How is it possible that the ocean water is suddenly so much warmer than normal? Experts have been considering this question for a year now. Researchers now know what could not have caused it, such as El Niño or a volcanic eruption. But what is it?
It is a graph that has been frequent for months https://twitter.com/EliotJacobson/status/1785329869737644219as yesterday by an emeritus professor of mathematics and computer science.
“Breaking News,” wrote Eliot Jacobson. After 420 consecutive days of record high temperatures in the North Atlantic, temperatures fell below the 2023 record on April 29. The graph below shows the orange and red lines respectively:
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To be precise, it was a drop from 20.89 to 20.83 degrees. So it is not breaking news at all, says oceanographer Femke de Jong of the Royal Netherlands Institute for Sea Research (NIOZ). And not good news either.
“It is 0.06 lower than 2023, and those were already ridiculously high temperatures. The news is that the water has been this warm for a year.”
Half degree
Just to be clear: this concerns the temperature of the upper part of the ocean. This is quite easy to measure with satellites.
Last year we also wrote about the high sea temperature, specifically that of the North Atlantic Ocean. The temperature at that time was half a degree warmer than ever measured. And it would remain that way for months.
Half a degree doesn’t sound like much, but the amount of energy needed to heat such a large surface is enormous. “So much more energy has been stored in the ocean in the past year than in other years. We don’t know how that is possible,” says De Jong.
Scientists agree that seawater is becoming warmer due to climate change. So why is more research needed? Because the rise in temperature is much less uniform than you would expect, she explains.
Climate change
The speed at which the ocean is warming in particular raises questions, says De Jong. “It’s disturbing. You wonder whether predictions about climate change that are made are still correct.”
De Jong explains that climate change concerns averages and over several years. “The first climate models were simple and spot-on. They all came true.” But now we want to know in detail where it is getting warmer, and why in that place.”
After 420 record days, do we now know anything more about the cause of this special graph? “Some theories have now been refuted,” says De Jong.
Shipping
One suggestion was that it was due to the eruption of the Hunga Tonga volcano, which had blown a lot of water vapor into the atmosphere. But that can only explain a tiny bit of the increased temperature. “There was also a story going around that there are fewer aerosols in the air because shipping has become cleaner. That has also been calculated. That can only explain a few hundredths.”
A lack of wind and Sahara dust cannot be the cause either, says De Jong. El Niño was also mentioned last year, which causes the sea water to warm up. But that natural phenomenon has now subsided while the heat is still there. “Some things fall off on their own.”
The sea surface temperature has not only risen in the Atlantic Ocean. This is the picture worldwide, in the area between 60 degrees north latitude and 60 degrees south latitude:
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It is striking that the warm sea water has not directly led to several major hurricanes. You would normally expect that: warm sea water is the ingredient of a fierce hurricane season.
Inhibitory effect
Last year they were lucky in Central and North Africa. That was probably due to El Niño, scientists say. The atmosphere is more stable during this weather phenomenon. It has an inhibitory effect on the development of hurricanes.
This year there is no El Niño effect, which means the hurricane season could be quite intense. This is also what meteorologist Marjon de Hond from Buienradar says. “Warm sea water is the ideal breeding ground for hurricanes. We will probably see more hurricanes and in more places.”
Both Colorado State University and Atmospheric G2/The Weather Company predict about 20 tropical storms, 11 of which will become hurricanes. For comparison: last year twenty tropical storms formed. Seven of them became hurricanes, which corresponded to an average season.
Deeper in the sea
So there is work to be done for meteorologists. In the meantime, oceanographers continue to investigate seawater temperatures. De Jong emphasizes that there is still plenty to explore beneath the surface of the ocean. “We know the temperature of the top of the ocean from a day ago, but measurements of the ocean current and temperatures from deeper in the sea are not something you can easily access.” These sensors are located deep under water.
The temperature of the top is therefore easier to measure. It is still about 0.9 degrees above average. In this video, marine researcher Furu Mienis explains what other consequences an increasingly warmer sea has for us:
