Oceanography Answers

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the ____ is the source of energy on Earth
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SUN
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Sun
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Fuels atmospheric circulation ocean circulation
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Incident angle of sunlight
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1. Solar ‘footprint’ 2. Reflection (Diameter of Sun >100x Earth’s)
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Differential heating
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Excess heat from low latitudes is transferred to heat-deficit polar latitudes by both ocean and atmospheric circulation (but this occurs slightly differently in the atmosphere than in the oceans)
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Latitude
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goes horizontally
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Surplus at the equator
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heat transfers outwards to where there are deficits
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Earth’s heat budget
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Incoming solar radiation at top of atmosphere: 7 million calories per square meter per day, averaged for the Earth as a whole ( 70% absorbed mostly by ocean)
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~50% of heat absorbed at the Earth’s surface is
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returned to the atmosphere by evaporation and precipitation (latent heat)
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30% reflected
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most by clouds (the BIG unknown)
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Heat
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Sensible vs. Latent
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Evaporation is proportional to humidity
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80% of heat from the Sun (ie. infrared energy) is absorbed in the first three feet of water
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Latent heat of evaporation or condensation 540 calories per gram
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liquid water and water vapor
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range of normal ocean temperatures
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Ice and liquid water
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Latent heat of fusion or melting 80 calories per gram
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Ice
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Latent Heat Exchange
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PHASE CHANGE (Ice -[absorbs 80 cal.]-> Water -[absorbs 540 cal.]-> Vapor) (releases going the other way)
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What causes our change in seasons??
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Is it NOT how close the Earth is to the Sun during its orbit?
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The seasons occur because of the tilt of the Earth’s axis, and thereby how sunlight (energy) is distributed over the planet as we orbit around the Sun during the course of a year …
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If the Earth’s axis did not tilt, we would not have seasons!!
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Spring
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Sun aims directly at equator
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Summer
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Northern Hemisphere tilts toward sun
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Fall
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Sun aims directly at equator
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Winter
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Northern Hemisphere tilts away from sun
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23 1/2 degrees
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arctic circle between to polaris (north polar star)
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Heat transfer in the atmosphere largely occurs by
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CONVECTION
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warm air rises
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because its LESS dense
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cool air sinks
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because its MORE dense
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In reality, this is how atmospheric circulation is organized
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Coriolis effect (warm air rises, cool air falls, warm air rises, jet stream, flows west to east)
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atmospheric circulation patterns
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CORIOLIS EFFECT (stronger/faster at the poles because the radius is smaller)
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MOMENTUM ((mass x velocity) = kg x m/s)
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it’s energy you do not feel I.e.: riding in a car on the highway, walking on a moving sidewalk (it is acceleration you can feel)
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Angular momentum
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as it rotates on its axis -varies with latitude…it is greater near the Equator and less toward the Pole [1. how fast something’s going 2. how massive that things is 3. how big a circle it traces]
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Coriolis Effect
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difference in circumference (because of the radial differences) between two points on earth, it is WEAK at low latitudes and STRONGEST toward the Poles
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How does the Coriolis Effect move
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due to earth’s rotation (west to east) objects deflect to the RIGHT in the northern hemisphere and the LEFT in the southern hemisphere
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Atmospheric Circulation is governed by
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1. convection-caused by uneven heating of the earth’s surface 2. coriolis effect- caused by the rotation of the Earth
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high heat capacity of water and rock, compared with atmosphere
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most energy is absorbed by Earth’s surface, not atmosphere (heat convection occurs in the troposphere)
