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  • 1. Ahlström, A. P.
    et al.
    Anderson, B.
    Arenillas, M.
    Bajracharya, S.
    Baroni, C.
    Bidlake, W. R.
    Braun, L. N.
    Caceres, B.
    Casassa, G.
    Ceballos, J. L.
    Cobos, G.
    Davila, L. R.
    Delgado Granados, H.
    Demberel, O.
    Demuth, M. N.
    Espizua, L.
    Fischer, A.
    Fujita, K.
    Gadek, B.
    Ghazanfar, A.
    Hagen, J. O.
    Hoelzle, M.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Karimi, N.
    Li, Z.
    Martinez De Pison, E.
    Pelto, M.
    Pitte, P.
    Popovnin, V. V.
    Portocarrero, C. A.
    Prinz, R.
    Ramirez, J.
    Rudell, A.
    Sangewar, C.
    Severskiy, I
    Sigurdsson, O.
    Soruco, A.
    Tielidze, L.
    Usubaliev, R.
    Van Ommen, T.
    Vincent, C.
    Yakovlev, A.
    Historically unprecedented global glacier decline in the early 21st century2015In: Journal of Glaciology, ISSN 0022-1430, E-ISSN 1727-5652, Vol. 61, no 228, p. 745-+Article in journal (Refereed)
    Abstract [en]

    Observations show that glaciers around the world are in retreat and losing mass. Internationally coordinated for over a century, glacier monitoring activities provide an unprecedented dataset of glacier observations from ground, air and space. Glacier studies generally select specific parts of these datasets to obtain optimal assessments of the mass-balance data relating to the impact that glaciers exercise on global sea-level fluctuations or on regional runoff. In this study we provide an overview and analysis of the main observational datasets compiled by the World Glacier Monitoring Service (WGMS). The dataset on glacier front variations (similar to 42 000 since 1600) delivers clear evidence that centennial glacier retreat is a global phenomenon. Intermittent readvance periods at regional and decadal scale are normally restricted to a subsample of glaciers and have not come close to achieving the maximum positions of the Little Ice Age (or Holocene). Glaciological and geodetic observations (similar to 5200 since 1850) show that the rates of early 21st-century mass loss are without precedent on a global scale, at least for the time period observed and probably also for recorded history, as indicated also in reconstructions from written and illustrated documents. This strong imbalance implies that glaciers in many regions will very likely suffer further ice loss, even if climate remains stable.

  • 2.
    Christiansen, Hanne H.
    et al.
    Geology Department, The University Centre in Svalbard, UNIS, Norway.
    Etzelmüller, Bernd
    Department of Geosciences, The University of Oslo, Norway.
    Isaksen, Ketil
    Norwegian Meteorological Institute, Norway.
    Juliussen, Håvard
    Geology Department, The University Centre in Svalbard, UNIS, Norway.
    Farbrot, Herman
    Department of Geosciences, The University of Oslo, Norway.
    Humlum, Ole
    Geology Department, The University Centre in Svalbard, UNIS, Norway.
    Johansson, Margareta
    GeoBiosphere Science Centre, Department of Physical Geography and Ecosystem Analyses, Lund University, Sweden.
    Ingeman-Nielsen, T.
    Department of Civil Engineering, The Technical University of Denmark, Denmark.
    Kristensen, Lene
    Geology Department, The University Centre in Svalbard, UNIS, Norway.
    Hjort, Jan
    Department of Geography, University of Helsinki, Finland.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Sannel, A. Britta K.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Sigsgaard, Charlotte
    Department of Geography and Geology, University of Copenhagen, Denmark.
    Åkerman, H. Jonas
    GeoBiosphere Science Centre, Department of Physical Geography and Ecosystem Analyses, Lund University, Sweden.
    Foged, Nils
    Department of Civil Engineering, The Technical University of Denmark, Denmark.
    Blikra, Lars H.
    International Centre for Geohazards, Åknes/Tafjord Early Warning Centre, Norway.
    Pernosky, M. A.
    Asiaq, Greenland Survey, Nuuk, Greenland.
    Ødegård, Rune S.
    Gjøvik University College, Norway.
    The thermal state of permafrost in the Nordic area during the International Polar Year 2007-20092010In: Permafrost and Periglacial Processes, ISSN 1045-6740, E-ISSN 1099-1530, Vol. 21, no 2, p. 156-181Article in journal (Refereed)
    Abstract [en]

    This paper provides a snapshot of the permafrost thermal state in the Nordic area obtained during the International Polar Year (IPY) 2007–2009. Several intensive research campaigns were undertaken within a variety of projects in the Nordic countries to obtain this snapshot. We demonstrate for Scandinavia that both lowland permafrost in palsas and peat plateaus, and large areas of permafrost in the mountains are at temperatures close to 0°C, which makes them sensitive to climatic changes. In Svalbard and northeast Greenland, and also in the highest parts of the mountains in the rest of the Nordic area, the permafrost is somewhat colder, but still only a few degrees below the freezing point. The observations presented from the network of boreholes, more than half of which were established during the IPY, provide an important baseline to assess how future predicted climatic changes may affect the permafrost thermal state in the Nordic area. Time series of active-layer thickness and permafrost temperature conditions in the Nordic area, which are generally only 10 years in length, show generally increasing active-layer depths and rising permafrost temperatures.

