Peatbank response to late Holocene temperature and hydroclimate change in the western Antarctic Peninsula

The western Antarctic Peninsula experienced rapid warming in the second half of the 20th century, which has increased vascular plant abundance and moss productivity. To better understand long-term ecological responses, we used paleoecological and microclimate data to investigate dynamics of late-Holocene peatbank development and landscape influences. In peatbank cores from three locations on Litchfield Island (64°46′S; 64°06′W) high-resolution plant macrofossil and geochemical analysis show contrasting ecological and environmental changes. Two peatbanks on the southwest- and west-facing slopes of two separate hills are about 500 years old in contrast to a north-facing peatbank that is 2700 years old. The period from 1350 to 450 calibrated years before present (cal yr BP) at the north-facing peatbank had low accumulation (0.25 mm yr−1, 36 g OM m−2 yr−1), which we interpret as a period of low temperature and increased snow cover. Microclimate differences were amplified by this regional climate cooling, causing the delayed peat initiation on non-equator-facing slopes. Over the last 500 years, the north-facing peatbank had an accumulation rate (0.7 mm yr−1, 76 g OM m−2 yr−1) that was lower than the southwest- and west-facing peatbanks (1-1.4 mm yr−1, 97-110 g OM m−2 yr−1). Microclimate data suggest that slope aspect on Litchfield Island influences soil temperature, snow cover, and water availability that in turn affect growing-season lengths and peat accumulation. Plant macrofossils preserved in the north- and west-facing peatbanks show a centennial-scale pattern of fluctuation in relative abundance of dry-adapted Polytrichum strictum and wetter Chorisodontium aciphyllum mosses. Our results suggest that moss communities responded to external environmental influence, particularly those affecting moisture conditions, while topography and resultant microclimate differences had a strong influence on peat accumulation.