ИСТИНА

The Vavilov ice cap (RGI nventory area 1781.4 km2, 79.30◦N, 95.47◦E) is located on October Revolution Island, the Severnaya Zemlya archipelago. We analyzed the changes of its western basin and its margin using remote sensing images covering the period 1963–2017 (Landsat-1, 5, 7, 8, Terra ASTER, Sentinel-1 and Corona). Results show that from 1963 to 2017 the basin outer margin advanced seaward by 11.7 km (central line), and basin area increased by 133 km2 (in April 2017 the basin area reached 428.84 km2). The accelerated advance started in 2010 and surge culminated in 2016. In summer 2016 the glacier front terminated in sea began to disintegrate, and in 2017 the advance continued but with lower velocity. The data on glacier surface velocities was taken from two sources. The first one is GoLIVE program. Also, we analyzed the synthetic aperture radar (SAR) data from Sentinel-1B satellite. Comparison of the velocities acquired from two sources for the same period shows that they are in a good agreement. Maximum velocity of glacier was in 2016 and reached 25.4 m day−1. To evaluate the volume changes of western basin of the Vavilov ice cap digital elevation models (DEM) were analyzed. We used ASTER DEMs of 2000 and 2015, which were applied to estimate elevation changes above sea level, and radar data obtained during RES survey in 2014 and bathytmetry from topographic maps of scale 1:200 000 to estimate changes below sea level. Above the contour line of 100 m (2015) the main trunk of the newly formed outlet glacier thinned by at least 1.918 km3, and at the same time its snout increased by 4.101 km3. This study is supported by the Russian Foundation for Basic Research, grant 16-35-00333, and by Russian National Foundation, grant 14-37-00038.