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Convection produces
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High (compresses and warms/down) and LOW pressure systems (expands and cools/up)
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Meteorological Equator
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zone of maximum heating
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Inter-Tropical Convergence Zone (ITCZ)
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boundary between the Easterly Winds of the Northern and Southern Hemispheres (ie. NE and SE Trade Winds) **Why does ITCZ shift further North and South around Asia and Indian Ocean? (has to do with elevation)
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Northern Hemisphere winter- ITCZ shifts south
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(in SE Asia, winds come from NE—over continental landmass that lacks lots of water –> DRY SEASON)
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Northern Hemisphere summer – ITCZ shifts North
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(in SE Asia, winds come from SW—over Indian ocean that supplies lots of water, rains out when hits Himilayas –> WET SEASON)
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Rate of CO2 increase matches fossil fuel consumption
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Half increase happened since 1980 -CO2 levels are much higher than last 800,000 years Probably (but not 100% sure) higher than last 3 million years
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Global Temperature Anomalies (1880-2013)
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13 warmest years: 2010, 2005, 2007, 1998, 2002, 2013, 2003, 2006, 2009, 2012, 2011, 2001, 2004
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CO2, 13C, 14C
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Burning, photosynthesis, old source
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last glacial maximum, last time CO2 was as high as today, CO2 could get that high by 2100
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25,000 years ago, 3-5 million years ago, 50 million years ago
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CO2 levels are much higher than last 800,000 years
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Temperature and CO2 vary together
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Megadroughts
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Medieval Megadroughts: -60 years or longer (up to 240 yr) -40% reduction in rainfall in plains states
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Dust Bowl
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1930s “Dust Bowl” -6 years -25% reduction in rainfall in plains states
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Sunspots
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-More sunspots = brighter sun -11 year cycle (brightness varies by 1%) -Longer variations in cycle (cycle average varies 0.1%)
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Base period
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1951-1980 For every place in Northern Hemisphere, how does summer compare to other summers for that place? -“Hot” means hotter than 2/3 of summers from 1951-1980 in that place. -“Cold means colder than 2/3 of summers from 1951-1980 in that place.
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“Climate Departure”
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Scientists expect that the coldest year after 2050 or so will be hotter than the hottest year through 2005.
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Air moves from
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HIGH TO LOW PRESSURE AREAS
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Storms
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-An atmospheric disturbance that generates high winds and often large amounts of precipitation -Form by interaction between or within air masses(air mass: body of air with uniform temp and humidity)
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Cyclonic Rotation
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-Warm, humid air rises -Rising air forms low pressure -Pressure gradient draws in more air -Coriolis effect drives air to right (left in South. Hemi.)
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Tropical storms (hurricanes, typhoons, cyclones)
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-develops from a disturbance within one warm air mass -draws energy from warm ocean surface (latent heat-amount of energy absorbed or released by a substance during a change in its physical state that occurs without changing its temperature) -only form between 8°-20° latitude
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How do hurricanes form?
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-really warm ocean water (atmosphere air must cool off very quickly higher you go) -wind must be blowing in the same direction at the same speed to force air upward from ocean surface (wind flows outward above storm allowing air to rise) -5-15 latitude north and south of equator (coriolis force is needed to create the spin in the hurricane and it becomes too weak near the equator)
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when levees fail
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piping of substratum, overtopping, structural impacts, overtopping/jetting
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Water Circulation in the Oceans
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Currents are masses of water that flow from one place to another Driven by WIND (Surface currents), or by DENSITY differences (Deep currents)
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Surface currents
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-Helped navigation and exploration -Influence ocean biological production -Affect climates in coastal regions (transfer heat from warmer to cooler latitudes, and vice versa)
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Surface Ocean Circulation
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-primary force is wind stress -a major secondary force is the Coriolis Effect,which interacts with the wind stress
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Ekman Spiral
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Wind stress placed on the ocean surface causes water to move, but due to Coriolis Effect it turns about 30-45° from the wind … part of this motion is transferred to the water below the surface layer, which rotates further right. This transfer of energy and rotation continues to about 100 m deep
