The basic understanding of ocean currents is that warm currents carry moisture whereas cold currents carry nutrients. This is why some scientists believe in the connection between the Arctic ice caps and the warm Gulf Stream and the frigid Humboldt and Benguela currents turning the tropical lands of Chile and Namibia bone-dry.

With that, there are some confusions with the workings of coldwater ocean currents. Antarctica is surrounded by the Antarctic Circumpolar Current, a coldwater current, yet it is covered in mile after mile of frozen water. The Pacific coast of North America is nurtured by coldwater currents, yet we see temperate rainforests.

So what's going on? Why are there habitats that require a lot of moisture near coldwater ocean currents that can't carry that much?

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    $\begingroup$ I don't get this question at all. What do moisture in the air and nutrients in the water have to do with each other? 'Worse': The Pacific coast of North America is nurtured by coldwater currents, yet we see temperate rainforests suggests that nutrients from the ocean contribute to rainforests????? $\endgroup$
    – Jan Doggen
    Jul 28 '16 at 10:12
  • $\begingroup$ @JanDoggen Why must I repeat that warm ocean currents carry moisture whereas cold ocean currents carry nutrients? $\endgroup$ Jul 28 '16 at 13:28
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    $\begingroup$ Nobody says you have to repeat. Actually, just repeating does not add anything. I specifically mention in the air versus in the water. If you think you don't have to explain that discrepancy, fine. It's your question, you get better/more answers the clearer your question is. Moving on... $\endgroup$
    – Jan Doggen
    Jul 28 '16 at 13:43
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    $\begingroup$ @TomAu The California Current is cold. $\endgroup$ Jul 29 '16 at 1:30
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    $\begingroup$ @JohnWDailey: The North Pacific current en.wikipedia.org/wiki/North_Pacific_Current splits into the California current (south but cold), and the Alaska current (north but warm). The latter impacts Oregon and Washington. Go figure. $\endgroup$
    – Tom Au
    Jul 29 '16 at 1:39

The currents run counterclockwise. That's why the Humboldt Current cools the Pacific coast of South America, because the water is coming from the "six o'clock" position in the Antarctica. But in the Northern Hemisphere, the "six o'clock" position is warm water near the equator, which warms Oregon and Washington.

In the northern hemisphere, the cold Labrador current cools land to its west. That's because the water is coming from the "12 o'clock position near the Arctic. On the other hand, the west coast benefits from warm water currents running in a counterclockwise direction. That's because the "6 'oclock" position in the northern hemisphere is near the tropics, which brings warm water to Washington and Oregon at the "2-3 o'clock" position.

All other things being equal, colder air carries less moisture than warm air, and land near cold water currents is dryer than land near warm water currents.

  • $\begingroup$ I don't see what this has to do with moisture. $\endgroup$ Jul 28 '16 at 13:27
  • $\begingroup$ @JohnWDailey: Added a new last sentence. $\endgroup$
    – Tom Au
    Jul 28 '16 at 14:59
  • $\begingroup$ So why is Antarctica covered in ice, which is solidified water? Why is the Pacific coast of North America covered in rainforest? $\endgroup$ Jul 28 '16 at 15:55
  • $\begingroup$ @JohnWDailey: The Antarctica is like the Arctic in being covered with ice. So a "counterclockwise" current brings the cold water to South America. In the northern hemisphere, the counterclockwise current brings water from the tropics (6 o'clock position) to Oregon and Washington (2-3 o'clock.). $\endgroup$
    – Tom Au
    Jul 28 '16 at 16:18

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