Influence of insolation patterns on the spatial distribution of mass balance of ice caps on Bennett Island (East Siberian Sea)

Abstract

Using Bennett Island (East Siberian Sea) as a case study, the role of shortwave radiation was examined in shaping the spatial distribution of the mass balance of Arctic ice caps. The aim of the study was to quantitatively assess the influence of spatial variability in insolation on glacier surface lowering. Changes in the surface elevation of four ice caps on Bennett Island, with a total area of approximately 56 km², over the period 2012–2022 were previously derived from multi-temporal ArcticDEM data. On average, the elevation change amounted to −6.27 ± 0.12 m, corresponding to a mass balance of −5.33 ± 0.39 m w. e. The mean incoming clear-sky shortwave radiation flux for a typical ablation season (76 frost-free days per year, based on ERA5-Land reanalysis data for 1994–2024) was modeled in SAGA GIS, taking into account both astronomical and terrain-related factors. The resulting distribution of values is characterized by spatial heterogeneity and direct dependencies on exposure and slope shading. The spatial variability of clear-sky insolation across the ice caps ranged from 360 to 520 W/m². For two of the ice caps, a statistically significant positive relationship between surface lowering and insolation was identified, with a linear trend of 0.013–0.021 m of additional melt per 1 W/m². Also, for two larger domes, a positive trend of ice melt was revealed, which equals 1.115–1.750 m per 100 m of altitude. It was shown that for smaller ice caps, the maximum differences in clear-sky insolation (160 W/m²) were equivalent to the effect of an elevation gradient of 100–200 m. For the largest ice cap, Toll, the influence of insolation could not be evaluated: due to horizontal ice motion, surface lowering derived using the geodetic method did not directly correspond to the actual melt. Therefore, further investigation required in situ mass balance measurements using the glaciological method.