Salinity Contribution to Regional Sea Level Trends in the Tropical Southwestern Pacific Ocean Over 2014–2023

Abstract Steric sea‐level has been identified as the main driver of regional sea‐level trends. Altimetry‐based spatial patterns vary as a function of space and time. Thermosteric (temperature‐related) sea‐level trends have generally been found to be more important than the halosteric (salinity‐related) trends. Using satellite altimetry data together with an Argo‐based gridded product, we find a negative trend in halosteric sea‐level in the Tropical Southwestern Pacific Ocean over 2014–2023, which attenuates thermosteric sea‐level trends during this period. This striking negative halosteric trend is associated with salinization of the upper 400 m, which is related to both salinity anomalies on isopycnal surfaces and to the vertical movement of isopycnals. This salinization can be explained by a precipitation deficit and by a remote contribution from wind‐driven wave propagation. Our results highlight the importance of salinity changes when interpreting satellite altimetry data.