Antarctica has a network of meltwater rivers that is much larger than previously thought
Antarctica is the most inhospitable place on Earth. Since the early 20th century, however, seasonal melting has produced temporary rivers and lakes, breaking up the monotonous line of ice.
And these bodies of water may not be as rare as scientists once thought. In a first-of-its-kind survey released Thursday, researchers were able to document meltwater drainage's unexpectedly large network of rivers, lakes, and ponds at the fringes of the Antarctic continent.
The news comes as concerns about melting ice at the poles are at an all-time high among climate scientists and concerned policymakers across the world. The extent of the drainage network has led some to worry that the meltwater may help weaken ice shelves in the Antarctic that are already hanging on by a thread, causing large chunks of ice to break off and contribute to rising sea levels. A companion study released the same day, however, presents evidence that the meltwater network might actually help redistribute water that would ordinarily pool in one place, keeping some ice shelves from falling apart prematurely.
"The new research paints an evolving and complex picture for meltwater systems in Antarctica," says Luke Trusel, a researcher who studies the impacts of climate change on Earth's ice sheets in Antarctica and Greenland, who was not involved in the study.
Dr. Trusel, a professor of Geology at Rowan University in Glassboro, N.J., tells The Christian Science Monitor in an email that meltwater rivers are similar to rivers you might expect to find anywhere else on the planet – they simply exist on top of ice sheets instead of land, transporting melted ice and snow, rather than rainwater, from one location to another.
"We've known that the margins around Antarctica experience surface melting today – in some places like the Antarctic Peninsula this melt has been quite intense," he adds. "We've seen that following intense melt episodes, the ice melt can pond in crevasses and form lakes that destabilize ice shelves in a process scientists call 'hydrofracture.' This has resulted in several large-scale and catastrophic ice shelf collapses in recent decades."
The recent survey found that the meltwater network in the Antarctic was extensive, consisting of drainage pools, rivers, waterfalls, and other features. Through this network, meltwater moves around the continent, possibly staving off hydrofracture in some areas. It is also possible, however, that meltwater could move to weaker points in an ice shelf, triggering collapses that might not happen otherwise.
"This is not in the future – this is widespread now, and has been for decades," said lead author of the initial study and co-author of the second study Jonathan Kingslake, a glaciologist at Columbia University’s Lamont-Doherty Earth Observatory in New York, in a statement. "I think most polar scientists have considered water moving across the surface of Antarctica to be extremely rare. But we found a lot of it, over very large areas."
The studies, which were both published in the journal Nature, were based on the systematic cataloguing of surface water images in the Antarctic dating as far back as 1947, coupled with satellite imagery from 1973 and later. In total, the researchers found close to 700 seasonal systems of interconnected waterways at the edges of the continent. Some of the meltwater rivers run up to 75 miles long, and can be found as high as 4,300 feet above sea level, where liquid water had been thought rare or even impossible.
Of course, the extent of the network may have grown over the past few decades in concert with rising temperatures because of climate change. Unfortunately, there is no way to know for sure, since early data is sparse in many areas. Still, Trusel says he is all but certain that melting in the Antarctic will become more widespread in the coming years.
"My research has assessed how surface melting may change in the future under various climate scenarios," he adds. "It shows that human emissions of greenhouse gasses essentially control the future of surface melting in Antarctica. The more we emit, the more surface melting and the greater potential for future ice shelf collapses and accelerated contributions to sea level."
The effects of warming global temperatures are already being felt in the Antarctic, says Stephen Price, a meltwater researcher at the Los Alamos National Laboratory in New Mexico.
"Ice shelves are very flat, and essentially lie at sea level. So a small increase in temperature at sea level can translate to an increase in temperature over a very large area of an ice shelf," Dr. Price tells the Monitor via email. "If temperatures at sea level are already near the melting point, then small increases in temperature could lead to huge areas of the surface of ice shelves that were previously frozen becoming melted, for at least part of the year."
Without drastic action to reduce emissions, the problem in Antarctica will only get worse, says Trusel. And the damage won't be confined to just one continent, flooding coastal regions worldwide.
"The consequences of increased surface melting in Antarctica could mean increased ice destabilization in the not too distant future," says Trusel. "Recent ice sheet modeling work that has incorporated increased surface melting and its impacts has shown that under 'business as usual' conditions, Antarctica could add up to one meter of sea level by the end of this century."
