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Unformatted text preview: The Circulation of the Oceans of
Dr. Emily Berndt Fundamentals of the Climate System EAS 253 I. Winds and Surface Currents I.
a. The atmospheric circulation is caused by a. atmospheric pressure gradients that result from vertical or horizontal temperature differences differences b. Temperature differences are caused by b. latitudinal differences in solar radiation latitudinal Surface Winds Winds Surface Ocean Currents Surface Surface Ocean Currents Surface I. Winds and Surface Currents I.
c. Do the oceans circulation for the same reason as the c. atmosphere? atmosphere? i. No- atmosphere is heated from below ii. Solar heating takes place at the surface for the ocean 1. Warm water near surface 2. Sun’s rays only warm top few hundred m (~ 100m) 3. stable situation, little vertical movement 4. density is impacted by the temperature and salt content 4. of the water of iii. The oceans overturn very slowly I. Winds and Surface Currents I.
d. Temperature changes in the ocean occur slowly i. High heat capacity iii. Slight changes in solar radiation has little impact on i. SSTs. iii. Does not circulate as a direct response to surface heating heating iv. Temperature plays an indirect role 1. Temperature influences atmosphere circulation 2. Wind patterns determine the circulation of the 2. upper ocean upper ocean I. Winds and Surface Currents I.
e. Surface Currents i. Winds stress over the ocean causes friction ii. Frictional drag sets up the wind drift currents iii. Currents confined to top 50-100 m iv. Well developed current 1-2 km deep v. Coriolis deflects currents 1. Right in NH, left in SH 2. deflections is 20-25° from wind direction vi. Currents complete large, circular patterns called gyres 1. Best defined in subtropical oceans 2. clockwise in NH, counterclockwise in SH I. Winds and Surface Currents I.
f. Convergence ii. Why doesn’t water pile up when it . reaches the coasts? reaches I. Winds and Surface Currents I.
iii. Water piles up or converges in the middle i. of a gyre due to: of
1. Wind driven surface currents 2. Earth’s rotation 3. Friction I. Winds and Surface Currents I.
iii. Ekman Spiral I. Winds and Surface Currents I.
iv. Ekman Transport Upwelling Upwelling What are the implications of Ekman What Transport if the prevailing wind is flowing south along a coastline? south Water is pushed away from the coast Water and replaced with cold water from the depths depths Coldest SST’s Correlate with Strongest Upwelling Strongest Coastal Upwelling Coastal Wind blowing parallel to a shore Wind or offshore can cause coastal upwelling upwelling The friction of wind blowing along The the ocean surface causes the water to begin moving, the coriolis effect deflects it to the right and Ekman transport moves it offshore it Upwelling impacts climate and Upwelling increases nutrients increases Downwelling occurs when wind Downwelling blows the opposite direction blows Little influence on climate or Little productivity productivity Transports dissolved gasses and Transports nutrients downward nutrients g. Divergence i. occurs near the equator
1. NE trades and SE trades create diverging north and south equatorial currents I. Winds and Surface Currents I. ii. Occurs along coastlines Depending on:
1.direction of wind movement 2. surface current iii. Important regions 1. SW coast of North America
2. west coast of South America 3. west coast of Africa 4. Easterly winds and south moving currnets I. Winds and Surface Currents I.
h. Upwelling and Downwelling I. Winds and Surface Currents I.
i. Geostrophic Flow (Current) ii. The real reason why the subtropical ocean circulation . forms gyres forms iii. Areas of CON and DIV produce slight variations in sea i. surface elevation surface 1. Sea surface slopes from one point to another 2. Changes in slope ~1 in 10^5m to 1 in 10^m 2. 3. slight elevation gradients cause a downslope force due to 3. gravity gravity 8.6 ...
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- Spring '11