LINKING 2,000 YEARS OF SEDIMENTATION IN THE WESTERN ARCTIC OCEAN TO AN ATMOSPHERIC TEMPERATURE PROXY RECORD FROM A GLACIAL LAKE IN THE BROOKS RANGE, AK

The delivery of sediment to the Alaskan continental shelf is largely associated with ice drift and wind driven Arctic Ocean circulation patterns that have varied during the Holocene. This study presents a comparison of two continuous, high-resolution proxy records from the western Arctic over the past 2,000 years. Direct correlations were made between marine grain size, related to shifts in depositional mechanisms, and terrestrial atmospheric climate in northern Alaska. To provide variations of sedimentation patterns in the Arctic Ocean (e.g., sea-ice transport, density flows, ocean currents), the grain size distributions were measured in a piston core (HLY02-04 JPC16) from the eastern Chukchi Sea at a higher resolution than previously reported. A revised JPC16 age-depth model was used in this analysis (Darby et al., 2012). The sediment core, collected on the east flank of Barrow Canyon (72.1555°N, 153.50817°W), preserves a record of local variations in sedimentation mechanisms in the Chukchi-Beaufort Seas.

A Varimax-rotated Principle Component Analysis (VPCA) was conducted on JPC16. We inferred three principal components (PCs) of sediment deposition at the core site related to anchor ice, nepheloid flows, and suspension freezing based on variations in grain-size distributions. This interpretation is consistent with previous downcore analysis by Darby et al. (2009). A fourth, less significant mode, is related to resuspension and deposition connected to intermittent suspension. While all components showed increased variability since 200 yr BP, factors related to sea-ice showed the highest positive loadings between 2000-1300 cal yr BP. The high-resolution record of sediment deposition in the Arctic Ocean allowed for direct correlation with the atmospheric climate proxy as recorded by varve thickness in the Brooks Range (Bird et al., 2009). The time interval investigated here shows a significant relationship of marine sea-ice sedimentation with variability in atmospheric temperature (r = 0.7). Additionally, marine sedimentation appears to lag the atmospheric temperature proxy, indicating that temperature is a primary forcing mechanism in sea-ice variation. This analysis suggests that warmer intervals are likely correlated with greater sea-ice melt and favor sedimentation of entrained sediments.