Researchers found that 2023’s record-breaking marine heat wave was caused by extraordinarily weak winds and increased solar activity. Photo: Wikimedia Commons
In 2023, the seas in the North Atlantic Ocean broke heat records. Not just broke them, but absolutely smashed them. Now, researchers looking into what caused it have found an answer and published it in the journal Nature.
“The intensity of the warming in that single summer was equivalent to about two decades worth of warming for the North Atlantic,” said lead author, Professor Matthew England. “While these extreme temperature events are typically only temporary, we can expect they’ll become more frequent in the future.”
The study, which was led by scientists from the University of South Wales Sydney, looked at nearly all regions of the North Atlantic including the subpolar ocean, where there has been a cooling trend in that particular zone over the last 50-100 years.
In short, the researchers found that the “off-the-scale marine heat wave” was caused by incredibly weak winds in 2023 and increased solar radiation. Wind helps to disperse heat as it gathers over the ocean as well as churning the surface of the ocean up, letting the cooler waters beneath mix with it. Solar radiation, obviously, supplies that heat. When there’s more heat and less wind to spread it around, the surface of the ocean warms rapidly.
In an ironic twist, Professor England was actually looking into a region in the North Atlantic that was strangely cold. It is important to remember here that “global warming” means that the planet is warming on average, so intermittent bouts of cold in certain regions aren’t an indicator that global warming isn’t real. The so-called “cold blob” England was researching was off Greenland, and was just one of the consequences of global warming. “[It was] a sign of the Atlantic Meridional Overturning Circulation (AMOC) slowing down, which is a scenario made famous by the Hollywood movie, The Day After Tomorrow, Phys.org explained.
Since the cold blob had been cooling those waters for nearly a century, the researchers were surprised to see that water temperatures were rising rapidly, leading to a few questions. “We even asked ourselves if this was the circulation making a temporary comeback, but the rate of warming was far too rapid for that,” England said.
With far less wind than normal, the surface layer of the ocean wasn’t mixing with the deeper, colder water, which allowed the sun’s energy to heat it up. According to Professor England, this is just the beginning. Marine heat waves will almost certainly become more severe and more frequent in the future.
“Severe marine heat waves often only last for a few weeks or months, but this one in the North Atlantic left a legacy that persisted for more than a year,” he said. “Unfortunately, the frequency and intensity of marine heat waves is only set to worsen in the coming decades and beyond. The only way to stop this trend is to phase out our use of fossil fuels. Net zero cannot come soon enough.”
