Episode 4 | Ancient Ice

Alok Jha talks to Dr Kelly Hogan, a Marine Geophysicist at the British Antarctic Survey to find out what studying the remains of ancient ice sheets in Antarctica can tell us about climate change and the future of the planet. 

Kelly works on research vessels around Antarctica, looking for clues about how ancient ice sheets flowed and eventually receded back towards land but also what caused the ice to shrink.

In addition to more than 10 trips to the Arctic, Kelly has been on 5 research cruises to Antarctica. Her most recent trips have been to study Thwaites Glacier. New research has revealed huge channels underneath the glacier, which funnel in warm ocean water towards it, and could speed up the melting of the glacier.

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Seafloor Mapping

This illustration shows the multibeam seabed sonar mapping process which Kelly and her colleagues use to collect data from the seafloor in Antarctica. The sonar images reveal the topography and show an ‘imprint’ of the Antarctic ice sheet once flowed.

Why does Antarctica matter to you?

"It's a pristine, amazing and beautiful environment that we as a planet have committed to protect. We have seen how much more ice is being lost now versus 30 years ago, and although everything appears quiet and still, it is responding quickly to what we're doing to the rest of the planet and that's what keeps my attention and efforts."

Kelly Hogan, 2021

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Episode 4 Transcript Ancient Ice

Alok Jha (00:02): Let me take you on a journey to the coldest place on earth and it's last and greatest wilderness on A Voyage to Antarctica. Welcome to A Voyage to Antarctica brought to you by the UK Antarctic Heritage Trust. I'm your host. Alok Jha. What can studying the remains of ancient ice sheets in Antarctica tell us about climate change and the future of the planet. Answering that question today will be Dr. Kelly Hogan, a Marine Geophysicist at the British Antarctic Survey. Kelly works on research vessels around Antarctica, looking for clues about how ancient ice sheets flowed, and eventually receded back towards the land. In addition to more than 10 trips to the Arctic, Kelly's been on five research cruises to Antarctica. Her most recent trips have been to study the Thwaites Glacier. New research there has revealed huge channels underneath the glacier, which funnel in warm ocean water.

Alok Jha (01:11): How did you come to become interested in Antarctica? How did your career take you there?

Kelly Hogan (01:19): I think the first thing that sort of pointed me in the direction of Antarctica in particular was during my undergraduate degree, which was in geology at Oxford. And there was a guest lecturer there, a guy called Gary Wilson and he had done field work, terrestrial field work, so on land field work in Antarctica, lived in a field camp, studied the rocks there, but also what the rocks meant in terms of what the climate was doing. So how cold it was and when it was, when it was warmer. And he showed us this sort of glimpse Antarctica and glimpse of the questions relating to how the climate behaves there, how it controls the ice, what the feedbacks are for the whole global system. And I just thought it was absolutely fascinating. And that was really the bug for me.

Alok Jha (02:07): Well, what was it about the stories you got told there? Was it the science itself or was it the sense of adventure and the idea that you would be having to go to somewhere very few people get to go to?

Kelly Hogan (02:21): Yeah, I think it's hard to pretend that the sense of adventure isn't a factor, but I think in terms of the science, what really caught me was that there was still quite a lot of unknown questions to answer for Antarctica. It's obviously quite a hard place to work it's very far away, it's very remote. It's hard to get to, it's hard to access the things that you want to study, because a lot of the things you might want to study are under several miles of ice or under several miles of ocean. So it's, it's quite tricky place to work, but the questions are big and so global and so important. So it sort of seemed like a place where we could still do a ton of work and really important work. And there was still a lot of questions to resolve.

Alok Jha (03:10): So tell me, what was the first time you went to Antarctica?

Kelly Hogan (03:14): The first time that I went to Antarctica was actually doing my PhD studies and it was in 2007 and I was asked to join a research cruise really as a, as an extra pair of hands to look after some of the geophysical instruments on board while they were serving. That was my first visit to Antarctica. We actually visited one of the big UK research bases, which is called Rothera research station on the Antarctic peninsula, so we actually got to get off the ship and land, and that's quite a big thing. If you work on ships, sometimes you can do whole cruises and never, never step onto the land or onto the continent at all that you're studying. And so that was really a phenomenal experience. And then we went off and did our work off shore there, which included using , a very early ROV, remotely operated vehicle, to send it down, to dive down to the sea floor and study lots of different things from geology to biology. So it was really a fascinating cruise.

