Sea level variations in the South China Sea inferred from satellite gravity, altimetry, and oceanographic data

Abstract

Sea level variations (SLVs) can be divided into two major components: the steric SLV and the mass-induced SLV. These two components of SLV in the South China Sea (SCS) are studied by using satellite altimetry, GRACE (Gravity Recovery and Climate Experiment) satellite gravity, and oceanographic data on annual and inter-annual timescales. On the annual timescale, the geographic distribution of mass-induced SLV’s amplitude jointly estimated from altimetry and the ECCO (Estimation of the Circulation and Climate of the Ocean) model agrees very well with that from GRACE. GRACE observes obvious seasonal mass-induced SLV in the SCS with annual amplitude of 2.7±0.4 cm, which is consistent with the annual amplitude of 2.7±0.3 cm estimated from the steric-corrected altimetry. On the inter-annual timescales, the mean SLV in the SCS shows a large oscillation, which is mainly caused by the steric effect. The trend of mean SLV inferred from altimetry in the SCS is 5.5±0.7 mm/yr for the period of 1993–2009, which is significantly higher than the global sea level rise rate of 3.3±0.4 mm/yr in the same period. There is no obvious trend signal in the mass-induced SLV detected from GRACE that indicates the water exchange between the SCS and its adjacent seas and land is in balance within the study period.