Drivers and distribution of global ocean heat uptake over the last half century

Since the 1970s, the ocean has absorbed almost all of the additional energy in the Earth system due to greenhouse warming. However, sparse observations limit our knowledge of where ocean heat uptake (OHU) has occurred and where this heat is stored today. Here, we equilibrate a reanalysis-forced ocean-sea ice model, using a spin-up that improves on earlier approaches, to investigate recent OHU trends basin-by-basin and associated separately with surface wind trends, thermodynamic properties (temperature, humidity and radiation) or both. Wind and thermodynamic changes each explain similar to 50% of global OHU, while Southern Ocean forcing trends can account for almost all of the global OHU. This OHU is enabled by cool sea surface temperatures and sensible heat gain when atmospheric thermodynamic properties are held fixed, while downward longwave radiation dominates when winds are fixed. These results address long-standing limitations in multidecadal ocean-sea ice model simulations to reconcile estimates of OHU, transport and storage.

Automated summary

Since the 1970s, the ocean has absorbed most of the additional energy caused by greenhouse warming, but limited observations have hindered our understanding of where this heat is stored. In this study, a reanalysis-forced ocean-sea ice model is used to investigate ocean heat uptake trends in different basins. It is found that wind and thermodynamic changes each explain about 50% of global ocean heat uptake, while the trends in the Southern Ocean can account for almost all of the global ocean heat uptake. This study addresses long-standing limitations in ocean-sea ice model simulations and provides valuable insights into estimates of ocean heat uptake, transport, and storage.