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Chapter 5
Homework 4 20 points Name: __________________
Due Date: WED Feb. 27 (Hand in before class) Lab: M W 1 2
Answers will be posted on the web after class to help you review for the exam.
Late assignments will be docked 5 points each day late.
Chapter 5
Define (1 point each):
See definitions at back of book
Remember you do not need to know the concept of vorticity in depth. But know what it is.
Please type answers to the following questions:
Review Questions (1, 3, 5, 9, 11) 1 point each
1. The patterns of surface winds
sets up broadly similar patterns of ocean currents underneath them (wind-driven
currents).
3. a. The Ekman spiral is the 3-D
pattern of wind-driven currents decreasing in speed and drifting progressively
to the right with depth (to the left in the Southern Hemisphere).
b. The Ekman transport is a
result of the Ekman spiral that is formed by a combination of friction in the
water and Coriolis force. Wind-driven currents at the surface drag along by
friction a layer of water below them. This water is bent to the right, just as
the wind-driven currents are with respect to the winds. That lower layer of
water drags along another layer beneath it, which is bent more to the right, and
so forth progressively deeper and progressively slower.
Ekman transport is the net movement of the water which is at a right
angle to the direction of the wind in the Northern Hemisphere.
( I think the book authors meant to say explain the Ekman spiral not
transport which is why this is a little repetitive with the critical thinking
question.)
5. A geostrophic current is one
whose motion represents a balance between the pressure force (the slope of the
water surface) and the Coriolis force. Geostrophic currents around gyres flow
clockwise (in the Northern Hemisphere) and nearly parallel to the winds.
7. (not assigned but fyi) a.
Oceanic salt comes from weathering of continental rock and volcanic releases. b.
The oceans' salinity is remaining constant because material has accumulated to
the point that it is now being lost as fast as it is being added (steady state).
9. The pycnocline is a layer
where the density of ocean water increases relatively rapidly with depth. The
halocline and thermocline are layers where salinity increases rapidly with depth
and temperature decreases rapidly with depth.
11. The thermohaline conveyor belt is the large-scale three-dimensional marine return-flow circulation caused by differences in temperature and salinity (i.e., density) in seawater.
Critical Thinking (1, 3) 2 points each
1. Ekman transport is the
movement of subsurface water perpendicularly to the right of the surface winds
and surface currents. Ekman transport makes water converge at the center of
large gyres, where it mounds up and creates a pressure force away from the
center (like an atmospheric high-pressure center). Water flowing away from the
center is deflected to the right and ultimately turned into clockwise
geostrophic flow (in the Northern Hemisphere).
In addition, the convergence of water may result in downwelling in the
center of the gyre.
3. Antarctic bottom water takes hundreds of years to reach the Pacific Basin. Effects of a stoppage would be felt much sooner than that, however, because the flow toward the Pacific would no longer be forced. Since bottom waters are for the most part not formed anywhere in the North Pacific Basin (in contrast to the North Atlantic Basin), stopped flow would have a near immediately affect (1 years - 1 decade) on temperatures of the surface water there. In the North Pacific, cold dense waters are gradually heated and rise due to the circulation pattern. The surface water would become hotter than it is now because cold waters would no longer be rising.
On the attached map, please draw red arrows showing oceanic water movement from the equatorial region northward or southward to represent warm water flow. Draw blue arrows from polar regions towards the equator. Discuss how the oceanic current patterns influence the global distribution of temperature and regional climates (Figure 401 page2 and 3 in the colored pages). Use specific examples in your discussion.
Example Discussion
Because water has a high specific heat capacity, currents transport large amounts of solar energy away from the equatorial region towards the poles. Because winds drive surface ocean circulation, the pattern of ocean circulation and its transport of heat is somewhat similar to the atmospheric transport of energy. However, because continents restrict the ocean circulation, the current pattern is altered. Cool water tends to flow up from the south along the western side of continents, whereas warm water tends to flow down from the north on the eastern side of continents. The Gulf Stream transports large amounts of heat northward creating milder climates in the UK and Northern Europe. Areas at the same latitude in North America are much colder. The Kuroshio Current warms Japan in a and the southern coast of Alaska similar manner. The current along the west coast of South America and Africa (southern portion only) are both cool, water from the Antarctica Circumpolar current as well as upwelling that occurs along these coast. Upwelling occurs due to Ekman transport that moves water away from the edge of the continent. Oceans also affect seasonal climates generally moderating climates along the coasts. There are also other examples that you may have used.