Upper ocean changes with hurricane-strength wind events: a study using Argo profiles and an ocean reanalysis

As the Earth’s climate is warming, the intensity and rain rate of tropical cyclones (TCs) is projected to increase. TCs intensify by extracting heat energy from the ocean, hence a better understanding of upper ocean changes with the TC passage is helpful to improve our understanding of air-sea interactions during and after the event. This work uses Argo float observations and the HYCOM ocean reanalysis to describe characteristics of upper ocean changes with hurricane-strength wind events. We study the association of upper ocean changes with the vertical structure of the salinity profile before the event (increasing versus decreasing), as well as the contribution of changes in salinity to upper ocean density changes in each case. Results show that in regions where pre-event salinity increases (decreases) with depth, there is a corresponding statistically significant increase (decrease) in upper ocean salinity. Consistent with previous studies, temperature decreases in both regions. As temperature decreases, upper ocean density increases and the increase is larger where pre-event salinity increases with depth. Changes in upper ocean properties (from Argo and HYCOM) are overall consistent with wind-driven vertical mixing of near-surface waters with colder and higher (or lower) salinity waters below. Resulting changes in ocean stratification have implications for air-sea interactions during and after the event, with potential impacts on weather events that follow.