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:

Collapse of the European ice sheet caused chaos
Scientists have reconstructed in detail the collapse of the Eurasian ice sheet at the end of the last ice age.
Oversized landforms discovered beneath the Antarctic ice sheet
A team of scientists led by the Université libre de Bruxelles (ULB, Belgium) and the Bavarian Academy of Sciences (Germany) have now discovered an active hydrological system of water conduits and sediment ridges below the Antarctic ice sheet.
Climate change clues revealed by ice sheet collapse
The rapid decline of ancient ice sheets could help scientists predict the impact of modern-day climate and sea-level change, according to research by the universities of Stirling in Scotland and Tromsø in Norway.
Last remnant of North American ice sheet on track to vanish
The last piece of the ice sheet that once blanketed much of North America is doomed to disappear in the next several centuries, says a new study by researchers at Simon Fraser University in British Columbia and the University of Colorado Boulder.
Mysterious 'crater' on Antarctica indication of vulnerable ice sheet
The East Antarctic ice sheet is more vulnerable than expected, due to a strong wind that brings warm air and blows away the snow.
New study shows impact of Antarctic Ice Sheet on climate change
An international team of researchers has concluded that the Antarctic Ice Sheet actually plays a major role in regional and global climate variability -- a discovery that may also help explain why sea ice in the Southern Hemisphere has been increasing despite the warming of the rest of the Earth.
East Greenland ice sheet has responded to climate change over the last 7.5 million
Using marine sediment cores containing isotopes of aluminum and beryllium, a group of international researchers has discovered that East Greenland experienced deep, ongoing glacial erosion over the past 7.5 million years.
Historic shrinking of Antarctic Ice Sheet linked to CO2 spike
Twenty-three million years ago, the Antarctic Ice Sheet began to shrink, going from an expanse larger than today's to one about half its modern size.
Tracking the amount of sea ice from the Greenland ice sheet
The Greenland ice sheet records information about Arctic climate going back more than 120.000 years.
This week from AGU: Greenland's thawing ice sheet, Nepal's landslides, and more
This week from AGU are papers on Greenland's thawing ice sheet, Nepal's landslides, and four more research spotlights.

Related Ice Sheet Reading:

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

Setbacks
Failure can feel lonely and final. But can we learn from failure, even reframe it, to feel more like a temporary setback? This hour, TED speakers on changing a crushing defeat into a stepping stone. Guests include entrepreneur Leticia Gasca, psychology professor Alison Ledgerwood, astronomer Phil Plait, former professional athlete Charly Haversat, and UPS training manager Jon Bowers.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".