The freshwater transport and dynamics of the western Maine coastal current
The freshwater transport and dynamics of the western Maine coastal current
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DOI：
10.1016/j.csr.2004.04.001
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发表时间：
2004-08-01
影响因子：
2.3
通讯作者：
Keafer, BA
中科院分区：
文献类型：
--
作者：
Geyer, WR;Signell, RP;Keafer, BA
利用在美国缅因湾进行的观测，描述了缅因州西部沿岸流的淡水输送、时间变异性和动态。这些观测包括1993年4月至7月和1994年4月至7月期间的系泊测量、多次水文测量和漂流释放。由于进入海湾西部的河流的淡水输入，沿岸水流的盐度和沿岸流速有很强的季节性信号。春季淡水沿岸流的表层盐度一般比环境低2PSU，表层沿岸流以0.10-0.20m S(-1)的速度向西南方向流动，偶尔达到0.50m S(-1)。在50-100米深的水中，羽流厚度通常为10-20米，因此在其大部分面积范围内，它与底部隔离得很好。由于风应力的变化，羽流中沿海岸的淡水输送变化很大，但在几周到几个月的时间尺度上，它遵循河流输入的变化，时间滞后与平流速度一致。不到一半的沿岸流输送是由斜压梯度所解释的；与缅因湾大尺度动力有关的正压强迫约占输送的60%。沿岸流中的淡水输入量比当地河流的淡水输入量高出30%，这表明圣约翰河向东北方向500公里的淡水输入量做出了重大贡献。然而，缅因州西部沿海洋流的测量表明，沿海岸的淡水斜压输送显著减少，e折叠尺度约为200公里。(C)2004爱思唯尔有限公司。保留所有权利。
Observations in the Gulf of Maine, USA, were used to characterize the freshwater transport, temporal variability and dynamics of the western Maine coastal current. These observations included moored measurements, multiple hydrographic surveys, and drifter releases during April-July of 1993 and 1994. There is a strong seasonal signal in salinity and along-shore velocity of the coastal current, caused by the freshwater inputs of the rivers entering the western Gulf. Surface salinity within the coastal current during the spring freshet is typically 2 psu below ambient, and along-shore currents in the surface layer are directed southwestward at speeds of 0.10-0.20 m s(-1) occasionally reaching 0.50 m s(-1). The plume thickness is typically 10-20 m in water depths of 50-100 m, thus it is well isolated from the bottom over most of its areal extent. The along-coast freshwater transport within the plume varies considerably due to variations in wind stress, but on time scales of weeks to months it follows the variations of riverine input, with a time lag consistent with the advective velocity. Less than half of the transport of the coastal current is explained by the baroclinic gradient; the barotropic forcing associated with the larger-scale dynamics of the Gulf of Maine accounts for about 60% of the transport. The volume of freshwater transport in the coastal current exceeds the local riverine input of fresh water by 30%, suggesting a significant contribution of freshwater transport from the St. John River, 500 km northeastward. The measurements within the western Maine coastal current, however, indicate a significant decrease in the baroclinic transport of fresh water along the coast, with an e-folding scale of approximately 200 km. (C) 2004 Elsevier Ltd. All rights reserved.