ELEMENTS OF OCEANOGRAPHY

 

TOPIC 11 - DEEP OCEAN CIRCULATION

Overheads:

Thermohaline Circulation
Changes in water temperature and salinity alter water density
Increases in water density cause water to sink until it reaches water of comparable density (stable stratification)
All water in deep oceans gets there by cooling and increased salinity
Deep ocean currents move the cold, saline waters around the world

Major Sources of Deep Water
North Atlantic Deep Water (NADW)
formed in the Greenland Seaby cooling of high salinity water
flows southward underneath the Gulf Stream
Antarctic Bottom Water (AABW)
formed adjacent to Antarctica by increasing salinity of cold water through ice formation
flows northward into all major ocean basins

Major Sources of Intermediate Water
Mediterranean Intermediate Water (MIW)
formed by evaporation of warm Mediterranean surface water
sinks to bottom, leaves through Gibralter Straits, moves across North Atlantic Ocean
Antarctic Intermediate Water (AAIW)
forms near Antarctica by mixing of AABW with cold fresh water from ice melting
moves northward above AABW

North Atlantic Circulation
NADW generated at high northerly latitudes and sinks to fill most of North Atlantic
AABW generated at high southerly latitudes and sinks to fill most of South Atlantic
AABW moves into North Atlantic underneath NADW
AAIW flows above AABW and NADW
MIW flows above NADW

Pacific/Indian Ocean Circulation
AABW flows northward and fills much of each basin
AAIW flows above AABW into both basins
North Pacific Intermediate Water flows southward in Pacific to meet AAIW
Red Sea Intermediate Water flows southward in Indian Ocean to meet AAIW

 

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