EVSC10001 Lecture Notes - Lecture 16: Ocean Current, Thermohaline Circulation, Thermocline

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Density decreases exponentially w/ height
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Oceans are INCOMPRESSIBLE
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Surplus of heat at equator + deficit at North and South poles
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Regions w/ clouds -> heat radiation from clouds
Deep tropics many clouds - less radiation
Subtropics have descending air -> less clouds -> radiation from surface
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Temp decrease as increase altitude in atmosphere
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Heat transport
Highest total 45 N
Tropics have very little transport
Increased latitude currents in ocean from lower to higher latitudes
60N -> north pole very little heat transport
Little currents b/w 50N -> arctic ocean b/w ocean ridges
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Surface ocean currents
Strongest from tropics to higher latitudes
Strong poleward currents on western sides of oceans driven by
westerly winds
Upper layers warmer
Mixed by wind -> mixes heat down deep
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Deep ocean currents
Very slow circulation
Driven by density, temp, and salt variations
Cold and saline
More dense -> sinks (cold water)
Thermohaline circulation
Fresh water = lighter
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Temp decrease - increased density
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Salinity increase - increased density
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Thermocline: rapid temperature decline
Slow, deep ocean circulation driven by density variations
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Halocline: saltier water deep ocean - rain forms fresh water layer -> tropics
more rain (fresher water)
Pycnocline: water density increases rapidly with depth
Largest range of temp in subtropics
Not much cloud
Large variations b/w temps in summer + winter
Increased ocean temp when sunlight strongest
Surface salinity varies
Saltier at 20N and S
Less rain
Continued evaporation
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E-P > 0 : Dry - increased salinity
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E-P < 0 : Wet - decreased salinity
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WARM
Least salty
No mixing b/c low density water
Eg. N. Australia - high temps, high rainfall, less dense water
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SALINITY:
Highest in deeper waters
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High in Atlantic - flow out of Mediterranean
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High in Pacific - evaporation
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SEA ICE:
Varies throughout year
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Ice made of fresh water
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Much more reflective than water
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Winter - provides source of salt in upper layers
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Helps maintain radiative balance of atmosphere and ocean
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Removing ice -> oceans warm
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Winter
Col temp -> sea ice forms -> salt expelled -> cold, salty water = dense -> sinks
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Antarctic bottom water - formed as ice is made - most dense
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OCEANS ROLE IN STORING/TRANSPORTING HEAT
Effective heat capacity of ocean is larger than land
Heat mixed through upper layer
More energy to heat up
Longer to heat up/cool down
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Ocean temp vary slowly
Well-defined seasonal cycle
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Surface currents example of atmosphere driving ocean
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Ocean circulation
Wednesday, 6 June 2018
3:59 pm
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Document Summary

Surplus of heat at equator + deficit at north and south poles. Regions w/ clouds -> heat radiation from clouds. Subtropics have descending air -> less clouds -> radiation from surface. Increased latitude currents in ocean from lower to higher latitudes. 60n -> north pole very little heat transport. Little currents b/w 50n -> arctic ocean b/w ocean ridges. Strong poleward currents on western sides of oceans driven by westerly winds. Mixed by wind -> mixes heat down deep. Slow, deep ocean circulation driven by density variations. Halocline: saltier water deep ocean - rain forms fresh water layer -> tropics more rain (fresher water) Large variations b/w temps in summer + winter. E-p > 0 : dry - increased salinity. E-p < 0 : wet - decreased salinity. N. australia - high temps, high rainfall, less dense water. High in atlantic - flow out of mediterranean. Winter - provides source of salt in upper layers.

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