Ocean Circulation Deep Thermohaline currents. Density = mass/volume (gr/cm 3 ) D () ~(T, S)

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Transcript of Ocean Circulation Deep Thermohaline currents. Density = mass/volume (gr/cm 3 ) D () ~(T, S)

  • Slide 1
  • Ocean Circulation Deep Thermohaline currents
  • Slide 2
  • Density = mass/volume (gr/cm 3 ) D () ~(T, S)
  • Slide 3
  • Density Layered Ocean! Surface layer Ekman Spiral Pycnocline Layer Geostrophic curr. Deep Ocean Thermohaline curr.
  • Slide 4
  • 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)
  • Slide 5
  • Surface Geostrophic and Deep Thermohaline Circulation
  • Slide 6
  • 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)
  • Slide 7
  • Deep Thermohaline Circulation T, S are CONSERVATIVE properties TS properties attained at the surface Change only by mixing (Non-Conservative Properties) O 2, Nutrients Oceans are layered according to water densities!!!
  • Slide 8
  • H 2 0: Temperature and Density
  • Slide 9
  • Seawater: Temperature and Density
  • Slide 10
  • Seawater: Ice Formation
  • Slide 11
  • Seasonal changes of surface layer thermocline Surface seasonal thermocline Deep permanent thermocline
  • Slide 12
  • Latitudinal changes of surface layer salinity
  • Slide 13
  • TS Plots Represent the influence of TS on density (iso-picnolines)
  • Slide 14
  • TS Plot example
  • Slide 15
  • Example: CTD Hydrographic Survey
  • Slide 16
  • Example: CTD Casts Line A TSD http://tabs.gerg.tamu.edu/gomoms/ctddata.html
  • Slide 17
  • Example: TS Diagram for CTD Line A
  • Slide 18
  • 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
  • Slide 19
  • Deep Water Formation
  • Slide 20
  • Major Water Masses Thermohaline Circulation Central Waters (0-1000m) Intermediate Waters (1000-2000m) Deep Waters (2000-5000m) Bottom Waters (over ocean bottom)
  • Slide 21
  • Atlantic Deep Waters AABW Antarctic Atlantic Bottom Water -1.9 o C - 34.6 o / oo (cold & fresh) Forms in the Weddell Sea, during southern winter ice formation NADW North Atlantic Deep Water 4 o C - 34.9 o / oo (warm & saline) Forms by cooling of saline Atlantic surface waters during northern winters, in the Norwegian and Greenland Seas
  • Slide 22
  • Atlantic Deep Waters AIW Antarctic Intermediate Water 2.2 o C - 33.8 o / oo (cold & fresh) Forms in sub-polar regions, in the Antarctic Convergence zone Extends Northward up to 25 o N (NAIW North Atlantic Intermediate Water) MIW Mediterranean Intermediate Water 11.9 o C - 35.5 o / oo (warm and very saline) Spills from Mediterrenan over the Gibraltar Sill Forms a tongue in the Atlantic ~1000m deep
  • Slide 23
  • Atlantic Surface Waters NACW North Atlantic Central Water 24 o C - 36 o / oo (very warm & very saline) Surface waters, low density
  • Slide 24
  • Atlantic Deep Water Masses
  • Slide 25
  • Slide 26
  • Weddell Sea formation AABW
  • Slide 27
  • Weddell Sea
  • Slide 28
  • Mediterranean Intermidiate Water
  • Slide 29
  • Tracing Deep water masses TS Diagrams
  • Slide 30
  • Coriolis Effect on Thermohaline Circulation
  • Slide 31
  • North Atlantic Deep Conveyer belt 1000 year cycles
  • Slide 32
  • Conveyor Belt engine
  • Slide 33
  • North Atlantic Deep Conveyer belt 1000 year cycles
  • Slide 34
  • Pacific Ocean Thermohaline Circulation