Brief Communication: Sudden drainage of a subglacial lake beneath the Greenland Ice Sheet
Summary: In the summer of 2011, a large crater appeared in the surface of the Greenland Ice Sheet. It formed when a subglacial lake, equivalent to 10,000 swimming pools, catastrophically drained in less than 14 days. This is the first direct evidence that surface meltwater that drains through cracks to the bed of the ice sheet can build up in subglacial lakes over long periods of time. The sudden drainage may have been due to more surface melting and an increase in meltwater reaching the bed.
Stable climate and surface mass balance in Svalbard over 1979–2013 despite the Arctic warming
Summary: We have modelled the surface mass balance (SMB) of Svalbard with the model MAR over 1979--2013. The mean SMB is slightly negative and the Svalbard glaciers are losing mass through surface processes (mainly precipitation and runoff), but there has been no acceleration of the surface melt, contrary to Greenland where melt records have been broken since 2006. We attributed it to a change in atmospheric circulation, resulting in northerly cold flows over Svalbard damping Arctic warming.
Recent summer Arctic atmospheric circulation anomalies in a historical perspective
Summary: The 2007-2012 summertime circulation anomaly over the Arctic region (i.e. more high pressure systems over the Beaufort Sea, the Canadian Arctic Archipelago, and Greenland) is put in a historical perspective. While the 2007-2012 anomaly seems to be exceptional, similar circulation conditions have occurred since 1871, on the basis of five reanalyses (ERA-Interim, ERA-40, NCEP/NCAR, ERA-20C, 20CRv2). The attribution of this anomaly (natural variability or global warming) remains debatable.
The impact of snow depth, snow density and ice density on sea ice thickness retrieval from satellite radar altimetry: results from the ESA-CCI Sea Ice ECV Project Round Robin Exercise
Summary: Snow depth and ice density are equally important parameters for sea ice thickness retrieval from radar altimetry of Arctic sea ice. Development of a new snow depth data set is mandatory as the Warren snow depth climatology does not represent the actual snow depth distribution. An optimal choice of ice density can be realized by including ice type and degree of deformation. Retrieval and validation enhancement requires more contemporary ice freeboard, thickness, and density and snow depth data.
Quantifying mass balance processes on the Southern Patagonia Icefield
Summary: We use a meteorological-glaciological multi-model approach to quantify, for the first time, melt and accumulation of snow on the Southern Patagonia Icefield (SPI). We were able to reproduce the high measured accumulation of snow of up to 15.4 m water equivalent per year as well as the high measured ablation of up to 11 m water equivalent per year. Mass losses of the SPI due to calving of icebergs strongly increased from 1975-2000 to 2000-2011 and were higher than losses due to surface melt.
UAV photogrammetry and structure from motion to assess calving dynamics at Store Glacier, a large outlet draining the Greenland ice sheet
Summary: An unmanned aerial vehicle (UAV) equipped with a commercial digital camera enabled us to obtain high-resolution digital images of the calving front of Store glacier, Greenland. The three sorties flown enabled key glaciological parameters to be quantified in sufficient detail to reveal that the terminus of Store glacier is a complex system with large variations in crevasse patterns surface velocities, calving processes, surface elevations and front positions at a daily and seasonal timescale.
Ice and AIS: ship speed data and sea ice forecasts in the Baltic Sea
Summary: The Baltic Sea is a seasonally ice-covered marginal sea in central northern Europe. In wintertime, on-time shipping depends crucially on sea ice forecasts. Among the forecasting tools heavily applied are numerical models, which suffer from a lack of calibration data because relevant ice properties are difficult (and costly) to monitor. We developed an innovative and inexpensive approach, by using ship speed observations obtained by the automatic identification system (AIS) to asses such models.
Sea ice pCO2 dynamics and air–ice CO2 fluxes during the Sea Ice Mass Balance in the Antarctic (SIMBA) experiment – Bellingshausen Sea, Antarctica
Summary: Temporal evolution of pCO2 profiles in sea ice in the Bellingshausen Sea, Antarctica (Oct. 2007), shows that physical and thermodynamic processes control the CO2 system in the ice. We show that each cooling/warming event was associated with an increase/decrease in the brine salinity, TA, TCO2, and in situ brine and bulk ice pCO2. Thicker snow covers reduced the amplitude of these changes. Both brine and bulk ice pCO2 were undersaturated, causing the sea ice to act as a sink for atmospheric CO2.
