Response of changes in sea ice thickness to cyclones: new insights from the MOSAiC expedition

Abstract Sea ice thickness (SIT) is essential to evaluate sea ice mass balance in the Arctic, regulating the feedback of the sea ice-ocean system to the lower atmosphere, as well as the physical processes of the sea ice itself. In this study, we elucidate the response of SIT change to cyclones across the region of ~50 km from both thermodynamic and dynamic perspectives and quantify their relative contributions at a synoptic time scale. The latest observations collected during the Multidisciplinary Drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition, combined with atmospheric reanalysis are utilized. We reveal that the interest period of the MOSAiC year (2019/11–2020/07) was characterized by more frequent and intensified storm events with 39 cyclones hitting the ice camp during the 9-month drift. In the observed cyclone events, the primary thermodynamic response was through ice bottom growth or melt governed by the surface radiation budget and thermal conduction within the ice, which was adjusted by the air mass advection associated with cyclones; the dynamic response of the SIT lay on the ice deformation events induced by the wind forcing when cyclone occurred. The conditions of near-surface atmosphere and sea ice during cyclone periods were significantly different from those of non-cyclone periods. Moreover, during different cyclone periods throughout the ice season, the average thermodynamic and dynamic contributions to the SIT change are estimated to be 0.02-1.44 cm/day and 0.05-28.54 cm/day, respectively. We argue that the dynamic process induced by cyclones through ice divergence generally dominates local SIT change at a synoptic time scale.