Surface predictor of overturning circulation and heat content change in the subpolar North Atlantic

Abstract

Abstract. The Atlantic Meridional Overturning Circulation\xa0(AMOC) impacts\nocean and atmosphere temperatures on a wide range of temporal and spatial\nscales. Here we use observational datasets to validate model-based\ninferences on the usefulness of thermodynamics theory in reconstructing AMOC\nvariability at low frequency, and further build on this reconstruction to\nprovide prediction of the near-future\xa0(2019–2022) North Atlantic state. An\neasily observed surface quantity – the rate of warm to cold transformation\nof water masses at high latitudes – is found to lead the observed AMOC at\n45 ∘ \u2009N by 5–6\xa0years and to drive its 1993–2010\xa0decline and its\nongoing recovery, with suggestive prediction of extreme intensities for the\nearly\xa02020s. We further demonstrate that AMOC variability drove a\nbi-decadal warming-to-cooling reversal in the subpolar North Atlantic before\ntriggering a recent return to warming conditions that should prevail at\nleast until\xa02021. Overall, this mechanistic approach of AMOC variability and its impact on ocean temperature brings new key aspects for understanding and\npredicting climatic conditions in the North Atlantic and beyond.