Origins of heat and freshwater anomalies underlying regional decadal sea level trends

Abstract

AbstractRegional sea level changes often differ from global mean changes due to geographic variations in surface fluxes and to changes in ocean circulation. Here we study such regional sea level trends from 1993 to 2004 using a synthesis of observations and an ocean general circulation model. Unlike the global mean, steric changes dominate regional trends with negligible contributions from column‐integrated mass variations. Regional heat and freshwater anomalies underlying steric changes are in turn distinguished between redistribution of pre‐existing anomalies within the ocean and contributions from additional surface fluxes external to the ocean. Internal redistribution accounts for most regional trends but exceptions are found, most notably in the western tropical Pacific Ocean where a warming of external origin dominates the trend. On average, external thermosteric sea level trends are found to be positive in temperate regions while negative at higher latitudes with opposite trends found in halosteric anomalies of external origin.