Dachenzhen Ocean Station was set up on Dachen Island,25 km off the coast of Zhejiang Province.In August 2013,the station observed a low temperature of 22°C and a high salinity record of 34.3,which was different f...Dachenzhen Ocean Station was set up on Dachen Island,25 km off the coast of Zhejiang Province.In August 2013,the station observed a low temperature of 22°C and a high salinity record of 34.3,which was different from the usual year.In this paper,the sources and causes of the abnormal low temperature and high salinity record were discussed and studied by using the cruises data,wind data,Sea level anomaly data and absolute geostrophic current data.The results show that the water mass recorded at Dachenzhen Ocean Station in August 2013 is the subsurface water of Kuroshio.Under the continuous southerly wind,the offshore transport volume of surface Ekman current along the coast of Zhejiang is several times to ten times that of other years,resulting in an abnormal decrease in the offshore sea surface and an abnormal rise in the offshore sea surface.The abnormal difference of the monthly mean sea surface height from the offshore sea to the offshore coast is 38 cm,and the pressure gradient difference from the offshore sea to the offshore coast is much stronger than that in normal years.As a result,the geostrophic current that flows northward along the bottom coast is abnormally strengthened,and the induced bottom Ekman current is generally transported to the shore,providing the power for the Kuroshio subsurface water to invade the shore.The Kuroshio subsurface water penetrates the traditional upwelling area from the bottom Ekman layer 2-3m thick into the nearshore area,and then surges to the surface.In view of the hydrologic properties of low temperature,high salinity and nutrient-rich salt in the subsurface water of Kuroshio,the occurrence of this water mass in the near-shore surface water may have a great impact on the local fishery production and ecological environment.展开更多
文摘Dachenzhen Ocean Station was set up on Dachen Island,25 km off the coast of Zhejiang Province.In August 2013,the station observed a low temperature of 22°C and a high salinity record of 34.3,which was different from the usual year.In this paper,the sources and causes of the abnormal low temperature and high salinity record were discussed and studied by using the cruises data,wind data,Sea level anomaly data and absolute geostrophic current data.The results show that the water mass recorded at Dachenzhen Ocean Station in August 2013 is the subsurface water of Kuroshio.Under the continuous southerly wind,the offshore transport volume of surface Ekman current along the coast of Zhejiang is several times to ten times that of other years,resulting in an abnormal decrease in the offshore sea surface and an abnormal rise in the offshore sea surface.The abnormal difference of the monthly mean sea surface height from the offshore sea to the offshore coast is 38 cm,and the pressure gradient difference from the offshore sea to the offshore coast is much stronger than that in normal years.As a result,the geostrophic current that flows northward along the bottom coast is abnormally strengthened,and the induced bottom Ekman current is generally transported to the shore,providing the power for the Kuroshio subsurface water to invade the shore.The Kuroshio subsurface water penetrates the traditional upwelling area from the bottom Ekman layer 2-3m thick into the nearshore area,and then surges to the surface.In view of the hydrologic properties of low temperature,high salinity and nutrient-rich salt in the subsurface water of Kuroshio,the occurrence of this water mass in the near-shore surface water may have a great impact on the local fishery production and ecological environment.
