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Deep Water Circulation
n/a
20
Other
Undergraduate 2
10/15/2012

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Term
pycnocline
Definition

depth interval over which there is a rapid change in density

lower density on surface--> higher density on bottom

Term
importance of deep water circ
Definition
  • vertical stratification: impt for biology
  • transports heat 
  •  dissolved oxygen to deep ocean
  • stores  CO2 
Term
deep water circulation
Definition
  • aka thermohaline circulation, abyssal circluation, meridional overturning circulation, global conveyor belt
  • caused by density difference
Term
density
Definition
a function of temperature (thermo) and salinity (haline)
Term
driving mechanism for circulation in deep ocean
Definition
  • salinity 
Term
thermohaline circulation
Definition
  • driven by temperature and salinity
  • vertical structure of the deep ocean
Term
thermocline
Definition
depth over which there is a change in temperature
layer of warm water on surface and a cold layer below
Term
halocline
Definition

depth in water column where salinity changes abruptly. usually from shallow waters to deep waters (saltier)

 

Term
temperature variation with depth
Definition
  • sun heats only upper ~100m layer
  • deep water is cold
  • density and T= mirror image
  • temp has a greater effect on density
Term
deep water circulation in low lattitude
Definition
  •  strong thermocline--> stratified
    • ex. ecuador
Term
water masses
Definition
  • parcels of water exhibiting somewhat narrow range of T and S
  • N. Atlantic- deep water
  • Antarctic- bottom water
Term
returning flow 
Definition
  • mixing in the ocean brings deep water to the surface
  • indonesian through flow connects the pacific and indian oceans
  • the antarctic circumpolar current mixes deep water from all oceans and redistributes it back to each ocean
Term
the ocean conveyor belt
Definition
  • wally broecker 
  • meridonial overturning circulation
  • what drives the circulation of all ocean basins
  • drives 90% of ocean currents
  • interconnectedness of ocean currents 
Term
tracers
Definition
  • distribution of tritium in the Western N Atlantic in 1972 and 1981)
  • half-life 12 years
  • T was produced by nuclear bomb tests
  • *human pollutants can be used as tracers for deep water circulation
Term
thermohaline circulation and climate change
Definition
  • affected by excess precipitation, runoff, or ice melt
  • slowdown/shutdown of ocean conveyor 
  • belt disturbing the global heat distribution can disrupt climates 
  • varying climate change (by location)
Term
what happened 12,700 years ago?
Definition

earth emerged from Younger Dryas (lasted 1300 years)

the Conveyor belt was disrupted

Within 10 yrs, temperatures in the N. Atlantic region plummeted nearly 5° Celsius

caused the most recent ice age

  

Term
NADW
Definition
  • North Atlantic Deep Water 
  •  "start" of thermohaline circulation
  • stratification by density difference!
  • N. Atlantic: high salinity, extremely cold: dense--> water sinks
    • evaporation: temp drops, salinity rises
    • ice formation: S rises by brine rejection
Term
deep water circulation in high latitudes
Definition
vertically well mixed
Term
ARGO
Definition

deep current buoys

increase their density, sink through different layers, go along with currents, transmit information

tells how deep water circulation moves

Term
examples of tracers 
Definition
  • oxygen
  • nutrients
  • CFCs and SF6
  • radiocarbon (C-14)
  • Tritium (H-3)
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