Sea Camp: Why Are Ocean Currents Shifting?

Summary

Short Wave Podcast Summary: Sea Camp – Why Are Ocean Currents Shifting?

Published on July 7, 2025

Hosts: Emily Kwong and Regina Barber
Producer: Hannah Chen
Special Guests: Matt Luongo (Climate Scientist and Physical Oceanographer), Lynn Talley (Professor at Scripps Institution of Oceanography), Shangfeng Xie (Climate Scientist and Oceanographer)

---

Introduction to Sea Camp

In the premiere episode of "Sea Camp," a special series from NPR’s Short Wave, hosts Emily Kwong and Regina Barber embark on an eight-week exploration of the ocean's depths. This inaugural episode, titled "Why Are Ocean Currents Shifting?" sets the stage by examining the intricate relationship between the ocean and the atmosphere and the profound implications of shifting ocean currents in the context of a warming planet.

Understanding Ocean Currents

Hannah Chen, the episode's producer, introduces the fundamental concepts of ocean currents:

“Ocean currents are the continuous movement of water within the ocean along a particular path... they affect fish migration, distribute heat and nutrients which support ecosystems, help drive weather, and shape human travel.”
(04:04)

Matt Luongo elaborates on how the ocean moderates climate, particularly along the U.S. west coast:

“Anyone who lives along the west coast of the U.S. for instance, knows that we have really mild winters, and that's a result of the fact that we have the ocean kind of mediating the weather there.”
(01:15)

Regina Barber reflects on the personal connection to this phenomenon:

“Yeah, I mean, I grew up in Washington State and California. And he's right. Like, we do have very mild winters, but I never, like, put together. It's because of the Pacific Ocean.”
(01:38)

Historical Insights: Benjamin Franklin and the Gulf Stream

Hannah Chen introduces Lynn Talley, a professor at the Scripps Institution of Oceanography, who shares a fascinating historical perspective:

“One of the oldest ocean current maps we have comes courtesy of Benjamin Franklin.”
(04:42)

The discussion reveals how Benjamin Franklin’s cousin, a whaling captain, leveraged knowledge of the Gulf Stream to expedite mail delivery across the Atlantic:

“He noticed that his cousin in Rhode island, who was a whaling captain, could get across the Atlantic Ocean a whole lot faster than the British official postmaster ships. And that's because his cousin in Rhode island knew about the Gulf Stream.”
(05:22)

Emily Kwong highlights the significance of the Gulf Stream:

“Because the Gulf Stream... it's like, a perfect route if you want to cross the Atlantic.”
(05:49)

Remarkably, a 1978 discovery showed that Benjamin Franklin's map of the Gulf Stream remains accurate today, underscoring the stability of these surface currents over centuries:

“The map was so accurate, and it was exactly where it is now.”
(06:33)

Hannah Chen summarizes:

“These surface currents remain so consistent over time... the main envelope, she called it, that Benjamin Franklin drew, is basically the same map as what we use now.”
(06:40)

Driving Forces Behind Surface Currents

The conversation shifts to the mechanics that sustain ocean currents. Hannah Chen outlines several factors:

“There's temperature, there's salinity, coastlines, overall, global wind patterns... even the rotation of the Earth can drive these currents because of something that's called the Coriolis effect.”
(07:12)

Regina Barber further explains the Coriolis effect:

“Because the Earth is spinning, it affects air currents. So, like, this makes air flow, like, slightly deflect to the right in the northern hemisphere, and it slightly deflects to the left in the southern hemisphere, and it makes these, like, curved paths of air. And this, in turn, like, affects the ocean currents.”
(07:24)

Matt Luongo emphasizes the dominance of wind-driven surface currents:

“The surface currents are primarily driven by winds... the Gulf Stream, the California Current, the Kuroshio... these kind of wind driven surface currents.”
(07:49)

The Impact of Climate Change on Ocean Currents

Hannah Chen introduces Shangfeng Xie, who discusses recent research on how a warming climate is influencing ocean currents:

“In a warming climate, surface currents across the globe will significantly accelerate.”
(08:15)

Regina Barber probes further:

“Like, will they speed up everywhere?”
(08:35)

Hannah Chen clarifies:

“In more than three quarters of the world's oceans, yes. But the surface currents specifically, not the deep ocean ones.”
(08:37)

Using the analogy of an outdoor swimming pool, Hannah explains:

“It'll take a really long time for the deep ocean to warm, but the top layer is warming much faster.”
(09:26)

As the surface water warms, it expands and creates greater pressure differences, speeding up the surface currents:

“As this surface water warms, its molecules move faster and further apart. Meaning that it's all going to take up more space. That'll result in intensified pressure differences, basically pushing parts of the ocean, like the currents at the surface, to move faster.”
(09:34)

This acceleration is already observable. For instance, the Antarctic Circumpolar Current has sped up over recent decades:

“...the Antarctic Circumpolar current... it's sped up significantly over the past few decades.”
(09:56)

Consequences of Shifting Currents

Shangfeng Xie discusses the ecological ramifications:

“Fish definitely is going to tell the difference... their migration, spawning and feeding... phytoplankton. And also the fish migration is certainly going to change tremendously.”
(10:22)

Hannah Chen adds that accelerating currents may alter their paths and impacts:

“As these currents speed up, they could end up shifting their location and their effects as well.”
(10:55)

Shangfeng Xie explains:

“When the currents speed up, they're going to move nutrients, they're going to move heat. If you speed a current up, it might not want to stay where it started. It might try to push itself a little farther towards the pole, and it will carry things farther and faster.”
(11:16)

The Atlantic Meridional Overturning Circulation (AMOC) Exception

While most surface currents are accelerating, the AMOC, a crucial system for global heat redistribution, is an exception. Hannah Chen describes AMOC:

“It's a system of surface currents and deep currents, kind of like an Atlantic Ocean current conveyor belt that moves warm water north and cold water south.”
(11:16)

Shangfeng Xie highlights concerns about AMOC:

“It... helps redistribute energy and kind of moderate heat around the world.”
(11:27)

Hannah Chen shares alarming projections:

“For decades, scientists have been worried that it's begun to slow down. And Xiaoping's team's models supported this. They said that along with multiple currents in the deeper ocean, it'll continue to decelerate, which could change a whole host of things... sea level rise along north part of the East Coast, Western Europe and a lot of the Northern Hemisphere way colder or change monsoon season and rainfall near the equator...”
(11:41)

Call to Action: Addressing Climate Change

Emily Kwong underscores the urgency:

“Like a choose your own adventure game, but bad.”
(12:20)

Hannah Chen reinforces the gravity of the situation:

“But unlike a choose your own adventure game where you can restart it whenever, we humans only get one shot.”
(12:22)

Matt Luongo emphasizes the need for immediate action:

“We understand a lot of the basic building blocks. So I think it then becomes kind of a political and social decision on how much we want to not emit CO2, for instance. It's kind of what we decide to do.”
(12:36)

Closing Remarks

Emily Kwong and Regina Barber thank Hannah Chen for her insightful contributions, setting the stage for the subsequent episodes in the "Sea Camp" series. The hosts highlight the importance of understanding and addressing the shifting ocean currents to mitigate potential climate disasters.

---

Conclusion

This episode of Short Wave's "Sea Camp" provides a comprehensive exploration of ocean currents, their historical significance, the driving forces behind them, and the profound impacts of climate change on these vital systems. Through expert insights and engaging narratives, Emily Kwong and Regina Barber underscore the interconnectedness of the ocean and the atmosphere, emphasizing the urgent need for collective action to preserve the planet’s climatic balance.

---

Notable Quotes:

• Matt Luongo (01:15): “Anyone who lives along the west coast of the U.S. for instance, knows that we have really mild winters, and that's a result of the fact that we have the ocean kind of mediating the weather there.”

• Shangfeng Xie (10:22): “Fish definitely is going to tell the difference... their migration, spawning and feeding... phytoplankton. And also the fish migration is certainly going to change tremendously.”

• Hannah Chen (09:34): “As this surface water warms, its molecules move faster and further apart. Meaning that it's all going to take up more space. That'll result in intensified pressure differences, basically pushing parts of the ocean, like the currents at the surface, to move faster.”

• Matt Luongo (12:36): “We understand a lot of the basic building blocks. So I think it then becomes kind of a political and social decision on how much we want to not emit CO2, for instance. It's kind of what we decide to do.”

