PAST AND PRESENT PEATLAND DEVELOPMENT IN ANTARCTICA UNDER WARM CLIMATES

Here we report the recent resurgence of a peat deposit on Cape Rasmussen (65.2°S, 64.1°W), off the Graham Coast of the Antarctic Peninsula, in proximity to the Argentine Islands. To our knowledge, peatlands have never been reported in Antarctica. We interpret peatland initiation, around 2700 cal. BP, as well as its recent resurgence, less than 50 years ago, as new and important indicators of ecosystem changes that have been brought about by warmer conditions in the region.

While numerous aerobic moss peatbanks (non-wetland systems) have been described and analyzed across the Antarctic Peninsula over the past few decades, the reported peatland on Cape Rasmussen conforms to the wetland definition and resembles soligenous systems typically found in the boreal, subarctic, and sub-Antarctic regions. The ecosystem is approximately 100 m² in size, is characterized by a shallow water table, and its surface vegetation is dominated by Warnstorfia (moss).

Peat inception was dated at 2700 cal. BP and followed by rapid peat accumulation (~ 0.1 cm/year) until 2150 cal. BP. Our multi-proxy analysis then shows a 2000-year-long stratigraphic hiatus as well as the recent resurgence of peat accumulation, sometime after 1950 AD. The existence of a thriving peatland at 2700-2150 cal. BP implies regionally warm summer conditions extending beyond the mid-Holocene. Recent peatland recovery at the study site might have been triggered by ongoing rapid warming, as the area is experiencing climatic conditions approaching those found on milder, peatland-rich sub-Antarctic islands (50-60°S). Assuming that colonization opportunities and stabilization mechanisms would allow peat to persist in Antarctica, our results suggest that longer and warmer growing seasons in the maritime Antarctic region may lead to a peatland-rich landscape in the future.

One of the key reasons explaining the widespread occurrence of moss peatbanks and the scarcity of peatlands in Antarctica might be their different surface energy balances. With their saturated grounds, peatlands lose energy to the atmosphere through latent heat flux, such that their surface is often cooler than air temperature during daytime. That is not the case in dry, aerobic peatbanks, which tend to be warmer than surrounding air during daytime, as they absorb direct heat from the Sun.