Alok Jha (04:15): You are a Marine geophysicist. So tell us what one of those scientists does.

Kelly Hogan (04:22): Yes, as I said a bit a bit before, I study the sea floor around Antarctica, but what we, how we do that is to use, sound in sort of different guises that we omit from a ship and we send it down to the sea floor and then it is reflected back to us. And, you know, we use a variety of different frequencies and different instruments to, to study different things. One of the main things that I look at is the shape of the sea floor and how that's been sculpted and shaped by ice in the past. And how we do that is to send a sort of fan, if you can imagine a fan of sound going down to the sea floor and then coming back up to the ship and, and recorded, you record the time that it comes back up to the ship. And then as the ship moves along, you sort of map out these features on the sea floor, sort of in 3D because this fan is moving back and forth. You can imagine it like you are mowing the lawn with your lawn mower. So you're going up and down, up and down and sending these pulses of sound down to the sea floor, bring them back and then recording the depth down to the sea floor. So you eventually get this big 3D map of what the sea floor looks like.

Alok Jha (05:31): But instead of a lawn mower, you're using sound waves to sort of sweep across the sea floor. As you build up this three-dimensional map of the sea floor and understand what's down there, what is that telling you? How is that feeding into the sort of larger picture of the continent?

Kelly Hogan (05:54): Yeah, what it tells us is how ice flowed and moved around and behaved during what we call full glacial periods. So the last one was the last glacial maximum is about 20,000 years ago to about 10,000 years ago. And what happened then was that Antarctica grew out onto the sort of shallow sea floor around the continent. And the ice grew out from Antarctica and flowed over it. And so then after that cold period ended and the ice moved back towards the land, then, you know, these, the shapes that the ice left on the sea floor sort of expose, in sort of pristine condition on the sea floor. So we can use what we call glacier landforms. So these sculpted forms on the sea floor to tell us about things like how the ice moved, where it flowed, how fast it was moving, whether there was water there. And then also how quickly it retreated and whether it moved back because it got melted or because it was carving big icebergs or a combination. So it really can tell us lots of different things about how ice behaves by studying these sort of past records.

Alok Jha (07:04): And all of this is telling you about how the climate on the earth has changed over the course of hundreds of thousands, millions of years.

Kelly Hogan (07:13): Yes, that's right. I mean the sea floor around Antarctica and what I've just described tells us most about the most recent time that ice grew out over it, but you can look further off shore as well, and you can look and you can drill down into the piles of sea floor sediments. So just muds and sands and you can get a record of those going back through time and you can look for things like the last time they were these big, releases of icebergs from Antarctica, and they drop a very special kind of debris to the sea floor. And so you get these records of armadas of icebergs leaving Antarctica during, you know, when you have one of these big events when when ice is lost from Antarctica. So you can get these records over yes thousands to millions of years. If you go a little bit further off shore than right where I was just describing.

Alok Jha (08:05): Actually, that's a good question. How far back can you piece together the past using this method?

Kelly Hogan (08:11): Well, we, you can use various sea floor records to go all the way back to the first time there was ice on Antarctica and that's about 35 million years ago. So you can get these use these deep sea records to basically measure the amount of different oxygen isotope ratios that are caught up in some of the bugs that live in the ocean, and then they die and they fall down to the bottom of the sea floor. And the ratio of these different oxygen isotopes tells you also actually about the volume of ice that's on land. So you can go basically all the way back to the start of ice on Antarctica.

Alok Jha (08:59): It seems incredible to me that there was a time that there wasn't ice on Antarctica, I suppose this is the, this is the thing about human mental capacity to think about deep history, which is Antarctica for all of human history has basically been an ice locked, well full of ice, it's the forbidden continent and all those things, the idea that it might have been something completely different in the history of the earth and for most of the history of the earth is, is so strange to think.

Kelly Hogan (09:26): I think it's, I think it is quite hard for people to visualize and because what you're talking about is moving continents around from where they are now to totally different positions. You know, you, the reason that Antarctica didn't have ice before that was because it was joined up with south America and Africa. And, and so you, it, wasn't isolated by the ocean and couldn't get as cold as it is today. Um, so it's really quite hard for us to, to visualize, but I think, you know we're lucky to be able to go there and to study what's going on there. And colleagues of mine that I work with, they study these fossilized forests and they find evidence of these great big bivalves that used to live there in much warmer conditions. So we sort of see it with our eyes. We see the fossils and we see the record of those warmer times. And it is really fascinating.

