Measuring Ice Thickness in Antarctica: NASA’s ICESat-2 Mission

Published Jan 8, 2019

We go behind the scenes with NASA glaciologists Dr. Kelly Brunt and Dr. Adam Greeley as they prepare for a data-collecting expedition around the South Pole.

In this episode
  • Kelly talks about measuring ice sheets to learn more about sea level rise
  • Kelly and Adam describe how to sleep comfortable in below 0 temperatures
  • Adam talks about the type of vehicle needed to cruise around Antarctica
  • Colleen asks Kelly and Adam about their chances of running into penguins
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Full transcript

Welcome to the Got Science podcast. I’m your host Colleen MacDonald. Today’s guests are roughly 9144 miles from our podcast headquarters here in Cambridge, MA. Care to guess where they are? Okay, I’ll tell you. They are at the South Pole or thereabouts on a really cool NASA mission. You’ll hear about their preparations for this extreme road trip. And stick around after the interview. Shreya Durvasula brings us another example of sidelining science.

Orbiting 308 miles above the Earth is one of many remote sensing satellites, designed and launched by NASA in September 2018 to detect the thickness of ice sheets at our planet’s poles. With a polar orbit every 94 minutes, it might even be traveling above your head right now, depending on where you are in the world and when you’re listening.

While I can barely see 20 feet in front of me without my glasses, the satellite known as ICESat-2 is measuring the height of sea ice to within an inch from outer space. This improved precision in polar ice data will help scientists run more accurate computer models, which means better predictions about sea level rise, and better understanding of how quickly polar ice sheets are melting.

But NASA knows that even when you have some of the world’s most sophisticated and sensitive technology at your disposal, it’s good to check your work. So it sent out my two guests today to make the long trek to Antarctica, where…as of this recording… they are currently collecting ground-based GPS data for comparison with what ICESat-2 is recording.

Before they left, they took some time to chat with me about their expedition. And I think you’ll hear from my voice how excited I was to talk about satellites, polar ice, and the complexities of traveling in Antarctica with real-life NASA scientists Dr. Kelly Brunt and Dr. Adam Greeley.

Dr. Brunt is an Associate Research Scientist in the Earth Sciences Division at NASA’s Goddard Space Flight. Dr. Greeley is a post-doctoral researcher with the same institution. They tag-teamed this interview to discuss the importance of ICESat-2 and its applications on Earth, penguin strutting, and where to get the best coffee at the South Pole.

Colleen: Kelly, Adam, thank you so much for joining me on the "Got Science?" podcast.

Kelly: Thanks for having us.

Adam: Yeah, thanks for having us.

Colleen: I want to start with process. Tell me, who comes up with the idea for the mission. Where does this all start before you even come up with the exciting, "We're going to Antarctica," stuff?

Kelly: So we're part of a satellite mission here at Nasa called ICESat-2. It's a laser altimeter. So from space, it's actually sending a laser down and precisely measuring the surface of the Earth. Basically the orbits of that satellite converge near the poles, and the data are most dense in that area. So one of our thoughts when we thought about, "How do you validate a satellite mission? How do you prove that this is the most accurate, the most precise laser altimeter ever, at that centimeter level," you go to where the data are most dense, and you collect a lot of ground-based data to directly compare against what the satellite's showing you. And it seems ludicrous, but a lot of us had had Antarctic experience and knew that while it was a little farfetched to go all the way to the pole and then drive away from the pole to go out to this dense area, it just made sense, and everybody was kind of on board like, "Hey. Let's do this. This is a good idea, from a statistical standpoint and from a mission standpoint."

Colleen: What is the ultimate goal of the mission? Is there a human application?

