News / Science & Technology

Most Accurate Projection of Polar Ice Melt Produced to Date

Surface melt water rushes along the surface of the Greenland Ice Sheet through a supra-glacial stream channel. [Image courtesy of Ian Joughin]
Surface melt water rushes along the surface of the Greenland Ice Sheet through a supra-glacial stream channel. [Image courtesy of Ian Joughin]
Rosanne Skirble
Scientists have produced the clearest picture yet of a key indicator of global warming - the world’s shrinking polar ice sheets. The international study ends a 20-year dispute over how much ice is being lost or gained in Greenland and Antarctica.  

Measuring ice sheets is a tricky business.  Over the last two decades, dozens of studies on ice loss have come up with conflicting results.  Now, a global scientific team, reporting in the journal Science, has tried to set the record straight.

Different Assessment Methods Agree

Andrew Shepherd is a professor of Earth sciences at the University of Leeds in England and lead author of the study.  He says teams of experts from 25 international institutions, working at the same time and in the same locations, used different methods to gather ice-loss data, and then compared what they found. 

“When you look at the data, the ice sheets do have their own weather," he said. "From month to month we can see very different amounts of ice in Antarctica as compared to Greenland for example, and it becomes very important when you are comparing different estimates, that they’re made over the same time period and over the same geographical area.”
Polar Ice Melt
Polar Ice Melti
|| 0:00:00
...    
🔇
X

Shepherd says the results from the diverse research teams are two to three times more accurate than the most recent report from the Intergovernmental Panel on Climate Change (IPCC), the scientific body set up by the United Nations to regularly assess climate change. 

“The total amounts of ice lost from Greenland and on Antarctica all together since 1992, amounts to about 11 millimeters of global sea level rise,”  Shepherd said.  Of that 11 millimeters, he adds, two-thirds to three-quarters is from Greenland and the remainder is from Antarctica.

All Ice Sheets Losing Mass Except East Antarctica

While 11 millimeters might not seem like much, Shepherd says the combined rate of ice melt has increased over time.

“In the 1990s the ice sheets were losing about 0.3 millimeters of ice in terms of global sea level equivalent each year," he said. "Right now they are losing three times as much.”

The study finds that all ice sheets are losing mass - except for East Antarctica, where climate change is having a different effect. 

“In East Antarctica, "Shephard noted, "it’s a very large area and receives a very large amount of snowfall.  The signal of growth is consistent with that story.”

New Assessment Critical to Climate Modeling

Co-author Ian Joughin, a glaciologist at the University of Washington, says the information they’ve gathered for the study is critical to modeling global climate and predicting sea level rise.  He says even tiny changes in sea level, when added over an entire ocean, can have a substantial impact on storm surge and flooding forecasts for coastal and island communities. 

“It’s important to keep in mind," Joughin says, "that this is a snapshot of the current mass balance of the last two decades’ mass balance of the ice sheets.”  The expected warming, he predicts, will accelerate losses going further into the rest of the century.

Lead author Andrew Shepherd says he hopes the international teams will continue their ice-sheet surveys each year, and fill in some of the gaps left by less-frequent IPCC climate assessments. 

“We hope that this is an annual exercise where every team that has contributed to this assessment can do this on a more regular time than the IPCC reports, which are very useful assessments on a five- or six-year cycle, but in the intervening five or six years, it leaves people in the dark as to how things have changed,” he said.

The new ice-sheet data, reported in the journal Science, comes amid a flurry of new climate-change reports published in recent days, while international delegates in Doha, Qatar, discuss a new U.N. climate change treaty. Those talks conclude on December 7.

  • The midnight sun casts a golden glow on an iceberg and its reflection in Disko Bay, Greenland. Much of Greenland’s annual mass loss occurs through calving of icebergs such as this. (Photo courtesy Ian Joughin)
  • Each summer, streams channel much of the melt that is produced by the warmer temperatures along the Greenland Ice Sheet’s lower elevation margins. (Photo courtesy Ian Joughin)
  • Surface melt water rushes along the surface of the Greenland Ice Sheet through a supra-glacial stream channel. (Photo courtesy Ian Joughin)
  • Over the course of several years, turbulent water overflow from a large melt lake carved this 60-foot deep canyon. Note the people for scale. (Photo courtesy of Ian Joughin)
  • For several summers this deeply incised melt channel transported overflow from a large melt lake to a Moulin, a conduit that drains the water through many hundreds of feet to the ice sheet’s bed. (Photo courtesy Ian Joughin)
  • Large (~0.75 mile diameter) melt lake that is just one of the many supraglacial lakes that form on the ice sheet’s surface during the period of strong summer melt. (Photo courtesy Ian Joughin)
  • Moulin that drains surface meltwater through ice more than 3000 feet thick to reach base of the ice sheet, from where a subglacial drainage network ultimately routes it to the ocean. (Photo courtesy Ian Joughin)
  • Close-up of large crevasses produced by Pine Island Glacier’s rapidly stretching ice just above its grounding line (the transition from grounded to floating ice). (Photo courtesy of Ian Joughin)
  • Close-up of large crevasses produced by Pine Island Glacier’s rapidly stretching ice just above its grounding line (the transition from grounded to floating ice). (Photo courtesy Ian Joughin)
  • Curvi-linear crevasses in a region of complex ice flow on Pine Island Glacier, West Antarctica. (Photo courtesy Ian Joughin)
  • Seaward-looking view down Pine Island Glacier’s floating ice shelf, with a train of crevasses receding toward the horizon. (Photo courtesy Ian Joughin)
  • Summer clouds swirl in around the Staccato Peaks of Alexander Island, Antarctic Peninsula. High snowfall and strong weather gradients in this mountainous area make assessment of glacier mass balance particularly challenging. (Image courtesy of Hamish Pritchard, British Antarctic Survey)
  • A British Antarctic Survey two-man field camp next to The Obelisk on Alexander Island, Antarctic Peninsula. (Image courtesy of Hamish Pritchard, British Antarctic Survey)
  • The late summer sun sets over mountains and icebergs around Adelaide Island, Antarctic Peninsula, as twenty-four hour daylight gives way to the long polar night of winter. (Image courtesy of Hamish Pritchard, British Antarctic Survey)
  • Hamish Pritchard on a British Antarctic Survey expedition in the Herschel Heights, Alexander Island. Rock samples can tell us when these summits emerged from the retreating ice sheet. (Photo courtesy of Mike Brian)

