A complete energy analysis of ocean background and available potential energy over the past century

After many decades of relative stability, the heat content of the oceans has been increasing at a relatively steady rate since the late 70’s, as confirmed by the analysis of many observational datasets. How global warming affects the available potential energy (APE) of the oceans, however, has received comparatively much less attention, yet is important to assess changes in the strength of wind-driven gyres and Antarctic Circumpolar Current for instance. In this talk, I will contrast the temporal changes over the past century of the APE and background potential energy (BPE) of the oceans based on the analysis of the EN4 dataset, by making use of the most recent local theory of APE. Results show that temporal changes in the BPE mimic that of the ocean heat content estimated in terms of potential temperature or Conservative Temperature. In contrast to the ocean heat content, the total APE of the oceans does not exhibit any marked trend. In this talk, I will discuss how regional APE estimates differ from the global APE estimate, to identify whether global warming has any detectable impact the large-scale ocean circulation features.