Late Holocene moisture variability in Arctic Alaska from chitin δ18O

Abstract

Amplified warming in the Arctic has resulted in reduced sea-ice extent, which can impact regional climate dynamics. Elucidating past moisture variability in response to changing temperatures and sea-ice conditions can offer insight into how anthropogenic climate change may impact Arctic areas such as the Alaskan North Slope in the future. We contribute a new high-resolution record of precipitation variability from Lake GTH90 located on the Alaskan North Slope. This new record is based on the isotopic composition of chitin from lake sediments and adds to a growing suite of Late Holocene climate records in northern Alaska. An overall decrease in δ¹⁸O values from 3.5 cal. ka BP to present at Lake GTH90 is coincident with Neoglacial cooling associated with a millennial-scale decrease in summer insolation. The highest and most variable δ¹⁸O values occur between 3.5 and 2.6 cal. ka BP and the lowest values are centred around 0.5 cal. ka BP, indicating isotopically depleted precipitation during the Little Ice Age. Isotopic variability in our record on centennial timescales is consistent with temporal variability in sea-ice extent in the Arctic Ocean in the Late Holocene, suggesting that periods of high sea-ice extent inhibited Arctic moisture sources and long-distance moisture transport from the North Pacific became dominant. In addition, we compare regional records to evaluate how shifts in the strength and position of the Aleutian Low may have also contributed to Late Holocene precipitation in this region.