the antarctica debate
GLOBAL WARMING SYNOMPSIS-ANTARCTICA DEBATE
banshee-WASHINGTON (Reuters) - An unexpectedly rapid warming of lakes on a desolate Antarctic island provides compelling evidence of the environmental impact wrought by rising global temperatures, scientists said on Thursday.
The gain in winter lake temperatures was three times higher than that of local air temperatures, the scientists said. The amount of time during a given year that the lakes were completely frozen over declined by more than four weeks.
This decline allowed the lake water and sediments to absorb solar energy that normally would be reflected away by the ice.
Nutrient levels in the lakes rose, most likely because streams ran over thawed ground rather than ice. Algae and phytoplankton in the lakes also increased.
The study was published just two weeks after other researchers reported in the journal Nature that temperatures had dropped since the mid-1980s in Antarctica's arid and inhospitable desert valleys. Those researchers noted that the climate is warming up on average globally, and that Antarctica's Dry Valleys region represented an exception.
John Turner, also of the British Antarctic Survey, said a complex picture has emerged of temperature change over the whole Antarctic continent. He noted that while the Antarctic Peninsula region experienced one of the largest temperature increases on Earth over
the last 50 years, the South Pole has experienced a modest cooling.
goofyfish---------------------------------------------------------------------------------
The Antarctic has cooled during the past 35 years despite the worldwide temperature rise, according to a study published today. The finding challenges the belief that global warming is raising temperatures across the whole of the southern continent. But the authors accept that some Antarctic "hotspots" have got warmer over the past few decades. (full text here)
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Dr Ian Joughin, of the American space agency's (Nasa) Jet Propulsion Laboratory, and Slawed Tulaczyk, of the University of California at Santa Cruz, say they have found "strong evidence" that the ice sheet in the Ross Sea area is growing, by 26.8 gigatons per year. (full text here)
banshee- Follow up, Antarctic Ice Shelf...
720 billion tons is not right. It is actually 72 billion tons... Click on the link for a little movie with comment...
http://www.msnbc.com/news/726247.asp?pne=msn
Staggering end to Antarctic ice shelf
U.S., British researchers tie rapid collapse to warming trend A NASA satellite image shows the thousands of icebergs created by the Larsen B ice shelf collapse. Brownish streaks are rocks and glacial debris exposed from the former underside and interior of the shelf.
By Miguel Llanos
MSNBC
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 offered fuel for 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. Some 1,255 square miles of the ice shelf disintegrated between Jan. 31 and March 7, the U.S. National Snow and Ice Data Center reported Tuesday. “The shattered ice formed a plume of thousands of icebergs adrift in the Weddell Sea,” the center said, adding that 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.
Before it broke apart, the shelf was 650 feet thick and about the size of Rhode Island.
Scientists with the British Antarctic Survey first predicted in 1998 that it would eventually 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
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 said 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. center noted that 720 billion tons is enough ice for 29 trillion 5-pound bags.
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 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.
‘CLOSER TO THE LIMIT’
Ted Scambos, a glaciologist with the National Snow and Ice Data Center, said in a statement that the Larsen B collapse “gave us the information we need to reassess the stability of ice shelves around the rest of the Antarctic continent. They are closer to the limit than we thought.”
“Loss of ice shelves surrounding the Antarctic continent could have a major effect on the rate of ice flow off the continent,” Scambos added. The center, located at the University of Colorado, noted that 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 said, 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 center said.
New cracks in Larsen B were observed in the weeks prior to the sudden collapse.
New Iceberg Breaks Off Shelf
Chunk of Ice Peeled From Ross Ice Shelf
The Associated Press
May 9 — An iceberg 47 miles long and 4.6 miles across has broken off the Ross Ice Shelf in the Antarctic, the National Ice Center reported today.
The giant sheet of glacial ice and snow was named C-18, meaning that it's the 18th iceberg to be tracked in that section of Antarctica since 1976, when record keeping began.
The iceberg, floating close to the ice shelf, is not considered a hazard to navigation. It was spotted on satellite images.
