The Impact of Salinity Perturbations on the Future Uptake of Heat By the Atlantic Ocean

Abstract:

Ocean uptake of anthropogenic warming is a key factor in determining the rate of surface climate change and sea-level rise. There is considerable uncertainty in the detail of how the surface freshwater forcing of the ocean will change, which may significantly impact ocean heat uptake. Here, we investigate this by adding either freshwater or salt to the Atlantic in global climate model simulations, simultaneously imposing an idealised atmospheric CO₂ scenario. Whilst circulation changes are roughly equal and opposite for salt and freshwater perturbations, freshwater perturbations cause a net increase in Atlantic heat content but salt perturbations produce only small changes in heat content compared to the baseline CO₂ scenario. Approximately 15% of the increase in Atlantic heat content in our climate change experiments is due to changes in the Atlantic overturning circulation. The processes active in our model appear robust, although their net result depends on model- and experiment-dependent details.