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  • 1.
    Arendt, A
    et al.
    University of Alaska.
    Luthcke, S
    University of Alaska.
    Hock, Regine
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    GRACE Mascon Estimates of Glacier Changes in the St. Elias Mountains: Can Mass Balance Models Explain Recent Trends?2009In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 50, no 50, p. 148-154Article in journal (Refereed)
  • 2. Arendt, Anthony A.
    et al.
    Luthcke, Scott B.
    Hock, Regine
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Glacier changes in Alaska: can mass-balance models explain GRACE mascon trends?2009In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 50, no 50, p. 148-154Article in journal (Refereed)
    Abstract [en]

    Temperature and precipitation data from three weather stations in the St Elias Mountains of Alaska and northwestern Canada were used to drive one-dimensional (1-D) (elevation-dependent) and 0-D degree-day mass-balance models. Model outputs were optimized against a 10 day resolution time series of mass variability during 2003-07 obtained from Gravity Recovery and Climate Experiment (GRACE) mass concentration (mascon) solutions. The models explained 52-60% of the variance in the GRACE time series. Modelled mass variations matched the phase of the GRACE observations, and all optimized model parameters were within the range of values determined from conventional mass-balance and meteorological observations. We describe a framework for selecting appropriate weather stations and mass-balance models to represent glacier variations of large regions. There is potential for extending these calibrated mass-balance models forwards or backwards in time to construct mass-balance time series outside of the GRACE measurement window.

  • 3.
    Bhardwaj, Anshuman
    et al.
    TERI University, New Delhi.
    Sam, Lydia
    Department of Environmental Science, Sharda University.
    Singh, Shaktiman
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Kumar, Ramesh
    Department of Environmental Science, School of Basic Sciences and Research, Sharda University, Greater Noida.
    Automated detection and temporal monitoring of crevasses using remote sensing and their implications for glacier dynamics2016In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 57, no 71, p. 81-91Article in journal (Refereed)
    Abstract [en]

    Detailed studies on temporal changes of crevasses and their linkage with glacier dynamics are scarce in the Himalayan context. Observations of temporally changing surficial crevasse patterns and their orientations are suggestive of the processes that determine seasonal glacier flow characteristics. In the present study, on a Himalayan valley glacier, changing crevasse patterns and orientations were detected and mapped on Landsat 8 images in an automated procedure using the ratio of Thermal Infrared Sensor (TIRS) band 10 to Optical Land Imager (OLI) shortwave infrared (SWIR) band 6. The ratio was capable of mapping even crevasses falling under mountain shadows. Differential GPS observations suggested an average error of 3.65% and root-mean-square error of 6.32m in crevasse lengths. A year-round observation of these crevasses, coupled with field-based surface velocity measurements, provided some interesting interpretations of seasonal glacier dynamics.

  • 4. Bliss, Andrew
    et al.
    Hock, Regine
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Cogley, J. Graham
    A new inventory of mountain glaciers and ice caps for the Antarctic periphery2013In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 54, no 63, p. 191-199Article in journal (Refereed)
    Abstract [en]

    Although the glaciers in the Antarctic periphery make up a large fraction of all mountain glaciers and ice caps on Earth, a detailed glacier inventory of the region is lacking. We compile such an inventory, recording areas, area-altitude distributions, terminus characteristics and volume estimates. Glaciers on the mainland are excluded. The inventory is derived from the Antarctic Digital Database and some manual digitization. We additionally rely on satellite imagery, digital elevation models and a flowshed algorithm to classify ice bodies. We find 1133 ice caps and 1619 mountain glaciers covering a total of 132 867 +/- 6643 km(2). Estimated total volume corresponds to 0.121 +/- 0.010 m sea-level equivalent. Of the total glacier area, 99% drains either into ice shelves (63%) or into the ocean (36%). The inventory will provide a database for glacier mass-balance assessments, modelling and projections, and help to reduce the uncertainties in previous studies.

  • 5. Booth, Adam D.
    et al.
    Mercer, Andrew
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Clark, Roger
    Murray, Tavi
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Axtell, Charlotte
    A comparison of seismic and radar methods to establish the thickness and density of glacier snow cover2013In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 54, no 64, p. 73-82Article in journal (Refereed)
    Abstract [en]

    We show that geophysical methods offer an effective means of quantifying snow thickness and density. Opportunistic (efficient but non-optimized) seismic refraction and ground-penetrating radar (GPR) surveys were performed on Storglaciaren, Sweden, co-located with a snow pit that shows the snowpack to be 1.73 m thick, with density increasing from similar to 120 to similar to 500 kg m(-3) (with a +50 kg m(-3) anomaly between 0.73 and 0.83 m depth). Depths estimated for two detectable GPR reflectors, 0.76 +/- 0.02 and 1.71 +/- 0.03 m, correlate extremely well with ground-truth observations. Refraction seismic predicts an interface at 1.90 +/- 0.31 m depth, with a refraction velocity (3730 +/- 190 m s(-1)) indicative of underlying glacier ice. For density estimates, several standard velocity-density relationships are trialled. In the best case, GPR delivers an excellent density estimate for the upper snow layer (observed = 321 +/- 74 kg m(-3), estimated = 319 +/- 10 kg m(-3)) but overestimates the density of the lower layer by 20%. Refraction seismic delivers a bulk density of 404 +/- 22 kg m(-3) compared with a ground-truth average of 356 +/- 22 kg m(-3). We suggest that geophysical surveys are an effective complement to mass-balance measurements (particularly for controlling estimates of snow thickness between pits) but should always be validated against ground-truth observations.

  • 6.
    Charalampidis, Charalampos
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Geol Survey Denmark & Greenland GEUS, Oster Voldgade 10, DK-1350 Copenhagen K, Denmark.
    van As, Dirk
    Geol Survey Denmark & Greenland GEUS, Oster Voldgade 10, DK-1350 Copenhagen K, Denmark.
    Colgan, William T.
    Geol Survey Denmark & Greenland GEUS, Oster Voldgade 10, DK-1350 Copenhagen K, Denmark.; York Univ, Dept Earth & Space Sci & Engn, 4700 Keele St, Toronto, ON M3J 1P3, Canada.
    Fausto, Robert S.
    Geol Survey Denmark & Greenland GEUS, Oster Voldgade 10, DK-1350 Copenhagen K, Denmark.
    MacFerrin, Michael
    Univ Colorado, CIRES, 216 UCB, Boulder, CO 80309 USA.
    Machguth, Horst
    Geol Survey Denmark & Greenland GEUS, Oster Voldgade 10, DK-1350 Copenhagen K, Denmark.; Tech Univ Denmark, Arctic Technol Ctr ARTEK, Byg 118, DK-2800 Lyngby, Denmark.
    Thermal tracing of retained meltwater in the lower accumulation area of the Southwestern Greenland ice sheet2016In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 57, no 72, p. 1-10, article id 6000021Article in journal (Refereed)
    Abstract [en]

