Steric Changes Associated With the Fast Sea Level Rise in the Upper South Indian Ocean

Abstract

Abstract This study provides a quantitative assessment of steric changes associated with sea level rise in the upper (0–500 m) South Indian Ocean (SIO) during 1993–2017, using the latest ocean state estimate of Estimating the Circulation and Climate of the Ocean (ECCO) combined with in‐situ observations from Argo. Both the observations and ECCO estimate show a sea level rise in the low‐latitude (0°–30°S) SIO that is faster than its South Pacific and South Atlantic counterparts by a factor at least two. Much of this fast sea level rise is due to warming and freshening of the upper ocean, with no significant contribution from the deeper layers (>500 m). We emphasize the importance of halosteric effect, whose contribution to sea level rise is comparable with that of thermosteric effect in the eastern basin. On interannual time scale, up to 90% of the region's sea level variability can be explained by steric changes that in turn are dominated by upper ocean convergence.

Keywords

• sea level rise
• upper‐ocean warming
• upper‐ocean freshening
• South Indian Ocean