Oceanic memory of tropical cyclones moderates the Kuroshio current

Abstract

Abstract Tropical cyclones (TCs) dramatically disturb the upper ocean and leave subsurface temperature anomalies that persist beyond their lifetimes, representing an oceanic “memory” of TC activity. How this long-term memory affects large-scale ocean circulation remains an open question. Here, we use high-resolution (~0.1°) numerical experiments, in combination with observations, to assess TCʼs impacts on the Kuroshio current. We show that, collectively, Western North Pacific TCs induce subsurface warming to the right of the Kuroshio due to enhanced mixing and downwelling, and cooling along the Kuroshio main axis primarily through upwelling. In the climatological mean, TCs strengthen the upper right flank of the Kuroshio by ~15% while weakening its main axis by ~4% through geostrophic processes, resulting in a net reduction of the Kuroshio’s meridional heat transport by 0.02 ± 0.02 PW. On seasonal and interannual scales, TC-induced changes are comparable to the background variability of the Kuroshio, highlighting the long-term cumulative impacts of TCs on ocean circulations and climate.