Geol 1345
Chapter 6
Review Questions:
1. Describe the vertical structure of the ocean in middle latitudes based on the variation in
temperature with increasing depth.
The ocean is divided into 3 horizontal depth zones based on density. The mixed layer,
pycnocline, and the deep layer. Mixed layer is from the surface to about 300ft. The
pycnocline is where water density increases rapidly with depth because of changes in
temperature and salinity, from 1600 to 3300 ft. In the deep layer the density increases
gradually with depth and water moves slower.
3. In the Northern Hemisphere, how does the direction of Ekman transport of ocean water
compare to the surface with direction?
It is generally in the same direction, although the Ekman transport makes it go
technically off to the right 20 degrees.
5. Contrast the surface ocean current on the eastern and western sides of the subtropical
gyres.
In the north they rotate in a clockwise direction. In the south they rotate in a
counterclockwise direction. Water on both sides of the gyres will get pulled in to the
right or to the left, depending on whether they are in the north or in the south and they
are pulled in a circular motion and converge to produce a sort of water mound.
7. Describe the role played by Ekman transport in coastal upwelling. Distinguish between
coastal upwelling and equatorial upwelling.
Coastal upwelling occurs where Ekman transport moves surface waters away from
the coast. When water that wells up from below the surface waters it gets replaced.
Deflection caused by the Coriolis effect reverses on the equator and the surface
waters are moved away from the equator, and that is equatorial upwelling.
Critical Thinking:
1. Suppose that the surface wind is blowing from the north along the Oregon coast. Predict
the direction of Ekman transport of surface waters. Would you expect coastal upwelling
or downwelling?
The Ekman transport of surface waters will be to the right of the wind blowing from
the north along the Oregon coast which will create a coastal upwelling.
3. How might rings (warm-core and cold-core eddies) influence the intensity of storm
systems over the ocean?
Rings influence the intensity of storms over the ocean based on the rings having
different measurements and impacts. Cold-core rings have diameters of about 300 km
and when viewed from above, they rotate in a counterclockwise direction. On the
north side where the warm-core ring, these rings are typically 100 to 200 km across.
From above these warm-core rings rotate in a clockwise direction. Because of the
different water temperature when combined can create a storm.
5. Define thermohaline circulation and describe how it is maintained in the ocean.
Thermohaline circulation is the deep-ocean circulation driven by variations in
density. It is maintained in the ocean through the continual diffuse upwelling of deep
water that maintains the existence of the permanent thermocline found everywhere at
low and mid-latitudes.
7. Describe the relationship between trade winds and biological productivity along the
equator.
The trade winds converge near the equator and the consequent Ekman transport
away from the equator gives rise to upwelling. This upwelling and down-welling
relationship influences sea-surface temperature and biological productivity
because upwelling waters originate at considerable depth and are usually colder
