How we look kilometers below the Antarctic ice sheet | Dustin Schroeder
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I’m a radio glaciologist. That means that I use radar
to study glaciers and ice sheets. And like most glaciologists right now, I’m working on the problem of estimating how much the ice is going to contribute
to sea level rise in the future. So today, I want to talk to you about why it’s so hard to put good numbers
on sea level rise, and why I believe that by changing
the way we think about radar technology and earth-science education, we can get much better at it. When most scientists
talk about sea level rise, they show a plot like this. This is produced using ice sheet
and climate models. On the right, you can see
the range of sea level predicted by these models
over the next 100 years. For context, this is current sea level, and this is the sea level above which more than 4 million people
could be vulnerable to displacement. So in terms of planning, the uncertainty in this plot
is already large. However, beyond that, this plot comes
with the asterisk and the caveat, “… unless the West Antarctic
Ice Sheet collapses.” And in that case, we would be talking
about dramatically higher numbers. They’d literally be off the chart. And the reason we should take
that possibility seriously is that we know from the geologic
history of the Earth that there were periods in its history when sea level rose
much more quickly than today. And right now, we cannot rule out the possibility of that
happening in the future. So why can’t we say with confidence whether or not a significant portion
of a continent-scale ice sheet will or will not collapse? Well, in order to do that, we need models that we know include all of the processes,
conditions and physics that would be involved
in a collapse like that. And that’s hard to know, because those processes
and conditions are taking place beneath kilometers of ice, and satellites, like the one
that produced this image, are blind to observe them. In fact, we have much more comprehensive
observations of the surface of Mars than we do of what’s beneath
the Antarctic ice sheet. And this is even more challenging
in that we need these observations at a gigantic scale
in both space and time. In terms of space, this is a continent. And in the same way that in North America, the Rocky Mountains, Everglades
and Great Lakes regions are very distinct, so are the subsurface
regions of Antarctica. And in terms of time, we now know that ice sheets not only evolve over
the timescale of millennia and centuries, but they’re also changing
over the scale of years and days. So what we want is observations
beneath kilometers of ice at the scale of a continent, and we want them all the time. So how do we do this? Well, we’re not totally blind
to the subsurface. I said in the beginning
that I was a radio glaciologist, and the reason that that’s a thing is that airborne ice-penetrating radar
is the main tool we have to see inside of ice sheets. So most of the data used by my group
is collected by airplanes like this World War II-era DC-3, that actually fought
in the Battle of the Bulge. You can see the antennas
underneath the wing. These are used to transmit
radar signals down into the ice. And the echos that come back
contain information about what’s happening inside
and beneath the ice sheet. While this is happening, scientists and engineers
are on the airplane for eight hours at a stretch, making sure that the radar’s working. And I think this is actually
a misconception about this type of fieldwork, where people imagine
scientists peering out the window, contemplating the landscape,
its geologic context and the fate of the ice sheets. We actually had a guy from the BBC’s
“Frozen Planet” on one of these flights. And he spent, like, hours
videotaping us turn knobs. (Laughter) And I was actually watching the series
years later with my wife, and a scene like this came up,
and I commented on how beautiful it was. And she said, “Weren’t you
on that flight?” (Laughter) I said, “Yeah, but I was looking
at a computer screen.” (Laughter) So when you think
about this type of fieldwork, don’t think about images like this. Think about images like this. (Laughter) This is a radargram, which is
a vertical profile through the ice sheet, kind of like a slice of cake. The bright layer on the top
is the surface of the ice sheet, the bright layer on the bottom
is the bedrock of the continent itself, and the layers in between
are kind of like tree rings, in that they contain information
about the history of the ice sheet. And it’s amazing
that this works this well. The ground-penetrating
radars that are used to investigate infrastructures of roads
or detect land mines struggle to get through
a few meters of earth. And here we’re peering
through three kilometers of ice. And there are sophisticated, interesting,
electromagnetic reasons for that, but let’s say for now that ice
is basically the perfect target for radar, and radar is basically
the perfect tool to study ice sheets. These are the flight lines of most of the modern airborne
radar-sounding profiles collected over Antarctica. This is the result
of heroic efforts over decades by teams from a variety of countries
and international collaborations. And when you put those together,
you get an image like this, which is what the continent
of Antarctica would look like without all the ice on top. And you can really see the diversity
of the continent in an image like this. The red features
are volcanoes or mountains; the areas that are blue
would be open ocean if the ice sheet was removed. This is that giant spatial scale. However, all of this