  • 3.
    Clason, Caroline C.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Applegate, Patrick
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Modelling Late Weichselian evolution of the Eurasian ice sheets forced by surface meltwater-enhanced basal sliding2014In: Journal of Glaciology, ISSN 0022-1430, E-ISSN 1727-5652, Vol. 60, no 219, p. 29-40Article in journal (Refereed)
    Abstract [en]

    We simulated the Late Weichselian extent and dynamics of the Eurasian ice sheets using theshallow-ice approximation ice-sheet model SICOPOLIS. Our simulated Last Glacial Maximum ice-sheetextents closely resemble geomorphological reconstructions, and areas of modelled fast flow areconsistent with the known locations of palaeo-ice streams. Motivated by documented velocity responseto increased meltwater inputs on Greenland, we tested the sensitivity of the simulated ice sheet to thesurface meltwater effect (SME) through a simple parameterization relating basal sliding to local surfacemelt rate and ice thickness. Model runs including the SME produce significantly reduced ice volumeduring deglaciation, with maximum ice surface velocities much greater than in similar runs that neglectthe SME. We find that the simple treatment of the SME is not applicable across the whole ice sheet;however, our results highlight the importance of the SME for dynamic response to increased melting.The southwest sector of the Scandinavian ice sheet is most sensitive to the SME, with fast flow in theBaltic ice stream region shutting off by 15 kaBP when the SME is turned on, coincident with a retreat ofthe ice-margin position into the Gulf of Bothnia.

  • 4.
    Clason, Caroline C.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. Plymouth University, UK.
    Greenwood, Sarah L.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Selmes, Nick
    Lea, James M.
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Liverpool, UK.
    Jamieson, Stewart S. R.
    Nick, Faezeh M.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Controls on the early Holocene collapse of the Bothnian Sea Ice Stream2016In: Journal of Geophysical Research - Earth Surface, ISSN 2169-9003, E-ISSN 2169-9011, Vol. 121, no 12, p. 2494-2513Article in journal (Refereed)
    Abstract [en]

    New high-resolution multibeam data in the Gulf of Bothnia reveal for the first time the subglacial environment of a Bothnian Sea Ice Stream. The geomorphological record suggests that increased meltwater production may have been important in driving rapid retreat of Bothnian Sea Ice during deglaciation. Here we apply a well-established, one-dimensional flow line model to simulate ice flow through the Gulf of Bothnia and investigate controls on retreat of the ice stream during the post-Younger Dryas deglaciation of the Fennoscandian Ice Sheet. The relative influence of atmospheric and marine forcings are investigated, with the modeled ice stream exhibiting much greater sensitivity to surface melting, implemented through surface mass balance and hydrofracture-induced calving, than to submarine melting or relative sea level change. Such sensitivity is supported by the presence of extensive meltwater features in the geomorphological record. The modeled ice stream does not demonstrate significant sensitivity to changes in prescribed ice stream width or overall bed slope, but local variations in basal topography and ice stream width result in nonlinear retreat of the grounding line, notably demonstrating points of short-lived retreat slowdown on reverse bed slopes. Retreat of the ice stream was most likely governed by increased ice surface meltwater production, with the modeled retreat rate less sensitive to marine forcings despite the marine setting.

  • 5. Eisen, Olaf
    et al.
    Frezzotti, Massimo
    Genthon, Christophe
    Isaksson, Elisabeth
    Magand, Olivier
    van den Broeke, Michiel
    Dixon, Daniel
    Ekaykin, Alexey
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    kameda, Takao
    Karlöf, Lars
    Kaspari, Susan
    Lipenkov, vladimir
    Oerter, Hans
    Takahashi, Shuhei
    Vaughan, David
    Ground-based measurements of spatial and temporal variability of snow accumulation in East Antarctica2008In: Reviews of Geophysics, ISSN 8755–1209, Vol. 46, p. 1-39Article in journal (Refereed)
    Abstract [en]

    The East Antarctic Ice Sheet is the largest, highest, coldest, driest, and windiest ice sheet on Earth. Understanding of the surface mass balance (SMB) of Antarctica is necessary to determine the present state of the ice sheet, to make predictions of its potential contribution to sea level rise, and to determine its past history for paleoclimatic reconstructions. However, SMB values are poorly known because of logistic constraints in extreme polar environments, and they represent one of the biggest challenges of Antarctic science. Snow accumulation is the most important parameter for the SMB of ice sheets. SMB varies on a number of scales, from small-scale features (sastrugi) to ice-sheet-scale SMB patterns determined mainly by temperature, elevation, distance from the coast, and wind-driven processes. In situ measurements of SMB are performed at single points by stakes, ultrasonic sounders, snow pits, and firn and ice cores and laterally by continuous measurements using ground-penetrating radar. SMB for large regions can only be achieved practically by using remote sensing and/or numerical climate modeling. However, these techniques rely on ground truthing to improve the resolution and accuracy. The separation of spatial and temporal variations of SMB in transient regimes is necessary for accurate interpretation of ice core records. In this review we provide an overview of the various measurement techniques, related difficulties, and limitations of data interpretation; describe spatial characteristics of East Antarctic SMB and issues related to the spatial and temporal representativity of measurements; and provide recommendations on how to perform in situ measurements.