Alok Jha (10:14): Can you take us to Antarctica and our minds, tell us what a typical day for you might be like when you're, when you're there in a season.

Kelly Hogan (10:25): So a typical day for me working on a ship. So I work on research ships when I'm in Antarctica and a typical day for me will be probably a 12 hour shift where I'm on and working for 12 hours. So I probably get up an hour before that and have breakfast in a canteen, a communal canteen with everyone else, and then start our shift. We'd have a handover session with the previous shift to tell us what they'd been doing and what the plans were and what the weather was looking like and what we were hoping to achieve for that day. And then during my shift, which would probably be sort of between four and six people on a shift, we could be doing some seafloor mapping in which case we have to monitor all the machines and fix any problems that come up and we start looking at the data and cleaning it and analyzing it and talking about it within the group. And then we also make plans for where are we going to take those sediments samples from the sea floor. If we were doing that, then we might be out on the deck, you know, all dressed up, you know, really wrapped up warm, putting these big coring devices down to the sea floor and bringing them back up again and taking out the material and processing it in the lab. So it can be quite varied but also quite hard work. And if you imagine doing 12 hour shifts, seven days on repeat, because you don't waste any days, you know, there's no weekends when you're working in Antarctica, you, you don't waste any of your time, you know, you keep going. So it does get tiring.

Alok Jha (12:01): It sounds tiring listening to that, especially given how cold it must be. And also if you're standing on deck for a period of time bringing up cause from the sea floor, I mean, that's going to be muddy, sort of slightly dirty work right? This is quite manual physical exertion going on.

Kelly Hogan (12:19): Yeah, it can be muddy and cold and wet and you know, where we were working for the past two seasons, at Thwaites Glacier in west Antarctica, we were outside in temperatures of minus 20. We were coring at night, so we were out on the deck it was actually dark at that time

Alok Jha (12:42): That does not sound like not fun at all...

Kelly Hogan (12:45): Well you say that, but then, when you're there, it's kind of a magical experience because you're in this place that no one has ever been to before. And you're collecting samples that no one has ever been able to get before. And you also know that at any time you can probably pop back into the ship and get a hot drink. So it's not the same as being on the ice itself, I'd say but it can be pretty tiring too.

Alok Jha (13:13): What's life on board, the ship like? You say you work seven days a week, but you must have some downtime otherwise you can't possibly continue for months and months on end working every single day, 12 hours like that.

Kelly Hogan (13:25): Well a typical research cruise is probably about six or seven weeks for somewhere sort of deeper dark Antarctica, where it takes a while to get there and a while to get back. So you probably only do the 12 hour shifts for maybe five weeks or something like that. With travel time on either end, I suppose, your downtime is your 12 hours off in between.

Alok Jha (13:46): In which you've got to sleep of course.

Kelly Hogan (13:46): There's, there's a gym on board, there's a sauna, there's a movie room, things like that.

Alok Jha (13:57): Now you're talking.

Kelly Hogan (14:01): The best ship that I've been on in terms of downtime actually was a Swedish icebreaker, the icebreaker Odin, and she's a really beautiful ship and they have two saunas on board and each one of those has a little lounge area outside. So you can take your cold beer and put it in the fridge, and then you can pop in the sauna at the end of your long day shift. And then you can come out and enjoy a cold beer. The Swedes know how to do things.

Alok Jha (14:26): Okay, now you're talking, that sounds more my kind of Antarctica expedition.

Alok Jha (14:50): There's that cliche that goes around isn't there, that we know less about the sea floor of the earth than we do about the surface of the moon. Is that true?

Kelly Hogan (14:59): I think that's true. And I think it probably extends to places like Mars as well. You know, we have, um, very, very high resolution, essentially satellite, datasets from Mars that tell us about the shape of the surface of Mars and people talk about where they can see evidence of water and, and that kind of thing there, but it's much harder to do when 70% of your planet is covered in, in water. You know, we don't have that kind of resolution of the sea floor. We have to, we still have to go out and make our measurements from ships to be able to make those 3D maps of the sea floor on earth. So, so we do know a lot, a lot less about, about that then certainly the moon or Mars, but we are getting there and there are some big global initiatives, actually things like, Seabed 2030, which is a global push to get all nations, to be mapping the sea floor whenever they can from all of their vessels. And to build up that picture of the sea floor.

Alok Jha (16:00): Your research is part of a suite of things that go on around Antarctica, around climate, through the research on climate, research of wildlife, physics research looking for neutrinos in the south pole, all sorts of stuff goes on, around and on the continent. I just want to know, could you just put your piece of it, the idea of understanding the sea floor in this way, how does that fit into this sort of history of scientific research on the continent?

