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March 19 — A massive Antarctic ice shelf has collapsed into the sea, shattering into thousands of icebergs and alarming researchers by the speed with which the process unfolded. Described by one researcher as “staggering,” the rapid collapse once again fueled the debate over whether global warming is to blame.
‘We knew what was left would collapse eventually, but the speed of it is staggering.’
— DAVID VAUGHAN
British Antarctic Survey scientist U.S. AND BRITISH government agencies confirmed the collapse of what’s known as the Larsen B ice shelf.
“The shattered ice formed a plume of thousands of icebergs adrift in the Weddell Sea,” the U.S. National Snow and Ice Data Center reported Tuesday.
Before it broke apart, the shelf was 650-feet thick and about the size of Rhode Island.
Scientists with the British Antarctic Survey in 1998 first predicted its eventual collapse and satellite images over the years suggested as much. The process accelerated over the last month, with the single largest piece calving on March 5.
720 BILLION TONS
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David Vaughan, a glaciologist with the British Antarctic Survey, noted that since the 1998 prediction “warming on the peninsula has continued and we watched as piece-by-piece Larsen B has retreated.”
“We knew what was left would collapse eventually,” he added in a statement, “but the speed of it is staggering.” It’s “hard to believe,” he said, that 720 billion tons “of ice sheet has disintegrated in less than a month.”
The U.S. agency noted that 720 billion tons is enough ice for 29 trillion five-pound bags and enough water to irrigate nearly 1,500 golf courses for a year.
Some 1,255 square miles of ice shelf disintegrated between Jan. 31 and March 7. Over the past five years, Larsen B lost nearly twice that amount and is now about 40 percent the size of what it used to be, the U.S. agency reported.
CONCERN OVER ICE SHEETS
The British Antarctic Survey said its scientists would be researching when such an event last happened and which ice shelves are threatened in the future. Earlier studies found four other ice shelves had been retreating in recent years.
The weakening of the Larsen B ice shelf was first noted in the late 1990s. This photo released by Greenpeace in Feb. 1997 shows researchers dwarfed by one fissure.
The researchers emphasized that ice shelves themselves would not raise sea levels because they were already floating in water. However, because shelves hold back ice sheets on the continent, their collapse could allow ice on the ground to slowly move into the sea, thereby raising sea levels over time.
The U.S. agency noted the the next shelf to the south, the Larsen C, “is very near the stability limit, and may start to recede in the coming decade if the warming trend continues.”
“More importantly,” it added, is what might happen with the giant Ross Ice Shelf, the main outlet for several major glaciers draining the West Antarctic Ice Sheet — which is 6,000-feet thick, covers an area the size of Mexico, and contains enough water to raise global sea levels by 15 feet.
“The warmest part of the giant Ross Ice Shelf is in fact only a few degrees too cool in summer presently to undergo the same kind of retreat process,” the agency said.
New cracks in Larsen B were observed in the weeks prior to the sudden collapse.
GLOBAL WARMING DEBATE
Both the U.S. and British agencies attributed the collapse and other retreating shelves to warmer temperatures over the last half century.
That would fit in nicely with arguments made by environmentalists and many scientists that manmade emissions of greenhouse gases like carbon dioxide are causing global warming. Greenpeace, for one, called the collapse “a harbinger of global warming.”
Others, including some scientists, say it’s possible that any warming is due to natural shifts, not manmade causes, and that further studies are needed before taking global action to reduce emissions.
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The agencies did not enter the debate over what has caused the warming around the Antarctic Peninsula.
The British Antarctic Survey limited its observation to earlier studies that found the peninsula has warmed by 4.5 degrees Fahrenheit over the last 50 years — much faster than global warming worldwide or even in other parts of Antarctica. The peninsula is the Antarctic area closest to southern Argentina and Chile.
The National Snow and Ice Data Center said studies had estimated that Larsen B had existed for at least 400 years and probably since before the end of the last major ice age 12,000 years ago.
“This is the largest single event in a series of retreats by ice shelves in the peninsula over the last 30 years,” the agency said, attributing them to “a strong climate warming in the region.”
COOLING IN SOME AREAS?
But other studies have suggested some Antarctic areas might be cooling.
One study reported new measurements showed the ice in West Antarctica was thickening, reversing earlier estimates that the sheet was melting. The Antarctica Peninsula extends from West Antarctica.
The researchers said the thickening, if not merely part of some short-term fluctuation, represented a reversal of the long retreat of the ice.
Another recent study concluded that Antarctica’s harsh desert valleys — long considered a bellwether for global climate change — have grown noticeably cooler since the mid-1980s.
Air temperatures recorded continuously over a 14-year period ending in 1999 declined by about 1 degree Fahrenheit in the polar deserts and across the White Continent, that paper said.
