LANL models new climate domain

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By Roger Snodgrass

Los Alamos National Laboratory is confronting one of the most alarming and most poorly understood implications of global warming.

What would happen if the vast ice sheets of West Antarctica or Greenland, both already showing signs of climate stress, began to melt even faster?

How long might it take for sea levels to rise? Would oceans swell by several meters and cause harbors and beaches to flood? What islands might become totally submerged?

How quickly would that happen?

The risk is called abrupt climate change, but it’s also known as “the nasty surprise,” “the jokers in the deck” or “the tipping point,” that precipitous moment when a trend becomes a catastrophic problem.

Bill Lipscomb of Los Alamos National Laboratory has been modeling sea ice, which he said does not directly contribute to the ocean level problem.

Even if the Arctic sea ice almost disappears in the summer by 2040 as LANL’s models have predicted under one scenario, that won’t add to the ocean level, because the volume is already there.

In recent years the menacing possibility of an abrupt change over the course of a decade rather than a century, has called greater attention to all the fresh water that has been locked up in ice sheets, covering land primarily in Greenland and Antarctica.

Greenland’s ice cap is two kilometers thick. West Antarctica holds some 3.8 million cubic kilometers of ice.

There are many differences between them, Lipscomb said. Greenland is more susceptible to surface warming and melting could be accelerated by melt water coming up under the glaciers, for example.

The melting and potential slide of West Antarctica’s ice sheet would be caused by warmer ocean water circulating under the ice shelves.

Together they could add as much as 40 feet to sea level if they slid into the ocean.

Now Lipscomb and colleague Phil Jones, who leads the climate modeling effort at Los Alamos, have been called into a new national collaboration sponsored by the Department of Energy to factor in the ice sheets.

Over the next several years, Los Alamos National Laboratory will apply its climate modeling climate expertise to one of the most threatening causes of abrupt change – marine ice sheet instability.

 “From recent observations, we’ve seen accelerated melting of all the ice sheets,” Jones said. “From our past assessment, we thought we wouldn’t see those impacts for perhaps a hundred years, but now with accelerated melting we’re thinking things might happen a little faster. How much and how fast affects ocean rise, but will it be one meter over a hundred years? We’re not certain at this point.”

The new research program, IMPACTS (which stands for Investigation of the Magnitudes and Probabilities of Abrupt Climate Transitions), is led by Berkeley National Laboratory and includes four other labs in addition to LANL: Argonne, Lawrence Livermore, Oak Ridge, and Pacific Northwest.

The combined work will go into the next version of the Community Climate System Model (CCSM) one of the models used by the Intergovernmental Panel on Climate Change, an international body that produces a comprehensive report every seven years. The next one comes up in 2014.

LANL’s models currently program sea ice and the ocean current components for the CCSM, aggregated by the National Center for Atmospheric Research in Boulder, Colo.

Climate research is going through a subtle shift after decades of emphasis on whether warming was occurring, to what to do about it.

“From the past IPCC assessments we’ve become more confident about what’s going on at the global scales,” Jones said.

“What the policy makers are doing now is asking us to give them more information on how this is going to impact their communities on issues like water availability. Sea rise issues affects all our coastal cities, so that’s why we’re interested.”