The Arctic wasn't always covered in ice. 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. The work is in the journal Science. [Julie Brigham-Grette et
al., Pliocene Warmth, Polar Amplification, and Stepped Pleistocene Cooling
Recorded in NE Arctic Russia]
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. 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. These warm temperatures, which supported plants like
Douglas fir and hemlock, lasted until about 2.2 million years ago.
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. These
changes help us understand details about the development of Ice Ages. In
addition, the sediment comes from a window of time during the Pliocene Epoch,
when greenhouse gas levels were only slightly higher than they are today.
Such sensitivity to small carbon dioxide changes hint at a warm Arctic future.
題目是:
Which era did the sediment which revealed the temparature of the summers back
during the formation of the El'gygytgyn belong to?
請英文強的大大幫忙解一下感謝>__<
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