Tabular icebergs detach from Antarctic's ice shelves
James Kirkham
Icebergs the size of a city once derived beyond the coast of Great Britain when glacial caps covering much of northern Europe were in rapid retreat approximately 18,000 to 20,000 years ago.
James Kirkham During the British Antarctic Survey and his colleagues found the preserved surface marks that these giants made while their underside plowed by the sediments of the seabed. The long comb characteristics are buried under the mud in the North Sea, but are still visible in the seismic survey data collected to search for oil and gas.
“We can estimate the extent of the parks and what we know about the ancient sea level that these bergs were probably five to a few tens of kilometers wide and perhaps a few hundred meters thick – icebergs on the scale of a medium -sized British city,” Kirkham explains.
In AntarcticTabular icebergs or paintings are a spectacular view. Some, like recent giants known as A23A And A68Awould even compete with small American states in terms of zone. They Calbe of ice shelves – The wide and floating protumiers of glaciers flowing from the earth in the ocean.
The recognition that tabular icebergs used to exist in the North Sea is therefore a clear indication that the margins towards the sea of a British and Irish ice cap also had ice cream platforms. And that means that there could be lessons for the future decline of Antarctica, explains Kirkham.
In the North Sea, the right tram lines of large icebergs are too written by wavy hollows made by narrow skittles of much smaller ice. In other words, there is a “diet change” in which large icebergs are replaced by countless small icebergs while ice shelves break in response to temperature increase, Kirkham explains.
The sediment radiocarbon dating shows that this change occurred over a period of 20,000 to 18,000 years ago.
The observation casts a doubt on the idea that the calving of mega-brug like A23A and A68A could announce the generalized collapse of the Antarctic ice cream.
Emma Mackie At the University of Florida followed the size of tabular icebergs in satellite data from the mid -1970s and found that the trend is essentially flat.
“James' research underlines mine, which is that major calving events are not necessarily a sign of instability or cause of alarm,” explains Mackie. “On the contrary, the ice shelves disintegrate by death by a thousand cuts. We have to worry when we stop seeing the major calving events. ”
