Ocean Circulation Flashcards
what dictates ocean circulation?
wind and currents
what do ocean contain?
large currents. gyres and eddies
what are currents?
continuous streams of water than are both permanent channels and also periodic
what are boundary currents?
very large ocean currents that run along continent
- Gulf stream
what are gyres?
massive circular or spiraling circulation patterns that are thousands of km in diameter that are bordered by permanent boundary currents
-> Beaufort gyre
what affects gyres?
Coriolis effect and wind
what are eddies?
smaller circular pockets of water that break off from Boundary current
- temporary
- cold or warm depending on boundary current
- important for dispersal of animals and plankton
how does the Gulf Stream affect NY?
- brings warmer water to coast
- nutrient influx
- alters ecosystem
what is an example of what occurs in gyres?
loggerhead sea turtles stay within North Atlantic subtropical gyre
what warms the oceans?
sun
- warms the surface of ocean
- ocean warm atmosphere
- some of the radiation is absorbed and some of it is reflected (greenhouse effect)
where is there a surplus of radiation?
40N and 40S (equator)
what drives the general circulation of the atmosphere?
the sun
where is the surplus of heat energy transferred by?
atmosphere and oceans to higher latitudes
what happens when hot air rises at the equator?
increased precipitation
- air is less dense
- lose of moisture = lots of precipitation
what kind of cell is at the equator?
hadley
what happens with rising air?
takes pressure off the earth
what happens when air is cool?
more dense and falls
what kind of cells are the closest to the poles?
polar
what kind of cell is in between hadley and polar?
ferrel
what is the polar front?
extra cold area between ferrel and polar
what is horse latitudes?
- air goes down and dissipates
- not windy
- boats were moving so slowly that they threw the horses overboard
what are doldrums?
no wind bc the air is heated and only moves up
why is the wind curved?
bc of the Coriolis effect
in what direction do objects deflect in the northern hemisphere?
right
- increasing deflection of moving water parcel to the right
in what direction do objects deflect in the southern hemisphere?
left
- increasing deflection to the left
is there deflection at the equator?
no
why is there deflection?
- the earth is moving faster than the water so there is deflection -> earth’s rotation (objects at equator move faster than objects at poles
- gravity (centrifugal forces) - objects are pulled towards earth by gravity and objects are spun fast around earth by centrifugal forces
how is energy transferred from winds to the upper layer of the ocean?
through friction between the ocean and atmosphere at the sea-surface
what causes ocean currents?
friction of atmospheric currents on ocean
where does atmospheric circulation occur?
at the surface of earth
what makes circulation patterns more chaotic?
continents
- westerlies and trade winds are still evident
what drives ocean currents?
winds
what shapes water?
land
- water contained by land creating circular patterns
- more inertia in water than air
how many subtropical gyres are there?
5
what kind of currents are in subtropical gyres?
strong western boundary currents - warm water away from the equator
-> Gulf stream, Brazil currents, Kuroshio current, East Australian currents, Agulhas current
what kind of water are in strong eastern boundary currents?
cold water
- from poles to the equator
what is Ekman Transport?
- deflection of water 90 degrees
- bc of friction (of wind on water and water layers on water layers)
- leads to upwellings
what causes each successive sheet of water to deflect relative to sheet above?
Coriolis effect
what generates an Ekman transport?
wind along a coast
what is a result of an upwelling?
nutrient-rich water deeper waters move to the surface to replace water transported offshore
what are in deep waters and the result?
more nutrients and with sunlight the new nutrients fuels phytoplankton blooms which can support huge fish abundances making them productive
El Nino
southern oscillation
- equatorial current “slackens” - unknown
- warm water stays and slooshes back
- stratification of water means layers = very shallow or no thermocline
- no upwelling, no nutrients brought to surface = poor fisheries
La Nina
- equatorial current = warm water
- strong upwelling off Peru
- steep thermocline - cold deep water brought to the surface
- deep water brings nutrients to surface
- generates phytoplankton blooms, increasing zooplankton, which means lots of food for fish = good fisheries
what occurs during La Nina?
- trade winds blow across Pacific (E to W)
- generate steep thermocline and strong upwelling off Peru
what occurs during El Nino?
- warm winds blowing down along South America coast
- warm water current flow E
- thermocline drops = stratification
thermohaline circulation
- high latitude surface waters have low salinity and low temp -> high density
- dense water sinks
- moves to lower latitudes at depth
- generates a massive ocean river from Arctic to Antarctic and back
what is thermohaline circulation called?
global conveyor belt
how does cold water reheat in the south?
the upwelling brings the cold water upwards to reheat
