TOPICS > Science

Greenland Residents Detect Sea Changes

August 1, 2007 at 6:25 PM EDT

SPENCER MICHELS, NewsHour Correspondent: On Greenland’s west coast, residents of the town of Ilulissat — the name means “among the icebergs” — say they are already feeling some results of global warming. Climbing temperatures have affected the fishing and tourism industries, the lifeblood of the town’s 4,500 residents, sometimes for good, sometimes not.

OLE HANSEN HOF, Crane Operator: Some people say it’s OK because it’s warmer. Some people, they worry about the future, what might happen if the ocean is changed and the fish move out.

SPENCER MICHELS: Changing ocean temperatures mean some species of fish have left, but others have arrived from the south. Fishing now takes place year-round.

GREENLAND RESIDENT: What most people are afraid of, of fishermen, the cold water fish is disappearing, and their equipment is to fish cold water fish, so they’re going to have a big bill in the future if they want to change the gear.

SPENCER MICHELS: Dog-sledding, a major tourist activity, used to run through April. Now it’s limited to mid-winter. The implications of a warming climate go far beyond Ilulissat.

LARS KRISTIAN, Dock Worker: Because the water, it’s getting bigger and bigger, maybe the islands of the Atlantic, it’s getting drowned.

GREENLAND RESIDENT: You don’t have to be a scientist to see the changes. They’re big changes.

SPENCER MICHELS: But you do need to be a scientist to know just how big the changes are, how fast they’ll come, and what they mean. That’s why researchers are focusing on the Jakobshavn glacier, one of the world’s largest. It is so large that the icebergs that break off from it, a process called calving, are sometimes more than 40 stories high and three city blocks wide.

Glaciers are slowly moving rivers of ice. The Jakobshavn used to creep along at a pace that could truly be called glacial. Then, in 1997, it doubled its speed. It’s now moving more than the length of a football field each day, making it the world’s fastest glacier.

Its ice also thinned, and the calving front — the place where the icebergs break off — has retreated inland. When these icebergs reach the ocean and eventually melt, they raise sea level. But not enough is known scientifically about the reasons for these changes, or their impact, or how fast they will happen in the future, here and elsewhere.

Even a recent report from the Intergovernmental Panel on Climate Change, or the IPCC, couldn’t answer those questions. It said scientists simply did not have enough understanding of the melting process to make solid predictions of future sea level rise. That’s where researchers like New York University’s David Holland come in.

DAVID HOLLAND, Oceanographer, New York University: So the IPCC report, there are two headlines from it. One is that, in the next century, the air temperature is going to increase. That is solid science, totally credible, believable, good observations, good models.

The second headline is that sea level will rise between 20 and 60 centimeters. That’s totally incredible and unbelievable. That’s just a guess based on past behavior, how much sea level has risen in the past century. We cannot predict yet sea level change, and we’re stuck, and we’re stuck because we aren’t able to model processes that we have not observed.

"A poster child for global warming"

SPENCER MICHELS: To make those observations, oceanographer Holland and a team of scientists headed this summer to the Jakobshavn glacier, which, because of publicity it has received, has become a poster child for global warming.

DAVID HOLLAND: The fact of it is, is that the water and the depth of this fjord are not known, and yet this receives a lot of media attention as a reason why sea level will go up. So it's fundamental research, and basically the reason it's not measured is because it's just hard to get to.

SPENCER MICHELS: Just how hard Holland learned first-hand. His first night, he was stranded on the ice without half his gear after fog grounded his supply helicopter. The next day, the rest of his team was able to get just one more flight out, so they tried to cram their scientific instruments onto that aircraft. Then it was a 40-minute flight to their observation post. The scientists had just a week to do all their work. It was Holland's first visit to Greenland.

DAVID HOLLAND: It makes one breathless. It's just absolutely stunning. And to think, also, that this is a place where important consequences of climate change occur not in theory but in fact, these are the kinds of places we're talking about. If climate change is going to have an impact on populations in the future, it's what happens in these kind of places that matter.

