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Geography 104 - “Physical Geography of the World’s Oceans”. Great Ocean Conveyor Belt illustration of thermohaline circulation shows link between surface and deep circulation demonstrates connectivity of the world ocean transport of energy and biogeochemical tracers - PowerPoint PPT Presentation
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Great Ocean Conveyor Belt
- illustration of thermohaline circulation
- shows link between surface and deep circulation
- demonstrates connectivity of the world ocean
- transport of energy and biogeochemical tracers
- significant link between ocean and climate (weather)
Geography 104 - “Physical Geography of the World’s Oceans”
• processes that change temperature (thermo) or salinity (haline) and thus density driven flow
• winter storms and rapid surface cooling
• freezing seawater and salt rejection
• sinking (vertical motion) of near-surface water
Thermohaline Circulation
• only very small density changes are needed
• vertical velocities are small (< 1 m/day)
• downward movement at one location must be compensated by upward movement (conservation of volume)
• resulting horizontal velocities small (< 1 cm/s)
• important for sea life – oxygen moved downward
– nutrients moved upward
Thermohaline Circulation
Water masses are defined by their T-S properties
Movement of seawater is along isopycnal surfaces
know there are a variety of water masses in the ocean……….
identifiable by their T-S properties,
with the densest waters being deepest.
Atlantic Deep Circulation
Global Conveyor Circulation
WinnipegLondon
50º
Climate differences: N. America vs. Northern Europe
WinnipegLondon
50º
Climate differences: N. America vs. Northern Europe
conveyor circulation drive:North Atlantic & Southern Ocean
conveyor circulation drive:North Atlantic & Southern Ocean
deep water formation regions
vapor export from North Atlantic
from Broecker (1997)
- arrows show water vapor transport in Sverdrups (x106 m3 s-1)- negative values show evaporation- ~15 cm of freshwater over entire Atlantic per year
North Atlantic surface salinity
North Atlantic deep water formation: North Atlantic Conveyor Drive
Curry and Mauritzen (Science, 309, 1772-1774 2005)
North Atlantic deep water formation: North Atlantic Conveyor Drive
Curry and Mauritzen (Science, 309, 1772-1774 2005)
water mass sinking
North Atlantic deep circulation
NADW
http://www-das.uwyo.edu/~geerts/cwx/notes/chap11/sea_ice.html
Antarctic sea ice formation: Southern Ocean Conveyor Drive
Antarctic bottom water formation: Southern Ocean Conveyor Drive
AABW
Southern Ocean deep circulation
AABW
Southern Ocean Conveyor Drive
S3
Salinity – Southern Ocean Conveyor Drive
AABW
NADW
AAIW
Pot. Temp. – Southern Ocean Conveyor Drive
AABW
NADW
AAIW
global Winds and PressureJuly
Westerlies
Antarctic Circumpolar Current
Ekman transport
Westerlies
Antarctic Circumpolar Current
Antarctic IntermediateWater formation
temperature-salinity of deep water masses
mixing in the Antarctic Circumpolar Current
NADW formation
AABW formationAAIW
formationfrom Broecker (1997)
mixing in the Antarctic Circumpolar Current
NADW
salinity at 2000 m
- NADW mixes rapidly in Antarctic Circumpolar Current
North Pacific water formation
19%
30%51%
North Pacific Deep Wateror Pacific and Indian Ocean Common Water
North Pacific Deep Water flow
North Pacific Deep Water Formation
salinity at 2000 m
to Indian
Ocean
to Pacific
Ocean
North Pacific Deep Water flow
SectionP18
equator 20° N 65° S
North Pacific Deep Water along 105° W
North Pacific Deep Water
Global Conveyor Circulation
Global Conveyor Circulation
choke points in surface return flow
Indonesian Throughflow
Readings (Surface and Deep Circulation):Text Chapter 9 (pgs 165 - 189)Reader pgs. 105 – 129 (Thermohaline Circulation)
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