Rapid ocean mixing observed by an underwater glider during Typhoon Soulik over tidally dominated and highly stratified waters west of Jeju Island, Korea

Abstract

The Yellow Sea is highly stratified during the summer months with warm surface water, typically warmer than 25C and an extensive area of cold bottom water less than 15C. Similar to hurricanes along the US east coast this highly stratified region is frequently impacted by typhoons in summer. Unlike the US east coast, strong tidal currents off the Korean Peninsula often reach 1.2 m/s with maximum tidal ranges of 3 m. Recent studies off the US east coast have identified the essential ocean processes responsible for ahead of eye center cooling and its feedback on rapid storm deintensification. During Typhoon Soulik, the glider observed rapid cooling. Surface temperatures dropped 11C, bottom temperature increased by 3C, and a dramatic deepening of the pycnocline from 30 to 70 meters depth. This rapid mixing coincided with a tidal transition after hours of sustained winds and waves with limited mixing and cooling. In this study we present a preliminary analysis of Typhoon Soulik and its interaction with this tidally dominated and highly stratified coastal ocean.