An Iceberg Caught in the Act of Forming

An airborne ‘eye in the sky’ has provided unprecedented views and details of a massive iceberg calving from its parent glacier in Antarctica. Essentially, we’re able to watch the process of an iceberg being born. NASA’s Operation IceBridge mission discovered a huge crack in the Pine Island Glacier in western Antarctica. The mammoth rift extends at least 18 miles and is 50 meters deep, and scientists say it could produce an iceberg more than 800 square kilometers in size.

“We are actually now witnessing how it happens and it’s very exciting for us,” said IceBridge project scientist Michael Studinger, Goddard Space Flight Center, Greenbelt, Md. “It’s part of a natural process but it’s pretty exciting to be here and actually observe it while it happens. To my knowledge, no one has flown a lidar instrument over an actively developing rift such as this.”

The specially outfitted DC-8 airplane for Operation IceBridge flew over the glacier on Oct. 14, 2011 and scientists noticed a crack. They made a special point to return again on Oct. 26 and saw the rift growing.

Pine Island Glacier last calved a significant iceberg in 2001, and some scientists have speculated recently that it was primed to calve again. But until the Oct. 14th flight, no one had seen any evidence of the ice shelf beginning to break apart. Since then, a more detailed look back at satellite imagery seems to show the first signs of the crack in early October.

While Pine Island has scientists’ attention because it is both big and unstable – scientists call it the largest source of uncertainty in global sea level rise projections – the calving underway now is part of a natural process for a glacier that terminates in open water. Gravity pulls the ice in the glacier westward along Antarctica’s Hudson Mountains toward the Amundsen Sea. A floating tongue of ice reaches out 30 miles into the Amundsen beyond the grounding line, the below-sea-level point where the ice shelf locks onto the continental bedrock. As ice pushes toward the sea from the interior, inevitably the ice shelf will crack and send a large iceberg free.

A primary goal of Operation IceBridge is to put the same instruments over the exact same flight lines and satellite tracks, year after year, to gather meaningful and accurate data of how ice sheets and glaciers are changing over time. They will be able to create 3-dimensional maps of the changes taking place.

Below is an animation that shows glacier changes in the highly dynamic Amundsen Embayment of West Antarctica, from satellite and Ice Bridge data.

Scientists know that ice speeds in this area have increased dramatically from the late 1990s to the present as the ice shelves in this area have thinned and the bottom of the ice has lost contact with the bed beneath. As the ice has accelerated, ice upstream of the coast must be stretched more vigorously, causing it to thin.

The changes on Pine Island and Smith glaciers have the potential as continuing sources of ice to the sea, and they have been targeted for repeat measurements in coming years.

Source: NASA