OCEANOGRAPHY & MARINE SCIENCE

An extensive series utilizing many multiple
images to present a comprehensive and
integrated approach to the total spectrum
of marine biology and oceanography. Solid
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WORLD OCEAN: THE EARTH'S WATERS
How the oceans aquire, store and circ- ulate heat, the many movements seawater undergoes and how sea-level varies over time. 5 pgms. 70 slides and guides.
EPSS-0730X SLIDES
$149.95

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SAVE OVER $55.00 ON 5 SLIDE SET BUNDLE ORDER EP #SS-0730X....$149.95
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HEAT BUDGET OF THE WORLD OCEAN Slides order #SS-0730S......$42.50

The oceans' surface temperature has changed very little during the past one or
two billion years. This program discusses the concept of a global balance of heat
entering vs. heat lost from the ocean. Examines the role of unequal distribution of heat
inflow and outflow in circulating surface and sub-surface currents. 15 frames, cassette
and guide. (Filmstrip order SS-0730F.....$15.00.)

CONTENT SAMPLE: 2. Virtually one hundred percent of heat flow into the oceans is
from solar radiation. Other sources of heat gain are negligible: heat inflow from the earth’s interior,
heat generated by waves in surf, and heat from chemical and nuclear reactions.

Heat flow in ocean waters is generally measured in langleys per unit time; one langley
(ly) equals one gram calorie per square centimeter.

The average amount of solar radiation that is received at the earth’s surface (i.e.,
insolation) is 0.25 ly per minute on a 24 hr basis. During daylight hours both the land and ocean
are heated as the energy in solar radiation is absorbed.

The ocean is a more efficient collector of solar energy then the land due to the high
heat capacity of water and vertical mixing of surface ocean waters. Water has an extremely high
heat capacity, with the result that ocean waters can absorb and release large amounts of heat
with little resulting change in temperature. But water temperatures would increase by about 3.5
degrees C in one day if the absorbed sunlight heated only the upper water of the ocean surface.
Vertical mixing of near-surface waters distributes the daily inflow of solar energy to depths of ten
meters or more. As a result the heat absorbed by ocean waters during the day is not as readily
lost to the atmosphere as on land, where only the surface of rocks and soil are heated. The
mean daily temperature variation of the land is consequently much greater than that of the open
ocean, which varies by only 0.2--0.3 degrees C over a 24 hr period.
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CIRCULATION OF THE WORLD OCEAN Slides order #SS-0735S.......$34.95

This program examines the slow temperature and/or saline stimulated mixing of
deep ocean water masses, in contrast to the continuous driving force of surface winds.
The interaction of thermohaline and surface circulations, and the process of heat transfer
from low latitudes for an overall world ocean heat balance is detailed. 10 frames,
cassette and guide. (Filmstrip order SS-0735F......$15.00.)

CONTENT SAMPLE: 3. The unequal heating of the ocean surface also causes vertical
circulation cells within the ocean. The origin and form of these cells differs from those of the
atmosphere.

The atmosphere is heated from the bottom primarily by back radiation from the ocean and
land and from condensation of water vapor. Warm air rises and is replaced by cooler air, thereby
forming convection cells that enhance circulation.

The ocean, on the other hand, is heated at the surface. Warm water is less dense than
cool water and convection cells are inhibited as the warmer water sits on the surface. Warm water
is less dense because it expands; its mass per unit volume decreases. The sea level at the
equator is consequently several inches higher than at the poles. Surface water flows down this
tiny slope from the equator towards the poles. Meanwhile the denser water at the poles sinks
below the surface and tends to spread along the bottom toward the equator.

Such subsurface movement of water masses is termed "thermohaline," because the
driving force is a change in density due to a change in temperature and/or salinity. Wind-driven
surface currents form the surface component of these simplified circulation cells.
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SEA-LEVEL CHANGES Slides order #SS-0765S .........$34.95

Provides a basic understanding of the meaning of "sea-level" and how it is
determined. Examines variations in sea-level over the past 100,000 years, and factors
influencing those variations. Concludes with a thought-provoking discussion of the
impact of future sea-level changes. 10 frames, cassette and guide. (Filmstrip order
SS-0765F......$15.00.)

CONTENT SAMPLE: 7. Locating and dating ancient shorelines allows us to recon-
struct the history of sea level fluctuations during glacial periods. The graph presented in this slide
shows how global mean sea level has changed during the past one hundred thousand years. This
interval corresponds to the last glacial period, from the Sangamon Interglacial Age through the late
Wisconsin Ice Age to the present interglacial age of Holocene times. Sea level is represented
here in meters below the present level after isostatic adjustments have been taken into account.
At the height of the Late Wisconsin Ice Age sea level dropped about 100 m relative to its present
level, as about 150 m of seawater were removed from the world ocean and stored in conti-
nental glaciers. Sea level rose to its present level when the continental glaciers melted. Between
17,000 and 6,000 years ago the rise in sea level was relatively rapid, with an average rise of about
1 cm per year. Since about 6,000 years ago (4,000 B.C.) sea level has remained essentially
stable. Over the first half of the present century measurements indicate that global mean sea
level is rising at an average rate of only 1.2 mm per year.
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THE TIDES Slides order #SS-0515S..........$49.95

An inspection of lunar/solar influences on the oceans and the biological results
of these forces. 20 frames, cassette and guide. (Filmstrip order SS-0515F.......$15.00.)

CONTENT SAMPLE: 16. Astronomical tidal effects are greatly modified by the
contour, depth, and size of ocean basins. In the open oceans, large standing waves (like the
waves in a plucked guitar string, above) oscillate and have nodes where tidal variation is minimal.
One side of a node will have a high tide while the other has a low tide (below). If the standing
waves of a particular node are generated by lunar gravitation, the node may experience solar
tides alone; for example, high tides occur in the Society Islands at noon and at midnight.
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WAVES AND TIDES Slides order #SS-0740S ......$42.50

Beginning with a consideration of the parts of the wave, this program covers all
the resonant interactions affecting tidal times and ranges. The cyclical influences of the
sun and the moon, and the local influences of barometric pressure and onshore winds
are also discussed. 15 frames, cassette and guide. (Filmstrip order SS-0740F...$15.00.)

CONTENT SAMPLE: 2. The propagation of waves through deep water is associated
with very little net water movement; only the wave form is moving. Consider a block of wood
floating on the surface of deep water. The block moves forward along the slope of each wave crest
and backward down the slope of each wave trough. With the passage of each wave the block
describes a complete circle, returning to its initial position after each successive crest and trough.
(Actually there is a slight net movement in the direction of wave travel, since the block moves
faster in the crest than in the trough, but this net movement is negligible when compared to wave
speed.)

As can be seen in this illustration, the diameter of the orbital paths traced by a floating
block or surface particle is equal to the wave height (H), the vertical distance between a crest
and a trough. Below the surface both the diameter and speed of the orbits decrease progressively
with depth until at a depth of about half a wavelength (L/2) orbital motions disappear altogether.
Thus in water deeper than half a wavelength the passage of wave forms is not accompanied by
significant horizontal water movements. In addition, wave speed and wavelength are not affected
by the ocean bottom in water deeper than half a wavelength.
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wav&td11 Tides at the Bay of Fundy. graphic by Educational Images Ltd.

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