    We present in situ firn temperatures from the extreme 2012 melt season in the southwestern lower accumulation area of the Greenland ice sheet. The upper 2.5 m of snow and firn was temperate during the melt season, when vertical meltwater percolation was inefficient due to a c. 5.5 m thick ice layer underlying the temperate firn. Meltwater percolation and refreezing beneath 2.5 m depth only occurred after the melt season. Deviations from temperatures predicted by pure conductivity suggest that meltwater refroze in discrete bands at depths of 2.0–2.5, 5.0–6.0 and 8.0–9.0 m. While we find no indication of meltwater percolation below 9 m depth or complete filling of pore volume above, firn at 10 and 15 m depth was respectively 4.2–4.5 degrees C and 1.7 degrees C higher than in a conductivity-only simulation. Even though meltwater percolation in 2012 was inefficient, firn between 2 and 15 m depth the following winter was on average 4.7 degrees C warmer due to meltwater refreezing. Our observations also suggest that the 2012 firn conditions were preconditioned by two warm summers and ice layer formation in 2010 and 2011. Overall, firn temperatures during the years 2009–13 increased by 0.6 degrees C.

  • 7.
    Dahlke, Helen E.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Early melt season snowpack isotopic evolution in the Tarfala valley, northern Sweden2013In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 54, no 62, p. 149-156Article in journal (Refereed)
    Abstract [en]

    This study investigated the stable water isotopic (delta O-18 and delta D) evolution of two snowpacks located at the same elevation on a north-facing (Nf) and a south-facing (Sf) slope within the Tarfala research catchment, northern Sweden, and the potential impact of pre-freshet snowpack melt on streamflow. Our results indicate that over the study period the Sf snowpack showed a more enriched isotopic composition, especially in the top of the profile, and contributed more snowmelt to streamflow than the Nf slope. The Sf snowpack also showed a significantly higher variability in snowpack delta O-18 levels and snowpack snow water equivalent (SWE) over time. Comparing snowpack and snowmelt isotopic values it was seen that the Sf slope experienced earlier snowmelt from upslope positions due to greater insolation that subsequently enhanced the meltwater flux at the base of downslope snowpacks. In contrast, the Nf slope primarily underwent changes within the snowpack and experienced relatively minimal melt. Detailed field-based isotopic snowmelt studies such as this highlight the potential importance of incorporating spatio-temporal runoff generation concepts into distributed energy-balance models, which could allow for more accurate prediction with regard to the spatio-temporal dynamics associated with the snowmelt ion pulse.

  • 8.
    Fisher, D. A.
    et al.
    Geological Survey of Canada .
    Koerner, R. M.
    Geological Survey of Canada .
    Zielinski, G. A.
    University of New Hampshire.
    Wake, C. P.
    University of New Hampshire.
    Zdanowicz, Christian
    Geological Survey of Canada.
    Bourgeois, J. C.
    Geological Survey of Canada.
    Mayewski, P. A.
    University of New Hampshire.
    Grummet, N.
    University of New Hampshire.
    The effects of flowline length evolution on chemistry - δ18O profiles from Penny Ice Cap, Baffin Island, Canada2002In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 35, no 1, p. 150-156Article in journal (Refereed)
    Abstract [en]

    The isotopic and chemical signatures for ice-age and Holocene ice from Summit, Greenland, and Penny Ice Cap, Baffin Island, Canada, are compared. The usual pattern of low δ180, high Ca2+ and high Cl- is presented in the Summit records, but Penny Ice Cap has lower than present Cl- in its ice-age ice. A simple extension of the Hansson model (Hansson, 1994) is developed and used to simulate these signatures. The low ice­ age Cl- from Penny Ice Cap is explained by having the ice-age ice originating many thou­sands of km inland near the centre of the Laurentide ice sheet and much further from the marine sources. Summit's flowlines all start close to the present site. The Penny Ice Cap early-Holocene δ180's had to be corrected to offset the Laurentide meltwater distortion.The analysis suggests that presently the Summit and Penny Ice Cap marine impurity ori­ ginates about 500 km away, and that presently Penny Ice Cap receives a significant amountoflocal continental impurity.

  • 9.
    Fransson, Agneta
    et al.
    Norwegian Polar Res Inst, Fram Ctr, Tromso, Norway.;Univ Gothenburg, Dept Earth Sci, Gothenburg, Sweden..
    Chierici, Melissa
    Univ Gothenburg, Dept Chem & Mol Biol, Gothenburg, Sweden.;Inst Marine Res, Tromso, Norway..
    Abrahamsson, Katarina
    Univ Gothenburg, Dept Chem & Mol Biol, Gothenburg, Sweden..
    Andersson, Maria
    Univ Gothenburg, Dept Chem & Mol Biol, Gothenburg, Sweden..
    Granfors, Anna
    Univ Gothenburg, Dept Chem & Mol Biol, Gothenburg, Sweden..
    Gårdfeldt, Katarina
    Univ Gothenburg, Chalmers Univ Technol, Ctr Environm & Sustainabil, Gothenburg, Sweden..
    Torstensson, Anders
    Univ Gothenburg, Dept Biol & Environm Sci, Gothenburg, Sweden..
    Wulff, Angela
    Univ Gothenburg, Dept Biol & Environm Sci, Gothenburg, Sweden..
    CO2-system development in young sea ice and CO2 gas exchange at the ice/air interface mediated by brine and frost flowers in Kongsfjorden, Spitsbergen2015In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 56, no 69, p. 245-257Article in journal (Refereed)
    Abstract [en]

    In March and April 2010, we investigated the development of young landfast sea ice in Kongsfjorden, Spitsbergen, Svalbard. We sampled the vertical column, including sea ice, brine, frost flowers and sea water, to determine the CO2 system, nutrients, salinity and bacterial and ice algae production during a 13 day interval of ice growth. Apart from the changes due to salinity and brine rejection, the sea-ice concentrations of total inorganic carbon (C-T), total alkalinity (A(T)), CO2 and carbonate ions (CO32-) in melted ice were influenced by dissolution of calcium carbonate (CaCO3) precipitates (25-55 mu mol kg(-1)) and played the largest role in the changes to the CO2 system. The C-T values were also influenced by CO2 gas flux, bacterial carbon production and primary production, which had a small impact on the C-T. The only exception was the uppermost ice layer. In the top 0.05 m of the ice, there was a CO2 loss of similar to 20 mu mol kg(-1) melted ice (1 mmol m(-2)) from the ice to the atmosphere. Frost flowers on newly formed sea ice were important in promoting ice-air CO2 gas flux, causing a CO2 loss to the atmosphere of 140-800 mu mol kg(-1) d(-1) melted frost flowers (7-40 mmol m(-2)d(-1)).

