Accelerated ice shelf breaking up and retreat at Pine Island Glacier, West Antarctica.

Pine Island Glacier in West Antarctica had several major iceberg calving events over the past decades.

Above, rift in Pine Island Glacier ice shelf, photographed from the air during a NASA Operation IceBridge survey flight on Nov. 4, 2016.

Common on polar ice shelves, this type of calving is with no clear connection to ocean-ice dynamic forcing.

Researcher Ian Howat from Ohio State University, said:

“It’s generally accepted that it’s no longer a question of whether the West Antarctic ice sheet will melt, it’s a question of when. This kind of rifting behaviour provides another mechanism for rapid retreat of these glaciers, adding to the probability that we may see significant collapse of West Antarctica in our lifetimes.”

Coincident with rift formation was the sudden disintegration of the ice mélange that filled the northern shear margin, resulting in ice sheet detachment from this margin. Examination of ice velocity suggests that this internal rifting resulted from the combination of a change in ice shelf stress regime caused by disintegration of the mélange and intensified melting within basal crevasses, both of which may be linked to ocean forcing.