In the tropical Southwest Indian Ocean, the multidecadal sea level decline observed in previous studies from the 1960s to the early 2000s has shifted abruptly to a rapid increase of 4.05 ± 0.56 cm/decade over the past two decades. Sea-level budget analysis indicates that manometric sea level accounts for 41% of this rise. Additionally, 30% of the increase is attributed to steric sea level (SSL) changes in the upper 2000 m, with the SSL rise in the upper 300 m being of secondary importance. In contrast, thermal expansion below the thermocline (300–2000 m) constitutes a significant contributor to SSL changes. Furthermore, the observed reversal in multidecadal sea level trends is likely linked to the SAM-related shift in sea surface winds at the beginning of this century. This study underscores the importance of ocean mass and deeper ocean dynamics in a warming climate, in contrast to previous research that primarily focused on thermal variations above the thermocline.

Sea level,Multidecadal Variability,Tropical Indian Ocean