The Associated Press contributed to this report.
‘We knew what was left would collapse eventually, but the speed of it is staggering.’
— DAVID VAUGHAN
British Antarctic Survey scientist U.S. AND BRITISH government agencies confirmed the collapse of what’s known as the Larsen B ice shelf.
“The shattered ice formed a plume of thousands of icebergs adrift in the Weddell Sea,” the U.S. National Snow and Ice Data Center reported Tuesday.
Before it broke apart, the shelf was 650-feet thick and about the size of Rhode Island.
Scientists with the British Antarctic Survey in 1998 first predicted its eventual collapse and satellite images over the years suggested as much. The process accelerated over the last month, with the single largest piece calving on March 5.
720 BILLION TONS
Advertisement
David Vaughan, a glaciologist with the British Antarctic Survey, noted that since the 1998 prediction “warming on the peninsula has continued and we watched as piece-by-piece Larsen B has retreated.”
“We knew what was left would collapse eventually,” he added in a statement, “but the speed of it is staggering.” It’s “hard to believe,” he said, that 720 billion tons “of ice sheet has disintegrated in less than a month.”
The U.S. agency noted that 720 billion tons is enough ice for 29 trillion five-pound bags and enough water to irrigate nearly 1,500 golf courses for a year.
Some 1,255 square miles of ice shelf disintegrated between Jan. 31 and March 7. Over the past five years, Larsen B lost nearly twice that amount and is now about 40 percent the size of what it used to be, the U.S. agency reported.
CONCERN OVER ICE SHEETS
The British Antarctic Survey said its scientists would be researching when such an event last happened and which ice shelves are threatened in the future. Earlier studies found four other ice shelves had been retreating in recent years.
The weakening of the Larsen B ice shelf was first noted in the late 1990s. This photo released by Greenpeace in Feb. 1997 shows researchers dwarfed by one fissure.
The researchers emphasized that ice shelves themselves would not raise sea levels because they were already floating in water. However, because shelves hold back ice sheets on the continent, their collapse could allow ice on the ground to slowly move into the sea, thereby raising sea levels over time.
The U.S. agency noted the the next shelf to the south, the Larsen C, “is very near the stability limit, and may start to recede in the coming decade if the warming trend continues.”
“More importantly,” it added, is what might happen with the giant Ross Ice Shelf, the main outlet for several major glaciers draining the West Antarctic Ice Sheet — which is 6,000-feet thick, covers an area the size of Mexico, and contains enough water to raise global sea levels by 15 feet.
“The warmest part of the giant Ross Ice Shelf is in fact only a few degrees too cool in summer presently to undergo the same kind of retreat process,” the agency said.
New cracks in Larsen B were observed in the weeks prior to the sudden collapse.
GLOBAL WARMING DEBATE
Both the U.S. and British agencies attributed the collapse and other retreating shelves to warmer temperatures over the last half century.
That would fit in nicely with arguments made by environmentalists and many scientists that manmade emissions of greenhouse gases like carbon dioxide are causing global warming. Greenpeace, for one, called the collapse “a harbinger of global warming.”
Others, including some scientists, say it’s possible that any warming is due to natural shifts, not manmade causes, and that further studies are needed before taking global action to reduce emissions.
Environment news
Keep up with environment news: MSNBC's special section is updated regularly
• Click here to bookmark Environment News
The agencies did not enter the debate over what has caused the warming around the Antarctic Peninsula.
The British Antarctic Survey limited its observation to earlier studies that found the peninsula has warmed by 4.5 degrees Fahrenheit over the last 50 years — much faster than global warming worldwide or even in other parts of Antarctica. The peninsula is the Antarctic area closest to southern Argentina and Chile.
The National Snow and Ice Data Center said studies had estimated that Larsen B had existed for at least 400 years and probably since before the end of the last major ice age 12,000 years ago.
“This is the largest single event in a series of retreats by ice shelves in the peninsula over the last 30 years,” the agency said, attributing them to “a strong climate warming in the region.”
COOLING IN SOME AREAS?
But other studies have suggested some Antarctic areas might be cooling.
One study reported new measurements showed the ice in West Antarctica was thickening, reversing earlier estimates that the sheet was melting. The Antarctica Peninsula extends from West Antarctica.
The researchers said the thickening, if not merely part of some short-term fluctuation, represented a reversal of the long retreat of the ice.
Another recent study concluded that Antarctica’s harsh desert valleys — long considered a bellwether for global climate change — have grown noticeably cooler since the mid-1980s.
Air temperatures recorded continuously over a 14-year period ending in 1999 declined by about 1 degree Fahrenheit in the polar deserts and across the White Continent, that paper said.
The Associated Press contributed to this report.
