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Abstract:
Geodetic observations have a wide range of applications that are vital for quantifying and understanding global climate change. Here, we provide an update on the combination of total sea level (from altimetry) and ocean mass (from GRACE/GRACE Follow-On) to estimate Earth’s Energy Imbalance (EEI) from 2002 through 2023, using the so-called sea level budget approach. Ocean heat uptake (OHU) poses a vital constraint on EEI and its uncertainty, as over 90% of planetary heat uptake occurs in the oceans. Using recent geodetic observations, geophysical corrections, and new estimates of the ocean’s expansion efficiency of heat, we translate steric sea-level change, the difference between total sea-level and ocean-mass change, into a global OHU of 0.88+/-0.24 Wm-2 over the 2006-2020 time period. As has also been noted by others, subtracting the 0-2000m Argo-based OHU estimate from the geodetic OHU implies a residual that is likely too large to be attributed to the deep ocean only. We discuss regional sea level budgets (e.g., in the South Pacific) and compare the geodetic OHU with select deep ocean hydrographic surveys to assess the extent and realism of deep or residual ocean warming.
