HAS 221A OCEANS and the GLOBAL ENVIRONMENT
DISCOVERY SEMINAR 2008
QUIZ 2
The quiz Wednesday morning will consist of 4 questions chosen from the following:
1. We have seen that ocean gyres and hurricanes inherit the rotation of the Earth. Thus we
have gyres in the subpolar latitudes that are 'cyclonic', that is, they rotate in the same sense as
the Earth . Yet some ocean gyres and some ocean eddies rotate in the opposite direction to
the Earth. Show that this is possible by considering the ‘figure skater’ effect (the change in
spin as he draws his arms inward or outward) when viewed as an observer on a rotating
Earth.
o Which gyres of ocean circulation rotate this ‘opposite’ (anti-cyclonic) way?
2. If an ice cube floating in a glass of water melts,
o does the water surface go up, go down or stay the same?
o If it the water is salty, what sort of convective circulation do you expect will occur as
the ice melts. Does it depend on the salinity of the water?
3 The UW wetlands that we visited experience, over the year, about 2 ½ feet of rise and fall
of the lake surface during the year (low in late summer).
o How might this affect the ecosystem of the wetland?
4. Give examples (at least two) of small creatures you have encountered in our samples
from Lake Washington and its wetlands, where they seemed supremely well adapted to the
tasks they are performing: sensing, chasing, eating, building, hiding, escaping. You don’t
need to know their names.
5 o What is the carrying capacity of osprey in the Montlake Fill?
Assume that an Osprey needs to each 2 40 gram fish every day to survive, and that the fish
eat daphnia and copepods, lets say that they need 2 grams of these freshwater zooplankton
everyday. The zooplankton eat their weight in phototrophic flagellates everyday (they weigh
about 10 milligrams). The Phototrophic flagellates multiply once per day, and live in the top
meter of water. What surface area of lake water is required for an osprey to survive? Note:
Julie is working on a revised version of this question!
6 Beavers are a keystone species because of the vegetation they eat.
o Hypothesize what the Montlake fill would look like without Beavers.
7. We have looked at ocean gyre circulations and ocean conveyor belt circulations.
o Describe these two kinds of circulation, and in particular, which one would you expect to
change the most in the next Ice Age? (During the past 2 million years, glaciation (ice ages)
have occurred which created deep ice sheets on North America and Eurasia. The ice cove
reached from the North Pole to Seattle's latitude; there was much less change in the
Southern Hemisphere).
(turn over)
8. The amount of fresh water contained in Greenland's ice, if it melts, will raise the sea
level about 7 meters over the entire Earth. If this happens in 100 years,
o how many Sverdrups (1 Sverdrup = 1 million cubic meters per second) of outflow will
that be? How many Amazon Rivers (Amazon River flow averages 0.2 Sverdrups). The area
covered by oceans is about 3.7 x 1014 square meters.
o If Greenland's ice melts, what are some possible effects on the ocean circulation of the
Atlantic?
9. o Make a 'spherical cow' estimate of the residence time of carbon in vegetation (1) on land
and (2) in the oceans? (Hint: first take a guess based on the apparent lifetime of plants that
you know).
o What does the answer tell you about the parts of trees that are dominating this
residence time of carbon?
{We estimate that net primary productivity of ocean phytoplankton is
2.5 x 1013 kg carbon per year, and the total mass of marine plants is on the order of 2 x 1012
kg. Similarly the net primary productivity of land plants is very roughly 5 x 1013 kg/year
and the stock of living biomass on the continents is 5.6 x 1014 kg. }
10 We saw that the Atlantic Ocean is saltier and warmer than the Pacific Ocean. We know
that this is partly explained by the greater evaporation of water into the atmosphere, in the
Atlantic (as compared with the Pacific). We also observe that cold, dense waters sink in the
northern Atlantic and flow into the other oceans.
o How do we fit this together as a 'conveyor belt' circulation?
o Given that nutrients in the ocean are concentrated near the bottom, will this circulation
cause the nutrients to be more concentrated or less concentrated in the Pacific, as compared
with the Atlantic?
11. The world’s oceans are built of many layers of different density. Both salinity and
temperature affect the density of ocean water. .
o Describe how and where salinity and temperature variations originate and appear on
layers in the upper, middle and deep ocean.
12. The gaseous atmosphere, liquid ocean and solid Earth all behave as fluids when it comes
to ‘layering’ (the development of thin layers with different densities). Explain how pressure
variations related to buoyancy make this happen.
13. Atmospheric carbon dioxide is increasing at the rate of 0.7 parts per million, per year.
Many people argue that photosynthesis will increase as a result; since the CO2 will ‘fertilize’
the biosphere. Describe how limiting nutrients may make this prediction wrong for oceanic
plankton.
===========================