GEO-SCI 103 Lecture 12Outline of Current Lecture: Thermohaline Circulation and the Global Conveyor (pgs. 144-147)I. Density Driven Downwelling and Thermohaline CirculationA. Temperature and salinityB. ThermohalineC. Neutral BuoyancyD. Deep Waters E. Intermediate WatersF. Thermohaline CirculationII. The Global Conveyor: World Ocean CirculationA. Global Conveyor B. Net Export of Deep Water and Net Import of Surface water into AtlanticC. Conservative PropertiesD. Non-Conservative PropertiesE. What extracts Oxygen and produces CO2F. Oxygen and Carbon Dioxide in water mass Current LectureI. Density Driven Downwelling and Thermohaline Circulation A. Temperature and Salinitya) The differences in temperature and salinity that can occur among different oceanic water masses stimulate a very different kind of circulation system. b) Cold dense waters are formed by the intense winter cooling and sea ice formation in the polar seas because there is an absence of a pycnocline (density barrier)B. Thermohalinea) These dense waters move toward the equator beneath the pycnocline as “deep” or bottom waters (<4 degrees Celsius or <40 degrees F) to fill the entire world ocean below the pycnoclineb) Density driven circulation of the deep ocean c) Both temperature and salinity are IMPORTANT in the production of deep and intermediate water massesThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.d) Also includes the production and circulation of “intermediate” water massesC. Neutral Buoyancya) Intermediate and deep waters sink to their level of density equilibrium below the solar warmed surface watersb) There is a vertical component of thermohaline circulation related to the downwelling of dense waters c) Much of the motion is related to horizontal flow through the ocean basins of the world D. Deep Waters: influenced by the Coriolis Effect resulting in strong western boundary currentsa) Form only in the Atlanticb) North Atlantic Deep Water (NADW) forms in the northern North Atlantic (Greenland and Norwegian Sea)c) Antarctic Bottom Water (AABW) forms in the southern South Atlantic d) Some of this water flows along the continental slope of Antarctica to enter the Indian and Pacific Oceane) The deep waters of these ocean basins are a mix of NADW and AABW called Circumpolar Water (common water)f) as deep water flows toward the equator beneath the pycnocline, they hug the lower continental slopes and rises on the western sides of the ocean basinsE. Intermediate Waters a) Less dense and are produced in smaller volume than deep watersb) Antarctic Intermediate Water (AAIW) forms at the Antarctic Convergence (Polar Front), then sinks and flows north into the South Atlantic, Caribbean Sea, Gulf of Mexico and North Atlantic c) Mediterranean Intermediate Water (MIW): warm, salty water mass-produced in the Mediterranean sea due to high evaporation rates in thesubtropics. 1. Among the densest waters formed in the ocean. Sinks to about 1000 m and turns toward the North Due to Coriolis effect.2. Provides an important source of salt for the winter production of the North Atlantic deep water F. Thermohaline Circulation: Vertical Circulation in the ocean that is driven by temperature and salinity differences in the various ocean water massesa) Important because it ventilates the entire water column of the world ocean below the pycnoclineb) The motion of intermediate, deep and bottom waters redistributes heat, salt, dissolved gases and nutrients c) Relatively slow compared to wind driven surface circulationd) Intimately linked with wind driven circulation above the pycnocline to create a “global conveyor” of the world ocean circulation e) Also caries away some of the excess carbon dioxide and other greenhouse gasses that have been rapidly building up in our atmosphere due to the burning of fuelII. The Global Conveyor: World Ocean CirculationA. Global Conveyor a) Describes the complete circuit of global ocean circulation involving horizontal flow of surface and deep waters and the vertical flow of downwelling and upwelling b) Waters of the thermocline and surface mixed layer move UNDER the influence of WIND DRIVEN CIRCULATIONc) Waters below the permanent thermocline (and pycnocline) move by DENSITY driven THERMOHALINE CIRCULATION d) The surface and ocean currents of the world are connected to the thermohaline circulation system by the upwelling and downwelling that occurs at various locations in the ocean B. Net Export of Deep Water and Net Import of Surface water into Atlantica) Surface waters cool and sink in the Atlantic and spread to fill all the ocean basins of the world with cold deep waters b) Coastal upwelling at the margins of the ocean, around the Continent of Antarctica and in the equatorial Pacific return waters to the surfacec) Surface currents return these waters back to Atlantic C. Conservative Propertiesa) Deep and intermediate water masses acquire their physical and chemical characteristics at surface where they formb) Properties include: temperature, salinity and density, which are considered conservative because they are modified only by the diffusion of mixing with other water masses. D. Non-Conservative Propertiesa) Other properties acquired at the surface include nutrients and dissolvedgasses (oxygen and carbon dioxide) which are non conservative properties because they are modified by biochemical cycles, even though the water masses retains its temperature and salinity signatureb) Because cold-water holds more dissolved gasses than warm water, deepwaters are initially oxygen rich. However, these waters lose oxygen overtime due to animal respiration and decomposition of organic matter E. What consumes oxygen from ocean and produces CO2?a) Cold water loses oxygen overtime from:1. Animal respiration2. Decomposition of organic matterF. Oxygen and Carbon Dioxide in water massesa) The OLDER the water mass, the LONGER it has been away from the surface and consequently its Oxygen is LOWER and the Carbon dioxide content is HIGHER (North Pacific)b) Rich in Carbon Dioxide and nutrients accumulated by respiration and decompositionc) Accumulation of nutrients in deep waters as they age is due to rain (flux) of organic matter out of the surface oceanBiological Pumpd) Biological Pump1. Bacteria breakdown the organic matter thereby releasing carbon dioxide and nutrients in the process. 2. The