The Current - World’s biggest iceberg runs aground

Episode Date: March 10, 2025

An iceberg weighing nearly a trillion tonnes, named A23a, appears to have run aground off the shore of an island in the South Atlantic. A scientist warns that it could pose a significant risk to local wildlife — but also presents an opportunity to study these rare, giant slabs of ice.

What does a mummified Egyptian child, the Parthenon marbles of Greece and an Irish giant all have in common? They are all stuff the British stole. Maybe. Join me, Mark Fennell, as I travel around the globe uncovering the shocking stories of how some, let's call them ill-gotten, artifacts made it to faraway institutions. Spoiler, it was probably the British. Don't miss a brand new season of Stuff the British Style. Watch it free on CBC Gem. This is a CBC Podcast. Hello, I'm Matt Galloway and this is The Current Podcast. In 1986, a monster was born. Scientists named it A23A. It was giant, made of ice, blindingly white, and sat in

Weddell Sea off the coast of Antarctica. A23A is the world's largest iceberg. It is close to 3,300 square kilometers. It weighs a trillion tons, two-thirds the size of PEI. In 2020, this iceberg freed itself from the ocean floor and began to float northward. And now it appears to have run aground about 70 kilometres off the shore of South Georgia, an island in the South Atlantic. There are concerns, given its size, about its potential impact on the local ecosystem there. Gareint Tarling is a research scientist with the British Antarctic Survey.

He is aboard the RRS Sir David Attenborough. It's a polar research vessel about 500 nautical miles away from this giant iceberg. Garaint, good morning. Hello. People have described this iceberg as, as larger than Las Vegas, twice the size of the city of London, the size of a small state.

What does it look like when, when you are as close to it as, as you are? Yeah, it's, it's quite a formidable site. So as you say, it rises from the ocean. It can be about 30 to 35 meters tall and it's just a wall of ice as far as you can see. It just goes off into the distance, probably into some fog because it's so cold as well around there. And yet you just see these crevices and so the blue caverns there and water lapping up against it. It's also quite a haven for wildlife as well. So that's the other amazing thing around these icebergs is that animals tend to gravitate towards them.

And so it's been on the move for 40 years and has now ended up, as I mentioned, at South Georgia Islands. Tell me about this island and who and what lives there. Yeah, South Georgia is right at the edge of the Antarctic Southern Ocean so it's it's as far north as you can go before you become you know sort of more like South Antarctic type temperate climates that you would get in Canada. But because it's in this ocean, this current that's coming from Antarctica, it's really cold. It's an amazing place for wildlife. So all the animals that you see in Antarctica, they're also in South Georgia as well. So when we go there, we see loads and loads of penguins and seals, also

recovering populations of whales. They're really abundant there now. And when we look in the oceans, we see tons and tons of Antarctic krill, which is right at the base of the food web. So it's a major area, almost an amazing nature wilderness really that is just right in the middle of the Southern Ocean. And so is this an expected kind of end point for this iceberg? Do people assume that it was going to run aground at some point in time and this just happens to be the place that it has stopped? No, not at all. This is really unusual for an iceberg, particularly of this size, to run aground around South Georgia.

It's not that they're uncommon. We do see icebergs around South Georgia. And there's something called Iceberg Alley, that a lot of icebergs come out from the Antarctic continent itself. And then they go in this particular current that's going from west to east and then ends up somewhere around South Georgia.

That's a really regular route. What they don't often do is run the grounds and we don't get icebergs this size either. That is incredibly rare to have something as big as this. So there's two things combined, running a ground and being so huge. That's quite a rare event that we haven't seen. So given, as you've described, the local wildlife population in South Georgia, what impact could this gigantic thing have on that population? Yeah, it's gonna be a mixed blessing for them, I think.

It's actually run aground now in the autumn season, so we're really nervous about things that might run aground in the spring and the summer, because that's when penguins and seals in particular, that's when they breed, that's when their chicks and pups are around, and the parents have to go out and do regular forays and come parents have to go out and do

regular forays and come back. So if there's something in their way that's going to delay them getting back and that could be quite devastating for the animals they're trying to bring up. But this is happening in the autumn and all those animals now have fledged and popped and they've actually gone on their way so it's not going to affect them so much. So we're thinking about other things that they might affect and one of the things is that because this iceberg is so deep, it's almost 300 meters deep, it's actually gouging the seafloor. And the other thing about South Georgia is that the seafloor is incredibly rich with biodiversity, untouched, incredible organisms you don't see anywhere else and this iceberg now is quite a destructive force having run aground just sort of

don't see anywhere else. And this iceberg now is quite a destructive force having run aground, just sort of tearing all this benthic community apart, which can sound quite devastating, but actually it's also a process of renewal as well, because now it's sort of gouging out these areas, it's creating this new space for other benthic organisms, seabed organisms to come in to populate. So it's a process that will be destructive,

but also creative in equal measure. Tell me more about that and about the potential benefits, if I can put it that way, of this iceberg arriving where it has. People have, I was reading about another scientist who said that when this thing arrives and perhaps it starts to melt, what is contained in it will release

