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.

upwelling
Upwelling usually results in rich fisheries.

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.

artificial upwelling
Noun

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

Noun

an invisible line around which an object spins.

Noun

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

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.

Noun

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

complex
Adjective

complicated.

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.

Noun

agricultural produce.

Noun

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

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.

Noun

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

east
Noun

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

Noun

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

Noun

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

Noun

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

fertile
Adjective

able to produce crops or sustain agriculture.

fishery
Noun

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

Noun

clouds at ground level.

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.

Noun

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

Noun

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

Plural Noun

(singular: plankton) microscopic aquatic organisms.

reduction
Noun

lowering.

Noun

object's complete turn around its own axis.

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.

Noun

process in which cold, nutrient-rich water from the bottom of an ocean basin or lake is brought to the surface due to atmospheric effects such as the Coriolis force or wind.

veer
Verb

to lean or change direction.

west
Noun

direction in which the sun appears to set.

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.