The discovery comes just under a month after a much larger iceberg — 40 miles by 53 miles — broke away from another part of Antarctica. That iceberg is known as B-22.
Also in March, a large floating ice shelf in Antarctica collapsed. The 1,250-square-mile section of the Larsen Ice Shelf collapsed during a five-week period that ended March 7. It splintered into a plume of drifting icebergs.
Meanwhile, however, new measurements indicate the ice in parts of Antarctica is thickening, reversing earlier estimates that the sheet was melting.
Mixed Signals
Scientists reported in January that new flow measurements for the Ross ice streams indicate that movement of some of the ice streams has slowed or halted, allowing the ice to thicken.
Researchers don't know if the thickening is merely part of some short-term fluctuation or represents a reversal of the long retreat of the ice
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.”
The weakening of the Larsen B ice shelf was first noted in the late 1990s. This 1997 photo shows people dwarfed by one fissure. 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.
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 center said, attributing them to “a strong climate warming in the region.”
In comments to MSNBC.com, Scambos was careful not to tie the collapse to manmade emissions of greenhouse gases, and noted that computer models actually predicted different regional effects from those gases. But he added that the collapse was so sudden in geological time that it’s not clear it was due to natural causes either. What’s needed, he said, are improved computer models, more sampling of ice cores for climate changes and continued tracking of ice shelves and sea ice.
“The tools are there,” he said, “we need to apply them.”
COOLING IN SOME AREAS?
Other studies have actually 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.
edufer-Wet1, how difficult is for you (and most other people) to understand that the Larsen shelf (and other ice barriers) have collapsed, not melted. The cooling that has being going on in Antarctica during the last 25 years produced such a gigantic ice mass that, finally, overwhelmed the resistance of the ice shelf borders and plunged the ice mass into the waters beneath. A purely mechanical reason.
Global warming has nothing to do with it, because there is nothing like "warming" going on Earth --as demonstrated by ALL satellite and radiosondes measurements since they began recording temperature measurements, decades ago. If there is something, as shown by the satellites, it is a slight trend towards "cooling".
banshee-May 14 ? The Antarctic Peninsula ice shelves are cracking up and, on the face of things, it is the most serious thaw since the end of the last ice age 12,000 years ago.
The break-up of the ice shelves in itself is a natural process of renewal, but the size and rate of production of icebergs ? some the size of major cities ? is alarming scientists, some of whom blame global warming.
Significant warming in parts of the pristine Antarctic wilderness is expected to continue to send huge icebergs into the Southern Ocean, and lead to the disintegration of other sections of ice shelves that fringe Antarctica's continental ice cover. A longer-term effect would be if the disintegration led to a meltdown of the grounded West Antarctic ice sheet, which would cause the world's oceans to rise by up to five meters (17 feet).
The Antarctic Peninsula, which juts out into the Southern Ocean, has warmed by 2.5 degrees Celsius over the past 50 years, while some other areas have cooled. Some parts of West Antarctica have been losing ice, while, like shifting grains of sand on a beach, ice has built up elsewhere.
edufer-
Contradictions, contradictions... The Larsen shelf broke off, it did not thaw or melted. As it has been demonstrated before, Antarctica has been cooling during the last 25 years, so the huge amount of ice formed during those 25 years caused the breakoff, just for the sheer weight, not because temperatures that have been going down. At least they recognize that some scientists blame the "thaw" to global warming.
banshee-Earlier this year, satellites observed the rapid collapse of much of the enormous floating Larsen ice shelf that had existed on the peninsula since the last Ice Age, 12,000 years ago. The likeliest cause of that, geologists said, is that surface ice melted and penetrated through the shelf, weakening it to the point where it broke up catastrophically. With summer temperatures in the peninsula substantially above freezing, "it is almost certain that warming precipitated the collapse," King said.
