On today's episode of the 5 Things podcast: Warming waters could lead to more hurricanes, dying coral and a collapsed Gulf Stream

A record 40% of the world’s oceans are experiencing marine heat waves, according to the National Oceanic and Atmospheric Administration (NOAA). This temperature shift is especially notable in the Gulf states and threatens the health of their oceanic ecosystems. It could also lead to an increase in hurricane activity and intensity and puts the Gulf Stream in danger of collapsing. What’s causing these marine heat waves and how worried should we be? We're joined by NOAA Chief Scientist Dr. Sarah Kapnick to help us dig into it. 

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Dana Taylor:

Hello and welcome to 5 Things. I'm Dana Taylor. Today is Sunday, August 20th, 2023.

10 days ago, the National Oceanic and Atmospheric Administration, or NOAA, revised its hurricane forecast to above normal due to record warm temperatures at sea surfaces. Roughly 40% of the world's oceans are experiencing marine heat waves, the most since satellite tracking started in 1991. This temperature shift is especially notable in the Gulf States - Florida, Louisiana, and Texas - hitting record highs this July. This is worrisome on multiple fronts, the health of those ecosystems, the hurricane season, and the impact of El Niño. What's causing these marine heat waves, and should we be worried? Here to help us dig into it, I'm now joined by Dr. Kapnick, Chief Scientist for the National Oceanic and Atmospheric Administration. Dr. Kapnick, thanks for joining me.

Dr. Sarah Kapnick:

Thank you for having me.

Dana Taylor:

Okay, so I'll start with the last part of that question and ask you to give us NOAA's definition of what a marine heatwave is.

Dr. Sarah Kapnick:

A marine heatwave is a heatwave that's happening in the ocean or any aquatic environment. So it's when you get temperatures that are above normal. And these events can last over a day, or several days, or even months.

Dana Taylor:

And by all accounts, waters in and around the Gulf States ... I'm in Florida. Louisiana, Texas, they've hit record highs this July. Temperatures we've seen have been in the 90s. So what impact might this have on the health of things like coral reefs and the ecosystems they support?

Dr. Sarah Kapnick:

Just like us when it gets hot, we get stressed. And what we're seeing in the ocean is that fisheries are being stressed by this heat. Especially coral reefs which are really susceptible to heat. They have this symbiotic relationship in their tissues where algae live in their tissues. And when they are hot for a prolonged period of time, and what we're seeing is over a week in many places, they expel that algae. And so the coral reefs lose the algae and their food source, which leads to what we call coral bleaching. So when you see the algae, it looks white because it's lost all of its algae. It's lost its food source. So when that happens, the coral tissues are really susceptible to disease, but they're also starting to starve. And so if the bleaching is prolonged for a prolonged period of time, that coral then begins to die.

Dana Taylor:

So are we seeing any of that yet?

Dr. Sarah Kapnick:

We are starting to see that in some of these regions in the Gulf and along the Caribbean where it is elevated warm temperatures of at least a week in some of these zones.

Dana Taylor:

And can the coral recover or is it too soon to tell?

Dr. Sarah Kapnick:

There are certain parts that are starting to have the bleaching, and so we will see if they recover based on what happens with the temperatures, and others may die because of this.

Dana Taylor:

Wow. So how is this impacting other fish and wildlife in and around the Gulf?

Dr. Sarah Kapnick:

So corals are critical. They're a fishery habitat where baby fish of all different types are born and get their food and then are able to grow. And so we'll see this in the coming months and years as that has an impact on fisheries of the fish that come there. They also remove the food for older fish. It harms fisheries in the corals, but then also around all those marine zones where you have the heat. It leads to fish that can swim away, will swim away. They'll go to deeper waters than move to different places to try and escape that temperature.

And when this also happens, it can affect loss of corals. It affects the tourism in those places where people like to go and see the corals, like to go diving. It also affects storm protection. Because the loss of corals leads to stronger storm action on the coast, which actually leads to erosion along the coast when you have those big storms with those waves coming in. Because the corals no longer act as a buffer as those waves come in.

