Hydrological cycle amplification reshapes warming-driven oxygen loss in the Atlantic Ocean

The loss of oxygen from the ocean due to warming is not ubiquitous. In the Atlantic Ocean above 1 km depth, there is oxygen loss at subpolar latitudes, but there has been no oxygen loss or gain in the subtropics over the past six decades. Here we show that the amplification of the hydrological cycle, a response to climate change that results in a ‘salty-get-saltier, fresh-get-fresher’ sea surface salinity pattern, influences ocean ventilation and introduces a spatial pattern in the rate of climate change-driven oxygen loss in an Earth system model. A salinification enhances ventilation of (already salty) mode waters that outcrop in the subtropics and opposes warming-driven oxygen loss, while a freshening reduces ventilation of (already fresh) deep waters that outcrop at subpolar latitudes and accelerates oxygen loss. These results suggest that climate change introduces patterns of oxygenation through surface salinity changes, key to understanding observed and future regional changes.