Subtropical shelf front off eastern south america
Subtropical shelf front off eastern south america
复制标题
南美洲东部副热带陆架前缘
DOI：
10.1029/1999jc000300
复制
发表时间：
2000
影响因子：
--
通讯作者：
Carlos Martinez
中科院分区：
文献类型：
--
作者：
A. Piola;E. Campos;O. O. Möller;M. Charo;Carlos Martinez
南美洲东部大陆架的历史水文学数据用于检查南纬 20° 至 40°S 区域水团的温盐特性。大陆架水团起源于南大西洋西边界流的开放海域海水的稀释。根据温度-盐度关系，识别出两个不同的水团，即亚南极陆架水和亚热带陆架水。亚南极陆架水源自主要在东南太平洋的亚南极水，由于过量降水和大陆径流而被稀释，并进入南纬 55° 附近的大陆架。亚热带陆架水是经过巴西海岸大陆径流稀释的南大西洋中央水。此外，拉普拉塔河口（大约位于南纬 36°）以及帕托斯-米林泻湖（南纬 32°）的上层陆架水域发生了严重稀释。拉普拉塔河和帕托斯河的外流形成低盐度舌，覆盖了陆架水，导致盐度降至 <30。低盐舌向北延伸越过陆架，冬季比夏季向北延伸得更远。低盐度水的范围对垂直层结有很大影响，并限制冬季对流到盐跃层以上的层。亚南极陆架水和亚热带陆架水之间很少或没有混合的迹象。强烈的温度、盐度和营养物前沿将这些水团分开。锋面呈南北方向，平均位于南纬32°50 m等深线附近，并向南延伸至南纬36°附近的陆架折断处。南纬 32° 至 34° 之间，副热带陆架锋面沿 100 至 200 m 等深线延伸，将亚南极陆架水与南大西洋中央水分开。根据温度和盐度分布，在低盐度表层之下，副热带陆架前缘表现为巴西-马尔维纳斯交汇处在南美洲大陆架上的延伸。因此，副热带陆架前缘的位置可能与巴西-马尔维纳斯交汇处与大陆坡的分离点的迁移有关。
Historical hydrographic data from the continental shelf off eastern South America are used to examine the thermohaline properties of the water masses in the region between 20°S and 40°S. The continental shelf water masses are originated by dilution of open ocean waters of the western boundary currents of the South Atlantic Ocean. On the basis of temperature-salinity relation, two distinct water masses are identified, namely, the Subantarctic Shelf Water and the Subtropical Shelf Water. Subantarctic Shelf Water originates by dilution of Subantarctic Water, primarily in the southeast Pacific, due to excess precipitation and continental runoff and enters the continental shelf near 55°S. The Subtropical Shelf Water is modified South Atlantic Central Water diluted by continental runoff from the coast of Brazil. In addition, substantial dilution of the upper shelf waters takes place at the mouth of Rio de la Plata (approximately located at 36°S) and, in a lesser extent, at the Patos-Mirim Lagoon (at 32°S). The Rio de la Plata and the Patos outflows form a low-salinity tongue that caps the shelf water leading to a salinity decrease to values <30. The low-salinity tongue extends northward over the shelf penetrating farther north in winter than in summer. The extent of the low-salinity water has a strong impact on the vertical stratification and acts to limit winter convection to the layer above the halocline. There is little or no indication of mixing between Subantarctic Shelf Water and Subtropical Shelf Water. An intense temperature, salinity, and nutrient front separates these water masses. The front is oriented along the north-south direction, located on average near the 50 m isobath at 32°S and extends southward toward the shelf break near 36°S. Between 32° and 34°S the Subtropical Shelf Front follows the 100 to 200 m isobaths and separates Subantarctic Shelf Water from the oceanic South Atlantic Central Water. On the basis of the temperature and salinity distributions, beneath the low-salinity surface layer, the Subtropical Shelf Front appears as an extension of the Brazil-Malvinas Confluence over the continental shelf of South America. Thus the location of the Subtropical Shelf Front may be linked to the migrations of the separation point of the Brazil-Malvinas Confluence from the continental slope.