an extraordinary amount of nutrients potentially into an area that otherwise might not have those nutrients. So tell me a bit more about that. That's the really fascinating thing about icebergs is that people think of them as inert objects that are just really destructive, but they do contain lots and lots of different types of nutrients, nutrients that are otherwise limiting that they stop growth in the oceans because they're just exhausted in the oceans. They're bringing this nutrient in as it's melting out because these nutrients come from the air and also from glaciers that feed into them. It's trapped and it's built

over thousands of years. So as it melts, it all melts into the ocean and providing the nutrients that particularly right at the base of the food web, the phytoplankton that need nutrients in order to grow, they were provided with all these nutrients that are melting out quite quickly, actually. And so creating these fantastic conditions for blooms of phytoplankton, which then feeds the wider food web through the zooplankton and then through the things that feed on them like fish and penguins and seals and whales, in fact. So it's creating actually a huge, almost an oasis in a desert, if you can imagine that, of this nutrient-fueled production.

So that's the fantastic thing that icebergs offer to the ocean. What does it mean when all the freshwater, because icebergs are made from freshwater, so what does it mean when all that freshwater ends up in the seawater? Yeah, well, we've been studying this. There was another iceberg maybe about five or six years ago now called A68A, and that fell apart just before it got to South Georgia. this there was another iceberg maybe about five or six years ago now called A68A and that fell apart just before we got to South Georgia and we had a research vessel in the vicinity of that and we looked at what this melting meant for how the the ocean is structured because what you have in

the ocean are different layers you have a surface water that overlays an intermediate water and then a deeper water and what that fresh water is doing is coming down. And we saw with our own research samples that this pushing down all these layers further down, deeper into the ocean. And so that changes the structure of the ocean. But one of the benefits of that is that all this carbon that's accumulated through the phytoplankton growth that's in the surface, that's being pushed down

deeper into the ocean, accelerated almost, and could potentially be accelerating what we call carbon sequestration, the movement of carbon away from the atmosphere through the sea surface and into the ocean interior. So that could be a positive process through the melting out and the pushing down of all the layers beneath through the fresh water

that's melting out from the iceberg. What happens now? I mean, is there's a possibility, like is this the final resting place for it, or is there the possibility like is this the final resting place for it or is there the possibility that chunks of it could break off and move further afield? Yeah I think we don't quite know yet. We know it's pinned on a certain corner of the iceberg and it's still rotating around where it's pinned. So it could rotate off and then spin off and then go off to the to the wider ocean probably to the warmer parts where it would rapidly melt or it could rotate off and then spin off and then go off to the wider ocean, probably

to the warmer parts where it would rapidly melt. Or it could stay pinned, it could just be pushed a little bit further along, not very far, but maybe just a little bit further in and then become completely stuck. And then there's going to be a slow or potentially fast melting process depending on the ocean temperatures around it. And that will have lots of chunks of ice which could surround South Georgia. And we'll have to wait and see if that happens because that could have quite a major effect on wildlife if that hangs around for another six months or so. Is this kind of a sign of things to come when you have icebergs of this size that calve off from Antarctica and float away?

Again, as people look at a changing climate, they wonder whether what we're seeing now perhaps could be something that we might see more of in future. Yeah, that's a really good question. So the modelers in our team and also in other research teams are predicting that the carving of icebergs definitely will accelerate as the globe warms and the movement of ice from these continental interiors like Antarctica and Greenland moves faster to the periphery from where these icebergs carve. That means we'll get lots more of these, well maybe not the size of this, but lots of other icebergs coming out from places like Antarctica and Greenland. So yeah, this could definitely be, you know, it's a good model,

this type of iceberg and other ones we've seen recently of things that might happen far more frequently going into the future of climate change continues at the rate that it does. Pete Just finally, I mean, the scale of this is getting a lot of attention, just how enormous this thing is, but some of what you've talked about is what's in it and the fact that there are questions that we still don't understand about its impact on the natural world when you're studying this I mean what to you is is most amazing about this thing that that That we're talking about the scale of it is one thing but what else it kind of turns your head. Yeah

Well, I'm a biologist and I love the things that grow around Icebergs the things that actually can grow inside the ice itself. We call it ice algae. And that's sort of is a whole new food web that we know so little about. And having these sort of things to study gives us incredibly important insights into how this can actually change our oceans. Because when these things melt out, it changes the community around it of all the other small organisms, both plants and animals. So yeah, we know so little about that because it's very hard to study icebergs. They're ephemeral things. They're not there all the time. We can't really base our expeditions around finding icebergs because they'll be gone before we even start. So these things are really not known,

and that's why it's so precious to be able to get these samples from icebergs just to understand a lot of the biology as well as the physics of how they change our oceans. This is so interesting, Corrine. Thank you very much for this. You're very welcome. Corrine Tarling is a research scientist with the British Antarctic Survey, currently aboard the RRS, Sir David Attenborough,

in the South Atlantic Ocean. For more CBC podcasts, go to cbc.ca slash podcasts.