Dana Taylor:

Okay, I'll get to storms in a little bit. I'm in Florida, so I have a lot of questions about that. But commercial fishing, that's a huge industry in the region. How do you anticipate warmer waters impacting the folks who work in that industry?

Dr. Sarah Kapnick:

So marine heat waves leads to changes in where the fish are distributed. It makes them move out of those zones and move for colder water. They're going to move poleward, they're going to move to deeper waters. This affects the ability then of fisherman to go find their fish. They have to move farther to be able to get to those fisheries that they're used to. So they're spending a lot of energy, they're spending costs on fuel to be able to get that, so that increases their costs. If they can't follow those fish, then they aren't catching the fish. And so that leads to collapses and problems in the fisheries. In previous years we've seen this. In 2013, 2017, when there was a marine heat wave in the Northeast Pacific, it upended the ecosystems. It led to fisheries collapse and it led to disaster declarations for many different types of fisheries.

Dana Taylor:

So let's talk about storms. Hurricanes notoriously feed off of warmer waters. We're a couple of months into the current hurricane season now. Is it raising the threat that we could see bigger and potentially more destructive hurricanes this year?

Dr. Sarah Kapnick:

When hurricanes form and they take their energy out of the ocean, the warm waters is what feeds the energy of those storms. If you get a storm and it goes over some of these warm waters, you can have growth, you can have strong storms forming from this. And actually we already have that into our calculations of our expectations for this hurricane season. And El Niño has been developing and has been declared in the Pacific. Normally during El Niño, we expect less storms in the Atlantic. However, because the waters were so warm, we put out our prediction of a average season with a 40% chance of a normal season and then 30% chance above or below as a result of these warm waters pushing the likelihood that we can actually form more storms.

Dana Taylor:

What I also wonder with a hurricane as it gets closer to the shore, if the waters are warm, are we going to see an intensification closer in?

Dr. Sarah Kapnick:

This does allow for intensification to happen as the storms come closer and with the warm waters. And to cause the damages of hurricanes, it really just takes one hurricane. And so we are watching it very closely as the season develops. If this marine heatwave continues over the coming months, particularly as we move into the typically most active part of the hurricane season which is coming later in August, September, that is what everyone will be looking at with concern about will happen with potential impacts of the U.S.

Dana Taylor:

What about hurricane speeds across land? When a hurricane moves slowly, it has an opportunity to dump more water over certain areas. Do warmer waters have any impact at all on speed?

Dr. Sarah Kapnick:

Warmer waters don't necessarily have an impact on speed. It depends on that gradient of those waters and how it alters the storm. It interacts with the physics of the storms. But what warmer waters can definitively do is provide an increased heat source for storms. And so it increases the potential that you can get stronger storms if they move over. And if they're moving over slowly, that allows them to extract much more energy out of the ocean and to become stronger.

Dana Taylor:

Let's talk about the elephant in the room. All of the other extreme weather that we've experienced nationally and globally this year already - record heat, droughts, fires, floods - do warmer waters play a role in those? And if so for each of them, how so?

Dr. Sarah Kapnick:

With all the warming that has been happening due to climate change, the ocean is taking up 90% of that excess heat and that excess heat is being circulated around the world and then coming back out into the atmosphere. And as storms pass over that water, they can increase the amount of water that's then being held in the atmosphere. That then increases the amount of rain that can happen from the storms. It also is altering our storm patterns around the world where those intensities are happening and where those storm tracks are occurring. And so it's having all of these knockout effects into the storms, into their strength.

Dana Taylor:

And globally, what other areas specifically are you seeing any trends where it's not like anything you've seen before?

Dr. Sarah Kapnick:

Particularly with this El Niño and this year, as we're looking at what looks like the next few months, normally during an El Niño, we have parts of the United States that are cooler than normal. But because of the warm waters in the ocean and because of the background warming that's happened worldwide, we're actually predicting for the next several months warmer than average temperatures over those months.