  • 6. Fretwell, P.
    et al.
    Pritchard, H. D.
    Vaughan, D. G.
    Bamber, J. L.
    Barrand, N. E.
    Bell, R.
    Bianchi, C.
    Bingham, R. G.
    Blankenship, D. D.
    Casassa, G.
    Catania, G.
    Callens, D.
    Conway, H.
    Cook, A. J.
    Corr, H. F. J.
    Damaske, D.
    Damm, V.
    Ferraccioli, F.
    Forsberg, R.
    Fujita, S.
    Gim, Y.
    Gogineni, P.
    Griggs, J. A.
    Hindmarsh, R. C. A.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Holt, J. W.
    Jacobel, R. W.
    Jenkins, A.
    Jokat, W.
    Jordan, T.
    King, E. C.
    Kohler, J.
    Krabill, W.
    Riger-Kusk, M.
    Langley, K. A.
    Leitchenkov, G.
    Leuschen, C.
    Luyendyk, B. P.
    Matsuoka, K.
    Mouginot, J.
    Nitsche, F. O.
    Nogi, Y.
    Nost, O. A.
    Popov, S. V.
    Rignot, E.
    Rippin, D. M.
    Rivera, A.
    Roberts, J.
    Ross, N.
    Siegert, M. J.
    Smith, A. M.
    Steinhage, D.
    Studinger, M.
    Sun, B.
    Tinto, B. K.
    Welch, B. C.
    Wilson, D.
    Young, D. A.
    Xiangbin, C.
    Zirizzotti, A.
    Bedmap2: improved ice bed, surface and thickness datasets for Antarctica2013In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 7, no 1, p. 375-393Article in journal (Refereed)
    Abstract [en]

    We present Bedmap2, a new suite of gridded products describing surface elevation, ice-thickness and the seafloor and subglacial bed elevation of the Antarctic south of 60 degrees S. We derived these products using data from a variety of sources, including many substantial surveys completed since the original Bedmap compilation (Bedmap1) in 2001. In particular, the Bedmap2 ice thickness grid is made from 25 million measurements, over two orders of magnitude more than were used in Bedmap1. In most parts of Antarctica the subglacial landscape is visible in much greater detail than was previously available and the improved data-coverage has in many areas revealed the full scale of mountain ranges, valleys, basins and troughs, only fragments of which were previously indicated in local surveys. The derived statistics for Bedmap2 show that the volume of ice contained in the Antarctic ice sheet (27 million km(3)) and its potential contribution to sea-level rise (58 m) are similar to those of Bedmap1, but the mean thickness of the ice sheet is 4.6% greater, the mean depth of the bed beneath the grounded ice sheet is 72m lower and the area of ice sheet grounded on bed below sea level is increased by 10 %. The Bedmap2 compilation highlights several areas beneath the ice sheet where the bed elevation is substantially lower than the deepest bed indicated by Bedmap1. These products, along with grids of data coverage and uncertainty, provide new opportunities for detailed modelling of the past and future evolution of the Antarctic ice sheets.

  • 7. Fujita, S.
    et al.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Andersson, I.
    Brown, Ian
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Enomoto, H.
    Fujii, Y.
    Fujita, K.
    Fukui, K.
    Furukawa, T.
    Hansson, M.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hara, K.
    Hoshina, Y.
    Igarashi, M.
    Iizuka, Y.
    Imura, S.
    Ingvander, Susanne
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Karlin, Torbjörn
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Motoyama, H.
    Nakazawa, F.
    Oerter, H.
    Sjöberg, L. E.
    Sugiyama, S.
    Surdyk, S.
    Ström, Johan
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Uemura, R.
    Wilhelms, F.
    Spatial and temporal variability of snow accumulation rate on the East Antarctic ice divide between Dome Fuji and EPICA DML2011In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 5, no 4, p. 1057-1081Article in journal (Refereed)
    Abstract [en]

    To better understand the spatio-temporal variability of the glaciological environment in Dronning Maud Land (DML), East Antarctica, a 2800-km-long Japanese-Swedish traverse was carried out. The route includes ice divides between two ice-coring sites at Dome Fuji and EPICA DML. We determined the surface mass balance (SMB) averaged over various time scales in the late Holocene based on studies of snow pits and firn cores, in addition to radar data. We find that the large-scale distribution of the SMB depends on the surface elevation and continentality, and that the SMB differs between the windward and leeward sides of ice divides for strong-wind events. We suggest that the SMB is highly influenced by interactions between the large-scale surface topography of ice divides and the wind field of strong-wind events that are often associated with high-precipitation events. Local variations in the SMB are governed by the local surface topography, which is influenced by the bedrock topography. In the eastern part of DML, the accumulation rate in the second half of the 20th century is found to be higher by similar to 15% than averages over longer periods of 722 a or 7.9 ka before AD 2008. A similar increasing trend has been reported for many inland plateau sites in Antarctica with the exception of several sites on the leeward side of the ice divides.

