Test Answers on Oceanography

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Four major sub-disciplines of Oceanography (4)
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1. marine geology and geophysics 2. Chemical oceanography 3. Physical oceanography 4. Biological Oceanography and Marine biology
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Marine Geology and Geophysics (4)
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1. Shape and origin of ocean floor 2. Plate tectonics 3. Geology of ocean crust 4. Origin and distribution of sediments
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Chemical Oceanography (5)
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1. Composition of seawater – exchange of material with other geochemical reservoirs 2. Distribution of elements in seawater 3. Chemical tracers of ocean circulation 4. Chemical nutrients and the regulation of biological production 5. Relationship between seawater chemistry, and changes in atmosphere CO2
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Physical Oceanography (5)
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1. Ocean Circulation – wind driven surface currents, density driven deep water movement, connections to climate 2. Ocean mixing, heat and freshwater 3. Waves 4. Tides 5. Tsunamis: a link between MG&G and physical oceanography
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Biological Oceanography (4)
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1. Distribution of marine organisms 2. Influence of biology on environment 3. Interactions between organisms and their environments 4. Biology of marine organisms, biological adaptations to the marine environment
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Ice Coverage (2)
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1. decreasing 2. Maintains earth’s temperature
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Early interests in the ocean
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1. Egyptians 3200 BC 2. Phoenicians 1200 to 146 BC 3. Polynesians 2500 BC – food, trade, navigation, colonization, exploration 4. Ancient Greece – Science and geography 384-322 BC (catalog of marine organisms, water cycling as rain)
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Middle Ages
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1. 400-1500 AD 2. Emphasis on trade and navigation 3. Scientific interest dwindled after Greeks, knowledge preserved by the Arabs 4. Then – regained interest by economic forces -current and trade routes, bathymetry and cable-laying
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Charts and Navigational Info
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1700s: interest in accurate charts and navigational techniques Spain, England offered awards for accurate sea-going clocks
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John Harrison
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Yorkshire: award for developing accurate chronometer (high accuracy clock) in 1760s -this clock was used by James Cook in 1772
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Captain James Cook
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1. made 3 voyages to chart Pacific between 1768 and 1779 2. Prevented Vitamin C deficiency and scurvy by controlling sailors’ diets 3. Observed surfing in hawaii
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Ben Franklin (1706-1790)
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Constructed 1769 Franklin-Folger chart of the Gulf Stream current to improve efficiency of shipping routes
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Matthew F. Maury
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1842: founded Naval Depot of Charts, began systematic collection of wind and current data from ships’ logs 1855: published The Physical Geography of the Sea (first oceanography textbook?) ALLOWED SHIPS TO SAIL SAFELY AND TAKE DAYS OFF SAILING TIMES
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Alexander von Humboldt
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studied currents west of South America (1799-1804)
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Charles Darwin
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survey ship Beagle described, collected, and classified organisms from land and sea, described atoll formation
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Edward Forbes
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surveyed marine life around British Isles and in the Mediterranean Sea; proposed ‘azoic’ zone below 550m
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The Challenger Expedition
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1. 1872-1876 2. Organized and funded by British Govt 3. Led by Charles Wyville Thompson – naturalist at University of Edinburgh 4. By sail and steam
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Challenger Summary
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1. 70,000 nautical miles 2. 500 deep ocean soundings – 8180 Marianas Trench 3. 133 dredge samples 4. produced 50 volumes of data
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Deepest spot in the ocean
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Challenger Deep
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Challenger – marine sediments
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1. Collected/described by Sir John Murray 2. Delineated geographic distributions 3. Recognized relationship to phytoplankton productivity in surface waters
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Late 19th and 20th century, oceanography changed from
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Descriptive to Quantitative science
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Oceanography 1970s
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More interdisciplinary research/satellite studies/discovery of hydrothermal vent system/recognition of signs of global degradation and need for policy/management
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World Ocean Circulation Experiment (WOCE)
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1. Studies world oceans using computers and chemical tracers to model and make predictions 2. Uses ships, satellites, and floating buoys with sensors
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U.S. Joint Global Ocean Flux Study (JGOFS)
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1. 1988-2003 2. Goal to understand processes regulating biologically active elements between oceans, atmosphere, and land 3. Helps predict response to climate change
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Global Ocean Observing Systems
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1991, collections of moorings, cabled instruments, sensors, collect data continuously, transmit in “real time”
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UT Marine Science Institute
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1. 1940s 2. Professor E.J. Lund 3. Conducted research to find the reasons for massive fish kills (caused by the red tide) Three Missions: Research, Education, Outreach
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Satellite Oceanography
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Measure sea surface height, temperature, chlorophyll concentrations, winds, ice coverage, water vapor, salinity, CDOM, visual data
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Data from Buoys
