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Gyres and Currents. Made by Michael Kramer. Coriolis Effect. Apparent deflection of the path of an object that moves within a rotating coordinate system Object doesn’t deviate from path, but appears it does Most apparent in path of an object moving longitudinal
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Gyres and Currents Made by Michael Kramer
Coriolis Effect • Apparent deflection of the path of an object that moves within a rotating coordinate system • Object doesn’t deviate from path, but appears it does • Most apparent in path of an object moving longitudinal • An object moving along North-South path will undergo deflection to its right in Northern Hemisphere and to its left in Southern Hemisphere • This caused by Earth rotating eastward and tangential velocity of a point on Earth is a function of latitude (Velocity is zero at poles and max value is at Equator) • Deflection is related to motion of object, Earth, and latitude. Magnitude is given by 2Sin.
Coriolis Effect Animations and Videos • Coriolis Effect Animation • Coriolis Effect Youtube Video
El Niño • Defined by prolonged differences in Pacific Ocean surface temperatures when compared with average value. • Caused by the Coriolis Effect • Occurs at irregular intervals of 2-7 years and last 9 months to 2 years • When warming/cooling occurs for 7-9 months, it is classified as El Niño conditions. When it occurs for more than 9 months, it is classified as El Niño episodes. • First signs are: rise in surface pressure, fall in air pressure, trade winds, warm air rises near Peru, and warm water spreads from West Pacific and Indian Ocean to East Pacific. • La Niña is the opposite of El Niño, and happens where it corresponds to a lower surface temperature.
Gyres • Large system of rotating ocean currents, generally those involved with large wind movement • Caused by Coriolis Effect • Large mounds of water and flow around them are Gyres and they produce circular currents in all of the ocean basins • Five most common gyres are: Indian Ocean Gyre, North Atlantic Gyre, North Pacific Gyre, South Atlantic Gyre, and South Pacific Gyre • Other gyres include tropical, subtropical, and subpolar
Cool Facts about Gyres • Another name for “swirling vortex” • There is a small gyre in the Arctic Ocean known as the Beaufort Gyre, which is being studied by scientists due to the high amount of freshwater in it • North Pacific Gyre is home to the Great Pacific Garbage Patch that contains about 3 million tons of plastic litter • South Pacific Gyre is Earth’s largest system of rotating ocean currents and center of the gyre is regarded as Earth’s largest oceanic desert • The Southern ocean has two gyres: Weddel and Ross
Currents • Ocean current is a continuous and directed movement of ocean water generated by a variety of forces • These forces include breaking waves, wind, temperature, salinity, tides, and the Coriolis Effect • These currents can flow for vast distances and create the great flow of the global conveyor belt that determines the climate of many regions • Two examples are the Gulf Stream and the California Current
Currents • The balance met between the Coriolis Effect and gravity creates a flow known as a Geostrophic current • Boundary Currents are the main geostrophic currents around the gyre • Difference between Western and Eastern boundary currents is the strength because of rotating of the Earth that moves down the hill of water to western sides of ocean basins • Western boundary currents include: Gulf Stream, Kuroshio Current, Labrador Current, Oyashio Current, Agulhas Current, Brazil Current, and East Australia Current • Eastern boundary currents include: California Current, Canary Current, Peru Current, and Benguela Current
Currents Continued • There are two types of Currents: Surface and Deep Water • Surface Currents make up about 10% of all water in the ocean and are the upper 400 meters of the ocean • Deep Water Currents make up other 90% of the ocean and move around ocean basins by density driven forces and gravity • Currents are influenced by two types of forces: Primary and Secondary • Primary forces start the water moving and are solar heating, winds, gravity, and the Coriolis effect • Secondary Forces influence where the currents flow
Surface Circulation • Solar heating causes the water to expand • The water is about 8 cm higher near the equator than in middle latitudes and this causes a slope that water wants to flow down • Winds blow on the surface of the ocean and push the water • Friction occurs between the wind and water’s surface • A wind blowing for 10 hours across the ocean will cause surface waters to flow at roughly 2% of wind speed • Gravity will pull the water down the pile of water against the pressure gradient • The Coriolis Effect then intervenes and causes the water to move to the right around the mound of water
Ekman Transport • Term given for 90 degree net transport of surface layer due to wind forcings • This was found by Fridtjof Nansen who found ice transport to occur at an angle to the wind direction during his arctic expedition • Direction is dependent on hemisphere. If angle is to the right of the direction of the wind, it is in the Northern Hemisphere. If angle is to the left, it is in the Southern Hemisphere. • The Ekman Transport is the average of the Ekman spiral, which is the spiral created by ocean water at the surface moved by an angle of wind as it turns against the water under the surface.
Upwelling and Downwelling • Upwelling along coast is caused by Ekman transport of waters. These waters are moved offshore and replaced by waters from below. This brings cold and rich water to the surface. • Downwelling is caused by the Ekman transport on shore.
