Ocean heat uptake and interbasin redistribution driven by anthropogenic aerosols and greenhouse gases

Anthropogenic aerosols and greenhouse gases have played important roles in modulating the storage and distribution of heat in oceans since the industrial age. Here we isolate and quantify the effects of both using coupled climate model simulations. We show that, relative to the pre-industrial ocean, the Southern Ocean imports heat from the Indo-Pacific Ocean but exports heat into the Atlantic Ocean in response to anthropogenic aerosols. Ocean heat uptake diminishes in the subpolar Atlantic. Alterations in ocean circulation and temperature have a weak compensation in contributing to interbasin heat exchange. Consequently, interbasin heat exchange contributes comparably to ocean heat uptake changes to modifying the stored heat in the Atlantic and Indo-Pacific. The greenhouse-gas-associated changes are the opposite of the aerosol-associated changes. Anthropogenic greenhouse gases promote the ocean heat uptake in the subpolar Atlantic and allow the Southern Ocean to import heat from the Atlantic but export heat to the Indo-Pacific. The cause of this ocean heat redistribution is distinct from the aerosol-forcing scenario, seeing that ocean circulation effects are strongly offset by temperature shifts. Accordingly, interbasin heat exchange is much less important than ocean heat uptake changes for greenhouse-gas-associated ocean heat storage. Our results suggest that the aerosol-driven changes in ocean circulations and associated interbasin heat transports are more effective in altering oceanic heat distribution than those driven by globally increasing greenhouse gases.