Oceanography Ch.7

Equatorial counter currents

A large amount of water is driven westward due to the north and south equatorial currents. Due to the coriolis effect, it piles up on the western margins, making it up to 2 meters higher up than the water on the eastern side. Then, under the force of gravity, it flows eastward and counter to the adjoining continental currents. A large counter current exists in the Pacific Ocean, due to the large equatorial space in the Pacific Ocean, as well as the fact that continual influx of water creates a dome trapped between Australia and Asia. There is not so much of a equatorial counter current in the Atlantic, due to the bounding nature of the continents. In the Indian ocean, the existence of an equatorial current is strongly influenced by monsoons.

Surface currents

Air masses, mostly the major air masses, move currents at the surface. Powered by the Sun.

Conveyor belt circulation

An integrated model showing deep thermohaline circulation and surface currents. Starting in the North Atlantic, surface water carries heat to high latitudes via the Gulf Stream. During the winter, this heat is transferred to the atmosphere, warming Northern Europe. Cooling in the North Atlantic increases the density of surface water, and it sinks, creating a conveyor belt of sorts, and flows at a rate of 100 Amazons, flowing into the ocean basins of the world. This limb extends all the way to Africa, where it joins the deep water near Antarctica, which includes the deep water that encircles the margins of the Antarctic continent. This mixture of deep water flows north ward into the deep Pacific and Indian Ocean basins, where it completes the conveyor belt by flowing north and west again into the North Atlantic Ocean.

ENSO Index

Calculates the alternating patterns of El Nino and La Nina conditions since 1950. Calculated using a weighted average of atmoshpheric and oceanic factors. Positive numbers indicate El Nino conditions, while negative numbers indicate La Nina conditions. The greater the index number differs from zero, the stronger the respective condition.

Dissolved Oxygen in Deep Water

Cold water dissolves more oxygen than warm water, and circulation brings this cold, oxygen rich water to the deep ocean. When it returns, the oxygen rich water is also nutrient rich, due to the decomposition of dead organisms. Oxygen content of the oceans has circulated widely throughout time, and in the geologic past, deep water was warmer, leading to less oxygen in the water. Without this give and take, there would be significantly less organisms on the surface due to the lack of nutrients, and there would be virtually none on the ocean bottom due to the lack of oxygen.

East Australian Current

Cold, Eastern boundary current for the Indian Ocean Subtropical Gyre. Receives westward flow from the South Pacific Subtropical Gyre.

Eastern boundary currents

Come from higher latitude regions where water is cool, so they carry cool water to lower latitudes. When currents flow back across an ocean basin, continental barriers and the Coriolis effect turn them eastward and they become _____.

Ocean currents and climates

Continental margins that have cool ocean currents offshore typcally have a dry climate. Continental margins that have warm ocean currents offshore typically have humid climates.

Somali Current

Deals with monsoons. Extension of the North Equatorial Current that flows off of the African coast. During the winter, the North Equatorial Current flows from east to west. During summer, switches direction.

Thermohaline Circulation

Deep water circulation is caused by density variation, and in turn those are caused by differences in salinity and temperature. Deep water currents are very slow, and affect about 90% of water.

Antarctic Convergence Water

Deep water formed at the Arctic Convergence. Remains one of the world's most poorly studied deep water masses.

Ekman spiral

Developed by a Swede who said that ice moving left and right in ocean was a result of the balance between the friction in the water and the Coriolis effect. Assumes that wind sets in motion water. This water spins and creates a column of water, also spinning, beneath it. Due to the Coriolis effect in the Northern Hemisphere, the water spins progressively to the right, and because the energy is smaller with each and every other column of water underneath, it eventually slows down and dies, usually at a depth of 100 meters.

Leeuwin Current

Displaces the West Australian Current offshore. Is driven southward along the Australian current. Different from other eastern boundary currents because it produces a mild climate.

Antartic Divergence

Divergent current between East Wind Drift and West Wind Drift. Abundant marine life during Southern Hemisphere summer.

Antartic Circumpolar Current/ West Wind Drift

Driven by westerly wind belt. At 40 latitude, Southern Convergence, which forms northernmost boundary. Very strong winds. Only current which circumscribes Earth, due to lack of land at high latitudes. Continually pushed away from continent because of Coriolis Effect.

Monsoon winds

During the winter, air cools rapidly, creating high atmospheric pressure, and as it moves outward, it causes the wind to blow over the ocean. This is called the northeast monsoon, and during the winter there is little precipation. During the summer, the air heats rapidly because of the lower heat capacity of rocks and soil, creating low atmospheric pressure over the continent, and as a result, the wind blows strongly from the Indian Ocean into the continent, creating heavy precipitation. Affects surface circulation in the Ocean.

California Current

Eastern Boundary Current for the North Pacific Current. Cold current.

