Fluctuating sea ice margins over the last ~50 kyr from the Sør Rondane mountains, East Antarctica, from a novel biological archive

There is spatial and temporal variability in the density of sea ice reconstructions available around Antarctica through the Holocene and the preceding Last Glacial Maximum. This study provides the first continuous sea ice reconstruction for the Princess Ragnhild Coast (20 °E and 34 °E), spanning the last ~50,000 years (Marine Isotope Stage 3, the Last Glacial Maximum, the deglaciation and the Holocene). We use snow petrel (Pagodroma nivea) stomach-oil deposits as archives of the sea ice environment in which the seabirds forage. For our study site, the snow petrels integrate information spanning the Atlantic and Indian Ocean sectors of the Southern Ocean, within ~1000 km of the coastline.  Our region of study currently has no Holocene reconstructions and only inferred Last Glacial Maximum sea ice reconstructions (Lhardy et al., 2021; Crosta et al., 2022).

Here, we use bulk stable isotopes, fatty acid ratios and elemental data to infer that sea ice in the Princess Ragnhild Coast area had a limited expansion during the Last Glacial Maximum. In agreement with previously inferred limits (Lhardy et al., 2021) our data suggests that the sea ice limits remained within ~500km of the continent edge over our time interval of interest. We also see a large negative trend in nitrogen isotopes between the Last Glacial Maximum and Holocene, in agreement with trends seen in marine sediment cores (Ai et al., 2021) although we suggest that diet largely remains the same throughout.