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Serious science

Ted Scambos talks about disintegrating ice shelves, climate change and returning to Antarctica

Ted Scambos is the lead scientist at Boulder, Colo.-based National Snow and Ice Data Center, which supports research into the frozen places of the world, from Antarctic glaciers to the dwindling sea ice cover over the Arctic. A veteran glaciologist who has made nine trips to Antarctica, Scambos specializes in remote sensing, using satellites to study ice dynamics and processes, particularly how climate change affects the cryosphere.

The Antarctic Sun sat down with Scambos at his office on the east campus of the University of Colorado-Boulder (CU-Boulder) in July to talk about climate change, ice shelves and his upcoming projects in the Antarctic.

Q: What got you involved in science, particularly polar research?

“I’ve always been interested in science,” Scambos said. He ticked off a number of heady disciplines that caught his interest at an early age, when scientific inquiry for most of us might include zapping ants with heat using a magnifying glass. In first grade, he wanted to study astronomy. By high school, interest had turned to chemistry. Planetary science — the astronaut dream of many young boys — also stirred his imagination.

After getting his master’s degree in geology, Scambos said he needed a break from academia. He worked for five years in the lucrative oil industry, at Philips Petroleum. “Did I like it? Was that what I wanted to do? It wasn’t,” he said. “Even though it was like falling off an economic cliff, I went back to grad school.”

He got his PhD in geochemistry from CU-Boulder, eventually landing a job as a remote sensing specialist with another well-known glaciologist and polar veteran, Robert Bindschadler at NASA’s Goddard Space Flight Center.

“Even though I kind of still looked at planetary science jobs, things went so well and they were so exciting and there’s so many big issues to solve in terms of polar science and climate change, it just took over. Looking back, it really played out perfectly for me, because what I really wanted to do all those years thinking about astronomy and planetary science was go to the moon or go to Mars or be in space.

“That’s something a tiny fraction of people involved in the field get to do, but in glaciology and Antarctic science, it’s much easier to go there and be a part of it and have experience of being out there in an extreme part of the world and trying to measure and understand it.

“That’s really the thing I like the best about what I do: It’s outdoors but it’s serious science, so you have the challenge of trying to live and work in the deep field, and the challenge of trying to bring the instrumentation down there and make it work and answer a question and find out something. That’s great. I love the field for that. I sit here at the computer and look at a lot of satellite images, but it’s essential that every once in a while we get out and actually see it with our own eyes and instruments.”

Q: You’re involved with the International Polar Year project with the Norwegians that will travel on tracked vehicles from South Pole to the Norway research facility, Troll Station, this coming season. The project is looking at how ice mass is changing due to climate change — whether ice loss at the edges of continent is being offset by more precipitation in its interior. How does this compare to your previous fieldwork?

“I’m committed to one of the longest field seasons that I’ve ever had. I’ve been there nine times to Antarctica, [but] I’ve never been to the South Pole or a traverse like this before. It’s a big commitment of time at this point. … I’m actually just going to enjoy it the whole way. I’m just going to have fun. It’s actually kind of liberating to not be the team leader and just be somebody who is helping as much as you can.”

Q: You reported the start of the Wilkins Ice Shelf disintegration in March 2008 of this year. Since then, the shelf has continued to deteriorate, even in winter. How unusual is the breakup, and what is its significance?

“It’s definitely been instructive to see what’s happened with the Wilkins … What’s happening now looks to be related to basal melt. Warm water from the ocean is actually somehow mixing up in the upper layer that usually caps it called the halocline. There’s fresh, cold water that surrounds the Antarctic. Sea ice floats in that. Snowfall plus sea ice melt keeps that layer fresh and light. Underneath it is saltier water, but it’s much warmer.

“That is typically 200 to 300 meters down below the surface in the Wilkins, so it touches the underside of the Wilkins ice plate but it doesn’t usually get up to the near surface. Now we’re seeing that in the last 10 or 15 [synthetic aperture radar] images it looks as though thin areas in the ice plate, even though it’s winter, are just sort of disappearing, thinning to the point of melting away and disaggregating the ice shelf.

“I’m going to stand by with what happened in the summer has to do with surface melting. The lesson is that there’s more than one way to lose an ice shelf. People have talked about basal thinning. There hasn’t been as end-to-end a model for how basal thinning really does the job on the ice shelf, but I think that’s emerging.

“By thinning the ice shelf and keeping the inflow constant you change the stresses that you’re asking the ice shelf to bear, the thinner plate of ice to bear, and it begins to fracture as a result of that. Those fractures lead to icebergs drifting away.”

Q: You recently received funding through the Cooperative Institute for Research in Environmental Sciences with Robert Massom of the Australian Antarctic Division and Antarctic Climate and Ecosystems Cooperative Research Centre to study ice shelf breakup. In particular, you’re looking more closely at the role of sea ice, or rather the lack of sea ice, plays in ice shelf collapse. Would you explain your hypothesis?

“Summer after summer, you have warming in the Antarctic Peninsula, and melt on the surface of ice shelves year after year, and then all of a sudden one year they go through this runaway disintegration. What triggers that? It’s like having dominoes all stacked up, but then you need something to tap the first domino and they all start falling apart. That’s the scenario I’m working on now.

