Giant ice rings in southern Baikal: multi-satellite data help to study ice cover dynamics and eddies under ice The Cryosphere DOI 10.5194/tc-15-4501-2021 17 November 2021 Giant ice rings are a beautiful and puzzling natural phenomenon. Our data show that ice rings are generated by lens-like warm eddies below the ice. We use multi-satellite data to analyse lake ice cover in the presence of eddies in April 2020 in southern Baikal. Unusual changes in ice colour may be explained by the competing influences of atmosphere above and the warm eddy below the ice. Tracking ice floes also helps to estimate eddy currents and their influence on the upper water layer. Read more
Recent degradation of interior Alaska permafrost mapped with ground surveys, geophysics, deep drilling, and repeat airborne lidar The Cryosphere DOI 10.5194/tc-15-3555-2021 10 September 2021 Permafrost is actively degrading across high latitudes due to climate warming. We combined thousands of end-of-summer active layer measurements, permafrost temperatures, geophysical surveys, deep borehole drilling, and repeat airborne lidar to quantify permafrost warming and thawing at sites across central Alaska. We calculate the mass of permafrost soil carbon potentially exposed to thaw over the past 7 years (0.44 Pg) is similar to the yearly carbon dioxide emissions of Australia. Read more
Thaw-driven mass wasting couples slopes with downstream systems, and effects propagate through Arctic drainage networks The Cryosphere DOI 10.5194/tc-15-3059-2021 18 August 2021 Climate-driven landslides are transforming glacially conditioned permafrost terrain, coupling slopes with aquatic systems, and triggering a cascade of downstream effects. Nonlinear intensification of thawing slopes is primarily affecting headwater systems where slope sediment yields overwhelm stream transport capacity. The propagation of effects across watershed scales indicates that western Arctic Canada will be an interconnected hotspot of thaw-driven change through the coming millennia. Read more
Mapping the aerodynamic roughness of the Greenland Ice Sheet surface using ICESat-2: evaluation over the K-transect The Cryosphere DOI 10.5194/tc-15-2601-2021 26 July 2021 We developed a method to estimate the aerodynamic properties of the Greenland Ice Sheet surface using either UAV or ICESat-2 elevation data. We show that this new method is able to reproduce the important spatiotemporal variability in surface aerodynamic roughness, measured by the field observations. The new maps of surface roughness can be used in atmospheric models to improve simulations of surface turbulent heat fluxes and therefore surface energy and mass balance over rough ice worldwide. ICESat-2: evaluation over the K-transect">Read more
Faster decline and higher variability in the sea ice thickness of the marginal Arctic seas when accounting for dynamic snow cover The Cryosphere DOI 10.5194/tc-15-2429-2021 16 July 2021 We re-estimate pan-Arctic sea ice thickness (SIT) values by combining data from the Envisat and CryoSat-2 missions with data from a new, reanalysis-driven snow model. Because a decreasing amount of ice is being hidden below the waterline by the weight of overlying snow, we argue that SIT may be declining faster than previously calculated in some regions. Because the snow product varies from year to year, our new SIT calculations also display much more year-to-year variability. Read more
Comment on “Exceptionally high heat flux needed to sustain the Northeast Greenland Ice Stream” by Smith-Johnsen et al. (2020) The Cryosphere DOI 10.5194/tc-15-2251-2021 5 July 2021 The modelling of Smith-Johnson et al. (The Cryosphere, 14, 841–854, 2020) suggests that a very large heat flux of more than 10 times the usual geothermal heat flux is required to have initiated or to control the huge Northeast Greenland Ice Stream. Our comparison with known hotspots, such as Iceland and Yellowstone, shows that such an exceptional heat flux would be unique in the world and is incompatible with known geological processes that can raise the heat flux. Read more
Atmospheric extremes caused high oceanward sea surface slope triggering the biggest calving event in more than 50 years at the Amery Ice Shelf The Cryosphere DOI 10.5194/tc-15-2147-2021 22 June 2021 The unexpected September 2019 calving event from the Amery Ice Shelf, the largest since 1963 and which occurred almost a decade earlier than expected, was triggered by atmospheric extremes. Explosive twin polar cyclones provided a deterministic role in this event by creating oceanward sea surface slope triggering the calving. The observed record-anomalous atmospheric conditions were promoted by blocking ridges and Antarctic-wide anomalous poleward transport of heat and moisture. Read more
On the attribution of industrial-era glacier mass loss to anthropogenic climate change The Cryosphere DOI 10.5194/tc-15-1889-2021 14 June 2021 The worldwide retreat of mountain glaciers and consequent loss of ice mass is one of the most obvious signs of a changing climate and has significant implications for the hydrology and natural hazards in mountain landscapes. Consistent with our understanding of the human role in temperature change, we demonstrate that the central estimate of the size of the human-caused mass loss is essentially 100 % of the observed loss. This assessment resolves some important inconsistencies in the literature. Read more
Pervasive diffusion of climate signals recorded in ice-vein ionic impurities The Cryosphere DOI 10.5194/tc-15-1787-2021 8 June 2021 Current theory predicts climate signals in the vein chemistry of ice cores to migrate, hampering their dating. I show that the Gibbs–Thomson effect, which has been overlooked, causes fast diffusion that prevents signals from surviving into deep ice. Hence the deep climatic peaks in Antarctic and Greenlandic ice must be due to impurities in the ice matrix (outside veins) and safe from migration. These findings reset our understanding of postdepositional changes of ice-core climate signals. Read more
Sudden large-volume detachments of low-angle mountain glaciers – more frequent than thought? The Cryosphere DOI 10.5194/tc-15-1751-2021 26 May 2021 Hardly recognized so far, giant catastrophic detachments of glaciers are a rare but great potential for loss of lives and massive damage in mountain regions. Several of the events compiled in our study involve volumes (up to 100 million m3 and more), avalanche speeds (up to 300 km/h), and reaches (tens of kilometres) that are hard to imagine. We show that current climate change is able to enhance associated hazards. For the first time, we elaborate a set of factors that could cause these events. Read more
