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The Role of Oceanic and Atmospheric Feedbacks in the Response of the Atlantic Meridional Overturning Circulation to a CO2 Increase

Presentation Date
Wednesday, October 14, 2020 at 2:41pm
Virtual Meeting



The Atlantic Meridional Overturning Circulation (AMOC) plays an important role in the climate system: it redistributes large amounts of heat throughout the Atlantic Ocean, and its ability to sequester heat from the atmosphere mitigates global warming. Its projected slowdown in response to continued anthropogenic forcing is hence a matter of concern. The strength and stability of the AMOC is governed by several feedbacks involving the advection of heat and salt from the subtropics to the subpolar North Atlantic, as well as interactions with the atmosphere. Here we use a novel approach to examine the role of these feedbacks in the response of the AMOC to a quadrupling of CO2 in the CESM1 Earth system model. A tracer decomposition technique is used to distinguish the components of salinity and temperature anomalies that are forced by anomalous surface fluxes (surface-driven anomalies), or by changes in the AMOC itself (circulation-driven anomalies). Then we perform a partially-coupled experiment in which atmospheric feedbacks on the circulation-driven temperature changes are suppressed. We will discuss how the advective and atmospheric feedbacks conspire to shut down the AMOC in the fully-coupled case, while they stabilize the AMOC in the partially-coupled case.

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