Formal detection and attribution studies have used observations and climate models to identify an anthropogenic warming signature in the upper (0–700 m) ocean 1, 2, 3, 4. Recently, as a result of the so-called surface warming hiatus, there has been considerable interest in global ocean heat content (OHC) changes in the deeper ocean, including natural and anthropogenically forced changes identified in observational5, 6, 7, modelling 8, 9 and data re-analysis 10, 11 studies. Here, we examine OHC changes in the context of the Earth's global energy budget since early in the industrial era (circa 1865–2015) for a range of depths.
We rely on OHC change estimates from a diverse collection of measurement systems, including data from the nineteenth-century Challenger expedition12, a multi-decadal record of ship-based in situ mostly upper-ocean measurements, the more recent near-global Argo floats profiling to intermediate (2,000 m) depths13, and full-depth repeated transoceanic sections5. We show that the multi-model mean constructed from the current generation of historically forced climate models is consistent with the OHC changes from this diverse collection of observational systems.
Our model-based analysis suggests that nearly half of the industrial-era increases in global OHC have occurred in recent decades, with over one third of the accumulated heat occurring below 700 m and steadily rising.
Simulated and observed industrial-era changes in global OHC for three depth ranges (0–700 m, 700–2,000 m and >2,000 m).
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