Supply of Aged Organic Carbon on the Arctic Chukchi Sea Slope

Abstract

To better understand the carbon cycling dynamics in the Arctic Ocean, which is undergoing rapid declines in sea ice extent and increasing temperatures, we examined sinking particles collected by bottomtethered sediment traps deployed on the Chukchi Sea slope in the Pacific sector of the Arctic Ocean from 2017 to 2021. Sinking particle flux was high during the summer (June？September) and low during the winter (October？May), reflecting the characteristic seasonal variation in primary production. Additionally, two notable phenomena were observed: (a) substantial interannual variations in summertime particle flux and (b) a continuous supply of aged carbon throughout the year. The pronounced interannual variations in summertime particle flux were plausibly associated with the timing of sea ice retreat, subsequent ice­free periods, and associated biogeochemical processes. Aged particulate organic carbon, likely supplied by sediment resuspension and lateral transport, accounted for a considerable fraction of total carbon flux throughout the year, as evidenced by depleted radiocarbon isotopic compositions and relatively high contents of lithogenic material.