  • 10. Gusmeroli, Alessio
    et al.
    Murray, Tavi
    Clark, Roger A.
    Kulessa, Bernd
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Vertical seismic profiling of glaciers: appraising multi-phase mixing models2013In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 54, no 64, p. 115-123Article in journal (Refereed)
    Abstract [en]

    We have investigated the speed of compressional waves in a polythermal glacier by, first, predicting them from a simple three-phase (ice, air, water) model derived from a published ground-penetrating radar study, and then comparing them with field data from four orthogonally orientated walkaway vertical seismic profiles (VSPs) acquired in an 80 m deep borehole drilled in the ablation area of Storglaciaren, northern Sweden. The model predicts that the P-wave speed increases gradually with depth from 3700 m s(-1) at the surface to 3760 m s(-1) at 80 m depth, and this change is almost wholly caused by a reduction in air content from 3% at the surface to <0.5% at depth. Changes in P-wave speed due to water content variations are small (<10 m s(-1)); the model's seismic cold-temperate transition surface (CTS) is characterized by a 0.3% decrease downwards in P-wave speed (about ten times smaller than the radar CTS). This lack of sensitivity, and the small contrast at the CTS, makes seismically derived water content estimation very challenging. Nevertheless, for down-going direct-wave first arrivals for zero- and near-offset VSP shots, we find that the model-predicted travel times and field observations agree to within 0.2 ms, i.e. less than the observational uncertainties.

  • 11.
    Harrison, W.
    et al.
    University of Alaska.
    Cox, L.
    University of Montana.
    Hock, Regine
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Petit, E.C.
    Implications for the dynamic health of a glacier from comparison of conventional and reference-surface balances2009In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 50, no 50, p. 25-30Article in journal (Refereed)
    Abstract [en]

    Conventional and reference-surface mass-balance data from Gulkana and Wolverine Glaciers, Alaska, USA, are used to address the questions of how rapidly these glaciers are adjusting (or 'responding') to climate, whether their responses are stable, and whether the glaciers are likely to survive in today's climate. Instability means that a glacier will eventually vanish, or at least become greatly reduced in volume, if the climate stabilizes at its present state. A simple non-linear theory of response is presented for the analysis. The response of Gulkana Glacier is characterized by a timescale of several decades, but its stability and therefore its survival in today's climate are uncertain. Wolverine seems to be responding to climate more slowly, on the timescale of one to several centuries. Its stability is also uncertain, but a slower response time would make it more susceptible to climate changes.

  • 12.
    Hedfors, Jim
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Environment and Landscape Dynamics.
    Pohjola, Veijo
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Environment and Landscape Dynamics.
    Ice flux of Plogbreen, a small ice stream in Dronning Maud Land, Antarctica2004In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 39, no 1, p. 409-416Article in journal (Refereed)
    Abstract [en]

    As part of a long-term mass-balance program run by SWEDARP since 1988, a detailed study on Plogbreen, Dronning Maud Land, Antarctica, was undertaken during the austral summer of 2003 to investigate the long-term mass balance. We compare ice outflux, out, through a cross-sectional gate with ice influx, in, from the upstream catchment area. The in is based on calculations of snow accumulation upstream of the gate using data available from published ice-core records. The out is based on Glen's flow law aided by thermodynamic modeling and force-budget calculations. Input data from the field consist of measurements of ice surface velocity and ice geometry. The ice surface velocity was measured using repeated differential global positioning system surveying of 40 stakes over a period of 25 days. The ice geometry was determined by 174 km of ground-penetrating radar profiling using ground-based 8 MHz dipole antennas. This study presents the collected velocity and geometry data as well as the calculated ice flux of Plogbreen. The results show a negatively balanced system within the uncertainty limits; out = 0.55 ± 0.05 km3 a−1 and in = 0.4 ± 0.1 km3 a−1. We speculate that the negative balance can be explained by recent eustatic increase reducing resistive stresses and inducing accelerated flow.

  • 13.
    How, Penelope
    et al.
    Univ Edinburgh, Sch GeoSci, Inst Geog, Edinburgh, Midlothian, Scotland;Univ Ctr Svalbard, Dept Arctic Geol, Longyearbyen, Norway;Univ York, Dept Environm & Geog, York, N Yorkshire, England.
    Schild, Kristin M.
    Univ Oregon, Dept Earth Sci, Eugene, OR 97403 USA;Univ Maine, Climate Change Inst, Orono, ME USA.
    Benn, Douglas I.
    Univ St Andrews, Dept Geog & Sustainable Dev, St Andrews, Fife, Scotland.
    Noormets, Riko
    Univ Ctr Svalbard, Dept Arctic Geol, Longyearbyen, Norway.
    Kirchner, Nina
    Stockholm Univ, Dept Phys Geog, Stockholm, Sweden.
    Luckman, Adrian
    Swansea Univ, Dept Geog, Coll Sci, Swansea, W Glam, Wales;Univ Ctr Svalbard, Dept Arctic Geophys, Longyearbyen, Norway.
    Vallot, Dorothée
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Hulton, Nicholas R. J.
    Univ Edinburgh, Sch GeoSci, Inst Geog, Edinburgh, Midlothian, Scotland;Univ Ctr Svalbard, Dept Arctic Geol, Longyearbyen, Norway.
    Borstad, Chris
    Univ Ctr Svalbard, Dept Arctic Geophys, Longyearbyen, Norway.
    Calving controlled by melt-under-cutting: detailed calving styles revealed through time-lapse observations2019In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 60, no 78, p. 20-31Article in journal (Refereed)
    Abstract [en]

    We present a highly detailed study of calving dynamics at Tunabreen, a tidewater glacier in Svalbard. A time-lapse camera was trained on the terminus and programmed to capture images every 3 seconds over a 28-hour period in August 2015, producing a highly detailed record of 34 117 images from which 358 individual calving events were distinguished. Calving activity is characterised by frequent events (12.8 events h(-1)) that are small relative to the spectrum of calving events observed, demonstrating the prevalence of small-scale calving mechanisms. Five calving styles were observed, with a high proportion of calving events (82%) originating at, or above, the waterline. The tidal cycle plays a key role in the timing of calving events, with 68% occurring on the falling limb of the tide. Calving activity is concentrated where meltwater plumes surface at the glacier front, and a similar to 5 m undercut at the base of the glacier suggests that meltwater plumes encourage melt-under-cutting. We conclude that frontal ablation at Tunabreen may be paced by submarine melt rates, as suggested from similar observations at glaciers in Svalbard and Alaska. Using submarine melt rate to calculate frontal ablation would greatly simplify estimations of tidewater glacier losses in prognostic models.