Kelly: A hundred percent. So ICESat's collecting the most accurate, the most precise elevation data of our ice sheets and other things. It's doing things for sea ice. It's doing things for trees and lakes and whatnot around the world. But one of its main missions is to be able to measure our ice sheets, then measure them again, look at the difference, and then make an assessment of how changes in our ice sheets are directly contributing to mean sea level rise. We're doing this at the centimeter scale, sub-centimeter scale. Why? Because a centimeter of change over a continent amounts to a lot of water getting dumped into the ocean.

Colleen: So when you arrive, you're going to fly to the pole, and that's where you'll get into the vehicle and start to go, start the mission. Do we call it a mission? Start the project? Do you call it a mission?

Kelly: Sure. I think we generally call it a project, but, you know, when I hear, "Mission," I think of the satellite. So that's the big mission, and this is just a project, kind of a part of that piece.

Colleen: Okay.

Colleen: So when you start the project, how many of you are on the vehicle?

Adam: There'll be about four of us. So Kelly and I are the two scientists that'll be on the traverse, and there will be two others with us. A mountaineer who serves sort of as a medic as well, making sure nobody rolls their ankle and that we're safe when we're out of the vehicles and walking around the ice, and then a mechanic as well who's kind of the clutch player that we like to have along for these rides. We'll have two vehicles. So obviously when you're a couple hundred kilometers from the nearest base, you want to make sure you got someone who can problem solve and fix any sort of mechanical issues we've got. But yeah, so between two vehicles, there'll be four of us.

Colleen: So just four of you? That's it?

Adam: Yeah.

Colleen: Wow. So what kind of resume does the mountaineer have to have? Who gets that type of job?

Adam: You know, it's not set-in-stone sort of, I think, list of requirements you must have. But I mean it's usually people who've done a lot of outdoor survival training work, people who have gone on either expeditions to Greenland or Antarctica, but also people who have done a lot of work in the mountains in Alaska, doing sort of expedition guide work, people who have extensive wilderness survival/medical experience and know how to handle these sort of things when they come up and can sort of get you back together and walking again.

Colleen: Sort of the MacGyver type? Or maybe that's more the mechanic. Just...

Adam: Well, a little bit of both.

Colleen: Yeah.

Adam: Because I mean you're in unexplored, really remote environment, and you don't have an ER right down the road that you can hop in an ambulance and go to. So a lot of this is sort of, you know, flying by the seat of your pants and making sure you can get where you need to go and what you need to do with what you have.

Kelly: Ultimately, I think all four players involved...I think when you're a geoscientist or an Earth scientist and you spend a lot of time in the field, one of the things you become is a good problem solver. Obviously the mechanic's a good problem solver, and the mountaineer who is carrying a couple medical kits, you know, but for the most part, the first aid that you have in the deep field is really just problem solving and thinking things through. So I think the whole key is, you know, everybody's a problem solver, and no matter what the issue is, everybody's contributing and kind of thinking about the task at hand and trying to solve it. So all these things complement each other really, really well.

Colleen: So Kelly, in your experience, how frequently does that happen that you're having to problem solve something significant?

Kelly: At least once a, you know, a project. The good ones are things that you solve on the order of hours and not days, or minutes as opposed to hours. Just there's things that just come up, and they're small things, you know. You hope it's not a medical thing, of course, but everything that I've seen has generally been, "Hey. We need something to replace this because it broke," and you start thinking, "What do we have around here that kind of serves the same sort of purpose as that," and fix it and move on. It's not, you know... It's fun, actually. Those are the really fun parts of field work, is, "Okay. What are we gonna do now?"

Adam: It’s kind of like those middle school and high school science projects where they’re like “We’re giving you an egg, some string, and some cardboard. Drop it from the ceiling and make sure the egg doesn’t break.” It’s exactly that kind of stuff sometimes.

Kelly: In my office, I have a little corner, and it's got all these little plastic bits, and I call it "The Wall of Improvisation," and it's things that I've implemented in the field, pictures, you know, of medical tape acting as a belt, meaning an automobile belt, plastic zip ties that have been Frankensteined back together to serve a purpose or whatever, but that's the fun part, I think, is problem solving the little things that come up.

