Articles | Volume 13, issue 9
Research article
08 Sep 2017
Research article |  | 08 Sep 2017

Holocene dynamics in the Bering Strait inflow to the Arctic and the Beaufort Gyre circulation based on sedimentary records from the Chukchi Sea

Masanobu Yamamoto, Seung-Il Nam, Leonid Polyak, Daisuke Kobayashi, Kenta Suzuki, Tomohisa Irino, and Koji Shimada

Abstract. The Beaufort Gyre (BG) and the Bering Strait inflow (BSI) are important elements of the Arctic Ocean circulation system and major controls on the distribution of Arctic sea ice. We report records of the quartz ∕ feldspar and chlorite ∕ illite ratios in three sediment cores from the northern Chukchi Sea, providing insights into the long-term dynamics of the BG circulation and the BSI during the Holocene. The quartz ∕ feldspar ratio, interpreted as a proxy of the BG strength, gradually decreased during the Holocene, suggesting a long-term decline in the BG strength, consistent with an orbitally controlled decrease in summer insolation. We propose that the BG rotation weakened as a result of the increasing stability of sea-ice cover at the margins of the Canada Basin, driven by decreasing insolation. Millennial to multi-centennial variability in the quartz ∕ feldspar ratio (the BG circulation) is consistent with fluctuations in solar irradiance, suggesting that solar activity affected the BG strength on these timescales. The BSI approximation by the chlorite ∕ illite record, despite a considerable geographic variability, consistently shows intensified flow from the Bering Sea to the Arctic during the middle Holocene, which is attributed primarily to the effect of higher atmospheric pressure over the Aleutian Basin. The intensified BSI was associated with decrease in sea-ice concentrations and increase in marine production, as indicated by biomarker concentrations, suggesting a major influence of the BSI on sea-ice and biological conditions in the Chukchi Sea. Multi-century to millennial fluctuations, presumably controlled by solar activity, were also identified in a proxy-based BSI record characterized by the highest age resolution.

Short summary
Based on mineral records from the northern Chukchi Sea, we report a long-term decline in the Beaufort Gyre (BG) strength during the Holocene, consistent with a decrease in summer insolation. Multi-centennial variability in BG circulation is consistent with fluctuations in solar irradiance. The Bering Strait inflow shows intensification during the middle Holocene, associated with sea-ice retreat and an increase in marine production in the Chukchi Sea, which is attributed to a weaker Aleutian Low.