Estimate of the steric contribution to global sea level rise from a comparison of the WOCE one-time survey with 2006-2008 argo observations

Abstract

It is well known from observations by altimetric satellites (predominantly TOPEX/Poseidon and Jason-1) that global sea level is rising. What is less well known is exactly how the observed sea level rise is partitioned between a steric contribution (sea level rising because of changes in ambient temperature and salinity) and a contribution arising from the addition of new water mass to the oceans. Strictly speaking, such a separation is not possible because of the non-linearity in the equation of state for sea water, but in practice the non-linearities are sufficiently small to allow this separation as a very good first approximation.A careful comparison of the World Ocean Circulation Experiment (WOCE) one-time survey with recent observations by the Argo array indicate a steric component to sea level rise of 2.2 mm y -1 between the early 1990s and 2006 to 2008. This is a significantly larger rise rate than previously estimated and, along with recent estimates of melt rate from ice sheets, is in much closer agreement with the total rise rate as reported by altimetric satellites, 3.2 ± 0.4 mm y -1 over this period.