Colleen: So how luxurious is the kitchen tent and the sleeping quarters?

Kelly: I love that you didn't touch on the bathroom tent.

Colleen: That's off limits.

Kelly: So I find the sleeping amazing. Everyone gets their own tent. I know it's about -20 C. I think that's -14 F.

Adam: It's a little warmer.

Kelly: Is it warmer than that?

Adam: It's closer to zero, I think.

Kelly: Is it? Ultimately I know that sounds cold.

Adam: It's cold.

Kelly: But... So what we have is our tents are set up on these sleds. So there's, you know, a couple centimeters plastic, then there's a pallet that's, you know, a few inches, then there's a plywood slab that's a few more inches, then the tent. We put about four Therm-a-Rests in there. So now you're stacked up high like "The Princess and the Pea." Ultimate...Then we have...What I do is take what we call a "-40 bag," so big, down, very, very thick sleeping bag. Probably just sitting there unrolled and everything, comes up to about your knee, just in the fill. Then you take that, and you shove it into another, a rectangular bag that's, you know, just a little bit more warmth. I sleep in my thermals, no socks, no hat, and I'm insanely comfortable. I loved it. I slept better there than in some of the stations for different reasons. Loved it. Kitchen's a little tight. Four people in an eight-by-eight kitchen setup is tight. I'm not gonna try to lipstick that up at all.

Colleen: What's the coffee like?

Kelly: The coffee is phenomenal because I wouldn't have it any other way.

Colleen: Good answer.

Adam: Yeah.

Kelly: I'm a huge fan of drip coffee. That's one thing. We'll do pour-overs. We did that last year. Which is unbelievably easy to clean up too. People come up with all these fancy whatevers to do coffee. No, forget that. Just get a funnel, a filter, and a handful of grounds, and get yourself hot water. It's amazing. So coffee is no drama. That's...

Colleen: I'm ready now. You can sign me up.

Colleen: So, were there ever indigenous people living in Antarctica?

Kelly: Indigenous people? I'm not totally sure. I think some of the first folks that really went down to this area, because it is getting extreme, were the whalers that were just kind of looking to extend and extend and extend to hunt. So to the best of my knowledge, no real indigenous people to Antarctica, although people have been doing their best to sort of live in the environment for well over 100 years.

Colleen: And what about wildlife? We've got... We know there are penguins, birds. Anything else there?

Kelly: Lots of seals. In the area where we'll be, that's probably the thing that we'll definitely see without even trying. They like to crawl into the cracks of the sea ice and get themselves up and sit in the sun. So we'll definitely see seals. Penguins, possibly. They sunk the... We're in the raw sea region, the southern raw sea region, and the sea ice there usually extends a little far out for the time of year that we'll be there. So the seals will come in and abuse the sea ice. So we'll get to see that. The penguins have really short legs and don't like to walk great distances on the sea ice. So we probably won't see too many of them at this time of year.

Colleen: Adam, anything you're particularly like, "I have to see a?"

Adam: Oh, man. I'd love to see a penguin. We'll see if that actually happens.

Colleen: Kelly, can you make sure he sees one?

Kelly: I'll do what I can.

Adam: And not a researcher dressed up in a penguin costume. Sorry.

Kelly: Okay. Shoot.

Adam: Doesn't count. Yeah. No. Definitely looking forward to that, but also the South Pole itself. Yeah, that'll be fun. Quite a sight to see.

Colleen: So is it marked?

