No, The Gulf Stream Is Not Collapsing

11:45 minutes

Gulf stream. North Atlantic Drift. System of warm currents in the North Atlantic. 3d illustration.
An illustration of the North Atlantic part of the Gulf Stream, which is not the same as AMOC. Credit: Shutterstock

A sobering climate study came out this week in the journal Nature Communications. It suggests that a system of ocean currents—called the Atlantic meridional overturning circulation (AMOC)—could collapse sometime between 2025 and 2095, which could have dire climate consequences for the North Atlantic. 

SciFri director of news and audio John Dankosky talks with Swapna Krishna, a journalist based in Philadelphia, about what this means and what could be at stake. They also chat through other big science news of the week, including the detection of water vapor around a very distant star, a new image depicting the first detection of gas giants being formed around stars, a new theory for the origin of the world’s “gravity hole,” why the fuzzy asp caterpillar packs such a scary sting, and what scientists can learn from ticklish rats.

Segment Guests

Swapna Krishna

Swapna Krishna is a journalist based in Philadelphia, Pennsylvania.

Segment Transcript

JOHN DANKOSKY: This is Science Friday. I’m John Dankosky.

DIANA PLASKER: And I’m Diana Plasker. I’m SciFri’s Events Manager, and we’re excited to fill in for Ira this week. Later in the hour, looking back at a year since the Dobbs decision, and getting to know some parrots.

JOHN DANKOSKY: But first, the Supreme Court cleared the way for the 300-mile Mountain Valley pipeline to continue construction. This natural gas pipeline is highly contentious. It is supported by the Biden administration, by Congress, and a key player in this story– West Virginia Senator Joe Manchin. But environmental groups strongly oppose the giant project and say it threatens our water, our air, and our climate. We will keep following this story as it evolves.

In other climate change news today, a sobering study came out this week. Its author suggests that a system of ocean currents, called the Atlantic Meridional Overturning Circulation, could collapse sometime between 2025– that’s pretty soon– and 2095. So what exactly does this mean, and what is at stake if this system, known as AMOC, goes belly up?

Here with this story and other science news of the week is Swapna Krishna, freelance science writer and journalist based in Philadelphia, PA. Swapna, welcome back to Science Friday.

SWAPNA KRISHNA: Thank you so much.

JOHN DANKOSKY: So first of all, explain what exactly is AMOC and what does it do.

SWAPNA KRISHNA: OK, AMOC is a system of currents in the Atlantic Ocean. And basically warm water travels from tropical regions to the north, where it chills, and then it sinks, because cold water is denser than warm water. And then it moves back south and warms up again and rises. That’s the AMOC.

And it’s important to note that we’re not talking about the Gulf Stream here because a lot of people have gotten this confused. The Gulf Stream is a surface level current and it’ll basically exist as long as the Atlantic Ocean has water and the Earth rotates.

JOHN DANKOSKY: OK, so that’s not what’s falling apart. But scientists are saying it’s pretty sure that this larger system, this AMOC will collapse. How sure are they?

SWAPNA KRISHNA: So we aren’t sure, actually. The scientists behind the paper seem pretty convinced, but the larger scientific community is asking some questions. There’s generally agreement that AMOC is slowing down, but we’re not sure it’s on the verge of collapse, and especially not in two years.

This paper, it was in Nature Communications, and it used sea temperatures from 1870 as a proxy for the health of the AMOC current. Crews at sea actually would bring buckets of seawater on board and stick a thermometer in it to measure ocean temps back in the 1870s, and that’s how we have temperatures going back that far, which I think is pretty cool.

But the community at large isn’t convinced because they don’t know if sea temperatures are a good proxy for the health of AMOC. So we all agree it’s slowing down, but we don’t really know if it’ll actually collapse this imminently.

JOHN DANKOSKY: Yeah, I mean, I think one of the things that gets headlines, though, is what exactly is at stake if it does collapse. Maybe you can just take us through those doomsday scenarios.

SWAPNA KRISHNA: Yeah, it’s not as doomsday as you might think. It’s not great. The weather in Europe would get a lot colder. And the storm intensity and patterns would change on the US’s East Coast. And tropical regions would get even hotter, which nobody needs. And so there’d probably be some mass migration if this happened. So not the end of the world scenario, but generally not great.

