Sea Surface Temperature–Salinity Covariability and Its Scale-Dependent Characteristics

Abstract

Sea surface temperature and salinity (SST/SSS) are critical to understanding the ocean's role in the climate system. Because seawater density is controlled by temperature and salinity, characterizing the relationship between these two variables is particularly important for oceanography, climate science and other related fields. By analyzing observational data, we provide the first global picture of covariability between SST and SSS and associated physical processes at interannual timescales. A notable feature of such SST-SSS covariability is its distinct spatial-scale dependence; at small spatial scales (<1,000 km), their covariability is attributed to fluctuations in ocean currents and the associated heat and salt transport, whereas large-scale covariability result from combinations of changes in local atmospheric conditions and large-scale ocean circulations. It is found that the current generation of climate models underestimate such distinct SST–SSS covariations, suggesting that physical processes involving in variations of these variables are not faithfully represented as observed.