North Atlantic sea level budget revisited

Based on satellite altimetry, GRACE space gravimetry and Argo-based steric data down to 2000 m, recent studies have shown that the North Atlantic sea level budget (i.e., altimetry-based sea level minus sum of components) of the past two decades is not closed, with strong regional residuals in the North Atlantic. In this study, we revisit the North Atlantic sea level budget, using satellite altimetry, GRACE and GRACE-FO data, different Argo products and an ocean reanalysis (CIGAR) over the 2004–2022 time span. The ocean reanalysis is used to estimate the manometric contribution, an alternative to using GRACE data, as well as the deep ocean contribution to the sea level budget, not yet fully sampled by Argo. Analyzing different data sets allows us to assess their impact on the previously reported non-closure of the North Atlantic sea level budget. We first find that using the CIGAR ocean reanalysis-based manometric component significantly reduces the residuals of the North Atlantic sea level budget compared to GRACE. We also find that accounting for the deep ocean (below 2000 m) thermal expansion (using the CIGAR reanalysis) allows for reducing 90 % the North Atlantic budget residuals when using CIGAR for the manometric component. The budget can be closed within the data uncertainties when CIGAR manometric and full depth steric sea level are included.