JOHN DANKOSKY: Generally not great. Well, let’s keep talking about water, but we’ll talk about water in space. The JWST has found some evidence of water vapor very far away in outer space. Maybe you can tell us more about that.

SWAPNA KRISHNA: Yeah, so we found water vapor in a system called PDS 70 about 370 light years away. So this is a new system that’s in the process of forming. It has an inner ring of dust and gas, two gas giants, and then an outer ring of gas and dust. And those rings of gas and dust will probably eventually become planets. But the news here is we found water vapor in that inner ring.

JOHN DANKOSKY: Wow. So that’s pretty big news. How exactly do we know that water is there? And how do we know that it formed?

SWAPNA KRISHNA: So believe it or not, water does have an emission spectrum. Because it absorbs EM radiation, we can actually tell, thanks to telescopes like JWST, whether there’s water in a system. So I think that’s really cool.

But there’s two theories here as to how this might have formed. First, it could be happening on the spot. Hydrogen and oxygen could be colliding and forming water vapor.

The other theory is a little more complicated. Ice particles might be traveling from the outer part of the system where there’s ice into the inner part of the system. But that’s a really long way to travel. Think about ice traveling from Neptune to Earth. And we don’t really know what mechanism might cause that.

JOHN DANKOSKY: It’s super interesting. It feels like kind of a big deal. Can it tell us anything about how water might have formed on Earth?

SWAPNA KRISHNA: Yes. So the big question here is that these inner planets aren’t forming and this would be the habitable zone of that star. Earth is about 93 million miles away from the sun. This water vapor is within 100 million miles of the star.

So the question here now is will this mean that water will be available from the beginning to these planets? Because if that’s the case, what if water was available to the Earth from the very beginning, from our creation? It’s a really interesting question.

JOHN DANKOSKY: It really is. We’ve got some more exciting space news this week. And I know you’re excited about it. A new image tells us a bit about the formation of gas planets. What exactly does the photo look like, first of all?

SWAPNA KRISHNA: So this photo has a brilliant orange background of gas and dust. And it’s got these spiral-ish arms that are bigger than our solar system. And then there’s these blue clumps dispersed throughout the image kind of on top of it. And all of this will eventually become a planetary system.

JOHN DANKOSKY: So what exactly can we learn from this swirly image far out in space?

SWAPNA KRISHNA: So it’s actually a composite image taken with two different telescopes so we’re able to see matter in different kinds of light– orange is infrared, blue is from a radio telescope. What’s interesting is that these blue clumps of gas and dust are matter as big as planets. So that what we’re learning here is how gas giants like Jupiter might form.

JOHN DANKOSKY: How they might form. I mean, what do we know right now or what do we think we know about how gas giants form?

SWAPNA KRISHNA: Well, so there’s two major theories. The first is core accretion, which is basically when a collision of particles builds more and more mass until a planet forms. But this image is cool because it shows us evidence for the first time for the second theory, which is called gravitational instability. And this occurs when large swaths of material surrounding the star collapse into these blue clumps.

JOHN DANKOSKY: I want to head back to Earth quickly. And we’re going to head to the Indian Ocean for this next story, more specifically to the world’s gravity hole. Maybe you can explain what the gravity hole is, first of all.

SWAPNA KRISHNA: Yeah, this is not my favorite term, I’ll admit.


So there’s a weird spot in the Indian Ocean. It’s called the Indian Ocean geoid low. And at this spot, the Earth’s gravitational pull is actually lower than anywhere else. And the sea level is 328ft lower than surrounding areas. It’s like this hole in the ocean. It’s located off the tip of Southern India and it covers about 1.2 million square miles.

JOHN DANKOSKY: So how was this hole formed? Do we know?

SWAPNA KRISHNA: A group of Indian scientists theorized that about 140 million years ago, there was a gap between the Indian tectonic plate and the rest of Asia. It was basically an ancient ocean there that no longer exists.

So as that gap closed and the world formed the way we see it now, that oceanic plate may have sunk into the mantle. And that would have brought low density material up. And that would have spurred the formation of hot magma plumes rising up. And these plumes may be what created the gravity hole.

JOHN DANKOSKY: Oh, interesting. So how exactly did they figure this out?

SWAPNA KRISHNA: They used computer models going back 140 million years to see how something like this could happen. And they modeled the shift of magma inside the Earth’s mantle, and that’s the level below the crust, to try and figure out what might have led to this.

