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“It’s the fifth large calving event since 2000,” Lhermitte said. “This one and 2015, they were much further inland than the previous ones. So there has been a retreat of the calving front, specifically between 2011 and 2015.”

The Post confirmed the break with researchers at NASA and with another team of scientists studying Pine Island, Seongsu Jeong and Ian Howat of Ohio State University. They published a paper last year finding that Pine Island Glacier has developed a troubling new way of losing ice, with rifts forming in the centre of its floating ice shelf from beneath, rather than at the sides, the traditional manner. They suspect this is a function of warmer ocean waters reaching the base of the glacier and weakening it.

“We predicted that the rifting would result in more frequent calving, which is what’s happening here,” said Howat by email. “If new rifts continue to form progressively inland, the significance to ice shelf retreat would be high.”

We predicted that the rifting would result in more frequent calving, which is what's happening here. Ian Howat

Last fall, NASA’s Operation IceBridge mission snapped a photo of the rift in Pine Island Glacier that would lead to the latest calving event.

The ice loss in this event is nowhere near the size of the much publicized loss of an enormous ice island from the Larsen C ice shelf this year. However, in terms of sea level rise, changes at the Pine Island Glacier are far more consequential.

The current break was in the glacier’s floating ice shelf, which extends out over a deep ocean cavity. Further inland, the floating portion of the glacier ends and the ice slopes down and touches the seafloor at a vulnerable point called the “grounding line.” Changes in the temperature of waters reaching the grounding line in recent decades are widely believed to be the reason that Pine Island Glacier has been thinning and losing so much ice.