It's also fundamentally changing our expectations under an El Niño, what is going to happen in the U.S. in terms of temperatures. Also, due to this warming, it's increasing the ability of the air to hold more water. And so we're even seeing some of the predictions and some of the changes in precipitation. Normally as an El Niño develops, we should have some places that should start reducing in precipitation. And in some of those parts of the world, we're starting to see actually normal precipitation levels or precipitation happening at higher than average levels. And so this warmer water, warmer atmosphere is changing those responses to El Niños in ways that we haven't necessarily seen in the past, previous strong El Niños as they've developed.

Dana Taylor:

One theory bouncing around on the internet has to do with a change made by the International Maritime Organization back in 2020 when it started requiring ships to drastically reduce the sulfur content in their fuel. This may have led to less pollution over the world's oceans, but it may also have had an unintended effect of letting more sunshine heat our oceans. And since pollution does tend to block the sun, is there any merit at all to that argument?

Dr. Sarah Kapnick:

That is a contributing factor. We're also looking at dust coming off of Africa, and those values have been lower over the last few months. We're also looking at trade winds that typically cool the tropical Atlantic and are through latent heat release and they cool as they go over the water. We're also seeing that those are weaker in our observations. And so I think it's a confluence of these different factors plus the ocean taking up the heat that is leading to this. There will be numerous studies that will come out to try and ascertain what was critically causing this heat wave. It may be a connection of many of those things adding up together to seeing the extremes that we are seeing, plus a little bit of natural variability also making the likelihood of a marine heat wave happen. However, the strength, the duration, the severity, the statistics, probabilities of that are all pushed by climate change.

Dana Taylor:

So globally, what other areas of water is NOAA most worried about and why?

Dr. Sarah Kapnick:

We're looking at waters everywhere. They are all uniquely changing. No place is left untouched by this. And particularly in the U.S. with marine heat wave that's happening, we're really concerned right now about those corals and what's happening with the corals.

Dana Taylor:

I just think it's so interesting that that's the first domino that falls, and we can track it from there, how things are going.

Dr. Sarah Kapnick:

Yes, we can look at these things from space. We can look at them up close as we're going into those local places with the sensor technology that we have, with the monitoring systems that we have. So we're monitoring this all around the world and in key places in the United States.

Dana Taylor:

What will it take to get the water temperatures back to normal? Are we just waiting for colder weather to come, or could this be a longer term phenomenon that impacts the Gulf and all of us who depend on that ecosystem long-term?

Dr. Sarah Kapnick:

This is a heat wave. Heat waves end eventually. It ends by either the cooling for the natural season as we go into winter when the cooling starts to begin. It also will occur during the season if there's more enhanced mixing of the ocean from the lower levels into the top layers. And also if we start getting these trade winds going again, it'll help cool off.

So we'll see with this heat wave, it will break eventually. But we are moving towards a hotter future and the temperatures of the ocean are increasing every single year over year. And that will continue until emissions no longer accumulate in the atmosphere.

Dana Taylor:

What keeps you up at night, Dr. Kapnick? And what gives you the most hope?

Dr. Sarah Kapnick:

What keeps me up is am I doing enough and can we do more and trying to figure that out. And what gives me hope is the amazing science and technology that we have to deal with the problems that we have today and the amount of science we have, that we know what will happen in the future. And so if we take that information and we make it actionable towards climate solutions, towards building resilience and adaptation, we can reduce these impacts. We can reduce the costs, we can reduce the impacts on society and ecosystems, but we just need to act on all that information that we have.

Dana Taylor:

Thank you so much for your time and for joining me today, Dr. Kapnick.

Dr. Sarah Kapnick:

Thank you for having me.

Dana Taylor:

Thanks to Cherie Saunders for her production assistance. Our senior producer is Shannon Rae Green, and our executive producer is Laura Beatty. Let us know what you think of this episode by sending a note to [email protected]. Thanks for listening. I'm Dana Taylor. Taylor Wilson will be back tomorrow morning with another episode of 5 Things.