Antarctic ice’s instability concerns scientists
ABOVE THE ROSS SEA, ANTARCTICA >> Engines droned as a military cargo plane sliced through the frigid air, making straight for the world’s largest chunk of floating ice.
In the belly of the plane, an engineer with a shock of white hair directed younger scientists as they threw switches. Gravity meters jumped to life. Radar pulses and laser beams fired toward the ice. On computer screens, in ghostly traces of data, the surface of the Ross Ice Shelf began to yield secrets hiding beneath. Antarctica, an immense, frozen land, is hiding many of them. And some scientists are starting to think that nothing less than the fate of human civilization could hang on unraveling those mysteries.
Many people regard Antarctica as unchanging. But the ice moves from the land to the sea, billions of tons every year, and has done so for eons. Today the ice in parts of Antarctica seems to be accelerating. Some glaciers have been destabilized by warmer ocean waters. Scientists fear that parts of the ice sheet may be in the early stages of an unstoppable disintegration. Because the breakup of parts of the ice sheet could raise the sea level by many feet, the continued existence of vulnerable cities near the world’s coastlines could depend on what happens here. “We’re 9,000 miles from New York,” said the whitehaired engineer, Nicholas Frearson, a leader of a Columbia University team that was studying Antarctica late last year. “But we are connected by the ocean.”
A rapid deterioration of Antarctica might, in the worst case, cause the sea to rise so fast that tens of millions of coastal refugees would have to flee inland, potentially straining societies to the breaking point. Climate scientists once regarded that scenario as fit only for disaster films. Now they cannot rule it out. Yet as they try to determine how serious the situation is, they confront a frustrating lack of information.
Recent computer forecasts suggest that if greenhouse emissions continue at a high level, parts of Antarctica could break up rapidly, causing the sea to rise 6 feet or more by the end of this century — twice the maximum increase that an international climate panel projected four years ago. But the computer forecasts were deemed crude even by the researchers who created them. “We could be decades too fast or decades too slow,” said one, Robert M. DeConto of the University of Massachusetts, Amherst. Alarmed by signs that parts of the ice sheet are destabilizing, the National Science Foundation in Washington and the Natural Environment Research Council in Britain are joining forces to get better measurements in the main trouble spots. The effort could cost over $25 million and take years to yield clearer answers about the fate of the ice.
It is a race against time to produce clearer forecasts about the consequences of emissions. Columbia scientists have spent the past two Antarctic summers flying over the Ross Ice Shelf, which helps to slow the flow of land ice into the sea. Computer forecasts suggest that it may be vulnerable to collapse in the next few decades. The project to map the shelf’s structure and depth, funded by taxpayers through the National Science Foundation, puts Columbia and its partner institutions on the front lines of one of the world’s most urgent scientific and political problems. Remote as Antarctica might seem, everyone who gets in a car, eats a steak or boards a plane contributes to emissions that put the continent at risk. If those emissions go unchecked and the world is allowed to heat up enough, scientists have no doubt that large parts of Antarctica will melt into the sea.
But they do not know the trigger temperature, or whether the acceleration of the ice means that Earth has already reached it. The question, said Richard B. Alley, a scientist at Pennsylvania State University, is easier to ask than to answer: “How hot is too hot?”
More than 60 percent of the fresh water on Earth is locked up in Antarctica’s ice sheets. The risk is clear: Even a partial collapse of the ice has the potential to inundate coastal cities across the globe.
The ice has been building up for tens of millions of years. Thin layers of snow falling were gradually pressed into ice, burying mountain ranges and building an ice sheet more than 2 miles thick. Under its own weight, that ice flows downhill in slow-moving streams that eventually drop icebergs into the sea.
If the ice sheet were to disintegrate, it could raise the sea level by more than 160 feet — a potential apocalypse, depending on how fast it happened. Research suggests that if society burns all the fossil fuels known to exist, the collapse of the ice sheet will be inevitable. Improbable as such a large rise might sound, something similar may have already happened, and recently enough to be lodged in collective memory. In the 19th century, ethnographers realized that virtually every old civilization had some kind of flood myth.
In the Epic of Gilgamesh, waters so overwhelm the mortals that the gods grow frightened, too. In India’s version, Lord Vishnu warns a man to take refuge in a boat, carrying seeds. In the Bible, God orders Noah to carry two of every living creature on his ark.
“I don’t think the biblical deluge is just a fairy tale,” said Terence J. Hughes, a retired glaciologist. “I think some kind of major flood happened all over the world, and it left an indelible imprint on the collective memory of mankind that got preserved in these stories.” That flooding would have occurred at the end of the last ice age. Ice ages occur when wobbles in Earth’s orbit change the distribution of sunlight, allowing huge ice sheets to build up. At the peak of the last ice age, about 50,000 years ago, the ice sheets grew so large and locked up so much water that the sea level fell by an estimated 400 feet. Perhaps 25,000 years ago, the ice sheets began to melt, and the sea level began to rise. Over several thousand years, coastlines receded inland by as much as 100 miles.
Human civilization did not yet exist, but early societies of hunters and gatherers living along the world’s shorelines would have watched the inundation claim their lands.
Remnants of that ice age remain. A little bit of ice still clings to mountains, but the main survivors are the two great ice sheets covering Greenland and Antarctica. Scientists once thought that further destruction of those ice sheets was likely to take thousands of years. But, starting in the 1970s, some warned that the ice sheets could be vulnerable much sooner if greenhouse emissions were not checked.
Scientists are racing to understand what is happening to the ice shelf as the planet warms around it. A multiple-mile-long iceberg broke off of the Ross Ice Shelf and became grounded in McMurdo Sound in Antarctica.