  • 8. Fujita, S.
    et al.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Matsuoka, K.
    Enomoto, H.
    Fukui, K.
    Nakazawa, F.
    Sugiyama, S.
    Surdyk, S.
    Radar diagnosis of the subglacial conditions in Dronning Maud Land, East Antarctica2012In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 6, no 5, p. 1203-1219Article in journal (Refereed)
    Abstract [en]

    In order to better understand the spatial distribution of subglacial environments, ground-based radar profiling data were analyzed for a total distance of similar to 3300 km across Dronning Maud Land, East Antarctica. The relationship between geometrically corrected bed returned power [Pc bed] dB in decibels and ice thickness H was examined. When H is smaller than a critical value that varies according to location, [P-bed(c)](dB) tends to decrease relatively smoothly with increasing H, which is explicable primarily by the cumulative effect of dielectric attenuation within the ice. However, at locations where H is larger than the critical H values, anomalous increases and fluctuations in [P-bed(c)](dB) were observed, regardless of the choice of radar frequency or radar-pulse width. In addition, the amplitude of the fluctuations often range 10 similar to 20 dB. We argue that the anomalous increases are caused by higher bed reflectivity associated with the existence of subglacial water. We used these features to delineate frozen and temperate beds. Approximately two-thirds of the investigated area was found to have a temperate bed. The beds of the inland part of the ice sheet tend to be temperate, with the exception of subglacial high mountains. In contrast, the beds of coastal areas tend to be frozen, with the exception of fast-flowing ice on the subglacial lowland or troughs. We argue that this new analytical method can be applied to other regions.

  • 9.
    Holmlund, Erik S.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. University Centre in Svalbard, Norway.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Constraining 135 years of mass balance with historic structure-from-motion photogrammetry on Storglaciaren, Sweden2019In: Geografiska Annaler. Series A, Physical Geography, ISSN 0435-3676, E-ISSN 1468-0459, Vol. 101, no 3, p. 195-210Article in journal (Refereed)
    Abstract [en]

    Geodetic volume estimates of Storglaciaren in Sweden suggest a 28% loss in total ice mass between 1910 and 2015. Terrestrial photographs from 1910 of Tarfala valley, where Storglaciaren is situated, allow for an accurate reconstruction of the glacier's surface using Structure-from-Motion photogrammetry, which we used for past volume and mass estimations. The glacier's yearly mass balance gradient and net mass balance was also estimated back to 1880 using weather data from Karesuando, 170 km north-east of Storglaciaren, through neural network regression. These combined reconstructions provide a continuous mass change series between the end of the Little Ice Age and 1946, when field data become available. The resultant reconstruction suggests a state close to equilibrium between 1880 and the 1910s, followed by drastic melt until the 1970s, constituting 76% of the 1910-2015 ice loss. More favourable conditions subsequently stabilized the mass balance until the late 1990s, after which Storglaciaren started losing mass again. The 1910 reconstruction allows for a more accurate mass change series than previous estimates, and the methodology can be used on other glaciers where early photographic material exists.

  • 10.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Antarktis vidder, ett hotat område2008Other (Other (popular science, discussion, etc.))
  • 11.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Glaciärer: Gnistrande smycken som ännu pryder våra svenska fjäll2012Book (Other (popular science, discussion, etc.))
  • 12.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Glaciärforskaren Axel Hamberg2012In: Sarek, Arktis och akademisk vardag: En bok om geografen Axel Hamberg / [ed] Lars Andersson, Uppsala: Acta Universitatis Upsaliensis, 2012, p. 113-134Chapter in book (Other academic)
  • 13.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Haverier på isen blev vår julstress2007Other (Other (popular science, discussion, etc.))
  • 14.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Sulitelmas isar2012In: Sommarland och högfjäll: Badjelánnda och Sulidälbmà / [ed] Eva Selin, Arthur Lindroth, Stockholm: Svenska fjällklubben , 2012, p. 22-35Chapter in book (Other (popular science, discussion, etc.))
  • 15.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Summary of International Glacier Monitoring Summit2011In: NASA, The Earth Observer, Vol. 23, no 4, p. 28-31Article in journal (Refereed)
    Abstract [en]

    To answer questions about linkages between changes in glaciers and climate change—e.g., How much of the current global sea-level rise can be attributed to melting glaciers?—more precise and quantitative studies of glaciers are required. This includes systematically extending the available in situ and remote sensing data, putting together a more-detailed world glacier inventory (WGI), continuing and strategically enlarging the global mass balance monitoring network, and conducting a rigorous uncertainty assessment of the available data series.

