Antarctica’s coast is home to roughly 50 ice shelves — floating ledges of ice that jut out from the edge of the continent into the ocean — large enough to have names. There’s our old friend Larsen, the very relatably named Quar, the fancy-pants King Edwards, and others. Remember them now because as the planet warms, these ice shelves are increasingly developing fractures that put them at rigsk.
Right now, most of Antarctica’s ice shelves remain frozen and stable, even during the warmer months of the year. But if widespread global warming occurs later this century, that could change. New research shows that if rising temperatures drive melt water into those cracks, the ice shelves could be vulnerable to quick destruction. Their demise would unleash floods around the world.
The new study, published in Nature on Wednesday, suggests that 73 per cent of the total area of these ice shelves could collapse due to melt-induced fractures. Roughly 60 per cent of that area plays an important role in buttressing glaciers that keep ice locked up on land, shielding us from catastrophic sea level rise.
Floating portions of ice shelves are some of the most important ice on the planet. They act as a sort of firewall (ice wall?), restraining the flow of land ice into the ocean. Basically, they stabilise glaciers coming down from the ice sheet that covers the continent. If these shelves get destroyed, sea levels around the world could get pushed up rapidly as more land ice enters the ocean.
There are a number of processes that could cause their collapse, but the new paper looks at one called hydrofracturing where water, which is heavier than ice, forces the fractures to rip open, in turn causing the shelf to rapidly disintegrate. Most ice shelf fractures don’t have any liquid water in them as of yet. But as you may have heard, the world is getting warmer. And as it does, hydrofracturing could become a big problem.
To conduct their new research, the study’s authors used a combination of remote satellite sensing, theoretical modelling, and artificial intelligence.
“I trained a machine learning model — a neural network to be specific — to learn how fracture patterns look like on satellite images,” lead author Ching-Yao Lai, a postdoctoral researcher at Columbia University’s Lamont-Doherty Earth Observatory, wrote in an email.
Lai worked with a researcher from Google to train this model, then used it to predict the locations of coming fractures on the ice shelves and produce the first ever continent-wide fracture map.
“This is to the best of our knowledge the first use of machine learning on continent-scale data in the polar regions,” said Lai.
Using a physics theory called linear elastic fracture mechanics, the authors determined which portions of ice shelves provide important support to glaciers, keeping sea level rise under control. They then modelled which of those areas are vulnerable to meltwater fracturing, in part using results from a 2015 study that predicts the extent of ice surface melting would be widespread by 2100 if world leaders do nothing to curb the climate crisis (a scenario known as RCP8.5, or “business as usual”). The new findings show between 50 per cent and 70 per cent of the ice shelf area that blocks the flow of the Antarctic ice sheet into the ocean could be destabilized.
If all this fracturing comes to pass, it could have major consequences for Antarctic mass loss and global sea level rise. The exact impacts on how much oceans rise if this comes to pass, though, are still an area of active research.
“There are still many open questions remaining to be answered before we can make that sea level rise projection, such as how meltwater moves across the Antarctic ice shelves in a warming climate, and how do individual hydrofractures lead to a catastrophic collapse of ice shelves,” said Lai.
But the physics suggests the impact on sea level could be significant. All that extra water could inundate coasts and destroy entire communities. But this doesn’t have to be our fate, and Lai had some advice for world leaders looking to avoid this fate.
“Slow down climate change,” she said. “Reduce carbon dioxide emissions into the atmosphere.”