Three‐Dimensional Temperature Responses to Northward‐Moving Typhoons in the Shallow Stratified Yellow Sea in Summer

• Published in: Journal of geophysical research. Oceans 2022-12, Vol.127 (12), p.n/a
• Main Authors: Liu, Xingchuan, Zhai, Fangguo, Yan, Junjie, Gu, Yanzhen, Wang, Yucheng, Li, Peiliang, Wu, Kejian
• Format: Article
• Language: English
• Subjects: Barotropic currents; Barotropic mode; bottom warming; Climate change; Coastal currents; coastal downwelling; Cold; Cold water; Cold water masses; Cooling; Dimensional changes; Divergence; Downwelling; Dynamics; Geophysics; Global warming; Hurricanes; Marine ecosystems; Maximum winds; Numerical experiments; Numerical simulations; Ocean circulation; Oceans; Resolution; Sea surface; Shelving; Strong winds; Summer; Surface boundary layer; Surface cooling; Surface layers; Temperature changes; Thermocline; Turbulent mixing; typhoon; Typhoons; Upwelling; Vertical mixing; Water masses; Water temperature; Wind; Wind speed; Winds; Yellow Sea
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1029/2022JC019091

Characterized by a sharp thermocline and large cold‐water mass below, the Yellow Sea (YS) in summer is a shelf sea that is one of the most vulnerable to typhoons in the world. With observations and high‐resolution numerical simulations, we investigated the three‐dimensional temperature changes and underlying dynamics during the passage of Typhoon Bavi in August 2020, which was representative of northward‐moving typhoons in the eastern YS. Bavi's cyclonic strong winds caused intense turbulent mixing and Ekman divergence. The intense vertical mixing generated spatially coherent temperature cooling in the surface layer and partly caused temperature warming in the subsurface layer on both sides of the typhoon track. The largest surface cooling and subsurface warming both occurred on the right side of the typhoon track. Wind‐induced Ekman divergence generated two overturning circulation systems zonally across the YS, consisting of upper layer shoreward currents, coastal downwelling, lower layer seaward currents and upwelling on the typhoon track. Downwelling and seaward currents caused temperature warming below the thermocline, especially in the bottom layer. Upwelling shoaled the thermocline, resulting in subsurface cooling on the typhoon track. Additionally, Ekman divergence produced sea surface height minima on the typhoon track, causing strong southward barotropic currents to the left, which subsequently drove strong temperature cooling above the southern bottom slope of the South YS and fast southward movement of the YS Cold Water Mass. Further numerical experiments indicated that the magnitudes of the above changes increased with increasing maximum wind speeds and/or decreasing moving speeds of typhoons. Plain Language Summary Typhoons are the most severe synoptic events on Earth, imposing large influences on physical‐biogeochemical environments in the global oceans and seas. As a marginal shelf sea of the Northwestern Pacific Ocean, the Yellow Sea is characterized by a sharp thermocline and large cold‐water mass in summer. It experienced 1–2 typhoons on average each year in past decades and is projected to undergo more frequent typhoons in a future warming climate. These typhoons have quite different tracks, and moving northward/northeastward in the eastern Yellow Sea is the most common track. Using observations and high‐resolution numerical simulations, we investigated in detail the three‐dimensional temperature changes and underlying dynamics in the Ye