  • 16.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Vi nådde Antarktis i förledande sol2007Other (Other (popular science, discussion, etc.))
  • 17.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Vit kontinent berättar om klimatets historia: Miljöforskning2007In: Miljöforskning: Formas tidning för ett uthålligt samhälle, no 1, p. 22-25Article in journal (Other academic)
  • 18.
    Holmlund, Per
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Holmlund, Erik S.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Recent climate-induced shape changes of the ice summit of Kebnekaise, Northern Sweden2019In: Geografiska Annaler. Series A, Physical Geography, ISSN 0435-3676, E-ISSN 1468-0459, Vol. 101, no 1, p. 68-78Article in journal (Refereed)
    Abstract [en]

    The ice summit of Kebnekaise is slowly melting down as a consequence of climate change. In August 2018 this peak, which for a long time has been the highest in Sweden, reached an elevation a few decimetres lower than the nearby situated northern summit in solid rock. It has become a symbol of the fragility of nature. Its areal extent and shape have varied over time and its height has ranged within approximately 15 m during the twentieth century. Since the turn of the century, the ice summit has decreased to a new lower and smaller level but the changes are not uniform, and they show a complex relation between weather parameters and the shape and size of the summit. Layers in the ice include climate information of past changes. But what changes are we able to determine by examining gradually exposed dust layers, or by coring the summit. In this paper, we are analysing the late changes in shape and volume of the ice summit and we place the results into a paleo climate discussion. We have used photogrammetric methods to map the geometry of the summit at different dates when data has been available. We have also done a multiple regression to analyse the relation between the summit elevation and the net mass balance of the nearby located Storglaciaren. The correlation is good from mid 1970s until now but weak prior to that. It is herein explained by former uncertainties of the geographic position of the summit.

  • 19.
    Ingvander, Susanne
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Brown, Ian A.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Johansson, Cecilia
    Rosqvist, Gunhild
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Method study: Grain size sampling and digital object oriented image analysis for explanation of snow grain size, shape and distributionIn: Journal of Glaciology, ISSN 0022-1430, E-ISSN 1727-5652Article in journal (Refereed)
    Abstract [en]

    We have developed a digital image processing method for snow particle size and shape analysis suitable for quick and reliable analysis in the eld. Snow particle size is an important parameter strongly aecting snow cover albedo from seasonally snow covered areas and ice sheets. It is also important in remote sensing analysis because it influences the reflectance and scattering properties of the snow. Alternatively traditional methods based on visual inspection of samples can be used but they do not yield quantitative data. Our method provides an additional alternative to both simpler and more complex methods by providinga tool that limits the subjective eect of the visual analysis and provides a quantitativeparticle size distribution. The method involves image analysis software and field efficient instrumentation in order to develop a complete process-chain easily implemented under field conditions. The results from the analysis are a two dimensional analysis of particle size, shape and distributions for each sample. The developed method improves snow particle analysis being quantitative, reproducible and applicable for dierent types of eld sites.

  • 20.
    Ingvander, Susanne
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Brown, Ian A.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Peter
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Johansson, Cecilia
    Rosqvist, Gunhild
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Particle Size Sampling and Object-Oriented Image Analysis for Field Investigations of Snow Particle Size, Shape, and Distribution2013In: Arctic, Antarctic and Alpine research, ISSN 1523-0430, E-ISSN 1938-4246, Vol. 45, no 3, p. 330-341Article in journal (Refereed)
    Abstract [en]

    Snow particle size is an important parameter strongly affecting snow cover broadband albedo from seasonally snow covered areas and ice sheets. It is also important in remote sensing analyses because it influences the reflectance and scattering properties of the snow. We have developed a digital image processing method for the capture and analysis of data of snow particle size and shape. The method is suitable for quick and reliable data capture in the field. Traditional methods based on visual inspection of samples have been used but do not yield quantitative data. Our method provides an alternative to both simpler and more complex methods by providing a tool that limits the subjective effect of the visual analysis and provides a quantitative particle size distribution. The method involves image analysis software and field efficient instrumentation in order to develop a complete process-chain easily implemented under field conditions. The output from the analysis is a two-dimensional analysis of particle size, shape, and distributions for each sample. The results of the segmentation process were validated against manual delineation of snow particles. The developed method improves snow particle analysis because it is quantitative, reproducible, and applicable for different types of field sites.

