Evaluation of the atmospheric and oceanic forcing of sea ice at DDU, East Antarctica using in situ, remotely sensed, and modeling data

Dumont d’Urville (DDU) is a French research station located off the Adelie Coast of East Antarctica on Petrel Island. DDU is a permanently occupied station that is heavily instrumented, creating a unique opportunity to integrate in situ meteorological and oceanographic observations with remotely sensed and modeling data sets. Furthermore, this area is characterized by intense katabatic winds and shallow bathymetry, as well as being the site of Adelie and Emperor penguin rookeries. The coastal region of Eastern Antarctica is also characterized by large variations in sea ice extent and volume. For example, in the summers of 2016-2017 and 2017-2018, the pack ice was dense enough to prevent the supply and research vessel l’Astrolabe from reaching the French research station DDU and to limit wildlife access to open water. In 2016, the closest open water was nearly 90 km away from the coastline, which had a significant impact on the health of the local bird populations leading to starvation and death of numerous individuals. In contrast the summer of 2017-2018, the pack ice broke up early in the melt season, and open water occupied much of the coastal region in Terre Adelie and beyond. We developed a climatology of the summertime meteorological conditions at DDU using in situ observations from CALVA, GLACIOCLIM and MeteoFrance covering 2005-2019. Environmental characteristics such as temperature, humidity, precipitation, cloud cover, wind speed and direction were then related to sea ice properties retrieved from the satellite-derived weekly ice charts produced by the National Ice Center. The sea ice concentration and thickness were assessed at DDU, as well as for a larger region on the eastern Antarctic Coast that extends 20 degrees longitude in either direction from DDU. These features were also explored in the context of larger scale teleconnections to explore the mechanisms that lead to the presence or absence of dense pack ice. Preliminary analysis shows a statistically significant relationship between relative humidity and incoming radiation/clouds to changes in sea ice area, extent, and thickness. Moreover, the localized effect of katabatic winds is illustrated. Further analysis using reanalysis data will determine whether or not atmospheric conditions at DDU and the Adelie Coast are characteristic of the larger region encompassed by the study area (120 to 160°E). Model reanalysis data will also be useful for quantifying the influence of ocean swell on the break up of sea ice in this region. Likewise, changes to humidity and cloud properties due to storms and atmospheric rivers are hypothesized to have an influence on sea ice conditions. Better understanding of the interactions of the atmosphere-ocean-sea ice along the Eastern Antarctic coast will allow us to better forecast and simulate further changes in ice conditions and access to open water in the future that heavily impact biophysical marine and terrestrial systems.