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  • 1.
    Hattestrand, Martina
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Eight years of annual pollen monitoring in northern Sweden, from the boreal forest to above the birch forest-line2013In: Grana, ISSN 0017-3134, E-ISSN 1651-2049, Vol. 52, no 1, p. 26-48Article in journal (Refereed)
    Abstract [en]

    Pollen deposition during 1997-2004 was monitored for seven sites in northern Sweden, ranging from the boreal forest zone to above the birch forest-line. Fifty-three taxa were recorded in the traps. Of these, 22 are observed in the vegetation surrounding the trap sites. The remaining 31 taxa are most probably long distance transported. Taxa that strongly correlate with the site above the birch forest-line are Trientalis europaea, Asteraceae, Ericales and Linnaea borealis, while pollen of Pinus, Picea, Betula, Alnus and Juniperus correlates with sites within the boreal forest zone. A positive correlation is noted between pollen accumulation rates (PARs) of Pinus and Picea and mean July temperatures of the year prior to pollen release. A comparison between pollen counts retrieved from pollen traps, lake surface sediments and moss polster samples at one site shows similar pollen composition for the pollen trap and lake surface sediments, while the moss polster samples have higher percentage of Pinus pollen, lower percentage of Betula pollen and generally a lower diversity of pollen and spores.

  • 2.
    Hättestrand, Martina
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Vegetationsutveckling vid Rössberga (C-kurs arbete). In: Karlsson, S och Risberg, J., Miljöhistoria i södra Uppland - 7000-0 14C år BP Arlandabanan.1998Report (Other academic)
  • 3.
    Hättestrand, Martina
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jensen, C.
    Halsdóttir, M.
    Vorren, K.-D.
    Modern pollen accumulation rates at the north-western fringe of the European boreal forest2008In: Review of Paleobotany and Palynology, Vol. 151, p. 90-109Article in journal (Refereed)
  • 4.
    Hättestrand, Martina
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Robertsson, Ann-Marie
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Weichselian interstadials at Riipiharju, northern Sweden - interpretation of vegetation and climate from fossil and modern pollen records2010In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 39, no 2, p. 296-311Article in journal (Refereed)
    Abstract [en]

    The most complete records of Weichselian ice-free conditions in northern Sweden have been retrieved from kettleholes in the Riipiharju esker. In an earlier study, the Riipiharju I core was described as containing two Weichselian interstadials and Riipiharju was chosen as type site for the second Weichselian interstadial in northern Sweden. Here, we present a palynological investigation of two new sediment cores (Riipiharju II and III) retrieved from Riipiharju. Together, the new cores comprise a late cold part of the first Weichselian interstadial recorded in northeastern Sweden (Tarendo I, earlier correlated with Perapohjola in Finland) as well as a long sequence of the second Weichselian interstadial (Tarendo II, earlier named Tarendo). The results indicate that the climate during deposition of the Tarendo II sequence was more variable than earlier suggested. According to the present interpretation it was relatively warm in the early part of Tarendo II; thereafter a long cold phase persisted, and finally the climate was warmer again in the late part of Tarendo II. The warm phases are characterized by Betula-dominant pollen assemblages, while the cold phase is characterized by high percentages of Artemisia and Gramineae pollen. Since there is still no firm chronology established of the interstadials in northeastern Sweden, two possible correlations are discussed; either Tarendo I and II are correlated with Brorup (MIS 5c) and Odderade (MIS 5a), or, perhaps more likely, they are correlated with Odderade and early Middle Weichselian (MIS 3) time.

  • 5.
    Katrantsiotis, Christos
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Navarino Environmental Observatory (NEO), Greece.
    Kylander, Malin E.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Smittenberg, Rienk
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Yamoah, Kweku K. A.
    Hättestrand, Martina
    Stockholm University, Faculty of Science, Department of Physical Geography. Navarino Environmental Observatory (NEO), Greece.
    Avramidis, Pavlos
    Strandberg, Nichola A.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Norström, Elin
    Stockholm University, Faculty of Science, Department of Geological Sciences. Navarino Environmental Observatory (NEO), Greece.
    Eastern Mediterranean hydroclimate reconstruction over the last 3600 years based on sedimentary n-alkanes, their carbon and hydrogen isotope composition and XRF data from the Gialova Lagoon, SW Greece2018In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 194, p. 77-93Article in journal (Refereed)
    Abstract [en]

