Surface-elevation changes and mass balance of the Academy of Sciences Ice Cap, Severnaya Zemlya

We have determined the surface-elevation change rates of the Academy of Sciences Ice Cap, Severnaya Zemlya, Russian Arctic, for two different periods: 2004-2016 and 2012/2013-2016. The former was calculated from differencing of ICESat and ArcticDEM digital elevation models, while the latter was obtained by differencing two sets of ArcticDEM digital elevation models. From these surface-elevation change rates we obtained the geodetic mass balance, which was nearly identical for both periods, at -1,72 +/- 0,67 Gt a(-1), equivalent to -0,31 +/- 0,12 m w.e. a(-1) over the whole ice cap area. Using an independent estimate of frontal ablation for 2016-2017 of -1,93 +/- 0,12 Gt a(-1) (-0,31 +/- 0,12 m w.e. a(-1)), we get an estimate of the climatic mass balance not significantly different from zero, at 0,21 +/- 0,68 Gt a(-1) (0,04 +/- 0,13 m w.e. a(-1)), which agrees with the near-zero average balance at a decadal scale observed during the last four decades. Making an observationally-based assumption on accumulation rate, we estimate the current total ablation from the ice cap, and its partitioning between frontal ablation, dominated by calving (similar to 54%) and climatic mass balance, mostly surface ablation (similar to 46%).