Accelerated North Atlantic surface warming reshapes the Atlantic Multidecadal Variability

Abstract

Observed North Atlantic sea-surface temperatures are modulated by a recurrent alternation of anomalously warm and cold interdecadal phases known as Atlantic Multidecadal Variability. Here we use observations and a multi-model ensemble of climate simulations to demonstrate an ongoing acceleration of North Atlantic surface warming, which implies a smaller contribution of the Atlantic Multidecadal Variability to 21st century North Atlantic sea-surface temperature anomalies than previously thought. Future projections of the Atlantic Multidecadal Variability from realistic climate simulations are poorly constrained, yet a relaxation to a neutral phase by the mid-21st century emerges as the most probable evolution of the Atlantic Multidecadal Variability. In the simulations, the mitigating effects of a less likely upcoming cold phase of the Atlantic Multidecadal Variability are overwhelmed by fast North Atlantic surface warming, which is robustly projected to persist in upcoming decades independent of emission scenarios. Sustained North Atlantic surface warming is therefore expected to continue in the near future. Warming of North Atlantic sea surface temperatures is accelerating, and projected to be stronger than natural variability associated with the Atlantic Multidecadal Variability, according to an analysis of climate model simulations.