The Response of the Upper Ocean to Tropical Cyclones in the South Pacific

Abstract

AbstractConsecutive Argo float profiles are used to observe upper ocean changes resulting from the passage of tropical cyclones (TCs) in the South Pacific between 2001 and 2023. Cross‐sectional composites of the ocean response are produced by normalizing the distance between the profile and cyclone track by the 34‐knot wind radius (R34) of each TC to better resolve the average changes in water properties. Surface cooling in the initial mixed layer (ML) extends from the center to about twice R34 and is stronger to the left of the TC track. Subsurface warming at the base of the ML is observed between 0.4 and 2 R34 on both sides of the track. Strong cooling is observed in a distinct core directly under the TC path, reaching temperature changes of over −1.6°C between 70 and 450 m depth. Significant upwelling of over 40 m displacement is observed within ±0.05 R34, extending to 1,000 m depth. Surface cooling (and subsurface warming at the base of the ML) are positively correlated with wind stress on the ocean from the TC, quantified by the Local Wind Power Dissipation (PDL), and negatively correlated with the energy required to destratify the upper ocean, defined by a Cooling Inhibition index (CI). Subsurface warming is common with low CI but is not observed with high CI. We demonstrate an improved method to analyze Argo float data for measuring TC‐upper ocean interaction in remote oceans and the usefulness of PDL and CI in calibrating the TC‐ocean interaction.