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TEDx Talks
Published: 2017-05-19
Source: https://www.youtube.com/watch?v=M12jvQcKsNQ
summer radio glaciologist that means that I use radar to study glaciers and ice sheets and like most glaciologist 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 about why it's so hard to put good numbers until runs and why I believe that by changing the way
we think about radar technology and %HESITATION science education we can get much better at it when most scientists talk about civil rights issue a plot like this is produced using a sheet and climate models on the right you can see the range of sea level predicted by these models over the next hundred years for context this is currently level and this is the sea level above
which more than four 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 Asterix and the county out unless the west Antarctica she collapses in that case we keep talking about dramatically higher numbers big literally be off the chart and the reason we should take that possibility seriously is
that we know from the G. logic history of the earth that there were periods in its history when she level rose much more quickly than today and right now we cannot rule out the possibility of that happening in the so why can't we say with confidence whether or not a significant portion of a continent scale a sheet will or will not collapse well in order to
do that we need models that we now include all of the processes conditions and physics that would be involved in a class like that and that's hard to know because those processes and conditions are taking place beneath Kalamata is a vice 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 then 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 reasons of Antarctica and in
terms of time we now know that a she's not only of all over the time scale of millennia in centuries but they're also changing over the scale of years and days so what we want his observations beneath kilometers of ice 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 that thing is that airborne ice penetrating radar is the main tool we have to see inside of my sheets so most of the data that's used by my group is collected by airplanes like this World War two era DC three that actually fought in the battle of the bulge you can see the
antennas underneath the wing using used to transmit radar signals down into the ice and the echoes that come back keeping information about what's happening inside and beneath the ice while this is happening scientists and engineers are on the airplane for eight hours at a stretch making sure that the radar's working I think this is actually a misconception about this type of field work for people imagine
scientist peering out the window contemplating the landscape is geologic context in the fate of the ice sheets are we actually had a guy from the B. B. C.'s frozen planet on one of these flights and you spent like hours videotaping us turn knobs on and I was actually watching the series years later with my wife and the scene like this came up I commented on how
beautiful it was and she said weren't you on that flight I said yeah but I was looking at a computer screen %HESITATION so so when you think about this type of field work don't think about images like this think about images like this this is a radar Graham which is a vertical profile through the eye she kind of like a slice of cake the bright layer
on the top of the surface of the ice sheet the bright layer on the bottom is the bedrock of the continent itself in the layers in between are kind of like tree rings in that they contain information about the history of the I and it's amazing that this works this well the ground penetrating radar as there used to investigate him for structures of road to detect
landmine struggle to get through a few meters ever in humor peering through three kilometers of ice and there 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 study I sheets so 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 in international collaborations we put those together you get an image like this which is what the continent of Antarctica would look like without all the I signed and you can really see the diversity of the continent and image like this the red features are volcanoes are mountains areas that are blue be open
ocean if the guy she 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 eye she is changing in time now we're working on that because it turns out that the very first radar observations of an article were collected using thirty five millimeter
optical film there were thousands of reels of this film in the archives of the museum of the Scott polar research institute 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 into art historians we went over to England put on some clothes and archived in digitized all of that film that
produced two million images high resolution images that my group is now working on analyzing and processing for comparing with contemporary conditions in the Irish I see that scanner I found out about it from an archivist at the academy of motion pictures arts and sciences so like to thank the academy for making this possible and as amazing as it is that we can look at what was
happening under the ice sheet fifty 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 to their these recent ground based radar systems stay in one spot to take these radars and you put them on the ice sheeting area cache of car batteries and you leave
them out there for months or years at a time when they sent a pulse down into the ice sheet every so many minutes or hours to this gives you continuous observation in time that one spot to compare that imaging to the to the pictures provided by the airplane decisions 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 tempor coverage in one spot with ground based sounding but neither give us what we really want both at the same time never going to do that we're gonna be totally new ways of observing the ice sheet and ideally those should be extremely low cost that we can take lots of measurements from lots of sense well
for existing radar systems biggest driver of cost is the power required to transmit the radar signal itself to be great if we were able to use existing radio systems radio signals that are in the environment unfortunately the entire field of radio astronomy built on the fact that there are bright radio signals in the sky and a really bright one is our son it's 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 is one of our field tested Big Sur that PVC pipe ziggurat is an antenna stance in undergrad to my lab built and the idea here is that we stay out at Big Sur we wash the sunset and radio frequencies and we
try detect the reflection of the sun off the surface of the ocean I know you're thinking there are no glaciers the Big Sur and that's true I but it turns out that testing the reflection of the sun officers is the ocean and protecting the reflection off the bottom of it a sheet are extremely geo physically similar and if this works we should be able to apply
the same measurement principle in Antarctica and is not as far fetched as it seems seismic industry has gone through a similar technique development exercise where they were able to move from detonating dynamite as a source using ambient seismic noise in the environment 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 I'm saying if this might really work and if it does we're getting it extremely low cost sensors we can apply networks of hundreds or thousands these on an ice you image and that's where the technological stars have really aligned to help us there's earlier radar systems I talked about we 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 in the maker movement make itself as possible for a team of teenagers working in my lab over the course of a handful of months to build a prototype radar okay they're not any teenagers to Stanford undergrads but the point holds fifties enabling technologies are leading us break down the barrier between engineers who build instruments scientists
to use them and by teaching engineering students to think like earth scientists earth science students who can think like engineers my lab is building an environment in which we can build custom radar sensors each problem at hand that are optimized low cost and high performance sport that problem ethnic totally changed the way we have survived select the sea level problem role of the crash here infield
arises extremely important and will affect the entire world but that is not why I work on it I worked on it for the opportunity to teach and mentor Greenlee brilliant students because I deeply believe that teams of hyper talented hypertrophy and hyperplasia that young people can solve most of the challenges facing the world and that providing the observations required estimates he level rice just one of
