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  • 101.
    Boyd, Meighan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Holmgren, Karin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Speleothems from Alepotrypa Cave: Towards climate reconstruction2018In: Alepotrypa Cave in the Mani, Greece: in honor of George Papathanassopoulos / [ed] Anastasia Papathanasiou, William A. Parkinson, Daniel J. Pullen, Michael L. Galaty, Panagiotis Karkanas, Oxbow Books, 2018Chapter in book (Other academic)
  • 102.
    Boyd, Meighan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Holmgren, Karin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Finné, Martin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hoffmann, Dirk
    Max Planck Institute for Evolutionary Anthropology, Germany.
    Jochum, Klaus Peter
    Max Planck Institute for Chemistry, Germany.
    Karkanas, Panagiotis
    American School of Classical Studies at Athens, Greece.
    Papathanasiou, Anastasia
    Greek Ministry of Culture, Greece.
    Stoll, Brigitte
    Max Planck Institute for Chemistry, Germany.
    Scholz, Denis
    Johannes Gutenberg-Universität Mainz, Germany.
    Spötl, Christoph
    University of Innsbruck, Austria.
    Stable isotopes and phosphorus patterns in calcite stalagmites from Alepotrypa Cave, Peloponnese, Greece as indicators of Holocene changes in rainfall and vegetationManuscript (preprint) (Other academic)
  • 103.
    Boyd, Meighan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Holmgren, Karin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Shaw, Paul
    University of the West Indies, Jamaica.
    Hoffmann, Dirk
    Max Planck Institute for Evolutionary Anthropology, Germany.
    Mangini, Augusto
    University of Heidelberg, Germany.
    Mudelsee, Manfred
    Alfred Wegener Institute for Polar and Marine Research, Germany.
    Spötl, Christoph
    University of Innsbruck, Austria.
    Early Holocene patterns of rainfall, vegetation and soil conditions, inferred from a southern Caribbean stalagmiteManuscript (preprint) (Other academic)
  • 104.
    Boyd, Meighan
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Karkanas, Panagiotis
    American School of Classical Studies at Athens, Greece.
    Papathanasiou, Anastasia
    Greek Ministry of Culture, Greece.
    Hoffmann, Dirk
    Max Planck Institute for Evolutionary Anthropology, Germany.
    Holmgren, Karin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    U-Th dating of calcite on human bones from Alepotrypa Cave, GreeceManuscript (preprint) (Other academic)
  • 105. Brangari, Albert C.
    et al.
    Fernandez-Garcia, Daniel
    Sanchez-Vila, Xavier
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Ecological and soil hydraulic implications of microbial responses to stress - A modeling analysis2018In: Advances in Water Resources, ISSN 0309-1708, E-ISSN 1872-9657, Vol. 116, p. 178-194Article in journal (Refereed)
    Abstract [en]

    A better understanding of microbial dynamics in porous media may lead to improvements in the design and management of a number of technological applications, ranging from the degradation of contaminants to the optimization of agricultural systems. To this aim, there is a recognized need for predicting the proliferation of soil microbial biomass (often organized in biofilms) under different environments and stresses. We present a general multi-compartment model to account for physiological responses that have been extensively reported in the literature. The model is used as an explorative tool to elucidate the ecological and soil hydraulic consequences of microbial responses, including the production of extracellular polymeric substances (EPS), the induction of cells into dormancy, and the allocation and reuse of resources between biofilm compartments. The mechanistic model is equipped with indicators allowing the microorganisms to monitor environmental and biological factors and react according to the current stress pressures. The feedbacks of biofilm accumulation on the soil water retention are also described. Model runs simulating different degrees of substrate and water shortage show that adaptive responses to the intensity and type of stress provide a clear benefit to microbial colonies. Results also demonstrate that the model may effectively predict qualitative patterns in microbial dynamics supported by empirical evidence, thereby improving our understanding of the effects of pore-scale physiological mechanisms on the soil macroscale phenomena.

  • 106. Braun, Andreas
    et al.
    Wagner, Julia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hochschild, Volker
    Above-ground biomass estimates based on active and passive microwave sensor imagery in low-biomass savanna ecosystems2018In: Journal of Applied Remote Sensing, ISSN 1931-3195, E-ISSN 1931-3195, Vol. 12, no 4, article id 046027Article in journal (Refereed)
    Abstract [en]

    Although many studies exist on the estimation and monitoring of above-ground biomass (AGB) of forest ecosystems by methods of remote sensing, very little research has been carried out for ecosystems of low primary production, such as grasslands, steppes, or savannas. Our study intends to approach this gap and investigates the correlation between space-borne radar information and AGB at the scale of 10 tons per hectare and below. Additionally, we introduce the integration of passive brightness temperature as an additional covariate for biomass estimation, based on the hypothesis that it contains information complementary to microwave backscatter of the active sensors. Our findings show that large-scale estimates of AGB can be conducted for grasslands and savannas at high accuracy (R-2 up to 0.52). Additionally, we found that the integration of passive radar can increase the quality of AGB estimates in terms of explained variance for selected cases. We hope that these indications are a starting point for more integrated approaches toward biomass estimations based on Earth observation methods.

  • 107.
    Bring, Arvid
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of New Hampshire, USA.
    Asokan, Shilpa M.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jaramillo, Fernando
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Levi, Lea
    Stockholm University, Faculty of Science, Department of Physical Geography. KTH Royal Institute of Technology, Sweden; University of Split, Croatia.
    Pietroń, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Prieto, Carmen
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Rogberg, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Implications of freshwater flux data from the CMIP5 multimodel output across a set of Northern Hemisphere drainage basins2015In: Earths Future, ISSN 2328-4277, Vol. 3, no 6, p. 206-217Article in journal (Refereed)
    Abstract [en]

    The multimodel ensemble of the Coupled Model Intercomparison Project, Phase 5 (CMIP5) synthesizes the latest research in global climate modeling. The freshwater system on land, particularly runoff, has so far been of relatively low priority in global climate models, despite the societal and ecosystem importance of freshwater changes, and the science and policy needs for such model output on drainage basin scales. Here we investigate the implications of CMIP5 multimodel ensemble output data for the freshwater system across a set of drainage basins in the Northern Hemisphere. Results of individual models vary widely, with even ensemble mean results differing greatly from observations and implying unrealistic long-term systematic changes in water storage and level within entire basins. The CMIP5 projections of basin-scale freshwater fluxes differ considerably more from observations and among models for the warm temperate study basins than for the Arctic and cold temperate study basins. In general, the results call for concerted research efforts and model developments for improving the understanding and modeling of the freshwater system and its change drivers. Specifically, more attention to basin-scale water flux analyses should be a priority for climate model development, and an important focus for relevant model-based advice for adaptation to climate change.

  • 108.
    Bring, Arvid
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of New Hampshire, USA.
    Fedorova, I.
    Dibike, Y.
    Hinzman, L.
    Mard, J.
    Mernild, S. H.
    Prowse, T.
    Semenova, O.
    Stuefer, S. L.
    Woo, M-K.
    Arctic terrestrial hydrology: A synthesis of processes, regional effects, and research challenges2016In: Journal of Geophysical Research - Biogeosciences, ISSN 2169-8953, E-ISSN 2169-8961, Vol. 121, no 3, p. 621-649Article, review/survey (Refereed)
    Abstract [en]

    Terrestrial hydrology is central to the Arctic system and its freshwater circulation. Water transport and water constituents vary, however, across a very diverse geography. In this paper, which is a component of the Arctic Freshwater Synthesis, we review the central freshwater processes in the terrestrial Arctic drainage and how they function and change across seven hydrophysiographical regions (Arctic tundra, boreal plains, shield, mountains, grasslands, glaciers/ice caps, and wetlands). We also highlight links between terrestrial hydrology and other components of the Arctic freshwater system. In terms of key processes, snow cover extent and duration is generally decreasing on a pan-Arctic scale, but snow depth is likely to increase in the Arctic tundra. Evapotranspiration will likely increase overall, but as it is coupled to shifts in landscape characteristics, regional changes are uncertain and may vary over time. Streamflow will generally increase with increasing precipitation, but high and low flows may decrease in some regions. Continued permafrost thaw will trigger hydrological change in multiple ways, particularly through increasing connectivity between groundwater and surface water and changing water storage in lakes and soils, which will influence exchange of moisture with the atmosphere. Other effects of hydrological change include increased risks to infrastructure and water resource planning, ecosystem shifts, and growing flows of water, nutrients, sediment, and carbon to the ocean. Coordinated efforts in monitoring, modeling, and processing studies at various scales are required to improve the understanding of change, in particular at the interfaces between hydrology, atmosphere, ecology, resources, and oceans.

  • 109.
    Bring, Arvid
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Goldenberg, Romain
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kalantari, Zahra
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Prieto, Carmen
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Ma, Yan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Contrasting Hydroclimatic Model-Data Agreements Over the Nordic-Arctic Region2019In: Earth's Future, ISSN 1384-5160, E-ISSN 2328-4277, Vol. 7, no 12, p. 1270-1282Article in journal (Refereed)
    Abstract [en]

    Rapid changes in high-latitude hydroclimate have important implications for human societies and environment. Previous studies of different regions have indicated better agreement between climate model results and observation data for the thermodynamic variable of surface air temperature (T) than for the water variables of precipitation (P), evapotranspiration (ET), and runoff (R). Here we compare climate model output with observations for 64 Nordic and Arctic hydrological basins of different sizes, and for the whole region combined. We find an unexpectedly high agreement between models and observations for R, about as high as the model-observation agreement for T and distinctly higher than that for P or ET. Model-observation agreement for R and T is also consistently higher on the whole-region scale than individual basin scales. In contrast, model-observation agreement for P and ET is overall lower, and for some error measures also lower for the whole region than for individual basins of various scales. Region-specific soil freeze-thaw bias of climate models can at least partly explain the low model-observation agreement for P and ET, while leaving modeled R relatively unaffected. Thereby, model projections for this region may be similarly reliable and directly useful for large-scale average conditions of R as of T.

  • 110.
    Bring, Arvid
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography. The Nature Conservancy, USA.
    Role-play simulations as an aid to achieve complex learning outcomes in hydrological science2019In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 23, no 5, p. 2369-2378Article in journal (Refereed)
    Abstract [en]

    Students in hydrology are expected to become proficient in a set of quantitative skills while also acquiring the ability to apply their problem-solving abilities in real-life situations. To achieve both these types of learning outcomes, there is broad evidence that activity-based learning is beneficial. In this paper, we argue that role-play simulations in particular are useful for achieving complex learning outcomes, i.e., making students able to coordinate and integrate various analytical skills in complicated settings. We evaluated the effects of an integrated water resources management (IWRM) negotiation simulation next to more traditional teaching methods intended to foster quantitative understanding. Results showed that despite similar student-reported achievement of both complex and quantitative intended learning outcomes, the students favored the negotiation simulation over the traditional method. This implies that role-play simulations can motivate and actively engage a classroom, thereby creating a space for potential deeper learning and longer retention of knowledge. While our findings support the utility of simulations to teach complex learning outcomes and indicate no shortcoming in achieving such outcomes next to traditional methods aimed at quantitative learning outcomes, simulations are still not widely used to foster activity-based learning in the classroom. We thus conclude by presenting three particularly challenging areas of role-play simulations as learning tools that serve as potential barriers to their implementation and suggest ways to overcome such roadblocks.

