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1 .This is Scientific American 60-Second Science. I'm Sophie Bushwick. Got a minute?
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2 .The Arctic wasn't always covered in ice.
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3 .Samples of sediment layers beneath a frozen lake show this region used to be a lot warmer, and may thaw out again in the future.
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4 .The work is in the journal Science.
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5 .El'gygytgyn, a Russian lake 100 kilometers north of the Arctic Circle, contains layers of sediment that date back to the lake's formation 3.6 million years ago.
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6 .Analyses of sediment cores have revealed that back then summers reached about 15 to 16 degrees Celsius, a good 8 degrees warmer than modern Arctic summers.
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7 .These warm temperatures, which supported plants like Douglas fir and hemlock, lasted until about 2.2 million years ago.
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8 .Using a sediment core as a detailed history of climate change, scientists can see how the forested Arctic gradually became covered in ice and snow.
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9 .These changes help us understand details about the development of Ice Ages.
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10 .In addition, the sediment comes from a window of time during the Pliocene Epoch,
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11 .when greenhouse gas levels were only slightly higher than they are today.
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12 .Such sensitivity to small carbon dioxide changes hint at a warm Arctic future
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13 .Thanks for the minute, for Scientific American 60-Second Science. I'm Sophie Bushwic.
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