( record that provided a picture of temp...)Ice core 'dipstick' indicates West Antarctic ice has thinned less than believed

record that provided a picture of temperature and snowfall patterns near Siple Dome. The layers get thinner and thinner with depth, as more ice and snow piles up. But the thinness of the layers deposited near the end of the Last Glacial Maximum indicate the ice also was being thinned by ice streams that were flowing even then, probably starting in about the same places they do now.

"If you are making the ice sheet thinner over time, you're also stretching it much farther, so the individual layers get much thinner than they would be in a steady state," Waddington said.

Waddington is lead author of a paper describing the research, which is being published online March 23 in Geology, a journal of the Geological Society of America. Co-authors are Howard Conway and Eric Steig of the UW; Richard Alley of Pennsylvania State University; Edward Brook of Oregon State University; Kendrick Taylor of the Desert Research Institute at the University of Nevada, Reno; and James White of the University of Colorado. The work was funded by the National Science Foundation.

Previous data have shown that, in the ice age, glacial ice built to quite high elevations in the mountains just inland from the Ross Ice Shelf. That led to the expectation that Siple Dome had to be substantially thicker than it is now as the ice moved from the mountains to the ice shelf. But the new study shows the ice could not be thick at Siple dome, so ice must have flowed toward the ocean with a very gentle slope for more than 600 miles. An ice sheet with such a low profile and gradual decline would have had to have a very slippery bed to maintain its continuous flow, Waddington said, and it appears the ice flowed vigorously despite being relatively thin.

One major implication of the research, he said, is that it disputes the theory that West Antarctic ice streams retreated when the ice shelf did. In the last ice age, the ice streams near Siple Dome had to be roughly where they are
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Source:University of Washington

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