    Understanding past hydroclimate variability and related drivers is essential to improve climate forecasting capabilities especially in areas with high climatic sensitivity, such as the Mediterranean. This can be achieved by using a broad spectrum of high resolution, multiple proxy records which can also allow us to assess linkages between regional hydroclimate variability and shifts in the large-scale atmospheric patterns. Here, we present a multiproxy reconstruction of the central-eastern Mediterranean hydro climate changes over the last 3600 years based on a sediment core from the Gialova Lagoon, a shallow coastal ecosystem in SW Peloponnese, Greece. Our combined dataset consists of the distribution and compound-specific carbon and hydrogen isotope (delta C-13 and 8D) composition of n-alkanes, bulk organic matter properties and X-ray fluorescence (XRF) core scanning data. This approach was complemented with a semi-quantitative analysis of plant remains in the core. The results indicate a high contribution of local aquatic vegetation to organic matter. Large delta C-13 variations in predominantly aquatic plant-derived mid-chain alkanes (C23-23) mainly reflect changes in the aquatic plant abundance and their carbon source. Our data suggest that higher delta C-13(23-25) values (up to 19 parts per thousand) largely correspond to expansion of aquatic vegetation during wet and/or cold periods causing carbon-limiting conditions in the water and assimilation of isotopically-enriched bicarbonate by the plants. The 8D records of the individual n-alkanes (C-17 to C-31) exhibit a nearly identical pattern to each other, which implies that they all reflect changes in the source water isotope composition, driven by hydroclimate variability. In addition, the 8D profiles are consistent with the XRF data with both proxies being driven by a common hydroclimate signal. We observe two major shifts from dry and/or warm periods at ca 3600-3000 cal BP and ca 17001300 cal BP to wet and/or cold episodes at ca 3000-2700 cal BP and ca 1300-900 cal BP. The period ca 700-200 cal BP is the wettest and/or coldest in our record and coeval with the Little Ice Age. The climatic fluctuation reported in this study can be explained by the relative dominance of high-latitude (e.g. North Atlantic Oscillation during winters) and the low-latitude atmospheric patterns (Intertropical convergence zone, Subtropical High and the effects of Asian monsoons during summers) which suggests an Atlantic-Mediterranean-Monsoon climate link in this area for the late Holocene.

  • 6.
    Katrantsiotis, Christos
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Navarino Environmental Observatory (NEO), Greece.
    Norström, Elin
    Stockholm University, Faculty of Science, Department of Geological Sciences. Navarino Environmental Observatory (NEO), Greece.
    Smittenberg, Rienk H.
    Stockholm University, Faculty of Science, Department of Geological Sciences.
    Finné, Martin
    Weiberg, Erika
    Hättestrand, Martina
    Stockholm University, Faculty of Science, Department of Physical Geography. Navarino Environmental Observatory (NEO), Greece.
    Avramidis, Pavlos
    Wastegård, Stefan
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Climate changes in the Eastern Mediterranean over the last 5000 years and their links to the high-latitude atmospheric patterns and Asian monsoons2019In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 175, p. 36-51Article in journal (Refereed)
    Abstract [en]

    This research aims to improve the knowledge of the mid to late Holocene climate changes and the underlying drivers in the eastern Mediterranean. We focus on the Peloponnese peninsula, SW Greece, characterized by a W-E rainfall/temperature gradient and a strong climate-sensitivity to shifts in the large-scale atmospheric patterns. A radiocarbon-dated sediment core, taken from the ancient Lake Lerna, a former lake in NE Peloponnese, was analyzed for distribution and hydrogen isotope (δD) composition of n-alkanes and bulk organic geochemistry (δ13C, TOC). The predominantly macrophyte (submerged/floating)-derived δD23 profile exhibits the largest long-term fluctuation in the record and co-varies with δD of long-chain n-alkanes providing evidence for precipitation and temperature changes over the last 5000 years. The Lerna δD23 signal is sometimes in agreement with other n-alkane δD records from SW Peloponnese indicating wetter conditions in the peninsula at ca 5000–4600, ca 4500–4100, ca 3000–2600 (more unstable in SW) and after ca 700 cal BP with drier periods at ca 4100–3900 and ca 1000–700 cal BP. Conversely, a NE-SW climate see-saw is revealed at ca 4600–4500, ca 3200, ca 2600–1800, and ca 1200–1000 cal BP when the δD23 Lerna exhibits more positive trends (drier in NE) with a reversal at ca 3900–3300, ca 3200–3000 and ca 1800–1300 cal BP. These opposing and sometimes similar signals between NE and SW Peloponnese can be explained by the relative dominance of high-latitude atmospheric patterns over the peninsula. A similar signal would be expected when the North Atlantic Oscillation (NAO) exerts the main control with NAO (+) creating conditions of reduced moisture. The dipole pattern is likely driven by shifts in North Sea–Caspian Atmospheric pattern (NCP), which account for the present-day regional climate variability with NCP (+) leading to wetter and colder conditions in NE Peloponnese. The Asian monsoonal system likely has an additional impact on the δD variabilities through influencing the summer temperatures. There is a consistency between the Peloponnesian δD signals and monsoonal records after ca 4000 cal BP confirming the actualistic models. Strong monsoonal periods coincide with cooler summers (lower δD values) in Lerna, due to the northerly winds, the Etesians. On the contrary, SW Peloponnese is dominated by warmer conditions during the same periods as the area is located on the lee side of the mountain and highly influenced by the adiabatic warming associated with the subsidence over the Eastern Mediterranean.

