Ocean Motion : Definition : Ocean in Motion - Geostrophic Flow
related topics. Ocean current · Equatorial countercurrent. Equatorial current, ocean current flowing westward near the equator, predominantly is propelled westward by the Southeast Trade Winds to about longitude ° E. There it splits, part. The trade winds are the prevailing pattern of surface winds from the east toward the west In the Pacific ocean, the full wind circulation, which included both the trade wind easterlies and higher-latitude Westerlies, was unknown to Europeans until 3D map showing Hadley cells in relationship to trade winds on the surface . There are a variety of factors that affect how ocean currents (water in motion) are created, including a are the Westerlies, which blow west to east, and the Trade Winds, which blow east to west. Related Sciencing Articles.
Seasonally, the ITCZ moves with the sun, shifting northward during the Northern Hemisphere spring and southward during the Northern Hemisphere autumn but generally remaining north of the equator, especially over the Atlantic Ocean.
Consequently, the eastward-flowing Equatorial Counter Current, separating the surface current systems of the two hemispheres, also lies mostly just north of the equator. The South Equatorial Current crosses the equator in the Atlantic and to a lesser extent in the Pacific.
In this way, it transports surface waters and heat into the Northern Hemisphere. The return flow is through subsurface currents discussed later.
The cape at the easternmost point of South America diverts part of the flow of the South Equatorial Current into the southward flowing Brazil Current. The remainder continues northwestward along South America's northeast coast into the Caribbean Sea.
Notice the band of bright white clouds in center of the image near the Equator, where the trade winds of the Northern and Southern Hemispheres come together. Why do I care? Ocean circulations have a big impact on weather patterns and atmospheric circulations that affect our weather in the Southeast. I should already be familiar with: Ocean Currents How does wind affect ocean circulation?
Surface ocean currents are primarily affected by wind patterns. Trade winds can push water along the top of the ocean and aid in the formation of surface currents. One example of a wind-driven circulation affecting an ocean current is the Gulf Stream. The Gulf Stream takes very warm water from the Gulf of Mexico and parts of the Caribbean Sea and transports it northward.
During the winter, the Gulf Stream can have a great effect on storm systems along the East Coast of the United States. The boundary between the two sets of trade winds is usually slightly north of the equator. The trade winds set up two westward-flowing currents north and south of the equator the North and South Equatorial Currentsbut because the southeast trades blow across the equator, this causes a divergence upwelling along the equator itself because of the change in direction of the action of the Coriolis force.
Between the two trade-wind belts is a region of generally light winds, known as the Doldrums.
This allows water, which would otherwise pile up against the western boundary of the ocean in the Equatorial currents, to flow back eastwards in the surface Equatorial Countercurrent.
There is also an eastward-flowing Equatorial Undercurrentwhich forms a jet within the thermoclinedriven by the horizontal pressure gradient.
This system of eastward-flowing and westward-flowing currents is found in the upper meters feet in all three oceans, although their distribution may change seasonally depending on the wind forcing. The equatorial undercurrents are much stronger than the surface currents at the equator, and can have flows of more than 50 Sv.
Deep Currents Currents in the deep ocean exist because of changes in the density of sea water occurring at the surface. These density changes give rise to specific water masses, which have well-defined temperature and salinity characteristics, and which can be traced for long distances in the ocean.
When sea water freezes, much of the salt that it contains is frozen out, so that a layer of cold brine forms at the ocean surface. Being denser than the water below it, the brine sinks, entraining water as it does so, until it reaches a level where it has the same density as the surrounding sea water.
This process takes place in several regions of the world's oceans, the most important being in the Greenland, Norwegian, and Labrador Seas in the Northern Hemisphere, and close to the Antarctic continent in the Weddell and Ross Seas in the south.
It is the dense waters formed by this process that set up the deep ocean current patterns. Water formed in the Weddell and Ross Seas spreads eastwards and northwards around Antarctica under the influence of the Coriolis force.
As is the case with surface waters, most of the flow is concentrated on the western sides of ocean basins, but in this case movement is towards the north. In the South Atlantic Oceanfor instance, bottom water from the Weddell Sea can be identified flowing through the Argentine and Brazil Basins below 4, meters 2.
Similar effects are found in both the South Indian and South Pacific oceans, with the bottom waters being forced to follow the bottom topography. Water masses formed in the Northern Hemisphere similarly flow southward. The deep water from the Greenland and Norwegian Seas fills up these basins until it spills over the ridges between Greenland, Icelandand Scotland. From here it is forced to the right by the Coriolis force and follows the topography around the coast of southern Greenland and the Labrador Sea, eventually crossing under the Gulf Stream and flowing south along the east coast of the U.
This water, known as North Atlantic Deep Water NADWcontinues south until it joins the Antarctic Circumpolar Currentfrom where it supplies much of the salt to the deep waters of the southern hemisphere.
The Labrador Sea is also a source of dense water. Since, however, the winter conditions are not as severe here as in the Greenland and Norwegian Seas, the brine produced is less dense and does not sink as deep only 1,—2, meters, or 0.
What are the trade winds?
Role of Water Masses. All these water masses help to transfer oxygen from the atmosphere into the deep ocean. The sinking water is very cold and contains high concentrations of dissolved oxygen acquired at the surface, because cold water can hold more oxygen than warm water. During their flow, they mix with "older" water that has been away from the surface for a longer time, thus ensuring that the bottom waters of the ocean are supplied with oxygen.
In this region, water does not freeze in winter, but it does cool forming a lowsalinity layer that sinks to about 1, meters 0. Water need not be cooled to change its density. Large density changes also can be produced in areas where evaporation is more important than precipitation.
The Climate System
Mediterranean Water can be traced across the North Atlantic because of its high salinity, while Red Sea Water can be followed moving south along the east coast of Africa to the Agulhas Current.
An idealized version of the current patterns throughout the whole ocean is shown in Figure 2. This shows clearly that although the surface and deep current patterns may appear separate, they are actually closely linked. Deep water sinking in the northern North Atlantic is replaced at the surface by warmer water from nearer the equator.