Because OF ALL THE ICE How do you know there s an Ice Age Global Circulation Patterns 3 Atmosphere Ocean coupling Low latitudes Oceans High latitudes Atmosphere OCNG 251 Oceanography Tuesday Oct 21st 2008 i The Ocean Atmosphere coupling ii Surface Ocean Circulation Atmosphere Ocean coupling Atmosphere Transfer of moisture to the atmosphere heat released in higher latitudes as water condenses Atmosphere Ocean coupling Atmosphere Transfer of moisture to the atmosphere Hurricanes In summary Latitudinal Differences in Energy www weather com Amount of solar radiation received annually at the Earth s surface Latitudinal Differences in Salinity Latitudinal Differences in Density Structure of the Oceans Heavy Light T has a much greater impact than S on Density Atmospheric Wind patterns January Atmospheric Wind patterns January Westerlies Easterlies Easterlies Westerlies High Low Pressure systems Heat capacity High Low Pressure systems Wind generation Wind drag Zonal Wind Flow Wind is moving air Air molecules drag water molecules across sea surface remember waves generation frictional drag Westerlies If winds are prolonged the frictional drag generates a current Easterlies Only a small fraction of the wind energy is transferred to the water surface Easterlies Westerlies Any wind blowing in a regular pattern High Low Pressure systems Wind generation by flow from High to Low pressure systems Coriolis effect 1 Ekman Spiral Once the surface film of water molecules is set in motion they exert a frictional drag on the water molecules immediately beneath them getting these to move as well Motion is transferred downward into the water column Speed diminishes with depth friction Direction changes with depth coriolis 1 Ekman Spiral Spiraling current in which speed and direction change with depth Net transport average of all transport is 90 to right North Hemisphere or left Southern Hemisphere of the generating wind Transport occurs at most down to 100m 1 Ekman Transport An example July 1 Ekman Transport An example January 1 Ekman Transport Surface circulation Large central gyres in ocean basins 2 Geostrophic Flow Dynamic equilibrium between Coriolis deflection and pressure gradient 2 2 Geostrophic Flow Ekman transport is limited to 100m How come the Gulf Stream extends down to 500 800m Pressure or geostrophic gradients P gh 1 2 Geostrophic Flow Western intensification due to transport and vorticity 3 Ekman Transport 1 Downwelling Convergence zones generate downwelling of water and nutrients The Gulf Stream Western intensification Grand scheme of things Surface circulation Heat transport Ekman Transport 2 Upwelling If wind blows parallel to a shore in the proper direction Ekman transport moves near surface water offshore Water must then rise from below to compensate for seaward surface flow 1 Ekman Transport Upwelling Peru California Africa Australia Grand scheme of things Surface circulation Warm and cold currents Balance of Earth Heat budget Next time The Ocean in Motion 2 Vertical circulation 3 Ocean Structure