Chapter 2 - Moving Ocean Waters

Notes for Chapter 2:
Moving Ocean Waters and Their Relationship to Life

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Case History: UFOs

Featured Organism p. 9, 22: Maldive coconut (coco de mer)
Featured Organism p. 22, 28: ocean sunfish or links 1 - 2 - 3 - 4

I. Ocean Gyres and Currents
        terms: gyres
    a) Surface Currents
        terms: Antarctic Circumpolar Current (West Wind Drift),
            East Wind Drift, Equatorial Countercurrent, North/South
            Equatorial Currents

RQ2.1: Describe the primary global currents, starting with the
most important ones

    b) The Winds That Drive the Currents
        terms: northeast/southeast trade winds (trades), westerlies,
            polar easterlies, meteorological equator, doldrums,
            horse latitudes, southwest/northeast monsoon

RQ2.2: If trade winds blow westward, why does the Equatorial
countercurrent travel eastward?

    c) The Effects of Surface Currents on Marine Communities
        terms: polar/cold-temperate/warm-temperate (subtropical)/tropical
        1) Currents compress or expand communities
            along continental shores

        Featured Organisms p. 26:
        Cancer amphioetus (warm-temperate crab,
                           nice images with Japanese text)
        Arctica islandica (cold-temperate clam,
                           better know as ocean quahog)

         RQ2.3: Why does the warm-temperate crab have a narrower
                latitudinal distribution (north to south) on our West
                Coast than it does in the vicinity of Japan?

2) Currents carry organisms to hostile environments
terms: rings, warm-core ring, cold-core ring, expatriate organisms

        Featured Organisms p. 28:
                California (or Pacific) baracuda or links 1 - 2
                blue shark or links 1 - 2
                albacore or links 1 - 2
                black durgon (triggerfish) or movie 1

         RQ2.4: If so-called "expatriate" organisms can occasionally be
                transported far north or south of their normal range, why
                do they tend to disappear after a few years?

II. The Movements of Deep Ocean Waters
    a) The Density of water
         terms: density (mass divided by volume)
        1) Water of low density floats; water of high density sinks
         terms: stratified vs. unstratified water

         RQ2.5: Why does the ocean become stratified and what
                time of year does it become this way. Why and when
                does it become unstratified?

        2) Cooling, freezing, and salt concentrations cause surface
            seawater to sink
         terms: turnover, profiles, thermocline

b) The Strata of Water in the Oceans
terms: surface layer, upper/intermediate/deep/bottom waters

       1) Surface waters form everywhere; Central and Equatorial
            waters form in the subtropics
         terms: Equatorial Water, Central Water, Subtropical Convergences

        2) Sinking water forms the deepest three layers
         terms: Antarctic Bottom Water (ABW), North Atlantic Deep Water
                (NADW), Antarctic Divergence, Antarctic Convergence, Antarctic
                Intermediate Water (AIW)

         RQ2.6: Imagine you are in a submarine in the middle of the
                Atlantic Ocean on the Equator. Describe the discrete layers
                of seawater of different densities and temperature that you
                expect to pass through on your way to the bottom. Where
                did each layer originate? (Challenge question: When was
                it last at the surface?)

       3) Sinking surface water carries oxygen to the deep sea
            bottom
         terms: thermohaline circulation

        RQ2.7: You finally made it to the bottom (see last question) and
                find some deep sea organisms living there that depend on
                oxygen for their normal respiration. What is the source of
                that oxygen?

        4) The Cariaco Basin has no deep flows and therefore
            no oxygen, no animals
         terms: anaerobic bacteria, toxic hydrogen sulfide, anoxic water

5) Some fishes avoid the East Pacific oxygen minimum
terms: oxygen minimum

c) Deep-Water Avenues to Other Oceans
terms: submergence

         RQ2.8: Why don't the Pacific and Indian Oceans have
                circulation patterns from the polar regions that
                were described for the Atlantic Ocean?

III. Upwelling
terms: upwelling

a) Coastal Upwelling
terms: Coriolis effect, downwelling

Having trouble visualizing it? Check out this animated Coriolis effect

The truth behind the Coriolis effect and whether it affects toilet bowls
and sinks: 1 - 2 - 3

RQ2.8: When does coastal upwelling affect the California coast
and what consequences does it have when it does?

         RQ2.9: Why do many coastal marine animals that have a
                planktonic larval stage seem to have especially good success
                at settling out of the plankton onto the shore during years
                when there is not much coastal upwelling?

b) Equatorial Upwelling and the Great Antarctic Divergence
terms: Antarctic Divergence

         RQ2.10: How is the upwelling that occurs around the Antarctic
                continent fundamentally different than coastal upwelling
                elsewhere in the world?

IV. Estuarine Circulation
terms: estuary, estuarine circulation, salt wedge, negative
estuary, positive estuary

V. Tides
        terms: tides
    a) The Effect of the Moon, the Sun, and the Shapes of Ocean Basins
        terms: tidal bulge, high tide, low tide, mixed tide (as in California),
                semidiurnal tide, diurnal tide (see Fig. 2.19), MLW, MLLW,
                zero tide level, spring vs. neap tides, MSL

Visit the source of this animated image here (link now dead) or
click here for a similar but more detailed animation

Tides stumped Galileo and others (but Pytheas correctly attributed them to the Moon).
Newton finally figured out why they occur (see here for a pdf of tide theory).

RQ2.11: Why are there two low tides most days in California?

RQ2.12: Why does the lowest of the two low tides each day
occur about 50 minutes later than the day before?

RQ2.13: Why are the low tides lower than average about every
two weeks (at the full and new moons)?

The Moon is mostly responsible for tides, but the shape of ocean
basins can make a very large difference.

Tides can be extreme in some areas, like the Bay of Fundy, while other
places like the Adriatic Sea have relatively little tidal fluctuations.

Unusually severe tides can sometimes wreak havoc if unchecked,
as those who lived in London and the surrounding North Sea in 1953 know.

b) Critical Tide Heights on Intertidal Shores
terms: critical tide levels, tidal zones

        RQ2.14: In Seattle (Fig. 2.19), animals living at +8 ft. tidal
                height will be uncovered by low tides twice each day,
                while animals lower on the shore at +4 ft. only get
                uncovered once each day. How come?

VI. Waves
terms: wave, wavelength, wave height, crest, trough, surge,
exposed vs. protected shore

RQ2.15: What makes a wave break as it approaches the shore?
Why are some areas more impacted by waves than others?

VII. How Organisms Use Currents and Tides
terms: life cycle closure

Featured Organism (p. 46, Fig. 2.25):
Velella velella (By-the-wind Sailor) or links 1 - 2 - 3

a) Adaptation to Tidal Rhythms
terms: endogenous rhythm

                Featured Organisms
                    p. 48: California grunion or links 1 - 2
                            Expected grunion runs March - August 2002
                    p. 49: fiddler crab or links 1 - 2 - 3 - 4

RQ2.16: What advantage does a California grunion have
if it is synchronous with the activities of other grunions?

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or Lecture Notes by Chapter
Back to Chapter 1 or ahead to Chapter 3