Chapter 6 Flashcards PDF

**acoustical tomography** 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. **Antarctic Bottom Water** The densest ocean water (1.0279 g/cm^3^), formed primarily in Antarctica...

**acoustical tomography** 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. **Antarctic Bottom Water** The densest ocean water (1.0279 g/cm^3^), formed primarily in Antarctica's Weddell Sea during Southern Hemisphere winters. **Antarctic Circumpolar Current (West Wind Drift)** The current driven by powerful westerly winds north of Antarctica. The largest of all ocean currents, it continues permanently eastward without changing direction. **Argo System** **caballing** Mixing of two water masses of identical densities but different temperatures and salinities, such that the resulting mixture is denser than its components. **coastal upwelling** Upwelling adjacent to a coast, usually induced by wind. **contour current** A bottom current made up of dense water that flows around (rather than over) seabed projections. **convergence zone** The line along which waters of different density converge. Convergence zones form the boundaries of tropical, subtropical, temperate, and polar areas. **countercurrent** A surface current flowing in the opposite direction from an adjacent surface current. **current** Mass flow of water. (The term is usually reserved for horizontal movement.) **downwelling** Circulation pattern in which surface water moves vertically downward. **eastern boundary current** 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. **Eddy** 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. **Ekman spiral** 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 45° to the right of the wind in the Northern Hemisphere and 45° to the left in the Southern Hemisphere. Water at successively lower layers drifts progressively to the right (N) or left (S), though not as swiftly as the surface flow. **Ekman transport** 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. **El Niño** A southward-flowing, nutrient-poor current of warm water off the coast of western South America, caused by a breakdown of trade-wind circulation. **ENSO** Acronym for the coupled phenomena of El Niño and the Southern Oscillation. See also *El Niño; Southern Oscillation.* **equatorial upwelling** 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.* **geostrophic gyre** Circular current around the periphery of an ocean basin in balance between the Coriolis effect and the pressure gradient. **global ocean conveyor belt A simplified outline of the three-dimensional global circuit that ocean currents follow as they transport heat around the globe.** **Gulf Stream** The strong western boundary current of the North Atlantic, off the Atlantic coast of the United States. **gyre** Circuit of mid-latitude currents around the periphery of an ocean basin. Most oceanographers recognize five gyres plus the Antarctic Circumpolar Current. **La Niña** 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 also *ENSO.* **Langmuir circulation** Shallow, wind-driven circulation of water in horizontal, spiral bands. **North Atlantic Deep Water** Cold, dense water formed in the Arctic that flows onto the floor of the North Atlantic ocean. **Southern Oscillation** A reversal of airflow between normally low atmospheric pressure over the western Pacific and normally high pressure over the eastern Pacific; the cause of El Niño. See also *El Niño.* **Surface Current** The horizontal flow of water at the ocean's surface. **Sverdrup (sv)** 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. **temperature-salinity (T-S) diagram** A graph showing the relationship of temperature and salinity with depth. **thermohaline circulation** Water circulation produced by differences in temperature and/or salinity (and therefore density). **transverse current** East-to-west or west-to-east current linking the eastern and western boundary currents. An example is the North Equatorial Current. **ndercurrent** A current flowing beneath a surface current, usually in the opposite direction. **upwelling** 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. **West Wind Drift (Antarctic Circumpolar Current)** Current driven by powerful westerly winds north of Antarctica. The largest of all ocean currents, it continues permanently eastward without changing direction. See *Antarctic Circumpolar Current.* **western 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. **westward intensification** The increase in speed of geostrophic currents as they pass along the western boundary of an ocean basin. **wind-induced vertical circulation** Vertical movement in surface water (upwelling or downwelling) caused by wind.