Concluding what colleagues are calling an 'unprecedented' and exhaustive study, scientists on Thursday said they can report "definitively" that the ice sheets of both Antarctica and Greenland are, indeed, melting and that as global temperatures continue to soar this melting will lead to continued and drastic sea level increases.
The study, published by the journal Science, was performed by a large team of scientists and relied heavily on satellite imaging and years of field observations and argues that the extensiveness of the research should end long-running speculation about whether or not the ice sheets, in total, are losing mass.
"The estimates are the most reliable to date, and end 20 years of uncertainty of ice mass changes in Antarctica and Greenland," said study leader, Andrew Shepherd, of Leeds University. "There have been 30 different estimates of the sea level rise contribution of Greenland and Antarctica, ranging from an annual 2mm rise to a 0.4mm fall."
"We can state definitively that both Greenland and Antarctica are losing mass, and as [the] temperature goes up we are going to lose more ice."
By their estimates, the combined loss of ice is equivalent to 4 trillion tonnes and that the rate of melting has accelerated dramatically in more recent years. For instance, glaciers in Greenland are losing five times as much ice as it was in 1992, when the scientific community first began monitoring melting there.
The scientists put the attributable sea level increase of this specific melting at 11 millimeters, which is roughly one-fifth of the overall sea level rise that's taken place over this period.
Prof Richard Alley, of Penn State University, US, who was not involved in the study, told The Guardian: "This project is a spectacular achievement. The data will support essential testing of predictive models, and will lead to a better understanding of how sea level change may depend on the human decisions that influence global temperatures."
Kevin Trenberth, a senior scientist at the Boulder, Colorado-based National Center for Atmospheric Research, also not involved in the study, told National Geographic that the new study's "evidence is very compelling that global warming is playing a role in massive ice losses on land that contribute to sea level rise."
And National Geographic adds:
Rising seas would increase the risk of catastrophic flooding like that caused by Hurricane Sandy last month in New York and New Jersey. Environmental damage may include widespread erosion, contamination of aquifers and crops, and harm to marine life. And in the long term, rising seas may force hundreds of millions of people who live along the coast to abandon their homes.
By reconciling nearly two decades of often conflicting satellite data into one format—in other words, comparing apples to apples—the new study, published in the journal Science, made a more confident estimate of what's called ice sheet mass balance.
That refers to how much snow is deposited on an ice sheet versus how much is lost, either due to surface melting or ice breaking off glaciers.
For more palpable evidence of this rapid melt-off, a new documentary by Jeff Orlowski documents the real-time impact of global warming. "Chasing Ice" follows environmental photographer James Balog in his endeavor to create an "Extreme Ice Survey" by deploying time-lapse cameras across the brutal Arctic to capture a multi-year record of the world’s changing glaciers.