Dr. Ginny Catania and colleagues are studying glacial hydrology at remote sites near Swiss Camp in Greenland. After setting up GPS units to measure ice movement last summer, the team plans several 2011 field work expeditions to gather data. All photos: Matt Hoffman

Scientists have predicted that if Greenland’s glaciers melted, sea level could rise up to six meters, devastating coastal cities and having enormous impacts. Consequently, understanding the complex dynamics of the country’s glaciers—both coastal and inland—has become increasingly important.

Given the widely accepted evidence that Greenland loses more ice mass than it gains every year, some glaciologists have begun pursuing the question of what factors influence and expedite glacial melting.

Studying water and ice

Enter Dr. Ginny Catania, a glaciologist and polar adventurer with the Institute for Geophysics at The University of Texas at Austin (UT). Dr. Catania is the principal investigator on an NSF-supported project called “ROGUE: Real time observations of Greenland’s under-ice environment.

The project is collaborative across two US-based institutions—UT and Dartmouth College, NASA researchers and colleagues at ETH in Switzerland.

“Greenland is losing ice, and the fast moving glaciers are accelerating,” says Dr. Catania. “We are interested in what happens to land-terminating glaciers when surface melt water travels to the glacial bed. There is evidence that the melt lubricates the bed, and the glacier can speed up.”

Post-doctoral fellows install GPS units to measure glacial activity.

When that happens, the glacier moves from higher to lower elevations where warmer temperatures expedite melting.

Looking at the entire glacier, from surface to bed

Specifically, Dr. Catania and her team aim to examine the nature and cause of short-term ice velocity changes near Swiss Camp, Greenland. They will be studying the interactions between the ice sheet, the atmosphere, and the bed through an integrated observational approach that involves borehole geophysics, surface-based measurements, satellite data and modeling.

Following the flow

Want to find a moulin? Just follow the stream.

Their work will focus on the hydraulic system underneath the glacier. Taking precise measurements, the team aims to investigate how surface water travels to the bed of the glacier, causes it to slide and how this system evolves through the melt season.

As a result, the top of the ice may move at a different speed than the bottom of the ice, which at times is sliding on a water layer at the base of the ice sheet.

“We want to measure the amount of sliding at the base,” says Dr. Catania.

Planning and operations

After selecting 3 sites last summer, a small team will travel to Swiss Camp in May to set out GPS measuring devices on the glacier surface. Then, from June through August, researchers will drill a total of 18 boreholes at three different sites with differing ice thicknesses of 650 meters, 750 meters and 850 meters.

The team will place instruments near the base of the ice sheet to measure water pressure—or the amount of overlying water in the borehole column.  This water level will fluctuate over daily/seasonal/yearly time scales, says Dr. Catania.

“Monitoring the water levels over time allows us to understand how the water is moving under the ice sheet,” she says.

Understanding ice dynamics

In addition, the boreholes will allow scientists to measure how the ice deforms to determine how much of the surface speed (measured by GPS) is due to ice deformation.

By directly observing the basal processes, the team will develop a more precise understanding of the evolution of what happens when water from a glacier’s surface travels to its bed.

Moulins

Moulins like this one provide routes for surface water to travel to a glacier's bed.

Scientists already know the water descends through features known as moulins, which are naturally occurring and prevalent on glaciers. Dr. Catania’s team will drill near existing moulins this summer.

Not your average drill

The drilling itself is no easy feat. The drill is a high-pressure, hot-water drill that can quickly reach the base of the ice sheet in a day.

“There are lots of GPS on the ice sheet surface, but we don’t yet know how much of the glacier’s movement is due to sliding on the bed or how much is ice deforming,” says Dr. Catania. “We will be able to measure deformation, and we’ll measure sliding.”

A glacier’s surface speed can be different than the speed the ice moves at the base, where the glacier meets the ground.

The team will also measure water quality, testing for salinity to understand where the water in the boreholes comes from. Water that is closest to the glacial bed will be saltier. They also plan to send down cameras, which, if successful, will allow them a rare glimpse of the glacial bed.

Improved modeling

The data collected will be correlated to melt and surface water volume proxies based on remote sensing data, meteorological data available from surface-based weather stations and measured lake volume.

