Massive Antarctic iceberg raises climate fears

An iceberg about twice the size of Auckland city broke off Pine Island Glacier in West Antarctica sometime between February 8 and 9, satellite data shows, confirming yet another in a series of increasingly frequent calving events in this rapidly warming region.

The Pine Island Glacier is one of the fastest-retreating glaciers in Antarctica, and along with the Thwaites Glacier nearby, it’s a subject of close scientific monitoring to determine whether these glaciers are in a phase of runaway melting, potentially causing vast inland areas of ice to flow to the sea and raising sea levels.

According to Nasa, the region surrounding the Thwaites and Pine Island glaciers contains enough “highly vulnerable ice” to raise global sea levels by about 1.2m.

The new iceberg from Pine Island did not last long as a single chunk of ice, instead breaking off into smaller pieces that will gradually head out to sea. But this behaviour is consistent with recent studies of this glacier.

While this calving did not give rise to a record-large iceberg, as occurred with the Larsen C ice shelf in 2016, scientists are nonetheless concerned that such events are becoming increasingly common as the glacier flows into the sea via a floating ice shelf. If the shelf destabilises sufficiently, the glacier — like Thwaites nearby — could begin a rapid and potentially unstoppable cycle of ice loss, since the land upon which the ice rests dips downward as one heads inland.

This could allow relatively mild ocean waters to penetrate well inland, melting more ice and speeding its movement into the sea.

Large calving events used to take place at Pine Island Glacier every four to six years, but they’re now a nearly annual occurrence.