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How the Bering Strait influences Earth's climate

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(Read caption) A gray whale in the waters of the Bering Strait.

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At 50 miles wide, the Bering Strait, which separates Alaska from Russia, hardly seems like a major player in Earth's climate.

But a new study in the journal Nature Geoscience concludes that this shallow strait between the North Pacific and the Arctic oceans has played a large role in climate fluctuations during recent ice ages. Depending on whether it's closed or open, the strait dramatically changes the distribution of heat around the planet.

When sea levels decline enough that water can no longer flow from the Pacific to the Arctic through the strait, the North Atlantic responds by growing warmer. That warmth is strong enough to melt ice sheets and temporarily reverse the glaciation of the Northern Hemisphere.

Generally, scientists think that changes in Earth's orbit around the sun have driven the repeated advance and retreat of glaciers during the Pleistocene — the period starting 2.58 million years ago and ending about 10,000 years ago.

When less sun reaches the Northern Hemisphere during summer months, winter snows don't melt. The white snow reflects more of the sun's energy back into space, further cooling the region. Glaciers form and begin creeping southward. These ice sheets, a mile or more thick in places, suck up large quantities of water.

Compared to today, sea levels dropped by as much as 400 feet during the Pleistocene.

But while glacial periods follows Earth's orbital variations quite closely — they occur very roughly on 100,000-year cycles — for the past 100,000 years or so, a shorter warming and cooling cycle has played out over the larger one.

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