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68 Cards in this Set
- Front
- Back
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what are the two types of ocean currents?
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wind driven and density driven
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Analogy:
Surface Currents-Wind, Deep Currents- _______ |
density
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what are two main methods to directly measure currents?
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1. a floating device is track over time
2. propeller devices |
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what are some tracers used to measure ocean currents?
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Tritium and CFCs
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About what percent of the wind's energy is transferred to the ocean surface?
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2%
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If there were no continents on earth, surface currents would.............
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follow the major wind belts of the world
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what is the maximum depth of surface currents?
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1 km (the pycnocline)
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surface currents influence what percent of the ocean water?
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10%
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the gulf stream and the brazil current are examples of what type of currents?
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western boundary currents
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the canary current and benguela current are examples of what type of currents?
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eastern boundary currents
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how many gyres are there in the world, and what are they?
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5; N and S Atlantic gyres, N and S Pacific gyres, and Indian Ocean gyre
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how many currents make up a gyre?
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4
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what are the four currents that make up the N Atlantic gyre?
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Gulf stream, N Atlantic current, Canary current, and N Equatorial current
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in what direction to gyres roate in the N hemisphere? S?
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N = clockwise
S = counterclockwise |
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who first observed that surface currents moved in a direction different from the wind?
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Fridtjof Nansen, during the FRAM voyage
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what does the Ekman model assume?
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a uniform column of water is set in motion by wind blowing across its surface
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what is the average movement under ekman transport?
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90 degrees to the right in N Hemisphere and to the left in S hemisphere
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a geostrophic current is balanced by what two effects?
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the coriolis effect and gravity
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what is western intensification?
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western boundary currents of gyres are narrower, faster, deeper, and deeper than other currents of the gyre
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give examples of western boundary currents
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gulf stream, brazil current, kuroshio current
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give examples of eastern boundary currents
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canary current, benguela current, california current
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why is the south pacific gyre less intense than other gyres?
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it covers a large area and lacks confinement by continents
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what does a warm coastal current mean for the climate of the adjacent landmass?
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low pressure, high precipitation
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what does a cold coastal current mean for the climate of the adjacent landmass?
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high pressure, low percipitation
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why are upwelling and downwelling important?
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they provide important mixing mechanisms between surface and deep waters
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what is the importance of equatorial upwelling and how is it accomplished?
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it creates areas of high productivity near the equator; since the meteorological equator is a few degrees latitude to the north, ekman transport causes surface water north of the equator to veer to the right and water south of the equator to veer to the left
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give an example of downwelling where surface waters converge
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in the N Atlantic ocean, the gulf stream, the labrador current and E greenland current converge and cause downwelling
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why are upwelling and downwelling common in high latitudes?
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the absence of a pycnocline allows significant vertical mixing between high density cold surface water and high density cold deep water below
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name 3 ways upwelling can be caused
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1. offshore winds
2. a seafloor obstruction, such as a table mount 3. a sharp bend in coastal geometry |
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describe the antarctic convergence
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colder, denser, antarctic waters converge with and sink sharply below aarmer, less dense sub antarctic waters; occurs at 50 degrees S latitude
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what is the driving force behind the West Wind Drift (aka Antarctic Circumpolar Current)?
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powerful prevailing westerly wind belts
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what is the only current that completely circumscribes the earth?
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the antarctic circumpolar current; aka west wind drift
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what is the surface velocity of the antarctic circumpolar current?
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2.75 km/hr
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what is the flow rate of the antarctic circumpolar current?
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130 Sv.
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what is the driving force behind the East Wind Drift?
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the polar easterlies
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why does the boundary between the East wind drift and West wind drift create a high abudnance of marine life?
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the two currents move in opposite directions, so they bring up deep, cold, nutrient rich water
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what is the best studied of all ocean currents and is also the fastest current in the world?
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the gulf stream
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why is the eastern boundary of the gulf stream difficult to identify?
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because it is usually masked by meandering water masses that change their position continuously
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where is the Sargasso sea located?
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in the Atlantic, near the eastern US coast
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what happens to the gulf stream as it moves eastward?
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it gradually merges with the water of the Sargasso sea
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what's the transport rate of the gulf stream off Chesapeake bay? off NewFoundland?
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100 Sv. near Chesapeake; 40 Sv. near Newfoundland
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why are warm core and cold core rings (eddies) important to marine life?
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they provide isolated habitats for either warm water organisms in a cold ocean, or conversely, cold water organisms in a warmer ocean
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is the gulf stream rich in marine life?
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the gulf stream itself isn't, but its boundaries are
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what is the importance of the gulf stream to the coast?
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it moderates temperatures along the East coast of the US and the West coast of N Europe
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why is the Kuroshio current (aka Japan current) important to Japan?
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it makes Japan's climate warmer than would be expected based on its latitude
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in terms of temperatures, what is the difference between western and eastern boundary currents of a gyre?
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western currents are much warmer than eastern ones
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how does a geostrophic current ideally flow?
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in circular paths around the hill of a gyre.
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One of the first indications that an El Niño event may be occurring is when...
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water from the Pacific Warm Pool migrates across the equatorial South Pacific Ocean from near Australia toward South America
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The circulation cell in the equatorial South Pacific created by the movement of air between high- and low-pressure regions is called the......
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Walker Cell
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The ocean's deep water is initially formed at the ____________, and in __________ regions
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surface; subpolar
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Thermohaline flow is a term that describes............
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deep ocean current movement
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True or False? Subtropical gyres flow counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere
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False
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True or False? Vertical mixing of surface and deep seawater takes place in the low latitudes
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False
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why does western intensification "happen"?
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because a gyre's center is located to the west of the ocean basin's geographic center
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the california current is [Warm / Cold] and flows [North / South]
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Cold....South
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the gulf stream is [Warm / Cold] and flows [NorthEast / SouthEast / SouthWest]
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Warm....NorthEast
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the peru current is [Warm / Cold] and flows [North / South]
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Cold....North
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the E Australia current is [Warm / Cold] and flows [North / South]
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Warm...South
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the West Wind drift is [Warm / Cold] and flows [West / East]
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Cold...East
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What are some effects of El Nin~o?
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1. trade winds cease or flow in reverse direction
2. ocean temperatures increase near peru and decrease near indonesia 3. upwelling reduced near peru 4. heavy rainfall in peru 5. droughts in indonesia 6. droughts in parts of Asia and Africa 7. forest fires in Australia 8. coastal erosion in California |
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ENSO is most closely associated with what circulation cell?
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Walker Ciculation Cell
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what's the effect of El Nino on marine iguanans of the Galapagos?
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they shrink because of limited food sources
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how often do El Ninos (Los Ninos) occur?
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2-10 years according to Thurman, but 3-5 according to Segar
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how long do El Ninos (Los Ninos) last?
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12 to 18 months?
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When did 2 of the most sever El Nino events of the 20th century occur?
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1982-83 and 1997-98
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what is Pacific Decadal Oscillation (PDO)?
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a phenomenon which lasts 20-30 years and appears to influence Pacific sea surface temperatures
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what was the impact of the 1976 El Nino on the US?
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it coincided with California's worst drought and the Eastern US experienced record cold temperatures
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when was the strongest El Nino ever recorded? what were the effect?
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1982-83; warming in tropical pacific; sea level was higher and lots of coastal erosion in western pacific; jet stream swung farther south; lots of rainfall in SW US; flooding and landslides anf lots of snowfall in Rocky Mtns; Peru = lots of rainfall; French Polynesia, which had not experienced a hurricane in 75 yrs, experienced 6; Overall 2K Deaths and $10 Billion property damage
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