Holocene climate inferred from oxygen isotope ratios in lake sediments, central Brooks Range, Alaska

Analyses of sediment cores from two lakes in the central Brooks Range provi de temperature and moisture balance information for the past similar to 850 0 cal yr at century-scale resolution. Two methods of oxygen isotope analysi s are used to reconstruct past changes in the effective moisture (precipita tion minus evaporation) and temperature. Effective moisture is inferred fro m oxygen isotope ratios in sediment cellulose from Meli Lake (area similar to0.13 km(2), depth 19.4 m). The lake has a low watershed-to-lake-area rati o (7) and significant evaporation relative to input. Summer temperature shi fts are based on oxygen isotope analyses of endogenic calcite from Tangled Up Lake (area similar to0.25 km(2), depth 3.5 m). This basin has a larger w atershed-to-lake-area ratio (91) and less evaporation relative to input. Se diment oxygen isotope analyses from the two sites indicate generally more a rid conditions than present prior to similar to 6000 cal yr B.P. Subsequent ly, the region became increasingly wet. Temperature variability is recorded minimally at centennial scale resolution with values that are generally co ol for the past similar to 6700 cal yr. The timing and direction of climate variability indicated by the oxygen isotope time series from Meli and Tang led Up lakes are consistent with previously established late Holocene glaci er advances at similar to 5000 cal yr B.P. in the central Brooks Range, and high lake-levels at Birch Lake since similar to 5500 cal yr B.P. This uniq ue use of oxygen isotopes reveals both moisture balance and temperature his tories at previously undetected high-resolution temporal scales for norther n Alaska during the middle to late Holocene. (C) 2001 University of Washing ton.