MIDGE DERIVED PALEOTEMPERATURE RECONSTRUCTIONS FOR THREE SITES FROM YUKON, CANADA AND ALASKA, U.S.A

A model has recently been developed that allows for the reconstruction of paleotemperatures in northwestern North America using subfossil midges as a biological proxy. This model (r2boot=0.82; RMSEP=1.46°C) has been applied to midge data from Antifreeze Pond (Southwest Yukon), Eikland Pond (southwest Yukon) and Birch Lake (central Alaska). Preliminary results show that mean July air temperatures fluctuated by as much as ~5°C around the Pleistocene-Holocene transition (i.e., 12,500 to 9,000 14C yr BP); more high resolution data are being sought to assess whether these fluctuations are synchronous among sites. We reconstruct temperatures ~2°C colder than present from ~9,000 to 8,500 14C yr BP. These data do not support the idea of an early Holocene thermal maximum for this part of Beringia. By 8,500 14C yr BP, temperatures warmed to modern values and have remained relatively stable through to the present.