The Handy Ocean Answer Book (The Handy Answer Book Series)

545 Pages·1999·73.04 MB·English

by  Patricia Barnes-Svarney

I n t r o d u c t i o n
It
is difficult for those of us who live inland to understand the immensity and effects
of the world's oceans. These vast bodies of water take up 70 percent of the surface area
of globe, with a volume close to 350 million cubic miles. And at present, ours is
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the only known planet in the solar system to contain such waters.
Even those of us living in the middle of a continent are affected by these immense
bodies of water in a direct or indirect way. For example, the Sun heats the surface of
the oceans, evaporating waters to form clouds and mixing the air currents to produce
our weather systems. The Sun's heat also stirs the surface waters, creating waves and
currents that sculpt our shorelines. Seasonal temperature changes of the ocean waters
alternately increase or decrease populations of marine organisms, including many
that humans harvest for food.
Most importantly, without the oceans, there would be no life. It was in the oceans,
billions of years ago, that life began-probably in shallower waters or around deep
hydrothermal vents. Either way, life evolved under water, eventually reaching the edges
of the oceans and making its way to land. As amazing as it seems, our entire population
of terrestrial and marine organisms all had a common beginning-in our oceans.
To most of us, the ocean is beautiful, awesome, sometimes deadly-and at the
same time, misunderstood. The reason it is not well understood is, perhaps, obvious:
We cannot see below the surface of the ocean without diving in; and because of our
physical limitations, we can only dive so far and for so long. We can only touch and
examine the fringes of this huge body of water, and, so far, have made relatively few
forays into its depths. As many people have pointed out, what lies below the surface of
the Earth's oceans is almost an alien planet to us.
It is this alienness that The Handy Ocean Answer Book addresses, filling the gaps
in the reader's understanding of the most important part of our world. These pages
present answers to the most common questions about our oceans-eovering features
and organisms from the shoreline to the open ocean. Here, we examine the physical XI
attributes of the oceans, marine animals and plants, and finally, the human ties to
(and our effect on) the oceans.
Many people call the oceans our most important natural resource. The waters
have furnished humans with food for centuries-from a plethora of fish species to cer
tain marine plants. But people have also adversely affected the oceans: Over-fishing,
coastal erosion caused by development, and pollution threaten this natural habitat.
We need to keep the oceans in balance in the future-especially since we will continue
to need the oceans and their bounty if we are to survive as a species.
The world ocean continues to hold many secrets; there are numerous questions
still to be answered. For example, what kinds of organisms are found in the ocean's
deepest waters? How many fish thought to be extinct are actually still alive? What
species are important to coral reef growth? How do microorganisms live in the coldest
waters of the Arctic? Other questions have to do with the connections-and interde+
pendencies-between humans and the ocean. For example, are plankton (one of the
most important organisms in the marine food chain) able to withstand environmental
stresses such as the ozone hole? Can humans continue to harvest the oceans without
disrupting the balance between the organisms and their environment? Scientists hope
to answer some of these questions in the near future, not only by using better technol
ogy that allows humans to dive into and explore the oceans for longer periods, but
through new satellites that watch the global waters-tracking changes over time.
We hope these pages describe an underwater world that will inform and inspire
you, and, perhaps, engage your interest enough that you'll want to discover even more
about the wonders of the ocean. This is the mysterious and largely unexplored territo
ry where life originated-and it will be an integral part of our future.
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A c k n o w l e d g m e n t s
As with every book, there are many people who contributed stories and informa
tion-a list, in this case, that seems to go on forever. In particular, thanks go out
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to the many oceanographers and scientists who have charted the oceans, dived into
the depths, and studied marine life for the past decades. Without their hard work and
dedication, this book could not have been written.
We would also like to thank the following groups and people: Woods Hole Oceano
graphic Institution, Scripps Institution of Oceanography, Mystic Aquarium, the
National Aquarium (Baltimore), the Smithsonian Institution, many of the National
Marine Sanctuaries, Lamont-Doherty Geological Observatory, Shoals Marine Lab, the
Naval Research Laboratory, U.S. Naval Academy, Virginia Institute of Marine Science,
University of South Florida at St. Petersburg, the Monterey Bay Aquarium, the Nation
al Oceanic and Atmospheric Administration (including the U.S. National Oceano
graphic Data Center), the National Aeronautics and Space Administration, Eugenie
Clark, Ann McGovern, and Kristen Kusek.
