He El Niño phenomenona huge mass of warm ocean water in the tropical Pacific Ocean that can change rainfall patterns around the world, is older than the area where it occurs.
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 ago, and 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.
Climate scientists study El Niño, a giant zone of unusually warm water 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. Its counterpart, the cold spot La Niña, can 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.
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 look into 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 “slices” 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.
panthalasian ocean
“In the past, solar radiation reaching Earth was about 2% less than today, but the CO2 that warms the planet was much more abundant, making 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 the ‘atmospheric noise’ of 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. “So 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.”