This research will be part of a growing movement to better understand how glaciers work, says Catania. By developing a better understanding of how water gets to a glacier bed and what impact that has on ice speed, the scientists will produce data that can help modelers better predict the causes and impacts of glacier melt.  —Rachel Walker

Comments (0) Feb 18 2011

An artist's rendering of the ICESat satellite. Credit: NASA

NASA’s Ice, Cloud and land Elevation satellite (ICESat), which for seven years gathered data about ice sheets and sea ice at Earth’s poles, was guided out of orbit and plunged into the Barents Sea on Aug. 30, the agency reported.

NASA launched ICESat in January 2003 as the first mission dedicated to specifically studying the polar regions using a space-based laser altimeter. It was intended to transmit data for only five years.  However, ICESat’s lasers lasted until February. Flight controllers started lowering its orbit in June until it reached 200 km (125 miles) above the Earth. At that point, its orbit naturally lowered until it mostly burned up on re-entry into the Earth’s atmosphere with the few remaining chunks landing in the Barents Sea.

The satellite has helped scientists better measure changes in the mass of the ice sheets in Antarctica and Greenland, sea ice thickness at both poles, vegetation height and the height of clouds and aerosols. In the Arctic, for example, researchers used ICESat to watch as thin, seasonal sea ice replaced thick, older sea ice. In Antarctica, scientists were able to identify the network of lakes underneath the ice sheet that actively drain or fill.

“ICESat has been a tremendous scientific success,” said Jay Zwally, ICESat’s project scientist at NASA’s Goddard Space Flight Center, in a statement on NASA’s website.  “It has provided detailed information on how the Earth’s polar ice masses are changing with climate warming, as needed for government policy decisions.”

NASA has begun designing ICESat-2, which it intends to launch in late 2015. In the meantime, the agency’s Operation Ice Bridge has been underway since last year to bridge the gap in polar data in between ICESat missions. Operation Ice Bridge uses NASA aircraft to target areas of rapid change at either pole to get 3-D views of ice sheets, ice shelves and sea ice. It’s the largest ever aircraft-based survey of Earth’s polar ice.

– Emily Stone

Comments (0) Sep 01 2010

Sometimes thinking outside the box means thinking inside the sphere.

At least that’s what the designers at New York City’s Studio les bêtes did in coming up with the concept for the Arctic Drifter, an enormous inflatable ball that can hold a crew inside and roll around the Arctic collecting data.

The Arctic Drifter’s exterior would be made of inflatable Hypalon airbags — a material similar to that used in rugged inflatable boats — so it could roam across ice, water or flat land in all sorts of weather. When fully inflated, the contraption would be 15 meters (50 feet) in diameter. An inner sphere that remains permanently upright would house a crew, electronics and, as the company’s website notes, a composting toilet.

The outside of the ball would be decked out with a network of visual sensors that would project the external environment onto the inner sphere’s walls in real time for the crew to see and navigate.

There’s no word on when, or if, the idea will become a reality. But if it seems too off-the-wall to be plausible, remember that NASA tested its Tumbleweed Rover, a 2-meter (6.5-foot) rolling, unmanned data collector, at Summit Station in 2003 in hopes that it will someday tumble over the surface of Mars.  —Emily Stone

Comments (0) Aug 26 2010

The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured this natural-color image of Petermann Glacier on August 5, 2010. The image was acquired almost 10 hours after the observation that first recorded the event. By the time Terra took this image, skies were less cloudy than they had been earlier in the day, and the oblong iceberg had broken free of the glacier and moved a short distance down the fjord. NASA image created by Jesse Allen and Robert Simmon. Caption by Holli Riebeek and Michon Scott.

An iceberg roughly four times the size of Manhattan is making its way toward the Arctic Ocean after calving off Greenland’s Petermann Glacier earlier this month.

The 251-square kilometer (97-square mile) behemoth broke off the Petermann in northwestern Greenland on Aug. 5, causing the glacier to lose about one-quarter of its 70-kilometer (40-mile) floating ice shelf, according to NASA. It’s the largest Arctic iceberg to form since 1962.

Researchers at the Byrd Polar Research Center at The Ohio State University said the chunk represents the largest single loss of ice ever recorded in Greenland. Jason Box, an associate professor of geography and atmospheric sciences, wrote in a blog post that the glacier retreated 15 km (9 miles) in that one event, which represents a new known minimum for the glacier.

Box and others studying the glacier have recorded its increasing disintegration since 2000. It’s retreated a total of 21 km (13 miles) in that time. The Aug. 5 break is three times larger than any previous ice loss in Greenland or elsewhere in the Arctic since at least 2000.

“While it is unreasonable to pin an individual cracking event of a glacier on Global Warming, even if enormous, the retreat of Petermann glacier is most certainly part of a pattern of global warming,” Box wrote.

