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Ocean Currents
Why is Ocean Circulation Important?
Transport heatEquator to poles
Transport nutrients and organisms
Influences weather and climate
Influences commerce
Surface Currents
The upper 400 meters of the ocean (10%).
Deep Water Currents
Thermal/Salinity currents (90%)
Ocean Currents
Wind-driven surface currents
30o
30o
60o
60o
90o
90o
0o
Forces
1. Solar Heating (temp, density)
2. Winds
3. Coriolis
Surface Currents
What do Nike shoes, rubber ducks, and hockey gloves have to do with currents?
Lost at Sea
• January 1992 - shipwrecked in the Pacific Ocean, off the coast of China
• November 1992 - half had drifted north to the Bering Sea and Alaska; the other half went south to Indonesia and Australia
• 1995 to 2000 - spent five years in the Arctic ice floes, slowly working their way through the glaciers2001 - the duckies bobbed over the place where the Titanic had sunk
• 2003 - they were predicted to begin washing up onshore in New England, but only one was spotted in Maine
• 2007 - a couple duckies and frogs were found on the beaches of Scotland and southwest England.
Duckie Progress
2004-2007 Barber’s Point
Surface and Deep-Sea Current Interactions
“Global Ocean Conveyor Belt”
Transport by CurrentsSurface currents play significant roles in transport
heat energy from equatorial waters towards the poles
Currents also involved with gas exchanges, especially O2 and CO2
Nutrient exchanges important within surface waters (including outflow from continents) and deeper waters (upwelling and downwelling)
Pollution dispersalImpact on fisheries and other resources
Global ocean circulation that is driven by differences in the density of the sea water which is controlled by temperature and salinity.
White sections represent warm surface currents. Purple sections represent deep cold currents
Upwelling and downwellingVertical movement of water
Upwelling = movement of deep water to surface Hoists cold, nutrient-rich water to surface Produces high productivities and abundant marine life
Downwelling = movement of surface water down Moves warm, nutrient-depleted surface water down Not associated with high productivities or abundant
marine life
upwelling
downwelling
El Niño-Southern Oscillation (ENSO)El Niño = warm surface current in equatorial eastern
Pacific that occurs periodically around DecemberSouthern Oscillation = change in atmospheric
pressure over Pacific Ocean accompanying El NiñoENSO describes a combined oceanic-atmospheric
disturbance
El Niño• Oceanic and atmospheric
phenomenon in the Pacific Ocean• Occurs during December• 2 to 7 year cycle
Sea Surface Temperature
Atmospheric Winds
Upwelling
Normal conditions in the Pacific Ocean
El Niño conditions (ENSO warm phase)
La Niña conditions (cool phase; opposite of El Niño)
El NiñoNon El Niño
1997
Non El Niño
El Niño
Thermocline – layer of ocean right beneath the “mixed layer” where temperatures decrease rapidly.
upwelling
El Niño events over the last 55 years
El Niño warmings (red) and La Niña coolings (blue) since 1950. Source: NOAA Climate Diagnostics Center
El Nino Animation
World Wide Effects of El Niño
• Weather patterns
• Marine Life
• Economic resources
Effects of severe El Niños