Our gratitude to the people at Visible Ink Press and the Gale Group who assisted
us in many ways: Pamela Galbreath for her book design work and Cindy Baldwin for
her artistic guidance; Matt Nowinski and Justin Karr for helping us locate images;
Edna Hedblad for securing permissions; Pam Reed, Randy Bassett, and Robert Duncan
for preparing the images-and Mary Grimes and Leatha Etheridge-Sims for cata
loging them; Marco Oi Vita of the Graphix Group for typesetting; and David Deis at
Oreamline Cartography for the color map of the world appearing in the insert. And a
very special thanks to our ever-patient editors Jeff Hermann and Rebecca Ferguson for
all their help and great work on this book; and also to Julia Furtaw, Marty Connors,
and Christa Brelin, who believed in us and let us "play in the ocean." We could not
have written this book without their help.
Xlii
O C E A N BASICS
What is the world ocean?
The world ocean is the large, interconnected body of saltwater that cov
ers just over 70 percent of our planet. This vast world ocean is com
posed of five large, localized oceans (the Pacific, Atlantic, Indian,
Antarctic, and Arctic oceans), and numerous seas. The more familiar,
individual oceans are bodies of water that have well-defined basins, bot
tom topography (landscape of the seafloor), wind patterns above the
ocean surface, and vertical and horizontal water movement in the form
of currents and waves. The definitions and boundaries of the global
oceans are determined by the International Hydrographic Bureau,
located in Monaco.
The depressions on the ocean floor holding most of the planet's water
are called ocean basins. Landscapes of these depressions are unique and
changing-and are an often-neglected, integral part of the ocean.
Where did the word "ocean" originate?
The word ocean is from the Greek word okeanos, meaning "river." The
early Greeks believed the ocean to be a great river flowing around the
Earth. They also believed the Mediterranean, their local body of water,
was a sea within the river.
3
What is the total volume of the world ocean?
Since much of the world ocean has not been mapped yet, the total vol
ume of the oceans and seas cannot be absolutely determined. However,
scientists estimate the total volume of the world's oceans and seas is
about 350 million cubic miles (1.5 x 109 cubic kilometers)-making our
globe a definite water planet. The Earth has more ocean volume than
any other planet in the solar system. Jupiter's moons Europa and Callis
to may harbor oceans under their icy surfaces-a highly debated theory
currently under study-but these oceans would be much smaller than
the Earth's.
Why are oceans important to the global environment?
The oceans are the cradles and nurturers of life on this planet-without
them, you would not be here. The oceans are the main drivers of the
Earth's water cycle, supplying most of the moisture that influences the
global climate. Without moisture from the oceans, the planet would be
parched, similar to oceanless Mars; or it would be a staggeringly hot and
carbon dioxide-fi1led environment similar to Venus.
The differential heating of the oceans by the Sun's rays produces tem
perature and pressure changes in the atmosphere, which in turn gener
ate the winds and create our weather. The long-term distribution of this
energy by the oceans creates the localized climates that support the var
ied life forms found in our world.
In addition, the ocean currents transport heat, oxygen, nutrients, plants,
and animals around the globe, and the ocean itself provides us with food
and other necessities. The oceans sustain a large and complex food
chain-a major part of the planet's overall food web.
Why does the Earth look blue from space?
The Earth looks blue from space because of its oceans. Using a prism,
light can be broken up into an array of colors-red, orange, yellow,
green, blue, and violet-called a spectrum. The ocean waters act as a
prism, but as light travels into the water, the red, orange, and yellow col
4 ors are absorbed more quickly than the blue light. Blue light can pene-
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viewed ~gainst the backdrop ofTurkey's white be~ches. (for color irTlilge, 5ee insert.) CORB/5/Chri5 Hellier
trate below about 100 feet (30 meters) in depth-which is why the clear,
mid-ocean water looks so blue on a sunny day. In many coastal and polar
water areas-in which animals and plant life are plentiful and sediment
arrives from rivers-the blue light is more readily absorbed, causing the
water to look more greenish in color.
Can an ocean be a color other than blue?
Yes, and many times, depending on the circumstances, an ocean seems
to change color. For example, during hurricanes in the Atlantic Ocean,
the water often looks green, as it mixes with the yel10w pigments of
floating plants (the colors yellow and blue mixed together equal green).
Other times, parts of the Atlantic surf will look almost a milky brown, as
a storm churns up sand and sediment is swept out of rivers by fast-mov
ing currents. Other oceans and seas also seem to vary in color, including
the Red Sea in the Middle East, in which seasonal growth of red algae
turns the waters red; the Black Sea (north of Turkey), which contains so
much hydrogen sulfide that the water truly looks black; and the Yellow 5
Sea (off the coast of China), which
looks yellow because of the nearby
mud and sediment-filled rivers that
empty into it.
What percentage of the Earth's
surface is oceans and what
percentage is land?
