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[Aircraft noise, music]

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Alex Gardner: My interest in glaciers

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comes from the sheer size of these things and 

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how much they’re able to change on human timescales.

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[waterfall noise] And so the amount of mass and energy being transferred

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by glaciers around the globe is tremendous,

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and it’s an absolutely fascinating thing to study from space.

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[waterfall noise builds, intro music kicks in]

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Narrator: Mountain glaciers are some of the most charismatic parts 

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cryosphere. Some might cling to the edges of cliffs 

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[music rises] at higher elevations, then lay bare and flat in a broad plain,

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looking cracked and weathered like elephant skin, before tumbling 

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thousands of feet toward the sea, and terminating in a dramatic 

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calving front. They’re like motion frozen in time - [iceberg calves]

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until they aren't. They tell a story about

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the distant past, and yet are incredibly responsive to the present. 

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You can understand why they’d be captivating to all of us, 

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and especially cryospheric scientists.

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Meet Alex Gardner, a cryospheric scientist at NASA’s

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Jet Propulsion Laboratory, who is going to help break down what a classic 

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west coast North American glacier might look like, where high amounts of snow

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dump on to the mountains. Gardner: And at higher elevations,

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there’s melt in summer, but not enough melt to get rid of all that snow. So that snow

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 it compacts, it turns into ice, and it starts to flow under its own weight.

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And it flows down the valleys. As it flows down the valleys, it actually 

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 it actually carves those valleys out and it makes them deeper. And so it creates these beautiful fjords

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where the ice flows down, it snakes out to the ocean 

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or to the lakes or further inland. And so that ice is flowing. It’s moving.

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[music builds] Narrator: Alex uses satellite data to study large-scale changes 

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. But two thousand miles to the north, Chris Larsen 

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from the University of Alaska Fairbanks spends a lot of time studying 

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glaciers from the air. He’s been flying over Alaskan

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mountain glaciers for many years, most recently on a NASA-funded mission

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[water fall noise] called Operation IceBridge Alaska. He’s absolutely 

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enamored with his local rivers of ice. 

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Interviewer: And what do you love about mountain glaciers? Chris Larsen: Well, they're in mountains

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so they're really pretty! You couldn't ask for a better way to experience 

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Alaska on a large scale than to go flying around for campaign after campaign 

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and to look at all the mountains in Alaska -- truly infinite.

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You just feel like you'll never see the end of them, and you don't want to.

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Narrator: But Chris doesn’t spend weeks away from home

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and family for the views. Chris and his colleagues at NASA want to answer 

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some pretty big questions by learning more about Alaskan glaciers

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and how they tick. Larsen: You know, why does NASA care about these?

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Well, they actually disproportionately contribute a large amount to sea level rise. 

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Narrator: In the long run as the Earth warms due to climate change, 

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the big ice sheets and mighty outlet glaciers of Greenland and Antarctica

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stand to contribute the most to sea level rise, simply because

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the vast majority of the planet’s ice is stored there. But currently, 

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it’s the world’s smaller mountain glaciers in comparatively warmer places, 

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places like Alaska and Patagonia that are contributing about a third of all 

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inputs to sea level rise, even though they account for only 

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1% of the world’s ice. Larsen: It’s mostly due to them 

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them being dynamic. They have water at the bed, which allows them to slide 

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fast, and they react quickly to climate change

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and have higher velocities than their polar counterparts.

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Narrator: Back at JPL, Alex uses satellite measurements 

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of global ice and computer models to predict ultimately, 

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how much sea level rise we might see due to climate change. 

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But in the case of mountain glaciers, we also care about the local impacts 

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of disappearing ice.Alex:When we think of changes in ice sheets, 

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we typically think of just what is the consequence for sea level rise 

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and the future evolution of the ice sheets. But glaciers in other regions, like high mountain Asia, 

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Alaska, the European Alps, these are places where

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these are places where changes in runoff matters to stream flows.

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In places like high mountain Asia, you have a lot of glaciers that feed the streams 

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that flow down to populated regions. And that runoff

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becomes significant for water resources, irrigation, and agriculture.  

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Narrator: Both Alex and Chris are passionate about 

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understanding how glaciers are changing and what it means for our planet’s future. 

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They’ll continue to use tools like elevation maps from the

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ICESat-2 satellite and detailed airborne measurements to monitor changing ice. 

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[music fades, teaser music builds]

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Peter Griffith: by the end of the tunnel you're about 100 feet under ground, and you're surrounded by

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bones sticking out of the wall from the steppe bison and the

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mastodons, there's sticks that are 40,000 years old

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there's grass that's still green, that's tens of thousands of years old.

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[music ends]