Vertical snow structures from in-situ and remote sensing measurements

Snow on sea ice alters the properties of the underlying ice cover as well as associated exchange processes at the interfaces between atmosphere, sea ice, and ocean. As Antarctic snow cover persists during most of the year, it contributes significantly to the sea-ice mass budget due to comprehensive physical (seasonal) transition processes within the snowpack. It is therefore necessary to locate and quantify internal snowmelt, snow metamorphism, and snow-ice formation in the Antarctic snowpack on different spatial scales. Doing so, we present here, on the one hand, in-situ observations of physical snow properties from point measurements and transect lines during recent expeditions in the Weddell Sea from 2013 to 2018, covering summer and winter conditions. On the other hand, we used passive microwave (19 and 37 GHz signal frequency) as well as scatteroemter observations (5.6 and 13.4 GHz signal frequency) to describe snowmelt processes on Antarctic-wide scales. As different signal frequencies result in different penetration depths, we hypothesize that the different sensors respond to snow melt processes in different depths within the snow cover. The observed differences are consistent with the effects of short- and longwave radiation transmission and absorption, and the related occurrence of strong snow metamorphism, internal snow melt, and superimposed ice formation known to be important on Antarctic sea ice. Results of the study will improve our understanding on processes and interactions in the snowpack as well as at the snow/ice interface associated with seasonal and inter-annual variations in the sea-ice energy and mass budgets of the Southern Ocean