Bulge formation of a buoyant river outflow
Bulge formation of a buoyant river outflow
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DOI：
10.1029/2007jc004100
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发表时间：
2008-01-24
影响因子：
3.6
通讯作者：
Schofield, Oscar
中科院分区：
文献类型：
--
作者：
Chant, Robert J.;Glenn, Scott M.;Schofield, Oscar
[1]2005年拉格朗日输运和转化实验(LATE)期间的观测表明，哈德逊河的外流形成了一个再循环流体的凸起，限制了沿岸洋流中平流离开的淡水的体积。聚焦于一次始于下流风的事件，我们估计了沿海洋流中的淡水通量和凸起的淡水库存。在热风平衡条件下，沿岸流以地面平流烟羽为特征。然而，沿岸流中的淡水输运不到淡水总输出量的1/2。凸起从海岸延伸了30公里，沿海岸方向延伸了40公里，在海洋彩色图像中很明显。在逐日平均的地面流雷达资料中，隆起区的再环流也很明显，但这种流动模式在逐时资料中被潮汐和风的强迫所掩盖，即使在日间频段也是如此。然而，哈德逊河外流的许多方面与最近的实验室实验和浮力排放的数值模拟是一致的。不断增长的凸起将河流的流出输送到哈德逊陆架山谷的顶部，在那里它越过了50米的等深线。该地区以前的工作表明，锋面特征位于这条等深线上。我们观察到淡水沿着这条等深线输送，这表明淡水有一条快速的跨陆架输送通道。隆起的形成和跨陆架的运输都具有重要的生物地球化学意义。
[1] Observations taken during the Lagrangian Transport and Transformation Experiment (LaTTE) in 2005 indicated that the Hudson's river outflow formed a bulge of recirculating fluid that limits the volume of fresh water that is advected away in a coastal current. Focusing on an event that began with downwelling winds we made estimates of the freshwater flux in the coastal current and the fresh water inventory of the bulge. The coastal current was characterized by a surface advected plume in thermal wind balance. However, the freshwater transport in the coastal current was less than 1/2 of the total freshwater outflow. The bulge extended 30 km from the coast and 40 km in the along-shore direction and was evident in ocean color imagery. Recirculation in the bulge region was also apparent in daily averaged surface current radar data, but this flow pattern was obscured in the hourly data by tidal and wind-forcing even in the diurnal band. Nevertheless, many aspects of the Hudson's outflow are consistent with recent laboratory experiments and numerical simulations of buoyant discharges. The growing bulge transports the river's outflow to the head of the Hudson shelf valley where it crosses the 50 m isobath. Previous work in this region indicates that frontal features reside along this isobath. We observed fresh water being transported along this isobath and is suggestive of a rapid cross-shelf transport pathway for fresh water. Both the bulge formation and cross-shelf transport have significant biogeochemical implications.