Like a driver facing a crack in a windshield, scientists have been watching a rift growing across a giant ice shelf in Western Antarctica for years, waiting for the day that it would break. This week, a trillion-ton expanse of ice nearly the size of Delaware broke off into the ocean.
"This event will fundamentally change the landscape of the Antarctic Peninsula," scientists involved in Project Midas, which studies the impact of melting on ice shelf dynamics and stability, wrote on its website. The group announced early this morning that satellite data had confirmed the break.
The break that sliced off about 10 percent of the Larsen C Ice Shelf was driven by natural processes, and it isn't going to raise sea level on its own because the ice shelf was already floating on the water. But it can't be viewed in isolation.
Though it will be years before scientists understand the impacts of the break, what remains of the Larsen C shelf will be drastically altered, and climate change could play a part in driving what happens next.
Antarctica's ice shelves are facing other forces as global temperatures rise. Warmer water has been detected closer to the edges of Antarctica in recent years, and that can accelerate the melting of ice shelves from below. Likewise, warmer air can increase surface melting from above.
The ice shelves act as giant buffers, slowing the flow of glaciers from the frozen land behind them. When an ice shelf disappears, the land-based glacier ice it held back can flow faster into the ocean, directly contributing to sea level rise. After the smaller Larsen B Ice Shelf, just up the peninsula, quickly broke apart over the span of a few weeks in 2002, studies found that the flow of glaciers behind it accelerated sharply.
"Although this is a natural event, and we're not aware of any link to human-induced climate change, this puts the ice shelf in a very vulnerable position," said Martin O'Leary, a glaciologist at Swansea University, said as the Midas project announced that the ice shelf had broken. "This is the furthest back that the ice front has been in recorded history. We're going to be watching very carefully for signs that the rest of the shelf is becoming unstable."
Jonathan Kingslake, an assistant professor at Columbia University's Lamont-Doherty Earth Observatory, also raised concerns about the stability of the ice shelf and other Antarctic ice shelves amid changes underway in the region. "More broadly, warming on the Antarctic Peninsula is linked to human activity and probably triggered the collapse of two more northerly ice shelves," he said.
For a closer look at the mechanics of ice shelves and some of the risks their breakup creates, here are more sources.
- The European Space Agency used satellite data to calculate the new giant iceberg's vital statistics. The results: the area that broke off is about 190 meter thick (623 feet), 6,000 square kilometers (2,300 square miles) at the surface, and contains about 1,155 cubic kilometers of ice, or about 1 trillion tons. "Icebergs calve from Antarctica all the time, but because this one is particularly large, its path across the ocean needs to be monitored as it could pose a hazard to maritime traffic," the ESA said.
- The New York Times and The Guardian go into more detail and provide maps and images of how ice shelves hold back the ice on Antarctica, land ice that would raise sea level as glaciers and ice streams flowed more quickly to the ocean. The land upstream from Larsen C is estimated to hold enough ice to raise sea level by 10 centimeters. The National Snow and Ice Data Center and the Antarctic Glaciers website further explain the mechanics and importance of ice shelves and the impacts on neighboring land ice when they break apart.
- Changes in the ice and water temperatures around Antarctica also affect wildlife and ecology, both on land and in the ocean. The Long-Term Ecological Project based at Palmer Station, Antarctica, has been tracking climate changes in the West Antarctic Peninsula for over 25 years. A series of reports last year looked at the changing ecology and biology of the region. CBS talked to some of the scientists about the impact of the changing climate on penguins and other life this year.