Current Weather Introduction to Air-Sea interactions Ekman Transport Sub-tropical and sub-polar gyres Upwelling and downwelling Return Exam I For Next Class: Read Moran Ch. 8 (pp ) Climate and Air-Sea Interactions

© AMS2 Driving Question  How do interactions between the ocean and atmosphere impact worldwide climate and short-term climate variability?

© AMS3 Air/Sea Interactions  The ocean influences radiational heating and cooling of the planet Primary control of the amount of solar radiation absorbed at Earth’s surface Primary control of the amount of solar radiation absorbed at Earth’s surface Contributes to non-radiative latent heat and sensible heat fluxes at the air/sea interface Contributes to non-radiative latent heat and sensible heat fluxes at the air/sea interface

© AMS4 Air/Sea Interactions  Ocean and atmosphere are closely coupled Variations in atmospheric conditions can impact temperatures and wind-driven currents Variations in atmospheric conditions can impact temperatures and wind-driven currents Ocean surface currents strongly influence climate Ocean surface currents strongly influence climate Broad scale patterns of sea-surface temperature strongly influence the location of major features of the atmosphere’s planetary scale circulation Broad scale patterns of sea-surface temperature strongly influence the location of major features of the atmosphere’s planetary scale circulation

© AMS5 Mean State of Ocean Circulation  Ekman Transport Ekman spiral: simplified model of the three-dimensional current pattern caused by a steady horizontal surface wind Ekman spiral: simplified model of the three-dimensional current pattern caused by a steady horizontal surface wind Indicates that the direction of water movement changes with increasing depthIndicates that the direction of water movement changes with increasing depth Each successively lower layer moves more toward the right and at a slower speedEach successively lower layer moves more toward the right and at a slower speed

© AMS6 Mean State of Ocean Circulation  Ekman Transport Net transport of water due to the coupling between the surface wind and water is known as Ekman transport Net transport of water due to the coupling between the surface wind and water is known as Ekman transport Piles up surface waters in some areas of the ocean and removes surface waters from other areasPiles up surface waters in some areas of the ocean and removes surface waters from other areas Produces variations in the height of the sea surface, causing it to slope gradually Produces variations in the height of the sea surface, causing it to slope gradually

© AMS7 Mean State of Ocean Circulation  Geostrophic Flow and Ocean Gyres Horizontal movement of surface water arising from a balance between the pressure gradient force and the Coriolis Effect is known as geostrophic flow Horizontal movement of surface water arising from a balance between the pressure gradient force and the Coriolis Effect is known as geostrophic flow Characterizes gyres, large-scale roughly circular surface current systems in the ocean basinsCharacterizes gyres, large-scale roughly circular surface current systems in the ocean basins

© AMS8 Mean State of Ocean Circulation  Geostrophic Flow and Ocean Gyres Subtropical gyres are centered near 30° latitude in the North and South Atlantic, the North and South Pacific, and the Indian Ocean Subtropical gyres are centered near 30° latitude in the North and South Atlantic, the North and South Pacific, and the Indian Ocean Ekman transport causes waters to converge from all sides toward the central region of a subtropical gyre Ekman transport causes waters to converge from all sides toward the central region of a subtropical gyre

© AMS9 Mean State of Ocean Circulation  Upwelling and Downwelling Coastal upwelling occurs where Ekman transport moves surface waters away from the coast Coastal upwelling occurs where Ekman transport moves surface waters away from the coast Surface waters are replaced by water that wells up from belowSurface waters are replaced by water that wells up from below

© AMS10 Mean State of Ocean Circulation  Upwelling and Downwelling Where Ekman transport moves surface waters toward the coast, the water piles up and sinks in the process known as coastal downwelling Where Ekman transport moves surface waters toward the coast, the water piles up and sinks in the process known as coastal downwelling

© AMS11 Mean State of Ocean Circulation  Upwelling and Downwelling Upwelling is most common along the west coast of continents bordering the subtropical gyres Upwelling is most common along the west coast of continents bordering the subtropical gyres Upwelling and downwelling also occur in the open ocean where winds cause surface waters Upwelling and downwelling also occur in the open ocean where winds cause surface waters Diverge from a regionDiverge from a region causing upwelling causing upwelling Converge toward a regionConverge toward a region causing downwelling causing downwelling

© AMS12 Mean State of Ocean Circulation  Upwelling and Downwelling Equatorial upwelling occurs when surface waters are moved away from the equator and replaced by upwelling waters Equatorial upwelling occurs when surface waters are moved away from the equator and replaced by upwelling waters Upwelling and downwelling influence ocean temperatures, biological activity, weather, and climate Upwelling and downwelling influence ocean temperatures, biological activity, weather, and climate

© AMS13 Mean State of Ocean Circulation  Thermohaline Circulation Deep-ocean circulation driven by variations in density Deep-ocean circulation driven by variations in density Caused by variations in temperature and salinityCaused by variations in temperature and salinity Significant in the Earth system because Significant in the Earth system because Contributes to poleward heat transportContributes to poleward heat transport Modifies climateModifies climate