And they found in every simulation that they ran there were magma plumes when a geoid hole was created. But it’s not for sure– for example, these models didn’t predict the specific shape of this hole. But it’s a good start at least.

JOHN DANKOSKY: So we’ve been talking about some really big ideas of formation of planets and gravity holes. Let’s talk about smaller things. I want to talk about some critters before I let you go, especially a very strange caterpillar called the asp caterpillar. If you take a look at it, it kind of looks like a tiny toupee. Tell me what we know about them.

SWAPNA KRISHNA: Asp caterpillars are located in the Southern United States. And they look fuzzy and adorable, but stay away. They have a terrible, terrible sting.

JOHN DANKOSKY: A terrible sting. So is it like a spiky sting? What exactly is causing the sting?

SWAPNA KRISHNA: So they have hidden venomous spines that inject a poison. And it can hospitalize people. This pain has been described as akin to being hit with a baseball bat or breaking a bone.

JOHN DANKOSKY: So why exactly is it so painful, this cute little caterpillar?

SWAPNA KRISHNA: Scientists have identified a protein in the venom and that’s what makes its sting so painful. And what’s really interesting is actually how it behaves. I think this is really cool. It actually behaves like bacteria. The proteins bind to the cell and then the shape changes into a sort of doughnut. And then they punch their way into the cell. And that’s when scientists think that the pain signals are sent to the brain.

JOHN DANKOSKY: So what does this tell us? I mean, what does this teach us other than don’t touch this caterpillar?

SWAPNA KRISHNA: Yeah, right? What I think is really interesting about this is the way this kind of mutation must have formed. The transformer would have had to go through something very specific to be heritable or passed down to offspring. Bacteria normally just do like a horizontal gene transfer, which means those genes don’t get passed down.

So for this to have happened, the bacteria would have needed to specifically insert the DNA into cells that would become sperm and eggs. And it’s the only way it could have been passed on. And it’s uncommon for this to happen. So it’s actually very cool that scientists were able to identify this.

JOHN DANKOSKY: That is really cool. Let’s end on one more critter story, kind of a happy note here. It’s a study that came out just today. Researchers– they tickled rats to study their brains.


Tell us what’s happening here.

SWAPNA KRISHNA: I love this story. Researchers wanted to study if a play was centered in a certain area of a brain. So for this experiment, scientists let the rats run free for a few days and got them comfortable with their humans. And then once they were, they played kind of this chase the hand game where they would tickle the rats. And the scientists monitored the rats’ brains while they laughed, or, in this case, squeaked, because rats don’t really laugh.


JOHN DANKOSKY: So we assume that that stands in for a laugh, a little rat squeak. So what exactly do these giggling rats teach us?

SWAPNA KRISHNA: Well, it’s really important to laugh during play because it’s kind of what signals that people are enjoying themselves. And scientists suspected that there was something that regulated this behavior. And what they found was that there were strong neural responses in a part of the rat brain called the periaqueductal gray. And that’s where laughing and play is centered.

JOHN DANKOSKY: OK, so that’s where laughing and play is centered. What else do we know about this part of the brain?

SWAPNA KRISHNA: We know it plays a role in autonomic function. And humans have one as well in the midbrain.

JOHN DANKOSKY: Oh, OK. So I guess that this must teach us something important about, I don’t know, the importance of play.

SWAPNA KRISHNA: I think it teaches us that play is important. And more important than we realize, it’s probably underrated and it serves a way as to actually grow the brain in this case.

JOHN DANKOSKY: I honestly– one of the things I learned is I didn’t know you could tickle a rat.



JOHN DANKOSKY: Who exactly knew? It sounds to me like this story tells us that we should get out and play a bit this weekend. I want to thank Swapna Krishna, freelance science writer and journalist based in Philadelphia, Pennsylvania. So good to have you here.

SWAPNA KRISHNA: Thank you so much.

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About Rasha Aridi

Rasha Aridi is a producer for Science Friday. She loves stories about weird critters, science adventures, and the intersection of science and history.

About John Dankosky

John Dankosky works with the radio team to create our weekly show, and is helping to build our State of Science Reporting Network. He’s also been a long-time guest host on Science Friday. He and his wife have three cats, thousands of bees, and a yoga studio in the sleepy Northwest hills of Connecticut. 

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