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1. Communicate with satellites 2. Direct measurements of ocean currents, water mass formation, air-sea interactions, ocean variability
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13.7 Billion Years Ago
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singularity explodes, universe expands and cools, with cooling less energy in particles so matter can form, many elements form in high temperature stars
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4.6 Billion Years Ago
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Earth formed – solar system originally a cloud of gas and dust set to spin by nearby explosion, collisions and gravity form planets
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Makeup of the universe
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5% – familiar matter 30% – dark matter (doesn’t interact with light) 65% – dark energy that causes universe expansion to accelerate
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2 Primary Sources of Ocean Water
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1. Outgassing from mantle (volcanic eruptions) 2. Colliding ice meteorites
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Hydrologic Cycle
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Recycles ocean water
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Earth’s water surface
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1. 71% 2. 362 x 10^6 km squared 3. 96% of water on surface in oceans (also frozen groundwater)
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Average Surface temp of Earth
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16 degrees Celsius
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Average ocean depth
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3600 meters
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Other bodies maybe with water
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1. Europa and Callisto (Jupiter moons) 2. ice-covered surfaces maybe with liquid water beneath
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Isotope
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atoms of the same element having different number of neutrons
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Radioactive Isotope
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atom with an unstable nucleus that decays over time at a constant rate
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Half-life
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time over which one half the atoms of a radioactive isotope decay
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Year
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time for Earth to orbit sun
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Seasons
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time between equinoxes and solstices
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Month
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approximate time of moon’s orbit around Earth
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Week
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Phases of the moon
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Rotation of the moon about the earth
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Tides
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Earth’s tilt + resulting seasons –> differential heating –>
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hydrologic cycle, atmospheric and ocean circulation
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Polar radius is
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Shorter than equatorial radius
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Lines of Latitude
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1. Equally spaced, parallel to equator 2. one minute – 1/60 of a degree = 1 nautical mile
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Lines of Longitude
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1. Converge at the poles 2. One minute = 1 nautical mile only at the equator 3. Also called meridians
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Determining Position with Latitude
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Measure the elevation of a celestial body (such as North Star) above the horizon using a sexton
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Determining Position with Longitude
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Each hour the Earth rotates 15 degrees West to East, can measure relative to the sun
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Process of Longitude and Time
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Sun is at it’s highest point at noon 1. Note the time at which the sun reaches the zenith at your location (local noon time) 2. Difference between your reference time and the local noon times gives your longitude (15 degrees west or east for each hour)
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Earth’s Water Reservoirs
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1. Less then 3% is fresh 2. about 1% is drinkable and available to sustain people
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Flux
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Movement, expressed as a rate (amount per time) of material between 2 compartments
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Residence time
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Average time a molecule of a substance spends in a compartment, or the time it would take to fill a compartment with that substance Residence time = inventory/flux Mass/(mass/time) = time
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Residence time of water in the atmosphere
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11 days
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P Wave
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Primary wave, (fastest, compressional)
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S Wave
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Secondary wave, shear wave (slower, up/down, cannot propodgate in liquids
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Surface Wave
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Late
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Mantle
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Solid, Mobil, Heterogenous; 70% of earth’s volume
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Crust
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Solid, Continental (thicker) & oceanic (thinner)
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Moho
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Separates regions of distinct chemical structure (between crust and mantle); know from exposed rocks on surface
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Continental Crust
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30-40 km thick
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Oceanic Crust
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1. 6-7 com thick 2. Uppermost mantle: behaves rigidly, fused to and moves with overlying crust, together the lithosphere
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Asthenosphere
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underneath lithosphere, less rigid, partially molten
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Mesosphere
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lower mantle, fully solid, but thought to move slowly up or down
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Isostasy