“We’re going to try and take a look at sea ice extent in front of these ice shelves during these breakup events, during these retreat events. The thought is that ocean waves, especially long-period ocean waves, are getting in and breaking off the first front iceberg of the ice shelf and then that leads to a runaway situation because of this water perched on top of that shelf that wants to get into any crack that forms.”

Scambos explained that waves created from distant, powerful storms can travel thousands of kilometers. “These aren’t surfing waves,” he explained, but waves with barely discernible crests, or amplitude, but extremely long periods, or troughs, between the crests. Imagine a brick floating in a bathtub, he said, and then drop a pebble in the water. The pebble has no influence; the waves merely bounce off the brick. But slam your hand in the water and the subsequent waves causes the brick to move.

“The wave doesn’t bounce as much as it interacts with the brick. That’s what it takes. You need a wave the size of the [ice] shelf to actually flex the shelf.

“Sea ice acts as this great buffer. … When you get into the sea ice [on an icebreaker] within five, 10 kilometers, suddenly it’s like you’re in a building. Everybody comes out of their room. They’re not sick anymore. People you haven’t seen in a week are suddenly in the galley. That’s because the sea ice has dampened down the wave action considerably.”

Glaciologist Doug MacAyeal, of the University of Chicago, was the first to suggest this long-range effect by storms on icebergs, after he reported how a storm in the Gulf of Alaska rocked iceberg B-15 apart.

“That launched the whole idea that we needed to take a closer look,” Scambos said. “We thought about it and suspected before, but that really showed us there is some major connectivity to wave trains and large bergs that we had not completely explored.”

But the cause and effect relationship isn’t that simple. Seismic waves from the Indian Ocean tsunami in 2004 hit stable ice shelves along the coast of East Antarctica head on. None of the ice shelves responded to the blow.

“It has to be a combination of events,” Scambos said. “You have to have an ice shelf teetering on the brink, and then this rumpling at the edges sends it over in this runaway decay process.

“These things are responding slowly, but they get to the point where they suddenly break apart.”

Q: Will you ever be able to collect enough data to model and predict ice shelf collapse?

After a long pause: “Yes. It would be a really hazy, risky model.” Such a model, Scambos explained, would require a number of thresholds be met, such as temperature and sea ice extent, before one could predict a collapse. Even then, the best estimate would be a plus or minus of a decade.

“The ability to predict is based on a steady extrapolation of a really noisy year to year signal in terms of weather.”

Q: To continue on the theme of ice shelves, you have a pretty big IPY project coming up during the 2009-10 field season called LARISSA [for LARsen Ice Shelf System Antarctica], with an all-star team of scientists going down to the Antarctic Peninsula to look at the Larsen Ice Shelf area, where two of the three sub-shelves have disintegrated. What do you hope to learn and accomplish?

“The overarching goal is to examine every aspect of an ecosystem and glacial system evolving under a very rapidly warming climate as an analog, in this case, for the rest of Antarctica.

“The Antarctic system, in general, is snowfall high up on the plateau, great big glaciers that flow out, and usually there’s a huge ice shelf in the Antarctic system fronting these ice shelves.

“As you go through warming, that ice shelf can suddenly disappear, [causing] big changes to the ecosystem – benthic and surface – and big changes to the glaciers because you’ve lost the back stress that the ice shelf provides on this glacial outflow.

“The Larsen is a big enough system that it’s a realistic model of what’s going to happen to the Antarctic, but yet small enough so that the [R/V Nathaniel B.] Palmer can in one season study all aspects of it.”

Q: Few argue that the planet is undergoing a change in its climate. Global temperatures are rising, entire ecosystems are shifting such as in the Antarctic Peninsula, and the oceans are acidifying, threatening marine life on a broad scale. Yet there’s still the debate about whether these events are largely natural variability or the result of anthropogenic input. What convinced you that human activities are driving climate change?

“I think I was still on that fence – more in that sense of natural variability or is it really climate change – in the late 90s. By the time the Larsen B [ice shelf] came around [in 2002] that wasn’t quite the epiphany moment. It had already happened, but the Larsen B was pretty emphatic evidence that we were going to see severe changes and that things were happening now that had not occurred in the previous minor warmings on the Earth before.

“This time it’s different. An ice plate [Larsen B] that had been there for 10,000 years was disintegrating tells us that this is not like the Medieval Warm Period, not like the Climate Optimum …”

Scambos said data from ice cores drilled in Greenland and Antarctica first convinced him that humans were largely responsible for global climate change. He is particularly interested in seeing the results from the West Antarctic Ice Sheet drilling project, a three-year effort to extract an ice core 1.5 kilometers long.

“I’m hoping WAIS core gives us some details,” he said. Ice cores contain a wealth of information about past climate, a study called paleoclimatology. For instance, bubbles of gas trapped in the ice from hundreds of thousands of years ago can tell scientists about the climate then, which they can then extrapolate into the future.

“In other words, [we] use the big changes that have happened in the past to tell us the net result of what this [human] experiment will be for climate change. Models are really having trouble dealing with the complexity of the system. We’ve seen it in how fast the Arctic sea ice is disappearing.

The North Pole, he added, could be ice-free in five or 10 years. “Any day now,” he quipped. “We’re in the range where a hot summer could melt all of it away.”

NSF-funded research in this story: Ted Scambos, National Snow and Ice Data Center, Award No. 0732921 and Award No. 0538103

 
 
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Curator: Peter Rejcek, Antarctic Support Contract | NSF Official: Winifred Reuning, Division of Polar Programs