West Australian Current

Eastern boundary current for the Indian Ocean subtropical gyre. That merges with the South Equatorial Current.

Peru Current

Eastern boundary current for the South Pacific Current. Completes the South Pacific Subtropical Gyre. Continual upwelling of nutrient rich water produces great productivity, making the current one of the Earth's richest fishing grounds.

Benguela Current

Eastern boundary current in South Atlantic Gyre. Slow moving and cold, flows toward equator near Africa. Completes South Atlantic Gyre.

Canary Current

Eastern boundary for the North Atlantic Gyre. North Atlantic Drift turns southward to become this current.

Equatorial upwelling

Ekman transport causes water north of the equator to move rightward, and water south of the equator to move leftward, creating upswelling, usually in the Pacific Ocean. Creates areas of high productivity.

Subtropical convergence

Ekman transport moves water to the right in the Northern Hemisphere, and because of this, there is a great bulge in the middle of the ocean basin that can be as high as 2 meters.

Atlantic Equatorial Countercurrent

Equatorial counter current between North Atlantic Subtropical Gyre and South Atlantic Subtropical Gyre.

Gulf Stream

Equatorial current. Flows northward along East Coast.

Indirect current measures

First method: Current flows parallel to pressure gradient. Measure internal density of pressure gradient, and current should be the same. Second method: radar altimeter determines the shape and surface of the ocean by measuring the lumps and bulges on the ocean floor. Creates dynamic topography maps. Third method: Uses Doppler flow meter to measure the change in frequency between the waves emitted and those bounced back by the water particles.

Direct current measures

First method: Sticking measuring device into the ocean. Second method: Measuring current while on a pier, or on a boat.

Antilles Current

Flows across the West Indies.

Irminger Current

Flows along Iceland's west coast, and is broken off from the Labrador Current

Worldwide Deep water Circulation

For every liter of water that upwells, one liter of water must downswell. It was generally thought that this occurs gradually throughout the ocean, and of higher intensity in low latitude regions, where surface temperatures are higher. However, new research indicates that deep water traveling across rugged bottom topography is a major factor in producing upwelling and down swelling.

Sargasso Sea

Gulf Stream merges with it. The water that circulates around the rotation center of the North Atlantic Gyre. Stagnant eddy of North Atlantic Gyre. It's name is derived from a type of grape.

Walker Circulation Cell

High pressure and sinking air near South America and low pressure and rising air in the Pacific create the southeast trade winds. Named by an English scientist.

Temperature salinity Diagram

Identifies deep water masses based on their characteristic temperature, salinity, and density. Most deep water currents begin in high latitude as surface. As the water becomes cold, salinity increases as sea ice forms, and it sinks. Once it sinks, it is removed from the physical processes that created it, making it easy to identify. Because water in high latitudes has little to no temperature difference, there is no thermocline or pynocline, and upwelling and downwelling are accomplished easily.

Labrador Current

South of Newfoundland, the Gulf Stream breaks off into many currents. The cold water of this current combines with the warm water of the Gulf Stream to produce abundant fog in the North Atlantic.

North Atlantic Deep Water

In northern subpolar latitudes, large masses of water form in the Norweigan Sea, where they eventually sink, and are carried by a subsurface current into the North Atlantic. Less dense than Antarctic Bottom Water, so it layers on top of it, but does spread throughout ocean basins.

Antarctic Bottom Water

In southern subpolar latitudes, huge masses of ice form beneath sea ice, eventually sinking to the bottom, and eventually becoming the most dense water in the open ocean. It eventually spreads to all the world's ocean, eventually returning to the surface 1000 years later.

Tropical Ocean Global Atmosphere Program

Initiated after 1997-1998 El Nino event in order to try to predict the next Southern Oscillation. Measures the South Pacific Equatorial Currents.

North Pacific Subtropical Gyre

It's Eastern boundary current is called the Kuroshio Current, it's northern boundary is the North Pacific Current, and it's eastern boundary current is the cold California current, which flows southward.

Pacific Decadal Oscillation

Lasts 20 to 30 years and appears to influence Pacific sea surface temperatures. Analysis suggests that the Pacific Sea is in the cold phase, which may supress El Nino events during the next few decades.

Density currents

Low temperature, or substances dissolving in surface water causes it to sink to ocean floor, and move slowly throughout the bottom.

Warm core rings

Meanders, which are currents that pop off of Gulf Stream and are thought to cause the loss of water as the Gulf Stream goes northward, creates vortexes and eddies that trap warm water of the Sargasso Sea off of the northern boundary of the Gulf Stream. Contain shallow, bowl shaped masses of warm water. Remove large volumes of water as they disconnect from the Gulf Stream. Spin clockwise. Have safe havens for organisms that can only exist in cold or warm water, and can last up to two years.

