Antarctica is home to more than you might think.

Harsh winters, waddling penguins,  research stations, blubbery seals, and, um... oh yeah, the Doomsday Glacier. This glacier is enormous, and  making sure it stays that way   is crucial for preventing  irreversible sea level rise.

It probably won’t surprise you  to hear that it’s shrinking. But the reasons it’s shrinking are a lot more  complicated than the one you’re imagining. So complicated that we’ve only recently  begun to understand all of them.

The good news is that, with these findings,   there’s a real chance we  can slow down the melting. Which is desirable for something  with “doomsday” in the name. [♪ INTRO] While “Doomsday Glacier” is super catchy, scientists much prefer to call it by  its proper name: Thwaites Glacier. It’s named after Fredrik Thwaites, a  glacial geologist and geomorphologist.

He never actually visited the glacier, but he was   so influential in the field of glacial  geology that they named it in his honor. It was discovered in 1947, and it’s  the single widest glacier in the world,   with an area of 192 thousand square kilometers. Or, to put it another way, larger than  the entire American state of Florida.

A lot colder than Florida, too. And I am manifesting that it is gonna stay that way! Thwaites Glacier is also very tall.

The ice is 800 meters deep at its thinnest,  and almost 4000 meters at its thickest! For comparison, the world’s tallest building,  the Burj Khalifa, is only 828 meters high,   so parts of the glacier would bury it in  ice several times over, with room to spare. The glacier is so big that  when a big chunk breaks off,   the tremors from the falling ice can be detected  by seismometers as far as 1600 kilometers away.

And it picked up its ominous nickname, the  Doomsday Glacier, because if it ever melts   or breaks apart, all the water locked up in  there could cause dramatic sea level rise. But let’s go back a bit to  review what a glacier is,   in case you slept through your  8am section of Glaciers 101. Glaciers come in two different flavors.

If you hike, the type you might be  familiar with are alpine glaciers. They form in chilly mountain regions and most of  them flow down into valleys like a river of ice. And then there are ice sheets,  like the Thwaites Glacier.

Instead of flowing in one direction,   they form domes that flow in all  directions, emptying out into the sea. This distinction is important because Antarctic   glaciers rest partially on land,  and float partially on the sea. That land vs sea ratio is  critical for understanding   a glacier’s potential impact on sea level rise.

See, if ice is already floating  in the ocean, like an iceberg,   and then it melts, that doesn’t  really affect the overall sea level. Think about it like a glass of ice water. No matter how full your glass is, it won’t  overflow when the ice eventually melts.

But if you add more ice cubes,  eventually the glass would overflow. As long as glacier ice is locked up on land,  their extra water isn’t overflowing our oceans. But as the world warms, glaciers like Thwaites  are flowing faster and faster toward the sea,   transporting all that ice to the ocean.

To be specific, estimates say that  if the Thwaites Glacier melts,   it alone could raise global sea  levels by as much as 65 centimeters. That’s more than double the amount that sea levels  have already risen since we started keeping track. Which is pretty bleak.

But believe it or not, that’s not the most  “doomsday” thing about the Doomsday Glacier. What scientists are really worried  about is that losing the Thwaites   Glacier might also destabilize  the West Antarctic Ice Sheet. This ice sheet contains enough ice to  raise sea levels by several meters,   which would be enough to flood almost  all of Florida’s coastal cities.

Orlando would nearly be beachfront property! The Thwaites Glacier is one of the only things  holding the West Antarctic Ice Sheet in place. So losing the Thwaites could make the West  Antarctic Ice Sheet fall into the sea too.

Despite this very real danger, many scientists  don’t like the ‘Doomsday’ nickname because it   makes it seem like we’re already doomed  and there’s nothing we can do to stop it. Which is absolutely not  what scientists are saying. There’s still a lot we could do to slow down   climate change if we could just  get our collective act together!

The glacier is shrinking, but  panicking about it isn’t useful. Scientists still don’t know enough to  predict a time of death for Thwaites Glacier. Because this whole thing is a little  more complicated than a cooler full   of ice cubes melting during your backyard cookout.

Thwaites Glacier is a complicated system. It has a lot of different forces acting on it,   and we don’t fully understand how  all those forces affect each other. So it’s hard to predict exactly  how much the glacier is melting,   or how it will react to  future temperature changes.

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That’s the nature of a glacier, but  Thwaites likes to keep us on our toes. A research paper from 2022 showed that rather than   sliding smoothly towards the ocean,  Thwaites tends to retreat in spurts. Glacial retreat happens when a glacier  shrinks faster than it gains new snow and ice.

Its terminus, the edge  point, ends up moving uphill. And researchers were able  to track Thwaites Glacier’s   retreat by looking at sedimentary ridge deposits. As glaciers flow, they scrape up a layer of  rock and dirt and add that to their ice river.

All that stuff gets transported to the edge of  the glacier and forms a small hill of sediment. A sedimentary ridge deposit, if you will. That means these ridges mark the  end of the sediment conveyor belt.

AKA the point where the glacier broke off  from the sea floor and started to float,   called the grounding line. As the glacier retreats, its grounding line  retreats, too, stepping closer to the shore. Researchers found Thwaites’ grounding lines  by swimming around under the glacier with an   autonomous underwater vehicle, basically  a robot with a sediment-seeking mission.

They found a pattern of rapidly retreating  spurts, occurring over the past two centuries. And, probably unsurprisingly, they  found that these spurts have been   getting closer and closer together over time. This isn’t just because the  ocean is getting warmer though.

