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PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Slide 46Slide 47Slide 48Slide 49Slide 50Slide 51Slide 52IV. Circulation of the Liquid Earth: The Oceans and the Hydrologic Cycle.A. Origin of the Oceans: 1. Where did the water come from?Outgassing from the Earth’s interior (volcanos), the same as the atmosphere. There have been oceans as far back as we can find rocks, almost 4 billion years. And there is still another ocean inside the Earth.V. Circulation of the Liquid EarthA. Origin of the Oceans1. Where did the water come from?2. Where did all the salt come from?Early geologists thought they could calculate the age of the Earth from the salt in the ocean.Ocean holds 5 x 1019 kg of salt.Rivers deliver 4 x 1012 kg of salt/year.Age of Earth is 13 x 106 years old.But, Earth is 4.6 x 109 years old…… what went wrong??V. Circulation of the Liquid EarthA. Origin of the Oceans1. Where did the water come from?2. Where did all the salt come from?Two key assumptions:• Rivers are the only source of salt.• All salt that enters the ocean stays there.Both are violated:• Salt is removed from the ocean.• New salt is also added to the ocean from mid-ocean spreading centers.V. Circulation of the Liquid EarthA. Origin of the OceansOur early geologists did not yet know about• Plate tectonics• Mid-ocean spreading centers• Evaporite basins• Sea critters that precipitate sea salts in their shells.• Sea-spray to the land.V. Circulation of the Liquid EarthA. Origin of the Oceans1. Where did the water come from?2. Where did all the salt come from?Calculating the age of the Earth this way adds three terms to our view of the Earth as a system:Reservoir, Flux and Residence TimeV. Circulation of the Liquid EarthA. Origin of the OceansReservoir: Reservoir: (a noun; it’s a “thing”) A volume or mass of something. Ocean (water, salt, etc.)Atmosphere (Oxygen, water vapor, etc.)Flux: (a verb; it’s the “action”) The rate at which energy or matter is transferred between reservoirs. The rate at which energy or matter is transferred between reservoirs. Expressed in amount per unit time.V. Circulation of the Liquid EarthA. Origin of the OceansReservoir: Flux: Residence time: The average time a substance stays in a reservoir. (Reservoir/Flux).In our salty ocean example, the calculated “age of the Earth”, 13 million years, is the residence time of salt in the ocean.V. Circulation of the Liquid EarthA. Origin of the OceansB. Distribution of water on EarthReservoirsReservoir Mass (1015 kg)Residence TimeOcean 1,400,000Snow and Ice 43,400Groundwater 15,300Freshwater 360Atmosphere 16Biosphere 2V. Circulation of the Liquid EarthA. Origin of the OceansB. Distribution of water on EarthReservoirs Fluxes (1015 kg/year)Evaporation from the ocean: 434Evapo-transpiration: 71(biota and lakes)Precipitation: 505Reservoir Mass (1015 kg)Residence TimeOcean 1,400,000Snow and Ice 43,400Groundwater 15,300Freshwater 360Atmosphere 16Biosphere 2MRTocean = Mass of the ocean flux of water from atm to oceanReservoir Mass (1015 kg)Residence TimeOcean 1,400,000 3000 yearsSnow and Ice 43,400Groundwater 15,300Freshwater 360Atmosphere 16Biosphere 2MRTocean = 1,400,000 = 3000 years 505Reservoir Mass (1015 kg)Residence TimeOcean 1,400,000 3000 yearsSnow and Ice 43,400Groundwater 15,300Freshwater 360Atmosphere 16 12 days Biosphere 2MRTatmosphere = 16 = 12 days 505V. Circulation of the Liquid EarthA. Origin of the OceansB. Distribution of water on EarthC. Surface currentsTroposphere unstable, ocean stableUnlike the troposphere, which is heated from the bottom, hence is fundamentally unstable and circulates in response to this instability, the oceans are heated from the top, hence the warmest (least dense) water is mostly at the surface. Stable.V. Circulation of the Liquid EarthA. Origin of the OceansB. Distribution of water on EarthC. Surface currents 1. Surface currents are driven by winds through the frictional coupling between atmosphere and sea surface.Surface currents generally restricted to uppermost 100 m.Average depth of the deep ocean = 4000 mV. Circulation of the Liquid EarthA. Origin of the OceansB. Distribution of water on EarthC. Surface currents 1. Surface currents - winds2. Coriolis: surface currents deflected to right (NH) or left (SH) of the prevailing winds.Simplified Surface CurrentsV. Circulation of the Liquid EarthA. Origin of the OceansB. Distribution of water on EarthC. Surface currents 1. Surface currents - winds2. Coriolis: surface currents deflected to right (NH) or left (SH) of the prevailing winds. We expect simple gyres. But simple gyres are complicated by continents.Generalized ocean surface currentsV. Circulation of the Liquid EarthA. Origin of the OceansB. Distribution of water on EarthC. Surface currents 1. Surface currents - winds2. Coriolis -- Actual net motion of water is further complicated by Ekman SpiralV. Circulation of the Liquid EarthA. Origin of the OceansB. Distribution of water on EarthC. Surface currents 1. Surface currents - winds2. Coriolis -- Ekman Spiral: transfer of Coriolis Effect down through the water column. Net effect is that surface water moves at right angles to the wind. Ekman TransportV. Circulation of the Liquid EarthC. Surface currents 1. Surface currents - winds2. Coriolis -- Ekman Spiral3. Convergence: surface water tends to pile up at the center of gyres, where downwelling occurs.4. Divergence: Winds on both sides of the equator are easterly, so net motion of water is N in NH and S in SH, creating divergence, and upwelling.V. Circulation of the Liquid EarthC. Surface currents 1. Surface currents - winds2. Coriolis -- Ekman Spiral3. Convergence: downwelling4. Divergence: upwelling5. Coastal Upwelling: Winds moving parallel to the continental coast can result in strong upwelling.Southern HemisphereStrong NW windsEkman Transport to the SW.UpwellingV. Circulation of the Liquid EarthC. Surface currents 1. Surface currents - winds2. Coriolis -- Ekman Spiral3. Convergence: downwelling4. Divergence: upwelling5.


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CU-Boulder GEOL 1060 - Circulation of the Liquid Earth

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