Millennial-scale Holocene variability in the Arctic-Pacific region from sedimentary proxy records

March 9, 2018
Friday, March 16, 2018 - 1:00pm to 2:00pm
177 Scott Hall, 1090 Carmack Road, Columbus, OH 43210
Masanobu Yamamoto

Masanobu Yamamoto

Associate Professor, Hokkaido University, Japan

Abstract:

Variability of the Holocene climate is investigated based on a number of marine and terrestrial sedimentary records from the North Pacific and adjacent sector of the Arctic. This presentation focuses on the latter region characterized by a complex system of Arctic-Pacific oceanic and atmospheric interactions.
 
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 mineralogical records of the quartz/feldspar (Q/F) and chlorite/illite (C/I) ratios in sediment cores north of the Bering Strait providing insights into the long-term dynamics of the BG circulation and the BSI during the Holocene. The Q/F ratio indicates a long-term decline in the BG strength.
 
We propose that the BG rotation weakened as a result of increasing stability of sea-ice cover at the margins of the Canada Basin, driven by decreasing summer insolation. Millennial to multi-centennial variability in the BG circulation is consistent with fluctuations in solar irradiance. The BSI 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 a decrease in sea-ice concentrations and increase in marine production, as indicated by biomarker concentrations. Multi-century to millennial fluctuations, presumably controlled by solar activity, were also identified in a proxy-based BSI record.
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