---

References:

• Sea Camp Series: An eight-week deep dive into oceanography, exploring various aspects of marine science and the critical role oceans play in Earth's climate system.

• Physics Behind Currents: Understanding the Coriolis effect and its influence on both atmospheric and oceanic circulation patterns.

• Historical Maps: The enduring accuracy of Benjamin Franklin’s Gulf Stream map as evidence of the stability of major ocean currents over centuries.

---

Note: This summary encapsulates the key discussions and insights presented in the "Sea Camp: Why Are Ocean Currents Shifting?" episode of NPR's Short Wave, providing a clear and comprehensive overview for listeners and non-listeners alike.

Transcript

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[Emily Kwong]

You're listening to shortwave from npr.

[Regina Barber]

Hey, shore waivers. It's Regina Barber and Emily Kwong, and we are excited to announce the launch of Sea Camp.

[Emily Kwong]

Every Monday for the next eight weeks, we'll be traveling deeper and farther into the depths of the ocean, from the sunlit zone to the twilight zone to the sea floor. And we're going to start today right on the surface. Sitting beside us on a metaphorical boogie board is producer Hannah Chen.

[Hannah Chen]

Hannah. Hi, Hannah. Hi, Emily. Hi, Gina. Today we're focused on how the atmosphere and the ocean affect each other. I gotta say, though, even though I grew up on the west coast going to the ocean every summer, hunting in tide pools, watching sea lions, I didn't realize until recently that that same ocean is also constantly affecting how we experience life on land.

[Matt Luongo]

Anyone who lives along the west coast of the U.S. for instance, knows that we have really mild winters, and that's a result of the fact that we have the ocean kind of mediating the weather there.

[Hannah Chen]

So this is Matt Luongo. He's climate scientist and a physical oceanographer at the University of Washington in Seattle.

[Matt Luongo]

In the Northern Hemisphere, the weather moves from the west to the east, and they're pretty strongly moderated by the ocean.

[Regina Barber]

Yeah, I mean, I grew up in Washington State and California. And he's right. Like, we do have very mild winters, but I never, like, put together. It's because of the Pacific Ocean. Yeah.

[Emily Kwong]

And, you know, when I think of the ocean and the atmosphere, I also think about humans have trapped on Earth with greenhouse gases, heat, and that heat is getting absorbed by the ocean. Like, if oceans didn't exist, climate change would have cooked us a long time ago.

[Hannah Chen]

Totally. And I think it's easy to be like, oh, like, great, the ocean saved us. We're fine. But, Emily, all that heat in the atmosphere is still slowly affecting the ocean surface. And scientific models are indicating that these surface level changes, that heat could have big, lasting effects on the ocean's currents, their location, their stability, as well as on this kind of feedback loop of ocean atmosphere interaction.

[Regina Barber]

So today on the show, we're talking about the surface of the sea and the complex movements of the currents in.

[Emily Kwong]

It, how those currents are shifting in response to a warming planet, and why.

[Regina Barber]

That might spell disaster.

[Emily Kwong]

You're listening to Shortwave, the science podcast from npr.

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[Regina Barber]

Okay, Hannah, let's start with, like, what are ocean currents and why are they important?

[Hannah Chen]

Yeah. So ocean currents are the continuous movement of water within the ocean along a particular path. So they can be deep and they can be shallow. They're kind of like rivers and streams, but they're winding through the ocean instead of the land, and they're taking things with them. They affect fish migration. They distribute heat and nutrients which support ecosystems. They help drive weather. And these surface currents can help shape human travel, which is why sailors have been mapping the surface currents of the ocean for a long, long time.

[Shangfeng Xie]

People have needed to know surface currents ever since they were sailing, you know, back in, you know, thousands of years ago. It's very, very important for navigation.

[Hannah Chen]

This is physical oceanographer Lynn Talley. She's a professor at the Scripps Institution of Oceanography at the University of California, San Diego. She told me that one of the oldest ocean current maps we have comes courtesy of Benjamin Franklin.

[Emily Kwong]

The Benjamin Franklin, of course.

[Regina Barber]

Like, he did so many things.

[Hannah Chen]

Yeah. Turns out in addition to being an inventor and a scientist and a diplomat, he also the postmaster general of Philadelphia.

