Details

Autor(en) / Beteiligte

• Roach, Lettie A.
• Blanchard‐Wrigglesworth, Edward
• Ragen, Sarah
• Cheng, Wei
• Armour, Kyle C.
• Bitz, Cecilia M.

Titel

The Impact of Winds on AMOC in a Fully‐Coupled Climate Model

Ist Teil von

• Geophysical research letters, 2022-12, Vol.49 (24), p.n/a

Ort / Verlag

Washington: John Wiley & Sons, Inc

Erscheinungsjahr

2022

Quelle

Access via Wiley Online Library

Beschreibungen/Notizen

• Here we investigate the role of the atmospheric circulation in the Atlantic Meridional Overturning Circulation (AMOC) by comparing a fully‐coupled large ensemble, a forced‐ocean simulation, and new experiments using a fully‐coupled global climate model where winds above the boundary layer are nudged toward reanalysis. When winds are nudged north of 45°N, agreement with RAPID array observations of AMOC at 26.5°N improves across several metrics. The phasing of interannual variability is well‐captured due to the response of the local Ekman component in both wind‐nudging and forced‐ocean simulations, however the variance remains underestimated. The mean AMOC strength is substantially reduced relative to the fully‐coupled model large ensemble, which is biased high, due to the impact of winds on surface buoyancy fluxes over the subpolar gyre. Nudging winds toward observations also reduces the 1979–2016 trend in AMOC, suggesting that improvement in the representation of the high‐latitude atmosphere is important for projecting long‐term AMOC changes. Plain Language Summary The Atlantic Meridional Overturning Circulation (AMOC) is a system of ocean currents that transports warm water northward near the ocean surface and cold water southward at depth, impacting a number of aspects of global climate. We focus on the strength of this circulation at 26.5°N, the location of an observing system. Coupled climate models, including the one we use here (CESM1), have biases in AMOC strength compared to these observations. We find that constraining CESM1 to observed winds in the mid‐to‐high northern latitudes improves the simulation of AMOC across several metrics. This highlights the importance of winds for various aspects of this oceanic circulation system, including its year‐to‐year variations, mean strength and multi‐year trends. Key Points We nudge winds above the boundary layer toward reanalysis in a fully‐coupled climate model over various spatial domains Constraining winds north of 45°N reduces biases in subpolar gyre surface buoyancy fluxes and Atlantic Meridional Overturning Circulation (AMOC) at 26.5°N Wind‐nudging experiments capture observed phasing of AMOC interannual variability at 26.5°N, but underestimate variability across timescales