Rossby and Kelvin Waves, Upwelling, and Equatorial circulation October 15.
Ocean Circulation Deep Thermohaline currents. Density = mass/volume (gr/cm 3 ) D (ρ) ~(T, S)
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Transcript of Ocean Circulation Deep Thermohaline currents. Density = mass/volume (gr/cm 3 ) D (ρ) ~(T, S)
Density Layered Ocean!
Surface layer – Ekman SpiralPycnocline 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)
Ocean Circulation1. 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!!!
Seasonal changes of surface layer thermocline
•Surface seasonal thermocline•Deep permanent thermocline
Example: CTD Casts Line ‘A’
T S Dhttp://tabs.gerg.tamu.edu/gomoms/ctddata.html
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
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