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1. Buoyant support of lithosphere by asthenosphere 2. Thicker, less dense continents float higher than more dense and thicker oceanic crust 3. tall mountains have deep roots
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Movement of Continents
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1. Evidence for a supercontinent 2. Subsidence theory of separation 3. Continental Drift (alfred wagner)
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Subsidence Theory of Separation
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Thought that isostatic changes cause continents to break up (but its not strong enough)
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Wegener’s Evidence
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1. Fit of Continents 2. Fossils 3. Rock Types 4. Indications of glaciations
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Seafloor spreading
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Basaltic magma extruded at ridges rift valley creates new ocean floor
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Spreading Centers
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Rift valley areas in ridges create new crust
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Evidence for Crustal Motion
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1. Bathymetric maps 2. Distribution of earthquake epicenters 3. Heat flow 4. Sediment age, and thickness 5. Radiometric measurements for age of land and sea floor rocks 6. Paleomagnetism
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Bruce Heezen and Marie Tharp
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First global maps of the sea floor -delineation of the mid-ocean ridges, significance for plate distribution -trenches, seamounts
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Seafloor Magnetism
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When oceanographers measure the magnetic fields from ships, the find PARALLEL STRIPES OF EQUAL AGE. This led to the prediction that such zones would be found around all oceanic ridges
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Magnetism
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The primary tool used to create maps of seafloor age today
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Polar Wander
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1. Exact position of the north pole moves through time even during period of “normal” polarity 2. Reconstruction of “apparent polar wander”
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Divergent
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Constructive
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Convergent
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Destructive
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Transform
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Conservative
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Theory of Slab Pull
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thick, dense crust sinks and drags remainder of plate
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Hot Spots
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1. regions where mantle material rises 2. can be mid-plate
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Seamounts, Guyots
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Plates move over hot spots, creates series of new volcanoes
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Hydrothermal Vents
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1. Venting of high temp fluids along mid-ocean ridges: circulation of seawater through newly formed crust 2. vent plume enriched with sulfur, metals, volatile gases
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Fathom
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6 feet
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Earliest method for measuring depths
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Hand line and wire marked with fathoms – lead weight on the end (shallow water)
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Echo Sounder
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depth recorder
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Laser Airborne depth Sounder
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1. uses light instead of sound 2. in shallow water (<70 m)
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Satellites
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1. Uses gravity’s effect on sea surface 2. seamounts pile water up 3. trenches cause dips and depressions in sea surface
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Multi-beam sound systems
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1. side-scan sonar system 2. Swath bathymetry
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Biggest difference in ocean floor as opposed to land
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1. slow rain of sediment in the ocean 2. little weathering compared to land 3. the conveyor belt of plate tectonics
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Active Margin
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Pacific, tectonically active, plate convergence/subduction; narrow/steep
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Passive Margin
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Atlant, little seismic activity; transition from continental to ocean crust in same plate; wide, broad, shallow
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Formation of Continental Shelves
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1. Geologically part of continent 2. Exposed in past glaciations 3. Accumulate sediments from various sources 4. Average about 65 km in width 5. Depth at edge of shelf averages 130 m
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Submarine Canyons
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1. Formed during lower sea levels, can be scale of grand canyon 2. Extensions of moden rivers
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Power of Turbidity Currents
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1. Impressive features, can move 90 kph for 100s of km 2. Detected in past by breaks in telegraph cables 3. carry a suspended material 300 kg per m cubed 4. material is sorted and when deposited creates graded deposits: turbidites
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Ocean Basin Floor
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1. Abyssal Plain (flattest on earth) 2. Abyssal Hills (<1000 m high) 3. Seamounts (steep sided volcanoes) 4. Guyots (flat topped seamounts)
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Ridges/Rises
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Spreading centers, hydrothermal vents
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Trenches
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-Deepest spots in the ocean, majority in the pacific -island arc systems
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Neritic Sediments
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more variable than Pelagic sediments, accumulate much faster
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Terrigenous Sediments
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1. from terrestrial source 2. present everywhere 3. finest sediment occurs in abyssal plains and is called red clay: iron rich abyssal clay
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Most iron is supplied to the ocean by
