Climate Change And Variability In The East Antarctic Icescape

In the Adelie Sea region of East Antarctica, atmospheric and oceanographic forcing influence sea ice concentration, thickness, and summer sea ice melt, particularly in the local Dumont d’Urville (DDU) Sea. Previous work demonstrated that the sea ice coverage in the DDU sea is out of phase with the overall patterns of sea ice concentration on the East Antarctic Coast near Adelie Land. However, the cause(s) of this variation has not yet been fully explored. Using a combination of fourteen years (2005-2019) of in-situ observations from instrumentation located at and around the French research station, Dumont d’Urville, and ERA5 climate reanalysis data (2005-2023, gridded 0.25°x0.25° hourly) from the European Centre for Medium-Range Weather Forecasts (ECMWF), we construct a summertime (NDJF) climatology of the surface, atmospheric and oceanographic conditions at DDU and in the surrounding area (area in a box bounded by 120°E -54°S and 160°E -70°S). To gain insight into the local-to-regional processes that drive sea ice concentration and thickness, we analyze in-situ environmental observations and reanalysis variables including air temperature, humidity, radiative fluxes, cloud cover, wind speed and direction, as well as sea surface temperature as they relate to satellite-derived weekly sea ice extent and concentration. The observational data are compared with the World Meteorological Organization (WMO) climatological standard period of 1991-2020 to understand variance and anomaly trends. Anomaly analysis of sea ice concentration and thickness and empirical orthogonal function analysis of sea ice and other environmental characteristics are used to identify areas of high and low variability throughout the study area and period. We also analyze the periods before and after the Mertz Glacier tongue calving (Feb 12-13, 2010) to identify how the relative strength of meteorological and oceanographic forcing were impacted by the calving event.

We observe inter-annual and intra-seasonal variations in the correlations of select atmospheric variables and sea ice concentration and thickness throughout the study period. For the region around DDU, we find a relationship between changes in sea ice area, extent, and thickness with respect to atmospheric relative humidity, downwelling radiation, cloud cover and katabatic winds from in-situ data. We also see an overall positive trend in surface temperature, low cloud cover, longwave downwelling radiation and relative humidity across the larger study area. ERA 5 reanalysis data add further evidence to the in-situ observed association between sea ice concentration and extent with respect to katabatic winds in the DDU area (attached figure), but this is less evident at the larger geographic scale. Detailed analysis across our three regional scales (in-situ, DDU area and larger study area) provide insight into the importance of local and coastal processes that behave differently from larger spatial areas analysis.