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 waterFriction 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.