Comparison of two cases of strong increase in the bottom temperature in the Yellow Sea in winter

Abstract

Mooring observations were carried out on the western slope of the southern Yellow Sea (YS) to observe the Yellow Sea Warm Current (YSWC). Strong increases in the bottom temperature (about 3°C within 1 day) were observed at mooring M5 (shelf break) on 8 January 2007, and at mooring A2 (mid-slope) on 5 December 2008. The strong temperature increase of bottom water at M5 was closely related to the burst of the YSWC. The bottom temperature at mooring A2 increased and decreased alternately from 7 November to 14 December 2008, and the strong increase (about 3°C within 1 day) occurring on 5 December was one of the four rises during that period. The significant semi-diurnal-oscillation during that period indicated that the thermal fronts outlining the Yellow Sea Cold Water Mass (YSCWM) boundary was very close to location A2. The notable rises in the bottom temperature at A2 were associated with bottom eastward currents, while the distinct falls in temperature coincide with bottom westward currents. The distinctive distribution in the bottom temperature associated with the YSCWM and the bottom eastward currents were mainly responsible for the strong increase in the bottom temperature at A2. The variations in the bottom temperature described here are valuable for understanding the time evolution of the YSWC in winter and the YSCWM from late autumn to early winter.