Surface Current Formation - Helms Science...

Surface Current Formation

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GyresA circular pattern formed by the connection ofseveral surface currents.

Northern Hemisphere2 gyres - clockwise rotation

Southern Hemisphere3 gyres – counter-clockwise rotation

Gyres are named for the ocean & hemispherethey are found in.

Parts of a GyreWestern Boundary Currents

1. Form on the western sides of oceans.2. Fast, deep, narrow currents that form eddies. 3. Warm currents b/c they flow from the equator.

5 Main WBCs: Gulf Stream – largestJapan Current (aka Kuroshio c.)Brazil CurrentAgulhas CurrentEast Australian Current

Parts of a Gyre

Eastern Boundary Currents

1. Form on the eastern sides of oceans.2. Slow, shallow, broad currents with no eddies. 3. Cold currents b/c they flow from the poles.

5 Main EBCs: Canary CurrentCalifornia CurrentPeru CurrentBenguela CurrentWest Australian Current

Currents going towards the equator (away from the poles) are cold water currents.

Current going towards the poles (away from the equator) are warm water currents.

Currents Lab

N. Pacific

N. EquatorialN. Equatorial

S. EquatorialS. Equatorial

S. Equatorial

EquatorialEquatorial Counter

West Wind Drift West Wind DriftWest Wind Drift

Density-Driven Ocean Circulation

Cold, dense water sinks below warmer water.

Salty, dense water sinks below less salty water.

Just like air, water will move to areas of lesser concentration.

There are different density layers found in the ocean.

Water Masses Bodies of water that are fairly uniform in their

densities.

Identifiable from their temperature, salinity and other characteristics.

Mixed/Surface Layer The top few hundred meters.

Here the water is mixed around by wind, waves & surface currents.

Has a relatively uniform temp. & salinity throughout.

Intermediate Layer

Immediately below the mixed layer.

It is more dense than the mixed layer due to temp. and/or salinity.

North Atlantic Deep Water (NADW)

From below the intermediate water to the ocean bottom.

Very cold water w/ higher salinity than the above layers.

Antarctic Bottom Water (AABW)

In contact w/ the seafloor.

Extremely cold water.

Typically nutrient rich.

Can travel around the globe for years.

Great Ocean Conveyor Belt Combination of deep ocean currents &

surface currents