  • 21.
    Ingvander, Susanne
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Brown, Ian A.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Fujita, Shuji
    Sugyama, Shin
    Surdyk, Sylviane
    Enomoto, Hiroyouki
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Regional and local Snow Grain Size variations in Dronning Maud Land, Antarctica and analysis of various distribution scalesManuscript (preprint) (Other academic)
    Abstract [en]

    Understanding spatial snow particle size variations are key to help interpretation of remotely sensed data of snow cover. In the case of Antarctica, remote sensing is the only viable option to estimate the surface mass balance of the ice sheet on continental scale. We have investigated snow particle size variability along a transect from the coast onto the polar plateau in Dronning Maud Land, Antarctica, to better understand the spatial and temporal variations in surface snow properties. Two daily samples were collected during a 55 day traverse to capture the regional variability. Local variability was assessed by sampling in grids at selected locations and the particle size and shape distributions for each site was analysed through digital image analysis, which has the benefit of yielding large quantities of reproducible quantitative data without the need for advanced laboratory analysis. The results provide an understanding of the complexity of snow particle size variability at different scales and show a variability range from 0.18–3.31 mm depending on the sample type (surface, grid or pit). We can verify relationships between grain size and both elevation and distance to the coast (moisture source) but have also identified regional seasonal changes, particularly on the lower elevations of the polar plateau. Our data provide possibilities to quantitatively assess the optical properties of the surface snow for remote sensing. The details of the spatial and temporal variations observed in our data provides a basis for further studies of the complex and coupled processes affecting snow particle size and the interpretation of remote sensing of snow covered areas.

  • 22.
    Ingvander, Susanne
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Brown, Ian A.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Fujita, Shuji
    Sugyama, Shin
    Surdyk, Sylviane
    Enomoto, Hiroyuki
    Hansson, Margareta
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Snow particle sizes and their distributions in Dronning Maud Land, Antarctica, at sample, local and regional scales2016In: Antarctic Science, ISSN 0954-1020, E-ISSN 1365-2079, Vol. 28, no 3, p. 219-231Article in journal (Refereed)
    Abstract [en]

    In this study, snow particle size variability was investigated along a transect in Dronning Maud Land from the coast to the polar plateau. The aim of the study was to better understand the spatial and temporal variations in surface snow properties. Samples were collected twice daily during a traverse in 2007-08 to capture regional variability. Local variability was assessed by sampling in 10 x 10m grids (5m spacing) at selected locations. The particle size and shape distributions for each site were analysed through digital image analysis. Snow particle size variability is complex at different scales, and shows an internal variability of 0.18-3.31 mm depending on the sample type (surface, grid or pit). Relationships were verified between particle size and both elevation and distance to the coast (moisture source). Regional seasonal changes were also identified, particularly on the lower elevations of the polar plateau. This dataset may be used to quantitatively analyse the optical properties of surface snow for remote sensing. The details of the spatial and temporal variations observed in our data provide a basis for further studies of the complex and coupled processes affecting snow particle size and the interpretation of remote sensing of snow covered areas.

  • 23. Isaksen, K
    et al.
    Sollid, JL
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Harris, C
    Recent warming of mountain permafrost in Svalbard and Scandinavia2007In: Journal of Geophysical Research: Earth Surface, Vol. 112, no F2, p. F02S04-Article in journal (Refereed)
    Abstract [en]

    Three deep boreholes (>= 100 m) in mountain permafrost were recently drilled in Svalbard (Janssonhaugen) and in Scandinavia (Tarfalaryggen and Juvvasshoe) for long-term permafrost monitoring. These holes form part of a latitudinal transect of boreholes in permafrost through Europe, established by the Permafrost and Climate in Europe (PACE) project. Six-year thermal time series data collected from the three boreholes are presented. These data provide the first opportunity for temporal trends in permafrost temperatures in Svalbard and Scandinavia to be analyzed. Results show that the permafrost has warmed considerably at all three sites. Significant warming is detectable down to at least 60 m depth, and present decadal warming rates at the permafrost surface are on the order of 0.04 degrees-0.07 degrees C yr(-1), with greatest warming in Svalbard and in northern Scandinavia. The present regional trend shows accelerated warming during the last decade.

  • 24.
    Kirchner, Nina
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography. KTH Royal Institute of Technology, Sweden.
    Noormets, Riko
    Kuttenkeuler, Jakob
    Strandell Erstorp, Elias
    Schytt Holmlund, Erik
    Stockholm University, Faculty of Science, Department of Physical Geography. University Centre in Svalbard, Norway.
    Rosqvist, Gunhild
    Stockholm University, Faculty of Science, Department of Physical Geography. University of Bergen, Norway.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Wennbom, Marika
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Karlin, Torbjörn
    Stockholm University, Faculty of Science, Department of Physical Geography. n.
    High-resolution bathymetric mapping reveals subaqueous glacial landforms in the Arctic alpine lake Tarfala, Sweden2019In: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 34, no 6, p. 452-462Article in journal (Refereed)
    Abstract [en]