[Shangfeng Xie]

He opened a post office in Philadelphia, and that was to get the mail back and forth between England and Philadelphia.

[Hannah Chen]

Wow. Airmail was not an option at the time. So all these letters had to come via boat over the Atlantic Ocean.

[Shangfeng Xie]

He noticed that his cousin in Rhode island, who was a whaling captain, could get across the Atlantic Ocean a whole lot faster than the British official postmaster ships. And that's because his cousin in Rhode island knew about the Gulf Stream.

[Emily Kwong]

Because the Gulf Stream, Right, that's that big current that flows from the Gulf of Mexico and goes north along the eastern coastline and then towards northern Europe. It's like, a perfect route if you want to cross the Atlantic.

[Hannah Chen]

Yeah. And it's also a huge feeding ground for whales, which is probably why Benjamin Franklin's cousin knew about it. And at the time, the average postal ship took two weeks longer to cross the Atlantic Ocean than Benjamin Franklin's cousin, the whaling captain, did, because the postal ship wasn't taking advantage of the Gulf Stream.

[Regina Barber]

This is so fascinating. It's kind of like Benjamin Franklin's cousin was, like, standing on an escalator, just, like, relaxing. And the other guy, this other ship, was trying to go down the up escalator. It's not even a race at all.

[Hannah Chen]

Not a fair race. No. And get this. In 1978, a scientist from the Woods Hole Oceanographic Institution found several copies of Ben Franklin's Gulf Stream map. And. And he realized nothing had really changed.

[Shangfeng Xie]

And he went, oh, my goodness. Because the map was so accurate, and it was exactly where it is now.

[Emily Kwong]

Oh, so she's saying the Gulf Stream was the same as it was in the 1760s?

[Hannah Chen]

Yeah, basically the same. And that's partially because these surface currents remain so consistent over time. Lynn told me they can meander back and forth a little. They're not set in a stream bed or a riverbed the way that our currents on land are. But this main envelope, she called it, that Benjamin Franklin drew, is basically the same map as what we use now. Hmm.

[Regina Barber]

That is so cool. Wait, Hank, can you tell us, like, what's driving these surface currents? Like, what exactly in the ocean is keeping them going?

[Hannah Chen]

Yeah, it's really a number of things. There's temperature, there's salinity, coastlines, overall, global wind patterns. Like, even the rotation of the Earth can drive these currents because of something that's called the Coriolis effect.

[Regina Barber]

Good old Coriolis effect. I remember my students, like, hating this subject. Okay, so because the Earth is spinning, it affects air currents. So, like, this makes air. Air flow, like, slightly deflect to the right in the northern hemisphere, and it slightly deflects to the left in the southern hemisphere, and it makes these, like, curved paths of air. And this, in turn, like, affects the ocean currents.

[Hannah Chen]

Yeah, exactly. And that's essentially what Lynn and Matt told me too.

[Matt Luongo]

The surface currents are primarily driven by winds. So those are really the. The currents that we know and love and we See, you know, these are the Gulf Stream, the California Current, the Kuroshio. And the things that we see day to day, that we think about with currents are really these kind of wind driven surface currents.

[Hannah Chen]

For a long time, these wind driven surface currents have stayed pretty consistent, but now they're changing.

[Shangfeng Xie]

Why?

[Emily Kwong]

Is it us? Is it climate change?

[Hannah Chen]

Okay, so the scientist you're going to hear from next is Shangfeng Xie. He's a climate scientist as well as an oceanographer. And a few years ago, he and his team did a study using predictive models to show that in a warming climate, surface currents across the globe will significantly accelerate.

[Regina Barber]

Like, will they speed up everywhere?

[Hannah Chen]

In more than three quarters of the world's oceans, yes. But the surface currents specifically, not the deep ocean ones.

[Regina Barber]

This is because of, like, heat transfer, right? Like, heat doesn't go through water very quickly. Again, I'm gonna push more physics. I'm so sorry.

[Hannah Chen]

No, it's not. No, I love physics. That's right. It's kind of like. I don't know if either of you have ever been to an outdoor swimming pool in the summer. Yes, Xiangping told me it's kind of like that.

[Unknown]

If you swim during the sunny afternoon in summer, you will feel like the surface water is a lot warmer than below.

