HOLOCENE PALEOENVIRONMENTAL CHANGE IN EASTERN BERINGIA

Holocene records of past environmental change in the interior of Alaska have been derived from multiproxy analyses of lake sediment cores, with dating control based on radiocarbon and 210Pb methods. In the interior regions of Alaska and adjacent Yukon Territory, estimates of past changes in precipitation are based on lake-level reconstructions coupled with hydrologic modeling. Similar temporal patterns of lake-level changes are observed at more than 10 interior sites, suggesting responses to regional climatic changes. A complex series of severe lake-level changes occurred during the deglacial to early Holocene period. Lakes were very low or dry for extended periods prior to about 12,000 ¹⁴C yr BP. Lakes rose rapidly following this arid interval, but were low again between 11,600 - 10,600 ¹⁴C yr BP. Following another rise, lakes were again low or dry in the earliest Holocene. A significant rise in lake-levels occurred ~8,500 - 9,000 ¹⁴C yr BP, though a trend of increasing lake-levels continued though the mid-Holocene (~ 4,800 ¹⁴C yr BP). Hydrologic models suggest that precipitation was 50 - 75% less than modern during the arid period prior to 12,000 ¹⁴C yr BP, and 25 - 45% less than modern during the early Holocene. In this semi-arid region, precipitation is an important control on ecosystem and biogeochemical processes.