Can refreezing Arctic sea ice help save polar bears?
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Polar bears might look cute and fluffy, but if you ever get up close to one, you're going to need to know how to beat it in a fight. The advice is not to run away, but to punch it on the nose. Hiya, I'm Hannah Gelbart, and today we are talking about polar bears. They're the biggest bears in the world. They can run up to 40 kilometres an hour, which is why you're advised not to try to outrun them. They can sniff out their prey from 16 kilometres away, and they can swim for hours in freezing cold water.

All of this means they need a lot of calories and their main hunting grounds are sea ice. But as it melts, it's leaving them vulnerable and hungry. So today you're going to hear some facts about polar bears and sea ice and you're going to find out whether refreezing the Arctic could help boost their numbers. Welcome back to What's in the World from the BBC World Service.

To break this down, I'm speaking to Victoria Gill, the BBC science correspondent. Hello, welcome back to the podcast. Hello, Hannah. Lovely to be here. You're literally my favourite animal expert and you have seen polar bears in real life. Did you ever have to punch one on the nose? That's very, very kind. I wouldn't consider myself an animal expert. I am a mere reporter, but I speak to a lot of animal experts in my job. So I'm very fortunate in that regard.

I did not have to punch a polar bear in the nose. The advice really is not to get close enough to them to be able to reach their nose. It's to avoid them altogether. But I have seen one up close. There's a polar bear under our tundra buggy right now. He's very curious about us. Oh my word.

So I made a documentary about polar bears in a wonderful place called Churchill in Manitoba on the Hudson Bay in Canada, in the just sort of sub-Canadian Arctic. And it's one of the most southerly places where polar bears live. The population of polar bears there is still bigger than the population of people in the town. And this particular population, because they're so dependent on the sea ice,

They hang around this bay when it melts in the summer, waiting in the autumn for that bay to freeze up again because they hunt from the ice. They use the ice as a hunting platform to catch seals. In the Arctic, the climate's warming faster than anywhere in the world. And that affects the polar bears because they need the ice. So we went out and saw them up close and it's amazing.

a weird experience because as you say, they are beautiful and adorable. Like looking into the face of one is reminiscent to looking at a teddy bear, but you also realise that these are incredibly dangerous predators and you wouldn't want to be on the ground anywhere near them. So it is a very confusing feeling to look into the face of something that is so

simultaneously adorable and lethal. You mentioned that the melting sea ice is affecting the populations of polar bears around the world. How are their numbers changing?

So that's a really good question, Hannah, because it's very difficult to say. There are populations all over the Arctic. The Hudson Bay population is one of the most southerly and temperatures are rising very quickly there. The length of time during that summer period where the bay has thawed out and is ice free is getting longer. And that has driven down the population of polar bears significantly.

How numbers are changing in terms of like the whole species and the whole of the Arctic, that's much more difficult to say. All of the data, all of the research that's being done is suggesting that their numbers could be going down, but we don't have enough data about every single population to say that that's actually the case.

So the sea ice is literally the platform that they dip their heads into the water from and they pull out these seals, which are very kind of fatty, blubbery creatures. And that's where they get the calories that they need to be able to grow to three metres tall. Is there any evidence of them adapting to be able to hunt in different climates and circumstances? Are there other animals they could catch in the water? Fundamentally, yes.

biologically they are dependent on the amount of fat that they get from eating a seal. So there is nothing that they can eat that can replace that very, very high fat, very high calorie diet. So while they will eat anything, there's not a sign that they're evolving to shift to something that could actually give them enough energy to survive and to thrive the way that they do when they're hunting from the ice.

You mentioned, Vic, some of the things that polar bears eat, and you're going to hear some more facts now about polar bears. This is Elisa McCool from Polar Bears International. Polar bears are the only marine bear. So all the other seven bear species have chosen to live on land, but polar bears have adapted to live on top of the frozen ocean.

Polar bears are also the most carnivorous bear. So they're eating more animals than any other bear. Really, they're eating more fat. They need a lot more fat than meat even, but they are eating a lot less fruits and veggies than all the other bears. Many bear species can survive indefinitely or almost fully on a vegetarian diet, but not polar bears. They would not do well.