  • 14. How, Penelope
    et al.
    Schild, Kristin M.
    Benn, Douglas I.
    Noormets, Riko
    Kirchner, Nina
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Luckman, Adrian
    Vallot, Dorothée
    Hulton, Nicholas R. J.
    Borstad, Chris
    Calving controlled by melt-under-cutting: detailed calving styles revealed through time-lapse observations2019In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 60, no 78, p. 20-31Article in journal (Refereed)
    Abstract [en]

    We present a highly detailed study of calving dynamics at Tunabreen, a tidewater glacier in Svalbard. A time-lapse camera was trained on the terminus and programmed to capture images every 3 seconds over a 28-hour period in August 2015, producing a highly detailed record of 34 117 images from which 358 individual calving events were distinguished. Calving activity is characterised by frequent events (12.8 events h(-1)) that are small relative to the spectrum of calving events observed, demonstrating the prevalence of small-scale calving mechanisms. Five calving styles were observed, with a high proportion of calving events (82%) originating at, or above, the waterline. The tidal cycle plays a key role in the timing of calving events, with 68% occurring on the falling limb of the tide. Calving activity is concentrated where meltwater plumes surface at the glacier front, and a similar to 5 m undercut at the base of the glacier suggests that meltwater plumes encourage melt-under-cutting. We conclude that frontal ablation at Tunabreen may be paced by submarine melt rates, as suggested from similar observations at glaciers in Svalbard and Alaska. Using submarine melt rate to calculate frontal ablation would greatly simplify estimations of tidewater glacier losses in prognostic models.

  • 15. Hulth, John
    et al.
    Rolstad Denby, Cecilie
    Hock, Regine
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Estimating glacier snow accumulation from backward calculation of melt and snowline tracking2013In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 54, no 62, p. 1-7Article in journal (Refereed)
    Abstract [en]

    Estimating precipitation to determine accumulation is challenging. We present a method that combines melt modelling and snowline tracking to determine winter glacier snow accumulation along snowlines. The method assumes that the net accumulation is zero on the transient snowlines and the maximum winter accumulation at the snowline can be calculated backwards with a temperature-index melt model. To verify the method, the accumulation model is applied for the year 2004 on Storglaciaren, Sweden, for which extensive meteorological and mass-balance data are available. The measured mean snowline accumulation is 0.94 +/- 0.10 m w.e. for 2004. Modelled accumulation, using backward melt modelling, at the same snowlines is 0.82 +/- 0.25 m w.e. The accumulation model is also compared with an often used linear regression accumulation model which yields a mean snowline accumulation of 1.02 +/- 0.38 m w.e. The reduction in standard error from 0.38 m w.e. to 0.25 m w.e. shows that the backward melt modelling applied at snowlines can provide a better spatial representation of the accumulation pattern than the regression model. Importantly, the applied method requires no field measurements of accumulation during the winter and snowlines can be readily traced in remotely sensed images.

  • 16.
    Ingvander, Susanne
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Dahlke, Helen E.
    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.
    Surdyk, Sylviane
    In situ sampled snow particle sizes of the East Antarctic ice sheet and their relation to physical and remotely sensed snow surface parameters2013In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 54, no 62, p. 166-174Article in journal (Refereed)
    Abstract [en]

    Knowledge of snow properties across Antarctica is important in estimating how climate could potentially influence the mass balance of the Antarctic ice sheet. However, measuring these variables has proven to be challenging because appropriate techniques have not yet been developed and extensive datasets of field estimates are lacking. The goal of this study was to estimate the relationship between field-observed snow particle-size parameters from across the East Antarctic ice sheet and a suite of spatial datasets (i.e. topography, remote-sensing data) using a principal component analysis (PCA). Five snow particle-size parameters were correlated to spatial datasets of the following five groups: (1) relief properties such as elevation and slope; (2) remote-sensing data from Moderate Resolution Imaging Spectroradiometer (MODIS) and synthetic aperture radar (SAR) sensors; (3) spatially interpolated data (i.e. 10 m maps of temperature and approximate snow accumulation in kg m(-2) a(-1)); (4) field-retrieved data on surface roughness; and (5) in situ elevation and distance from the coast. The results show that the relief parameter slope correlated best with the snow particle length and area (r=0.76, r=0.80). Further, the PCA indicated that the different remote-sensing parameters correlated differently with the size parameters and that the most common parameter in visual analysis, particle length (grain diameter), is not always the optimal parameter to characterize the snow particle size as, for example, area correlates better to slope and aspect than length.

  • 17.
    Ingvander, Susanne
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Rosqvist, Gunhild
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Svensson, Jonas
    Dahlke, Helen E.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Seasonal and interannual variability of elemental carbon in the snowpack of Storglaciaren, northern Sweden2013In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 54, no 62, p. 50-58Article in journal (Refereed)
    Abstract [en]

    We studied the variability of elemental carbon (EC) over 3 years (2009-11) in the winter snowpack of Storglaciaren, Sweden. The goal of this study was to relate the seasonal variation in EC to specific snow accumulation events in order to improve understanding of how different atmospheric circulation patterns control the deposition of EC. Specifically, we related meteorological parameters (e.g. wind direction, precipitation) to snow physical properties, EC content, stable-isotope 8180 ratios and anion concentrations in the snowpack. The distribution of EC in the snowpack varied between years. Low EC contents corresponded to a predominance of weather systems originating in the northwest, i.e. North Atlantic. Analysis of single layers within the snowpacks showed that snow layers enriched in heavy isotopes coincided predominantly with low EC contents but high chloride and sulfate concentration. Based on this isotopic and geochemical evidence, snow deposited during these events had a strong oceanic, i.e. North Atlantic, imprint. In contrast, snow layers with high EC content coincided with snow layers depleted in heavy isotopes but high anion concentrations, indicating a more continental source of air masses and origin of EC from industrial emissions.

  • 18. Jacobel, Robert W.
    et al.
    Welch, Brian C.
    Osterhouse, David
    Pettersson, Rickard
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    MacGregor, Joseph A.
    Spatial variation of radar-derived basal conditions on Kamb Ice Stream, West Antarctica2009In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 50, no 51, p. 10-16Article in journal (Refereed)
    Abstract [en]

    Radar profiles of bed echo intensity can survey conditions at the ice-bed interface and test for the presence or absence of water. However, extracting information about basal conditions from bed echo intensities requires an estimate of the attenuation loss through the ice. We used the relationship between bed echo intensities from constant-offset radar data and ice thickness to estimate depth-averaged attenuation rates at several locations on and near Kamb Ice Stream (KIS), West Antarctica. We found values varying from 29 dB km−1 at Siple Dome to 15 dB km−1 in the main trunk region of KIS, in agreement with a previous measurement and models. Using these attenuation-rate values, we calculated the relative bed reflectivity throughout our KIS surveys and found that most of the bed in the trunk has high basal reflectivities, similar to those obtained in the location of boreholes that found water at the bed. Areas of lower bed reflectivity are limited to the sticky spot, where a borehole found a dry bed, and along the margins of KIS. These results support previous hypotheses that the basal conditions at locations like the sticky spot on KIS control its stagnation and possible reactivation.

