This chart of ocean heat is terrifying

The warm waters along the Gulf Coast are part of what draws people to the region and its many beaches. But there is such a thing as too warm — and the Gulf of Mexico has reached that point.  

Take a look at the chart below. It shows how much heat there is in the ocean over time for the Gulf. The red line is 2024 and the blue line is the average over the last decade.

The Gulf is now the hottest it’s been in the modern record, according to Brian McNoldy, a climatologist at the University of Miami, who produced the chart. Taking a dip would feel like a bath: The average temperature of the surface is close to 90 degrees, according to recent measures of sea surface temperature. 

“This is out of bounds from the kinds of variability that we’ve seen in [at least] the last 75 years or so,” Ben Kirtman, director of the Cooperative Institute for Marine and Atmospheric Studies, a joint initiative of the University of Miami and the National Oceanic and Atmospheric Administration (NOAA), told Vox. “That can be scary stuff.”

These record temperatures are just one signal of a more widespread bout of warming across the North Atlantic that ramped up last year. It’s still not entirely clear what’s causing it, though scientists suspect a combination of factors including climate change — which raises the baseline ocean temperature — as well as lingering effects of El Niño, natural climate variability, and perhaps even a volcanic eruption. 

The temperature in the Gulf is ultimately only a handful of degrees warmer than the historic average. Yet as scientists are increasingly warning, those degrees matter — a lot. It’s not just sea life that’s at risk, but cities full of people. 

The double punch of extreme ocean heat

There are two major ways that a hot Gulf threatens coastal communities, and they both have to do with hurricanes. The first is straightforward: Hurricanes like heat. They need warm water, and the moist, rising air it produces. That air mingles with storm clouds and can eventually form a hurricane. 

Hotter water can lead to stronger hurricanes that accelerate faster, giving coastal regions less time to prepare. 

Now let’s return to that chart above. It’s not showing surface temperature, but the amount of heat energy measured across different layers of the ocean. It’s this energy that can fuel big storms, Kirtman said. Powerful winds stir up the ocean, bringing deeper, colder water to the surface. That can slow down a hurricane. But when the water is warm even below the surface, he said, then the hurricane can rapidly intensify — meaning, its wind speeds can increase by roughly 35 miles per hour or more in less than 24 hours. 

Then there’s the other problem: Hot water kills corals, which defend coastal communities from hurricanes. These natural structures are large enough to dampen waves that hit the shore, minimizing the threat of storm surge. (Enduring ocean heat causes polyps — the little animals that make up a piece of coral — to lose a type of symbiotic algae that lives inside them. Without the algae, the coral turns white, or “bleaches,” and can starve to death.)

In other words, a hot Gulf could produce monstrous, rapidly intensifying hurricanes while also weakening our natural defenses against them. Good stuff. 

This year has seen five named storms so far, including Hurricane Beryl — which rapidly intensified to become the earliest Category 5 storm on record. This is the kind of hurricane that scientists have been expecting as oceans warm. 

“We’re continuing to see the climatological hallmarks of an active season,” Matthew Rosencrans, the lead hurricane season forecaster at NOAA’s Climate Prediction Center, said in a statement earlier this month. “Sea surface temperatures remain abnormally high.” 

Hurricane season in the Atlantic typically peaks around September 10, according to NOAA, and the agency expects a total of 17 to 24 named storms — well above average, but perhaps also the new normal.

A weird cold spot that’s puzzling scientists

The Gulf, and the North Atlantic ocean more broadly, are unusually hot. That much is clear. But there’s also a strange blob of colder water around the equator, which has spurred conflicting, confusing headlines that suggest the Atlantic is cooling. 

The surface temperature in this stretch of ocean swung from exceptionally hot to unusually cool in a matter of months starting this spring, for reasons that scientists have yet to fully explain, according to Franz “Philip” Tuchen, an oceanographer at the University of Miami. The rapid change is “very unusual,” he told Vox. 

Yet this cooling is only in one area — somewhere between central Africa and Brazil — and it’s already fading. “It’s not the whole Atlantic, and it’s just a temporary cooling,” Tuchen said. 

Not only is the effect fading, but the blob lies below the “main development region” for hurricanes — the band of ocean where storms usually form. So it likely won’t have a large effect on hurricane season. That band, like the Gulf and much of the North Atlantic, is now very, very warm. And in the long term, barring a dramatic drop in greenhouse gas emissions, it will likely only get warmer.