  • 111.
    Bring, Arvid
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of New Hampshire, USA.
    Shiklomanov, Alexander
    Lammers, Richard B.
    Pan-Arctic river discharge: Prioritizing monitoring of future climate change hot spots2017In: Earth's Future, ISSN 1384-5160, E-ISSN 2328-4277, Vol. 5, no 1, p. 72-92Article in journal (Refereed)
    Abstract [en]

    The Arctic freshwater cycle is changing rapidly, which will require adequate monitoring of river flows to detect, observe, and understand changes and provide adaptation information. There has, however, been little detail about where the greatest flow changes are projected, and where monitoring therefore may need to be strengthened. In this study, we used a set of recent climate model runs and an advanced macro-scale hydrological model to analyze how flows across the continental pan-Arctic are projected to change and where the climate models agree on significant changes. We also developed a method to identify where monitoring stations should be placed to observe these significant changes, and compared this set of suggested locations with the existing network of monitoring stations. Overall, our results reinforce earlier indications of large increases in flow over much of the Arctic, but we also identify some areas where projections agree on significant changes but disagree on the sign of change. For monitoring, central and eastern Siberia, Alaska, and central Canada are hot spots for the highest changes. To take advantage of existing networks, a number of stations across central Canada and western and central Siberia could form a prioritized set. Further development of model representation of high-latitude hydrology would improve confidence in the areas we identify here. Nevertheless, ongoing observation programs may consider these suggested locations in efforts to improve monitoring of the rapidly changing Arctic freshwater cycle.

  • 112.
    Brown, Ian
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Mwansasu, Simon L. A.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Dar es Salaam, Tanzania.
    Westerberg, Lars-Ove
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Multi-decadal L-band SAR observations of the Mangrove forests of the Rufiji DeltaManuscript (preprint) (Other academic)
    Abstract [en]

    Mangroves are important habitats that face a range of threats, natural and anthropogenic. Synthetic aperture radar (SAR) images from 1994 to 2010 have been used to identify systematic changes in mangrove forest vegetation in the Rufiji Delta, Tanzania. The mangrove forest is a Forest Reserve and is protected from large scale exploitation, though there are settlements within the reserve. A dataset of five L-band SAR images spanning a 16-year time period was processed to identify spatio-temporal changes in mangrove forest extent and composition. SAR signatures are related to changes in water budget. The image data show minor expansion in cultivated land along the margins of established communities in the delta. Thinning of mangroves is detected on higher ground whilst along creeks and river channels SAR backscatter indicates an increase in biomass. Sea level height is found to exert a stronger influence on backscatter than minor differences in seasonality. Despite inaccuracies in older SAR images SAR time series are shown to provide valuable data on the spatio-temporal dynamics of East African mangrove forests.

  • 113.
    Brown, Ian
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Mwansasu, Simon
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Dar es Salaam, Tanzania.
    Westerberg, Lars-Ove
    Stockholm University, Faculty of Science, Department of Physical Geography.
    L-Band Polarimetric Target Decomposition of Mangroves of the Rufiji Delta, Tanzania2016In: Remote Sensing, ISSN 2072-4292, E-ISSN 2072-4292, Vol. 8, no 2, article id UNSP 140Article in journal (Refereed)
    Abstract [en]

    The mangroves of the Rufiji Delta are an important habitat and resource. The mangrove forest reserve is home to an indigenous population and has been under pressure from an influx of migrants from the landward side of the delta. Timely and effective forest management is needed to preserve the delta and mangrove forest. Here, we investigate the potential of polarimetric target decomposition for mangrove forest monitoring and analysis. Using three ALOS PALSAR images, we show that L-band polarimetry is capable of mapping mangrove dynamics and is sensitive to stand structure and the hydro-geomorphology of stands. Entropy-alpha-anisotropy and incoherent target decompositions provided valuable measures of scattering behavior related to forest structure. Little difference was found between Yamaguchi and Arii decompositions, despite the conceptual differences between these models. Using these models, we were able to differentiate the scattering behavior of the four main species found in the delta, though classification was impractical due to the lack of pure stands. Scattering differences related to season were attributed primarily to differences in ground moisture or inundation. This is the first time mangrove species have been identified by their scattering behavior in L-band polarimetric data. These results suggest higher resolution L-band quad-polarized imagery, such as from PALSAR-2, may be a powerful tool for mangrove species mapping.

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  • 114. Brugnara, Y.
    et al.
    Auchmann, R.
    Brönnimann, S.
    Allan, R. J.
    Auer, I.
    Barriendos, M.
    Bergström, H.
    Bhend, J.
    Brázdil, R.
    Compo, G. P.
    Cornes, R. C.
    Dominguez-Castro, F.
    van Engelen, A. F. V.
    Filipiak, J.
    Holopainen, J.
    Jourdain, S.
    Kunz, M.
    Luterbacher, J.
    Maugeri, M.
    Mercalli, L.
    Moberg, Anders
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Mock, C. J.
    Pichard, G.
    Řezníčková, L.
    van der Schrier, G.
    Slonosky, V.
    Ustrnul, Z.
    Valente, M. A.
    Wypych, A.
    Yin, X.
    A collection of sub-daily pressure and temperature observations for the early instrumental period with a focus on the "year without a summer" 18162015In: Climate of the Past, ISSN 1814-9324, E-ISSN 1814-9332, Vol. 11, no 8, p. 1027-1047Article in journal (Refereed)
    Abstract [en]

    The eruption of Mount Tambora (Indonesia) in April 1815 is the largest documented volcanic eruption in history. It is associated with a large global cooling during the following year, felt particularly in parts of Europe and North America, where the year 1816 became known as the "year without a summer". This paper describes an effort made to collect surface meteorological observations from the early instrumental period, with a focus on the years of and immediately following the eruption (1815–1817). Although the collection aimed in particular at pressure observations, correspondent temperature observations were also recovered. Some of the series had already been described in the literature, but a large part of the data, recently digitised from original weather diaries and contemporary magazines and newspapers, is presented here for the first time. The collection puts together more than 50 sub-daily series from land observatories in Europe and North America and from ships in the tropics. The pressure observations have been corrected for temperature and gravity and reduced to mean sea level. Moreover, an additional statistical correction was applied to take into account common error sources in mercury barometers. To assess the reliability of the corrected data set, the variance in the pressure observations is compared with modern climatologies, and single observations are used for synoptic analyses of three case studies in Europe. All raw observations will be made available to the scientific community in the International Surface Pressure Databank.

  • 115. Brönnimann, Stefan
    et al.
    Allan, Rob
    Ashcroft, Linden
    Baer, Saba
    Barriendos, Mariano
    Brázdil, Rudolf
    Brugnara, Yuri
    Brunet, Manola
    Brunetti, Michele
    Chimani, Barbara
    Cornes, Richard
    Domínguez-Castro, Fernando
    Filipiak, Janusz
    Founda, Dimitra
    García Herrera, Ricardo
    Gergis, Joelle
    Grab, Stefan
    Hannak, Lisa
    Huhtamaa, Heli
    Jacobsen, Kim S.
    Jones, Phil
    Jourdain, Sylvie
    Kiss, Andrea
    Lin, Kuanhui Elaine
    Lorrey, Andrew
    Lundstad, Elin
    Luterbacher, Jürg
    Mauelshagen, Franz
    Maugeri, Maurizio
    Maughan, Nicolas
    Moberg, Anders
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Neukom, Raphael
    Nicholson, Sharon
    Noone, Simon
    Nordli, Øyvind
    Björg Ólafsdóttir, Kristín
    Pearce, Petra R.
    Pfister, Lucas
    Pribyl, Kathleen
    Przybylak, Rajmund
    Pudmenzky, Christa
    Rasol, Dubravka
    Reichenbach, Delia
    Řezníčková, Ladislava
    Rodrigo, Fernando S.
    Rohr, Christian
    Skrynyk, Oleg
    Slonosky, Victoria
    Thorne, Peter
    Valente, Maria Antónia
    Vaquero, José M.
    Westcottt, Nancy E.
    Williamson, Fiona
    Wyszyński, Przemyslaw
    Unlocking Pre-1850 Instrumental Meteorological Records: A Global Inventory2019In: Bulletin of The American Meteorological Society - (BAMS), ISSN 0003-0007, E-ISSN 1520-0477, Vol. 100, no 12, p. ES389-ES413Article in journal (Refereed)
    Abstract [en]

    Instrumental meteorological measurements from periods prior to the start of national weather services are designated early instrumental data. They have played an important role in climate research as they allow daily to decadal variability and changes of temperature, pressure, and precipitation, including extremes, to be addressed. Early instrumental data can also help place twenty-first century climatic changes into a historical context such as defining preindustrial climate and its variability. Until recently, the focus was on long, high-quality series, while the large number of shorter series (which together also cover long periods) received little to no attention. The shift in climate and climate impact research from mean climate characteristics toward weather variability and extremes, as well as the success of historical reanalyses that make use of short series, generates a need for locating and exploring further early instrumental measurements. However, information on early instrumental series has never been electronically compiled on a global scale. Here we attempt a worldwide compilation of metadata on early instrumental meteorological records prior to 1850 (1890 for Africa and the Arctic). Our global inventory comprises information on several thousand records, about half of which have not yet been digitized (not even as monthly means), and only approximately 20% of which have made it to global repositories. The inventory will help to prioritize data rescue efforts and can be used to analyze the potential feasibility of historical weather data products. The inventory will be maintained as a living document and is a first, critical, step toward the systematic rescue and reevaluation of these highly valuable early records. Additions to the inventory are welcome.

  • 116. Buendía, Corina
    et al.
    Kleidon, Axel
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Reu, Björn
    Porporato, Amilcare
    Evaluating the effect of nutrient redistribution by animals on the phosphorus cycle of lowland Amazonia2018In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 15, no 1, p. 279-295Article in journal (Refereed)
    Abstract [en]

    Phosphorus (P) availability decreases with soil age and potentially limits the productivity of ecosystems growing on old and weathered soils. Despite growing on ancient soils, ecosystems of lowland Amazonia are highly productive and are among the most biodiverse on Earth. P eroded and weathered in the Andes is transported by the rivers and deposited in floodplains of the lowland Amazon basin creating hotspots of P fertility. We hypothesize that animals feeding on vegetation and detritus in these hotspots may redistribute P to P-depleted areas, thus contributing to dissipate the P gradient across the landscape. Using a mathematical model, we show that animal-driven spatial redistribution of P from rivers to land and from seasonally flooded to terra firme (upland) ecosystems may sustain the P cycle of Amazonian lowlands. Our results show how P imported to land by terrestrial piscivores in combination with spatial redistribution of herbivores and detritivores can significantly enhance the P content in terra firme ecosystems, thereby highlighting the importance of food webs for the biogeochemical cycling of Amazonia.

