Reserve of ice in glaciers on the Nordenskiöld Land, Spitsbergen, and their changes over the last decades

Abstract

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.

Distribution of cold and temperate ice and water in glaciers at Nordenskiöld Land, Svalbard, according to data on ground-based radio-echo sounding

“…The total volume of glaciers V Σ was determined using DEMs of total ice thickness H Σ as sum of product of area of cells A k by total ice thickness H Σk in each cell of the interpolation grid (Martin-Español et al 2016;Lavrentiev et al 2019):…”

“…Area S of glaciers in the year of RES measurements, mean thickness of glacier H mean , average thickness of cold ice H avcold and temperate ice H avtemp , volume of cold ice V cold and temperate ice V temp , measured total volume of glaciers V Σ , volume fraction of temperate ice in total volume of glacier FTIV=V temp /V Σ , and water storage W s =W×V temp in temperate ice with water content W Data for area S, mean ice thickness H mean , total volume V Σ of glaciers and errors in their estimates are given byLavrentiev et al (2019);c) Values of water storage W s in polythermal glaciers are given for estimated average water content W in temperate ice 2%In polythermal glaciers, the RWV in temperate ice v temp can range from 156 to 168 m/mcs; i.e., on average v temp =162 m/mcs, ε vtemp =± 6 m/mcs and depends on water content W in temperate ice. At maximum thickness of temperate ice H temp =240 m, ε Htemp = ±5.7 m (±2.4%).…”