— Emily Stone

Comments (1) Aug 19 2010

[youtube=http://www.youtube.com/watch?v=EP4ONFKZFAs]

For years, scientists thought that melted water beneath Greenland’s coastal glaciers such as the Jakobshavn and Helheim lubricated the giant sheets of ice above, accelerating their plunge into the ocean and contributing to loss of sea ice. Turns out, that was an over-simplified explanation, said Ian Howat, assistant professor of earth sciences at Ohio State University.

Speaking in a press conference Wednesday at the annual meeting of the American Geophysical Union (AGU), the NASA-funded, CPS-supported scientist explained that the subsurface dynamics beneath glaciers is significantly more complex than previously thought.

“In the science community it’s been accepted that basal lubrication due to increased melting and warming is responsible for accelerating glacial advance and breaking off,” said Howat. “We’re finding out that’s not true.”

A calving glacier drops huge ice chunks into the sea. Photo: Martyn Clark, National Snow and Ice Data Center

Specifically, a complex, subglacial “plumbing” system involving the ocean, meltwater, and ice evolves, which drives the glacial calving. In fact, early evidence from Howat’s research suggests that ocean changes have a greater impact on the rate at which outlet glaciers spill into the sea than does meltwater.

Much of the melt water comes from early summer hot temperatures, which melt the glacier’s surface. The water flows through cracks in the ice to the ground surface.

Ian Howet in the field. Photo: Ohio State University

In the early summer, the sudden influx of water overwhelms the subglacial drainage system, causing the water pressure to increase and the ice to lift off its bed and flow faster—up to 100 meters per year, he said. The water passageways quickly expand, however, and reduce the water pressure so that by mid-summer the glaciers flow slowly again.

Inland, this summertime boost in speed is very noticeable, since the glaciers are moving so slowly in general. But outlet glaciers along the coast, such as the Jakobshavn, are already flowing out to sea at rates as high as 10 kilometers per year — a rate too high to be caused by the meltwater.

“So you have this inland ice moving slowly, and you have these outlet glaciers moving 100 times faster. Those outlet glaciers are feeling a small acceleration from the meltwater, but overall the contribution is negligible,” Howat said.

His team looked for correlations between times of peak meltwater in the summer and times of sudden acceleration in outlet glaciers, and found none. So if meltwater is not responsible for rapidly moving outlet glaciers, what is? Howat suspects that the ocean is the cause.

Through computer modeling, he and his colleagues have determined that friction between the glacial walls and the fjords that surround them is probably what holds outlet glaciers in place, and sudden increases in ocean water temperature cause the outlet glaciers to speed up.

However, Howat said meltwater can have a dramatic effect on ice loss along the coast. It can expand within cracks to form stress fractures, or it can bubble out from under the base of the ice sheet and stir up the warmer ocean water. Both circumstances can cause large pieces of the glacier to break off, and the subsequent turbulence stirs up the warm ocean water, and can cause more ice to melt.

Comments (0) Dec 18 2009

Click on the image for a larger view. Credit: NASA/John Arvesen

At Palmer Station, Antarctica, NSF-funded US research program participants used their bright red parkas to send ground-to-air greetings to scientists and the flight crew aboard NASA’s DC-8 flying science laboratory as it flew over the station during Operation Ice Bridge. Operation Ice Bridge is a study of polar ice sheets, sea ice and glacial recession.

The missions help bridge the data gap between ICESat-I (which will likely end this year) and the launch of ICESat-II (around 2014). Satellite information provided by the ICESat program help scientists understand and monitor changes in the planet’s polar icescapes.

Operation Ice Bridge flew over Greenland  last April, as it has most years since 1991 (William Krabill, NASA Wallops, leads the arctic work).  You can learn more about the mission, and get in the plane with the NASA scientists, via the video posted to the Operation Ice Bridge Greenland page.   

Want more? Visit the Ice Bridge blog! 

Update: Our friend, the expeditionary artist Maria Coryell-Martin, writes about Operation Ice Bridge on her blog. Her father, Seelye Martin (U Washington), is conducting research on the flying laboratory. “When I was young, he embarked on several cruises to the Arctic and shared stories of the ice, animals, and darkness” she recalls. “I remember talking through radio-patch phone calls and at home, his two large parkas fill the hall closet.” Maria says her interest in painting ice springs largely from her father. View her work on her Web site.

Comments (0) Nov 12 2009