Environmental Science and Engineering Seminar

Wednesday, November 3, 2021
4:00pm to 5:00pm
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Online Event
Impact of atmospheric and oceanic advective feedbacks on the AMOC response to CO2 increase
Oluwayemi Garuba, Pacific Northwest National Laboratory,

The response of the Atlantic Overturning circulation involves a dynamic interplay between the impacts caused by CO2 induced anomalous surface flux components and several feedbacks that arise from the AMOC response itself and its interactions with the atmosphere. These feedbacks determine whether the AMOC stabilizes or collapses in the future. This study aims to understand the relative roles played by atmospheric and oceanic advection feedbacks on the Atlantic Meridional Overturning Circulation (AMOC) response to CO2 quadrupling. Oceanic advection feedbacks are isolated using a tracer decomposition technique that separates ocean buoyancy anomalies that produced by the AMOC response itself, from those that are produced by anomalous surface buoyancy fluxes. The impact of atmospheric feedbacks on the AMOC response and the surface flux component producing the feedback are further isolated using a hierarchy of partially coupled experiments in which atmospheric feedbacks on the AMOC response are suppressed. Analyses of the partially and fully coupled experiments suggest that atmospheric feedbacks have a destabilizing impact on the AMOC, causing the AMOC to nearly shut down in response to the CO2 increase in the fully coupled case, while in the partially-coupled one without these feedback, a weaker but still active AMOC is maintained. The negative temperature advective feedback stabilizes the AMOC in the partially coupled case, while in the fully coupled case, the negative temperature advection feedback is inactive due to the atmosphere's interaction with the AMOC response, allowing the anomalous heat uptake by the ocean to continually weaken the AMOC. No evidence for feedbacks between ocean circulation response and sea ice melt or surface wind changes is found in the experiments

For more information, please contact Bronagh Glaser by email at bglaser@caltech.edu or visit Environmental Science and Engineering.