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The frozen surface of Greenland appears to be solid and impenetrable. But trapped inside this ancient ice are tiny time capsules of environmental history. I’m Jim Metzner and this is the Pulse of the Planet. Geologists are studying ice to learn about changes in the earth’s climate stretching as far back as 400 hundred thousand years ago. Ed Brook, an Assistant Professor at Washington State University, examines these ice cores — cylinders drilled out of the ice sheets over both Greenland and Antarctica. He says one reason there’s history in this ice is that it contains ancient air.
“The way that air is trapped in the ice is fairly simple. When you’re sitting on top of a polar ice sheet, right beneath you is snow that’s recently fallen, and as the snow continues to fall, the snow grains compact and they eventually become ice, and it’s not like snow in your backyard that melts. The snow just falls and sits there and compacts and turns into ice. And as it cements together, there’s air between the snow crystals and eventually they cement together and trap the air between the grains. The little air bubbles trap the air and, in most cases, it’s not altered by the passage of time, so it provides us with a pretty direct measurement of the composition of the air. We know from studying ice cores that greenhouse gases like carbon dioxide and methane have been rising since the 1800’s and have reached levels now that are much higher than ever observed in the ice core records. The rising levels of carbon dioxide are undoubtedly due to industrial activities, burning of fossil fuels. And all these things have made a pretty big impact on the atmospheric composition of these gases.”
If you’d like to hear about our new Pulse of the Planet CD, please visit our website at pulseplanet.com. Pulse of the Planet is made possible by the National Science Foundation.
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