Global Estimate of Tropical Cyclone-Induced Diapycnal Mixing and Its Links to Climate Variability

A mixing length theory which considers the impact of TC characters and upper ocean stratification, is used to estimate the tropical cyclone (TC) induced diapycnal diffusivity, and investigate the trend, interannual and interdecadal variability of TC-induced diapycnal diffusivity in the globe and each basin. The annual mean climatology of the TC-induced diapycnal diffusivity is consistent with previous research, with maximum values in the Western North Pacific (WP) ranging from 0.05 cm²/s up to 1 cm²/s. The trends of TC-induced diapycnal diffusivity exhibit great inter-basin differences, which are not only related with TC itself, but also the ocean stratification. On the interannual timescales, El Niño and Southern Oscillation (ENSO) can modulate the variability of TC-induced diapycnal diffusivity in the globe by regulating the ocean stratification rather than TC intensity, because the impacts of ENSO on TC intensity in each basin cancel out each other. As for each basin, ENSO can affect TC-induced diapycnal diffusivity mainly by regulating the variability of TC intensity. In addition, the relationship of TC-induced diapycnal diffusivity with dominant climate modes such as Pacific Decadal Oscillation (PDO) and North Atlantic Oscillation (NAO) may be interactive on the interdecadal timescales, especially in the areas which are significantly influenced by PDO and NAO, such as WP, Eastern North Pacific and North Atlantic. We anticipate that these results can provide insights into the variability and physical mechanisms of TC-induced diapycnal mixing.