Water Masses

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Water Masses
Philip Kreycik EPS 131 2/24/04
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Defining Characteristics

• Conservative Properties- determined by boundary
  conditions
• Temperature
• Salinity
• Non-conservative Properties- influenced by
  processes in the interior
• These do not affect the classification of water
  masses.

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Geographical Origins
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Formation of Bottom Waters

• Increased surface water density
• Role of Sea Ice
• Antarctic Bottom Water, Norwegian Overflow Water
• Bering Sea
• Cold Wind

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Temperature-Salinity Envelopes
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Polar and Subpolar Water Masses

• NADW
• Very large region of uniform temperature
• Extension to 20 degrees S
• Source in the Greenland sea (80)
• Role of Gulf stream, Arctic Outflow
• Formation in pulses

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Polar and Subpolar Water Masses

• Antarctic Intermediate Water
• Centered at 1000m
• Low salinity
• Origin south of the Polar Frontal Zone
• Antarctic Bottom Water
• 2 Types
• Very deep
• Densest water in the open ocean

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Atlantic Cross Section
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Broecker and Takahashi

• Study of the NADW
• Compositional differences can be attributed to
  proportions of end members
• Use of SiO2 and NO conservative properties
• Very significant differences between northern and
  southern components

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Broecker and Takahashi, cont.

• Other findings
• Boundaries near 33N and 33S
• Dissolved O2 and the Mid-Atlantic Ridge
• Alkalinity- cf. SiO2 and NO
• Barium concentration

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Mode Waters

• North Atlantic (Iberian Peninsula)
• Sub-Antarctic MODE Waters (New Zealand)
• Effect on Climate
• CO2, O2

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Subtropical Mode Waters

• 18 water- warm, saline (evaporation)
• North Pacific and Atlantic MODE waters

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Mediterranean Waters
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Levantine Intermediate Water

• Saltiest water mass in Mediterranean
• Forms under cold, dry conditions in late winter
  in Aegean Sea
• Westward flow- eventually contributes to the
  Mediterranean outflow into Atlantic

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Adriatic Bottom Water

• Originates in the Adriatic sea between Italy and
  the Balkans
• Exits through the Ontario Strait into the Ionian
  Sea
• Debate over its origin

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Mediterranean Outflow

• Spreads approximately from 17N to 33N
• Settles around 1000m depth- why?
• Requirements for deep sinking
• Vertical density gradient must be small
• Flow rate must be fast
• Dilution will be negligible