13_geostrophic_flow

13_geostrophic_flow - Geostrophic flow GS222 Lecture 13...

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Unformatted text preview: Geostrophic flow GS222 Lecture 13 Overview - this lecture Ekman transport, divergence, and convergence Water flow under pressure, balanced by Coriolis effect Geostrophic currents and gyres Western boundary current intensification Ekman transport and pycnocline Ekman transport limited to upper ~ 100 m below ~ 100 m density increases rapidly, frictional coupling reduced pycnocline occurs at base of layer mixed by winds, i.e. mixed layer Ekman transport and pressure 1) Ekman transport: piles up water in some places and moves water away from others 2) Variations in sea surface height create horizontal pressure gradients that drive currents 2 primary causes: z z z p = g (z+ z) p = g z pressure = g z density (kg m-3 ) accel. due to gravity (m s-2 ) depth (m) z z z p = g (z+ z) p = g z Horizontal pressure gradients drive water from high to low pressure zones Pressure gradient works in opposite direction of Ekman transport horizontal pressure gradient = g z H L Ekman transport Ekman transport and pressure Pressure-driven flow Ekman flow limited to upper ~100 m, whereas pressure gradient driven flow occurs in any place where pressure gradient is felt Winds can indirectly influence currents to ~1000 m Mean flow below the wind-driven layer is directed away from highest sea surface elevation Example of winds, sea surface height, and induced pressure field H Geostrophic flow Water will flow away from the peak of pile, away from the...
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This note was uploaded on 01/20/2012 for the course GEO 222 taught by Professor Davidlund during the Winter '11 term at University of Michigan.

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13_geostrophic_flow - Geostrophic flow GS222 Lecture 13...

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