The Columbia River plume study : Subtidal variability in the velocity and salinity fields
The Columbia River plume study : Subtidal variability in the velocity and salinity fields
复制标题
DOI：
10.1029/97jc03290
复制
发表时间：
1998-05
影响因子：
--
通讯作者：
B. Hickey;L. Pietrafesa;D. Jay;W. Boicourt
中科院分区：
文献类型：
--
作者：
B. Hickey;L. Pietrafesa;D. Jay;W. Boicourt
对来自美国西海岸哥伦比亚河的强风驱动的中纬度浮力羽流的综合研究表明，羽流在秋冬季节有两种基本结构，即在南风或轻微北风应力期间向西向西北倾斜的薄（∼5-15 m）强分层羽流和在南风或轻微北风应力期间向北倾斜并紧贴海岸的较厚（∼10-40 m）弱分层羽流。较强的北向压力时期。羽流及其速度场几乎瞬时响应风速或风向的变化，风波动的时间尺度为 2-10 天。风驱动的摩擦流导致沿着羽流轴的主要单向流动分别转向轴的右侧或左侧，以产生北风或南风。在下游更远的地方，洋流变成平行而不是交叉盐度等值线，这与地转平衡一致。特别是，在羽流与海岸分离的时期，水流往往会在较新鲜的水堆周围流动。在距离河口超过约 20 公里的地方，从内陆到中陆的沿陆架深度平均流量是线性的，并且深度平均加速度仅由表面和底部应力之间的差异控制至最低阶。在该区域，~5 m处的沿陆架地转浮力驱动流（根据表面密度计算）和沿陆架地转风驱动流（根据深度平均线性模型计算）在震级上相当（~10-25 cm s−1）。
A comprehensive study of the strongly wind driven midlatitude buoyant plume from the Columbia River, located on the U.S. west coast, demonstrates that the plume has two basic structures during the fall/winter season, namely, a thin (∼5–15 m), strongly stratified plume tending west to northwestward during periods of southward or light northward wind stress and a thicker (∼10–40 m), weakly stratified plume tending northward and hugging the coast during periods of stronger northward stress. The plume and its velocity field respond nearly instantaneously to changes in wind speed or direction, and the wind fluctuations have timescales of 2–10 days. Frictional wind-driven currents cause the primarily unidirectional flow down the plume axis to veer to the right or left of the axis for northward or southward winds, respectively. Farther downstream, currents turn to parallel rather than cross salinity contours, consistent with a geostrophic balance. In particular, during periods when the plume is separated from the coast, currents tend to flow around the mound of fresher water. At distances exceeding about 20 km from the river mouth, the along-shelf depth-averaged flow over the inner to midshelf is linear, and depth-averaged acceleration is governed to lowest order by the difference between surface and bottom stress alone. In this region, along-shelf geostrophic buoyancy-driven currents at ∼5 m (calculated from surface density) and along-shelf geostrophic wind-driven currents (computed from a depth-averaged linear model) are comparable in magnitude (∼10–25 cm s−1).