The Increase in Global Ocean Heat Content and Favorable Conditions for Tropical Cyclone Rapid Intensification: Accounting for El Niño

Ocean heat content (“OHC”)—the heat energy within the ocean integrated to a reference depth—has physical drivers spanning spatial and temporal scales, including seasonality, El Niño / Southern Oscillation (ENSO), and others. The present article investigates changes in OHC100 during the period 1994-2020 using GLORYS12 monthly-averaged ocean reanalysis. OHC100 – ENSO correlation patterns are explored to glean insights about the oceanic mechanisms that facilitate ENSO’s global teleconnections. After extracting known seasonality and ENSO signals using the Oceanic Niño Index (ONI), the OHC100 residual is analyzed to investigate multidecadal drivers of OHC100. Lagged ENSO – OHC100 correlations (±12 months) reveal basin-scale oscillations in the sign of ENSO influence likely attributable to Rossby waves. OHC100 is increasing globally (in total 2.4x1022 J decade-1), with greatest increases near western boundary currents (WBCs). Some regions are decreasing, notably the Atlantic Main Development Region (MDR) for tropical cyclones (TCs). Correlations and multidecadal variability in the OHC100 tendency (OHCT) and zonal and meridional advections of OHC100 (ZAO and MAO) support the hypothesis that upper-ocean dynamics mediate ENSO teleconnections as well as exert an independent control of OHC100 variability. Local increases in OHC100 would support observed TC rapid intensification irrespective of ENSO phase as the TC-supporting region expands.