  • 117.
    Börjeson, Lowe
    et al.
    Stockholm University, Faculty of Social Sciences, Department of Human Geography.
    Berg, Johan
    Stockholm University, Faculty of Social Sciences, Department of Human Geography.
    Cousins, Sara A. O.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jansson, Ulf
    Stockholm University, Faculty of Social Sciences, Department of Human Geography.
    Open Access to Rural Landscapes!2014In: Rural Landscapes: Society, Environment, History, ISSN 2002-0104, Vol. 1, no 1, p. 1-2Article in journal (Other academic)
    Abstract [en]

    The academic study of rural landscapes covers a broad range of academic disciplines and thematic, methodological and theoretical concerns and interests; including questions concerned with resource use (e.g. agriculture, forestry, water and mining), settlement, livelihoods, conflicts, conservation, culture and identity. This diversity is clearly a strength (the rich empirical and intellectual base), but also presents a challenge, as the dissemination of research findings is distributed through a plethora of publishing channels, which do not necessarily encourage exchange of results and ideas that are not already perceived as germane to already established academic networks.

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  • 118. Böttner, Christoph
    et al.
    Berndt, Christian
    Reinardy, Benedict T.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Geersen, Jacob
    Karstens, Jens
    Bull, Jonathan M.
    Callow, Ben J.
    Lichtschlag, Anna
    Schmidt, Mark
    Elger, Judith
    Schramm, Bettina
    Haeckel, Matthias
    Pockmarks in the Witch Ground Basin, Central North Sea2019In: Geochemistry Geophysics Geosystems, ISSN 1525-2027, E-ISSN 1525-2027, Vol. 20, no 4, p. 1698-1719Article in journal (Refereed)
    Abstract [en]

    Marine sediments host large amounts of methane (CH4), which is a potent greenhouse gas. Quantitative estimates for methane release from marine sediments are scarce, and a poorly constrained temporal variability leads to large uncertainties in methane emission scenarios. Here, we use 2-D and 3-D seismic reflection, multibeam bathymetric, geochemical, and sedimentological data to (I) map and describe pockmarks in the Witch Ground Basin (central North Sea), (II) characterize associated sedimentological and fluid migration structures, and (III) analyze the related methane release. More than 1,500 pockmarks of two distinct morphological classes spread over an area of 225 km(2). The two classes form independently from another and are corresponding to at least two different sources of fluids. Class 1 pockmarks are large in size (> 6 m deep, > 250 m long, and > 75 m wide), show active venting, and are located above vertical fluid conduits that hydraulically connect the seafloor with deep methane sources. Class 2 pockmarks, which comprise 99.5% of all pockmarks, are smaller (0.9-3.1 m deep, 26-140 m long, and 14-57 m wide) and are limited to the soft, fine-grained sediments of the Witch Ground Formation and possibly sourced by compaction-related dewatering. Buried pockmarks within the Witch Ground Formation document distinct phases of pockmark formation, likely triggered by external forces related to environmental changes after deglaciation. Thus, greenhouse gas emissions from pockmark fields cannot be based on pockmark numbers and present-day fluxes but require an analysis of the pockmark forming processes through geological time. Plain Language Summary Marine sediments host large amounts of methane (CH4), which is a potent greenhouse gas. The amount of methane released into the atmosphere is, however, largely unknown making it difficult to implement this methane source in climate models. Here we use geophysical, geochemical, and sedimentological data to map the distribution of fluid escape structures in the central North Sea. More than 1,500 pockmarks, which are circular to semicircular depressions of the seafloor, indicate fluid flow from the subsurface. There are two distinct morphological classes of pockmarks corresponding to at least two different fluid sources. Class 1 pockmarks are large, show active venting, and are located above vertical fluid conduits in the subsurface, which feed fluids from deeper strata. Class 2 pockmarks, which comprise 99.5% of all pockmarks, are smaller and limited to the soft sediments directly below the seafloor. Older pockmarks in the subsurface document distinct phases of pockmark formation, likely triggered by external forces after the retreat of ice in the North Sea. The amount of methane released from natural geological sources based on pockmark numbers may be wrong as these do not take into account the origin and composition of released fluids.

  • 119. Büntgen, Ulf
    et al.
    Eggertsson, Ólafur
    Wacker, Lukas
    Sigl, Michael
    Charpentier Ljungqvist, Fredrik
    Stockholm University, Faculty of Humanities, Department of History.
    Di Cosmo, Nicola
    Plunkett, Gill
    Krusic, Paul J.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Cambridge, UK.
    Newfield, Timothy P.
    Esper, Jan
    Lane, Christine
    Reinig, Frederick
    Oppenheimer, Clive
    Multi-proxy dating of Iceland's major pre-settlement Katla eruption to 822-823 CE2017In: Geology, ISSN 0091-7613, E-ISSN 1943-2682, Vol. 45, no 9, p. 783-786Article in journal (Refereed)
    Abstract [en]

    Investigations of the impacts of past volcanic eruptions on climate, environment, and society require accurate chronologies. However, eruptions that are not recorded in historical documents can seldom be dated exactly. Here we use annually resolved radiocarbon (C-14) measurements to isolate the 775 CE cosmogenic C-14 peak in a subfossil birch tree that was buried by a glacial outburst flood in southern Iceland. We employ this absolute time marker to date a subglacial eruption of Katla volcano at late 822 CE to early 823 CE. We argue for correlation between the 822-823 CE eruption and a conspicuous sulfur anomaly evident in Greenland ice cores, which follows in the wake of an even larger volcanic signal (ca. 818-820 CE) as yet not attributed to a known eruption. An abrupt summer cooling in 824 CE, evident in tree-ring reconstructions for Fennoscandia and the Northern Hemisphere, suggests a climatic response to the Katla eruption. Written historical sources from Europe and China corroborate our proposed tree ring-radiocarbon-ice core linkage but also point to combined effects of eruptions occurring during this period. Our study describes the oldest precisely dated, high-latitude eruption and reveals the impact of an extended phase of volcanic forcing in the early 9th century. It also provides insight into the existence of prehistoric woodland cover and the nature of volcanism several decades before Iceland's permanent settlement began.

  • 120. Büntgen, Ulf
    et al.
    Galván, Juan D.
    Mysterud, Atle
    Krusic, Paul J.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Cambridge, UK.
    Hülsmann, Lisa
    Jenny, Hannes
    Senn, Josef
    Bollmann, Kurt
    Horn growth variation and hunting selection of the Alpine ibex2018In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 87, no 4, p. 1069-1079Article in journal (Refereed)
    Abstract [en]

    1. Selective hunting can affect demographic characteristics and phenotypic traits of the targeted species. Hunting systems often involve harvesting quotas based on sex, age and/or size categories to avoid selective pressure. However, it is difficult to assess whether such regulations deter hunters from targeting larger trophy animals with longer horns that may have evolutionary consequences.

    2. Here, we compile 44,088 annually resolved and absolutely dated measurements of Alpine ibex (Capra ibex) horn growth increments from 8,355 males, harvested between 1978 and 2013, in the eastern Swiss Canton of Grisons. We aim to determine whether male ibex with longer horns were preferentially targeted, causing animals with early rapid horn growth to have shorter lives, and whether such hunting selection translated into long-term trends in horn size over the past four decades.

    3. Results show that medium-to longer-horned adult males had a higher probability of being harvested than shorter-horned individuals of the same age and that regulations do affect the hunters' behaviour. Nevertheless, phenotypic traits such as horn length, as well as body size and weight, remained stable over the study period.

    4. Although selective trophy hunting still occurs, it did not cause a measurable evolutionary response in Grisons' Alpine ibex populations; managed and surveyed since 1978. Nevertheless, further research is needed to understand whether phenotypic trait development is coinfluenced by other, potentially compensatory factors that may possibly mask the effects of selective, long-term hunting pressure.

  • 121. Büntgen, Ulf
    et al.
    Jäggi, Maya
    Egli, Simon
    Heule, Martin
    Peter, Martina
    Zagyva, Imre
    Krusic, Paul J.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Cambridge, UK.
    Zimermann, Stephan
    Bagi, Istvan
    No radioactive contamination from the Chernobyl disaster in Hungarian white truffles (Tuber magnatum)2019In: Environmental Pollution, ISSN 0269-7491, E-ISSN 1873-6424, Vol. 252, p. 1643-1647Article in journal (Refereed)
    Abstract [en]

    Despite being one of the most expensive gourmet foods, it remains unclear if the iconic White Truffle (Tuber magnatum Pico; hereinafter WT) accumulates radioactivity at harmful levels comparable to other fungal species. Here, we measure the active radiocaesium-137 concentration (Cs-137) in ten hypogeous WT fruitbodies from southern Hungary, and the soils in which they were growing. All WTs reveal nonsignificant Cs-137 values, thus providing an 'all clear' for WT hunters in the species' northernmost habitats, where corresponding soil samples occasionally exhibit slight Cs-137 concentrations. Our results are particularly relevant in the light of a rapidly increasing global demand for WTs and their subsequent trading extent and price inflation, because up to 600 kg of fresh fruitbodies are harvested each year in southern Hungary. Moreover, some of Europe's forest ecosystems, in which mushroom picking is common practise, are still contaminated with Cs-137 from the Chernobyl fallout more than 30 years ago, posing a serious threat to human health.

  • 122. Büntgen, Ulf
    et al.
    Krusic, Paul J.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Cambridge, UK.
    Piermattei, Alma
    Coomes, David A.
    Esper, Jan
    Myglan, Vladimir S.
    Kirdyanov, Alexander
    Julio Camarero, J.
    Crivellaro, Alan
    Körner, Christian
    Limited capacity of tree growth to mitigate the global greenhouse effect under predicted warming2019In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, article id 2171Article in journal (Refereed)
    Abstract [en]

    It is generally accepted that animal heartbeat and lifespan are often inversely correlated, however, the relationship between productivity and longevity has not yet been described for trees growing under industrial and pre-industrial climates. Using 1768 annually resolved and absolutely dated ring width measurement series from living and dead conifers that grew in undisturbed, high-elevation sites in the Spanish Pyrenees and the Russian Altai over the past 2000 years, we test the hypothesis of grow fast-die young. We find maximum tree ages are significantly correlated with slow juvenile growth rates. We conclude, the interdependence between higher stem productivity, faster tree turnover, and shorter carbon residence time, reduces the capacity of forest ecosystems to store carbon under a climate warming-induced stimulation of tree growth at policy-relevant timescales.

