Two centuries of limited variability in subtropical North Atlantic thermocline ventilation

• Published in: Nature Communications
• Main Authors: Druffel, ERM, Goodkin, NF, Hughen, KA, Doney, SC
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2012
• Subjects: North Atlantic; North Atlantic oscillation
• Online Access: https://doi.org/10.1038/ncomms1811; http://hdl.handle.net/10722/151373

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. © 2012 Macmillan Publishers Limited. All rights reserved. link_to_subscribed_fulltext