  • 19. Jansson, Peter
    et al.
    Linderholm, Hans
    Pettersson, Rickard
    Karlin, Torbjörn
    Mörth, Carl-Magnus
    Assessing the possibility to couple the chemical signal in winter snow on Storglaciären to atmospheric climatology2007In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 46, no 1, p. 335-341Article in journal (Refereed)
    Abstract [en]

    Winter accumulation on glaciers in temperate to sub-arctic climate regimes is determined by both precipitation and snowdrifting during repeated events during any particular winter. Since glacier mass balance is calculated from the sum of winter and summer balance, and summer balance can be modeled with high accuracy, identification of the coupling between atmospheric circulation and winter balance is essential in order to fully understand the climate information hidden in the glacier mass-balance records. We have sampled snow cores from Storglaciären, Sweden, to examine identifiable chemical signatures to link these with up-wind sources in an attempt to quantify how much accumulation occurs under given atmospheric conditions. The snow samples reveal that several different chemical signatures occur but that identifying their source is not trivial, although only few but distinct sources exist. The relationship between the identified strata of a given signature is difficult to couple to recorded precipitation events because the crucial timing of deposition is lacking in our investigation. If time control on snow deposition is available, the combination of snow chemistry, meteorological and climatological data is a promising tool for evaluating the coupling between snow accumulation and atmospheric circulation.

  • 20.
    Jónsdóttir, Kristín
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Tryggvason, Ari
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Roberts, Roland
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Lund, Björn
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Soosalu, H.
    Bödvarsson, Reynir
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Geophysics.
    Habits of a glacier-covered volcano: Seismicity patterns and velocity structure of Katla volcano, Iceland2007In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 45, p. 169-177Article in journal (Refereed)
    Abstract [en]

    The Katla volcano, overlain by the Mýrdalsjökull glacier, is one of the most active and hazardous volcanoes in Iceland. Earthquakes show anomalous magnitude-frequency behaviour and mainly occur in two distinct areas: within the oval caldera and around Goðabunga, a bulge on its western flank. The seismicity differs between the areas; earthquakes in Goðabunga are low frequency and shallow whereas those beneath the caldera occur at greater depths and are volcano-tectonic. The seismicity shows seasonal variations but the rates peak at different times in the two areas. A snow budget model, which gives an estimate of the glacial loading, shows good correlation with seismic activity on an annual scale. Data recorded by the permanent network South Iceland Lowland (SIL), as well as by a temporary network, are used to invert for a 3D seismic velocity model underneath Eyjafjallajökull, Goðabunga and the Katla caldera. The tomography resolves a 15 km wide, aseismic, high-velocity structure at a depth of more than 4 km between the Eyjafjallajökull volcano in the west and the Katla volcano in the east. Anomalously low velocities are observed beneath the Katla caldera, which is interpreted as being a significantly fractured area of anomalously high temperature.

  • 21. Keller, T
    et al.
    Pielmeier, C
    Rixen, C
    Gadient, F
    Gustafsson, David
    Stähli, M
    Impact of artificial snow and ski slope grooming on the snow pack properties and the soil thermal regime in a sub-alpine area2004In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 38, p. 314-318Article in journal (Refereed)
    Abstract [en]

    Studies have indicated that the soil on groomed ski slopes may be subjected to more pronounced cooling than the soil below a natural snowpack. We analyzed the thermal impacts of ski-slope preparation in a sub-alpine ski resort in central Switzerland (1100 in a.s.l.) where artificial snow was produced. Physical snow properties and soil temperature measurements were carried out on the ski slope and off-piste during winter 1999/2000. The numerical soil-vegetation-atmosphere transfer model COUP was run for both locations, with a new option to simulate the snowpack development on a groomed ski slope. Snow density. snow hardness and thermal conductivity were significantly higher on the ski slope than in the natural snowpack. However, these differences did rift affect the cooling of the soil, since no difference was observed between the ski slope and the natural snow cover. This might be because cold periods were rare and short and thus any snowpack could protect the soil from freezing. The major impact of the ski-slope grooming was a 4 week delay in snowmelt and soil warming at the end of the season. The newly implemented option proved to be a useful strategy for simulating the snowpack of a ski slope. However, snow density was underestimated by the model as it could not account adequately for compaction due to grooming traffic. Our study demonstrates that there is no site-independent answer as to whether a groomed snowpack affects the thermal conditions in the soil.

  • 22. Killingbeck, Siobhan F.
    et al.
    Booth, Adam D.
    Livermore, Philip W.
    West, Landis J.
    Reinardy, Benedict T.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Nesje, Atle
    Subglacial sediment distribution from constrained seismic inversion, using MuLTI software: examples from Midtdalsbreen, Norway2019In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 60, no 79, p. 206-219Article in journal (Refereed)
    Abstract [en]

    Fast ice flow is associated with the deformation of subglacial sediment. Seismic shear velocities, Vs, increase with the rigidity of material and hence can be used to distinguish soft sediment from hard bedrock substrates. Depth profiles of Vs can be obtained from inversions of Rayleigh wave dispersion curves, from passive or active-sources, but these can be highly ambiguous and lack depth sensitivity. Our novel Bayesian transdimensional algorithm, MuLTI, circumvents these issues by adding independent depth constraints to the inversion, also allowing comprehensive uncertainty analysis. We apply MuLTI to the inversion of a Rayleigh wave dataset, acquired using active-source (Multichannel Analysis of Surface Waves) techniques, to characterise sediment distribution beneath the frontal margin of Midtdalsbreen, an outlet of Norway's Hardangerjokulen ice cap. Ice thickness (0-20 m) is constrained using co-located GPR data. Outputs from MuLTI suggest that partly-frozen sediment (Vs 500-1000 m s(-1)), overlying bedrock (Vs 2000-2500 m s(-1)), is present in patches with a thickness of similar to 4 m, although this approaches the resolvable limit of our Rayleigh wave frequencies (14-100 Hz). Uncertainties immediately beneath the glacier bed are <280 m s(-1), implying that MuLTI cannot only distinguish bedrock and sediment substrates but does so with an accuracy sufficient for resolving variations in sediment properties.

  • 23.
    Köhler, Andreas
    et al.
    Department of Geosciences, University of Oslo, Post Box 1047, 0316 Oslo, Norway ; NORSAR, 2007 Kjeller, Norway.
    Maupin, Valerie
    Centre for Earth Evolution and Dynamics, Department of Geosciences, University of Oslo, Post Box 1028, 0316 Oslo, Norway.
    Nuth, Christopher
    Department of Geosciences, University of Oslo, Post Box 1047, 0316 Oslo, Norway.
    Van Pelt, Ward
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Characterization of seasonal glacial seismicity from a single-station on-ice record at Holtedahlfonna, Svalbard2019In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 60, no 79, p. 23-36Article in journal (Refereed)
    Abstract [en]

    Glacial seismicity provides important insights into glacier dynamic processes. We study the temporal distribution of cryogenic seismic signals (icequakes) at Holtedahlfonna, Svalbard, between April and August 2016 using a single three-component sensor. We investigate sources of observed icequakes using polarization analysis and waveform modeling. Processes responsible for five icequake categories are suggested, incorporating observations of previous studies into our interpretation. We infer that the most dominant icequake type is generated by surface crevasse opening through hydrofracturing. Secondly, bursts of high-frequency signals are presumably caused by repeated near-surface crevassing due to high strain rates during glacier fast-flow episodes. Furthermore, signals related to resonance in water-filled cracks, fracturing or settling events in dry firn or snow before the melt season, and processes at the glacier bed are observed. Amplitude of seismic background noise is clearly related to glacier runoff. We process ambient seismic noise to invert horizontal-to-vertical spectral ratios for a sub-surface seismic velocity model used to model icequake signals. Our study shows that a single seismic sensor provides useful information about seasonal ice dynamics in case deployment of a network is not feasible.

