The El Niño climate phenomenon, a huge mass of warm ocean water in the tropical Pacific Ocean that can change rain patterns around the worldis older than the area where it is produced.
A new modeling study by a pair of Duke University researchers and their colleagues shows that the oscillation between El Niño and its cold counterpart, La Niña, was present at least 250 million years agoand was often of greater magnitude than the oscillations we see today.
These temperature changes were more intense in the past, and the oscillation occurred even when the continents were in different places than they are now, according to the study, which is published in the journal PNAS.
“In every experiment, we see an active El Niño southern oscillation, and it is almost always stronger than what we have now, some much stronger, some slightly stronger,” Shineng Hu, assistant professor of climate dynamics, said in a statement. at the Nicholas School of the Environment at Duke University.
Changing rainfall patterns
Climate scientists study The Childa gigantic unusually warm water area on either side of the equator in the eastern Pacific Ocean, because it can disrupt the jet stream, drying out the northwestern United States while drenching the southwest with unusual rainfall. His counterpart, the cold spot La Niñacan push the jet stream northward, drying out the southwestern United States, while also causing drought in East Africa and making the South Asian monsoon season more intense.
A tool to travel through time
The researchers used the same climate modeling tool used by the Intergovernmental Panel on Climate Change (IPCC) to try to project climate change into the future, except they ran it backwards to see the deep past.
The simulation is so computationally intensive that the researchers were unable to model each year continuously for 250 million years. Instead, they made “cuts” of 10 million years: 26 of them.
“The model experiments were influenced by different boundary conditions, such as different distribution of land and sea (with the continents in different places), different solar radiation, different CO2,” Hu said. Each simulation was run for thousands of model years to obtain robust results and took months to complete.
Panthalassic Ocean
«In the past, the solar radiation reaching the Earth was approximately 2% less than today, but the CO2 that warms the planet was much more abundantwhich made the atmosphere and oceans much warmer than today,” Hu said. In the Mezozoic period, 250 million years ago, South America was the middle part of the supercontinent Pangea, and the wobble occurred in the Panthalassic Ocean to the west.
“The study shows that the two most important variables in the magnitude of the oscillation historically appear to be the thermal structure of the ocean and ‘atmospheric noise’ from ocean surface winds,” said Xiang Li, a postdoc at Duke who is the first author.
Previous studies have focused primarily on ocean temperatures, but paid less attention to the surface winds that seem so important in this study, Hu said. “Therefore, part of the goal of our study is that, in addition to the thermal structure of the ocean, we also need to pay attention to atmospheric noise and understand how those winds are going to change».
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