The cold wake of typhoon Chaba (2010)

Abstract

The cold wake of typhoon Chaba (2010) is investigated using an array of temperature sensors connected from the surface to 540 m along the mooring line of an air-sea interaction buoy. Initially, surface forcing caused upper ocean water to entrain across the base of the thermocline, producing a mixed layer cooling and subthermocline warming between 42 and 100 m. However, this warm layer lasted just 12 h before it became overwhelmed by an upwelling of cold water. Observations indicate this upwelling occurred to at least 540 m while further analysis suggests that the actual depth of the ocean response to Chaba was closer to 700 m. This caused a massive reduction in heat content at the mooring site. The sea surface temperature decreased 2.5 °C. Due to the lateness of the season, the ocean didn’t recover to its pre-typhoon state, however, after sixteen days it did match the temperature outside the wake. These observations reveal intricate processes in a cold wake that redistribute heat between the mixed layer, the subthermocline region, and greater depths. This has implications for tropical storm intensity—by altering enthalpy fluxes, and climate—through the lateral and vertical movement of water which modifies the local temperature profile and impacts the transportation of heat to high latitudes.