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Abstract:
Approximately 90% of Earth’s energy imbalance is absorbed by the oceans. Therefore, Ocean Heat Content (OHC) and its time-derivative, Ocean Heat Uptake (OHU), are key parameters for monitoring planetary energy imbalance. Several approaches for estimating OHC and OHU have been proposed, each employing a different combination of in-situ and remote observations and models. Published estimates of OHU for the satellite oceanography era range between ~0.5 and ~1.0 Wm-2 with corresponding uncertainties of a few tenths of Wm-2. Although the range of OHU estimates has narrowed, the spread remains large relative to its absolute value due to persistent, potentially incompletely known, observational uncertainties or derived products. Here we report on new OHU estimates for 1992-2022 from the latest global ocean state estimate from the Estimating the Circulation and Climate of the Ocean (ECCO) Consortium. ECCO estimates are dynamically self-consistent and strictly obey the mass, energy, and momentum conservation principles over the full estimation period. The ECCO estimate is constrained in a least-squares sense to in-situ data, including Argo profiles, and remote ocean and marine-ice observations, including sea-level from altimetry and ocean mass from GRACE(-FO). We find time-mean OHU of 0.59 Wm-2 for the upper 2000 m and 0.60 Wm-2 for the full-depth ocean, with significant seasonal and interannual variability. Although sea-level and energy budgets are closed in ECCO estimates, the model does not (and cannot) reproduce all observational data. We describe model-data differences and their consequences in the context of other (often larger) OHU estimates derived from geodetic and other approaches.
