Improving global and regional ocean heat content by consistently combining GRACE gravity, satellite altimetry and Argo profile observations in a joint inversion framework

Abstract. The current energy imbalance at the top of atmosphere and corresponding heating of the Earth system is the main driver of steric sea level change through ocean heat uptake (OHU). A global constant heat capacity factor is commonly applied to retrieve ocean heat content (OHC) from observed ocean-average steric sea level. We propose an extension to this methodology, which focuses on the leading modes of steric variability, which are derived from an ocean model and fitted to GRACE gravity, satellite altimetry and in situ Argo observations within a joint inversion framework. These modes are utilized to obtain data driven OHC estimates by establishing a mapping between modeled OHC and steric sea level, and rescaling each mode individually based on observed steric sea level change. On global scales for the period 2005-01 till 2024-12, our OHU results (0.62 W/m²) agree well with a variety of published datasets from in situ Argo data, model reanalyses and space-geodetic approaches as well as independent estimates from the CERES project. At basin scales, we demonstrate the global OHU to be driven mainly by warming of the Pacific Ocean (0.23 W/m²), followed by contributions from the Indian (0.20 W/m²) and Atlantic (0.13 W/m²) oceans. Minor contributions are found from the Arctic Ocean (0.01 W/m²), the Southern Ocean (0.02 W/m²) and the residual ocean (0.03 W/m²). Our results also indicate a shift from dominant heating in the Indian Ocean driven by heat transport from the Pacific Ocean, e.g. found during 2005–2015, towards a more evenly distributed global ocean heat budget.