    In Arctic alpine regions, glacio-lacustrine environments respond sensitively to variations in climate conditions, impacting, for example,glacier extent and rendering former ice-contact lakes into ice distal lakes and vice versa. Lakefloors may hold morphological records of past glacier extent, but remoteness and long periods of ice cover on such lakes make acquisition of high-resolution bathymetric datasets challenging. Lake Tarfala and Kebnepakte Glacier, located in the Kebnekaise mountains, northern Sweden, comprise a small, dynamic glacio-lacustrine system holding a climate archive that is not well studied. Using an autonomous surface vessel, a high-resolution bathymetric dataset for Lake Tarfala was acquired in 2016, from which previously undiscovered end moraines and a potential grounding line feature were identified. For Kebnepakte Glacier, structure-from-motion photogrammetry was used to reconstruct its shape from photographs taken in 1910 and 1945. Combining these methods connects the glacial landform record identified at the lakefloor with the centennial-scale dynamic behaviour of Kebnepakte Glacier. During its maximum 20(th) century extent, attained c. 1910, Kebnepakte Glacier reached far into Lake Tarfala, but had retreated onto land by 1945, at an average of 7.9 m year(-1).

  • 25.
    Koblet, Thomas
    et al.
    Department of Geography, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
    Gärtner-Roer, Ingrid
    Department of Geography, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
    Zemp, Michael
    Department of Geography, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Thee, Patrick
    Swiss Federal Institute for Forest, Snow and Landscape Research, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.
    Haeberli, Wilfried
    Department of Geography, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Reanalysis of multi-temporal aerial images of Storglaciären, Sweden (1959–99) – Part 1: Determination of length, area, and volume changes2010In: The Cryosphere, ISSN 1994-0416, Vol. 4, p. 333-343Article in journal (Refereed)
    Abstract [en]

    Storglaciären, located in the Kebnekaise massif in northern Sweden, has a long history of glaciological research. Early photo documentations date back to the late 19th century. Measurements of front position variations and distributed mass balance have been carried out since 1910 and 1945/46, respectively. In addition to these in-situ measurements, aerial photographs have been taken at decadal intervals since the beginning of the mass balance monitoring program and were used to produce topographic glacier maps. Inaccuracies in the maps were a challenge to early attempts to derive glacier volume changes and resulted in major differences when compared to the direct glaciological mass balances. In this study, we reanalyzed dia-positives of the original aerial photographs of 1959, -69, -80, -90 and -99 based on consistent photogrammetric processing. From ther esulting digital elevation models and orthophotos, changes in length, area, and volume of Storglaciären were computed between the survey years, including an assessment of related errors. Between 1959 and 1999, Storglaciären lost an ice volume of 19×106 m3, which corresponds to a cumulative ice thickness loss of 5.69 m and a mean annual loss of 0.14 m. This ice loss resulted largely from a strong volume loss during the period 1959–80 and was partly compensated during the period 1980–99. As a consequence, the glacier shows a strong retreat in the 1960s, a slowing in the 1970s, and pseudo-stationary conditions in the 1980s and 1990s.

  • 26.
    Pettersson, Rickard
    et al.
    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.
    Holmlund, Per
    Cold surface layer thinning on Storglaciären, Sweden, observed by repeated ground penetrating radar surveys2003In: Journal of Geophysical Research, ISSN 0148-0227, Vol. 108, no F1, p. 5.1-5.9Article in journal (Refereed)
    Abstract [en]

    A characteristic feature of ground penetrating radar (GPR) surveys on polythermal glaciers is an internal reflection presumably caused by the cold temperate transition surface (CTS), hence providing a possible tool for mapping thermal structure with high accuracy. Comparison of detailed temperature measurements in bore holes and GPR profiles at 345 MHz and 800 MHz center frequencies on Storglaciären, Sweden, show that the CTS can be detected and mapped with an accuracy of about ±1 m at both frequencies. A comparison between comprehensive GPR surveys of the cold surface layer, separated by 12 years (1989-2001), shows a substantial and complex thinning of the cold layer. An overall decrease of 8.3 m (22% of average thickness) of the CTS depth is much larger than uncertainties in CTS depth determinations. The stability of the cold surface layer depends on the net ice ablation at the surface and the downward migration of CTS. There is no evidence of substantial increased net ablation between the survey dates that could explain the observed thinning. However, small increase in average winter air temperature, a limiting factor for the temperature gradient through the cold surface layer, may provide a partial explanation. The weaker temperature gradient reduces the transport of latent heat from the CTS, thus slowing down its downward migration.

  • 27. Rotschky, G
    et al.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Isaksson, E
    Mulvaney, R
    Oerter, H
    Van Den Broeke, MR
    Winther, JG
    A new surface accumulation map for western Dronning Maud Land, Antarctica, from interpolation of point measurements2007In: Journal of Glaciology, Vol. 53, no 182, p. 385-398Article in journal (Refereed)
    Abstract [en]

    s a result of intensive field activities carried out by several nations over the past 15 years, a set of accumulation measurements for western Dronning Maud Land, Antarctica, was collected, based on firn-core drilling and snow-pit sampling. This new information was supplemented by earlier data taken from the literature, resulting in I I I accumulation values. Using Geographical information Systems software, a first region-wide mean annual snow-accumulation field was derived. in order to define suitable interpolation criteria, the accumulation records were analyzed with respect to their spatial autocorrelation and statistical properties. The resulting accumulation pattern resembles well-known characteristics such as a relatively wet coastal area with a sharp transition to the dry interior, but also reveals complex topographic effects. Furthermore, this work identifies new high-return shallow-drilling sites by uncovering areas of insufficient sampling density.

