12 500 years of midge-inferred climatic history for interior Alaska

摘要

Freshwater midge fossils were used to reconstruct palaeotemperatures and palaeolake levels for Birch, Jan and Windmill Lakes, interior Alaska. Midge-inferred mean July air temperatures indicate a cold period (10 600 to 9700 14C yr BP, Birch Lake; 10 500 to 10 000 14C yr BP, Windmill Lake) overlapping with the Younger Dryas. Warming is apparent at 9700, 9000 and 11 400 14C yr BP at Birch, Windmill and Jan Lakes, respectively. Inferred temperatures peak at ~10 000 14C yr BP at Jan Lake, and gradually decline throughout the Holocene, possibly indicating an early Holocene Thermal Maximum. Mid-Holocene cooling from 7000 to 6000 14C yr BP at Windmill Lake aligns with Picea glauca decline throughout interior Alaska. Midge-inferred lake levels parallel results of earlier sedimentological research at Birch Lake. Maximum lake depths peak around 12 000, 10 400 and 8000 14C yr BP, synchronous with three midge-inferred cold periods.