They have the fattiest milk found on land. So when polar bear cubs are born, their mom has some of the fattiest milk we see on land. So it's over 30% fat. It's like drinking whipping cream. And this helps cubs grow really quickly. When they're born, they're about a pound. And by the time they're several months old, they can be over 20 pounds.

Their fur, of course, gives them wonderful camouflage. It looks white and blends in with the sea ice. It's actually clear and hollow, which helps them trap some warm air. And they've got two thick layers of it, a thick undercoat that's like a sweater, and then longer kind of overcoat hairs, more like a raincoat would be. And it's

sea ice isn't just a platform for the bears to access their food. Sea ice also is to the ocean what soil is to a forest. So sea ice is growing the base of the food chain in the Arctic. Algae is growing inside the ice and that's feeding the microorganisms that feed the fish, that feed the seals, that feed the bears. And there's whales and there's people and there's all sorts of life in the Arctic that's all tied to Arctic sea ice.

So, Vic, we've heard about some of the risks that this melting sea ice poses to polar bears. How else could it affect our planet? Fundamentally, the sea ice and this reflective surface kind of acts like a cooling mechanism for our whole planet. So, you know, all of us should really care about the state of Arctic and Antarctic sea ice. And

But it's because it's so white and so reflective that as the sun's energy comes in and warms the planet, a lot of it is reflected back when you have an icy or even better, a snowy surface. As the sea ice in the Arctic retreats, we've got more of that darker sea that is absorbing more of the sun's energy. So it's sort of this vicious cycle, this kind of positive cycle where as the sea ice retreats,

It heats up the planet more and it exposes more of that darker surface that's absorbing more of the sun's heat. So on it goes and on it goes. And one potential solution to all this that people are talking about is refreezing parts of the Arctic. It's an ambitious goal. Let's hear how it works. Hi, my name is Dr. Carrie Nichols. I'm an oceanographer. So the main technique that's being researched right now is...

where water would be pumped up from the ocean below the ice and then put up on top of the ice. So this first requires drilling a hole in the sea ice and then putting a pump

The water is exposed to the cold air and it freezes. There's a group called Real Ice that's based in the UK. They did a study last year in Canada at the High Arctic Research Station. And at the end of their study, they saw an increase of about a half a meter in ice thickness. There's another group called Arctic Reflections that conducted some studies in Svalbard last year. Their studies didn't really...

result in the ice lasting longer, but they do think that they conducted the research too late in the season to be effective. It's not going to be easy to scale up this effort. Real Ice is working on developing underwater drones that would deliver these pumping devices, but they estimate that they're going to need a fleet of 500,000 drones.

One of the issues with making ice is that ice is with fresh water. And so when you're making this fresh water ice, but you're using salt water, you're left with the salt. And so we kind of need to know what happens to the salt. Back to you, Vic. So how realistic would it be to refreeze parts of the Arctic?

I think that the short answer to that is we just don't know in terms of whether it would work on this huge millions of square kilometre scale. When you scale it up, there are loads of questions. You know, one is how feasible is that to pump all of that water and get that ice thickening across such a vast surface?

Another series of questions are, if you do that in the winter, is there going to be enough snow to replace, to fall on that sea ice and create that really reflective surface? Because what's super effective at reflecting the sun's energy is snow.

Then there's all the questions about how you affect the marine ecosystem. Now, if you're pumping seawater out from below the sea ice, you're pumping out some of that plant matter, some of those marine creatures. So what is that going to do to that whole ecosystem? There are lots and lots of questions, but I think the conclusion from all of this geoengineering of our planet and trying to fix these problems that we've created by

pumping greenhouse gases into the atmosphere that are warming the planet right now, all of these ways of fixing it, these tweaks, these technological fixes that we call geoengineering, they're quite controversial and they're still in kind of test phase. But I think some of the scientists that are working on this Arctic refreezing, this ice refreezing, say that basically we've run out of choices. We have to try these things because the planet is warming so quickly and we're not doing enough to slow that down. ♪

Vic, thank you so much for speaking to us. Absolute pleasure, Hannah. Thank you for having me. Well, that is it for today's episode. Thank you for joining us. I'm Hannah Gelbart. This is What In The World from the BBC World Service. We'll see you next time. Bye.