TIL about the changing ocean (part 1)

Hello and welcome to Today I Learned Climate. I'm your host, Lar Hesse-Fisher of the MIT Environmental Solutions Initiative. And this is our first episode of season four. And we have some great topics coming up this season. We'll be covering electric cars and hydrogen technology and much more. But today, we're going underwater to talk about the ocean.

Okay, so quickly, the accelerated climate change that we're experiencing today is mostly caused by humans adding a lot of extra carbon dioxide, CO2, to the atmosphere. since we started burning a lot of fossil fuels in the mid-1700s. And that extra CO2 is acting like a blanket around our planet, warming up the Earth. So we heard this startling figure about the ocean that maybe you've heard too. It's estimated that the ocean has absorbed about one third of that extra CO2. And that the ocean...

has absorbed more than 90%, 9-0% of this extra heat. So first, those are startling figures. They also open up a lot of questions, like... How does the ocean absorb all that CO2 and heat? And why does this matter? And what does it mean for the health of the ocean and the planet? We were really excited to be able to dig into all of this with Dr. Sylvia Earle, who may have the coolest title ever. I'm Sylvia Earle, explorer at large at the National Geographic, founder of Mission Blue.

Basically an oceanographer, and like other scientists, an explorer. Dr. Earle has a lifetime of experience studying the ocean. Since the 1950s, when I first had a chance to breathe air underwater, I've been privileged to have thousands of hours, not just diving using scuba, but living underwater.

Ten times. I've used dozens of little submarines, more than 30 different kinds, to go deeper in the ocean than you could go holding your breath or even using scuba. And during all that time she spent studying the ocean...

She saw what an enormous role it plays in how our planet functions and how it's changing. She's going to help us explain all of that. I think we should just dive in. From space, Earth looks blue. Earth is dominated by the existence of the ocean. Yeah, the ocean covers more than two-thirds of our planet. mysterious and maybe scary expanse, with not a lot going on compared to land. But the health of the ocean affects all of us. I think it's important to recognize that...

The ocean is the basic system that drives climate. Without the ocean, what we think of as climate could not exist. The ocean helps regulate Earth's rain and snow. produces most of the oxygen that we breathe, and affects the Earth's temperature. One thing we learned while making this episode is that it is an incredibly complicated system, with so many factors constantly at play.

gases are going in and out of the ocean, the temperature shifts at different layers and pockets of water, currents bring streams of water and sea life all around the world, storms come along and mix everything up. It's a lot to keep track of and explain. So today we're going to focus on just two of those factors that are essential when talking about the ocean and climate change. If I were an alien...

And I wanted to make life on Earth change, make it difficult for those pesky humans. I would do two things. I'd change the temperature and I'd change the chemistry of the planet. And we're doing that. We're changing the temperature. And we're changing the chemistry. And because there is so much to cover, we're going to do it in two episodes. This one is about humans changing the chemistry of the ocean. And the next one will be about the effects of rising temperatures.

So let's start with chemistry. Humans have introduced more carbon dioxide into the atmosphere, which is making our planet warmer. To understand what all this extra CO2 that we've added to the atmosphere is doing to the ocean... We need to start with a couple of minutes on something called the carbon cycle. The carbon cycle is a living cycle. Economists follow the money. They want to know how the world works.

From an economic sense, scientists follow the carbon when they want to know how does the world work? How does the climate work? The carbon cycle is all about how the element carbon... flows through our planet from the atmosphere to the ocean and life on land into soils and rock and back up into the atmosphere. The ocean...

takes in and stores carbon in two main ways. First, CO2 from the air dissolves into the water, where it goes through a series of chemical reactions and ends up in a few different forms, mostly as bicarbonate. but also a bit as carbonic acid, carbonate, and even just dissolved CO2, like in sparkling water. Yeah, the ocean is actually very slightly carbonated. And here is the second way.

