Dangers to ancient Antarctic ice portend a future of rapidly rising seas, but a new study may relieve one nagging fear: that ponds of meltwater fracturing the ice below them could cause protracted chain reactions that unexpectedly collapse floating ice shelves. Though pooled meltwater does fracture ice, ensuing chain reactions appear short-ranged.
Still, massive increases in surface melting due to unusually warm weather can trigger catastrophic ice shelf collapses like that of the iconic shelf "Larsen B," which shattered in 2002. Now, a study led by a researcher at the Georgia Institute of Technology has modeled fracture chain reactions and how much water it would take for a repeat of that rare, epic collapse.
Larsen B's disintegration was preceded by an atypical heatwave that riddled it with meltwater ponds, focusing researchers' attention on pond fracturing, also called hydrofracturing. They discovered that a melt pond hydrofracturing the ice shelf can prompt neighboring ponds to do the same. Concerns grew of possible extensive chain reactions, which the new study addressed.
Too much meltwater
"The chain reactions will not spread that far on the ice shelf," said Alex Robel, an assistant professor in Georgia Tech's School of Earth and Atmospheric Sciences. "Normally, it would take many years for the chain reactions to have an effect on the integrity of the ice shelves. But there's a caveat. Ponds that are close together and growing rapidly deeper could destroy the ice's integrity."
"There is a speed limit in the study that shows that an ice shelf can't collapse ridiculously fast," said co-author Alison Banwell, a glaciology researcher at the University of Colorado Boulder. "However, if it becomes as covered in meltwater ponds very quickly like Larsen B was, it can collapse in a similar way." She added, "Multiple hydrofracture chains originating in different areas of an ice shelf could also lead to a larger-scale ice shelf breakup."
The researchers published their results in the journal Geophysical Research Letters on October 24, 2019. The research was funded by the National Science Foundation and the Cooperative Institute for Research in Environmental Sciences at CU Boulder. An unrelated, recent study reported a record number of meltwater ponds on Antarctica.
"Currently there are not nearly enough ponds on any ice shelf for a repeat of Larsen B, but much meltwater is weighing on ice shelves and contributing damage to them," said Banwell, who helped pioneer hydrofracture research on ice shelves.
Materials provided by Georgia Institute of Technology. Note: Content may be edited for style and length.
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