An extreme warm event of the Yellow Sea Cold Water Mass in the summer of 2007 and its causes

Abstract

A high-resolution numerical model based on the Regional Ocean Modeling System (ROMS) was used to simulate the Yellow Sea Cold Water Mass (YSCWM) and revealed an extreme warm event of the YSCWM in the summer of 2007. This event was also captured by in situ observations. In August 2007, the average temperature of the YSCWM was above 1 °C higher than its climatological mean. The unusually-high temperature anomaly of the YSCWM could trace back to the winter 2006–07. Heat budget of the Yellow Sea deep water (YSDW) below 50 m depth, indicated that vertical mixing, rather than advection, in the winter 2006–07 played a crucial role in the generation of the warm event. With the seasonal thermocline disappearing in the winter 2006–07, a weak vertical mixing effect due to weak wind speeds and high heat content in the Yellow Sea upper water (YSUW) above the YSDW, together with strong advection effect, caused the YSDW to become quite warmer than its climatological mean. After that, the seasonal thermocline above the YSDW formed again and the warm YSDW persisted until the summer of 2007, resulting in the extreme warm event of the YSCWM.