Which wind drives polar currents

However, recent calculations on the basis of observations suggest that the wind power is only 0. In recent decades, biogenic mixing is thought to be another significant contributor to ocean mixing Katija and Dabiri, [17]. From small zooplankton to large mammals, swimming animals are capable of carrying bottom water with them as they migrate upward, and that movement indeed creates an inversion that results in ocean mixing.

The global power input from this process is estimated in the order of a TW of energy, comparable with levels caused by winds and tides. After all, each day, billions of tiny krill and some jellyfish migrate hundreds of meters from the deep ocean toward the surface where they feed. The deep ocean is a huge storehouse of heat, carbon, oxygen and nutrients. Deep ocean circulation regulates uptake, distribution and release of these elements.

The low overturning rate stabilizes our global climate. By carrying oxygen into the deeper layers it supports the largest habitat on earth. Present theories for explaining the deep ocean circulation predict that global warming will have a negative impact on the deep ocean circulation.

Most studies have focused on the northern Atlantic [18]. The formation of dense sinking surface water in the Arctic region will be counteracted by a higher atmospheric temperature and by release of fresh water by ice melting. The feeding of the Atlantic Meridional Overturning Circulation , which drives warm Gulf Stream waters to the north, will thus be reduced.

Besides, the density of the North Atlantic Deep Water will be lower; therefore the cold return current will flow closer to the ocean surface. It is expected that these factors will cause significant cooling of the West European climate. Model simulations indicate that this may entail considerable warming of deep waters in the entire Pacific; it may also affect the Atlantic by strengthening the Atlantic Meridional Overturning Circulation.

The impact of fresh water releases in the Antarctic region on the global climate and sea-level rise could even be greater than the impact of freshening of the Arctic waters, as discussed in the article Thermohaline circulation of the oceans. Rahmstorf: Thermohaline Ocean Circulation.

Elsevier, Amsterdam Log in. Page Discussion. Read View source View history. Jump to: navigation , search. Article reviewed by. Job Dronkers See the discussion page. On the wind-driven ocean circulation. Cook was the first person to use the term, Southern Ocean, to describe this area.

Despite its relatively slow eastward flow of less than 20 cm s -1 in regions between the fronts, the ACC transports more water than any other current Klinck and Nowlin, The ACC extends from the sea surface to depths of m and can be as wide as km. This tremendous cross-sectional area allows for the current's large volume transport. The Antarctic Circumpolar Current's eastward flow is driven by strong westerly winds.

Historically, the ACC has been referred to as the 'West Wind Drift' because the prevailing westerly wind and current are both eastward. Without the aid of continental reference point, except for the Drake Passage, where by convention, all flow through the Passage is the ACC, the current's boundaries are generally defined by zonal variations in specific water properties of the Southern Ocean Gordon et al.

Variations in these properties have been used to classify regions whose edges are defined by fronts, where there is rapid changes in water properties which occur over a short distance. The Antarctic Convergence is approximately km south of the Polar Front. A fourth zone, the Continental Zone, and the westward flowing Antarctic Coastal or Polar Current are located even further poleward, between the Southern Front and the Antarctic continent.

A region of upwelling, the Antarctic Divergence, occurs at the Southern Front. This area of divergence has been considered to be the ACC's southern boundary Klinck and Nowlin, but new analysis puts the southern boundary of the ACC further poleward.

Orsi et al. Northward displacement of the southern boundary of the ACC are in the areas of gyres with clockwise surface circulation in the Weddell Sea and in the Ross Sea. Strong, nearly zonal, westerly winds force a large, near-surface, northward Ekman transport and a northward pressure gradient. The ACC current is in approximately geostrophic equilibrium, so that inclined layers of constant density slope towards the surface poleward across the ACC to balance the current's northward sea surface height elevation.

The alignment between the prevailing winds and the resulting geostrophic current intensifies the ACC. Because stronger gradients give rise to stronger flow, the majority of the ACC transport is associated with the fronts within the current.

Other investigators have found meander wavelengths between and km. In the vicinity of the fronts, eastward jets flow at approximately two to three times the speed of the current found between them Klinck and Nowlin, Zambianchi et al.

Meridional ridges in the bottom topography provide a force balance for the Atlantic Circumpolar Current by generating frictional form drag. As the ACC crosses these ridges, frictional drag diminishes the current's deep flow Munk and Palmen, Bottom topography also controls the path of the ACC, since slow large-scale oceanic flows are, on the average, parallel to lines of constant planetary vorticity approximately the Coriolis acceleration divided by the water depth.

The degree of topographic blocking will also influence the current's eddy kinetic energy. This leaves a void that is filled by deep water that rises to the surface. Upwelling is extremely important where it occurs. During its time on the bottom, the cold deep water has collected nutrients that have fallen down through the water column. Upwelling brings those nutrients to the surface.

Those nutrient support the growth of plankton and form the base of a rich ecosystem. Upwelling also takes place along the equator between the North and South Equatorial Currents. Winds blow the surface water north and south of the equator so deep water undergoes upwelling. The nutrients rise to the surface and support a great deal of life in the equatorial oceans. Skip to main content. The Ocean.

Search for:. Currents Surface Currents Ocean water moves in predictable ways along the ocean surface. Surface currents are created by three things: global wind patterns the rotation of the Earth the shape of the ocean basins Surface currents are extremely important because they distribute heat around the planet and are a major factor influencing climate around the globe. Global Wind Patterns Winds on Earth are either global or local.

The major surface ocean currents. Lesson Summary Ocean surface currents are produced by global winds, the Coriolis effect and the shape of each ocean basin. The Pacific and Atlantic Oceans have a circular pattern of surface currents called gyres that circle clockwise in the Northern Hemisphere and counterclockwise in the Southern. The Indian Ocean only has a counterclockwise gyre.

Surface ocean circulation brings warm equatorial waters towards the poles and cooler polar water towards the equator. Thermohaline circulation drives deep ocean currents. Upwelling of cold, nutrient-rich waters creates biologically rich areas where surface waters are blown away from a shore, or where equatorial waters are blow outward.

Review Questions What causes the patterns of surface currents in the ocean? How do ocean surface currents affect climate? Scientists across the globe are trying to figure out why the ocean is becoming more violent and what, if anything, can be done about it. Ocean currents, including the ocean conveyor belt, play a key role in determining how the ocean distributes heat energy throughout the planet, thereby regulating and stabilizing climate patterns.

A current is the steady, predictable movement of a fluid within a larger body of that fluid. Fluids are materials capable of flowing and easily changing shape. A gyre is a circular ocean current formed by the Earth's wind patterns and the forces created by the rotation of the planet.

Join our community of educators and receive the latest information on National Geographic's resources for you and your students. Skip to content. Image Rubber Duck on the Beach A rubber duck washed up on the beach after being carried out in the ocean. Twitter Facebook Pinterest Google Classroom. Encyclopedic Entry Vocabulary. Coriolis effect. 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.

Media If a media asset is downloadable, a download button appears in the corner of the media viewer. Text Text on this page is printable and can be used according to our Terms of Service. Interactives Any interactives on this page can only be played while you are visiting our website. Related Resources. Plastic Pollution. View Collection. Ocean Currents and Climate.