  • 123. Büntgen, Ulf
    et al.
    Krusic, Paul J.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Cambridge, United Kingdom.
    Verstege, Anne
    Sanguesa-Barreda, Gabriel
    Wagner, Sebastian
    Julio Camarero, J.
    Charpentier Ljungqvist, Fredrik
    Stockholm University, Faculty of Humanities, Department of History.
    Zorita, Eduardo
    Oppenheimer, Clive
    Konter, Oliver
    Tegel, Willy
    Gärtner, Holger
    Cherubini, Paolo
    Reinig, Frederick
    Esper, Jan
    New Tree-Ring Evidence from the Pyrenees Reveals Western Mediterranean Climate Variability since Medieval Times2017In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 30, no 14, p. 5295-5318Article in journal (Refereed)
    Abstract [en]

    Paleoclimatic evidence is necessary to place the current warming and drying of the western Mediterranean basin in a long-term perspective of natural climate variability. Annually resolved and absolutely dated temperature proxies south of the European Alps that extend back into medieval times are, however, mainly limited to measurements of maximum latewood density (MXD) from high-elevation conifers. Here, the authors present the world's best replicated MXD site chronology of 414 living and relict Pinus uncinata trees found >2200 m above mean sea level (MSL) in the Spanish central Pyrenees. This composite record correlates significantly (p <= 0.01) with May-June and August-September mean temperatures over most of the Iberian Peninsula and northern Africa (r = 0.72; 1950-2014). Spanning the period 1186-2014 of the Common Era (CE), the new reconstruction reveals overall warmer conditions around 1200 and 1400, and again after around 1850. The coldest reconstructed summer in 1258 (-4.4 degrees C compared to 1961-90) followed the largest known volcanic eruption of the CE. The twentieth century is characterized by pronounced summer cooling in the 1970s, subsequently rising temperatures until 2003, and a slowdown of warming afterward. Little agreement is found with climate model simulations that consistently overestimate recent summer warming and underestimate preindustrial temperature changes. Interannual-multidecadal covariability with regional hydroclimate includes summer pluvials after large volcanic eruptions. This study demonstrates the relevance of updating MXD-based temperature reconstructions, not only back in time but also toward the present, and emphasizes the importance of comparing temperature and hydroclimatic proxies, as well as model simulations for understanding regional climate dynamics.

  • 124. Büntgen, Ulf
    et al.
    Oliach, Daniel
    Martínez-Peña, Fernando
    Latorre, Joaquin
    Egli, Simon
    Krusic, Paul J.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Cambridge, United Kingdom.
    Black truffle winter production depends on Mediterranean summer precipitation2019In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 14, no 7, article id 074004Article in journal (Refereed)
    Abstract [en]

    The unprecedented price inflation of Black truffles, recently exceeding 5000 Euro kg(-1) (in Zurich), is a combined result of increasing global demands and decreasing Mediterranean harvests. Since the effects of long-term irrigation and climate variation on symbiotic fungus-host interaction and the development of belowground microbes are poorly understood, the establishment and maintenance of truffle plantations remains a risky venture. Using 49 years of continuous harvest and climate data from Spain, France and Italy, we demonstrate how truffle production rates, between November and March, significantly rely on previous June-August precipitation totals, whereas too much autumnal rainfall affects the subsequent winter harvest negatively. Despite a complex climate-host-fungus relationship, our findings show that southern European truffle yields can be predicted at highest probability (r = 0.78, t-stat = 5.645, prob = 0.000 01). Moreover, we demonstrate the reliability of national truffle inventories since 1970, and question the timing and dose of many of the currently operating irrigation systems. Finally, our results suggest that Black truffle mycorrhizal colonization of host fine roots, the sexualisation of mycelium, and the formation of peridium are strongly controlled by natural summer rainfall. Recognising the drought-vulnerability of southern Europe's rapidly growing truffle sector, we encourage a stronger liaison between farmers, politicians and scientists to maintain ecological and economic sustainability under predicted climate change in the Mediterranean basin.

  • 125. Büntgen, Ulf
    et al.
    Trnka, Miroslav
    Krusic, Paul J.
    Stockholm University, Faculty of Science, Department of Physical Geography. Navarino Environmental Observatory, Greece.
    Kyncl, Tomáš
    Kyncl, Josef
    Luterbacher, Jürg
    Zorita, Eduardo
    Charpentier Ljungqvist, Fredrik
    Stockholm University, Faculty of Humanities, Department of History.
    Auer, Ingeborg
    Konter, Oliver
    Schneider, Lea
    Tegel, Willy
    Štěpánek, Petr
    Brönnimann, Stefan
    Hellmann, Lena
    Nievergelt, Daniel
    Esper, Jan
    Tree-Ring Amplification of the Early Nineteenth-Century Summer Cooling in Central Europe2015In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 28, no 13, p. 5272-5288Article, review/survey (Refereed)
    Abstract [en]

    Annually resolved and absolutely dated tree-ring chronologies are the most important proxy archives to reconstruct climate variability over centuries to millennia. However, the suitability of tree-ring chronologies to reflect the “true” spectral properties of past changes in temperature and hydroclimate has recently been debated. At issue is the accurate quantification of temperature differences between early nineteenth-century cooling and recent warming. In this regard, central Europe (CEU) offers the unique opportunity to compare evidence from instrumental measurements, paleomodel simulations, and proxy reconstructions covering both the exceptionally hot summer of 2003 and the year without summer in 1816. This study uses 565 Swiss stone pine (Pinus cembra) ring width samples from high-elevation sites in the Slovakian Tatra Mountains and Austrian Alps to reconstruct CEU summer temperatures over the past three centuries. This new temperature history is compared to different sets of instrumental measurements and state-of-the-art climate model simulations. All records independently reveal the coolest conditions in the 1810s and warmest after 1996, but the ring width–based reconstruction overestimates the intensity and duration of the early nineteenth-century summer cooling by approximately 1.5°C at decadal scales. This proxy-specific deviation is most likely triggered by inflated biological memory in response to reduced warm season temperature, together with changes in radiation and precipitation following the Tambora eruption in April 1815. While suggesting there exists a specific limitation in ring width chronologies to capture abrupt climate perturbations with increased climate system inertia, the results underline the importance of alternative dendrochronological and wood anatomical parameters, including stable isotopes and maximum density, to assess the frequency and severity of climatic extremes.

  • 126. Büntgen, Ulf
    et al.
    Wacker, Lukas
    Galvan, J. Diego
    Arnold, Stephanie
    Arseneault, Dominique
    Baillie, Michael
    Beer, Jurg
    Bernabei, Mauro
    Bleicher, Niels
    Boswijk, Gretel
    Brauning, Achim
    Carrer, Marco
    Charpentier Ljungqvist, Fredrik
    Stockholm University, Faculty of Humanities, Department of History. University of Cambridge, UK.
    Cherubini, Paolo
    Christl, Marcus
    Christie, Duncan A.
    Clark, Peter W.
    Cook, Edward R.
    D'Arrigo, Rosanne
    Davi, Nicole
    Eggertsson, Olafur
    Esper, Jan
    Fowler, Anthony M.
    Gedalof, Ze'ev
    Gennaretti, Fabio
    Griessinger, Jussi
    Grissino-Mayer, Henri
    Grudd, Hakan
    Gunnarson, Björn E.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hantemirov, Rashit
    Herzig, Franz
    Hessl, Amy
    Heussner, Karl-Uwe
    Jull, A. J. Timothy
    Kukarskih, Vladimir
    Kirdyanov, Alexander
    Kolar, Tomas
    Krusic, Paul J.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Cambridge, UK; Navarino Environmental Observatory, Greece.
    Kyncl, Tomas
    Lara, Antonio
    LeQuesne, Carlos
    Linderholm, Hans W.
    Loader, Neil J.
    Luckman, Brian
    Miyake, Fusa
    Myglan, Vladimir S.
    Nicolussi, Kurt
    Oppenheimer, Clive
    Palmer, Jonathan
    Panyushkina, Irina
    Pederson, Neil
    Rybnicek, Michal
    Schweingruber, Fritz H.
    Seim, Andrea
    Sigl, Michael
    Churakova (Sidorova), Olga
    Speer, James H.
    Synal, Hans-Arno
    Tegel, Willy
    Treydte, Kerstin
    Villalba, Ricardo
    Wiles, Greg
    Wilson, Rob
    Winship, Lawrence J.
    Wunder, Jan
    Yang, Bao
    Young, Giles H. F.
    Tree rings reveal globally coherent signature of cosmogenic radiocarbon events in 774 and 993 CE2018In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 9, article id 3605Article in journal (Refereed)
    Abstract [en]

    Though tree-ring chronologies are annually resolved, their dating has never been independently validated at the global scale. Moreover, it is unknown if atmospheric radiocarbon enrichment events of cosmogenic origin leave spatiotemporally consistent fingerprints. Here we measure the C-14 content in 484 individual tree rings formed in the periods 770-780 and 990-1000 CE. Distinct C-14 excursions starting in the boreal summer of 774 and the boreal spring of 993 ensure the precise dating of 44 tree-ring records from five continents. We also identify a meridional decline of 11-year mean atmospheric radiocarbon concentrations across both hemispheres. Corroborated by historical eye-witness accounts of red auroras, our results suggest a global exposure to strong solar proton radiation. To improve understanding of the return frequency and intensity of past cosmic events, which is particularly important for assessing the potential threat of space weather on our society, further annually resolved C-14 measurements are needed.

  • 127. Campbell, Bruce M.
    et al.
    Beare, Douglas J.
    Bennett, Elena M.
    Hall-Spencer, Jason M.
    Ingram, John S. I.
    Jaramillo, Fernando
    Stockholm University, Faculty of Science, Stockholm Resilience Centre. Stockholm University, Faculty of Science, Department of Physical Geography.
    Ortiz, Rodomiro
    Ramankutty, Navin
    Sayer, Jeffrey A.
    Shindell, Drew
    Agriculture production as a major driver of the Earth system exceeding planetary boundaries2017In: Ecology & society, ISSN 1708-3087, E-ISSN 1708-3087, Vol. 22, no 4, article id 8Article in journal (Refereed)
    Abstract [en]

    We explore the role of agriculture in destabilizing the Earth system at the planetary scale, through examining nine planetary boundaries, or safe limits: land-system change, freshwater use, biogeochemical flows, biosphere integrity, climate change, ocean acidification, stratospheric ozone depletion, atmospheric aerosol loading, and introduction of novel entities. Two planetary boundaries have been fully transgressed, i.e., are at high risk, biosphere integrity and biogeochemical flows, and agriculture has been the major driver of the transgression. Three are in a zone of uncertainty i.e., at increasing risk, with agriculture the major driver of two of those, land-system change and freshwater use, and a significant contributor to the third, climate change. Agriculture is also a significant or major contributor to change for many of those planetary boundaries still in the safe zone. To reduce the role of agriculture in transgressing planetary boundaries, many interventions will be needed, including those in broader food systems.

