Antarctica’s ‘doomsday glacier’ won’t collapse even in worst-case scenario

Thwaites Glacier in AntarcticaDoomsday GlacierIf it collapses, coastlines around the world could be flooded. Annual sea level rise of 4%As ice is lost, the glaciers will soon Collapse into the seaLike falling dominoes.

But is such a rapid collapse really as likely as feared? A new study into the vulnerability of the Swaites Glacier suggests: Instability of marine ice cliffsIt gives me hope. But Survey resultsThat doesn’t mean Thwaites is stable.

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Polar Scientist Mathieu MorlighemThe research leader explains the results.

Why is Thwaites Glacier so important?

Thwaites Glacier drains a vast area of ​​the Antarctic ice sheet, about 74,000 square miles (192,000 square kilometers), an area larger than Florida. When snowflakes fall within its drainage system, they end up breaking off into icebergs in the ocean off the coast of Thwaites.

What we’re witnessing right now at Thwaites Glacier is a disaster unfolding in slow motion.

Thwaites Glacier’s bedrock is below sea level and slopes downward inland, so the glacier deepens towards the inside of the ice sheet. This slope makes it very difficult to slow the retreat once the glacier begins to retreat and exceeds the amount of ice lost through snowfall. And as the climate warms, Thwaites Glacier is already retreating at an accelerating rate.

Thwaites Glacier contains enough ice to raise global sea levels by more than 2 feet (0.65 meters). If Thwaites Glacier begins to destabilize, neighboring glaciers will also destabilize. So what happens to Thwaites Glacier affects the entire West Antarctic Ice Sheet and sea level rise along coastlines everywhere.

What is marine ice cliff instability?

Marine ice cliff instability is a relatively new concept that has been proposed by scientists in the past decade.

Many of the glaciers around Antarctica have huge floating extensions called ice shelves that support the glaciers and slow the flow of ice into the ocean. Climate warming is seeing some of these floating extensions break off, sometimes very rapidly, over the course of a few weeks to months.

If the Swates Ice Shelf were to break apart, it would expose very high sea-facing ice cliffs along its 75-mile-long (120-kilometer) front. Ice can only withstand so much force, so if the cliffs are too high, they will collapse into the sea.

This would expose new ice cliffs further inland, but because they are further inland they would be higher, and according to marine ice cliff instability theory, if the cliffs collapsed rapidly, it could set off a domino effect that would cause even higher ice cliffs to collapse in turn.

But no one has ever observed marine ice cliff destabilization in action, and we don’t know if it will happen because a lot depends on how quickly the ice breaks up.

What did we find out about the risk to Thwaites?

When the theory of marine ice cliff instability was first introduced, rough approximations were used for how ice cliffs would collapse if ice shelves disappeared.

Subsequent studies have found that the ice cliffs won’t systematically collapse until the ice is about 442 feet (135 meters) high, and even at that point, the rate of collapse will be slower than expected until the ice gets even higher.

We used three high-resolution models to explore what this new physical understanding of ice cliff instability means for Twaites Glacier this century.

Our findings suggest that if the entire Swaite Ice Shelf were to collapse today, instability in the marine ice cliff alone would not cause the ice front to retreat inland as quickly. Without the ice shelf, glacier ice would flow seaward much faster, causing the glacier front to thin. As a result, the ice cliffs would not grow as high.

They found that the Switzer Glacier will remain relatively stable until at least 2100. They also simulated the collapse of the ice shelf 50 years from now, when the glacier’s grounding line (where the grounded ice meets the sea) would retreat deep inland, and found that even in that case, instability in the marine ice cliffs alone would not cause rapid retreat.

The results call into question recent estimates of how quickly Thwaite could collapse, including a worst-case scenario that the Intergovernmental Panel on Climate Change described in its latest assessment as “unlikely.”

“Thwaites Glacier is the glacier that everyone’s worried about. When we model the whole ice sheet, this is where the marine ice cliff destabilization starts and spreads far inland. So if Thwaites Glacier is not as vulnerable to ice cliff collapse as we thought, that’s a good sign for the whole ice sheet.”

However, marine ice cliff instability is only one mechanism for ice loss, and this finding does not mean that Swaites Glacier is stable.

What else could be causing glaciers to retreat at an accelerated rate?

There are many processes that destabilize the Antarctic ice sheet, some of which are very well understood.

So far, most of the recent ice mass loss can be explained by ice-ocean interactions. Antarctica is a very cold place, so atmospheric warming hasn’t had a big effect yet. But warm ocean currents are getting under the ice shelves, thinning them from below and weakening them. That means ice flows can move faster because there’s less resistance.

Over the past few decades, warm water from the Antarctic Circumpolar Current has been intruding and melting the ice from beneath the Amundsen Sea region, which includes the Switze and Pine Island glaciers.

What does this have to do with climate change?

Antarctica may seem like a faraway place, but human activities that warm the planet, such as burning fossil fuels, are having a dramatic effect on both poles: Loss of ice is leading to rising sea levels, affecting coastal areas around the world.

The choices people make today will determine how quickly the waters rise.

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