  • 24.
    Moore, John C
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Jevrejeva, S.
    Grinsted, A.
    The historical global sea level budget2011In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 52, no 59, p. 8-14Article in journal (Refereed)
    Abstract [en]

    We analyze the global sea-level budget since 1850. Good estimates of sea-level contributions from glaciers and small ice caps, the Greenland ice sheet and thermosteric sea level are available over this period, though considerable scope for controversy remains in all. Attempting to close the sea-level budget by adding the components results in a residual displaying a likely significant trend of 0.37 mm a-1 from 1955 to 2005, which can, however, be reasonably closed using estimated melting from unsurveyed high-latitude small glaciers and ice caps. The sea-level budget from 1850 is estimated using modeled thermosteric sea level and inferences from a small number of mountain glaciers. This longer-term budget has a residual component that displays a rising trend likely associated with the end of the Little Ice Age, with much decadal-scale variability that is probably associated with variability in the global water cycle, ENSO and long-term volcanic impacts.

  • 25.
    Mortin, Jonas
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Howell, Stephen E. L.
    Climate Research Division, Environment Canada.
    Derksen, Chris
    Climate Research Division, Environment Canada.
    Wang, Libo
    Climate Research Division, Environment Canada.
    Svensson, Gunilla
    Stockholm University, Faculty of Science, Department of Meteorology .
    Graversen, Rune G.
    Stockholm University, Faculty of Science, Department of Meteorology .
    OSCAT as a successor to QuikSCAT: a comparison over Arctic sea ice with emphasis on the seasonal melt-freeze transitionsIn: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644Article in journal (Refereed)
    Abstract [en]

    It is important to continuously monitor the seasonal melt-freeze transitions because of their influence on the Arctic climate system. The Ku-band scatterometer QuikSCAT was widely used to retrieve the seasonal transitions before its antenna failed in November 2009. In this study, we show that OSCAT, a Ku-band scatterometer launched in September 2009, can serve as a successor to QuikSCAT over Arctic sea ice. This is done by (1) comparing backscatter measurements acquired in overlapping time periods, and by (2) retrieving the seasonal melt-freeze transitions over Arctic sea ice from resolution-enhanced QuikSCAT and OSCAT data and comparing the results, also with other datasets. The main difference between the instruments, in terms of backscatter measurements, is the incidence angle in which backscatter is acquired, which yields backscatter discrepancies of 1-2 dB. This discrepancy is significantly smaller than the response of both sensors to surface melting and freezing processes. An edge-detection algorithm is employed that retrieves seasonal transitions from QuikSCAT (1999-2009) and OSCAT (2011-2013) at a 4.45-km spatial resolution. A comparison with transitions retrieved from the C-band scatterometer ASCAT (2009-2013) and from passive microwave radiometers (1999-2013) indicates that the transitions from scatterometers are largely consistent across all regions in the Arctic sea-ice domain.

  • 26. Osmanoglu, B.
    et al.
    Braun, M.
    Hock, Regine
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Navarro, F. J.
    Surface velocity and ice discharge of the ice cap on King George Island, Antarctica2013In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 54, no 63, p. 111-119Article in journal (Refereed)
    Abstract [en]

    Glaciers on King George Island, Antarctica, have shown retreat and surface lowering in recent decades, concurrent with increasing air temperatures. A large portion of the glacier perimeter is ocean-terminating, suggesting possible large mass losses due to calving and submarine melting. Here we estimate the ice discharge into the ocean for the King George Island ice cap. L-band synthetic aperture radar images covering the time-span January 2008 to January 2011 over King George Island are processed using an intensity-tracking algorithm to obtain surface velocity measurements. Pixel offsets from 40 pairs of radar images are analysed and inverted to estimate a weighted average surface velocity field. Ice thicknesses are derived from simple principles of ice flow mechanics using the computed surface velocity fields and in situ thickness data. The maximum ice surface speeds reach >225 m a(-1), and the total ice discharge for the analysed flux gates of King George Island is estimated to be 0.720 +/- 0.428 Gt a(-1), corresponding to a specific mass loss of 0.64 +/- 0.38 m w.e. a(-1) over the area of the entire ice cap (1127 km(2)).

  • 27. Ostby, Torbjorn I.
    et al.
    Schuler, Thomas V.
    Hagen, Jon Ove
    Hock, Regine
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Reijmer, Leen H.
    Parameter uncertainty, refreezing and surface energy balance modelling at Austfonna ice cap, Svalbard, 2004-082013In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 54, no 63, p. 229-240Article in journal (Refereed)
    Abstract [en]

    We apply a physically based coupled surface energy balance and snowpack model to a site close to the equilibrium line on Austfonna ice cap, Svalbard, over the 2004-08 melt seasons, to explain contributions to the energy available for melting and to quantify the significance of refreezing. The model is forced using in situ meteorological measurements and precipitation downscaled from ERA-Interim reanalysis. Applying a Monte Carlo approach to determine the tunable parameters of the model, we estimate the uncertainty related to the choice of parameter values. Multiple criteria are evaluated to identify well-performing parameter combinations, evaluating the model performance with respect to longwave outgoing radiation, snow and ice temperatures and surface displacement. On average, over the investigated melt seasons (1 June to 15 September) net radiation and sensible heat contributed 90 +/- 2% and 10 +/- 2%, respectively, to the mean energy available for melting snow and ice. The energy consumed by subsurface heat exchange reduced runoff by 15 +/- 2% in 2004 and 49 +/- 3% in 2008. Refreezing of meltwater and rain was estimated to be 0.37 +/- 0.04 m w.e. a(-1) on average over the five seasons, which represents a considerable reduction of mass loss during summer. Our findings suggest that refreezing potentially exerts a decisive control on glacier mass balance in persistently snow- or firn-covered areas.

