HOLOCENE CLIMATE RECONSTRUCTION FOR THE BERING SEA REGION FROM PEAT OXYGEN ISOTOPES, ST. MATTHEW ISLAND, ALASKA

Stable oxygen isotopes from peat cellulose are becoming a more widely used proxy to reconstruct paleoclimate and paleoenvironmental conditions. Recent studies using peat moss demonstrate that oxygen isotope values can reflect regional-to-local humidity, hydrology, temperature, and vapor source, which characterize past patterns of atmospheric circulation and modes of climate variability. In addition to plant macrofossils and pollen, bulk peat and species-specific peat moss oxygen isotopes from St. Matthew Island document Bering Sea hydroclimate variability for the past 5000 years. Brown moss macrofossils indicate enhanced groundwater flow prior to 2500 cal yr BP, which were followed by a change to sedge and Sphagnum dominance. The pollen record indicates forb tundra vegetation, followed by an increase in Alnus and Salix pollen after ~2000 cal yr BP, although these shrubs were likely not present on the island during the Holocene. Preliminary stable oxygen isotope values indicate a positive shift by ~6‰ by 3000 cal yr BP. A prominent decline of ~10‰ occurred from ~1500-1000 cal yr BP, with the most depleted values centered at 1200 cal yr BP, roughly coinciding with the Medieval Climate Anomaly (1250-950 cal yr BP). These patterns are similar to changes in North Pacific ocean-atmosphere dynamics documented by lake and ice oxygen isotope records from the Gulf of Alaska region. By representing the first peat oxygen isotope record from the Bering Sea region, these results will contribute to a better understanding of links between past ocean-atmosphere circulation patterns, external forcing, and peatland dynamics.