南极绕极流区中尺度涡动动能年际变化和转换机制

INTERANNUAL VARIABILITY OF THE MESOSCALE EDDY KINETIC ENERGY IN THE ANTARCTIC CIRCUMPOLAR CURRENT REGION AND ITS TRANSLATION MECHANISM

提要采用多种资料研究南大洋南极绕极流(Antarctic Circumpolar Current,ACC)区中尺度涡的年际变化规律及机制。通过分析网格化融合卫星海洋资料AVISO(Archiving,Validation and Interpretation of Satellites Oceanographic DATA-AVISO)卫星高度计资料发现,ACC区涡动能(Eddy Kinetic Energy,EKE)的季节变化不明显,但年际变化非常显著。对纬向风应力与年际南半球环状模(Southern Annular Mode,SAM)异常事件的分析表明,纬向风应力极大/极小值超前EKE极大/极小值3年左右出现,EKE对风应力延时响应的时间及强度依赖于风应力异常的强度。此外,还采用海洋环流与气候评估协会(Estimating the Circulation and Climate of the Ocean,ECCO)温盐数据,计算了南极绕极流区斜压能量转化率的分布,并基于此来分析年际尺度上风场、背景海洋间的能量传递关系。研究认为:ACC区中尺度涡的年际变化是由于年际南半球环状模相关的风应力变化引起ACC流量变化以及ACC相关洋域的等密面倾斜程度发生改变,导致背景海洋向中尺度涡的斜压能量转换改变,造成中尺度涡的活动产生年际调整。

Several dataset are used to study the interannual variability of the mesoscale eddies in the ACC（Antarctic Circumpolar Current） region.Analysis of AVISO data（Archiving,Validation and Interpretation of Satellites Oceanographic data） reveals that seasonal variability of EKE（Eddy Kinetic Energy） is barely discernible in this area,but its interannual variability is significant.Analysis of zonal wind stress and the interannual abnormal event of SAM（Southern Annular Mode） shows that maximum/minimum of zonal wind stress occurs around 3 years ahead of EKE maximum/minimum,lag and strength of the EKE response depend on the strength of wind stress anomaly.In addition,we also use ECCO-JPL temperature and salinity data to calculate the distribution of baroclinic energy conversion rate in the ACC region.Based on this we analyze the energy transfer between wind field and the background ocean in interannual time scales.Based on the above analysis,we consider that the interannual variability of the ACC mesoscale eddies is contributed to the SAM-related wind stress,which causes the variation of ACC transport and tilt of isopycnal surface.And this causes the variation of baroclinic energy conversion rate from the background ocean to mesoscale eddy,leading to the interannual variability of mesoscale eddies.