[Regina Barber]

It's definitely bringing me back to, like, swim team. Like, if you're swimming along the surface, it's going to be pretty warm. You go even just a little bit, it's going to be cooler. But if you sit on the bottom, it's pretty cold.

[Hannah Chen]

Yeah, exactly.

[Emily Kwong]

But Hannah, our ocean is so much bigger than a swimming pool. So how does this apply to us on planet Earth?

[Hannah Chen]

Well, it's kind of the same idea that it'll take a really long time for the deep ocean to warm, but the top layer is warming much faster.

[Unknown]

The ocean is a layer of warm water floating over a body of deep cold water.

[Hannah Chen]

And as this surface water warms, its molecules move faster and further apart. Meaning that it's all going to take up more space. That'll result in intensified pressure differences, basically pushing parts of the ocean, like the currents at the surface, to move faster.

[Emily Kwong]

Oh, that's why you said earlier so many surface currents are expected to speed up.

[Hannah Chen]

Exactly. And this is already happening. For example, scientists know from satellite measurements and observational floats that the Antarctic Circumpolar current, which is the eastward ocean current kind of encircling Antarctica, it's sped up significantly over the past few decades. And Xiaoping said this overall acceleration could really change Ocean life as we know it.

[Unknown]

Yeah. So fish definitely is going to tell the difference because, you know, a lot of fish, they migrate, spawning and feeding and the nursery grounds. So they rely on the kind of a temperature structure. So phytoplankton. And also the fish migration is certainly going to change tremendously.

[Hannah Chen]

And it's not just fish and plankton. Lynn told me that as these currents speed up, they could end up shifting their location and their effects as well.

[Shangfeng Xie]

When the currents speed up, they're going to move nutrients, they're going to move heat. If you speed a current up, it might not want to stay where it started. It might try to push itself a little farther towards the pole, and it will carry things farther and faster.

[Hannah Chen]

There is one key exception to this overall surface acceleration trend, and that's the amoc. Okay, so this stands for the Atlantic Meridional overturning Circulation.

[Shangfeng Xie]

Cool.

[Hannah Chen]

And it's a system of surface currents and deep currents, kind of like an Atlantic Ocean current conveyor belt that moves warm water north and cold water south. And this helps redistribute energy and kind of moderate heat around the world.

[Regina Barber]

Got it. Okay, so what's happening to the amoc, right under climate change?

[Hannah Chen]

Well, for decades, scientists have been worried that it's begun to slow down. And Xiaoping's team's models supported this. They said that along with multiple currents in the deeper ocean, it'll continue to decelerate, which could change a whole host of things. It could increase storm severity and cause sea level rise along north part of the East Coast. It could make Western Europe and a lot of the Northern Hemisphere way colder or change monsoon season and rainfall near the equator, scientists don't know all of the potential effects yet.

[Emily Kwong]

That's like a choose your own adventure game, but bad.

[Hannah Chen]

Yeah, but unlike a choose your own adventure game where you can restart it whenever, we humans only get one shot. And for Matt Luongo, who's the oceanographer you heard from at the beginning of this episode, the that means we should act now so that we can curb this climate disaster.

[Matt Luongo]

We understand a lot of the basic building blocks. So I think it then becomes kind of a political and social decision on how much we want to not emit CO2, for instance. It's kind of what we decide to do.

[Hannah Chen]

Yeah.

[Emily Kwong]

Hannah, thank you so much for bringing us this story and kicking off Sea Camp at the surface, but with great depth.

[Regina Barber]

Oh, no problem.

[Hannah Chen]

Thanks for having me. And good luck with the rest of Sea Camp.

[Regina Barber]

Thanks, Hannah.

[Emily Kwong]

This episode was produced by Hannah Chin and Rachel Carlson. It was edited by our showrunner, Rebecca Ramirez, and fact checked by Tyler Jones. Jimmy Keeley was the audio engineer, Beth.

[Regina Barber]

Donovan is our senior director and Colin Campbell is our senior vice president of podcasting strategy. I'm Regina Barber.

[Emily Kwong]

I'm Emily Kwong.

[Regina Barber]

Thank you for listening to Short Wave and Sea Camp from NPR.

[Hannah Chen]

Foreign.

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