  • 7. Näslund, Jens-Ove
    et al.
    Wohlfarth, Barbara
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Alexanderson, Helena
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Helmens, Karin
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hättestrand, Martina
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kleman, Johan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Lundqvist, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Brandefelt, Jenny
    Houmark-Nielsen, Michael
    Kjellström, Erik
    Strandberg, Gustav
    Knudsen, Karen-Luise
    Krog Larsen, Nikolai
    Ukkonen, Pirkko
    Mangerud, Jan
    Fennoscandian paleo-environment and ice sheet dynamics during Marine Isotope Stage (MIS) 3: Report of a workshop held September 20–21, 2007 in Stockholm, Sweden2008Report (Other academic)
  • 8. Treat, Claire C.
    et al.
    Kleinen, Thomas
    Broothaerts, Nils
    Dalton, April S.
    Dommain, Rene
    Douglas, Thomas A.
    Drexler, Judith Z.
    Finkelstein, Sarah A.
    Grosse, Guido
    Hope, Geoffrey
    Hutchings, Jack
    Jones, Miriam C.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Lacourse, Terri
    Lahteenoja, Outi
    Loisel, Julie
    Notebaert, Bastiaan
    Payne, Richard J.
    Peteet, Dorothy M.
    Sannel, A. Britta K.
    Stelling, Jonathan M.
    Strauss, Jens
    Swindles, Graeme T.
    Talbot, Julie
    Tarnocai, Charles
    Verstraeten, Gert
    Williams, Christopher J.
    Xia, Zhengyu
    Yu, Zicheng
    Valiranta, Minna
    Hättestrand, Martina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Alexanderson, Helena
    Brovkin, Victor
    Widespread global peatland establishment and persistence over the last 130,000 y2019In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 116, no 11, p. 4822-4827Article in journal (Refereed)
    Abstract [en]

    Glacial-interglacial variations in CO2 and methane in polar ice cores have been attributed, in part, to changes in global wetland extent, but the wetland distribution before the Last Glacial Maximum (LGM, 21 ka to 18 ka) remains virtually unknown. We present a study of global peatland extent and carbon (C) stocks through the last glacial cycle (130 ka to present) using a newly compiled database of 1,063 detailed stratigraphic records of peat deposits buried by mineral sediments, as well as a global peatland model. Quantitative agreement between modeling and observations shows extensive peat accumulation before the LGM in northern latitudes (> 40 degrees N), particularly during warmer periods including the last interglacial (130 ka to 116 ka, MIS 5e) and the interstadial (57 ka to 29 ka, MIS 3). During cooling periods of glacial advance and permafrost formation, the burial of northern peatlands by glaciers and mineral sediments decreased active peatland extent, thickness, and modeled C stocks by 70 to 90% from warmer times. Tropical peatland extent and C stocks show little temporal variation throughout the study period. While the increased burial of northern peats was correlated with cooling periods, the burial of tropical peat was predominately driven by changes in sea level and regional hydrology. Peat burial by mineral sediments represents a mechanism for long-term terrestrial C storage in the Earth system. These results show that northern peatlands accumulate significant C stocks during warmer times, indicating their potential for C sequestration during the warming Anthropocene.

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