It also has to do with the glacier’s geography. On one end, Thwaites is pinned in  place by the Thwaites Ice Shelf,   the floating section of the glacier  that’s attached to the grounding line. But on the other end, the glacier is unprotected.

It used to be shielded by the  Thwaites Glacier Tongue, a narrow,   floating extension of the glacier  that extended far beyond the land. But over the past couple decades, the  tongue has broken off into several icebergs,   leaving the rest of the glacier  more vulnerable and less stable. One of the largest icebergs,  B-22, broke off in 2002.

B-22 is approximately the size of Rhode Island. But that’s only like one  fiftieth of the size of Florida. Just in case you were wondering.

After B-22 detached, its largest portion, B-22A,   broke off and got grounded about 100  kilometers offshore from the Tongue. This turned out to be a good thing, because  like ice in your drink at that backyard cookout,   the iceberg managed to keep the surrounding  water cooler than it would have been otherwise. B-22A was stuck there for a really long time.

Like weirdly long for an iceberg. It started to move again in 2022. Since then, the tongue has split  into several more icebergs.

The latest iceberg, B-22J,  was spotted in September 2025. So those are the big changes to the Thwaites,   but there have also been smaller, less  visible changes beneath the surface. When glaciers melt, they release  cold, fresh water into the sea.

This can have a few strange effects,  because it changes the water’s density. It’s tempting to imagine the ocean  as one uniform blob of water. But if you had special goggles  that could see density,   you’d find the ocean is actually made of many  different small blobs with differing density.

The denser water sinks below the less dense bits,   like the wax in your lava  lamp that sinks as it cools. When it comes to seawater,   there are two main factors that affect  its density: temperature and salinity. Cold water is denser than warm water, but  salty water is denser than freshwater.

While Antarctic seawater isn’t exactly  warm, it is warmer than glacial melt. But it’s also saltier than glacial melt. So when cold, fresh water enters the  warmer, salty water, strange things happen.

If you were looking at it  with your density goggles,   you’d see some really weird  lava lamp shenanigans going on. For example, in 2013 a network of subglacial lakes  drained out from underneath Thwaites Glacier. The sudden influx of all that fresh lake  water started mixing with the seawater,   creating pockets of warm saltwater suspended in  the flow of cold freshwater from the glacier.

And some scientists think that when  these pockets of warm water are held up   against the glacier’s surface, they can  trigger faster melting at those spots. But that’s only one possibility. While we know a subglacial lake drained,  and we know that it caused some mixing,   we can’t actually quantify the  full effect of that mixing.

There’s also evidence that hurricane-like  underwater storms could accelerate melting. When water masses of different  densities smash into one another,   they create storms of swirling water. The vortices can be up to 10 kilometers wide,   and like hurricanes, they carry  a lot of power and momentum.

When they reach an ice sheet  floating on top of the water,   like the free edge of the Thwaites  Glacier, they can slide under the ice. When the storm gets trapped under an ice  shelf, its whirling pulls cold water away   from the glacier, and draws warm water  up towards the ice from the deep ocean,   effectively melting the ice  shelf from the bottom up. And since these storms are caused by the collision  of water masses of differing temperatures,   that meltwater can flood out into the  ocean and spin off even more vortices.

Scarily similar to how surface  melting can trigger a feedback loop,   the underwater melting can build stronger  storms that lead to even more melting. Since 2025, storms like these have  been responsible for a fifth of the   underwater melting events at Thwaites Glacier. And, like regular hurricanes, these processes   are expected to get worse with  increasing ocean temperatures.

These effects are like the tip  of an iceberg when it comes to   everything that’s been going on with this glacier. Simply adding up calving icebergs  and underwater melting and rising   ocean temperatures doesn’t quite  equal the glacier loss that we see. So measuring how fast Thwaites  Glacier is shrinking is complicated.

And understanding exactly why it’s  shrinking is even more complicated. To predict what’s going to  happen to it in the future,   and how those changes will affect sea level  rise, there’s a lot left we need to understand. This all matters because there’s a real  chance we could stop the shrinking.

Scientists have been brainstorming ways to  prevent Thwaites Glacier from melting entirely. And some of them are pretty surprising. Like, researchers have thought of placing  reflective material over portions of the glacier,   or building fences to retain snow that  would otherwise blow into the ocean,   or drying the seabed beneath the glacier so  it doesn’t slide toward the ocean as easily.

But there have also been discussions  of building berms or artificial islands   out of material dredged up from the  seafloor or shipped in from elsewhere. Placing these structures around or  beneath glaciers could protect against   the warmer ocean water that stirs  up vortices and accelerates melting. One particularly interesting idea is to build   flexible sheets that keep cold water close  to the glacier and direct warm water away.

These curtains could keep the glacier  frostier, like a coat to keep the cold in. But they’d come with a hefty price tag. One of those curtains would  cost about 50 billion dollars.

As you can imagine, a lot of these  ideas have been controversial. And it isn’t just price  that has scientists worried. Some scientists think that direct interventions   distract from a much more important  goal: lowering global CO2 emissions.

That’s the number one thing that we can do to stop  climate change, and all that it comes with it. Including melting glaciers. But that said, even if we  stopped emitting CO2 tomorrow,   the ocean wouldn’t stop warming right away.

So maybe it's a good idea to have some  other solutions up our sleeve so we can   keep Thwaites Glacier from living  up to its other, more ominous name. [♪ OUTRO]