WEBVTT - How Much Can Ice Tell Us About Climate Change?

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<v Speaker 1>Welcome to Brainstuff from how Stuff Works, Hey, brain Stuff,

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<v Speaker 1>Lauren Vogel bomb here the history of life is chronicled

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<v Speaker 1>in our fossil record. Scientists use skeletons, trackways, and other

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<v Speaker 1>tangible calling cards to learn new things about prehistoric organisms.

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<v Speaker 1>But how do they study prehistoric climates? Unlike dinosaurs or mastodon's,

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<v Speaker 1>the climate has no bones to leave behind, no footprints

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<v Speaker 1>to track. Telltale indicators of past weather conditions can still

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<v Speaker 1>be found, though, if you know where to look for them.

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<v Speaker 1>One important line of evidence lies inside the world glacial ice.

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<v Speaker 1>Glaciers form where snow is steadily accumulating but not melting. Slowly,

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<v Speaker 1>the weight of new layers deforms the snow crystals below them.

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<v Speaker 1>The compression fuses old buried snowflakes together until they become

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<v Speaker 1>a dense, rock hard sheet of ice. Eventually that becomes

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<v Speaker 1>a glacier, which is a towering pile of these sheets.

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<v Speaker 1>The oldest of those sit at the bottom of the glacier.

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<v Speaker 1>Scientists like to describe glacial ice as a kind of

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<v Speaker 1>annual record. While a new layer forms, tiny bubbles of

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<v Speaker 1>air get trapped inside. By analyzing that trapped air, they

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<v Speaker 1>can determine how much greenhouse gas was in the atmosphere

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<v Speaker 1>back when a given chunk of ice first solidified. Hardening

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<v Speaker 1>Glacial ice can also trap volcanic ash, which lets us

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<v Speaker 1>know when an ancient eruption must have taken place. Other

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<v Speaker 1>things extrapolated from the ice include the strength of prehistoric

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<v Speaker 1>winds and the global temperatures of bygone ages. This precious

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<v Speaker 1>information is harvested via drilling. With the help of mechanical

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<v Speaker 1>or thermal drills, a research team can extract a tall,

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<v Speaker 1>vertical cross section from a glacier. Glaciologists call these frozen

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<v Speaker 1>columns ice cores. The shortest are usually around a hundred

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<v Speaker 1>meters or three d and thirty feet long, but cores

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<v Speaker 1>stretching more than three kilometers or about two miles from

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<v Speaker 1>end to end have also been collected. During the extraction process,

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<v Speaker 1>a core is broken up into smaller pieces, which are

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<v Speaker 1>then placed into metal cylinders and stored in chilled laboratories.

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<v Speaker 1>A convenient feature of glaciers, at least for researchers, is

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<v Speaker 1>the fact that they're made up of annual layers. By

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<v Speaker 1>counting these, like tree rings, scientists can get a good

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<v Speaker 1>idea of how old an ice core segment is. Another

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<v Speaker 1>applicable technique is radiometric dating. Also helpful is the global

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<v Speaker 1>distribution of glaciers. There's at least one glacier on every

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<v Speaker 1>continent except Australia. Despite this, most of the ice cores

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<v Speaker 1>recovered so far were drilled in either Greenland or Antarctica.

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<v Speaker 1>That's not to say scientists are ignoring glaciers in other places.

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<v Speaker 1>In mid December, researchers announced that they had an ice

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<v Speaker 1>core of huge historical importance that was removed from the

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<v Speaker 1>Tibetan Plateau. The news comes out of Ohio State University,

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<v Speaker 1>which gave an update on the results of a joint

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<v Speaker 1>expedition by scientists from the school's Bird Polar and Climate

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<v Speaker 1>Research Center and the Chinese Institute of Tibetan Plateau Research.

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<v Speaker 1>Their venture began in September and October off when the

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<v Speaker 1>international party made its way to the Galia ice Cap

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<v Speaker 1>in Tibet's western Glenland Mountains. Accompanying them was six tons

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<v Speaker 1>or five point four metric tons of equipment that was

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<v Speaker 1>flown over from the United States. They're jective drill new

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<v Speaker 1>ice cores to enhance our knowledge of West Tibet's glacial history.

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<v Speaker 1>By investigating the past, we may be able to make

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<v Speaker 1>predictions about the area's uncertain future. More than one point

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<v Speaker 1>four billion people get their fresh water from the forty

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<v Speaker 1>six thousand glaciers that stand on the Tibetan Plateau, a

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<v Speaker 1>region nicknamed the Third Pole, but climate change has put

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<v Speaker 1>the area's long term stability in question. According to a

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<v Speaker 1>report published in the journal Nature, most of the glaciers

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<v Speaker 1>in Tibet have shrunk over the past thirty years, and

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<v Speaker 1>melting ice from Tibet's highlands has been cited as a

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<v Speaker 1>large contributor to the rise of global sea levels. Altogether,

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<v Speaker 1>the international team pulled five ice cores out of Galia.

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<v Speaker 1>The longest among them is a record holder at one

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<v Speaker 1>thousand feet that's about three five meters. It's nearly twice

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<v Speaker 1>as long as the Washington Monument is high. Even more

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<v Speaker 1>significant is its age. The lowest layers were formed around

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<v Speaker 1>six hundred thousand years ago. That's the oldest date ever

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<v Speaker 1>represented in an ice core that was found outside of

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<v Speaker 1>Earth's two polar circles. From a certain point of view,

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<v Speaker 1>it's still just a baby though. Some two point seven

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<v Speaker 1>million year old glacial ice was taken from an Antarctic

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<v Speaker 1>core in Still, that doesn't diminish the importance of these

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<v Speaker 1>new Tibetan cores. It isn't every day that humanity finds

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<v Speaker 1>six hundred millennia worth of preserved climate history. Plus any

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<v Speaker 1>addition to the global ice core supply will only benefit

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<v Speaker 1>future research. By consulting the cores found in different parts

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<v Speaker 1>of the world, scientists can figure out if historic weather

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<v Speaker 1>trends were universal or just regional. In the early twenty teens,

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<v Speaker 1>for example, scientists compared specimens from Tibet and Europe. The

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<v Speaker 1>data showed that while the latter continents saw temporary warm

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<v Speaker 1>period in medieval times, central Asia most likely didn't. Chinese

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<v Speaker 1>and American scientists will be putting these newfound cores through

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<v Speaker 1>an intensive chemical analysis over the next few months. We'll

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<v Speaker 1>keep you updated. Today's episode was written by Mark Mancini

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<v Speaker 1>and produced by Tristan McNeil. For more on this and

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<v Speaker 1>lots of other glacial topics, visit our home planet, faustive

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<v Speaker 1>works dot com. M