  • 28.
    Pohjola, Veijo A
    et al.
    Uppsala universitet, Luft-, vatten och landskapslära.
    Hedfors, Jim
    Uppsala universitet, Miljö- och landskapsdynamik.
    Holmlund, Per
    Investigating the potential to determine the upstream accumulation rate, using mass flux calculations along a cross-section on a small tributary glacier in Heimefrontfjella, Dronning Maud Land, Antarctica2004In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 39, no 1, p. 175-180Article in journal (Refereed)
    Abstract [en]

    How well can we estimate the incoming ice flux by calculating the ice flux through a well-defined cross-section? We test this by comparing calculated ice flux out from the small glacier Bonnevie-Svendsenbreen with the measured accumulation rate integrated over the well-defined catchment area in the Sivorgfjella plateau, Dronning Maud Land, Antarctica (74°45′S, 11°10′W). The ice flux is calculated using ice-dynamical properties from an ice temperature model and the distribution of forces calculated using a force-budget model. The input we use includes velocity data of the glacier surface, combined with ice-thickness measurements. The result is an accumulation rate on the Sivorgfjella plateau of 0.50 ± 0.05 m w.e.a−1. We find that this is similar to the accumulation rate recorded by ground-penetrating radar work in the area. We therefore find the balance-flow method, in combination with the force-budget technique and ice temperature modeling, to be a useful tool for studies of mass fluxes in a catchment area. The most important source of uncertainty in these calculations is the quality and the spatial distribution of the ice surface velocity data. The high accumulation rate shows the effect of orographic enhancement on accumulation in montane areas in Antarctica.

  • 29.
    Pohjola, Veijo A
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Hedfors, Jim
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Environment and Landscape Dynamics. Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL. Miljö- och landskapsdynamik.
    Holmlund, Per
    Investigating the potential to determine the upstream accumulation rate, using mass flux calculations along a cross-section on a small tributary glacier in Heimefrontfjella, Dronning Maud Land, Antarctica2004In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 39, no 1, p. 175-180Article in journal (Refereed)
    Abstract [en]

    How well can we estimate the incoming ice flux by calculating the ice flux through a well-defined cross-section? We test this by comparing calculated ice flux out from the small glacier Bonnevie-Svendsenbreen with the measured accumulation rate integrated over the well-defined catchment area in the Sivorgfjella plateau, Dronning Maud Land, Antarctica (74°45′S, 11°10′W). The ice flux is calculated using ice-dynamical properties from an ice temperature model and the distribution of forces calculated using a force-budget model. The input we use includes velocity data of the glacier surface, combined with ice-thickness measurements. The result is an accumulation rate on the Sivorgfjella plateau of 0.50 ± 0.05 m w.e.a−1. We find that this is similar to the accumulation rate recorded by ground-penetrating radar work in the area. We therefore find the balance-flow method, in combination with the force-budget technique and ice temperature modeling, to be a useful tool for studies of mass fluxes in a catchment area. The most important source of uncertainty in these calculations is the quality and the spatial distribution of the ice surface velocity data. The high accumulation rate shows the effect of orographic enhancement on accumulation in montane areas in Antarctica.

  • 30.
    Radic, Valentina
    et al.
    Department of Physical Geography and Quaternary Geology, Stockholm University, Stockholm, Sweden.
    Hock, Regine
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Air and Water Science.
    Oerlemans, Johannes
    Institute for Marine and Atmospheric Research Utrecht, University of Utrecht, The Netherlands.
    Volume-area scaling vs flowline modelling in glacier volume projections2007In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 46, no 1, p. 234-240Article in journal (Refereed)
    Abstract [en]

    Volume-area scaling provides a practical alternative to ice-flow modelling to account for glacier size changes when modelling future glacier evolutions, however, uncertainties remain as to the validity of the approach under non-steady conditions. We address these uncertainties by deriving scaling exponents in volume-area relationship from one-dimensional ice-flow modelling. We generate a set of 37 synthetic steady-state glaciers of different sizes, and then model volume evolutions due to climate warming and cooling as prescribed by negative and positive mass balance perturbations, respectively, on a century time scale. The scaling exponent derived for the steady-state glaciers (=1.56) differs from the exponents derived from the glaciers in transient (non-steady) state by up to 86%. Nevertheless, volume projections employing volume-area scaling are relatively insensitive to these differences in scaling exponents. Volume-area scaling agrees well with the results from ice-flow modelling and is able to simulate the approach of a glacier to a new steady state, if mass-balance elevation feedback is considered by adding or removing elevation bands at the lowest part of the glacier in response to mass balance variations. Provided area-changes are considered in the mass balance computations in this way, our results indicate that volume-area scaling is a powerful tool for glacier volume projections on multi-century time scales.

  • 31.
    Radic, Valentina
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hock, Regine
    Uppsala University, Department of Earth Sciences)(Uppsala University, Air and Water Science.
    Oerlemans, Johannes
    Institute for Marine and Atmospheric Research Utrecht, University of Utrecht, The Netherlands.
    Volume-area scaling vs flowline modelling in glacier volume projections2007In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 46, p. 234-240Article in journal (Refereed)
    Abstract [en]

    Volume-area scaling provides a practical alternative to ice-flow modelling to account for glacier size changes when modelling future glacier evolutions, however, uncertainties remain as to the validity of the approach under non-steady conditions. We address these uncertainties by deriving scaling exponents in volume-area relationship from one-dimensional ice-flow modelling. We generate a set of 37 synthetic steady-state glaciers of different sizes, and then model volume evolutions due to climate warming and cooling as prescribed by negative and positive mass balance perturbations, respectively, on a century time scale. The scaling exponent derived for the steady-state glaciers (=1.56) differs from the exponents derived from the glaciers in transient (non-steady) state by up to 86%. Nevertheless, volume projections employing volume-area scaling are relatively insensitive to these differences in scaling exponents. Volume-area scaling agrees well with the results from ice-flow modelling and is able to simulate the approach of a glacier to a new steady state, if mass-balance elevation feedback is considered by adding or removing elevation bands at the lowest part of the glacier in response to mass balance variations. Provided area-changes are considered in the mass balance computations in this way, our results indicate that volume-area scaling is a powerful tool for glacier volume projections on multi-century time scales.

  • 32. Schannwell, Clemens
    et al.
    Murray, Tavi
    Kulessa, Bernd
    Gusmeroli, Alessio
    Saintenoy, Albane
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    An automatic approach to delineate the cold-temperate transition surface with ground-penetrating radar on polythermal glaciers2014In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 55, no 67, p. 89-96Article in journal (Refereed)
    Abstract [en]

    Ground-penetrating radar has been widely used to map the thermal structure of polythermal glaciers. Hitherto, the cold temperate transition surface (CTS) in radargrams has been identified by a labour-intensive and subjective manual picking method. We introduce a new automatic approach for picking the CTS that uses the difference in signal power exhibited by the cold and temperate ice layers. We compare our automatically computed CTS depths with manual picks. Our results show very good agreement between the two methods in most areas (r(2) > 0.7). RMSEs computed at each trace in two-way travel-time from three test sites range from 14 to 19 ns (2.4-3.2 m). The proposed automated method mostly fails in areas showing a rather gradual transition in signal power at the CTS. In some areas, high power originating from non-water sources is misinterpreted by the automatic picking method as 'temperate ice'.

