AntExtremes - Extreme events in the Antarctic: Understanding strong regional sea ice fluctuations in connection with atmospheric and oceanic drivers

• Applicants: Monica Ionita-Scholz, Ph.D.; Dr. Christian Melsheimer
• Subject Area: Oceanography ; Atmospheric Science
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 542090870

Sea ice is an important component in the Earth system as it controls heat, momentum and mass exchange between the atmosphere and the ocean, is an important part of the polar marine ecosystem and also impacts human activities in polar regions. Sea ice has been monitored continuously and globally by satellite since the 1970s, which allowed to closely observe the dramatic decline of sea ice in the Arctic in the past decades. Quite conversely, until 2015, the Antarctic sea-ice area was rather stable and did not show strong trends. However, year to year variability was already large, and especially regionally, strong fluctuations in sea ice area were observed. These events were often caused by thermodynamic (ocean and atmosphere) as well as dynamical (mainly atmosphere) drivers. Since 2015, however, the Antarctic sea-ice area has mostly stayed well below the long-term climatological mean (with temporally limited exceptions in 2020 and 2021) and has shown a strong negative trend. In 2023, the Antarctic sea-ice area was the lowest ever observed and during fall freeze-up the ice extent was more than five standard deviations below the climatological mean. However, regional differences are large with above average ice area in the Amundsen Sea and strongly below average ice area everywhere else. In order to understand the drivers of such extreme sea ice events, we analyse strong regional anomalies (i.e., deviations from climatological mean) in sea-ice conditions (ice concentration, ice type, and drift) using satellite observations in connection with atmospheric and oceanic conditions (e.g., wind, heat and moisture advection, air pressure pattern, sea surface temperature) from the ERA5 meteorological reanalysis data. In addition, we look at another kind of extreme events, polar lows. Polar lows are small, short-lived,but strong cyclones that develop over open water, are hence closely linked to the sea ice distribution, and possibly influence the sea ice in turn. Polar lows can be detected using microwave satellite radiometers. The statistical analysis yields spatiotemporal patterns and correlations between the sea ice variables and the possible atmospheric/oceanic drivers which then feed a statistical prediction model with the aim to predict extreme events of the sea ice a few months in advance. This will not only enhance our understanding of how the Antarctic sea ice reacts to external drivers, but also be useful outside science as extreme sea ice conditions (e.g., massive sea ice loss) have significant impact on human activities (shipping, expeditions) and infrastructure (research stations).

• DFG Programme: Infrastructure Priority Programmes
• Subproject of: SPP 1158: Infrastructure area - Antarctic Research with Comparative Investigations in Arctic Sea Ice Areas
• International Connection: South Africa, United Kingdom
• Cooperation Partners: Professor Dr. Thomas J. Bracegirdle; Professor Dr. Marcello Vichi