Kelly: So the ice over the South Pole is actually moving. So what they've done is they've set up a ceremonial pole. So it looks like a barber pole, like something that you would see Santa and his deer surrounding, and they've got a bunch of flags that represent the 13 original signers of the Antarctic Treaty, which protects the continent for science purposes. So there's a ceremonial pole, you know, a shiny little globe on it. But the USGS used to come down every single year. I think they still do this. I know that somebody marks the South Pole, but they come out, and they actually officially survey where the pole is that year, and they put a marker on it, like a benchmark, a USGS benchmark, that's unique to the South Pole, unique to the year, usually what they call an Antarctic program participant or somebody that...a support contractor person that spent the winter there usually takes time to design it every year, which is really cool. So part of the display cases at South Pole have the sort of different markers through time, which is really cool. So they come out, and they actually survey the official South Pole. You can take a photo there, and then you can take a photo with the ceremonial pole where everybody tries to ski to or walk to or fly to.


Colleen: So when you get to the pole, is there any structure there? Is there a building? Is there a coffee shop? Is there a, you know, a gift store?

Kelly: Yeah. So let's talk about the stations in Antarctica in general. We'll land at McMurdo Station, which is the U.S. Antarctic Program's largest base in Antarctica. The National Science Foundation runs three full-time bases. This is the largest one. It has roughly, you know, 1000 beds. When we're there, the population is probably 700-800 people. So it's a very big base, and the reason is that it's supporting lots of deep field science around McMurdo, but it also supports the air stuff going to the pole. So it's really big. Then you get to South Pole. Depending on... There's about 200 beds at South Pole, but it's a full-on base. They land planes. They take care of all that. They support science, mostly space-type sciences at the pole. So lots of beds. Obviously you have to feed all those people. You have to provide the science support. You have to move cargo around. So it's a full, you know, very large operating station.

Then the U.S. also has a smaller one called Palmer Station, south of South America, and it's a bit smaller. I think there's about, you know, 100 beds there or so, and that's supporting a lot of biological sciences. You can't really fly in and out of there. You basically come in by boat. In my mind, it's one of the more remote stations because you can't just hop in and hop out easily. It's boat in, boat out. So that's the sort of make up and size of all the different stations. So at South Pole, when we land there, for the most part... You know, some of the stuff that they do out on the cargo yard, they'll have like a small building out there. But for the most part, it's one big building that supports everything. The science support, the lodging, the cafeteria, everything, medical, all the good stuff needed to not only run the station but run it throughout the whole year.

Colleen: So what type of vehicle is it that you use when you're out there? And I will say I did look on some of the webpages that you sent me, and it's really cool.

Kelly: So we drive... We'll have two setups. We'll have two vehicles. They're called Piston Bullies, and they are basically the same tracked vehicle that typically grooms your ski area. Basically the U.S. Antarctic Program came up with this idea that, "How about we have you drive these vehicles? But we'll have these sleds behind the vehicles. You'll set up your tents on the vehicle just once. You'll drive 750 kilometers for your traverse, or roughly 450 miles. You'll set your stuff up once. You'll drive the whole route, and then you'll take it down." So what we've done is minimize the amount of time it takes to, you know, set camp and then tear it down the next morning, which is great. But the description of these sleds, they're basically these 60-foot-long pieces of plastic with pallets set up on top of that, and on some of those pallets we'll have tents. Some of them will have generators and fuel and cooking tents and a bathroom tent, all the gear needed to survive and conduct all the science.

The sled itself is pretty cool. It's got a really low friction coefficient, and it allows you to tow about 1000 pounds of gear as if it was more like 100 pounds, and that helps a lot. You can imagine towing everything that we need for a two-week deep field traverse. It gets pretty heavy, and that's tough on the vehicle. So it's nice that we've got this setup that allows us to do that, which is pretty cool. And I'd highly recommend people looking for the videos of this sled in action because it was described to me. I thought, "No way is this gonna work." No one was more surprised than me.

Colleen: So just tell me. So a day in the life here, you get up in the morning. You get in. You're driving it. You're each driving. You're rotating driving. And then how does the day unfold?

Kelly: Yeah, we basically get up in the morning, have a great cup of coffee, whatever snack you need...

Adam: Step one.

