A New Finding of Large-Scale Ocean Eddy in the Antarctic

通过对日本邮轮水文资料和漂流浮标资料的分析，阐明了印度洋地区南极辐散的海洋结构。南极辐散是由一条纬向长约500公里、经向长约200公里的气旋性涡流组成的。部分向东流动的南极绕极流蜿蜒在涡流之间的边界区域。控制气旋性涡旋形成和维持的主要因素是两种不同类型的水平流进入涡旋区的浅层和深层。温暖、咸化的环极地深水以上升流的形式进入浅层，而寒冷而密集的沿海水则以沿相对较浅的脊坡下沉的方式进入深层。涡旋形成年复一年地重复出现，但其位置略有变化；从大陆架地区向北延伸的脊线的存在大致控制了选定位置的涡旋形成。从地旋流型和盐度分布发现，沿海和近海之间的水交换是通过涡旋和CDW弯曲的环流进行的，这也导致了经向热量和盐分的交换。

An oceanic structure of the Antarctic Divergence in the Indian Ocean sector was clarifiedon the basis of analysis of hydrographic data and drifting buoy data for Japanese cruises.The Antarctic Divergence is composed of a street of several cyclonic eddies with the orders of about 500 km in zonal length and about 200 km in meridional length. Part of the eastward flowing antarctic circumpolar Current meanders in the boundary regions between the eddies. The major factor which governs the formation and maintenance of the cyclonic eddies is the advection of two different kinds of waters into shallow and deep layrs of the eddy regions. The warm, saline circumpolar Deep Water advects into the shallow layr as upwelling whereas a cold and dense, coastal water advects into the deep layr as sinking along a relatively shallow ridge slope. The eddy formation recurs year after year though their locations slightly change ; the existence of ridges extending northward from the continental shelf region approximately governs the eddy formation in the selective locations. We found from geostrophical flow patterns and salinity distributions that a water exchange between coastal and offshore regions occurs through the circulation with both the eddies and the CDW meanders ; this also causes the meridional exchanges of heat and salt.