An estimated 70.78 percent of the
Earth's surface is covered by oceans,
or 139.4 million square miles (360.9
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square kilometers). The amount in
each hemisphere also differs: In the
Southern Hemisphere, the proportion of water to land is approximately
4:1; in the Northern Hemisphere, it is approximately 3:2. Put another
way, about 81 percent of the surface of the Southern Hemisphere is cov
ered by oceans; while only about 61 percent of the Northern Hemi
sphere is covered by oceans.
What percentage of the world's water is held in the oceans?
The oceans contain about 97 percent of the tolal water on Earth. In con
trast, the ice caps and glaciers hold about 2 percent, and less than 0.3
percent is carried in the atmosphere in the form of clouds, rain, and
snow. Our inland seas, lakes, and channels account for a mere 0.02 per
cent of the Earth's water.
What is the total weight of all the water in the oceans?
The approximate total weight of all the water in the Earth's oceans is
1.45 x 1018 tons. This represents about 0.022 percent of the total weight
6 of the planet.
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What is the average depth of the world ocean?
The average worldwide ocean depth is about 12,460 feet (3,798 meters)
below sea level, or about five times the average elevation on land. The
average land height is about 2,757 feet (840 meters) above sea level.
What are the average depths of the major individual oceans?
The average depths of the major oceans vary greatly. The Pacific Ocean
has an average depth of 13,740 feet (4,188 meters), the Indian Ocean
averages 12,704 feet (3,872 meters), and the Atlantic Ocean has an aver
age depth of 12,254 feet (3,735 meters). The average depth of the Arctic
Ocean is only 3,407 reet (1,038 meters).
Which ocean is the deepest?
The Pacific Ocean is the deepest, with an average depth of 13,740 feet
(4,188 meters). It also contains most of the ocean trenches, which are 7
the deepest places known on the Earth's surface. The greatest depth in
this body of water is 36,198 feet (11,033 meters).
What is the shallowest ocean?
The Arctic Ocean-the sea and ice north of the Arctic Circle with the
North Pole at its center-is the shallowest, with an average depth of
3,407 feet (1,038 meters). The greatest depth in this body of water is
17,848 feet (5,440 meters).
What is the deepest point on the ocean floor?
The deepest known part of the ocean is a place called the Challenger
Deep, located at the bottom of the Mariana Trench in the Pacific Ocean.
It measures 36,198 feet (11,033 meters) below sea level. If Mount Ever
est-the tallest mountain on the Earth's surface, measuring 29,022 feet,
7 inches (8,846 meters) in height-were dropped into this trench, it
would be covered with more than a mile (or more than one and a half
kilometers) of seawater.
SEAWATER
What is seawater?
Water found in an ocean or sea is called seawater (or sea water). It is
composed of water-a molecule formed by the combination of one oxy
gen atom with two hydrogen atoms-and ions (electrically charged
atoms) of salt and other dissolved materials (trace elements).
Does the composition of seawater vary?
Yes and no: While there are local differences in temperature and salinity
8 (saltiness), and some differences in concentrations of certain substances
What is the composition of seawater?
French scientist Antoine-Laurent Lavoisier (1743-94) deter
mined that in addition to water (H 0), seawater is made up of
2
ions (electrically charged atoms) of sodium, calcium, and magne~
sium chlorides; sodium, magnesium, and calcium sulfates; and
calcium carbonate. These ions account for more than 99.95 per
cent of the total weight of all ions present in seawater; the fest
are found in trace amounts (trace amounts are measured in parts
per million, abbreviated ppm). These trace materials include
almost all of the elements.
from ocean to ocean, in general the composition, or content, of seawater is
fairly uniform throughout the oceans of the world. This fact was first con
firmed by William Dittmar, an English chemist who sailed on the H.M.S.
Challenger during its round-the-world expedition from 1872 to 1876.
In addition, studies of marine deposits from all geological time periods
show that the composition of seawater has remained fairly consistent
over the long history of our planet. This would make sense, since the
early ocean currents flowed unimpeded by continental barriers-thus
the seawater easily mixed throughout the global oceans.
What are some of the unique properties of water?
Water is the only known substance on Earth present in nature as a liq
uid, gas, and solid. In its liquid state, water is the foremost dissolver of
material, out-distancing the ability of any other liquid; water vapor
"humidifies" the atmosphere, and helps create the weather we experi
ence on the surface of Earth-part of the planet's complex water cycle.
And finally, the properties of water as a solid (or frozen) are critical to
life in the oceans: Ice is less dense than its liquid form, so it floats
(which, by the way, is a property shared only by three known elements).
Because of this, a body of water in the colder regions has a cap of ice,
with life-sustaining liquid below it. If ice were not less dense than water, 9