The ocean The ocean currents currents exerciseexercise

Ocean surface Ocean surface currents can becurrents can be

Ocean surface currents Ocean surface currents are driven byare driven by

Warm (and fast) or

Cold (and sluggish)

Westward flow of equatorial surface wind

Earth’s rotation

Gravitational roll-back of the waters that equatorial surface wind stacks on the western margins of tropical/semitropical oceans.

The westward flow of equatorial The westward flow of equatorial surface wind produces anticyclonic surface wind produces anticyclonic current gyres.current gyres.

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They start with North Equatorial and South Equa-torial currents, in the Atlantic (1, 2), Pacific (3, 4) and Indian (only 5) oceans.

Warm

Cold

1 North Equatorial Current in the Atlantic Ocean2 South Equatorial Current in the Atlantic Ocean3 North Equatorial Current in the Pacific Ocean4 South Equatorial Current in the Pacific Ocean5 South Equatorial Current in the Indian Ocean

Why no North Equatorial Current in the Indian Ocean?

The westward flow of equatorial The westward flow of equatorial surface wind produces anticyclonic surface wind produces anticyclonic current gyres.current gyres.

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6 Kuroshio or Japan Current 7 East Australian Current 8 Gulf Stream 9 Brazil Current10 Agulhas Current

Blocked by land, these currents turn polewards.

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The westward flow of equatorial The westward flow of equatorial surface wind produces anticyclonic surface wind produces anticyclonic current gyres .current gyres .

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Cold

11 California Current12 Peru Current13 Canary Current14 Benguela Current15 West Auatralian Current

They cool down as they reach ~45°, and return as cold water currents

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Earth’s rotation produces the Circum-Earth’s rotation produces the Circum-Antarctic or Circum-Polar Current.Antarctic or Circum-Polar Current.

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Cold

Also called the West Wind Drift, this cold water current is the only ocean surface current that joins the waters of all the oceans.

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Circum-Antarctic Circulation

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Equatorial Counter Current is the Equatorial Counter Current is the gravity driven roll-back of warm gravity driven roll-back of warm waters stacked on western waters stacked on western margins of the tropical ocean by margins of the tropical ocean by westward flowing equatorial westward flowing equatorial surface wind.surface wind.

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Circum-Antarctic Circulation

ECC ECC ECC

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A bottle dropped by Scripps off Perth, A bottle dropped by Scripps off Perth, Australia, took 5 years to reach Miami, Australia, took 5 years to reach Miami, Florida, located about 26,000 km Florida, located about 26,000 km away.away.

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Circum-Antarctic Circulation

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What currents did it ride on?What currents did it ride on?What was its average speed?What was its average speed?