Satellite-based detection of snow wetness and wave-induced surface wetting of Antarctic sea ice

Abstract

Sea ice is a fundamental, highly variable element of the polar environments. Its variability deeply affects, not only the local climate- and ecosystem but also the global Earth system. Until recently Arctic sea ice experienced a general retreat as expected under global warming whilst Antarctic sea ice extent increased up to 2014. However, Antarctic sea-ice extent at maximum annual cover shifted from a record high (2014) to a record minimum extent (2023), begging to explore the relationship between sea ice and ocean/atmospheric forcing. In this work, we pinpoint some extreme atmospheric events, specifically, atmospheric rivers (ARs) to analyse their influence on sea ice and snow properties. ARs can have a direct impact on the nature of oceanic surface gravity waves. Increasing wind speed causes an increase in wave height and energy, leading to greater repercussions on snow and sea ice. The sea ice area most affected by this forcing is the one that separates the pack ice from the open oceans, known as the marginal ice zone (MIZ). Our analysis aims to understand wave-sea ice interaction and its effect on accelerating snow melt or changing sea ice morphology. To accomplish this we focus on the influence of wave overwash on sea ice surfaces during the spring season in the Weddell Sea. The MIZ is identified by posing the limits of sea ice concentration (SIC) ranging from 15% to 80%. ARs events are identified using ERA5 reanalysis data, estimating their integrated water vapour transport (IWV) and vertically integrated vapour transport (vIVT) values, which are considered extreme if they exceed 95% of historical norms for the same location and time of year over a time interval that spreads from 1980 to 2022. Data obtained from AMSRE, AMSR2 & SMOS passive microwave sensors are used to generate time series and local maps of brightness temperature. These microwave signatures serve in the analysis of the possible spatial and temporal correlation between ARs events and sea ice and snow characteristics. Initial findings suggest that ARs and their subsequent gravity waves may significantly affect the wetting of sea ice and of the snow on it leading to increased melting of the MIZ. This study will improve the methods to inform models used to forecast the impact that extreme atmospheric events can have on sea ice and snow, offering new directions to investigate the coupled ocean-sea ice-atmosphere system in a changing climate.