Two largest ice sheets losing ice fast

1 December ScienceDaily

The planet's two largest ice sheets have been losing ice faster during the past decade, causing widespread confusion and concern. A new international study provides a firmer read on the state of continental ice sheets and how much they are contributing to sea-level rise.Dozens of climate scientists have reconciled their measurements of ice sheet changes in Antarctica and Greenland over the past two decades. The results, published Nov. 29 in the journal Science, roughly halve the uncertainty and discard some conflicting observations.

"We are just beginning an observational record for ice," said co-author Ian Joughin, a glaciologist in the University of Washington's Applied Physics Laboratory who is lead author on an accompanying review article. "This creates a new long-term data set that will increase in importance as new measurements are made."

The paper examined three methods that had been used by separate groups and established common places and times, allowing researchers to discard some outlying observations and showing that the results agree to within the uncertainties of the methods

"It provides a simpler picture," said co-author Benjamin Smith, a research scientist at the UW's Applied Physics Laboratory. "In the 1990s, not very much was happening. Sometime around 1999, the ice sheets started losing more mass, and probably have been losing mass more rapidly over time since then.

"The effort, led by Andrew Shepherd at the University of Leeds in the UK, reconciles three existing ways to measure this loss.

The first method takes an accounting approach, combining climate models and observations to tally up the ice gain or loss.