| Basic Structures and Dynamics | |
| Ekman transport | |
| Geostrophic currents | |
| Surface Ocean Circulation | |
| Subtropicl gyre | |
| Boundary current | |
| Deep Ocean Circulation | |
| Thermohaline conveyor belt |
| Temperature | |
| warm on the upper ocean, cold in the deeper ocean. | |
| Salinity | |
| variations caused by determined by evaporation, precipitation, sea-ice formation and melt, and river runoff. | |
| Density | |
| small in the upper ocean, large in the deeper ocean. |
Density and Temperature and Salinity
Seasonal Variation of Mixed Layer
Six Great Current Circuits in the World Ocean
| Currents are in geostropic balance | |
| Each gyre includes 4 current components: | |
| two boundary currents: western and eastern | |
| two transverse currents: easteward and westward | |
| Western boundary current (jet stream of ocean) | |
| the fast, deep, and narrow current moves warm water polarward (transport ~50 Sv or greater) | |
| Eastern boundary current | |
| the slow, shallow, and broad current moves cold water equatorward (transport ~ 10-15 Sv) | |
| Trade wind-driven current | |
| the moderately shallow and broad westward current (transport ~ 30 Sv) | |
| Westerly-driven current | |
| the wider and slower (than the trade wind-driven current) eastward current |
| Western Boundary Current | |
| Gulf Stream (in the North Atlantic) | |
| Kuroshio Current (in the North Pacific) | |
| Brazil Current (in the South Atlantic) | |
| Eastern Australian Current (in the South Pacific) | |
| Agulhas Current (in the Indian Ocean) | |
| Eastern Boundary Current | |
| Canary Current (in the North Atlantic) | |
| California Current (in the North Pacific) | |
| Benguela Current (in the South Atlantic) | |
| Peru Current (in the South Pacific) | |
| Western Australian Current (in the Indian Ocean) |
Surface Current – Geostrophic Gyre
| Mixed Layer | |
| Currents controlled by frictional force + Coriolis force | |
| à wind-driven circulation | |
| à Ekman transport (horizontal direction) | |
| à convergence/divergence | |
| à downwelling/upwelling at the bottom of mixed layer | |
| Thermocline | |
| downwelling/upwelling in the mixed layer | |
| à pressure gradient force + Coriolis force | |
| à geostrophic current | |
| à Sverdrup transport (horizontal) | |
Step 2: Ekman Layer
(frictional
force + Coriolis Force)
Ekman Spiral – A Result of Coriolis Force
Mixed Layers in the Atmosphere and Ocean
Step 3: Geostrophic
Current
(Pressure Gradient Force + Corioils Foce)
Ekman Transport à Convergence/Divergence
Interior Upwelling / Downwelling
Deep Ocean Circulation: Density-Driven
Two Regions of Deep Water Formation
| Surface Water | |
| to a depth of about 200 meters | |
| Central Water | |
| to the bottom of the main thermocline | |
| Intermediate Water | |
| to about 1500 meters | |
| Deep Water | |
| below intermediate water but not in | |
| contact with the bottom | |
| Bottom Water | |
| in contact with sea floor |