1. The Earth has one big ocean with many features
a The ocean is the dominant physical feature on our planet Earth—covering approximately 70% of the planet’s surface. There is one ocean with many ocean basins, such as the North Pacific, South Pacific, North Atlantic, South Atlantic,Indian and Arctic.
b An ocean basin’s size, shape and features (islands, trenches, mid-ocean ridges, rift valleys) vary due to the movement of Earth’s lithospheric plates. Earth’s highest peaks, deepest valleys and flattest vast plains are all in the ocean.
c Throughout the ocean there is one interconnected circulation system powered by wind, tides, the force of the Earth’s rotation (Coriolis effect), the Sun, and water density differences. The shape of ocean basins and adjacent land masses influence the path of circulation.
d Sea level is the average height of the ocean relative to the land, taking into account the differences caused by tides. Sea level changes as plate tectonics cause the volume of ocean basins and the height of the land to change. It changes as ice caps on land melt or grow. It also changes as sea water expands and contracts when ocean water warms and cools.
e Most of Earth’s water (97%) is in the ocean. Seawater has unique properties: it is saline, its freezing point is slightly lower than fresh water, its density is slightly higher, its electrical conductivity is much higher, and it is slightly basic. The salt in seawater comes from eroding land, volcanic emissions, reactions at the seafloor, and atmospheric deposition.
f The ocean is an integral part of the water cycle and is connected to all of the earth’s water reservoirs via
evaporation and precipitation processes.
g The ocean is connected to major lakes, watersheds and waterways because all major watersheds on Earth drain to the ocean. Rivers and streams transport nutrients, salts,sediments and pollutants from watersheds to estuaries and to the ocean.
h Although the ocean is large, it is finite and resources are limited. The Earth has one big ocean with many features.
2.
a Many earth materials and geochemical cycles originate in
the ocean. Many of the sedimentary rocks now exposed
on land were formed in the ocean. Ocean life laid down
the vast volume of siliceous and carbonate rocks.
b Sea level changes over time have expanded and contracted
continental shelves, created and destroyed inland seas, and
shaped the surface of land.
c Erosion—the wearing away of rock, soil and other biotic
and abiotic earth materials—occurs in coastal areas as wind,
waves, and currents in rivers and the ocean move sediments.
d Sand consists of tiny bits of animals, plants, rocks and
minerals. Most beach sand is eroded from land sources and
carried to the coast by rivers, but sand is also eroded
from coastal sources by surf. Sand is redistributed by
waves and coastal currents seasonally.
e Tectonic activity, sea level changes, and force of waves
influence the physical structure and landforms of the coast.
3.
a The ocean controls weather and climate by dominating
the Earth’s energy, water and carbon systems.
b The ocean absorbs much of the solar radiation reaching
Earth. The ocean loses heat by evaporation. This heat loss
drives atmospheric circulation when, after it is released into
the atmosphere as water vapor, it condenses and forms rain.
Condensation of water evaporated from warm seas provides
the energy for hurricanes and cyclones.
c The El Niño Southern Oscillation causes important changes
in global weather patterns because it changes the way heat
is released to the atmosphere in the Pacific.
d Most rain that falls on land originally evaporated from
the tropical ocean.
e The ocean dominates the Earth’s carbon cycle. Half the
primary productivity on Earth takes place in the sunlit layers
of the ocean and the ocean absorbs roughly half
of all carbon dioxide added to the atmosphere.
f The ocean has had, and will continue to have, a significant
influence on climate change by absorbing, storing, and
moving heat, carbon and water.
g Changes in the ocean’s circulation have produced large,
abrupt changes in climate during the last 50,000 years.
4.
a Most of the oxygen in the atmosphere originally came from
the activities of photosynthetic organisms in the ocean.
b The first life is thought to have started in the ocean.
The earliest evidence of life is found in the ocean.
5.
a Ocean life ranges in size from the smallest virus to the
largest animal that has lived on Earth, the blue whale.
b Most life in the ocean exists as microbes. Microbes are the
most important primary producers in the ocean. Not only
are they the most abundant life form in the ocean, they
have extremely fast growth rates and life cycles.
c Some major groups are found exclusively in the ocean.
The diversity of major groups of organisms is much greater
in the ocean than on land.
d Ocean biology provides many unique examples of life cycles,
adaptations and important relationships among organisms
(symbiosis, predator-prey dynamics and energy transfer)
that do not occur on land.
e The ocean is three-dimensional, offering vast living space
and diverse habitats from the surface through the water
column to the seafloor. Most of the living space on Earth
is in the ocean.
f Ocean habitats are defined by environmental factors.
Due to interactions of abiotic factors such as salinity, temperature,
oxygen, pH, light, nutrients, pressure, substrate and
circulation, ocean life is not evenly distributed temporally
or spatially, i.e., it is “patchy”. Some regions of the ocean
support more diverse and abundant life than anywhere
on Earth, while much of the ocean is considered a desert.
g There are deep ocean ecosystems that are independent
of energy from sunlight and photosynthetic organisms.
Hydrothermal vents, submarine hot springs, methane cold
seeps, and whale falls rely only on chemical energy and
chemosynthetic organisms to support life.
h Tides, waves and predation cause vertical zonation
patterns along the shore, influencing the distribution
and diversity of organisms.
i Estuaries provide important and productive nursery
areas for many marine and aquatic species.
6.
a The ocean affects every human life. It supplies freshwater
(most rain comes from the ocean) and nearly all Earth’s
oxygen. It moderates the Earth’s climate, influences our
weather, and affects human health.
b From the ocean we get foods, medicines, and mineral and
energy resources. In addition, it provides jobs, supports our
nation’s economy, serves as a highway for transportation
of goods and people, and plays a role in national security.
c The ocean is a source of inspiration, recreation,
rejuvenation and discovery. It is also an important element
in the heritage of many cultures.
d Much of the world’s population lives in coastal areas.
e Humans affect the ocean in a variety of ways. Laws,
regulations and resource management affect what is taken
out and put into the ocean. Human development and
activity leads to pollution (point source, non-point source,
and noise pollution) and physical modifications (changes
to beaches, shores and rivers). In addition, humans have
removed most of the large vertebrates from the ocean.
f Coastal regions are susceptible to natural hazards (tsunamis,
hurricanes, cyclones, sea level change, and storm surges).
g Everyone is responsible for caring for the ocean. The ocean
sustains life on Earth and humans must live in ways that
sustain the ocean. Individual and collective actions are
needed to effectively manage ocean resources for all.
7.
a The ocean is the last and largest unexplored place on Earth—
less than 5% of it has been explored. This is the great frontier
for the next generation’s explorers and researchers, where
they will find great opportunities for inquiry and
investigation.
b Understanding the ocean is more than a matter of curiosity.
Exploration, inquiry and study are required to better
understand ocean systems and processes.
c Over the last 40 years, use of ocean resources has increased
significantly, therefore the future sustainability of ocean
resources depends on our understanding of those resources
and their potential and limitations.
d New technologies, sensors and tools are expanding our
ability to explore the ocean. Ocean scientists are relying
more and more on satellites, drifters, buoys, subsea
observatories and unmanned submersibles.
e Use of mathematical models is now an essential part of
ocean sciences. Models help us understand the complexity
of the ocean and of its interaction with Earth’s climate.
They process observations and help describe the interactions
among systems.
f Ocean exploration is truly interdisciplinary. It requires close
collaboration among biologists, chemists, climatologists,
computer programmers, engineers, geologists, meteorologists,
and physicists, and new ways of thinking.
