Antarctica’s Pine Island Glacier – one of the fastest melting glaciers on the continent – is a new worry for climatologists.
The problem has to do with its ice shelf, a frozen ledge on the edge of Pine Island Glacier. The ice shelf helps to stabilize and contain the huge ice flow behind it.
But now it’s crumbling into pieces.
In the last five years alone, more than a fifth of the ice shelf has broken away in the form of huge icebergs that fall into the sea and drift off.
At the same time, the glacier has started to lose ice faster. Since 2017, the speed of the ice flowing from the glacier into the sea has increased by 12%.
Those losses are summarized in a new study published in the journal on Friday Scientific advances.
The big question is what will happen next, according to lead study author Ian Joughin, a glaciologist at the University of Washington. There is a possibility that the ice shelf may stabilize and the flow of ice may slow down, or at least stop accelerating.
On the other hand, “the other scenario is that this process will continue and the shelf will fall apart a lot faster than we expected,” he told E&E News.
Pine Island Glacier is a mammoth of the Antarctic Ice Sheet. Studies suggest that the glacier on the edge of West Antarctica, bordering the Amundsen Sea, pours nearly 60 billion tons of ice into the ocean every year. These losses have accelerated since at least the 1970s.
The ice shelf at the edge of the glacier – a kind of floating ledge jutting out into the sea – resembles a cork in a bottle, Joughin said. It helps stop the flow of all the ice pushing against it from behind. The weaker the cork becomes, the more ice flows into the ocean, where it contributes to the rise in global sea levels.
Scientists were already concerned about the Pine Island Glacier. The ice shelf had thinned in recent years, melted from bottom to top by warm ocean water seeping under the ice.
This process – warm water melting the ice from below – is a growing problem for glaciers along the coast of West Antarctica (Climate wire, April 10, 2018). The water itself appears to come from warm currents rising from the deep sea near the Antarctic coast. Experts believe that changing wind patterns in the southern hemisphere – likely altered in part by climate change – help drive these warm currents to the edge of the ice.
As the Pine Island ice shelf became thinner and weaker, the ice flow accelerated in “seizures and beginnings,” according to the researchers. It would accelerate rapidly for a few years and then settle down for a few years. The ice flow was relatively stable between 2009 and 2017.
That changed about five years ago when the ice shelf began to shed icebergs more and more frequently, some of which were several kilometers long. Last year the glacier lost a piece twice the size of Washington, DC
The scientists believe that the uneven speed of the glacier flow in the past few decades is at least partly responsible. Over time, cracks and fissures formed in the ice. As of 2017, the shelf began to fall apart quickly.
At the moment, scientists aren’t sure if the shelf will continue to break apart as quickly as it has in recent years. It’s an exceptionally difficult process to simulate in models, Joughin said.
Fortunately, satellites are helping scientists keep a close eye on the glacier. The European Space Agency takes new pictures of the site every six days.
If the shelf continues to dissolve, it is possible that the flow of ice could accelerate dramatically – perhaps doubling or tripling, noted Joughin. It’s an alarming possibility; Pine Island Glacier is already responsible for more than a quarter of Antarctica’s contribution to sea level rise in recent decades.
But there is still too much uncertainty to say how likely this scenario is.
“It’s a bit of a stretch for the shelf to fall apart, but it’s not a great distance,” Joughin said. “I really hate making a strong prediction one way or another that is going to happen.”
Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2021. E&E News provides important news for energy and environmental professionals.