浙江沿岸黑潮次表层水表层露出机制分析

Analysis of surface exposure mechanism of Kuroshio subsurface water along the coast of Zhejiang Province

中文关键词:  浙江沿岸  黑潮次表层水  海面高度异常  地转流  底Ekman效应

英文关键词:Zhejiang Coast  Kuroshio Subsurface Water  Sea Level Anomaly  Geostrophic Current  Bottom Ekman Effect

中文摘要:

      大陈镇海洋站设立在离浙江岸线25 km的大陈岛上，该站于2013年8月观测到异于常年的22 ℃的低温和34.30的高盐记录，本文利用大面调查数据、风场数据、海面高度异常数据以及地转流数据对该海洋站异常低温高盐记录的来源和成因进行了讨论和研究。结果表明：2013年8月大陈镇海洋站观测记录的水团为黑潮次表层水。在持续的偏南风作用下，浙江沿岸表层Ekman流离岸输运量数倍至十几倍于其他年份，导致近岸海面高度异常降低，外海海面高度异常升高，相距约2个经度的外海到近岸月平均海面高度异常差达到38 cm，外海到近岸的压强梯度差远强于正常年份，导致沿岸向东北方向流动的地转流异常加强，诱发的底Ekman流总体向岸输送，为黑潮次表层水向岸入侵提供动力，黑潮次表层水越过传统上升流区，从2-3 m厚的底Ekman层入侵到近岸区域，进而涌升至表层。鉴于黑潮次表层水低温高盐以及富营养盐的水文性质，该水团出现在近岸表层可能对当地渔业生产和生态环境产生巨大影响。

英文摘要:

      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 ℃ 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.