that took decades to produce is just one snapshot of the subsurface. It does not give us any indication
of how the ice sheet is changing in time. Now, we’re working on that,
because it turns out that the very first radar observations
of Antarctica were collected using 35 millimeter optical film. And there were thousands
of reels of this film in the archives of the museum
of the Scott Polar Research Institute at the University of Cambridge. So last summer, I took
a state-of-the-art film scanner that was developed for digitizing
Hollywood films and remastering them, and two art historians, and we went over to England,
put on some gloves and archived and digitized
all of that film. So that produced two million
high-resolution images that my group is now working
on analyzing and processing for comparing with contemporary
conditions in the ice sheet. And, actually, that scanner —
I found out about it from an archivist at the Academy
of Motion Picture Arts and Sciences. So I’d like to thank the Academy — (Laughter) for making this possible. (Laughter) And as amazing as it is that we can look at what was happening
under the ice sheet 50 years ago, this is still just one more snapshot. It doesn’t give us observations of the variation at the annual
or seasonal scale, that we know matters. There’s some progress here, too. There are these recent ground-based
radar systems that stay in one spot. So you take these radars
and put them on the ice sheet and you bury a cache of car batteries. And you leave them out there
for months or years at a time, and they send a pulse down
into the ice sheet every so many minutes or hours. So this gives you
continuous observation in time — but at one spot. So if you compare that imaging to the 2-D
pictures provided by the airplane, this is just one vertical line. And this is pretty much
where we are as a field right now. We can choose between
good spatial coverage with airborne radar sounding and good temporal coverage in one spot
with ground-based sounding. But neither gives us what we really want: both at the same time. And if we’re going to do that, we’re going to need totally new ways
of observing the ice sheet. And ideally, those should be
extremely low-cost so that we can take lots
of measurements from lots of sensors. Well, for existing radar systems, the biggest driver of cost
is the power required to transmit the radar signal itself. So it’d be great if we were able
to use existing radio systems or radio signals
that are in the environment. And fortunately, the entire field
of radio astronomy is built on the fact that there
are bright radio signals in the sky. And a really bright one is our sun. So, actually, one of the most exciting
things my group is doing right now is trying to use the radio emissions
from the sun as a type of radar signal. This is one of our field tests at Big Sur. That PVC pipe ziggurat is an antenna stand
some undergrads in my lab built. And the idea here
is that we stay out at Big Sur, and we watch the sunset
in radio frequencies, and we try and detect the reflection
of the sun off the surface of the ocean. Now, I know you’re thinking,
“There are no glaciers at Big Sur.” (Laughter) And that’s true. (Laughter) But it turns out that detecting
the reflection of the sun off the surface of the ocean and detecting the reflection
off the bottom of an ice sheet are extremely geophysically similar. And if this works, we should be able to apply the same
measurement principle in Antarctica. And this is not
as far-fetched as it seems. The seismic industry has gone through
a similar technique-development exercise, where they were able to move
from detonating dynamite as a source, to using ambient seismic noise
in the environment. And defense radars use TV signals
and radio signals all the time, so they don’t have to transmit
a signal of radar and give away their position. So what I’m saying is,
this might really work. And if it does, we’re going to need
extremely low-cost sensors so we can deploy networks of hundreds
or thousands of these on an ice sheet to do imaging. And that’s where the technological stars
have really aligned to help us. Those earlier radar systems I talked about were developed by experienced
engineers over the course of years at national facilities with expensive specialized equipment. But the recent developments
in software-defined radio, rapid fabrication and the maker movement, make it so that it’s possible
for a team of teenagers working in my lab over the course
of a handful of months to build a prototype radar. OK, they’re not any teenagers,
they’re Stanford undergrads, but the point holds — (Laughter) that these enabling technologies
are letting us break down the barrier between engineers who build instruments
and scientists that use them. And by teaching engineering students
to think like earth scientists and earth-science students
who can think like engineers, my lab is building an environment in which
we can build custom radar sensors for each problem at hand, that are optimized for low cost
and high performance for that problem. And that’s going to totally change
the way we observe ice sheets. Look, the sea level problem and the role
of the cryosphere in sea level rise is extremely important and will affect the entire world. But that is not why I work on it. I work on it for the opportunity
to teach and mentor extremely brilliant students, because I deeply believe
that teams of hypertalented, hyperdriven, hyperpassionate young people can solve most of the challenges
facing the world, and that providing the observations
required to estimate sea level rise is just one of the many such problems
they can and will solve. Thank you. (Applause)

