Oct 98 German Scientists floating away on ice.
A German research station with its accompanying scientists is adrift off Antarctica after a massive chunk of the Ronne Ice Shelf broke off last week. At 147 km long and 50 km wide it is larger than the state of Delaware and is considered by many scientists as evidence of global warming AFP.
Running Hot and Cold over Global Warming
New Scientist15 February 1997
Broken ice, but what does it mean?
Elisabeth Mealey, Antarctic Peninsula
RIFTS in the Larsen B Ice Shelf, east of the Antarctic Peninsula, indicate that the shelf's collapse is "imminent", Greenpeace claimed last week. Scientists agree that the Antarctic Peninsula, which reaches up from the frozen continent towards South America, is rapidly becoming warmer. But glaciologists contacted by New Scientist say that the cracks highlighted by Greenpeace do not necessarily indicate that Larsen B is about to disintegrate.
The world's attention focused on the Antarctic Peninsula two years ago when a 1300-square-kilometre section of the northern Larsen A Ice Shelf collapsed, breaking into thousands of icebergs over a threeweek period. Its disintegration is now so complete that the Greenpeace icebreaker Arctic Sunrise, which is in the area for a month to document signs of climate change, was able to sail within 2 kilometres of Cape Worsley-a point that was once 47 kilometres from the edge of the ice shelf.
Rift zone: Cracks are beginning to appear in the Larsen B Ice Shelf
Larsen B, to the south, is next in line if the warming continues. "It will be destroyed without any doubt. When, we don't know," says Rudi Del Valle of the Argentinian Antarctic Institute in Buenos Aires, who is on board the Arctic Sunrise. Helmut Rott of the University of Innsbruck in Austria, who is involved in a project to monitor Larsen B in the field and from satellite observations, agrees that the disintegration of the ice is likely to spread south. But he notes that Larsen B has been riven by large cracks since at least 1994. "They have been there for years." If the collapse of the shelf were imminent, Rott adds, glaciologists would expect to see a change in the slow movement of the ice within it. This has not been recorded. Scientists familiar with the area also point out that the climate changes recorded in the Antarctic Peninsula do not seem to be happening elsewhere in Antarctica. At Britain's Halley Station, on the eastern side of the Weddell Sea, there is no warming trend, says Chris Doake of the British Antarctic Survey in Cambridge, who documented the demise of Larsen A. Although the significance of the cracks in Larsen B remains uncertain, the Greenpeace cruise has given geologists their best view yet of the seabed that used to be hidden beneath Larsen A. Using an echo sounder, Ricardo Roura of Greenpeace and Jorge Lusky of the Argentinian Antarctic Institute have found a channel more than 800 metres deep, at least 15 kilometres wide and some 30 kilometres long. Del Valle speculates that the channel was filled with cold glacial meltwater, and that this may have prevented Larsen A collapsing earlier. However, Doake notes that the ice shelf's disintegration correlated well with air temperature, and this suggests that the water beneath Larsen A may not have had much of a protective influence. "Exactly what the connections are, no one really knows," he says.
Sci Am Jul 95 Antarctica is heating up, and the evidence is in the ice- or at least in its melt. One satellite image from this past January (left) shows the spidery-looking James Ross Island surrounded by water (top right): ever since the first maps were made 100 years ago, it has been connected to the Antarctic peninsula by an ice shelf. The image also shows the peninsula, composed of a chain of mountains (lower left to upper right), surrounded by dark patches of sea; the gargantuan Larsen ice shelf appears at the lower left. A satellite image taken shortly after, in February (right), documented further changes. The ice shelf has retreated; a 50-mile-long iceberg has calved; and the northernmost part of the shelf, just above the center of the picture, has disappeared, creating a plume of ice rubble. Other Antarctic ice shelves are also retreating, and "they are all ones we said would be sensitive to climatic change," notes David G. Vaughan of the British Antarctic Survey. Vaughan says the west side of Antarctica has warmed 2.5 degrees Celsius over the past 50 years. But any link with global warming is unproved, he cautions. -Tim Beardsley
Southern Oceans may hold key to Climate New Scientist 96
Major changes to climate appear to have a 10,000 year cycle in both the northern and now the southern hemisphere. Hienrich events in the northern hemisphere cause the growth and subsequent collapse of arctic ice sheets. Little Kroon and others in Paleocenography report that changes to the antarctic Benguela current and its connection with the trade winds could also cause a similar oscillation 3000 years ahead of the northern one (or 7000 years behind). The oceans may control the world's climate as much as CO2.
Is The Frozen North in Hot Water? New Scientist 8 Feb 97
Vincent Kiernan, Washington DC
CLIMATE change in the far north has got leading Arctic scientists so worried that they have written to the US National Science Foundation (NSF) urging it to support a monitoring programme to find out what is going on. Vast stretches of the Arctic Ocean have warmed by 1 IC or more since the late 1980s, while 'Vast st atmospheric pressure over the region has dropped, the researchers' open letter Oce-A--n- notes. "It is becoming increasingly clear that the Arctic is in the midst of a significant change," they warn. But no one knows whether this is a conse- quence of global warming, or part of a natural climatic variation in the region. So far, more than three dozen leading polar scientists have signed the open letter, says James Morison of the Polar Sciences Center at the University of Washington in Seattle, one of its organisers. "We already feel that we've got a consensus that this is important to look into," Morison says. The scientists make the strongest case so far that a major climate shift is occurring, based on data from studies conducted in the 1980s and 1990s. "Their science argument seems to make sense," says Tom Pyle, head of the NSF's Arctic sciences section. Morison and his col- leagues compared data gathered on recent Arctic cruises-including one by the US nuclear submarine Pargo in 1993-with results obtained t earlier. This shows that the Arctic Ocean now contains more water originating from the relatively warm Atlantic than was t the case at the end of the 1980s. The boundary between Atlantic water and the cooler water from the Pacific has shifted, the scientists say, bringing warm Atlantic water to an extra 550 000 square kilometres of the Arctic Ocean-more than t twice the area of Britain. The cruises also detected regions of relatively warm water in the Arctic Ocean over the Lomonosov and Mendeleyev Ridges on the seabed (see Map). Water over the Lomonosov Ridge was almost 1 OC warmer than in 1977 and 1983. "Changing that amount of water by 1 oC is a very significant change," says Pyle. Meanwhile, atmospheric pressure over the Arctic has been declining. In every year since 1988, average atmospheric pressure has been below the average recorded during the quarter century that started in 1970. Patterns of winds and atmospheric pressure appear to have changed most over parts of the Arctic Ocean where circulation pattems have also altered in recent years, the scientists say. Morison and his colleagues want to use aircraft, buoys and a Navy submarine to gather data on changing Arctic condi- tions. This monitoring effort should con- tinue indefinitely, not just for a season or two, as is common for most such research programmes, they say. Russian sci- entists ran a similar monitoring programme from 1950 to 1987, mostly using aircraft. But that work has halted because of Russia's economic woes. F7