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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