Kelly Hogan (16:30): Since Scott's expedition, when they took scientists and explored and they were actually doing geological studies and making geological maps at that time. But the British Antarctic Survey has been sending geologists down to Antarctica since the 1950s or so. And, they were moving around on land and trying to get rock samples and trying to map the outcrops of the mountains, what the rocks they could see with their eyes. So if you think about where does mapping the sea floor fit into it, we really didn't have the tools to be able to do that really efficiently until sort of the early 1990s, when the sonars that are called multi-beam sonars that send this fan of sound down to the sea floor and back again, became more widespread in, in science vessels. So even though there is a big drive to collect this kind of data now, and it is really important to understand the sort of long-term record of what's gone on with ice in Antarctica, it's actually a fairly new science and the pace of technology and our technological advances is really helping with that. And probably we can talk more about autonomous vehicles and the future of that kind of science as well.

Alok Jha (17:50): Well, let's talk about that because you mentioned earlier ROVs these remote Remotely Operated Vehicles, which is one of the first things you had to look after when you went to Antarctica, in 2007. Just tell us where that's, how that technology has come along, because you know, the idea of measuring things in very harsh environments, like Antarctica has really been helped essentially by robots and with machines that can dive very deep without putting human life at risk.

Kelly Hogan (18:25): Yeah, we are entering basically a new technological era in terms of what we can do in Marine environments, in places like Antarctica and polar regions. I think I could just compare what we did in 2007. So the remotely operated vehicle that we had there with us is called ISIS, which is a bit of an unfortunate name now. But this vehicle was tethered to the ship. So it has a cable running back to the ship so you have to stay within a certain range and you are limited by the length of cable that there is, it was quite hard to independently locate the ROV. So it's quite hard to put a gyrocompass or an instrument on the ROV to know exactly where it is. So then it's quite hard to locate where you are actually doing your mapping and where you're working. There was a lot of technology that you need just to keep the ROV running and you need big lights, because there's no light under hundreds of meters of water. And so these ROVs had a lot of lights, a lot of cameras, and then you're trying to put science instruments on there as well. And now what we're looking at is being able to send things like AUV, so autonomous underwater vehicles. So they're not tethered to the ship, but there's no one driving them. You basically program it to go where you want it to go and then you put it into the water from the back deck of the ship and off it goes, and it runs its course. They have a lot of really amazing technology on board to avoid icebergs. And if they do see an obstacle coming up, they do little loops to avoid them and then try to come back on track. They have sort of different options of what to do if they run into too much trouble, they basically surface or come back to the start point, and all of these things, you have to think very carefully about that when you're in an environment with huge floating icebergs that have keels, so the bottom bit that points down into the water, that's sort of tens to hundreds of meters deep. But we're now able to send those off and they can go underneath these floating bits of ice where we can't get to on a ship. And they're very hard to access from the surface as well, very dangerous places to work if there's a lot of crevasses. So we are really entering a whole new technological era.

Alok Jha (21:45): And so what kinds of things are you finding out? I mean, we know you've described already that mapping the sea floor is useful to understand ancient climates, and that helps you to see where the ice has been. So in this sort of rapidly increasing data collection phase of this research using these autonomous robots, what kinds of things are you discovering? What kinds of discoveries are being enabled by it all?

Kelly Hogan (22:15): Yeah, although there is a big push to use these new technologies, we're also quite careful. They're very expensive, all of these bits of kit and so we're really targeting things that are really going to help drive our understanding forward of these environments. Maybe I can just give you an example from the big project that I'm involved in now, which is to study Thwaites Glacier in Antarctica, it's called the international Thwaites Glacier Collaboration and so we've been on two research cruises down to Thwaites Glacier in Western Antarctica to study this particular glacier because it's losing ice so rapidly and at an accelerated rate that people are very concerned about its future. What we've done with some of these autonomous vehicles is send them underneath the ice to places that we can't get to. And what we're trying to do with that is to measure and to understand where warm ocean water is getting underneath the ice and getting to where the ice rests on the sea floor. And it's doing its most melting because if you understand where that melting is happening and how warm that water is and how it flows and how it circulates, then you can put that into your sort of computer model. That's trying to do a prediction for how it will behave in the future. The other big thing that our project is looking at are to make these sort of longer term records of change for Thwaites. So we know from satellite datasets, how Thwaites has behaved over the past sort of 30 or 40 years, but beyond that hundred year timescales, we don't really have a good record. We have no observations of what Thwaites was doing then so what we want to do is to use the geology of the sea floor in these records that we find just offshore from Thwaites Glacier to tell us how ice at Thwaites behaved in the past. So was it always chucking out lots of icebergs? Was it always being melted a lot by warm water? How has the warm water changed? How have the pathways of that warm water changed, understanding of all of those things?

