Ekman pumping Integrating the continuity equation through the layer:. Assume and let, we have is transport into or out of the bottom of the Ekman layer to the ocean’s interior (Ekman pumping). through the layer: Where and are volume transports. Assume and let, we have, upwelling Water pumped into the Ekman layer by the surface wind induced upwelling is from meters, which is colder and reduces SST., downwelling

Upwelling/downwelling are generated by curls of wind stress

Coastal and equatorial upwelling Coastal upwelling: Along the eastern coasts of the Pacific and Atlantic Oceans the Trade Winds blow nearly parallel to the coast towards the Doldrums. The Ekman transport is therefore directed offshore, forcing water up from below (usually from m depth). Equatorial Upwelling: In the Pacific and Atlantic Oceans the Doldrums are located at 5°N, so the southern hemisphere Trade Winds are present on either side of the equator. The Ekman layer transport is directed to the south in the southern hemisphere, to the north in the northern hemisphere. This causes a surface divergence at the equator and forces water to upwell (from about m).

An example of coastal upwelling Water property sections in a coastal upwelling region, indicating upward water movement within about 200 km from the coast. (This particular example comes from the Benguela Current upwelling region, off the coast of Namibia.) The coast is on the right, outside the graphs; the edge of the shelf can just be seen rising to about 200 m depth at the right of each graph. Note how all contours rise towards the surface as the coast is approached; they rise steeply in the last 200 km. On the shelf the water is colder, less saline and richer in nutrients as a result of upwelling.

Cold SST associated with the coastal and equatorial upwelling

Geostrophic flow below the Ekman layer For point B, v < 0 at 100 m and ∂w/∂z < 0. Form the local wind curls, it is expected that w E < 0 at z=-D E ≤ 100 m. Therefore, it is likely that w(z=100m) w E Since  /  z 0

Properties of Sea Water What is the pressure at the bottom of the ocean relative to sea surface pressure? What unit of pressure is very similar to 1 meter? What is salinity and why do we use a single chemical constituent (which one?) to determine it? What other physical property of seawater is used to determine salinity? What are the problems with both of these methods? What properties of seawater determine its density? What is an equation of state? What happens to the temperature of a parcel of water (or any fluid or gas) when it is compressed adiabatically? What quantity describes the effect of compression on temperature? How does this quantity differ from the measured temperature? (Is it larger or smaller at depth?) What are the two effects of adiabatic compression on density? What are σ t and σ θ ? How do they different from the in situ density? Why do we use different reference pressure levels for potential density? What are the significant differences between freezing pure water and freezing seawater?

Conservation laws Mass conservation (continuity equation), volume conservation Salt conservation (evaporation, river run-off, and precipitation, fresh water transport) Heat conservation (short and long-wave radiative fluxes, sensible and evaporative heat fluxes, basic factors controlling the fluxes, parameterizations) Meridional heat transport

Basic Dynamics What are the differences between the centrifugal force and the Coriolis force? Why do we treat them differently in the primitive equation? What is the definition of dynamic height? In geostrophic flow, what direction is the Coriolis force in relation to the pressure gradient force? What direction is it in relation to the velocity? Why do we use a method to get current based on temperature and salinity instead of direct current measurements for most of the ocean? How are temperature and salinity information used to calculate currents? What are the drawbacks to this method? What is a "level of no motion"? Why do we need a "level of known or no motion" for the calculation of the geostrophic current? (What can we actually compute about the velocity structure given the density distribution and an assumption of geostrophy?) What are the barotropic and baroclinic flows? Is there a “thermal wind” in a barotropic flow? What can you expect about the relation between the slopes of the thermocline depth and the sea surface height, based on a 1.5 layer model?

Ekman layer dynamics What is the basic forcing balance in the Ekman layer? What are the basic assumptions in deriving the Ekman’s equations and the solution? What direction is the Ekman transport? What is its magnitude? How is it related to the surface wind? Why is there an Ekman pumping? How is it related to the surface wind? What are its characters in the open ocean, near the coast, or close to the equator?