It’s no secret that weather forecasting is getting more complicated. Three months ago, the world’s major agencies stated this hurricane season would be intense. One of the two main reasons was something you’ve probably heard before: The Atlantic Ocean is unusually hot. But three months later, experts have discovered something surprising: The Atlantic is cooling.
Temperatures are dropping. A strange shift from warm to cold temperatures has been underway in the equatorial Atlantic Ocean since May, and it’s happening at record speed. This emerging pattern, a kind of “Atlantic Niña,” occurs just before an expected transition to a colder La Niña in the Pacific Ocean—a series of consecutive events that could have a domino effect on the global climate.
A difference compared to 2023. “We’re starting to see global average ocean temperatures going down,” Pedro DiNezio, a professor at the University of Colorado Boulder, said. According to NOAA, global sea surface temperatures this July were slightly colder than in July 2023, ending a 15-month streak of record-breaking average ocean temperatures.
Trade winds are the key. The area where this temperature change occurs is a narrow corridor along the equator near the African coast. The cooling of these waters during the summer is due to the trade winds, which move westward and tend to increase during the summer as a narrow region of tropical storms moves north. The interaction of these winds with the ocean water reduces some heat. However, the infusion of cooler water can be more or less significant in any given year.
2024 began with hot ocean waters in the eastern equatorial Atlantic. Still, experts observed a rapid transition to relatively cooler waters in late May, June, and July. It was the fastest transition on record. “We have reviewed the list of possible mechanisms, and nothing fits the bill so far. If temperatures remain 32.9 °F cooler than average for at least one more month, it will officially be considered an ‘Atlantic Niña,’” Franz Philip Tuchen, researcher at the University of Miami, stated.
Still unexplained. Interestingly, the cooling coincided with the weakening of the trade winds, which would generally do the opposite. This is one of the reasons why scientists aren’t sure how or why this is happening. More research is needed to understand the event.
How it affects the weather. These dramatic changes will inevitably impact our weather. Researchers point out that the two possible La Niña events will likely influence weather patterns worldwide because of their effects on temperature and humidity.
On the one hand, research associates La Niña in the Pacific Ocean with dry weather in the western U.S. and wet weather in eastern Africa. At the same time, an Atlantic Niña would tend to reduce rainfall in the Sahel region of Africa and increase rainfall in parts of Brazil.
How it affects the hurricane season. This is the other part to study, mainly because of the season. The region that could experience the potential Atlantic Niña, with abnormally cold water, is along the equator and not in the tropics where hurricanes form. There, the water is still quite warm. However, research has shown that an Atlantic Niña tends to reduce rainfall in the Gulf of Guinea region of Africa. In turn, it reduces the amount of tropical circulation coming off the African coast, which could limit the number of tropical cyclones.
Researchers associate the opposite phenomenon, El Niño/La Niña in the Pacific Ocean, with more tropical forces from East Africa. This increases the likelihood of hurricane activity. In other words, the Atlantic El Niño/Niña primarily affects hurricane development by regulating the amount of tropical circulation pushing off the African coast. However, it doesn’t appear to be a significant player in tropical forces originating elsewhere, such as the Caribbean or the Gulf of Mexico.
Influencing phenomena. For example, we have La Niña developing as we approach the peak hurricane season in 2024, which would favor an active season. However, we also have an Atlantic Niña, which could delay the otherwise highly predicted hyperactive season. That is if the Atlantic Niña develops.
For all that, experts say it’s difficult to predict how, but there’s reason to believe that the Atlantic La Niña could delay the development of the La Niña in the Pacific Ocean, slowing its cooling effects on the overall global climate. “There could be a tug of war between the Pacific trying to cool and the Atlantic trying to warm,” concludes NOAA researcher Michael McPhaden.
This article was written by Miguel Jorge and originally published in Spanish on Xataka.
Imagen | NASA Johnson, Franz Philip Tuchen/NOAA/climate.gov
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