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Ocean Gyres
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in the northern hemisphere, general water movement in the surface ocean is to the right of the winds
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Influences on Ocean Gyre Formation
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gravity is another major secondary force on surface ocean circulation
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Complete Surface Ocean Gyre
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Winds + Coriolis + Gravity
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strength of Coriolis Effect is greater at high latitudes
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(important effect on Ocean Gyres) Western Intensification
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Major N-S (boundary) currents of an ocean gyre
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Greater flow in Western Boundary Current is result of western intensification
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Western Intensification
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hill’ of water on western side of ocean basins
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Flow rates of major and minor currents in the North Atlantic ocean gyre
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Values reported as “sverdrups” (Sv), which equal1 million m3 of water per second
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Gulf Stream Eddies (It has many bends called meanders These meanders can break off to form eddies Eddies can lead to large plankton blooms)
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Eddies … formation of warm- and cold-cored ‘rings’
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Coastal Upwelling:
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Due to Coriolis Effect, northerly winds blowing along the coast move surface waters offshore (to the right) … this causes deeper waters to rise to the surface to replace them, a process called ‘upwelling
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Oceanic Upwelling
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rising of deep ocean water (from below the pycnocline) due to Coriolis Effect … brings nutrients to surface (photic zone)
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Satellite image of ocean chlorophyll
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warmer colors mean more primary production by phytoplankton
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Major Surface Ocean Currents:
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Operate in upper 300 m, except Western Boundary Currents to 2000 m
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Thermohaline Circulation (When high density water is formed –> denser water mass sinks and flows at depth)
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Water movement in the deep oceans is driven by differences in water density related to its temperature and salinity
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Vertical Structure of the Oceans
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– varies with latitude due to uneven heating of Earth’s surface – little or no thermocline at high latitudes, allows water mass to move up and down easily (vertical mixing) – strong thermocline at low latitudes, causes stratification (layering) that inhibits vertical mixing
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Ways to form high density water (1)
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1. Supercooling & sea -ice formation – colder water is more dense – ice formation excludes salt
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Flow rates of major and minor currents in the North Atlantic ocean gyre
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Gulf Stream ~55 Sv of flow ~10 Sv of flow goes into Greenland and Iceland Seas (~20% of total flow of North Atlantic Gyre) This 20% of water cools and sinks to initiate Deep-Ocean Circulation
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Ways to form high density water (2)
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2. High rates of Evaporation – saltier water is more dense – important at low latitudes (e.g., Mediterranean and Red Seas)
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Ways to form high density water (3)
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3. Densification – two water bodies mix to form denser water mass – important at ocean convergences
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Global patterns of the Ocean Conveyor Belt …
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driven by thermohaline and surface circulation patterns
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Important conditions for the formation of deep-ocean waters:
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1. Very cold climate (polar) 2. Broad, shallow sea (<1500 m deep)
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Formation of North Atlantic Deep Water
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1. Input of warm, salty Gulf Stream / N. Atlantic Current 2. Major Cooling occurs in Greenland Sea (colder water = more dense) 3. Sinking and Outflow of cold, dense North Atlantic Deep Water
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Circulation at the Southern Ocean and formation of … Antarctic Bottom Water (AABW) and Antarctic Intermediate water (AAIW)
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-AABW formed from surface water cooling below ice shelf (coldest, densest deep water) -Divergence causes upwelling -Upwelling draws NADW up, where it is transported onto the cold Antarctic shelf (Weddell and Ross seas) -Convergence causes downwelling (AAIW) -Mixing of warm,salty water with cold water (example of densification)
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Dissolved oxygen (DO) patterns in the oceans
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Atlantic Ocean – high O2 levels at depth due to continuous input of ‘young’ NADW from surface Pacific Ocean – very low O2 levels in North Pacific because waters are very old and O2 has been consumed by animals and bacteria
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SUMMARY Of Major Ocean Water Masses:
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Surface Waters – ~ 0-200 m depth – fast flow from winds, Coriolis, gravity Intermediate Waters – about 200-1500 m depth – very sluggish circulation Deep Waters – ~1500-4000 m depth – slow flow, formed in North. Hemisphere Bottom Waters – ~4000 m-bottom – slow flow, formed in South. Hemisphere

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