You May Like

How to Safeguard Your Mobile Privacy

As the digital world becomes more mobile, so too do concerns about eroding privacy and increased hacking More

'Desert Dancer' Chronicles Iranian Underground Dance Troupe

Film by Richard Raymond is based on true story of Afshin Ghaffarian and his friends More

Obesity Poses Complex Problem

Professor warns of obesity’s worldwide health impact More

This forum has been closed.
Comment Sorting
Comments
     
by: Matsuda Seikoh from: Japan
November 30, 2012 7:45 PM
I don't make sense why the sea level will rise by melting ice.
We know a glass of water remains same level when melting ices in the glass. Why does the sea level rise ? Doesn't it same phenomena? Scientists find new physical phenomena on melting sea ice!
In Response

by: Mark from: Salt Lake City
December 01, 2012 10:54 AM
Sea levels of course don't rise when sea ice melts. Land based ice is a different matter altogether. Greenland has LAND BASED ice and much of Antartica ice is also land based.

by: TSUTAYA from: Daikanyama
November 30, 2012 7:27 PM
Scientists say the sea level is rising by ice melting, but are they measuring sea level worldwide continuously?
They are just calculating rise of sea water from the amount of melting ice and the area of sea.
I think the melting ice is changing to air not to sea water.

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Rolling Thunder Run Reveals Changed Attitudes Towards Vietnam Wari
X
Katherine Gypson
May 25, 2015 1:32 AM
For many US war veterans, the Memorial Day holiday is an opportunity to look back at a divisive conflict in the nation’s history and to remember those who did not make it home.
Video

Video Rolling Thunder Run Reveals Changed Attitudes Towards Vietnam War

For many US war veterans, the Memorial Day holiday is an opportunity to look back at a divisive conflict in the nation’s history and to remember those who did not make it home.
Video

Video Female American Soldiers: Healing Through Filmmaking

According to the United States Defense Department, there are more than 200-thousand women serving in the U.S. Armed Forces.  Like their male counterparts, females have experiences that can be very traumatic.  VOA's Bernard Shusman tells us about a program that is helping some American women in the military heal through filmmaking.
Video

Video Iowa Family's Sacrifice Shaped US Military Service for Generations

Few places in America have experienced war like Waterloo. This small town in the Midwest state of Iowa became famous during World War II not for what it accomplished, but what it lost. As VOA’s Kane Farabaugh reports, the legacy of one family’s sacrifice is still a reminder today of the real cost of war for all families on the homefront.
Video

Video On Film: How Dance Defies Iran's Political Oppression

'Desert Dancer' by filmmaker Richard Raymond is based on the true story of a group of young Iranians, who form an underground dance troupe in the Islamic Republic of Iran. This is the latest in a genre of films that focus on dance as a form of freedom of expression against political oppression and social injustice. VOA’s Penelope Poulou has more.
Video

Video Turkey's Ruling Party Trying to Lure Voters in Opposition Stronghold

Turkey’s AK (Justice and Development) Party is seeking a fourth successive general election victory, with the goal of securing two-thirds of the seats in Parliament to rewrite the constitution and change the country's parliamentary system into a presidential one. To achieve that, the party will need to win seats in opposition strongholds like the western city of Izmir. Dorian Jones reports.
Video

Video Millions Flock to Ethiopia Polls

Millions of Ethiopians cast their votes Sunday in the first national election since the 2012 death of longtime leader Meles Zenawi. Mr. Meles' party, the Ethiopian People's Revolutionary Democratic Front, is almost certain of victory again. VOA's Anita Powell reports from Addis Ababa.
Video

Video Scientists Testing Space Propulsion by Light

Can the sun - the heart of our solar system - power a spacecraft to the edge of our solar system? The answer may come from a just-launched small satellite designed to test the efficiency of solar sail propulsion. Once deployed, its large sail will catch the so-called solar wind and slowly reach what scientists hope to be substantial speed. VOA’s George Putic reports.
Video

Video FIFA Trains Somali Referees

As stability returns to the once lawless nation of Somalia, the world football governing body, FIFA, is helping to rebuild the country’s sport sector by training referees as well as its young footballers. Abdulaziz Billow has more from Mogadishu.
Video

Video With US Child Obesity Rates on the Rise, Program Promotes Health Eating

In its fifth year, FoodCorps puts more than 180 young Americans into 500 schools across the United States, where they focus on teaching students about nutrition, engaging them with hands-on activities, and improving their access to healthy foods whether in the cafeteria or the greater community. Aru Pande has more.
Video

Video Virginia Neighborhood Draws People to Nostalgic Main Street

In the U.S., people used to grow up in small towns with a main street lined by family-owned shops and restaurants. Today, however, many main streets are worn down and empty because shoppers have been lured away by shopping malls. But in the Del Ray neighborhood of Alexandria, Virginia, main street is thriving. VOA’s Deborah Block reports it has a nostalgic feel with its small restaurants and unique stores.

VOA Blogs