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 |