Alok Jha (24:30): What can we learn about how our climate might change given the sort of stresses we're putting it under?

Kelly Hogan (24:41): Yeah, I think that's a really interesting question. I mean, I think that one really important thing that the geological record can give us is an idea of how the planet behaves when it's left to its own devices. So when it's naturally changing, due to things like the amount of solar insolation that we get due to the tilt of the earth, and things like that. So there's a natural variability in the Earth's climate that we can study from the rock record and from deep sea sediment, cores and things like that. But now we've, with what we're doing right now with greenhouse gas emissions and climate change, we're sort of perturbing that system. So what we can get from looking at geology is some idea of the boundary conditions of how quickly things can change or how slowly they change. And then we can compare that to the rates of change we're seeing neither in temperature or in the amount of ice lost, or the amount of melting in the Antarctica. And we can compare that to what would happen naturally, and we can really get a good handle on how that might, how ice might behave in the future.

Alok Jha (25:56): Can you tell us what the most surprising thing is that you found on the sea floor?

Kelly Hogan (26:01): I think probably the most surprising thing that we found in my particular research was when we were at Thwaites Glacier two years ago and it was a really crazy year because for the first time, during the living record we were able to get really quite close to Thwaites Glacier. So the sea ice that was there and has been there every year since man has been at Antarctica, had broken up and we were able to access an area that no one had ever been to before on a ship. And what the measurements that we made there showed us was that the sea was several hundred meters or a hundred to 700 meters deeper than we thought it was. And that was based on sort of using gravity models to make a model of the sea floor. And what that means is that if you think of a hundred meters, so the length of a football pitch deeper than you thought it was before, you think about how much more warm water might be able to get right up to the ice, it might be able to do that melting. Then that's a big error bar that we had. I think that was the first time that we've been able to map that area and to see exactly what the shape of the sea floor was underneath this really, really important glacier.

Alok Jha (27:23): Now all of this information that you're finding, all of these surprises, all of these things that feed in to our understanding of ancient sea floors. How do scientists also use this information to adapt and improve the models for current climate and future climate? Can we use that in that way too?

Kelly Hogan (27:47): Yes, we can use it in the models. I mean, I think you have to remember that science and climate science in particular and studying Antarctica is very, very joined up between the different disciplines, between the modelers and the glaciologists and the geologists and the biologists. You need to know pieces of everyone else's information to do your own work and to understand your own system because they're all connected. So there's two ways that you can use the sea floor information that I get in my work, in models. And the first is to use those new maps of the sea floor, of the depth of the sea floor as a boundary condition for the model. So if you were looking at how much water was getting into Thwaites Glacier, using the old imagery, or which is the water depth, you would obviously have a much different outcome versus the new, when you could get a lot more water when the sea floor is a lot deeper. The other way that we contribute and help models is by looking at the layers of sediment that we find on the sea floor. And that gives us records of how ice behaved in the past and how quickly some of these changes happened. And it's quite important to tell a modeler and a computer model of how ice behaves, how quickly things can happen if you don't have any upper bound or lower bound of how quickly, or how slowly some of these processes can happen, then the model could run away and be unrealistic. So we're providing those really important boundary conditions on how things might behave and also what the sea floor looks like. And those things are really important to get right before you even start doing the modeling.

Alok Jha (29:34): We always ask the same question to all our interviewees at the end, and I'll ask you as well. Why does Antarctica matter to you?

Kelly Hogan (29:44): Ah, that's such a good question. I was thinking about it this morning and I think my best answer is that it is such a pristine and amazing environment, all of it, the ice that's there, the ecosystems, the animals that live there, the ocean creatures that live there. It's this pristine, amazing, beautiful environment that we as a planet really have committed to protect, but it also really responds to what we are doing to the rest of the planet. What we've seen with how much more ice is being lost in Antarctica now versus 30 years ago, it responds and even though we think everything's quiet and still, and nothing happens faster, it really is responding to what we're doing to the rest of the planet. And I think that's what keeps my attention and my effort with Antarctica.