Emergence of deep ocean warming from a sea level budget approach

Assessments of the global mean sea level (GMSL) budget over the satellite altimetry era (since the early 1990s) have concluded that the GMSL budget is closed within data uncertainties until 2016. However, studies have shown that since then, the sea level budget based on Argo data down to 2000 for the thermosteric contribution is no more closed. Using an ocean reanalysis with no altimetry data assimilation, we show that accounting for deep ocean thermosteric contribution (below 2000 m, not sampled by Argo) allows the GMSL budget to be closed since 2016. This finding reveals that deep ocean warming has started to emerge and that ocean heat uptake has now reached several regions of the deep-water formation, notably the northwestern Atlantic Ocean and areas around Antarctica.