Tabular icebergs are separating from Antarctic ice shelves
James Kirkham
The Icebergs of the size of the city once went to the coast of Great Britain when the ice layers that cover a large part of northern Europe were rapidly retired about 18,000 to 20,000 years.
James Kirkham, of the British Antarctic survey and his colleagues, have found that the giant of flagelo brands made as their lower ones crossed the sediments of the sea. The long and similar characteristics to the comb are buried under mud in the North Sea, but are still visible in the seismic survey data collected to look for oil and gas.
“We can estimate from the scope of the squeezes and what is known is the old level of the sea that the thesis beges were probable from five to a few tens or kilometers wide and perhaps a couple of hundreds of hundreds of city of Iceberg thick”, secondary size British of a medium size.
In Antarctica, tabular or table icebergs are a spectacular view. Some, such as recent giants known as A23a and A68a, would rival the United States states equally small in terms of area. They leave the ice shelves: the wide floating protuberances of the glaciers that flow from the earth to the ocean.
Therefore, the recognition that tabular icebergs existed in the North Sea is a clear indication that the margins towards the sea of a layer of British and Irish ice also had ice shelves. And it means that there could be some lessons for the future Antarctic decline, says Kirkham.
In the Northern Sea, the straight tram lines of the large icebergs are exributed by jet channels made by the narrow throat of much smaller ice blocks. In other words, there is a “regime change” in which large icebergs are replaced by innumerable small icebergs as the ice shelves break in response to the increase in temperatures, says Kirkham.
The radiocarbon dating of the sediments shows that this change occurs for a period of 20,000 to 18,000 years ago.
The observation throws doubts about the idea that the delivery of Mega-Bergs such as A23a and A68a could announce the generalized collapse of the ice shelves of the Antarctica.
Emma Mackie, from the University of Florida, has tracked the size of tabular iceberg into satellite data from the mid -1970s and discovered that the trend is essentially flat.
“James’s research underlines mine, which is that great childbirth events are not necessarily a sign of instability or cause of alarm,” says Mackie. “Rather, ice shelves disintegrate through death by a thousand cuts. We should worry when we stop seeing the great childbirth events.”
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