Which one of the following is not correct?

Correct — D, The California Current is a warm ocean current. It is cold. The California Current runs southward down the western coast of North America as the eastern limb of the North Pacific gyre, dragging sub-polar water towards the tropics, and the upwelling along that coast makes the water colder still — which is why San Francisco has fog in July. The other three statements are accurate as printed.

• (a)The Gulf Stream is a warm ocean current. — True. It is the western boundary current of the North Atlantic, carrying tropical water north-east past Florida.
• (b)The North Atlantic Drift is a warm ocean current. — True. It is the Gulf Stream's continuation across the Atlantic, and it is why Norwegian ports stay ice-free at latitudes where Canadian ones freeze.
• (c)The Labrador Current is a cold ocean current. — True. It brings Arctic water south past Newfoundland, and its meeting with the Gulf Stream produces the fog and the fishing grounds of the Grand Banks.

Surface currents circle each ocean basin as a gyre, clockwise in the northern hemisphere and anticlockwise in the southern. Position inside that gyre, not name, decides temperature: the western boundary current carries equatorial water poleward and is warm, while the eastern boundary current returns cool water towards the equator and is cold.

That rule turns a memory list into one decision. Warm western boundary currents: Gulf Stream, Kuroshio, Brazil, Agulhas, East Australian. Cold eastern boundary currents: California, Canary, Benguela, Peru or Humboldt, West Australian. California sits on the eastern side of the Pacific, so the moment you place it on the map the statement fails. Upwelling along these eastern margins also explains why the world's great fisheries sit off Peru, California and Namibia.

• The California Current is the cold eastern limb of the North Pacific gyre.
• The Gulf Stream and its extension, the North Atlantic Drift, keep north-west Europe far milder than its latitude implies.
• The Labrador Current meets the Gulf Stream off Newfoundland, producing the Grand Banks fog.
• Prevailing winds are the main driver of surface currents; the Coriolis effect, water density and the shape of the sea floor modify them.
• Cold eastern-boundary currents are associated with coastal upwelling and with dry coasts such as Atacama and Namib.

• Memorising current names without their side of the ocean.
• Assuming a current flowing away from the pole must be warm.

One statement in four is false, or a straight 'which of these is a cold current' item.

• practice — not a real PYQ

  Which one of the following pairs of currents is warm?

  • (a)Kuroshio and Brazil
  • (b)Canary and Benguela
  • (c)Peru and California
  • (d)Labrador and Oyashio

  Answer(a) Kuroshio and Brazil — both are western boundary currents carrying tropical water poleward.

• practice — not a real PYQ

  Cold eastern-boundary currents are associated with

  • (a)heavy coastal rainfall
  • (b)coastal upwelling and rich fisheries
  • (c)the formation of tropical cyclones
  • (d)ice-free winter ports in high latitudes

  Answer(b) coastal upwelling and rich fisheries — nutrient-rich water rises along coasts such as Peru, California and Namibia.