PowerPoint Presentation by cJaxKih

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									     Ocean Circulation
Deep Thermohaline currents
Density = mass/volume
       (gr/cm3)
D (ρ) ~(T, S)
Density Layered Ocean!

Surface layer – Ekman Spiral
Pycnocline Layer – Geostrophic curr.
Deep Ocean – Thermohaline curr.
            Ocean Circulation
1. Surface Circulation  Wind Driven
  –   Ekman Transport and Geostrophic Currents
  –   Surface layer and Picnocline zone
  –   0 – 50,100m / 50,100m - ~1000m
  –   Affects ~25% of total water mass
  –   Fast (1-2 m/s)
Surface Geostrophic and Deep
  Thermohaline Circulation
            Ocean Circulation
1. Surface Circulation  Wind Driven
  –   Ekman Transport and Geostrophic Currents
  –   Surface layer and Picnocline zone
  –   0 – 50,100m / 50,100m - ~1000m
  –   Affects ~25% of total water mass
  –   Fast (1-2 m/s)
2. Deep Circulation  Density Driven
  –   Thermohaline Circulation
  –   Below Picnocline zone (>~1000m)
  –   Affects ~75% of total water mass
  –   Slow (~ m/day)
 Deep Thermohaline Circulation
• T, S are CONSERVATIVE properties
  – TS properties attained at the surface
  – Change only by mixing
• (Non-Conservative Properties)
  – O2, Nutrients


• Oceans are layered according to
  water densities!!!
H20: Temperature and Density
Seawater: Temperature and Density
Seawater: Ice Formation
 Seasonal changes of surface
      layer thermocline




•Surface seasonal thermocline
•Deep permanent thermocline
Latitudinal changes of surface
         layer salinity
                     TS Plots
Represent the influence of TS on density (iso-picnolines)
TS Plot example
Example: CTD Hydrographic Survey
Example: CTD Casts Line „A‟




 T          S                                D
                http://tabs.gerg.tamu.edu/gomoms/ctddata.html
Example: TS Diagram for CTD Line A
  Deep Thermohaline Circulation
• So… where do Deep Waters Form?
  – TS properties attained at the surface
  – TS properties remain remarkably constant
  – TS properties only altered by water mixing
Deep Water Formation
       Major Water Masses –
      Thermohaline Circulation
•   Central Waters (0-1000m)
•   Intermediate Waters (1000-2000m)
•   Deep Waters (2000-5000m)
•   Bottom Waters (over ocean bottom)
      Atlantic Deep Waters
• AABW
   • Antarctic Atlantic Bottom Water
   • -1.9 oC - 34.6 o/oo (cold & “fresh”)
   • Forms in the Weddell Sea, during southern winter
     ice formation

• NADW
   • North Atlantic Deep Water
   • 4 oC - 34.9 o/oo (“warm” & saline)
   • Forms by cooling of saline Atlantic surface waters
     during northern winters, in the Norwegian and
     Greenland Seas
        Atlantic Deep Waters
• AIW
   • Antarctic Intermediate Water
   • 2.2 oC - 33.8 o/oo (cold & “fresh”)
   • Forms in sub-polar regions, in the Antarctic
     Convergence zone
   • Extends Northward up to 25oN
   • (NAIW – North Atlantic Intermediate Water)

• MIW
   •   Mediterranean Intermediate Water
   •   11.9 oC - 35.5 o/oo (warm and very saline)
   •   Spills from Mediterrenan over the Gibraltar Sill
   •   Forms a tongue in the Atlantic ~1000m deep
  Atlantic Surface Waters

• NACW
   • North Atlantic Central Water
   • 24 oC - 36 o/oo (very warm & very saline)
   • Surface waters, low density
Atlantic Deep Water Masses
Atlantic Deep Water Masses
Weddell Sea – formation AABW
Weddell Sea
Mediterranean
Intermidiate
Water
Tracing Deep water masses
       TS Diagrams
Coriolis Effect on Thermohaline
           Circulation
North Atlantic Deep Conveyer
   belt – 1000 year cycles
Conveyor Belt “engine”
North Atlantic Deep Conveyer
   belt – 1000 year cycles
Pacific Ocean Thermohaline
         Circulation

								
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