In the ocean, the heavy lifting is done by photoplankton capturing the carbon through a process called photosynthesis. A quick refresher on photosynthesis. as well as other organisms like phytoplankton, pull carbon from the air or water and use it to build their trunks, leaves, roots, bodies, etc. You can probably visualize that process on land through trees.

And it's also happening in the ocean on a huge scale. In every cup full of water, you've got literally millions of organisms, tiny creatures so small. that they're not visible and curiously some creatures that are very much linked to the carbon cycle were not even discovered until 1986 by the scientist at MIT, Penny Chisholm.

because they are so small. And they are the basis of much of the food chain in the ocean. And the carbon doesn't just stay with the phytoplankton. The carbon is consumed by zooplankton. consumed then by larger organisms. Small fish eaten by larger fish and so on up the food chain. So the connection between great whales and carbon starts with...

photosynthesis, just as on the land. So those phytoplankton are pulling in carbon and turning it into food for other life in the ocean. Then life in the ocean does what all life eventually does. When it dies, it tends to either be consumed by some other organisms, but eventually it goes to the bottom of the ocean. There's this snow of life that ultimately...

is sequestered in the deep sea. It's where most of the carbon on the planet actually is. And some of it becomes limestone, calcium carbonate. The carbon is held in the rocks, in the sediments in the deep sea. That's where the great carbon deposits are. If you were to dive down to the deep sea floor and look around, you would see a mix of rocks, minerals, and a slow flurry of decomposing pieces of plants and animals. All of that holds carbon in the ocean over millions of years.

And in this way, the ocean functions as a huge carbon storage space, kind of like a bank vault, a metaphor you might remember from our episode on forests. And it keeps a lot of carbon out of the atmosphere. Now, it's important to mention that some of that carbon gets re-released from the surface of the water back up into the air, kind of like when soda goes flat.

Now before humans started burning a lot of fossil fuels and cutting down forests, this was pretty much in balance. I mean, the ocean and the atmosphere pretty much exchanged the same amount of carbon. But this has changed. The concentration of CO2 in the atmosphere has gone up. And so on the whole, the ocean is now actually taking in more carbon than it emits.

The ocean will take carbon dioxide up, but it doesn't remain as CO2. It becomes carbonic acid, which is changing the chemistry of the ocean, the pH of the ocean, more acidic. This is the acidification issue that is in the minds of some, the evil twin of climate change. We're already seeing this ocean acidification. happening today. Since humans started burning a lot of fossil fuels a couple hundred years ago, the ocean has gotten 30% more acidic.

This can make it harder for some snails, as well as oysters and clams, to build their shells, and for corals to build their skeletons. Scientists will be the first to admit that they don't... really understand what this is going to mean for the vast amount of life in the ocean. Every living thing kind of reacts a little differently to acidification.

But a lot of these organisms that we just talked about are a critical part of the marine food web. And billions of people rely on ocean life as their main source of protein and for their livelihoods. And so in that lab and in the ocean, scientists are measuring the effect of ocean acidification. And we have some resources in our show notes if you want to learn more about acidification and its current and potential impacts.

Okay, so all of this extra CO2 is having an impact in the ocean in and of itself. But CO2 is a heat-trapping gas that's also warming up the planet. And that extra heat... also affects the ocean. So in our next episode, we'll cover how the rising temperatures of climate change are affecting the ocean and some cool technology that's helping scientists better understand what's going on.

Keep listening for what's next. Today I Learned Climate is produced by the MIT Environmental Solutions Initiative. Our editor and producer is Dave Leshansky. Our associate producer is Erin Kroll. Natalie Jones is our script writer for these two episodes. Alana Hirschfeld is our production assistant. Sylvia Scharf is our climate education specialist.

Carolyn Shea was our fact checker. Our music was by Blue Dot Sessions. Our artwork is by Erin Kroll. And I'm your host and producer, Lar Hesse-Fisher.