  • 128.
    Cantoni, Jacopo
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kalantari, Zahra
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Watershed-Based Evaluation of Automatic Sensor Data: Water Quality and Hydroclimatic Relationships2020In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 12, no 1, article id 396Article in journal (Refereed)
    Abstract [en]

    Water is a fundamental resource and, as such, the object of multiple environmental policies requiring systematic monitoring of its quality as a main management component. Automatic sensors, allowing for continuous monitoring of various water quality variables at high temporal resolution, offer new opportunities for enhancement of essential water quality data. This study investigates the potential of sensor-measured data to improve understanding and management of water quality at watershed level. Self-organizing data maps, non-linear canonical correlation analysis, and linear regressions are used to assess the relationships between multiple water quality and hydroclimatic variables for the case study of Lake Malaren in Sweden, and its total catchment and various watersheds. The results indicate water discharge from dominant watersheds into a lake, and lake water temperature as possible proxies for some key water quality variables in the lake, such as blue-green algae; the latter is, in turn, identified as a potential good proxy for lake concentration of total nitrogen. The relationships between water discharges into the lake and lake water quality dynamics identify the dominant contributing watersheds for different water quality variables. Seasonality also plays an important role in determining some possible proxy relationships and their usefulness for different parts of the year.

  • 129. Capek, P. T.
    et al.
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kastovska, E.
    Wild, B.
    Diakova, K.
    Barta, J.
    Schnecker, J.
    Blasi, C.
    Martikainen, P. J.
    Alves, R. J. E.
    Guggenberger, G.
    Gentsch, N.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Mikutta, R.
    Shibistova, O.
    Urich, T.
    Schleper, C.
    Richter, A.
    Santruckova, H.
    A plant-microbe interaction framework explaining nutrient effects on primary production2018In: Nature Ecology & Evolution, E-ISSN 2397-334X, Vol. 2, no 10, p. 1588-1596Article in journal (Refereed)
    Abstract [en]

    In most terrestrial ecosystems, plant growth is limited by nitrogen and phosphorus. Adding either nutrient to soil usually affects primary production, but their effects can be positive or negative. Here we provide a general stoichiometric framework for interpreting these contrasting effects. First, we identify nitrogen and phosphorus limitations on plants and soil microorganisms using their respective nitrogen to phosphorus critical ratios. Second, we use these ratios to show how soil microorganisms mediate the response of primary production to limiting and non-limiting nutrient addition along a wide gradient of soil nutrient availability. Using a meta-analysis of 51 factorial nitrogen-phosphorus fertilization experiments conducted across multiple ecosystems, we demonstrate that the response of primary production to nitrogen and phosphorus additions is accurately predicted by our stoichiometric framework. The only pattern that could not be predicted by our original framework suggests that nitrogen has not only a structural function in growing organisms, but also a key role in promoting plant and microbial nutrient acquisition. We conclude that this stoichiometric framework offers the most parsimonious way to interpret contrasting and, until now, unresolved responses of primary production to nutrient addition in terrestrial ecosystems.

  • 130. Capek, Petr
    et al.
    Diakova, Katerina
    Dickopp, Jan-Erik
    Barta, Jiri
    Wild, Birgit
    Schnecker, Jörg
    Alves, Ricardo Jorge Eloy
    Aiglsdorfer, Stefanie
    Guggenberger, Georg
    Gentsch, Norman
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lashchinsky, Nikolaj
    Gittel, Antje
    Schleper, Christa
    Mikutta, Robert
    Palmtag, Juri
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Shibistova, Olga
    Urich, Tim
    Richter, Andreas
    Santruckova, Hana
    The effect of warming on the vulnerability of subducted organic carbon in arctic soils2015In: Soil Biology and Biochemistry, ISSN 0038-0717, E-ISSN 1879-3428, Vol. 90, p. 19-29Article in journal (Refereed)
    Abstract [en]

    Arctic permafrost soils contain large stocks of organic carbon (OC). Extensive cryogenic processes in these soils cause subduction of a significant part of OC-rich topsoil down into mineral soil through the process of cryoturbation. Currently, one-fourth of total permafrost OC is stored in subducted organic horizons. Predicted climate change is believed to reduce the amount of OC in permafrost soils as rising temperatures will increase decomposition of OC by soil microorganisms. To estimate the sensitivity of OC decomposition to soil temperature and oxygen levels we performed a 4-month incubation experiment in which we manipulated temperature (4-20 degrees C) and oxygen level of topsoil organic, subducted organic and mineral soil horizons. Carbon loss (C-LOSS) was monitored and its potential biotic and abiotic drivers, including concentrations of available nutrients, microbial activity, biomass and stoichiometry, and extracellular oxidative and hydrolytic enzyme pools, were measured. We found that independently of the incubation temperature, C-LOSS from subducted organic and mineral soil horizons was one to two orders of magnitude lower than in the organic topsoil horizon, both under aerobic and anaerobic conditions. This corresponds to the microbial biomass being lower by one to two orders of magnitude. We argue that enzymatic degradation of autochthonous subducted OC does not provide sufficient amounts of carbon and nutrients to sustain greater microbial biomass. The resident microbial biomass relies on allochthonous fluxes of nutrients, enzymes and carbon from the OC-rich topsoil. This results in a negative priming effect, which protects autochthonous subducted OC from decomposition at present. The vulnerability of subducted organic carbon in cryoturbated arctic soils under future climate conditions will largely depend on the amount of allochthonous carbon and nutrient fluxes from the topsoil.

  • 131. Capek, Petr
    et al.
    Kotas, Petr
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Santruckova, Hana
    Drivers of phosphorus limitation across soil microbial communities2016In: Functional Ecology, ISSN 0269-8463, E-ISSN 1365-2435, Vol. 30, no 10, p. 1705-1713Article in journal (Refereed)
    Abstract [en]

    Nutrient limitation of soil microbial communities controls the rates of plant litter and soil organic matter decomposition and nutrient mineralization, and as such, it is central to soil and ecosystem models. According to ecological stoichiometry theory, when the carbon (C)-to-nutrient (E) ratio of resources used by a microbial community is higher than a critical ratio (C:E-CR), that nutrient is limiting. The C-to-phosphorus (P) critical ratio (C:P-CR) that determines P limitation is largely unknown for soils, and thus, it is the subject of our study. Our results show that the C:P-CR in widely different soils ranges from 26<bold></bold>6 to 465<bold></bold>1 or from 20<bold></bold>9 to 740<bold></bold>7 when accounting for 95% confidence intervals. Using constant or narrowly fluctuating C:P-CR in ecosystem models is therefore inaccurate. The C:P-CR cannot be simply predicted from microbial community C:P or available soil P. C:P-CR was only related to relative abundance of phospholipid fatty acids, which reflects microbial community structure and physiology. Our data suggest complex controls over microbial community C:P-CR. We further propose that using P storage compounds that allow the microbial community to temporarily buffer variability in available P can represent a widely adopted strategies across soils.

  • 132.
    Carbonari, Daniel Escobar
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. International Center for Tropical Agriculture (CIAT), Vietnam; Ecotonos Foundation, Cali, Colombia.
    Grosjean, Godefroy
    Laderach, Peter
    Tran, Dai
    Sander, Bjoern Ole
    McKinley, Justin
    Sebastian, Leocadio
    Tapasco, Jeimar
    Reviewing Vietnam's Nationally Determined Contribution: A New Perspective Using the Marginal Cost of Abatement2019In: Frontiers in Sustainable Food Systems, E-ISSN 2571-581X, Vol. 3, article id UNSP 14Article, review/survey (Refereed)
    Abstract [en]

    The processes countries use to revise their Nationally Determined Contributions (NDCs) under the UNFCCC's Paris Agreement will be key to ensure that their pledges lead to effective climate change policy. In many developing countries, the agriculture, forestry and other land use (AFOLU) sector is central to their NDCs. For this study, a marginal abatement cost (MAC) curve was used to review Vietnam's mitigation pledges pertaining to the AFOLU sector. We conclude that Vietnam has the potential to increase its NDC pledges, especially in the land use sector and through negative cost mitigation measures including water techniques for rice cultivation, agroforestry, and management of livestock diets and manure. While the MAC curve alone is insufficient to prioritize policy options, this study highlights the fundamental importance of continuous data improvement and refinement for monitoring NDC actions and ultimately achieving the goals set out in the Paris Agreement.

  • 133. Caretta, Martina Angela
    et al.
    Westerberg, Lars-Ove
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Mburu, David Mwehia
    Fischer, Manuel
    Börjeson, Lowe
    Stockholm University, Faculty of Social Sciences, Department of Human Geography.
    Soil management and soil properties in a Kenyan smallholder irrigation system on naturally low-fertile soils2018In: Applied Geography, ISSN 0143-6228, E-ISSN 1873-7730, Vol. 90, p. 248-256Article in journal (Refereed)
    Abstract [en]

    In this study we examine the impact of soil management practices on soil properties in a landscape with naturally relatively poor soils on and below the dry slopes of a Rift Valley escarpment in Kenya that have been dominated by extensive smallholder investments in canal irrigation over the last 300 years. We show that farmers in the area have been able to keep up agricultural production in the face of growing population. The actual practices of soil management at one moment in time appear to be of minor importance to soil improvement, as indicated by the low correlation between Soil Management Index (SMI) and soil chemical data. However, cultivation triggers a process of slow soil improvement manifested by a positive correlation between nutrient levels and duration of irrigated cultivation and soil management, which likely explains farmers' confidence in soil productivity. However, we also identify sodicity as a risk connected to intensified irrigation in the area. Finally, we stress the need for further studies integrating investigations of local irrigation and soil management with soil and water quality analyses. These will be crucial to shape sustainable place-based and farmer-led solutions for African agricultural growth.

  • 134. Cerrato, Riccardo
    et al.
    Salvatore, Maria Cristina
    Gunnarson, Björn E.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Linderholm, Hans W.
    Carturan, Luca
    Brunetti, Michele
    De Blasi, Fabrizio
    Baroni, Carlo
    A Pinus cembra L. tree-ring record for late spring to late summer temperature in the Rhaetian Alps, Italy2019In: Dendrochronologia, ISSN 1125-7865, E-ISSN 1612-0051, Vol. 53, p. 22-31Article in journal (Refereed)
    Abstract [en]

    Ongoing climate change strongly affects high-elevation environments in the European Alps, influencing the cryosphere and the biosphere and causing widespread retreat of glaciers and changes in biomes. Nevertheless, high-elevation areas often lack long meteorological series, and global datasets cannot represent local variations well. Thus, proxy data, such as tree rings, provide information on past climatic variations from these remote sites. Although maximum latewood density (MXD) chronologies provide better temperature information than those based on tree-ring width (TRW), MXD series from the European Alps are lacking. To derive high-quality temperature information for the Rhaetian Alps, Pinus cembra L. trees sampled at approximately 2000 m a.s.l. were used to build one MXD chronology spanning from 1647 to 2015. The MXD data were significantly and highly correlated with seasonal May-September mean temperatures. The MXD chronology showed a generally positive trend since the middle of the 19th century, interrupted by short phases of climatic deterioration in the beginning of the 20th century and in the 1970s, conforming with the temperature trends. Our results underline the potential for using Pinus cembra L. MXD to reconstruct mean temperature variations, especially during the onset and latter part of the growing season, providing additional information on parts of the growing season not inferred from TRW. Future studies on MXD for this species will increase the availability of temporal and spatial data, allowing detailed climate reconstructions.

