ИСТИНА

Knowledge of frontal ablation of tidewater glaciers on Novaya Zemlya is very limited, meanwhile it is an important component of their mass balance and should be accounted in iceberg risk assessments for offshore hydrocarbons exploration and transport activities. Area of our interest is the Kara sea side of Novaya Zemlya, where 3 large tidewater glaciers - Roze, Rozhdestvensky and Vershinsky have been recently surveyed for ice thickness and surface velocity. Ice thickness data were derived from our 20 MHz airborne RES survey. Glacier surface velocities were extracted from repeated Landasat-8 imagery and GoLIVE v.1 dataset for 2014-2016, repeated TerraSAR images for 2017-2018, and continuous records from GPS beacons installed on these glaciers. ArcticDEM data on glacier ice surface combined with RES ice thickness data were used to compile glacier bedrock topography maps and transects. Obtained information was used to estimate the ice discharge across the fluxgates at glacier termini, the frontal ablation, and potential calving productivity. Data on ice surface velocity retrieved by different methods and sources are in a good agreement and show noticeable seasonal pattern on Vershinsky glacier. Area of potential calving zone (part of glacier area with bedrock topography below sea level) reaches 91.3 km2 on Vershinsky, 54.3 km2 on Roze and 24.7 km2 on Rozhdestvensky glacier. Considering the size of those terminus parts of Roze and Vershinsky glaciers that are close to flotation, the maximum horizontal dimensions of potential icebergs could reach 50-500 m and 60-130 m thick. Average ice thickness registered at glacier fronts is 95 m. Maximum ice flow velocity at the front of Vershinsky Glacier reaches 350-390 m a-1. Frontal ablation rate of three studied glaciers is assessed as 0.48 km3 a-1 for 2015-2016. This work is partly accomplished in frame of RFBR grants 18-05-60109 and 18-05-60067.