Remarkable 2023 North Atlantic Ocean Warming

Abstract In 2023 the NOAA Daily Optimum Interpolation Sea Surface Temperature in the Atlantic set new records, peaking above 24. 3°C for the full basin 30°S–60°N and above 25. 3°C for the North Atlantic 0–60°N, both for the first time during the satellite era. Proposed mechanisms include anomalous radiative and thermodynamic surface fluxes, horizontal transport, changing mixed layer thickness and basal entrainment rates. To test these ideas the heat budget of the ocean mixed layer was examined in a numerical simulation. The results show that the anomalous SSTs in the North Atlantic during the summer of 2023 were caused by increased shortwave warming and reduced thermodynamic cooling. In contrast, ocean mean and eddy heat transport convergence and heat exchanges along the mixed layer base dominate only regionally. A second contributor to the record SSTs was the preconditioning of mixed layer temperature following a series of anomalously warm years.