The ice shelf is slowing down one of the fastest Antarctic glaciers, but it has lost significant chunks of ice in recent years.
In Antarctica, we find the Great Pine Island River Glacier. The end of this glacier rests on the water and has become thinner and thinner in recent years due to the warming of the core water. This is a worrying development, as it means that the ice on the water (also called the ice shelf) is losing mass and could provide less counterweight to the glacier behind it, on land. This allows this glacier to flow faster and dump more ice into the sea.
But the ice shelf slowing the glacier isn’t just about thinning; Between 2017 and 2020, large chunks of ice broke off. As a result, the ice shelf became five times smaller in the mentioned period. This also causes the glacier to flow faster, researchers now show in the journal science progress On.
Analysis of satellite imagery shows that the Pine Island glacier began flowing at a 12 percent faster rate between 2017 and 2020. Models suggest that this acceleration can be traced back to the erosion of large chunks of ice.
“It appears that the ice shelf has been collapsing as the glacier has accelerated over the past two decades,” researcher Ian Joughin said. Between 1990 and 2009 the glacier accelerated sharply. A few decades ago, the center of the ice shelf was moving about 2,400 meters per year. But after 2008 the speed was about 4,000 meters per year. At the edges of the bay in which the ice shelf is located, the ice shelf is now nearly flat.” The difference in velocity causes cracks to form in the ice shelf. “The faster the glacier flows, the more of these cracks are formed.” When the cracks meet the edge of the ice shelf or With each other, large chunks of ice can break free. The ice shelf lost mass at a rapid pace between 2017 and 2020, and thus could provide less counterweight to the glacier, which has therefore begun to flow faster.” Recent changes in velocity are not due to thinning the ice shelf, but to the loss of its outer edges.”
For now, the iceberg’s acceleration is still manageable. “But if the rest of the ice shelf shatters and disappears, the glacier can accelerate a lot.” It is unclear whether the ice shelf is doomed to collapse before our eyes. “It’s hard to guess.”
If the ice shelf were to disappear, the Pine Island glacier – which contains about 180 trillion tons of ice, enough to raise the global sea level by half a meter – could flow faster and lose more ice. “The Pine Island Glacier is really the glacier that’s losing most of the ice in Antarctica,” Juggin said. “I can’t say how much ice he would lose if the ice shelf disappeared, but it’s certainly not unreasonable for the ice loss to double.”
What the research now shows is that the ice shelf could be disappearing much faster than previously thought. “It now appears that the ice shelf may disappear in the next two decades,” said researcher Pierre Doutrio. By comparison, if the ice shelf only experienced warmer ocean waters, it wouldn’t collapse for another 100 years—or perhaps even longer. “So it could be a much faster and more surprising change.”
Jogin agrees. “We predicted that melting from below – causing the ice shelf to thin rather than abruptly collapse – would be the main problem for the Pine Island glacier in the next century. It’s a surprise that the ice shelf can break up now because it’s so weak because of the glacier’s acceleration.” Given its consequences, it was a particularly pleasant surprise.