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1519642
8: Ocean Currents
Description
College EOS 102 Mind Map on 8: Ocean Currents, created by Rachael Lee on 10/23/2014.
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eos 102
college
Mind Map by
Rachael Lee
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Rachael Lee
over 10 years ago
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Resource summary
8: Ocean Currents
currents
what drives ocean currents?
wind
friction between air and water molecules drives surface curents
friction on surface is poor
up to ~200m depth
currents get slower as they get deeper
ocean currents are 1-3% of wind speed
density differences
differences in density between water masses causes rising and sinking of these waters
water evaporatese, salinity is increased
dense water mass sinks down
surface waters flow toward the are
displaced deep waters come up
additional causes
ice formation
salt is left behind
sinks under ice into deeper water
cooling of surface waters
momentum
once water molecules are in motion, even if wind dies, the molecules will continue to flow for great distance
steering forces
coriolis effect
horizontal pressure gradients
shape of coast
deflection of currents by landmasses
pressure gradients
bulge of water sits at angle
water tries to level itself out
water flows back to where it came from
water flows form high to low pressure
major surface currents
coriolis effect northern turn clockwise
gyre: sicrulation system of water
moving heat
gulf stream warm water keeps eastern coast of n. america warm at all times
warmer relative to other places in latitude
waters right next to coast more controlled by air temp and etc
gulf stream brings mild, wet seasons to western europe
5 major gyres except by india
northern/southern/etc boundary current
names: memorize: gulfstream, antilles, etc.
ekman spiral
water mass of infinite depth
as wind blows along surface, pushes surface water molecules toward wind
net motion of this layer deflects to the right
coriolis deflection
layer beneath is pushed along same line as above (imposed force)
but slightly deflected to right
continues down to certain depth
bottom of spiral ~4% of surface current speed
each layer down is smaller due to lost energy
water moving down: ekman transport
average net motion of the water-- the direction of spiral are 90 deg from the wind
deeper waters are floating away from the coast
requirements
uniform water density (rare)
sufficient water depth
~2-day constant wind speed
thermohaline overturn engine
oceanic conveyor belt
how all of the global oceans are connected
gulf stream brings warm waters into actic
cools, more dense
turns into ice, water is salty and denser
water sinking and thus overturning
at that depth moves south then into indian ocean
upwelling and water becomes warm
brings warm water into western europe
strength in trade due to the current
coast is completely ice free
embayments in arctic due to warm water that wont sink
warm surface waters cool and sink
go down toward equator
process of "overturn" drives atlantic ocean circulation
how might global warming affect this circulation?
increase in arctic surface water temp reduces "ability" of surface waters to cool and sink
increased freshwater input from melting arctice glacial ice reduces density of cool arctic waters and its "ability" to sink
shutting down may have happened in the past
younger dryas cooling event
reconstruction of temperatures
occurred between 12700 and 11500 ya at the end of the last ice age
debate whether northern hemi only
or north atlantic only (no pacific?)
hypothesis
massive ice sheet several km thick
covering allmost all of canada and greenlad=nd
begins melting, raises sea level several levels
a lot of the water pooled in lakes
ice pushed crust down
filled lower lined crust with water
lake agassiz from laurentide ice sheet
this held more freshwater than all fresh lakes combined today
this lake drained into north atlantic as result of break up of laurentide
caused reduction of atlantic meridional overturning circulation for at least 1000 years
freshwater floating on top as a lens initially
extremely low density, than cool saltwater
pushes gulf stream south, so it doesn't touch northern europe
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