Lecture 5 Notes
Lecture 5 Notes Geo 002
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This 3 page Class Notes was uploaded by Linda Tan on Tuesday February 16, 2016. The Class Notes belongs to Geo 002 at University of California Riverside taught by Prof. Tim Lyons in Winter 2016. Since its upload, it has received 23 views. For similar materials see Earth's Climate Through Time in Geology at University of California Riverside.
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Date Created: 02/16/16
GEO 2: Lecture 5 Notes Ocean Circulation Heating imbalance causes wind and ocean movement because of they move excess heat from high to low latitudes. Half is moved by the atmosphere and the other half is moved by the ocean. Hydrologic Cycle = steady state example Ocean: precipitation and rivers (return rate) = evaporation (loss) Global water distributions: Largest reservoirs are the ocean (96.5%) > glaciers (1.74%) > groundwater (1.7%) > ground ice (0.022%) > lakes (0.013%) > atmosphere (0.001%) > rivers (0.0002%) > biosphere (0.0001%) If all frozen ice melted, the ocean level would rise 70 meters. Water in atmosphere: Warm air can hold more water vapor than cold air. Air cools as it rises above the Earth’s surface (ITCZ) Circulation of the Oceans: Surface circulation driven by wind and deep ocean circulation driven by temp and salinity. Sea Surface currents: Ekman Spiral (result of Coriolis Effect) Wind blowing on surface puts the water into motion and is deflected to the right (north). The surface interacts with the water beneath it and the spiral of water gets deeper. It also loses energy as it goes down the spiral. If all the vectors from the spiral are added up, the water movement is 90 from the wind direction. (Right in the north and left in the south) Convergence: In the north there are the westerlies and the trade winds. The two push water into a center of circulation making a clockwise gyre. Making a topographical high at the center of the ocean versus coastal waters. Ex. A trash island in the middle of the Pacific As water flows downhill because of gravity, the water is deflected to the right creating a clockwise pattern. Global surface ocean currents Gulf Stream: A stream of warm water that moves warm water to high latitudes. In the Atlantic Ocean brings warm water up the east coast and across the pacific to Europe (England). A coast hugging wind pushes water away from the east coast. Similar to Ox bow lakes, the Gulf Stream cuts off meandering water and creates pools of warm water in the middle of the cold ocean. Example of latitudinal redistribution of energy Climate change can be big enough to shift ocean circulation Coastal Upwelling: Ekman transport pushes H O a2ay from the coast, cold water from Deep Ocean full of nutrients come up to replace displaced water. Areas of high productivity. Why is the sea salty? (another steady state example) Physical and chemical weathering of crustal rocks on land Water flowing over or through rocks remove soluble materials (ions). Rivers carry them to the ocean. Evaporation leaves behind salts. Evaporated water runs off land bringing more ions to the ocean. Salinity does not increase because many processes remove salts. Ex. Formation of evaporate deposits, biological processes, chemical reactions with the sea floor. Salinity: Amount of dissolved materials in sea water Are found in constant proportion (conservative element) except for calcium because of uptake by biology). Salt has a long residence time because there is so much of it in the ocean and the flow in or out is relatively small. (~millions of years) Mix of ocean ~1000 years. Ocean is well mixed and mostly constant Variations in salinity are caused by regional differences in evaporation, precipitation, sea- ice formation, ice melting and river runoff. Vertical Structure of oceans: 2 layers 1. Well mixed surface layer, hundreds of km deep, warm, less salty 2. Cold deep water, sharp increase in density between layers then stable density, more salty, 80% of ocean volume. Stable density insulates deep ocean from seasonal changes in temperature and salinity Bottom water formation (Densest water produced in ocean): As water freezes, salt is pushed under because it doesn’t freeze making the water underneath the ice very cold and very salty. High salinity and low temp = very dense making it sink to the seafloor and it spreads towards the equator If effects of climate change increase, there will be less ice/cold water formed, making less water in ocean circulation = messed up ocean circulation Ex AABW (Antarctica) and NADW (Greenland) cold water currents Thermohaline Conveyor Belt: Idealized map of deep water flow and returning surface circulation. Deep water comes back up to the surface at upwelling zones moving warm and cold water like air (vertical) Combined effect of distribution of heat on Earth: atmosphere (50%) and ocean circulation (50%)
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