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Gyres and CurrentsMade by Michael Kramer
Coriolis EffectApparent deflection of the path of an object that
moves within a rotating coordinate systemObject doesn’t deviate from path, but appears it
doesMost apparent in path of an object moving
longitudinalAn 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 VideosCoriolis Effect Animation
Coriolis Effect Youtube Video
El NiñoDefined by prolonged differences in Pacific Ocean surface
temperatures when compared with average value. Caused by the Coriolis EffectOccurs at irregular intervals of 2-7 years and last 9 months
to 2 yearsWhen 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.
Pictures of El Niño
GyresLarge system of rotating ocean currents, generally
those involved with large wind movementCaused by Coriolis EffectLarge 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
Map of Gyres
Picture of Gyre
Cool Facts about GyresAnother 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
CurrentsOcean 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
CurrentsThe balance met between the Coriolis Effect and gravity
creates a flow known as a Geostrophic currentBoundary Currents are the main geostrophic currents
around the gyreDifference 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 ContinuedThere are two types of Currents: Surface and Deep
WaterSurface Currents make up about 10% of all water in
the ocean and are the upper 400 meters of the oceanDeep 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 CirculationSolar heating causes the water to expandThe 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 surfaceA wind blowing for 10 hours across the ocean will cause
surface waters to flow at roughly 2% of wind speedGravity will pull the water down the pile of water against
the pressure gradientThe Coriolis Effect then intervenes and causes the water
to move to the right around the mound of water
Pictures
Ekman TransportTerm given for 90 degree net transport of surface layer
due to wind forcingsThis 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.
Ekman Transport Pictures
Upwelling and DownwellingUpwelling 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.
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