Northern winter djf 7 bathtub ocean with wind wind

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Northern Winter (DJF)
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7 Bathtub Ocean with Wind Wind Sea Surface Height What new force is introduced by differences in water height?
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8 Bathtub Ocean with Wind Wind High Pressure Low Pressure Pressure Gradient Force Geostrophic Current The geostrophic current is an oceanic flow in which the pressure gradient force is balanced by the Coriolis effect. The direction of geostrophic flow is parallel to the isobars (lines of equal pressure), with the high pressure to the right of the flow in the Northern Hemisphere, and the high pressure to the left in the Southern Hemisphere. Or in other words: The geostrophic current flows 90º to the right of the pressure gradient on the NH and 90º to the left of the pressure gradient on the SH. Northern Hemisphere example Geostrophic Current Overview of Today’s Lecture: Wind-driven Ocean Circulation Coriolis effect and atmospheric circulation Ekman transport Geostrophic Current Wind-driven Gyres
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9 Divergence + Upwelling Divergences in areas of upwelling in the opean ocean and the resulting changes in the height of the sea surface. These changes in sea surface height induce a pressure gradient force directed from high pressure toward low pressure. The balance of this pressure gradient force with the Coriolis force leads to circular motion around the low pressure system. DIVERGENCE Ocean surface Pycnocline Upwelling limit of wind influence Ekman transport Pressure gradient Geostrophic current into page Geostrophic current out of page H H L Northern Hemisphere CONVERGENCE Ocean surface Pycnocline Downwelling limit of wind influence Ekman transport Pressure gradient Geostrophic current into page Geostrophic current out of page Convergence + Downwelling Convergences in areas of downwelling in the opean ocean and the resulting changes in the height of the sea surface. These changes in sea surface height induce a pressure gradient force directed from high pressure toward low pressure. The balance of this pressure gradient force with the Coriolis force leads to circular motion around high pressure system Northern Hemisphere L L H Sea Surface Height Equatorial Divergence = lower sealevel Subtropical Convergence = higher sealevel Subtropical Convergence = higher sealevel H H L Equator Continent 45 ° N 45 ° S Continent Westerlies Trade winds Mounded sea surface Mounded sea surface Ekman transport Winds Gyre Currents Subtropical gyres in theory NH: clockwise SH: anticlockwise H H L (remember: NH high pressure to the right, SH high pressure to the left of the geostrophic flow) L L L L L L
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10 Equator Continent 45 ° N 45 ° S Continent Low High Low High Coriolis force Pressure gradient force Subtropical gyres in theory NH: clockwise SH: anticlockwise High High
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