两个西边界流延伸体区域中尺度涡统计特征分析

Statistical characteristics of mesoscale eddies in the two western boundary current extension regions

黑潮和湾流是世界大洋中最典型的两支西边界流,黑潮延伸体(Kuroshio Extention,KE)和湾流延伸体(Gulf Stream Extention,GSE)区域中尺度涡活动十分活跃。本文综合利用卫星高度计资料和Argo浮标资料,对KE和GSE区域中尺度涡的表层特征及其对温盐影响进行了统计研究和对比分析。结果表明:黑潮和湾流主轴附近为涡旋频率的高值区,主轴南北两侧分别以气旋涡和反气旋涡数量占多,主轴附近的涡旋强度明显大于其他区域;两个区域的涡旋以西向移动为主,气旋涡和反气旋涡都具有向南(赤道)偏离的趋势;两个区域的涡旋数量都以夏、秋季较多,涡旋强度都在春、夏季较大,且GSE区域涡旋强度明显大于KE区域;气旋涡(反气旋涡)引起内部明显的温度负(正)异常,KE区域气旋涡(反气旋涡)内部呈"负—正"("正—负")上下层相反的盐度异常分布,GSE区域气旋涡(反气旋涡)在各层呈现较为一致的盐度负(正)异常;两个区域中尺度涡对温盐场的平均影响深度可达1 000×10~4 Pa以上。

Kuroshio and Gulf Stream are the two most typical western boundary currents in the world＇s ocean,and mesoscale eddies are very active in Kuroshio Extention（KE）and Gulf Stream extension（GSE）regions.In this paper,surface features of mesoscale eddies in KE and GSE regions and their effects on temperature and salinity fields are studied and compared using satellite altimeter data and Argo buoy data.The results show that eddy frequency is extremely high and eddy intensity is obviously larger near the main axes of both Kuroshio and Gulf stream,and cyclonic eddies（CE）and anticyclonic eddies（AE）dominate in the south and north sides of the main axes,respectively.Most eddies propagate westward with a little southward（equatorward）deflection.The amount of eddies in the two regions are both larger in summer and autumn,and eddy intensities are larger in spring and summer,meanwhile intensities of eddies in GSE are larger than those in KE.CE（AE）cause consistent negative（positive）temperature anomaly.CE（AE）in KE represent＂negative-positive＂（＂positive-negative＂）salinity anomaly distribution from upper to lower layers,while CE（AE）in GSE exhibit a more consistent negative（positive）salinity anomaly in each layer.The average effect of mesoscale eddies on temperature and salinity fields in the two regions can reach more than 1 000×10~4 Pa depths.