Kelly: move forward. Kind of make sure the vehicles are up and ready and ready to go. That takes a little bit of... Start it up early, just like in the winter when you start your car a little bit earlier, and then you go off to work. Same thing here, but increase the time. Then we make sure all the science gear is running as well, and then we hit the road, and we start driving. We drive for about three hours. Then we stop, and we check the vehicles. We check the instruments. We take a little break. Get back in, drive about three hours, take a little break, check the stuff.

Colleen: In your drive time, the science is happening while you're driving. All the instruments, they're doing what they need to do to take measurements.

Kelly: That's exactly right. Basically all we're doing is continuously collecting GPS data. GPS, like what you have in your car, that's telling you where you're going. Basically in your car, you have about meters' level accuracy, you know, approximately, where you are in sort of lat-long space, to a handful of meters. When we collect these data and we post-process it after, say, two or three weeks' time after we return and let some time evolve, we can actually get down to the centimeter level of accuracy and precision. So we know exactly where we are in latitude and longitude, but even better, we know exactly how high we were off the ground. So we know that third component, that Z, or that elevation, and that's really what we're using to compare against the satellite. Ultimately, all we're doing is turning that GPS on in the morning, checking it routinely throughout the day, and for the most part, we were shutting it off at night for different reasons. Maybe this year, we'll leave it on throughout the evening, but that's all we're doing is basically making sure we're collecting that data all day long on both vehicles.

Colleen: So now you know the volume of the ice. Is that the important piece of what you’re trying to figure out?

Kelly: The satellite itself is just measuring the surface. So we get a lot of measurements very accurately and very precisely of the surface elevation of the ice sheet. Then we come back, and we make that measurement again over the exact same track. What you'll see is maybe a little difference in the elevation, a lowering in elevation. So you've got a lot of these tracks. You can sort of interpolate between the different tracks and get a total 2D area and then 3D volume loss of the ice. The key is mass. What does volume mean for mass? Because once you have the mass of what's been lost, then you can turn it into what we consider water equivalent. That's the hardest component. We can do the area. We can do the space. We can do the volume. But going to mass is really tough, and the reason it's tough is because you have to know about the density of the water, and we don't know that. We have great models and whatnot. We have sparse, what we call, NC2 data that gives us a sense of what's going on, but that's the hardest component, going from volume to mass, and that's where the real science of ICESat-2 takes place, and obviously it's the most meaningful part because that's what has a direct impact on folks around the world, is the sea-level component.

Colleen: Is this where... One of the graphics on one of the webpages, it showed the super-condensed, really dense ice.

Kelly: Yeah. Yeah.

Colleen: And the different layers. So that's sort of what you're talking about.

Kelly: Yep.

Colleen: Some of the ice is super dense. Then if it had... As it compresses, it's becoming more and more dense.

Kelly: Antarctica's a desert. So it's not like you're putting a lot into that equation all the time, you know, to pound that down and make it dense really quickly. It takes a lot of time to densify that. Consequently, you know, the density profile... So this is the top of the ice. This is the bottom of the ice. The density profile with increasing density going this way just kind of goes like this and then. You know? At a certain point, you're into what we actually call glacier ice, where it is hard as a freaking rock. But getting down to that can be hundreds of meters in the center of the Antarctic ice sheet. Takes a long time and a lot of weight and whatnot to, you know, cut off pore space and completely densify to get down to that glacier ice. The stuff above that, that's not fully cut off, that's not at its densest, is what we call firn, F-I-R-N. So we're basically just driving over the firn of the ice sheet. It's why we don't need cramp-ons.

Colleen: Let's fast-forward 5 years, 10 years from now. What is the importance of the data that you're collecting?

