THERMOHALINE CIRCULATION

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THERMOHALINE CIRCULATION
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• TS Diagrams
• Global view of thermohaline circulation
• Circulation at the Straits of Gibraltar
• Atlantic Ocean thermohaline circulation
• Pacific and Atlantic temperature and salinity
  sections
• The Conveyor Belt

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Thermohaline circulation
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• Below the pycnocline
• 90 of all ocean water
• Slow velocity (10-20cm/sec or less)
• Movement caused by differences in density
  (temperature and salinity)
• Cooler seawater denser
• Saltier seawater denser

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Thermohaline circulation
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• Selected deep-water masses
• Antarctic Bottom Water
• North Atlantic Deep Water
• Antarctic Intermediate Water
• Cold surface seawater sinks at polar regions and
  moves equator ward

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Thermohaline circulation
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Fig. 7.25
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Deep ocean currents
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• Cold, oxygen-rich surface water to deep ocean
• Dissolved O2 important for life and mineral
  processes
• Changes in thermohaline circulation can cause
  global climate change
• Example, warmer surface waters less dense, not
  sink, less oxygen deep ocean

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WATER MASS

• A defineable volume of water based on its
  temperature-salinity characteristics which come
  from a particular region in the ocean

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TS Relationships
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3/18
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Thermohaline circulation
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• Originates in high latitude surface ocean
• Once surface water sinks (high density) it
  changes little
• Deep-water masses identified on T-S diagram

Fig. 7.24
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Water has unique TS characteristics because It
has a common formative origin
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Different geographic areas have different TS
curves - they act as fingerprints because each
water mass has a common formative origin with
unique properties.
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Global Thermohaline Circulation
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The Straits of Gibraltar
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Salinity and Temperature
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GYRES
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Note Mediterranean water
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The Global Conveyor Belt
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Thermohaline circulation
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Fig. 7.26
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Conveyor-belt circulation
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• Combination deep ocean currents and surface
  currents

What goes around, comes around - the time to
complete a cycle (or the residence time in the
deep ocean) is from 750-1,000 years.
Fig. 7.27