  • 33. Stähli, M.
    et al.
    Stacheder, M.
    Gustafsson, David
    WSL Swiss Fed. Inst. Snow/Avalanche, Flüelastrasse, Switzerland.
    Schlaeger, S.
    Schneebeli, M.
    Brandelik, A.
    A new in-situ sensor for large-scale snow cover monitoring2004In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 38, p. 273-278Article in journal (Refereed)
    Abstract [en]

    A new in situ sensor for the simultaneous measurement of snow water equivalent, snow density and liquid-water content is presented in this paper. The system consists of radio frequency transmission lines of up to 25 in length cast in a flat PVC band, which can be set up either horizontally to monitor single snow-layer properties or sloping from a mast to the soil surface to determine vertical snowpack properties. The dielectric coefficient along the flat-band cable is measured with a time-domain reflectometer at high frequencies, and with a low-frequency impedance analyzer. The performance of the sensor system was tested during two winter seasons (2001-03) at the high-alpine test site Weissfluhjoch, Davos, Switzerland. The cable suspension and set-up of the sloping cable was shown to be critical with regard to stability and the formation of unwanted air gaps along the cable. Overall, the sensing system proved quite robust and produced results in agreement with manual snowpack observations.

  • 34. Sugiyama, S.
    et al.
    Enomoto, H.
    Fujita, S.
    Fukui, K.
    Nakazawa, F.
    Holmlund, P.
    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. 51Article in journal (Refereed)
    Abstract [en]

    As a joint contribution of Japan and Sweden to the International Polar Year 2007-09, a field expedition between Syowa and Wasa stations in East Antarctica was carried out in the 2007/08 austral summer season. Along the 2800 km long expedition route, the dielectric permittivity of the upper 1 m snow layer was measured at intervals of approximately 50 km using a snow fork, a parallel-wire transmission-line resonator. More than 2000 measurements were performed under carefully calibrated conditions, mostly in the interior of Antarctica. The permittivity epsilon' was a function of snow density as in previous studies on dry snow, but the values were significantly smaller than those reported before. In the light of the dielectric mixture theory, the relatively smaller e' obtained in this study can be attributed to the snow structures characteristic in the studied region. Our data suggest that the permittivity of snow in the Antarctic interior is significantly affected by weak bonding between snow grains, which is due to depth-hoar formation in the extremely low-temperature conditions.

  • 35.
    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)
  • 36. Wilhelms, Frank
    et al.
    Miller, Heinrich
    Gerasimoff, Michael D.
    Druecker, Cord
    Frenzel, Andreas
    Fritzsche, Diedrich
    Grobe, Hannes
    Hansen, Steffen Bo
    Hilmarsson, Sverrir A. E.
    Hoffmann, Georg
    Hörnby, Kerstin
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jaeschke, Andrea
    Jakobsdottir, Steinunn S.
    Juckschat, Paul
    Karsten, Achim
    Karsten, Lorenz
    Kaufmann, Patrik R.
    Karlin, Torbjorn
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kohlberg, Eberhard
    Kleffel, Guido
    Lambrecht, Anja
    Lambrecht, Astrid
    Lawer, Gunther
    Schaermeli, Ivan
    Schmitt, Jochen
    Sheldon, Simon G.
    Takata, Morimasa
    Trenke, Marcus
    Twarloh, Birthe
    Valero-Delgado, Fernando
    Wilhelms-Dick, Dorothee
    The EPICA Dronning Maud Land deep drilling operation2014In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 55, no 68, p. 355-366Article in journal (Refereed)
    Abstract [en]

    We report on the EPICA Dronning Maud Land (East Antarctica) deep drilling operation. Starting with the scientific questions that led to the outline of the EPICA project, we introduce the setting of sister drillings at NorthGRIP and EPICA Dome C within the European ice-coring community. The progress of the drilling operation is described within the context of three parallel, deep-drilling operations, the problems that occurred and the solutions we developed. Modified procedures are described, such as the monitoring of penetration rate via cable weight rather than motor torque, and modifications to the system (e.g. closing the openings at the lower end of the outer barrel to reduce the risk of immersing the drill in highly concentrated chip suspension). Parameters of the drilling (e.g. corebreak force, cutter pitch, chips balance, liquid level, core production rate and piece number) are discussed. We also review the operational mode, particularly in the context of achieved core length and piece length, which have to be optimized for drilling efficiency and core quality respectively. We conclude with recommendations addressing the design of the chip-collection openings and strictly limiting the cable-load drop with respect to the load at the start of the run.

  • 37.
    Zdanowicz, Christian M.
    et al.
    Geological Survey of Canada.
    Fisher, D. A.
    Geological Survey of Canada.
    Clark, I.
    University of Ottawa.
    Lacelle, D.
    University of Ottawa.
    An ice-marginal δ18O record from Barnes Ice Cap, Baffin Island, Canada2002In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 35, no 1, p. 145-149Article in journal (Refereed)
    Abstract [en]

    Barnes Ice Cap, Baffin Island, Canada, is a remnant of the Laurentide ice sheet that separated from it about 8500 years ago. Owing to recession of the ice cap during the Holocene, Pleistocene-age ice is now exposed along the margin in a distinctive bubble-rich white band. δ180 variations across the white ice resemble those in Canadian Arctic ice cores, suggesting that Barnes Ice Cap preserves a climatic record through thelast glacial period, possibly reaching back into the previous (Sangamon) interglacial. The δ180 shift at the Wisconsin-Holocene transition (15 per mil) exceeds that in other Canadian and Greenland records and cannot be explained solely in climatic terms. A steady-state model reconstruction of the Laurentide ice sheet during the Last Glacial Maximum suggests that Late-glacial strata in Barnes Ice Cap originated high up ( >2400 m a.s.l.) and far "inland" on the ice sheet, along a ridge that extended between the ancestral Foxe and Keewatin ice domes.

  • 38.
    Zdanowicz, Christian
    et al.
    Carleton University, Ottawa, Canada.
    Michel, F. A.
    Carleton University, Ottawa, Canada.
    Shilts, W. W.
    Geologival Survey of Canada.
    Basal debris entrainment and transport in glaciers of southwestern Bylot Island, Canadian Arctic1996In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 22, no 1, p. 107-113Article in journal (Refereed)
    Abstract [en]

    ABSTRACT. Glaciers on southwestern Bylot Island in the Canadian Arctic flow from an alpine setting in high-grade crystalline Archean terrane, on to coastal lowlands underlain by clastic sedimentary strata of Cretaceous to Tertiary age.  We have used the contrasting mineralogy of the substrate as a tool to study subglacialentrainment and transport of debris in two large piedmont glaciers on Bylot Island. High chlorite/ and mica-illite/smectite ratios indicate that most basal debris is derived from crystalline rocks underlying the upper reaches of the glaciers. The subglacial accretion of Cretaceous-Tertiary sediments appears restricted to the lowermost part ofthe basal zone and is most noticeable near the glaciers' termini. lce associated with discrete silty-sandy debris layers is characterized by an isotopic signature indicative of refreezing of meltwater at the glacier sole. The compositional, textural and isotopic characteristics of basal sediment and ice lead us to conclude that subglacial entrainment through basal ice accretion occurs in both the upper and marginal parts of the glaciers

1 - 38 of 38
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