Kelly: So let's go to just year two because, again, this is ICESat-2. There was an ICESat. So we have measurements that are already in that 10 to 15-year timeline. We have measurements from ICESat that we can compare to ICESat-2 and make that time series type assessment that you're talking about. So that's what's exciting about this type of satellite, is it's continuing an amazing time series of ice sheet change. But yeah, you're right. As we extend things out farther into the future, ultimately, what we'll probably be looking at is not changing ice sheets, but also the rate of change. You know, if we start to extend the time series to such a length, we can get a better sense of not only how they're changing, but how fast they're changing, have things sped up. So right away, we'll have a great comparison to ICESat, but downstream we'll have just a much better sense of the time series and what it really means for changes in the polar regions.

Colleen: Well, Kelly, Adam, thank you so much for taking time out of your crazy last few days before you head to Antarctica. Yes, which is pretty amazing. It's been really great chatting with you. I hope that maybe I'll get to check in with you when you get back, maybe phone call or something to see how things went.

Kelly: That'd be great.

Adam: Yeah.

Kelly: Thank you so much for your interest in the project. It's been fun talking.

Sidelining Science

As a pollutant, mercury is right up there with the worst neurotoxins. It can lead to heart attacks, damage the nervous system, and cause problems with motor function. This is why you weren’t allowed to play with the liquid mercury that escaped when you broke your old-school thermometer. It’s why pregnant people, and people in general, are advised not to eat too much of certain kinds of fish, which absorb mercury and convert it to its most toxic form. And it’s why, in 2011, the Environmental Protection Agency announced its Mercury and Air Toxics Standard to limit the amount of mercury pollutants in our air.

This standard applies mostly to power plants, especially coal-burning power plants, which are the single largest manmade sources of mercury pollutants. For the past eight years, power plants have been complying, reducing mercury emissions by 81 percent, according to the Center for American Progress. And the EPA estimates that their compliance has saved about 17,000 lives each year.

If you’ve been listening to this podcast for a while, then you might be thinking I’m going to tell you that the EPA under President Trump has rescinded this standard. Not quite. In fact, they’ve done something more nefarious.

Under Acting Administrator Andrew Wheeler, the EPA quietly proposed at the end of 2018 that setting limits on mercury pollution is suddenly too expensive and no longer, quote, “appropriate and necessary,” end quote.

While the EPA can weigh costs to industry as one factor in setting rules like the Mercury and Air Toxics Standard, it does not have to be the decisive and over-riding factor. But when the cost to industry is greater than the benefit to the rest of us, it can make it harder to get the standard passed and then more vulnerable to legal challenge.

(I have a lot to say about the way we value profit over our health, but that can wait for another podcast.)

So by using some shady math and narrowing the scope of what can count as benefits, the EPA is now revising the its prior cost finding of the mercury rule to make it seem like the billions we’ve saved, and will save, in health and related expenses… aren’t actually a direct benefit of the rule.

They’re not trying to do away with the rule—at least, not yet. They’re trying to make it harder to impose rules like this in the first place. Which is really bad news for our air quality, and our health.

Janet McCabe was acting assistant administrator for the EPA’s office of Air and Radiation under President Obama. About the new proposal, McCabe told the website Vox, quote:

“If finalized, it will leave the mercury reduction requirements vulnerable to rollback or further legal attack, and it puts at risk years of progress to reduce exposure to a known neurotoxin that accumulates in the environment. The proposal also sets a very troubling precedent for how the EPA evaluates the impact of policy on public health.” End quote.

Happily, there’s something we can do to push back on this. Like all proposed rules, this one will be open for public comment for 60 days. UCS is watching and will give a heads-up when the comment period begins, to our members and to anyone who breathes air and might be interested in weighing in.

Stay tuned to, where we’ll link to the comment site when it opens, and where we also provide tips for everyone on how to write and submit an effective public comment on science-related issues.

EPA leadership might try to conceal their industry giveaways behind their manipulated cost-benefit analyses. But we know they’re just sidelining science.

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Sidelining Science: Shreya Durvasula
Editing and music: Brian Middleton
Research and writing: Pamela Worth
Executive producer: Rich Hayes
Host: Colleen MacDonald

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