SPENCER MICHELS: He has one basic question to answer.

DAVID HOLLAND: Are the ocean waters in this fjord warm enough to be causing the observed melting of this ice sheet?

SPENCER MICHELS: To find that out, Holland had to start pretty much from scratch.

DAVID HOLLAND: We really want to know about how the oceans and ice interact. For the fjord itself, the depth of the fjord is not known; the temperature of the water is not known. And you can go on from there, but not knowing those two things, nothing is known.

Monitoring the Glacier

SPENCER MICHELS: They assembled a rugged weather station, which, they hope, will send back data, including video, every day for many years. Meanwhile, at the University of New Hampshire, glaciologist Mark Fahnestock has been compiling data he collected this spring on the speed of the glaciers and how icebergs sheer off them.

MARK FAHNESTOCK, University of New Hampshire: Our motivation for studying this system is understanding how you tie big glaciers that are draining a tremendous amount of ice to changing conditions, both in the atmosphere and in the ocean. And we're trying to understand the rapid changes that the ice sheet has shown us so that we can have some idea what it will do in the future.

SPENCER MICHELS: He and his colleagues want to figure out what controls the speed of the glacier and the calving. Fahnestock set up time-lapse cameras to watch the changes in a compressed timeframe. This is a week's worth of motion of the Jakobshavn. This is a day in the life of the Earth's fastest glacier, continuous motion, more than 90 feet a day, fast for a glacier. But Fahnestock found the glacier actually moves in fits and starts.

MARK FAHNESTOCK: The scale here is that that's probably 150 meters high as it rolls over.

SPENCER MICHELS: Sometimes there are sudden, violent calving events, an hour-long series of crashes sounding like a freight train. Scientists took a series of still photos of the event, shown in this black frame.

MARK FAHNESTOCK: The thing to take from that and from the rapid changes in the Jakobshavn area, I think, is that the ice sheet is much more sensitive to fairly subtle changes than we would have predicted having not seen it.

SPENCER MICHELS: To get even more information, two scientists on Holland's team went out on Disko Bay, off Ilulissat, to observe where the icebergs ends up. Team member Ralf Bachmayer works with the National Research Council of Canada.

RALF BACHMAYER, National Research Council, Canada: Right now, we're entering this magnificent scene here, and we have to see where we can actually go and launch the CTD. Before that, all bets are open.

New ways to study glacial activity

SPENCER MICHELS: They were using an instrument called a CTD -- conductivity, temperature, depth -- to gather data about seawater, to see if its warmth could be what's triggering the glacier's melting and movement. Later that week, they were also able to deploy the glider, a kind of instrumented mini-submarine. They hope in future years to fly it underwater, taking measurements below the icebergs.

Flying over the glacier, they also managed to lower instruments from their helicopter. For the first time, they measured the fjord's depth: almost 900 yards. A CTD found deeper water two degrees warmer than right at the surface. And even with fresh water pouring in from the melting ice cap, they found water way back in the fjord where icebergs break off was salty, confirming Holland's suspicion that changes in the ocean may be what is causing the increased melting.

The research this year was just the beginning of what's designed as a 10-year project.

DAVID HOLLAND: What's really needed is a decade-long period of observation. We need to be able to correlate when the ocean is warm and cold in this fjord to when the ice is moving and not. So little snapshots are good, but the key observational thing is to get long term. We make the observations; we synthesize, understand the time series; and we will be able to make models that predict the future sea level, hopefully soon enough.

SPENCER MICHELS: Those models may have implications beyond Greenland.

MARK FAHNESTOCK: It may be that Greenland can teach us something that will allow us to better project forward what Antarctica may do in a warming climate, but we have to learn the story in Greenland first. We have a lot to learn.

SPENCER MICHELS: What they do learn over the next decade could help them predict how far sea levels could rise in the future and ultimately whether apocalyptic visions of massive coastal flooding are valid or not.