Reconstructing neoglacial ice advance on Signy Island, Maritime Antarctica, from moss burial ages

Late Holocene glacial dynamics in Maritime Antarctica are relatively poorly understood due to limited data availability. Here, we present a reconstruction of neoglacial ice advance on Signy Island (South Orkney Islands, 60°S 45°W) based on radiocarbon-dated moss burial ages. The results showed that mosses were buried by neoglacial ice advance starting from an oldest age of approximately 218 CE (Common Era), with a peak in burial dates between 1000 and 1400 CE. The timing of advance is in line with regional temperature reconstructions, and moves former local ice advance reconstructions back by several centuries. Map and satellite image comparisons over the past 50 years confirm that the island’s ice cap is now retreating (horizontally) at increasing rates, from a mean of approximately 8 m/yr over the past 50 years to 20 m/yr in the period 2020-2023. Compared to the reconstructed average advance rate between 1300 and 1600 CE based on current and past recorded moss burial dates, the ice cap is currently retreating about six times faster than it previously advanced. Reconstructing periods of past glacial advance and retreat, as in our study, is important to determine the sensitivity of low altitude ice caps to the ongoing temperature increases predicted across the sub- and Maritime Antarctic.