  • 135. Chadburn, S. E.
    et al.
    Burke, E. J.
    Cox, P. M.
    Friedlingstein, P.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Westermann, S.
    An observation-based constraint on permafrost loss as a function of global warming2017In: Nature Climate Change, ISSN 1758-678X, E-ISSN 1758-6798, Vol. 7, no 5, p. 340-344Article in journal (Refereed)
    Abstract [en]

    Permafrost, which covers 15 million km(2) of the land surface, is one of the components of the Earth system that is most sensitive to warming(1,2). Loss of permafrost would radically change high-latitude hydrology and biogeochemical cycling, and could therefore provide very significant feedbacks on climate change(3-8). The latest climate models all predict warming of high-latitude soils and thus thawing of permafrost under future climate change, but with widely varying magnitudes of permafrost thaw(9,10). Here we show that in each of the models, their present-day spatial distribution of permafrost and air temperature can be used to infer the sensitivity of permafrost to future global warming. Using the same approach for the observed permafrost distribution and air temperature, we estimate a sensitivity of permafrost area loss to global mean warming at stabilization of 4.0(-1.1)(+1.0) million km(2) degrees C-1 (1 sigma confidence), which is around 20% higher than previous studies(9). Our method facilitates an assessment for COP21 climate change targets(11): if the climate is stabilized at 2 degrees C above pre-industrial levels, we estimate that the permafrost area would eventually be reduced by over 40%. Stabilizing at 1.5 degrees C rather than 2 degrees C would save approximately 2 million km(2) of permafrost.

  • 136. Chadburn, Sarah E.
    et al.
    Krinner, Gerhard
    Porada, Philipp
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Bartsch, Annett
    Beer, Christian
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Belelli Marchesini, Luca
    Boike, Julia
    Ekici, Altug
    Elberling, Bo
    Friborg, Thomas
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Johansson, Margareta
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kutzbach, Lars
    Langer, Moritz
    Lund, Magnus
    Parmentier, Frans-Jan W.
    Peng, Shushi
    Van Huissteden, Ko
    Wang, Tao
    Westermann, Sebastian
    Zhu, Dan
    Burke, Eleanor J.
    Carbon stocks and fluxes in the high latitudes: using site-level data to evaluate Earth system models2017In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 14, no 22, p. 5143-5169Article in journal (Refereed)
    Abstract [en]

    It is important that climate models can accurately simulate the terrestrial carbon cycle in the Arctic due to the large and potentially labile carbon stocks found in permafrost-affected environments, which can lead to a positive climate feedback, along with the possibility of future carbon sinks from northward expansion of vegetation under climate warming. Here we evaluate the simulation of tundra carbon stocks and fluxes in three land surface schemes that each form part of major Earth system models (JSBACH, Germany; JULES, UK; ORCHIDEE, France). We use a site-level approach in which comprehensive, high-frequency datasets allow us to disentangle the importance of different processes. The models have improved physical permafrost processes and there is a reasonable correspondence between the simulated and measured physical variables, including soil temperature, soil moisture and snow. We show that if the models simulate the correct leaf area index (LAI), the standard C3 photosynthesis schemes produce the correct order of magnitude of carbon fluxes. Therefore, simulating the correct LAI is one of the first priorities. LAI depends quite strongly on climatic variables alone, as we see by the fact that the dynamic vegetation model can simulate most of the differences in LAI between sites, based almost entirely on climate inputs. However, we also identify an influence from nutrient limitation as the LAI becomes too large at some of the more nutrient-limited sites. We conclude that including moss as well as vascular plants is of primary importance to the carbon budget, as moss contributes a large fraction to the seasonal CO2 flux in nutrient-limited conditions. Moss photosynthetic activity can be strongly influenced by the moisture content of moss, and the carbon uptake can be significantly different from vascular plants with a similar LAI. The soil carbon stocks depend strongly on the rate of input of carbon from the vegetation to the soil, and our analysis suggests that an improved simulation of photosynthesis would also lead to an improved simulation of soil carbon stocks. However, the stocks are also influenced by soil carbon burial (e.g. through cryoturbation) and the rate of heterotrophic respiration, which depends on the soil physical state. More detailed below-ground measurements are needed to fully evaluate biological and physical soil processes. Furthermore, even if these processes are well modelled, the soil carbon profiles cannot resemble peat layers as peat accumulation processes are not represented in the models. Thus, we identify three priority areas for model development: (1) dynamic vegetation including (a) climate and (b) nutrient limitation effects; (2) adding moss as a plant functional type; and an (3) improved vertical profile of soil carbon including peat processes.

  • 137.
    Chakrawal, Arjun
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Herrmann, Anke M.
    Koestel, John
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Nunan, Naoise
    Kätterer, Thomas
    Manzoni, Stefano
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Dynamic upscaling of decomposition kinetics for carbon cycling models2020In: Geoscientific Model Development, ISSN 1991-959X, E-ISSN 1991-9603, Vol. 13, no 3, p. 1399-1429Article in journal (Refereed)
    Abstract [en]

    The distribution of organic substrates and microorganisms in soils is spatially heterogeneous at the microscale. Most soil carbon cycling models do not account for this microscale heterogeneity, which may affect predictions of carbon (C) fluxes and stocks. In this study, we hypothesize that the mean respiration rate (R) over bar at the soil core scale (i) is affected by the microscale spatial heterogeneity of substrate and microorganisms and (ii) depends upon the degree of this heterogeneity. To theoretically assess the effect of spatial heterogeneities on (R) over bar, we contrast heterogeneous conditions with isolated patches of substrate and microorganisms versus spatially homogeneous conditions equivalent to those assumed in most soil C models. Moreover, we distinguish between biophysical heterogeneity, defined as the nonuniform spatial distribution of substrate and microorganisms, and full heterogeneity, defined as the nonuniform spatial distribution of substrate quality (or accessibility) in addition to biophysical heterogeneity. Four common formulations for decomposition kinetics (linear, multiplicative, Michaelis-Menten, and inverse Michaelis-Menten) are considered in a coupled substrate-microbial biomass model valid at the microscale. We start with a 2-D domain characterized by a heterogeneous substrate distribution and numerically simulate organic matter dynamics in each cell in the domain. To interpret the mean behavior of this spatially explicit system, we propose an analytical scale transition approach in which microscale heterogeneities affect (R) over bar through the second-order spatial moments (spatial variances and covariances). The model assuming homogeneous conditions was not able to capture the mean behavior of the heterogeneous system because the second-order moments cause (R) over bar to be higher or lower than in the homogeneous system, depending on the sign of these moments. This effect of spatial heterogeneities appears in the upscaled nonlinear decomposition formulations, whereas the upscaled linear decomposition model deviates from homogeneous conditions only when substrate quality is heterogeneous. Thus, this study highlights the inadequacy of applying at the macroscale the same decomposition formulations valid at the microscale and proposes a scale transition approach as a way forward to capture microscale dynamics in core-scale models.

  • 138. Chalov, Sergey R.
    et al.
    Tsyplenkov, Anatolii S.
    Pietron, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Chalova, Aleksandra S.
    Shkolnyi, Danila I.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Maerker, Michael
    Sediment transport in headwaters of a volcanic catchment-Kamchatka Peninsula case study2017In: Frontiers of Earth Science, ISSN 2095-0195, Vol. 11, no 3, p. 565-578Article in journal (Refereed)
    Abstract [en]

    Due to specific environmental conditions, headwater catchments located on volcanic slopes and valleys are characterized by distinctive hydrology and sediment transport patterns. However, lack of sufficient monitoring causes that the governing processes and patterns in these areas are rarely well understood. In this study, spatiotemporal water discharge and sediment transport from upstream sources was investigated in one of the numerous headwater catchments located in the lahar valleys of the Kamchatka Peninsula Sukhaya Elizovskaya River near Avachinskii and Koryakskii volcanoes. Three different subcatchments and corresponding channel types (wandering rivers within lahar valleys, mountain rivers within volcanic slopes and rivers within submountain terrains) were identified in the studied area. Our measurements from different periods of observations between years 2012-2014 showed that the studied catchment was characterized by extreme diurnal fluctuation of water discharges and sediment loads that were influenced by snowmelt patterns and high infiltration rates of the easily erodible lahar deposits. The highest recorded sediment loads were up to 9.10(4) mg/L which was related to an increase of two orders of magnitude within a one day of observations. Additionally, to get a quantitative estimate of the spatial distribution of the eroded material in the volcanic substrates we applied an empirical soil erosion and sediment yield model-modified universal soil loss equation (MUSLE). The modeling results showed that even if the applications of the universal erosion model to different non-agricultural areas (e.g., volcanic catchments) can lead to irrelevant results, the MUSLE model delivered might be acceptable for non-lahar areas of the studied volcanic catchment. Overall the results of our study increase our understanding of the hydrology and associated sediment transport for prediction of risk management within headwater volcanic catchments.

  • 139. Chalov, Sergey
    et al.
    Thorslund, Josefin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kasimov, Nikolay
    Aybullatov, Denis
    Ilyicheva, Elena
    Karthe, Daniel
    Kositsky, Alexey
    Lychagin, Mikhail
    Nittrouer, Jeff
    Pavlov, Maxim
    Pietron, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Shinkareva, Galina
    Tarasov, Mikhail
    Garmaev, Endon
    Akhtman, Yosef
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    The Selenga River delta: a geochemical barrier protecting Lake Baikal waters2017In: Regional Environmental Change, ISSN 1436-3798, E-ISSN 1436-378X, Vol. 17, no 7, p. 2039-2053Article in journal (Refereed)
    Abstract [en]

    The protection of Lake Baikal and the planning of water management measures in the Selenga River Basin require a comprehensive understanding of the current state and functioning of the delta’s ecosystem and hydrogeochemical processes. This is particularly relevant in light of recent and expected future changes involving both the hydrology and water quality in the Lake Baikal basin causing spatiotemporal changes in water flow, morphology, and transport of sediments and metals in the Selenga River delta and thus impacting on delta barrier functions. The central part of the delta had been characterized by sediment storage, especially along the main channels, causing a continuous lift of the delta surface by about 0.75 cm/year−1. Theses morphological changes have a significant impact on hydrological conditions, with historical shifts in the bulk discharge from the left to the right parts of the delta which is distinguished by a relatively high density of wetlands. Regions with a high density of wetlands and small channels, in contrast to main channel regions, show a consistent pattern of considerable contaminant filtering and removal (between 77 and 99 % for key metals), during both high-flow and low-flow conditions. The removal is associated with a significant concentration increase (2–3 times) of these substances in the bottom sediment. In consequence, geomorphological processes, which govern the partitioning of flow between different channel systems, may therefore directly govern the barrier function of the delta.