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Dust
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Biogenous Sediments
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1. from remnants of living organisms 2. usually unicellular organisms, corals Calcareous – calcium carbonate Siliceous – silicate
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If sediments are more than 30% biogenous, then they are termed
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OOZE
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Calcareous Sediments
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1. remains of coccolithophorids 2. Pteropods (snails) 3. Foraminifera (protozoans) 4. Chalk originally from calcareous deposit 5. Depth that dissolution first starts to occur: lysocline
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Siliceous Sediments
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1. remains of small phytoplankton shells (diatoms) or protozoans (radiolarians) 2. Soluble everywhere in seawater (mostly in shallow warm waters) 3. about 90% dissolved in water or sea floor
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Carbonate Compensation Depth (CCD)
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1. Depth at which less than 20% of total sediment is preserved calcareous material 2. Depth at which downward flux = dissolution into seawater (4500 m)
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Hydrogenous Sediments
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Formed by chemical actions of seawater, precipitation of minerals 1. Carbonates 2. Phosphorites 3. Salts 4. Manganese Nodules
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Cosmogenous Sediments
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Origin from space
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Coarse sediments located
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closer to shore
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Finer sediments located
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offshore due to easy transport
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Terrigenous sediments located
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in estuaries or river mouths
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Corer
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1. Used to sample sediments 2. Long metal tube that collects a length of sediment. Limited to upper 20 m or so.
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Acoustic Profiling
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1. Uses sound to profile sediments 2. Penetrates sediments 3. Oil exploration companies
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Methane Hydrate
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1. Methane trapped in water 2. potential future energy source 3. Global climate 4. Sediment strength
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Manganese Nodules
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1. Metal rich lumps sitting on or in sediments – size of golf balls 2. Internal rings change in chemistry during formation 3. Grow slowly in open ocean
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Polar Molecule
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Slight asymmetry in charges
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Hydrogen Bonds
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Weak attraction based on charge asymmetry
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1 Calorie
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Amount of energy needed to raise 1 gram of water 1 degree celsius
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Heat Capacity
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1. Quantity of heat required to produce a unit of change in temperature 2. Hydrogen bonds give water high heat capacity
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Cohesion
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Attraction between electric charges
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Surface Tension
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measure of how difficult it is to stretch or penetrate the surface of a liquid
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Viscosity
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resistance to motion or internal friction
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Density
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Mass per unit volume
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Density of ice is
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Less than density of water
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Density of moist air is less than
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density of dry air
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More salt at a given temperature equals
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higher density
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Caballing
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when cold fresh water mixes with warm salty water at same density
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For salinities less than 24.7%
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Liquid water will reach a density maximum about the freezing temp
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Pressure has a very small impact on
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Density
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“Universal Solvent”
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Water
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Energy is attenuated at depth
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absorbed, reflected, or scattered
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Amount of attenuation depends on
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wavelength -long wavelengths absorbed more readily, blues scattered more
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Attenuation Coefficient (k)
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expresses ability of water to reduce light
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Secchi Disk
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Simplest device to measure light
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Speed of sound in water
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faster than in air water: 1500 m/s air: 334 m/s
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3 types of fog
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Advective Fog Sea Smoke Radiative Fog
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Advective Fog
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warm, water-saturated air passes over cold water, condenses to fog
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Sea Smoke
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dry, cold air moves over warm water, forms wispy streamers
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Radiative Fog
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warm, moist air cools at night and condenses, heats up again during the day and disappears
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Most important ions in sea
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1. Chloride 2. Sodium 3. Sulfate 4. Magnesium 5. Calcium 6. Potassium
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Processes that affect salinity
