By Hilmar Gudmundsson, Adrian Jenkins and Bertie Miles
The Conger Ice Shelf in East Antarctica – a floating platform the size of Rome – separated from the continent on March 15, 2022. Since the beginning of satellite observations in the 1970s, the top of the shelf has disintegrated into icebergs as a series of glaciologists call the calving event.
Conger has been reduced to a strip 50 km long and 20 km wide attached to the vast continental ice sheet of Antarctica at one end and the ice-covered Bowman Island at the other. Two spawning events on March 5 and 7 reduced it further, separating it from Bowman and leading to its final demise a week later.
The world’s largest ice shelves surround Antarctica, extending its ice sheet down into the frigid Southern Ocean. Smaller ice shelves are found where continental ice meets sea in Greenland, northern Canada and the Russian Arctic. By limiting the amount of ground ice that flows upstream, they can control the loss of ice from within the layer into the ocean. When an ice shelf like the Conger is lost, the terrestrial ice that was once held behind the shelf can begin to flow faster as the resistance of the ice shelf is lost, leading to more ice falling into the ocean.
What caused the collapse?
Ice shelves are sometimes called the “safety bands” of Antarctica because they create a reverse flow of ice from the adjacent ice sheet. Some of the Antarctic ice melts on its surface, where the snow piles up. Instead, much of the continent was lost through birthing and melting along the undersides of floating ice shelves.
The breakdown and separation of parts of ice shelves is a natural process: ice shelves often experience cycles of slow growth due to isolated calving events. But in recent decades, scientists have seen several large ice shelves undergoing complete disintegration.
Along the Antarctic Peninsula, a whip-like land mass extends from mainland West Antarctica, these include the Prince Gustav Ice Shelf (from 1989 to 1995), the Larsen A ice shelf (1995), the Larsen B (2002) and the Larsen B shelf. the Wilkins band (2008 to 2009). In East Antarctica, where Conger was once, the Cook ice Shelf was partially lost in the 1970s. Taken together, this sequence of collapses suggests that some underlying environmental conditions, such as ocean temperatures ocean and atmosphere, are changing.
It’s too early to say what caused the Conger ice shelf’s collapse, but it doesn’t appear to have been caused by surface melting — no indication of any ponds on the ice shelf. The most recent sequence of events also preceded the record high air temperature recorded in Antarctica on March 18.
What are the future goals?
As glaciologists, we see the impact of global warming in Antarctica in increasing ice loss over time. And what happens in Antarctica is not in Antarctica.
The consequences of the collapse of the Conger ice shelf are not globally significant because the basin area that supplied the ice to the old shelf is small. And because of its shape, the Conger Ice Shelf is most likely not a significant support for the flow of ice upstream.
But global warming is making events like this more likely. And as more and more ice shelves around Antarctica collapse, the amount of ice loss will increase, and with it, global sea levels. There is enough ice on the West Antarctic Ice Sheet to raise sea levels by a few meters, and if East Antarctica begins to lose significant amounts of ice, the impact on sea levels could be measured in tens of metres.
Not everything that happens in nature is caused by global warming. Antarctica loses mass due to the discharge of icebergs and the ice shelves wax and wane as part of a natural cycle. But what we are seeing now, with the collapse of the Conger ice shelf and elsewhere, is the continuation of a disturbing trend whereby the Antarctic ice shelves in turn experience collapse. widespread.
Hilmar Gudmundsson is professor of glaciology, and Adrian Jenkins is professor of ocean science at Northumbria University, Newcastle; Bertie Miles was an original Leverhulme Fellow in the Geosciences at the University of Edinburgh