29 thoughts on “How we look kilometers below the Antarctic ice sheet | Dustin Schroeder

  1. I plan on sharing this with my friends. We have been watching an anime series called "A Place Further Than the Universe" in English separately. It has been an interesting series about a group of high school girls trying to find their path in life by going to Antarctica with an expedition.

  2. What they're doing beneath the ice sheet is studying how radio waves impact water. How is this all that different than what wifi and cell towers do to humans, 70% water?

    No research has been published on what 5G cell towers do to humans and I have a feeling this is somehow connected.

  3. This guy is one of the most reasonable-sounding climate scientists I've seen on TED. He's like the know-how of Bill Gates with a bit of the Steve Jobs charisma.

  4. Listen to the voice of the Noble Qur'an
    Surah: Al Mulk Verse:3-4
    [And] who created seven heavens in layers. You do not see in the creation of the Most Merciful any inconsistency. So return [your] vision [to the sky]; do you see any breaks?
    Then return [your] vision twice again. [Your] vision will return to you humbled while it is fatigued.
    Surah: Ar Rum Verse:41
    Corruption has appeared throughout the land and sea by [reason of] what the hands of people have earned so He may let them taste part of [the consequence of] what they have done that perhaps they will return [to righteousness].
    Surah: Al Luqman Verse:29
    Do you not see that Allah causes the night to enter the day and causes the day to enter the night and has subjected the sun and the moon, each running [its course] for a specified term, and that Allah, with whatever you do, is Acquainted?
    Surah: Ahd Dhariyat Verse:56
    And I did not create the jinn and mankind except to worship Me.
    Surah: Al Baqarah Verse:23
    And if you are in doubt about what We have sent down upon Our Servant [Muhammad], then produce a surah the like thereof and call upon your witnesses other than Allah, if you should be truthful.

  5. Didn't global sea levels rise by a few HUNDRED meters at the end of the last last age? Possibly due to glacial lakes suddenly draining. Anyone know if research on that is going anywhere?

  6. This could have been a bait-and-switch TED talk where Schroeder talks about radar but uses it as bait to give a Climate Change sermon.

    it was not. Well done and a thumbs up.

  7. Wow i didn't expect this video to be THIS interesting, but it was. I like how you can hear from his voice the PASSION and DRIVE and EXCITEMENT that the man has for this thing.

  8. The weird thing about this show is, I know how it works only based on what he told us for 11 minutes 11 seconds.
    He is a great at giving presentation

  9. well, as far as i know, the melting of the arctic ice sheet is not even close to being an important factor when looking at the rising sea level. Isn´t it weird that they totally forgot to mention that the decisive fact for sea level rise is the expansion of water due to heating, or should i say because there is no chance for cooling down again (therefor shrinking) because the environment is to warm.

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