Nav: Home

Study finds ice isn't being lost from Greenland's interior

May 04, 2016

Scientists studying data from the top of the Greenland ice sheet have discovered that during winter in the center of the world's largest island, temperature inversions and other low-level atmospheric phenomena effectively isolate the ice surface from the atmosphere -- recycling water vapor and halting the loss or gain of ice.

A team of climate scientists made the surprising discovery from three years of data collected at Summit Camp, an arid, glaciated landscape 10,500 feet above sea level in the middle of the Greenland ice sheet.

"This is a place, unlike the rest of the ice sheet, where ice is accumulating," says Max Berkelhammer, assistant professor of earth and environmental sciences at the University of Illinois at Chicago. Berkelhammer is first author on the study, reported in Science Advances, an open-access online publication of the journal Science.

Near Greenland's coasts, Berkelhammer said, "it's relatively warm, and the ice melts faster and faster."

"But in the center of the ice sheet, it's 25 below zero Celsius (-13 F), so it's always freezing, even if it warms. It's a very rare occurrence to go above freezing," he said. The authors note that "despite rapid melting in the coastal regions of the ice sheet, a significant area -- approximately 40 percent -- rarely experiences surface melting."

Solid ice can be lost not only by melting into liquid water. Under certain conditions, it can vaporize by sublimation, a one-step transition from solid to gas. Such conditions exist at the high-altitude, dry, frigid, glacial surface of Greenland's interior.

"Sublimation is common there, unlike other places," Berkelhammer said. "We looked at the exchange of water between the ice sheet and the air above it through condensation, evaporation, and sublimation."

At Summit Camp, a 150-foot tower was used to draw air samples at various heights above the surface and pipe the air into a laboratory buried a few feet below the ice. Lasers analyzed the air for two different isotopes of oxygen in H2O, whose ratio indicates the temperature at which the water molecules became airborne.

"We noticed a specific process that was occurring, where low-level fog would form right above the surface of the ice sheet," Berkelhammer said. A fogbow -- a rainbow caused by fog -- often appeared.

"As ice sublimates from the surface, it forms a fog," he said. "As the particles get heavier and settle back to the surface, you get recycling, rather than dissipation that would remove ice."

In winter, 80 percent of the ice that would otherwise be lost is recycled, Berkelhammer said. "So it's an incredibly efficient process."

But many questions remain as to how this boundary-layer recycling contributes to models of climate change.

"We expected sublimation to increase with temperature, but we find no net loss" of ice over time, Berkelhammer said, again referring just to the interior of the ice mass. "You could say, if this process changes, you'd lose ice significantly faster. Or, if (recycling) becomes even more efficient, you would conserve even more ice mass.

"We can't predict," he said. "And we don't know from the ice-core records what the history is."

The next step, he said, is to run experiments to see how sublimation changes with temperature associated with past and future changes in atmospheric carbon dioxide levels, to see how recycling fits into climate models.

"If we want to model how the ice sheet is warming, we need to include everything we know," he said. "This is a new process to incorporate in models."

But Berkelhammer cautions against over-interpreting the recycling as good news for the ice sheet or the planet, as its overall effect is likely to be relatively minor.

"This is small potatoes compared to the calving that's going on along the coasts," he said. "Every time we go back to Greenland, the edge of the ice is farther away from the coast."
-end-
Funding for the research was provided by the National Science Foundation, the Cooperative Institute for Research in Environmental Sciences (CIRES), the National Oceanic and Atmospheric Administration (NOAA) Climate Program, and the Danish Council for Independent Research.

Co-authors on the Science Advance publication are David C. Noone of Oregon State University; Christopher Cox, David Schneider, Michael O'Neill and James W. C. White of the University of Colorado, Boulder; Hans-Christian Steen-Larsen of the University of Copenhagen; Adriana Bailey of the University of Washington; and Konrad Steffen of the Swiss Federal Institute for Forest, Snow and Landscape Research.

University of Illinois at Chicago

Related Ice Sheet Articles:

Thousands of meltwater lakes mapped on the east Antarctic ice sheet
The number of meltwater lakes on the surface of the East Antarctic Ice Sheet is more significant than previously thought, according to new research.
Researchers discover ice is sliding toward edges off Greenland Ice Sheet
They found that ice slides over the bedrock much more than previous theories predicted of how ice on the Greenland Ice Sheet moves.
A clearer picture of global ice sheet mass
Fluctuations in the masses of the world's largest ice sheets carry important consequences for future sea level rise, but understanding the complicated interplay of atmospheric conditions, snowfall input and melting processes has never been easy to measure due to the sheer size and remoteness inherent to glacial landscapes.
Researchers discover more than 50 lakes beneath the Greenland Ice Sheet
Researchers have discovered 56 previously uncharted subglacial lakes beneath the Greenland Ice Sheet bringing the total known number of lakes to 60.
Ice-sheet variability during the last ice age from the perspective of marine sediment
By using marine sediment cores from Northwestern Australia, a Japanese team led by National Institute of Polar Research (NIPR) and the University of Tokyo revealed that the global ice sheet during the last ice age had changed in shorter time scale than previously thought.
Novel hypothesis goes underground to predict future of Greenland ice sheet
The Greenland ice sheet melted a little more easily in the past than it does today because of geological changes, and most of Greenland's ice can be saved from melting if warming is controlled, says a team of Penn State researchers.
Greenland's southwest ice sheet particularly sensitive to warming
The ice fields of southwest Greenland are becoming particularly sensitive to a climate cycle called the North Atlantic Oscillation as global warming proceeds.
Antarctic ice sheet could suffer a one-two climate punch
Variations in the axial tilt of the Earth have significant implications for the rise and fall of the Antarctic Ice Sheet, the miles-deep blanket of ice that locks up huge volumes of water that, if melted, would dramatically elevate sea level and alter the world's coastlines.
The first impact crater found underneath the Greenland ice sheet
A 31-kilometer-wide impact crater underneath about a kilometer of the Hiawatha Glacier's ice is the first of its kind to be discovered in northwest Greenland, scientists report.
Moderate warming could melt East Antarctic Ice Sheet
Parts of the world's largest ice sheet would melt if Antarctic warming of just 2°C is sustained for millennia, according to international research.
More Ice Sheet News and Ice Sheet Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.