Encyclopedic Entry

Upwelling usually results in rich fisheries.

Photograph by Bates Littlehales

Artificial Upwelling
Scientists and businesses are working to create areas of "artificial upwelling" to pump cold water to the surface. Researchers hope artificial upwelling will increase fish crops from the Gulf of Mexico to southwest Australia.

Artificial upwelling involves complex technology using the motion of waves to bring cold, nutrient-rich water from the deep ocean to the surface. Experiments in artificial upwelling have been tried in the Pacific Ocean near the Hawaiian Islands.

Upwelling is a process in which currents bring deep, cold water to the surface of the ocean. Upwelling is a result of winds and the rotation of the Earth.

The Earth rotates on its axis from west to east. Because of this rotation, winds tend to veer right in the northern hemisphere and left in the southern hemisphere. This is known as the Coriolis effect and is largely responsible for upwelling in coastal regions.

The Coriolis effect also causes upwelling in the open ocean near the Equator. Trade winds at the Equator blow surface water both north and south, allowing upwelling of deeper water.

The wind patterns generated during slow-moving cyclones can also blow surface water aside, causing upwelling directly beneath the eye of the cyclone. The colder water eventually helps to weaken the cyclone.

Effects of Upwelling
Biodiversity and productivity
Because the deep water brought to the surface is often rich in nutrients, coastal upwelling supports the growth of seaweed and plankton. These, in turn, provide food for fish, marine mammals, and birds.

Upwelling generates some of the world’s most fertile ecosystems. A 25,900-square-kilometer (10,000-square-mile) region off the west coast of Peru, for example, undergoes continual coastal upwelling and is among the richest fishing grounds in the world. Overall, coastal upwelling regions only cover 1 percent of the total area of the world’s oceans, but they provide about 50 percent of the fish harvest brought back to shore by the world’s fisheries.

During El Niño, a weather phenomenon that typically occurs every three to seven years, the Pacific Ocean’s climate changes dramatically. The transition zone between warm surface water and cold deep water deepens. Trade winds are also weak during El Niño. The combination of weak winds and deeper water limits upwelling. The reduction in nutrient-rich water leads to a lower fish population in the area, and therefore to a smaller fish crop.

Animal movement
Upwelling affects the movement of animal life in the area. Tiny larvae—the developing forms of many fish and invertebrates—can drift around in ocean currents for long periods of time. A strong upwelling event can wash the larvae far offshore, endangering their survival.

Coastal climate
The cold water welling up to the surface cools the air in the region. This promotes the development of sea fog. The city of San Francisco, California, is famous for its chilly, foggy summers, brought on by seasonal upwelling in the area.

Downwelling

Downwelling is a kind of reverse upwelling. Instead of deeper water rising up, warm surface water sinks down. Upwelling and downwelling patterns often alternate seasonally. The West Coast of the United States, for example, experiences summer upwelling and winter downwelling, as the winds change directions with the seasons.

Vocabulary

Term Part of Speech Definition Encyclopedic Entry

artificial upwelling

Noun

process of bringing cold water from the deep ocean to the surface.

axis

Noun

an invisible line around which an object spins.

Encyclopedic Entry: axis

biodiversity

Noun

all the different kinds of living organisms within a given area.

Encyclopedic Entry: biodiversity

bird

Noun

egg-laying animal with feathers, wings, and a beak.

chilly

Adjective

slightly cold.

climate

Noun

all weather conditions for a given location over a period of time.

Encyclopedic Entry: climate

coast

Noun

edge of land along the sea or other large body of water.

Encyclopedic Entry: coast

complex

Adjective

complicated.

Coriolis effect

Noun

the result of Earth's rotation on weather patterns and ocean currents. The Coriolis effect makes storms swirl clockwise in the Southern hemisphere and counterclockwise in the Northern Hemisphere.

Encyclopedic Entry: Coriolis effect

crop

Noun

agricultural produce.

Encyclopedic Entry: crop

current

Noun

steady, predictable flow of fluid within a larger body of that fluid.

Encyclopedic Entry: current

cyclone

Noun

weather system that rotates around a center of low pressure and includes thunderstorms and rain. Usually, hurricanes refer to cyclones that form over the Atlantic Ocean.

downwelling

Noun

movement of seawater from the surface to the deep.

Earth

Noun

our planet, the third from the Sun. The Earth is the only place in the known universe that supports life.

Encyclopedic Entry: Earth

east

Noun

direction in which the sun appears to rise, to the right of north.

ecosystem

Noun

community and interactions of living and nonliving things in an area.

Encyclopedic Entry: ecosystem

El Nino

Noun

irregular, recurring weather system that features a warm, eastern-flowing ocean current in the eastern Pacific Ocean.

Encyclopedic Entry: El Niño

Equator

Noun

imaginary line around the Earth, another planet, or star running east-west, 0 degrees latitude.

Encyclopedic Entry: equator

fertile

Adjective

able to produce crops or sustain agriculture.

fishery

Noun

industry or occupation of harvesting fish, either in the wild or through aquaculture.

fog

Noun

clouds at ground level.

Encyclopedic Entry: fog

invertebrate

Noun

animal without a spine.

larva

Noun

a new or immature insect or other type of invertebrate.

marine mammal

Noun

an animal that lives most of its life in the ocean but breathes air and gives birth to live young, such as whales and seals.

Northern Hemisphere

Noun

half of the Earth between the North Pole and the Equator.

nutrient

Noun

substance an organism needs for energy, growth, and life.

Encyclopedic Entry: nutrient

ocean

Noun

large body of salt water that covers most of the Earth.

Encyclopedic Entry: ocean

plankton

Plural Noun

(singular: plankton) microscopic aquatic organisms.

reduction

Noun

lowering.

rotation

Noun

object's complete turn around its own axis.

Encyclopedic Entry: rotation

seaweed

Noun

marine algae. Seaweed can be composed of brown, green, or red algae, as well as "blue-green algae," which is actually bacteria.

Southern Hemisphere

Noun

half of the Earth between the South Pole and the Equator.

technology

Noun

the science of using tools and complex machines to make human life easier or more profitable.

trade wind

Noun

winds that blow toward the Equator, from northeast to southwest in the Northern Hemisphere and from southeast to northwest in the Southern Hemisphere.

transition zone

Noun

area between two natural or artificial regions.

upwelling

Noun

process by which currents bring cold, nutrient-rich water to the ocean surface.

Encyclopedic Entry: upwelling

veer

Verb

to lean or change direction.

west

Noun

direction in which the sun appears to set.

wind

Noun

movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun.

Credits

Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Writers

Kim Rutledge
Melissa McDaniel
Diane Boudreau
Tara Ramroop
Santani Teng
Erin Sprout
Hilary Costa
Hilary Hall
Jeff Hunt

Illustrators

Tim Gunther
Mary Crooks, National Geographic Society

Editors

Kara West
Jeannie Evers

Educator Reviewer

Nancy Wynne

Producer

Caryl-Sue, National Geographic Society

Sources

Dunn, Margery G. (Editor). (1989, 1993). "Exploring Your World: The Adventure of Geography." Washington, D.C.: National Geographic Society.

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