  • 28. Strelin, Jorge
    et al.
    Cassassa, Gino
    Rosqvist, Gunhild
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Holocene glaciations in the Ema Glacier valley, Monte Sarmiento, Tierra del Fuego2008In: Palaeogeography, Palaeoclimatology, Palaeoecology, Vol. 260, p. 299-314Article in journal (Refereed)
  • 29.
    Sugiyama, Shin
    et al.
    Hokkaido University.
    Enomoto, Hiroyuki
    Kitami Institute of Technology, Japan.
    Fujita, Shuji
    National Institute of Polar Research, Tokyo.
    Fukui, Kotaro
    Tateyama Caldera Sabo Museum, Japan.
    Nakazawa, Fumio
    National Institute of Polar Research, Tokyo.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Dielectric permittivity of snow measured along the route traversed in the Japanese-Swedish Antarctic Expedition 2007/082010In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 51, no 55, p. 9-15Article in journal (Refereed)
  • 30. Sugiyama, Shin
    et al.
    Enomoto, Hiroyuki
    Fujita, Shuji
    Fukui, Kotaro
    Nakazawa, Fumio
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Surdyk, Sylviane
    Snow density along the route traversed by the Japanese Swedish Antarctic expedition 2007/082012In: Journal of Glaciology, ISSN 0022-1430, E-ISSN 1727-5652, Vol. 58, no 209, p. 529-539Article in journal (Refereed)
    Abstract [en]

    During the Japanese-Swedish Antarctic traverse expedition of 2007/08, we measured the surface snow density at 46 locations along the 2800 km long route from Syowa station to Wasa station in East Antarctica. The mean snow density for the upper 1 (or 0.5) m layer varied from 333 to 439 kg m(-3) over a region spanning an elevation range of 365-3800 m a.s.l. The density variations were associated with the elevation of the sampling sites; the density decreased as the elevation increased, moving from the coastal region inland. However, the density was relatively insensitive to the change in elevation along the ridge on the Antarctic plateau between Dome F and Kohnen stations. Because surface wind is weak in this region, irrespective of elevation, the wind speed was suggested to play a key role in the near-surface densification. The results of multiple regression performed on the density using meteorological variables were significantly improved by the inclusion of wind speed as a predictor. The regression analysis yielded a linear dependence between the density and the wind speed, with a coefficient of 13.5 kg m(-3) (m s(-1))(-1). This relationship is nearly three times stronger than a value previously computed from a dataset available in Antarctica. Our data indicate that the wind speed is more important to estimates of the surface snow density in Antarctica than has been previously assumed.

  • 31.
    Zemp, Michael
    et al.
    Department of Geography, University of Zurich.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Gärtner-Roer, Ingrid
    Department of Geography, University of Zurich.
    Koblet, Thomas
    Department of Geography, University of Zurich.
    Thee, Patrick
    Department of Geography, University of Zurich.
    Haeberli, Wilfried
    Department of Geography, University of Zurich.
    Reanalysis of multi-temporal aerial images of Storglaciären, Sweden (1959-1999) – Part 2: Comparison of glaciological and volumetric mass balances2010In: The Cryosphere, Vol. 4, p. 345-357Article in journal (Refereed)
    Abstract [en]

    Seasonal glaciological mass balances have been measured on Storglaciären without interruption since 1945/46. In addition, aerial surveys have been carried out on a decadal basis since the beginning of the observation program. Early studies had used the resulting aerial photographs to produce topographic glacier maps with which the in-situ observations could be verified. However, these maps as well as the derived volume changes are subject to errors which resulted in major differences between the derived volumetric and the glaciological mass balance. As a consequence,the original photographs were re-processed using uniform photogrammetric methods, which resulted in new volumetric mass balances for 1959–69, 1969–80, 1980–90, and 1990–99. We compared these new volumetric mass balances with mass balances obtained by standard glaciological methods including an uncertainty assessment considering all related previous studies. The absolute differences between volumetric and the glaciological mass balances are 0.8 m w.e. for theperiod of 1959–69 and 0.3 m w.e. or less for the other survey periods. These deviations are slightly reduced when considering corrections for systematic uncertainties due to differences in survey dates, reference areas, and internal ablation, whereas internal accumulation systematically increases the mismatch. However, the mean annual differences between glaciological and volumetric mass balance are less than the uncertainty of the in-situ stake reading and stochastic error bars of both data series overlap. Hence, no adjustment of the glaciological data series to the volumetric one is required.

1 - 31 of 31
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