Internal hydraulic jumps and overturning generated by tidal flow over a tall steep ridge

被引:141
作者
Legg, Sonya [1 ]
Klymak, Jody [2 ]
机构
[1] Princeton Univ, Program Atmosphere & Ocean Sci, Princeton, NJ 08544 USA
[2] Univ Victoria, Sch Earth & Ocean Sci, Victoria, BC, Canada
基金
美国海洋和大气管理局;
关键词
D O I
10.1175/2008JPO3777.1
中图分类号
P7 [海洋学];
学科分类号
0707 ;
摘要
Recent observations from the Hawaiian Ridge indicate episodes of overturning and strong dissipation coupled with the tidal cycle near the top of the ridge. Simulations with realistic topography and stratification suggest that this overturning has its origins in transient internal hydraulic jumps that occur below the shelf break at maximum ebb tide, and then propagate up the slope as internal bores when the flow reverses. A series of numerical simulations explores the parameter space of topographic slope, barotropic velocity, stratification, and forcing frequency to identify the parameter regime in which these internal jumps are possible. Theoretical analysis predicts that the tidally driven jumps may occur when the vertical tidal excursion is large, which is shown to imply steep topographic slopes, such that dh/dxN/omega > 1. The vertical length scale of the jumps is predicted to depend on the flow speed such that the jump Froude number is of order unity. The numerical results agree with the theoretical predictions, with finite-amplitude internal hydraulic jumps and overturning forming during strong offslope tidal flow over steep slopes. These results suggest that internal hydraulic jumps may be an important mechanism for local tidally generated mixing at tall steep topography.
引用
收藏
页码:1949 / 1964
页数:16
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