ENSO Explains the Link Between Indian Ocean Dipole and Meridional Ocean Heat Transport

Indian Ocean meridional heat transport (MHTIO) drives climate and ecosystem impacts, through changes to ocean temperature. Improved understanding of natural variability in tropical and subtropical MHTIO is needed to contextualize observations and future projections. Previous studies suggest that El Nino-Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD) can drive variability in MHTIO. However, it is unclear whether internally generated IOD can drive variability in MHTIO, or if the apparent relationship between IOD and MHTIO arises because both are modulated by ENSO. Here, we use a model experiment which dynamically removes ENSO to determine the role of internally forced IOD on MHTIO. We find that IOD is not linked to anomalies in MHTIO. Nevertheless, internal atmospheric variability drives significant MHTIO variability. There is little evidence for decadal or multidecadal variability in MHTIO, suggesting this may be a region where an anthropogenic trend rises above the level of internal variability sooner.