How Do Icebergs Form? Scientists Explain in New Study

ilulissat iceberg cave photo

Image from kaet44

It's not quite rocket science, but, as it turns out, it does involve a healthy dose of math and physics. The new "law" coined by Richard Alley, a glaciologist at Pennsylvania State University, and a team of other U.S.-based researchers will allow scientists to predict when and how icebergs in Greenland and Antarctica calve, or break off from larger ice shelves. The calving process is important because it is known to accelerate ice sheet flow and contribute to sea level rise.

iceberg breaking image

Image from NASA

Reporting their findings in the latest issue of Science (sub. required), Alley and his colleagues found that iceberg calving increased in relation with the along-flow spreading rate of an ice shelf. (In other words, the faster a parent ice shelf spread out over the ocean, the more likely an iceberg was to calve.) A faster spread meant that more cracks would form throughout the shelf, making it more susceptible to calving. The width and thickness of the shelves also matters. Until now, there had been no physically based law for how this process works.

The basic equation the team used can be boiled down to: the rate of spreading times the width of the shelf times its thickness, all times a constant. (A complete law, they explain, would also include forcing from waves and tides, geometry and other physical/material properties.) This "calving law" will help modelers predict future ice sheet break-ups -- a component that had been missing from most current ice-flow models examining the behavior of ice sheets under global warming.

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