台湾东北海域夏季冷穹及上升流的数值模拟

夏季,黑潮在台湾东北向东海陆架的入侵表现为黑潮次表层水的强烈涌升,并在陆架上形成明显的冷穹。本研究利用ROMS(Regional Ocean Modeling System)模式,模拟了夏季黑潮入侵所形成的冷穹及上升流的三维结构,并讨论了上升流形成的动力机制。结果表明,冷穹中心在50 m以上的深度位于25.5°N,122.5°E附近,最大降温5 ℃以上;在50 m以下的深度,冷穹的中心位于台湾岛北缘。表层黑潮在台湾北缘不存在明显入侵,在陆坡东向转向附近则以气旋式环流入侵至陆架以上。此外,上升流主要位于陆坡坡度最大的区域,且黑潮次表层水的涌升存在两个较为明显的路径,分别位于台湾岛以北的100 m与200 m等深线之间以及东向转向的陆坡区域。在上层,平流作用是上升流产生的主要机制;而在近底层,平流作用与底摩擦都对上升流有贡献。

Simulation of the cold dome and upwelling northeast of Taiwan in summer

The Kuroshio on-shelf intrusion northeast of Taiwan manifests as the subsurface Kuroshio water upwelling and a "cold dome" structure in summer. Using ROMS (Regional Ocean Modeling System) model, the three-dimensional structure of the cold dome and the circulation along with upwelling induced by Kuroshio intrusion were analyzed, and the mechanisms of the formation of upwelling were also discussed. Model results show that the center of the cold dome is located near 25.5°N, 122.5°E in the layers upper of 50 m with maximum 5 ℃ cooling, and close to the north end of Taiwan Island in the layers lower of 50 m. The result of current structures show that Kuroshio surface intrusion is not obvious at the north end of Taiwan Island. A cyclonic circulation exists near the region where the shelf break turns eastward. Upwelling mainly occurs near the large slope of shelf break, with two obvious routes of the subsurface water upwelled onto the shelf. One of the routes is north of the Taiwan Island and between the isobaths of 100 m and 200 m, while the other one is near the region where the shelf break turns eastward. In the upper layer, the advection term is the main dynamical factor of the upwelling. While in the near-bottom layer, both the advection and bottom friction terms contribute to the upwelling.