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  • 140.
    Chandler, Benjamin M. P.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Portsmouth, UK.
    Chandler, Samuel J. P.
    Evans, David J. A.
    Ewertowski, Marek W.
    Lovell, Harold
    Roberts, David H.
    Schaefer, Martin
    Tomczyk, Aleksandra M.
    Sub‐annual moraine formation at an active temperate Icelandic glacier2020In: Earth Surface Processes and Landforms, ISSN 0197-9337, E-ISSN 1096-9837Article in journal (Refereed)
    Abstract [en]

    This paper presents detailed geomorphological and sedimentological investigations of small recessional moraines at Fjallsjökull, an active temperate outlet of Öræfajökull, southeast Iceland. The moraines are characterised by striking sawtooth or hairpin planforms, which are locally superimposed, giving rise to a complex spatial pattern. We recognise two distinct populations of moraines, namely a group of relatively prominent moraine ridges (mean height ~1.2 m) and a group of comparatively low‐relief moraines (mean height ~0.4 m). These two groups often occur in sets/systems, comprising one pronounced outer ridge and several inset smaller moraines. Using a representative subsample of the moraines, we establish that they form by either (i) submarginal deformation and squeezing of subglacial till or (ii) pushing of extruded tills. Locally, proglacial (glaciofluvial) sediments are also incorporated within the moraines during pushing. For the first time, to our knowledge, we demonstrate categorically that these moraines formed sub‐annually using repeat uncrewed aerial vehicle (UAV) imagery. We present a conceptual model for sub‐annual moraine formation at Fjallsjökull that proposes the sawtooth moraine sequence comprises (i) sets of small squeeze moraines formed during melt‐driven squeeze events and (ii) larger push moraines formed during winter re‐advances. We suggest the development of this process‐form regime is linked to a combination of elevated temperatures, high surface meltwater fluxes to the bed, and emerging basal topography (a depositional overdeepening). These factors result in highly saturated subglacial sediments and high porewater pressures, which induces submarginal deformation and ice‐marginal squeezing during the melt season. Strong glacier recession during the summer, driven by elevated temperatures, allows several squeeze moraines to be emplaced. This process‐form regime may be characteristic of active temperate glaciers receding into overdeepenings during phases of elevated temperatures, especially where their englacial drainage systems allow efficient transfer of surface meltwater to the glacier bed near the snout margin.

  • 141. Chandler, Benjamin M. P.
    et al.
    Lovell, Harold
    Boston, Clare M.
    Lukas, Sven
    Barr, Iestyn D.
    Örn Benediktsson, Ívar
    Benn, Douglas I.
    Clark, Chris D.
    Darvill, Christopher M.
    Evans, David J. A.
    Ewertowski, Marek W.
    Loibl, David
    Margold, Martin
    Otto, Jan-Christoph
    Roberts, David H.
    Stokes, Chris R.
    Storrar, Robert D.
    Stroeven, Arjen P.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Glacial geomorphological mapping: A review of approaches and frameworks for best practice2018In: Earth-Science Reviews, ISSN 0012-8252, E-ISSN 1872-6828, Vol. 185, p. 806-846Article, review/survey (Refereed)
    Abstract [en]

    Geomorphological mapping is a well-established method for examining earth surface processes and landscape evolution in a range of environmental contexts. In glacial research, it provides crucial data for a wide range of process-oriented studies and palaeoglaciological reconstructions; in the latter case providing an essential geomorphological framework for establishing glacial chronologies. In recent decades, there have been significant developments in remote sensing and Geographical Information Systems (GIS), with a plethora of high quality remotely-sensed datasets now (often freely) available. Most recently, the emergence of unmanned aerial vehicle (UAV) technology has allowed sub-decimetre scale aerial images and Digital Elevation Models (DEMs) to be obtained. Traditional field mapping methods still have an important role in glacial geomorphology, particularly in cirque glacier, valley glacier and icefield/ice-cap outlet settings. Field mapping is also used in ice sheet settings, but often takes the form of necessarily highly-selective ground-truthing of remote mapping. Given the increasing abundance of datasets and methods available for mapping, effective approaches are necessary to enable assimilation of data and ensure robustness. This paper provides a review and assessment of the various glacial geomorphological methods and datasets currently available, with a focus on their applicability in particular glacial settings. We distinguish two overarching 'work streams' that recognise the different approaches typically used in mapping landforms produced by ice masses of different sizes: (i) mapping of ice sheet geomorphological imprints using a combined remote sensing approach, with some field checking (where feasible); and (ii) mapping of alpine and plateau-style ice mass (cirque glacier, valley glacier, icefield and ice-cap) geomorphological imprints using remote sensing and considerable field mapping. Key challenges to accurate and robust geomorphological mapping are highlighted, often necessitating compromises and pragmatic solutions. The importance of combining multiple datasets and/or mapping approaches is emphasised, akin to multi-proxy approaches used in many Earth Science disciplines. Based on our review, we provide idealised frameworks and general recommendations to ensure best practice in future studies and aid in accuracy assessment, comparison, and integration of geomorphological data. These will be of particular value where geomorphological data are incorporated in large compilations and subsequently used for palaeoglaciological reconstructions. Finally, we stress that robust interpretations of glacial landforms and landscapes invariably requires additional chronological and/or sedimentological evidence, and that such data should ideally be collected as part of a holistic assessment of the overall glacier system.

  • 142.
    Charpentier Ljungqvist, Fredrik
    et al.
    Stockholm University, Faculty of Humanities, Department of History.
    Krusic, Paul J.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Luterbacher, J.
    González-Rouco, J.F.
    García Bustamante, E.
    Melo Aguilar, C.A.
    Werner, J.P.
    Summer temperature and drought co-variability: Euro-Med2k workshop, Stockholm, Sweden, 1-2 December 20162017In: PAGES News, ISSN 1811-1602, E-ISSN 1811-1610, Vol. 25, no 2, p. 112-112Article in journal (Other academic)
  • 143.
    Charpentier Ljungqvist, Fredrik
    et al.
    Stockholm University, Faculty of Humanities, Department of History.
    Krusic, Paul J.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Sundqvist, Hanna S.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Zorita, Eduardo
    Brattström, Gudrun
    Stockholm University, Faculty of Science, Department of Mathematics.
    Frank, David
    Northern Hemisphere hydroclimate variability over the past twelve centuries2016In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 532, no 7597, p. 94-98Article in journal (Refereed)
    Abstract [en]

    Accurate modelling and prediction of the local to continental-scale hydroclimate response to global warming is essential given the strong impact of hydroclimate on ecosystem functioning, crop yields, water resources, and economic security. However, uncertainty in hydroclimate projections remains large, in part due to the short length of instrumental measurements available with which to assess climate models. Here we present a spatial reconstruction of hydroclimate variability over the past twelve centuries across the Northern Hemisphere derived from a network of 196 at least millennium-long proxy records. We use this reconstruction to place recent hydrological changes and future precipitation scenarios in a long-term context of spatially resolved and temporally persistent hydroclimate patterns. We find a larger percentage of land area with relatively wetter conditions in the ninth to eleventh and the twentieth centuries, whereas drier conditions are more widespread between the twelfth and nineteenth centuries. Our reconstruction reveals that prominent seesaw patterns of alternating moisture regimes observed in instrumental data across the Mediterranean, western USA, and China have operated consistently over the past twelve centuries. Using an updated compilation of 128 temperature proxy records, we assess the relationship between the reconstructed centennial-scale Northern Hemisphere hydroclimate and temperature variability. Even though dry and wet conditions occurred over extensive areas under both warm and cold climate regimes, a statistically significant co-variability of hydroclimate and temperature is evident for particular regions. We compare the reconstructed hydroclimate anomalies with coupled atmosphere-ocean general circulation model simulations and find reasonable agreement during pre-industrial times. However, the intensification of the twentieth-century-mean hydroclimate anomalies in the simulations, as compared to previous centuries, is not supported by our new multi-proxy reconstruction. This finding suggests that much work remains before we can model hydroclimate variability accurately, and highlights the importance of using palaeoclimate data to place recent and predicted hydroclimate changes in a millennium-long context.

  • 144.
    Charpentier Ljungqvist, Fredrik
    et al.
    Stockholm University, Faculty of Humanities, Department of History. University of Cambridge, United Kingdom.
    Seim, Andrea
    Krusic, Paul J.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Cambridge, United Kingdom.
    González-Rouco, Jesús Fidel
    Werner, Johannes P.
    Cook, Edward R.
    Zorita, Eduardo
    Luterbacher, Jürg
    Xoplaki, Elena
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    García-Bustainante, Elena
    Aguilar, Camilo Andrés Melo
    Seftigen, Kristina
    Wang, Jianglin
    Gagen, Mary H.
    Esper, Jan
    Solomina, Olga
    Fleitmann, Dominik
    Büntgen, Ulf
    European warm-season temperature and hydroclimate since 850 CE2019In: Environmental Research Letters, ISSN 1748-9326, E-ISSN 1748-9326, Vol. 14, no 8, article id 084015Article in journal (Refereed)
    Abstract [en]

    The long-term relationship between temperature and hydroclimate has remained uncertain due to the short length of instrumental measurements and inconsistent results from climate model simulations. This lack of understanding is particularly critical with regard to projected drought and flood risks. Here we assess warm-season co-variability patterns between temperature and hydroclimate over Europe back to 850 CE using instrumental measurements, tree-ring based reconstructions, and climate model simulations. We find that the temperature-hydroclimate relationship in both the instrumental and reconstructed data turns more positive at lower frequencies, but less so in model simulations, with a dipole emerging between positive (warm and wet) and negative (warm and dry) associations in northern and southern Europe, respectively. Compared to instrumental data, models reveal a more negative co-variability across all timescales, while reconstructions exhibit a more positive co-variability. Despite the observed differences in the temperature-hydroclimate co-variability patterns in instrumental, reconstructed and model simulated data, we find that all data types share relatively similar phase-relationships between temperature and hydroclimate, indicating the common influence of external forcing. The co-variability between temperature and soil moisture in the model simulations is overestimated, implying a possible overestimation of temperature-driven future drought risks.

