El Niño – Warmer than average water in the Pacific off South AmericaLa Niña – Cooler than average water in the Pacific off South AmericaENSO – El Niño Southern OscillationSouthern Oscillation – Atmospheric oscillation over South Pacific Ocean;Encompasses both El Niño and La Niña.Trade Winds – Easterly winds that blow along the equatorOceanic GyresOcean currents form an anticyclonic circulation (or gyre) in each ocean, in each hemisphereWarm currents east of continentsCold currents west of continents40% of heat transport in Northern Hemisphere occurs in oceansOceanic TemperatureWarmest water typically found at ocean surfaceAbsorbs solar radiationRapid temperature decrease with depth a few hundred meters below surfaceCalled thermoclineDeep ocean waters only a few degrees above freezingEven in summer and near EquatorVery darkUpwellingUpwelling – Vertical transport of deep ocean waters upwardUpwelling results in cooler surface water temperaturesTemperature decreases with depthTypically occurs along west coast of continentsWater temperatures along US west coast only reach upper 50s – lower 60s (F) in summerResults in cooler summers along west coastENSO-Normal ConditionsSurface low pressure near Indonesia (clouds/rain); high pressure near South AmericaResults in easterly (NE in NH, SE in SH) winds across equatorial PacificTrade windsAs winds push water from east to west, water is warmed by sunlightWarmer water to west, cooler water to eastHigher sea level, deeper layer of warm water to westWarm, moist air rises over Western South Pacific OceanClouds, heavy precipitationAir sinks near the west coast of South AmericaClear skies, little precipitationDriest place on earth: Atacama Desert, Chile. Portions average 1 mm (0.04 in) of rain a yearENSO Warm Phase—EL NiñoPressure gradient weakens across equatorial PacificReasons why unknownEasterly winds weakenWarm water flows eastward across PacificWalker Circulation reverses: Clouds/rain in east; dry in westTypically reaches maximum around ChristmasCalled “El Niño” – Means “boy child” (refers to Christ Child)May last for many months, affects large area, occurs every 2-7 yearsEvent ends as surface pressure field returns to normalVary in length and durationEffects of El Niño:Water temperatures may be 6oC (11oF) warmer than normal in Eastern PacificWarm water is nutrient poor (no upwelling)Dead fish, dead birdsDry weather in western Pacific, wet weather in eastern PacificTropical cyclones (hurricanes/typhoons)Increase in eastern/central PacificDecrease in western Pacific and all of AtlanticENSO Cool Phase—La NiñaPressure gradient strengths across equatorial PacificReasons why unknownEasterly Trade winds strengthenIncreases upwelling near South America; cool water flows across PacificWalker Circulation strengthens: More clouds/rain in west; drier in eastEl Niño, La Niña, and Southern Oscillation 11/06/2012El Niño – Warmer than average water in the Pacific off South AmericaLa Niña – Cooler than average water in the Pacific off South AmericaENSO – El Niño Southern OscillationSouthern Oscillation – Atmospheric oscillation over South Pacific Ocean;Encompasses both El Niño and La Niña.Trade Winds – Easterly winds that blow along the equatorOceanic GyresOcean currents form an anticyclonic circulation (or gyre) in each ocean, in each hemisphere-Warm currents east of continents-Cold currents west of continents40% of heat transport in Northern Hemisphere occurs in oceansOceanic TemperatureWarmest water typically found at ocean surface-Absorbs solar radiationRapid temperature decrease with depth a few hundred meters below surface-Called thermoclineDeep ocean waters only a few degrees above freezing-Even in summer and near Equator-Very darkUpwellingUpwelling – Vertical transport of deep ocean waters upward-Upwelling results in cooler surface water temperatures-Temperature decreases with depth-Typically occurs along west coast of continents-Water temperatures along US west coast only reach upper 50s – lower 60s(F) in summeroResults in cooler summers along west coastENSO-Normal Conditions-Surface low pressure near Indonesia (clouds/rain); high pressure near South America-Results in easterly (NE in NH, SE in SH) winds across equatorial PacificoTrade winds-As winds push water from east to west, water is warmed by sunlightoWarmer water to west, cooler water to eastoHigher sea level, deeper layer of warm water to west-Warm, moist air rises over Western South Pacific OceanoClouds, heavy precipitation-Air sinks near the west coast of South AmericaoClear skies, little precipitationoDriest place on earth: Atacama Desert, Chile. Portions average 1 mm (0.04 in) of rain a yearENSO Warm Phase—EL Niño-Pressure gradient weakens across equatorial PacificoReasons why unknownoEasterly winds weaken-Warm water flows eastward across Pacific-Walker Circulation reverses: Clouds/rain in east; dry in west-Typically reaches maximum around ChristmasoCalled “El Niño” – Means “boy child” (refers to Christ Child)-May last for many months, affects large area, occurs every 2-7 yearsoEvent ends as surface pressure field returns to normaloVary in length and duration-Effects of El Niño:oWater temperatures may be 6oC (11oF) warmer than normal in Eastern PacificoWarm water is nutrient poor (no upwelling)Dead fish, dead birdsoDry weather in western Pacific, wet weather in eastern PacificoTropical cyclones (hurricanes/typhoons)Increase in eastern/central PacificDecrease in western Pacific and all of AtlanticENSO Cool Phase—La Niña-Pressure gradient strengths across equatorial PacificoReasons why unknownoEasterly Trade winds strengthen-Increases upwelling near South America; cool water flows across Pacific-Walker Circulation strengthens: More clouds/rain in west; drier in