Study: Antarctic Ice Sheet Is Thickening, Not Thinning

Jan. 18, 2002 -- A series of troubling reports in recent years have suggested Antarctica is warming and shedding its ice shelves at an alarming rate.

But a new study that used a highly precise image-snapping satellite suggests at least one prominent ice sheet — the West Antarctic Ice Sheet — is in fact getting thicker.

The report, plus other work finding that desert valleys on the continent have cooled recently, appear to contradict predictions that global warming is melting the continent's massive ice reservoirs.

This may seem like good news, but scientists say: Don't count on it. They warn other ice sheets continue to shrink even as this one thickens.

"There's no question that some parts of Antarctica are warming," said Ian Joughin, a geologist with the Jet Propulsion Laboratory at the California Institute of Technology in Pasadena. "But it could be this part of the ice sheet is not necessarily sensitive to global warming."

Details of the study by Joughin and Slawek Tulaczyk, a professor of earth sciences at the University of California, Santa Cruz. are published in this week's issue of the journal Science.

Mighty Ice Rivers

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The West Antarctic Ice Sheet contains enough ice to raise sea levels more than 16 feet if it were to melt. Recent concern has centered on whether all or part of this contribution might break off from the continent and flow rapidly into the ocean. Such a rise could flood coastal regions and submerge islands.

One way to measure the mass of an ice sheet is to compare how quickly ice flows into and out of it via ice streams. Ice streams are sections of ice and snow ranging 20-60 miles wide that grind along slippery, muddy beds at an average speed of about a half mile a year.

By measuring ice flow speeds at entrance and exit points of the ice sheets, Joughin and his team determined that one ice stream — Ice Stream C — has ground to a halt while another — the Whillans Ice Stream — has dramatically slowed its drainage into the sea.