摘要
Based on analysis of Levitus data in the South China Sea (SCS), this note addresses the seasonal feature of the mixed layer and thermocline in the northern SCS in winter, and demonstrates thermocline ventilation during the winter period. The ventilated thermocline is isopycnic layers between sigma 22.0 and 23.5, the other layers beneath is not ventilated yet. The process of thermocline ventilation is accompanied by detrainment water from the mixed layer into the thermocline at the outcropping line and moves to the south. Forced by subduction, the seasonal southward propagating signal also appears in the unventilated thermocline. The horizontal component of the signal propagatesalong the isoline of potential vorticity (PV), in other words, moves around a seasonal PV pool.
Based on analysis of Levitus data in the South China Sea (SCS), this note addresses the seasonal feature of the mixed layer and thermocline in the northern SCS in winter, and demonstrates thermocline ventilation during the winter period. The ventilated thermocline is isopycnic layers between sigma 22.0 and 23.5, the other layers beneath is not ventilated yet. The process of thermocline ventilation is accompanied by detrainment water from the mixed layer into the thermocline at the outeropping line and moves to the south. Forced by subduction, the seasonal southward propagating signal also appears in the unventilated thermocline. The horizontal component of the signal propagates along the isoline of potential vorticity (PV), in other words, moves around a seasonal PV pool.
基金
This work was supported by the National NaturalScience Foundation of China (Grant No. 49636230)
the Major State Basic Research Program (Grant No. 1999043806)
and the Knowledge Innovation Project of the Chinese Academy of Sciences (Grant No. KZCX2-2
