Stability of a buoyancy-driven coastal current at the shelf break
Stability of a buoyancy-driven coastal current at the shelf break
复制标题
陆架断裂处浮力驱动的沿岸流的稳定性
DOI：
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发表时间：
2002
影响因子：
3.7
通讯作者：
P. Linden
中科院分区：
文献类型：
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作者：
C. Cenedese;P. Linden
在实验室中，通过从旋转容器中垂直边界附近的源释放浮力流体，产生浮力驱动的表面流。容器中引入了模拟大陆坡和大陆脊的不同底部地形。与底部情况相比，地形改变了流动，在底部情况下，电流在宽度和深度上增长，直到由于非轴对称扰动而变得不稳定。然而，当引入地形时，观察到浮力驱动电流的第二个不稳定性。描述流动的最重要参数是不稳定开始时大陆架宽度 W 与洋流宽度 L* 的比率。第一不稳定的 L* 值和第二不稳定的 L*−W 值不受地形影响，均为罗斯贝半径的 2-6 倍。因此，描述流动的参数可以表示为大陆架宽度与罗斯贝半径之比。当该比率大于 2-6 时，在当前锋线上观察到第二次不稳定。与大陆脊地形相比，大陆脊允许扰动增长到更大的幅度，形成涡流和锋面，而平缓的大陆坡降低了最不稳定模式的增长速率和幅度。当存在时，涡流不会与主流分离，并保持在陆架断裂附近。另一方面，对于罗斯贝半径的最大值，第一次不稳定被抑制，并且观察到流动保持稳定。在第一不稳定性的波长中发现了一个小但显着的变化，对于地形上的电流来说，其波长比平底上的电流要小。
Buoyancy-driven surface currents were generated in the laboratory by releasing buoyant fluid from a source adjacent to a vertical boundary in a rotating container. Different bottom topographies that simulate both a continental slope and a continental ridge were introduced in the container. The topography modified the flow in comparison with the at bottom case where the current grew in width and depth until it became unstable once to non-axisymmetric disturbances. However, when topography was introduced a second instability of the buoyancy-driven current was observed. The most important parameter describing the flow is the ratio of continental shelf width W to the width L* of the current at the onset of the instability. The values of L* for the first instability, and L*−W for the second instability were not influenced by the topography and were 2–6 times the Rossby radius. Thus, the parameter describing the flow can be expressed as the ratio of the width of the continental shelf to the Rossby radius. When this ratio is larger than 2–6 the second instability was observed on the current front. A continental ridge allowed the disturbance to grow to larger amplitude with formation of eddies and fronts, while a gentle continental slope reduced the growth rate and amplitude of the most unstable mode, when compared to the continental ridge topography. When present, eddies did not separate from the main current, and remained near the shelf break. On the other hand, for the largest values of the Rossby radius the first instability was suppressed and the flow was observed to remain stable. A small but significant variation was found in the wavelength of the first instability, which was smaller for a current over topography than over a flat bottom.