Summary: Elevation dependencies of snow depth are analysed based on snow depth maps obtained from airborne remote sensing. Elevation gradients are characterised by a specific shape: an increase of snow depth with elevation is followed by a distinct peak at a certain level and a decrease in the highest elevations. We attribute this shape to an increase of precipitation with altitude, which is modified by topographical-induced redistribution processes of the snow on the ground (wind, gravitation).
Deglaciation of the Caucasus Mountains, Russia/Georgia, in the 21st century observed with ASTER satellite imagery and aerial photography
Summary: The paper investigates changes in the area of 498 glaciers in the main Caucasus ridge and on Mt. Elbrus (the highest summit in geographical Europe), Russia/Georgia in the late 20th and 21st centuries using ASTER and Landsat imagery with 15 m resolution from 1999-2001 and 2010-2012 and aerial photography from 1987-2001. The glacier area decreased by 4.7±2.1% or 19.2±8.7 km2 from 1999-2001 to 2010/12. The recession rates of glacier terminus more than doubled between 1987-2000/01 and 2000/01–2010.
Are seasonal calving dynamics forced by buttressing from ice mélange or undercutting by melting? Outcomes from full-Stokes simulations of Store Glacier, West Greenland
Summary: Many iceberg-calving glaciers in Greenland have recently been observed to accelerate and retreat, prompting fears about their future stability in the face of climate change. We present results from a flow modelling study of Store Glacier, West Greenland, which suggest that glacier geometry may play an important role in determining calving glacier stability. Store Glacier flows into a narrow, shallow fjord and our model suggests this may make it insensitive to future ocean warming.
Inferred basal friction and surface mass balance of the Northeast Greenland Ice Stream using data assimilation of ICESat (Ice Cloud and land Elevation Satellite) surface altimetry and ISSM (Ice Sheet System Model)
Summary: We present a temporal inversion of surface mass balance and basal friction for the Northeast Greenland Ice Sheet between 2003 and 2009, using the altimetry record from ICESat. The inversion relies on automatic differentiation of ISSM and demonstrates the feasibility of assimilating altimetry records into reconstructions of the Greenland Ice Sheet. The boundary conditions provide a snapshot of the state of the ice for this period and can be used for further process studies.
Estimating the volume of glaciers in the Himalayan–Karakoram region using different methods
Summary: Existing methods (area–volume relations, a slope-dependent volume estimation method, and two ice-thickness distribution models) are used to estimate the ice reserves stored in Himalayan–Karakoram glaciers. Resulting volumes range from 2955–4737km³. Results from the ice-thickness distribution models agree well with local measurements; volume estimates from area-related relations exceed the estimates from the other approaches. Evidence on the effect of the selected method on results is provided.
H. Frey, H. Machguth, M. Huss, C. Huggel, S. Bajracharya, T. Bolch, A. Kulkarni, A. Linsbauer, N. Salzmann, and M. Stoffel The Cryosphere, 8, 2313-2333, 2014 AbstractFinal Revised Paper (PDF, 7532 KB)Discussion Paper (TCD)
12 Dec 2014
Assessing spatio-temporal variability and trends in modelled and measured Greenland Ice Sheet albedo (2000–2013)
Glacier topography and elevation changes derived from Pléiades sub-meter stereo images
Summary: We evaluate the potential of Pléiades sub-meter satellite stereo imagery to derive digital elevation models (DEMs) of glaciers and their elevation changes. The vertical precision of the DEMs is ±1 m, even ±0.5m on the flat glacier tongues. Similar precision levels are obtained in accumulation areas. Comparison of a Pléiades DEM with a SPOT5 DEM reveals the strongly negative region-wide mass balances of glaciers in the Mont Blanc area (-1.04±0.23m at 1 water equivalent) during 2003-2012.
E. Berthier, C. Vincent, E. Magnússon, Á. Þ. Gunnlaugsson, P. Pitte, E. Le Meur, M. Masiokas, L. Ruiz, F. Pálsson, J. M. C. Belart, and P. Wagnon The Cryosphere, 8, 2275-2291, 2014 AbstractFinal Revised Paper (PDF, 8151 KB)Discussion Paper (TCD)