Surface currents move at angle to wind due to Coriolis Each successive layer moves increasingly • to the right in N hemisphere • to the left in S hemisphere
Surface water flows downhill (gravity) and to the right (Coriolis effect) Balance of downhill and to the right causes geostrophic flow around the “hill”
Ocean circulation: Atlantic North Atlantic Subtropical Gyre 1. North Equatorial Current • • •
Antilles Current Caribbean Current Florida Current
2. Gulf Stream 3. North Atlantic Current 4. Canary Current
Ocean circulation: Atlantic Gulf Stream • • •
Ocean circulation: Atlantic
Warm-core rings Cold-core rings Unique biology
Average flow rate (Sv)
2
Ocean circulation: Atlantic
Ocean circulation: Indian
South Atlantic Subtropical Gyre
Indian Ocean Subtropical Gyre
1. South Equatorial Current 2. Brazil Current 3. Antarctic Circumpolar Current 4. Benguela Current
Climate Patterns: Indian
Ocean circulation: Pacific L
H L
Winter (dry!)
Ocean circulation: Pacific
1. South Equatorial Current 2. Agulhas Current 3. Antarctic Circumpolar Current 4. West Australian Current
H
North Pacific subtropical gyre 1. North Equatorial Current 2. Kuroshio Current 3. North Pacific Current - Alaskan Current 4. California Current
Summer (rain!)
Climate Patterns: Pacific Normal conditions
South Pacific subtropical gyre 1. 2. 3. 4.
South Equatorial Current East Australian Current Antarctic Circumpolar Current Peru Current
Water Properties: Temperature Average kinetic energy of molecules in a substance
• Deep currents - Driven by differences in density - Vertical and horizontal motions - Below the pycnocline - 90% of all ocean water - Slow velocity
4
Water Properties: Temperature
Water Properties: Salinity
Average kinetic energy of molecules in a substance
Total amount of solid ions dissolved in water
General relationship: ! water temp. " water density
General relationship: " water salinity " water density
Exception: When water freezes Big ! water density
Water Properties: Salinity
Water Properties: Salinity
Total amount of solid ions dissolved in water
Total amount of solid ions dissolved in water
Water temperature, salinity, density profiles
Water temperature & density profiles
Variable
Depth
5
Water salinity profiles
Ocean circulation: deep currents Deep currents, thermohaline circulation • Cold, salty, surface water sinks at polar regions and moves equatorward • Deep water formation • Antarctic Bottom Water • Antarctic Intermediate Water • North Atlantic Deep Water
Ocean circulation: deep currents
Ocean circulation: deep currents Antarctic
Weddell Sea
Ross Sea
Global conveyor belt
Ocean circulation: deep currents
Ocean circulation: deep currents
Antarctic Bottom Water
Antarctic Intermediate Water
• Sinking of cold water around ice sheet
• Convergence at the polar front
6
Ocean circulation: deep currents
Ocean circulation: deep currents
Antarctic Intermediate Water
North Atlantic Deep Water • Labrador Sea Water, Denmark Strait Overflow Water, Greenland Sea Water
Ocean circulation: deep currents
Ocean circulation: deep currents
North Atlantic Deep Water
No deep water formation in the Pacific Ocean
40S
0
40N
AIW: Arctic Intermediate Water AAIW: Antarctic Intermediate Water AABW: Antarctic Bottom Water MedW: Mediterranean Water NADW: North Atlantic Deep Water
AIW: Arctic Intermediate Water AAIW: Antarctic Intermediate Water AABW: Antarctic Bottom Water MedW: Mediterranean Water NADW: North Atlantic Deep Water CPW: Circumpolar Water PDW: Pacific Deep Water 40S
0
40N
Source: M. Tomczak
Source: M. Tomczak
Ocean circulation: deep currents
Ocean circulation:
No deep water formation in the Indian Ocean
Deep currents
AIW: Artic Intermediate Water AAIW: Antarctic Intermediate Water AABW: Antarctic Bottom Water MedW: Mediterranean Water NADW: North Atlantic Deep Water PDW: Pacific Deep Water RedSW: Red Sea Water
Source: M. Tomczak
7
Extra slides
Vertical movement of water • •
Converging surface water • • •
Surface seawater piles up Downwelling Low biological productivity • Surface water is nutrient poor • Deep water is nutrient rich
Downwelling Upwelling
Diverging surface water •
• •
Surface seawater moves away Upwelling High biological productivity
Example of diverging surface water: southeast trade winds blow across the equator
Coastal upwelling •
Coastal upwelling
Ekman transport can move surface seawater onshore or offshore
Example of Ekman transport and upwelling
8
Climate Patterns: Pacific • • •
Climate Patterns: Pacific
El Niño warm phase about every 2 to 10 years Highly irregular Phases usually last 12 to 18 months