East Wind Drift

Moves from East to West, forms divergent current with West Wind Drift. As it moves around Antartica, it is continually pushed towards the continent.

Norweigan current

Moves northward along Norway's coast.

Names of Subtropical Gyres

North Atlantic is named after Columbus, South Atlantic is named after Prince Henry the Navigator North Pacific is named the Turtle Gyre, after turtles who lay their eggs in Japan. South Pacific is named Heyerdahl, after Thor, who crossed the ocean in Kon Tiki. Indian Ocean is named the Majid Gyre, after the 15th century Arabian author and mariner, whose maps guided the Porteguese.

Subpolar Gyres

Northern or southern boundary currents that are driven eastward by prevailing easterlies and are eventually moved into sub polar latitudes (around the 60 latitude, north or south.) There, moved by polar easterlies, they are moved westward, and move in a direction opposite of adjacent sub tropical gyres.

North Pacific Current

Northernmost boundary for North Pacific Current, flows towards the East. Receives flow from the Kuroshio Current.

South Pacific Subtropical Gyre

Northernmost boundary is the South Equatorial Current. Western Boundary current is the Western Australian Current, which flows into the West Wind Drift, which is a cold current, and that flows into the Peru Current, which is a cold eastern boundary current. Also known as the Heyerdahl Gyre, includes the South Equatorial Current.

Indian Ocean Subtropical Gyre

Northernmost boundary is the southern equatorial current, it's eastern boundary is the Eastern Australian Current, and its western boundary is the Agulhas Current.

South Equatorial Current

Northernmost boundary of South Pacific Gyre. Reaches strength near Brazil and splits in two. Some splits off to North Atlantic and Caribbean Sea.

V. Walfrid Ekman

Observed that Fridtjof Nansen saw that Artic Ocean ice moved to the right 20 to 40 inches of the wind that blew across it, and developed the Ekman spiral. Ice in the Northern Hemisphere moved to the right, while the ice in the Southern Hemisphere moved to the left.

La Nina

Occurs immediately after an El Nino condition. Upwelling increases, pressure increases near Australia, and cold water extends leftward from South America.

Caribbean Current

Passes through Yucatan Channel into the Gulf of Mexico.

Argo

Program created in 2000 that sends advanced floats under the sea in order to determine the topography of the deep ocean, places unable to reached any other way. Go down for 10 days, surface and give information, do the same thing over and over again. Other methods for measuring deep water currents include using chemical tracers and identifying salinity and temperature characteristics of a deep water mass.

Alaskan Current

Receives flow from some of the North Pacific Current that flows northward, instead of southward.

Converging surface water

Results in downwelling, which creates areas of sparse productivity.

North Atlantic Subtropical Gyre

Rotates clockwise, due to trade winds, westerlies and Coriolis Effect. Contains both cold, equator moving return current and warm, poleward away currents.

South Atlantic Subtropical Gyre

Rotates counterclockwise, due to trade winds, westerlies and Coriolis Effect. Contains both cold, equator moving return curretn and warm, poleward away currents.

North Equatorial Current

Southernmost boundary of North Atlantic Gyre, and southernmost boundary for North Pacific Gyre. Moves parallel to the equator in the Northern Hemisphere, then joined by a portion of the South Equatorial Current as it flows southward across the South American Coast.

El Nino Southern Oscillation

Spanish for "the child." Periodically alternates between cold and warm phases and causes dramatic environmental changes. Accompanied by warmer water that extends from Australia towards South America. Trade winds weaken, even reverse direction, and upwelling halts.

Cold-core rings

Spin off to the south of the Gulf Stream as counter clockwise rotating rings. Can have depth that reaches ocean floor, which can have tremendous impact on ocean floor sediment. Can exceed over 500 diameters at the surface. Have safe havens for organisms that can only exist in cold or warm water, and can last up to two years.

Arctic Convergence

Surface waters converge within subtropical gyres and the Antarctic and Arctic, and do not sink because the surface water is too warm. This is not the case in this convergence.

Geostrophic current

Surface waters have a tendency to flow downhill due to gravity, but because of the Coriolis effect, it curves to the right, and the water goes back into the hill again. Ideal geostrophic flow involves the water going around the hill again and again. In actual geostrophic flow, friction between water molecules causes the water to gradually flow downward.

Western intensification

The hill in the ocean basin is closer to the western boundary of the ocean basin, rather than the middle. This causes the western water to be faster, narrower, and deeper. ALL WESTERN BOUNDARIES OF SUBTROPICAL GYRES ARE WESTERN BOUNDARY ORIENTED NO MATTER IF THEY ARE IN THE NORTHERN OR SOUTHERN HEMISPHERE. Because the Coriolis efect increases towards the poles, eastward flowing high latitude water turns toward the equator more strongly than westward flowing water turns in higher latitudes, leaving a narrow band through which western water can flow, making it of higher velocity.