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"What is well established is that most of the Antarctic Peninsula has been warming significantly over the past 50 years or so for which we have records," he said. "Over the rest of the continent, the signals are a lot less clear - at some stations you will see a slight warming, and at others you will see a cooling trend, but none of the observations would pass the test that we would use for statistical significance. Indeed, for the vast majority of the continent we don't have the observations that would enable us to say whether it is warming or cooling."
..
Many questions have been raised about the stability of the West Antarctic sheet, containing about 13 percent of the continent's ice, which is anchored to rock that is below sea level. If this ice were to melt precipitously, it could raise the world's average ocean level by about 5 meters. Using engineering risk-analysis methods, British and Norwegian scientists concluded last year, however, that there was only a 5 percent chance of major sea-level rise due to disintegration over a period of a few hundred years of the ice covering West Antarctica.
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Satellite and other evidence shows that the ice sheets are actually getting thicker, and that the Antarctic Dry Valleys, the continent's largest ice-free area, have cooled somewhat. The National Science Foundation says records show a decline in seasonally averaged surface air temperatures of 0.7 degrees centigrade per decade, but has no explanation for this fall. Antarctica is the only continent where such cooling has been observed. The Antarctic
edufer's reply-I have emphasized "likeliest" and "surface ice melted...". "Likeliest" means they are not sure at all, and the use of this kind of vague terminology gives them the chance to say. "Well, we didn't say that was the reason, but we thought it could be". Then comes the absence of physics when they say the "surface ice melted, and penetrated through the shelf". For ice to melt, the conditio sine qua non is that temperatures be above the freezing point (0°C) or more. As temperature records in the Larsen ice shelf show, are well under the freezing point: (they are about -25°C below zero, or freezing point). It is unlikely (I say impossible) that ice can melt at say -10°C. But, even if somebody had melted the ice with a blowtorch, when the water starts to "penetrate" the ice creaks and crevices, it would freeze again. Altough the ice temperature there is 0°C, the air is still well below freezing point. I remember trying to ski in upstate New York when there was -20°C, but had forgotten to take along my ski goggles. When I started down the slope, the tears in my eyes froze, provoking a terrible pain. The same applies to the water "penetrating" the shelf. They say there is no observations on which we can say it is cooling or warming --nevertheless, they insist it is warming! They vast majority of the continent is cooling, but a small portion (as the Peninsula) is warming. As a result, the mean Antarctic temperatures are cooling significantly, but they cannot aknowledge this fact, so they have to say they don't have the observations that can prove a warming or a cooling. As the "real world observations" don't count, we must rely only in climate modeling. Its like throwing away our Physics books and trying to determine warming or cooling by means of Christian Andersen's fairytales.
listed sites by edufer
Global Warming: Does it Exist?
or:
http://users.erols.com/dhoyt1/annex12.htm
odin: Have a look at this!
http://news.bbc.co.uk/hi/english/sci/tech/newsid_1752000/1752999.stm
Very Relevant
http://news.bbc.co.uk/hi/english/sci/tech/newsid_1766000/1766064.stm
report | quote | edit | 01-18-02 at 04:52 AM
odin1099 posts & another
http://news.telegraph.co.uk/news/main.jhtml;$sessionid$QWZT0RIAACZIRQFIQMFSFFOAVCBQ0IV0?xml=/news/2002/01/20/wenv20.xml&sSheet=/news/2002/01/20/ixworld.html
CONCLUSION: we see that:-
1)Antarctic peninsula has warmed in the last few decades.
2)large chunks of ice from the ice shelves around Antarctica has collapsed in recent years.question is what caused it?
3)inner reaches of Antarctica has cooled significantly in recent years.There is evidence of thickening of ice flows an stabilization of ice shelves in some cases.on the average Antarctica has experienced general cooling with significant regional variations.
4)2 theories as to why the ice shelves colapsed.
a)this is due to the thaw induced by global warming.cannot explain why inner Antarctica has cooled.
b)this is caused by mechanical collapse of the shelves under pressure of ice accumulated at rates far above normal due to the general cooling of the continent.says cooling occurred due to unknown natural causes.
COMMENT:insufficient data to link collapse to supposed global warming.