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1. Evaporation 2. Precipitation 3. Runoff 4. Freezing 5. Thawing
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Sources of Salt
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1. Positive ions: weathering and erosion 2. Negative ions: gases from volcanic eruptions
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Deep Seawater chemistry
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cold, oxygen rich, low in metals, slightly alkaline
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Vent Fluids chemistry
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Hot, zero oxygen, metal-rich, acidic
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As temperature increases, solubility
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decreases
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Distribution of gases strongly linked to
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1. local water conditions 2. biology 3. bottom topography
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Gulf of Mexico “Dead Zone”
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1. seasonal development of hypoxic (very low oxygen) conditions in a large area 2. nutrients from fertilizers in mississippi river basin stimulate phytoplankton production in gulf 3. when these phytoplankton sink to bottom, decomposition of them consumes oxygen 4. Benthic “bottom dwelling” organisms cant escape low-oxygen waters and die
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Compensation Depth
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Where photosynthesis and respiration balance
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Respiration & Decomposition
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Produce CO2 and remove all O2 at all depths
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Photosynthesis
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Removes Co2 and Produces O2 at the surface
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Carbon Dioxide Cycle
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1. Oceans uptake carbon dioxide from atmosphere 2. depends on pH, temp, salinity, chemistry 3. Biological pump transports carbon to deeper ocean
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Coriolis Effect results from
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differences in velocity with latitude
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El Nino – Southern Oscillation (ENSO)
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1. atmosphere-ocean coupling 2. originates in atmosphere of tropical Pacific 3. first recognized as ocean changes near Peru
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Normal Pacific Ocean Conditions
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1. Low pressure north of Australia 2. High pressure in Eastern South Pacific 3. Strong Trade Winds 4. Warm moist air rises over Indonesia 5. Dry air descending over S. America
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El Nino Conditions
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1. surface pressure in indonesia higher 2. trade winds weaken or reverse 3. deep, warm water moves east 4. upwelling weakens in eastern pacific
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La Nina Conditions
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enhanced pressure gradient, strong trade winds leas to cooler conditions in Eastern Pacific
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Consequences of El Nino
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1. Warm winters in Northern US and Canada 2. High rainfall in eastern US and western South America 3. Drought in western Pacific 4. Less intense hurricane seasons 5. Fisheries collapse in South America
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Temperature and Salinity together determine
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Density of seawater
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Annual Cycle of Temp in Surface Waters
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1. Warming in summer leads to stratification and isolation of surface waters 2. Cooling and the passage of storms in the winter leads to deeper mixing 3. Brings nutrients to the surface 4. High latitude oceans have deeper winter mixed layer
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Thermohaline Circulation
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vertical circulation caused by density changes
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Main driving force of Thermohaline Circulation
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1. high latitude cooling 2. turbulent mixing of heat
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Deep water is formed and sinks in 2 main regions
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1. northern North Atlantic 2. Weddell Sea
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Major Deep Water Masses
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1. North Atlantic Deep Water (NADW) 2. Antarctic Bottom Water (AABW)
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Intermediate-Depth Water Masses
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1. Antarctic Intermediate Water (AAIW) 2. Mediterranean Water 3. N Pacific Intermediate Water
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Upwelling and Downwelling
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Caused by density-driven currents as well as wind-driven currents; vertical motion is much slower than horizontal flow
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Easterlies
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East to West
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Westerlies
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West to East
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If at equator moving north
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deflected right
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If at equator moving south
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deflected left
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The Ekman Spiral
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1. the next layer down moves more slowly 2. the surface water movement is about 45 degrees to the right of the direction of the wind 3. the movement of each successive layer is offset to right and lesser in strength 4. SO, the NET motion of the water is 90 degrees to the wind (Ekman transport)
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Geostrophic balance
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1. gravity is forcing elevated water downward from surface slope, but Coriolis effect deflects water to center 2. Geostrophic flow, the Coriolis effect and gravitational force balance each other, currents flow smoothly around elevated center of gyre
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Eddies
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1. currents dont just flow in straight lines 2. have oscillations and meanders 3. can break off to form giant eddies
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Upwelling
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Occurs along divergence zone
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Downwelling
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Occurs along convergence zones

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