Two centuries of limited variability in subtropical North Atlantic thermocline ventilation.

Abstract

Ventilation and mixing of oceanic gyres is important to ocean-atmosphere heat and gas transfer, and to mid-latitude nutrient supply. The rates of mode water formation are believed to impact climate and carbon exchange between the surface and mid-depth water over decadal periods. Here, a record of (14)C/(12)C (1780-1940), which is a proxy for vertical ocean mixing, from an annually banded coral from Bermuda, shows limited inter-annual variability and a substantial Suess Effect (the decrease in (14)C/(12)C since 1900). The Sargasso Sea mixing rates between the surface and thermocline varied minimally over the past two centuries, despite changes to mean-hemispheric climate, including the Little Ice Age and variability in the North Atlantic Oscillation. This result indicates that regional formation rates of sub-tropical mode water are stable over decades, and that anthropogenic carbon absorbed by the ocean does not return to the surface at a variable rate.

DOI: 10.1038/ncomms1811

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@article{Goodkin2012TwoCO, title={Two centuries of limited variability in subtropical North Atlantic thermocline ventilation.}, author={Nathalie Fairbank Goodkin and Ellen R. M. Druffel and Konrad A . Hughen and Scott C. Doney}, journal={Nature communications}, year={2012}, volume={3}, pages={803} }