  • 145.
    Charpentier Ljungqvist, Fredrik
    et al.
    Stockholm University, Faculty of Humanities, Department of History. University of Cambridge, United Kingdom.
    Tegel, Willy
    Krusic, Paul J.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Cambridge, United Kingdom.
    Seim, Andrea
    Gschwind, Friederike M.
    Haneca, Kristof
    Herzig, Franz
    Heussner, Karl-Uwe
    Hofmann, Jutta
    Houbrechts, David
    Kontic, Raymond
    Kyncl, Tomáš
    Leuschner, Hanns Hubert
    Nicolussi, Kurt
    Perrault, Christophe
    Pfeifer, Klaus
    Schmidhalter, Martin
    Seifert, Mathias
    Walder, Felix
    Westphal, Thorsten
    Büntgen, Ulf
    Linking European building activity with plague history2018In: Journal of Archaeological Science, ISSN 0305-4403, E-ISSN 1095-9238, Vol. 98, p. 81-92Article in journal (Refereed)
    Abstract [en]

    Variations in building activity reflect demographic, economic and social change during history. Tens of thousands of wooden constructions in Europe have been dendrochronologically dated in recent decades. We use the annually precise evidence from a unique dataset of 49 640 tree felling dates of historical constructions to reconstruct temporal changes in building activity between 1250 and 1699 CE across a large part of western and central Europe largely corresponding to the former Holy Roman Empire of the German Nation. Comparison with annual records of 9772 plague outbreaks shows that construction activity was significantly negatively correlated to the number of plague outbreaks, with the greatest decrease in construction following the larger outbreaks by three to four years after the start of the epidemics. Preceding the Black Death (1346-1353 CE) by five decades and the Great Famine (1315-1322 CE) by two decades, a significant decline in construction activity at c. 1300 CE is indicative of a societal crisis, associated with population stagnation or decline. Another dramatic decline in building activity coincides with the Thirty Years' War (1618-1648 CE) and confirms the devastating nature of this conflict. While construction activity was significantly lower during periods of high grain prices, no statistically robust relationship between the number of felling dates and past temperature or hydroclimate variations is found. This study demonstrates the value of dendrochronological felling dates as an indicator for times of crisis and prosperity during periods when documentary evidence is limited.

  • 146.
    Charpentier Ljungqvist, Fredrik
    et al.
    Stockholm University, Faculty of Humanities, Department of History. Swedish Collegium for Advanced Study, Sweden.
    Thejll, Peter
    Björklund, Jesper
    Gunnarson, Björn E.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Piermattei, Alma
    Rydval, Miloš
    Seftigen, Kristina
    Støvek, Bård
    Büntgen, Ulf
    Assessing non-linearity in European temperature-sensitive tree-ring data2020In: Dendrochronologia, ISSN 1125-7865, E-ISSN 1612-0051, Vol. 59, article id 125652Article in journal (Refereed)
    Abstract [en]

    We test the application of parametric, non-parametric, and semi-parametric calibration models for reconstructing summer (June-August) temperature from a set of tree-ring width and density data on the same dendro samples from 40 sites across Europe. By comparing the performance of the three calibration models on pairs of tree-ring width (TRW) and maximum density (MXD) or maximum blue intensity (MXBI), we test whether a non-linear temperature response is more prevalent in TRW or MXD (MXBI) data, and whether it is associated with the temperature sensitivity and/or autocorrelation structure of the dendro parameters. We note that MXD (MXBI) data have a significantly stronger temperature response than TRW data as well as a lower autocorrelation that is more similar to that of the instrumental temperature data, whereas TRW exhibits a redder variability continuum. This study shows that the use of non-parametric calibration models is more suitable for TRW data, while parametric calibration is sufficient for both MXD and MXBI data - that is, we show that TRW is by far the more non-linear proxy.

  • 147.
    Charpentier Ljungqvist, Fredrik
    et al.
    Stockholm University, Faculty of Humanities, Department of History. University of Cambridge, United Kingdom.
    Zhang, Qiong
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Brattström, Gudrun
    Stockholm University, Faculty of Science, Department of Mathematics.
    Krusic, Paul J.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Cambridge, United Kingdom.
    Seim, Andrea
    Li, Qiang
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Zhang, Qiang
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Moberg, Anders
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Centennial-Scale Temperature Change in Last Millennium Simulations and Proxy-Based Reconstructions2019In: Journal of Climate, ISSN 0894-8755, E-ISSN 1520-0442, Vol. 32, no 9, p. 2441-2482Article in journal (Refereed)
    Abstract [en]

    Systematic comparisons of proxy-based reconstructions and climate model simulations of past millennium temperature variability offer insights into climate sensitivity and feedback mechanisms, besides allowing model evaluation independently from the period covered by instrumental data. Such simulation-reconstruction comparisons can help to distinguish more skillful models from less skillful ones, which may subsequently help to develop more reliable future projections. This study evaluates the low-frequency simulation-reconstruction agreement within the past millennium through assessing the amplitude of temperature change between the Medieval Climate Anomaly (here, 950-1250 CE) and the Little Ice Age (here, 1450-1850 CE) in PMIP3 model simulations compared to proxy-based local and continental-scale reconstructions. The simulations consistently show a smaller temperature change than the reconstructions for most regions in the Northern Hemisphere, but not in the Southern Hemisphere, as well as a partly different spatial pattern. A cost function analysis assesses how well the various simulations agree with reconstructions. Disregarding spatial correlation, significant differences are seen in the agreement with the local temperature reconstructions between groups of models, but insignificant differences are noted when compared to continental-scale reconstructions. This result points toward a limited possibility to rank models by means of their low-frequency temperature variability alone. The systematically lower amplitude of simulated versus reconstructed temperature change indicates either too-small simulated internal variability or that the analyzed models lack some critical forcing or have missing or too-weak feedback mechanisms. We hypothesize that too-cold initial ocean conditions in the models-in combination with too-weak internal variability and slow feedbacks over longer time scales-could account for much of the simulation-reconstruction disagreement.

  • 148.
    Chen, Yuanying
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Royal Institute of Technology (KTH), Sweden.
    Cvetkovic, Vladimir
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Scenarios of Nutrient-Related Solute Loading and Transport Fate from Different Land Catchments and Coasts into the Baltic Sea2019In: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 11, no 7, article id 1407Article in journal (Refereed)
    Abstract [en]

    This study uses controlled numerical experimentation to comparatively simulate and investigate solute transport and concentration responses and patterns in the Baltic Sea for various solute releases from the land through two different coastal cases. These cases are the Swedish Kalmar County coast and the Polish coast of the Vistula River outlet. For equivalent solute releases, the coastal flow conditions and their interactions with main marine currents determine the local coastal solute spreading, while the overall spreading over the Baltic Sea is similar for the two coastal cases, despite their large local differences. For nutrient-proportional solute release scenarios, the highly-populated Vistula catchment yields much greater total, but smaller per-capita nutrient impacts, in the Baltic Sea than the Kalmar County catchment. To be as low as from the Vistula catchment, the per-capita nutrient contribution from Kalmar County would have to be reduced much more than required on average per Swedish inhabitant by the Baltic Sea Action Plan. This highlights an unfairness issue in the per-capita distribution of nutrient load allowance among the Baltic countries, which needs to be considered and handled in further research and international efforts aimed to combat the Baltic Sea eutrophication.

  • 149.
    Chen, Yuanying
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Royal Institute of Technology (KTH), Sweden.
    Vigouroux, Guillaume
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Bring, Arvid
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Cvetkovic, Vladimir
    Destouni, Georgia
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Dominant Hydro-Climatic Drivers of Water Temperature, Salinity, and Flow Variability for the Large-Scale System of the Baltic Coastal Wetlands2019In: Water, ISSN 2073-4441, E-ISSN 2073-4441, Vol. 11, no 3, article id 552Article in journal (Refereed)
    Abstract [en]

    For the large-scale coastal wetland system of the Baltic Sea, this study develops a methodology for investigating if and to what degree the variability and changes in certain hydro-climatic drivers control key coastal-marine physical conditions. The studied physical conditions include: (a) water temperature, (b) water salinity, and (c) flow structures (magnitudes and directions of flows between marine basins and the associated coastal zones and wetlands). We use numerical simulations of three hydro-climatically distinct cases to investigate the variations in hydro-climatic drivers and the resulting physical conditions (a-c) among the cases. The studied hydro-climatic forcing variables are: net surface heat flux, wind conditions, saltwater influx from the North Sea, and freshwater runoff from land. For these variables, the available observation-based data show that the total runoff from land is significantly and positively correlated with precipitation on the sea itself, and negatively correlated with saltwater influx from the North Sea to the Baltic Sea. Overall, the physical condition (a-c) variability in the Baltic Sea and its coastal zones is found to be pairwise well-explained by simulation case differences as follows: (a) Net heat flux is a main control of sea water temperature. (b) Runoff from land, along with the correlated salt water influx from the North Sea, controls average sea salinity; with the variability of local river discharges shifting some coastal zones to deviate from the average sea condition. (c) Wind variability and change control the Baltic Sea flow structure, primarily in terms of flow magnitude and less so in terms of flow direction. For specific coastal wetland zones, considerable salinity differences from average Baltic Sea conditions (due to variability in local river discharges) are found for the coasts of Finland and Estonia, while the coastal wetland zones of south-eastern Sweden, and of Estonia and Latvia, emerge as particularly sensitive to wind shifts.

  • 150. Cheng, Chuntian
    et al.
    Chen, Fu
    Li, Gang
    Ristić, Bora
    Mirchi, Ali
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Texas at El Paso, USA.
    Tu, Qiyu
    Madani, Kaveh
    Stockholm University, Faculty of Science, Department of Physical Geography. Imperial College London, United Kingdom.
    Reform and renewables in China: The architecture of Yunnan's hydropower dominated electricity market2018In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 94, p. 682-693Article, review/survey (Refereed)
    Abstract [en]

    Reforms currently under way in China's electricity markets bear important implications for its decarbonization objectives. The southwestern province of Yunnan is among the provinces piloting the current iteration of power market reforms. As such, lessons from Yunnan will inform future market reform and renewable energy policies in China and potentially elsewhere. The dominance of hydropower in Yunnan's energy portfolio and the particular transmission constraints it faces, offer an interesting case study of the challenges of decarbonization. We report on market architecture reforms and aggregate market data collected from the Yunnan Power Exchange. We review four elements in the reformed market architecture. Market pricing rules, transitional quantity controls, the generation rights market, and inter-provincial trade. The specifics of market reform reflect a compromise between decarbonization, inter-provincial competition, grid security and development objectives and contribute to understanding of how the dual transitions of hydropower decarbonization and market liberalization interact. We conclude on six insights regarding the role of the grid operator, security checks on trade, integration of cascade hydropower, the inclusion of renewables in the generation rights market, price controls, and market participant price uncertainty.

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