Subtropical gryes

The large, circular moving loops of water in the ocean basin. Five major ones: North and South Atlantic Subtropical Gyres North and South Pacific Subtropical Gyres, and Indian Ocean Subtropical Gyres. Drift clockwise in a Northern Hemisphere, counterclockwise in a Southern Hemisphere. Average drift time in a smaller gyre, such as the North Atlantic Gyre, is three years, while the drift time in a larger one, such as the North Pacific Gyre, is six years. Each gyre is composed of four main currents.

North Atlantic Current

The sluggish, second main branch of the Gulf Stream.

Northern and Southern boundary currents

The westerlies, composed between 30 and 60 degrees latitude, blow these currents eastward across the ocean basin. When they are north of the equator, they are called____ and when they are south, they are called ______.

Equatorial currents

Trade winds set in motion by the currents in the tropics. These travel westward along the equator, and are named north or south ______ currents based on their position relative to the equator.

Pacific Warm Pool

Trade winds set water in motion, which warms as it crosses equatorial regions, and creates a wedge of warm water on the western side of the Pacific Ocean. Thicker on the western side due to the movement of equatorial currents.

Ekman transport

Under ideal conditions, the net water movement would move 45 degrees from the direction of the wind. However, all the layers combine to make the water transport 90 degrees right of the wind in the Northern Hemisphere and left in the Southern Hemisphere. In the real world, the water movement is less than 45 degrees, while the net water movement is around 70 degrees.

Tropical Atmosphere and Ocean Program

Used to measure the Pacific Ocean and try to predict El Nino events.

Upswelling

Vertical movement of cold deep water rich in nutrients and oxygen to the surface. Associated with high productivity. Can occur in high latitude areas, as the lack of a pynocline allows significant vertical mixing.

Downswelling

Vertical movement of surface water to deeper parts of the ocean. Brings neccessary dissolved oxygen to deepest parts of the ocean.

Florida Current

Warm current that merges into the Gulf Stream. As it moves off of North Carolina's Cape Hatteras in a northeasterly direction, it is called the Gulf Stream. The fastest current in the world ocean. It's eastern boundary is hard to identity because of all the meandering water masses. It's western boundary is very abrupt.

Coastal downswelling

Water coming in from the south causes water to move rightward and crash against the shore, causing downwelling. Same thing applies in Southern Hemisphere, except that it moves wind to the left.

Power from Currents

Water currents have about 800 times the density of air, many have proposed harnessing the energy inherent in them. One of the places this has been proposed is the Florida-Gulf Stream Current System, which is a western intensified surface current. One idea involves using a series of turbines, which can be set on the ocean bottom and turned to face incoming currents. This is problematic, because it poses a danger to shipping traffic, and water is a very effective corrosive. Still, turbines have been installed near Ireland, and are planned for use in South Korea.

Agulhas Current

Western Boundary Current for the Indian Ocean Subtropical Gyre. Flows southward along Africa's east coast.

Kuroshio Current

Western boundary current for the North Pacific Gyre. Receives flow from North Pacific Subtropical Gyre. Because the water is warm, it makes Japan's climate warmer than would be expected.

Brazil Current

Western boundary current. One of two split currents off of South Equatorial Current. Southward from Brazil. Weaker than Gulf Stream. Merges with Antarctic Circumpolar Current and moves eastward across the South Atlantic.

Oceanic Common Water

When North Atlantic Deep Water and Antarctic Bottom Water water mix and line the basin of the northern Indian Ocean.

Western boundary currents

When equatorial currents reach the western boundary of an ocean basin, they turn away, as they cannot cross land. The Coriolis effect turns these currents westward, where they become ______, and are so named because they travel on the westward boundary of the ocean basin. They also comprise the western boundary of the sub tropical gyre. Because they were formed in tropical places, they bring warm water upwards, to higher latitudes.

Antartic Convergence

Where cold Antartic water converges with warm Antartic water, in the West Wind Drift and East Wind Drift, and is submerged. Marks southernmost boundary of Antartic Ocean.

Coastal upwelling

Wind coming in from the north moves water to the right to due Ekman transport, and in coastal areas, causes waves to move away from the shore, causing upwelling to take their place. Same thing applies in Southern Hemisphere, except that it moves wind to the left.

Origin of surface currents

Without continents, would follow the trace of major air masses. Occur within and above the pynocline and affects about 10% of the world's water. It would flow, then, between 0 to 30 degrees under trade winds, 30 to 60 between the westerlies, and 60 to 90 between the polar winds. For example, prevailing trade winds and westerlies near the Atlantic Ocean create a swirl of air and ocean that is bounded by continents. This sort of thing occurs throughout the globe. Other factors that affect surface currents include gravity, the Coriolis effect, and friction.