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GEOL 150 MIDTERM 2 Study Guide

GEOL 150 MIDTERM 2 Study Guide - MIDTERM#2 STUDY...

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MIDTERM #2 STUDY GUIDE (Lectures 14-26) L ECTURE 14: S URFACE O CEAN C IRCULATION (& C HAPTER 2) Forces driving surface ocean circulation: o prevailing winds: winds blowing make waves and wind-drift currents o Coriolis force: causes currents to deflect clockwise/right (northern hemisphere) or counter-clockwise/left (southern hemisphere) Coriolis due to Earth’s Rotation: Coriolis leads to Ekman Transport (transfer of motion with water depth) coriolis force causes water to veer to the right/left water is driven deeper and deeper spiraling downwards ***This is kind of like taking a stack of paper and drawing circles in the top with your finger… the top sheets spiral more than the ones below so you get a spiral o Continental margins deflect and guide currents Most prominent result is huge gyres of water at subtropical latitudes o Spinning gyres result from drag of winds on ocean surface and coriolis deflection of the moving water (Coriolis effect turns the surface flow of water to the clockwise in Northern hemisphere and to counterclockwise in the southern hemisphere) o North Atlantic: trade winds blowing towards southwest and mid latitude westerlies blowing towards northeast push water into the center of the subtropical gyres and pile up a “lens” of warm water o The edges of continents act as boundaries that contain the flow of the gyres o The 5 gyres: Clockwise (northern hemisphere): North Atlantic Gyre, North Pacific Gyre Counterclockwise (southern Hemisphere): South Atlantic Gyre, Indian Ocean Gyre, South Pacific Gyre o Center of gyres= no surface life because there is no food or nutrients because there is no circulation, gyres circulate food from one place to another o Western boundary currents always move towards the poles → they transport relatively warmer waters, they are typically deep, narrow, flat, and some of the fastest currents eg. gulf stream – North Atlantic current o Eastern boundary currents move towards the equator→ move colder water. They are usually shallow, wide, and slow eg. California Current: cold water coming in from Alaska o Prevailing flow of water toward the equator in the deeper parts of the gyre must be balanced by a return flow towards the poles Eg. Poleward transport is the Gulf Stream (narrow concentrated outflow of warm salty water) and continues into North Atlantic Drift Generalized topography of ocean gyres: o Water is topographically higher in the middle of the gyres o Every time current moves, coriolis effect wants to push water to the right/left
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o coriolis causes the water to get pushed into the center and bulge in the middle o water in the center doesn’t want to stay piled up in the middle (gravity) so it pushes downward back out to the sides→ this causes down-welling Surface ocean currents and upwelling: o Boundary currents and offshore coastal winds create local coastal upwelling o Large-scale upwelling is associated with Equatorial Currents o
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