Thickness of the upper cold ice layer in the ablation area of the polythermal glacier Grønfjordbreen (Spitsbergen) was estimated by means of numerical modeling. The results were compared with data of radio-echo sounding of the same glacier obtained in 1979 and 2012. Numerical experiments with changing water content in the lower layer of temperate ice and surface snow cover thickness made possible to compare calculated and modeled cold ice thicknesses and to estimate their changes for 33‑year period caused by regional climate change. According to data of radio-echo sounding, thickness of the cold ice layer decreased, on average, by 34 m. Numerical modeling shown similar results: the cold ice layer became thinner by 31 m and 39 m at altitudes 100–300 a.s.l. under the snow cover thickness of 1 m and 2 m. We explain this by rising of annual mean air temperature by 0,6 °С as compared to data of the nearest meteorological station Barentsburg in the same period. We believe that changes in cold ice layer thickness in polythermal glaciers can be used for estimation of changes in such regional climatic parameter as mean air temperature at different altitudes of the glacier surface in the ablation area.
The glaciers and ice caps in the Arctic are experiencing noticeable changes which are manifested, in particular, in the intensification of their dynamic instability. In this paper we present data on a largescale surge in the Western basin of the Vavilov ice dome on the archipelago Severnaya Zemlya, derived from satellite images and supplemented by airborne RES-2014 and available publications. Analysis of 28 space images of 1963–2017 demonstrated that the surge developed over the whole period. In the fi st decade (1963–1973), the advance was very slow – from 2–5 to 12 m/year. Since the 1980-ies, the ice movement began to accelerate from tens to a hundred of meters per a year in the 2000-ies. The sudden change happened in the year 2012 when the surge front began to move already at speeds of about 0.5 km/year. In 2015, the volume of advanced part reached almost 4 km3. Maximal speed 9.2 km/year was recorded in 2016. From 1963 to 2017, the edge of the glacier advanced by 11.7 km, and its area increased by 134.1 km2 (by 47% relative to the basin area of 1963), that caused spreading of crevasse zone up the glacier. Surface speeds reached a maximum of 25.4 m/day in 2016 and decreased to 7.6 m/day in 2017. The authors suggest that the initial activation of the southern and western edges of the ice dome could be a reaction to the climate signal, possibly occurred several centuries ago. The ice crevassing and cryo-hydrological warming of ice, enhanced by positive feedback, resulted in instability of the glacier and the displacement of the edge of the ice belt containing moraine and frozen to the bed, which transformed into a catastrophic movement. The surge was facilitated by change of bedrock conditions as the ice lobe progressed offshore from permafrost coastal zone to the area of loose marine bottom sediments with low shear strength. The surge seems to be also stimulated by anomalously warm summer of 2012.
Data on thickness and area of 16 glaciers on the Nordenskiöld Land (Svalbard) were obtained in 1999 and 2010–2013. These data were used to determine volume of the glaciers and to establish statistical local relationship between the volume V and the area A (V–A scaling) in the form of the power function V = cAγ, and then to calculate the total ice volume of all 202 glaciers in this area and its changes during the period since 1936 to 2002–2008. The total area of 16 glaciers was 129.9±0.35 km2, 14 of which had areas from 0.2 to 8.1 km2. The two largest ones, the Fridtjof and the West Grenfjord, had the areas 17.5 and 47.3 km2, respectively, and thus occupied about 50% (64.8 km2) of the total area of 16 glaciers. These two glaciers account for 67% of the total measured volume (10,034 km3) of the 16 glaciers. A nonlinear least-squares method was used to estimate ice reserves in all 202 glaciers from data on the volume and area of 16 glaciers. The relation between volume V and area A of the glaciers (V–A scaling) was obtained as the ratio V = 0.03637A1,283 with 95%‑th confidence intervals of the coefficients с and γ, (0.02303–0,4971) and (1.184–1.381), respectively. This made possible to calculate total volume of 202 glaciers as of 2002-2008 state using data from RGI v.6.0, and that prove to be equal to 32.89 (16.75–56.63) km3. To verify this estimation, we applied the bootstrapping method for chosen 43 glaciers and calculated the volume by means of sequential use of data for large and smaller glaciers. According to this estimate, the total volume of 202 glaciers amounted to 30.34 km3 with a 95% confidence interval of 15.42–44.27 km3, that turned out to be slightly smaller than the volume calculated by nonlinear least squares method basing on measurements on 16 glaciers. Despite the large error (on the average, from −49% to +84%) in estimating the total volume of 202 glaciers in the Nordenskiöld Land, the data obtained were used for assessment of relative changes in the total volume of glaciers in this area over different time intervals. During the period from 1936 to1990 (54 years), the total area of all glaciers reduced from 738.1 to 546.7 km2, and the total volume decreased from 49,205 to 34,857 km3. Similar results for the period 1990–2002–2008 (~15 years) are the total area changes from 546.7 to 507.9 km2 and their total volume - from 34.857 to 32.890 km3. The rate of decrease of the volume for the period 1936–1990 was equal to −0.266 km3/year, for the period 1990–2002–2008 – minus 0.131 km3/year, and as a whole for the studied period (since 1936 to 2002–2008) – minus 0.236 km3/year. The average mass balance in the first period was equal to −0.372 m w.e./year, in the second one −0.224 m w.e./year, and for the whole time −0.342 m w.e./year.
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