Gong et al. (2022) Of Atlantic Meridional Overturning Circulation in the CMIP6 Project

X. Gong, H. Liu, F. Wang, and C. Heuzé (2022). Of Atlantic Meridional Overturning Circulation in the CMIP6 Project. Deep Sea Research Part II: Topical Studies in Oceanography, p.105193, doi: 10.1016/j.dsr2.2022.105193

The Atlantic Meridional Overturning Circulation or AMOC is one of the most famous climate tipping points, even mentioned in disaster movies. But its future is still uncertain, as climate models do not represent it as accurately as we wished.

In this publication, we computed the mean state and variabilities of the AMOC in the latest generation of global climate models used by the IPCC, a.k.a. CMIP6 models, and determine whether the representation of the AMOC has improved since CMIP5. The answer is: it depends…

The CMIP6 models disagree regarding the sign of the current trend in the AMOC, with several even saying that there is no trend. Adapted from Fig.6 of Gong et a. (2022).

The models agree more with each other in terms of AMOC value now in CMIP6 than they did in CMIP5, but disagree when it comes to the variability. More worryingly, while most CMIP5 models had the AMOC weakening currently, CMIP6 models now diverge: half say it weakens, and half say it does not or even increases. And this divergence persists when looking at the climate change scenarios. I personally think that it is not surprising given their inaccurate representation of deep water formation in the North Atlantic (see e.g. my publication [22]), but I am biased.

Download the full-text here.

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