Oceanography Chapter 9
Terms
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- The increase in speed of geostrophic currents as they pass along the western boundary of an ocean basin
- westward intensification
- Weak, cold, diffuse, slow-moving current at the eastern boundary of an ocean (off the west coast of a continent). Examples include the Canary Current and the Humboldt Current
- eastern boundary current
- Strong, warm, concentrated, fast-moving current at the western boundary of an ocean (off the east coast of a continent). Examples include the Gulf Stream and the Japan (Kuroshio) Current
- western boundary current
- A method of current study that measures the current as it flows past a fixed object
- flow method
- The densest ocean water (1.0279 g/cm3), formed primarily in Antarctica's Weddell Sea during Southern Hemisphere winters
- Antarctic Bottom Water
- Acronym for the coupled phenomena of El Niqo and the Southern Oscillation. See also El Niqo; Southern Oscillation.
- ENSO
- Circulation pattern in which surface water moves vertically downward
- downwelling
- Upwelling in which water moving westward on either side of the geographical equator tends to be deflected slightly poleward and replaced by deep water often rich in nutrients. See also upwelling.
- equatorial upwelling
- Net water transport, the sum of layer movement due to the Ekman spiral. Theoretical Ekman transport in the Northern Hemisphere is 90°̊ to the right of the wind direction
- Ekman transport
- Winds that blow steadily across the ocean, and the small waves that such winds generate, can induce long sets of counter-rotating cells in the surface water.
- Langmuir circulation
- Mass flow of water. (The term is usually reserved for horizontal movement.)
- Current
- The strong western boundary current of the North Atlantic, off the east coast of the United States
- Gulf Stream
- Mixing of two water masses of identical densities but different temperatures and salinities, such that the resulting mixture is denser than its components
- caballing
- A surface current is flowing in the opposite direction from an adjacent surface current
- countercurrent
- Circuit of mid-latitude currents around the periphery of an ocean basin. Most oceanographers recognize five gyres plus the West Wind Drift
- gyre
- A current flowing beneath a surface current, usually in the opposite direction.
- Undercurrent
- An event during which normal tropical Pacific atmospheric and oceanic circulation strengthens, and the surface temperature of the eastern South Pacific drops below average values. Usually occurs at the end of an ENSO event. See ENSO
- La Nina
- A theoretical model of the effect on water of wind blowing over the ocean. Because of the Coriolis effect, the surface layer is expected to drift at an angle of 45°̊ to the right of the wind in the Northern Hemisphere and 45°̊ to the left in the Sout
- Ekman spiral
- Water circulation produced by differences in temperature and/or salinity (and therefore density).
- thermohaline circulation
- Upwelling adjacent to a coast, usually induced by wind
- coastal upwelling
- Reversals of airflow between normally low atmospheric pressure over the western Pacific and normally high pressure over the eastern Pacific. The cause of El Niqo. See El Niqo
- Southern Oscillation
- A technique for studying ocean structure that depends on pulses of low-frequency sound to sense differences in water temperature, salinity, and movement beneath the surface.
- acoustical tomography
- Circulation pattern in which deep, cold, usually nutrient-laden water moves toward the surface. Upwelling can be caused by winds blowing parallel to shore or offshore.
- Upwelling
- A unit of volume transport named in honor of oceanographer Harald U. Sverdrup: 1 million cubic meters of water flowing past a fixed point each second
- sverdrup (sv)
- A southward-flowing nutrient-poor current of warm water off the coast of western South America, caused by a breakdown of trade wind circulation
- El Nino
- Vertical movement in surface water (upwelling or downwelling) caused by wind
- wind-induced vertical circulation
- The line along which waters of different density converge. Convergence zones form the boundaries of tropical, subtropical, temperate, and polar areas
- convergence zone
- A method of current study that depends on the movement of a drift bottle or other free-floating object.
- float method
- Horizontal flow of water at the ocean's surface
- Surface Current
- A circular movement of water usually formed where currents pass obstructions, or between two adjacent currents flowing in opposite directions, or along the edge of a permanent current
- eddy
- The Antarctic Circumpolar Current, driven by powerful westerly winds north of Antarctica. The largest of all ocean currents, it continues permanently eastward without changing direction
- The Antarctic Circumpolar Current (West Wind Drift)
- A bottom current made up of dense water that flows around (rather than over) seabed projections
- contour current
- A graph showing the relationship of temperature and salinity with depth.
- temperature-salinity (T-S) diagram
- East-to-west or west-to-east current linking the eastern and western boundary currents. An example is the North Equatorial Current
- transverse current
- Describing a gyre or current in balance between the Coriolis effect and gravity; literally, "turned by the Earth
- geostrophic