New Study finds possible rebirth of Indian Ocean El Niño with Climate Change
Simulated changes in Indian Ocean climate variability and mean state under glacial conditions and greenhouse warming showing the emergence of the Indian Ocean El Niño which does not exist currently.
“Greenhouse warming is creating a planet that will be completely different from what we know today, or what we have known in the 20th century,” author DiNezio said.
A new study published on Wednesday suggests that global warming could lead to the rebirth an Indian Ocean El Niño and La Niña appearing as early as 2050.
A paper in 2019 by the same author find evidence of an Indian Ocean El Niño during the Last Glacial Maximum (LGM).
Co-author Kaustubh Thirumalai, who led the study that discovered evidence of the ice age Indian Ocean El Niño, said that the way glacial conditions affected wind and ocean currents in the Indian Ocean in the past is similar to the way global warming affects them in the simulations.
“This means the present-day Indian Ocean might in fact be unusual,” said Thirumalai, who is an assistant professor at the University of Arizona.
"This mode, which is inhibited under present-day conditions, becomes active in climate states with a shallow thermocline and vigorous upwelling, consistent with the predictions of continued greenhouse warming." the study says.
At present an ENSO like mode is present in both the Pacific and Atlantic Oceans but not the Indian Ocean where only the IOD is present. This is because of the uniformly deep thermocline and westerly winds over the Indian Ocean the study says.
Both Greenhouse warming and glacial conditions result in a strengthening of easterly winds over the equator something which is reinforced by the changes in the underlying SST gradient via the cooling effect of a shallower thermocline the study says. However, the study says that these changes are initiated by different physical processes in the glacial and greenhouse warming case being shelf exposure for the glacial and a reversal of westerly winds over the eastern Indian Ocean driven by a weaker Walker circulation in the case of greenhouse warming but both result in the emergency in this ENSO like mode in the Indian Ocean.
“Greenhouse warming is creating a planet that will be completely different from what we know today, or what we have known in the 20th century,” author DiNezio said.
A new study published on Wednesday suggests that global warming could lead to the rebirth an Indian Ocean El Niño and La Niña appearing as early as 2050.
A paper in 2019 by the same author find evidence of an Indian Ocean El Niño during the Last Glacial Maximum (LGM).
Co-author Kaustubh Thirumalai, who led the study that discovered evidence of the ice age Indian Ocean El Niño, said that the way glacial conditions affected wind and ocean currents in the Indian Ocean in the past is similar to the way global warming affects them in the simulations.
“This means the present-day Indian Ocean might in fact be unusual,” said Thirumalai, who is an assistant professor at the University of Arizona.
"This mode, which is inhibited under present-day conditions, becomes active in climate states with a shallow thermocline and vigorous upwelling, consistent with the predictions of continued greenhouse warming." the study says.
At present an ENSO like mode is present in both the Pacific and Atlantic Oceans but not the Indian Ocean where only the IOD is present. This is because of the uniformly deep thermocline and westerly winds over the Indian Ocean the study says.
Both Greenhouse warming and glacial conditions result in a strengthening of easterly winds over the equator something which is reinforced by the changes in the underlying SST gradient via the cooling effect of a shallower thermocline the study says. However, the study says that these changes are initiated by different physical processes in the glacial and greenhouse warming case being shelf exposure for the glacial and a reversal of westerly winds over the eastern Indian Ocean driven by a weaker Walker circulation in the case of greenhouse warming but both result in the emergency in this ENSO like mode in the Indian Ocean.
Images from paper:
Observed variability and mean state over the tropical oceans under current climate showing a uniformly deep thermocline over the Indian Ocean:
Simulated changes in Indian Ocean climate variability and mean state under glacial conditions and greenhouse warming:
Rainfall impacts of current IOD and Indian Ocean ENSO like mode in the Indian Ocean:
Atmospheric precursor and developed warm equatorial mode events under greenhouse warming, glacial, and modern climate conditions, there is no such mode under modern climate:
Atmospheric precursor and developed cool equatorial mode events under greenhouse warming, glacial, and modern climate conditions, there is no such mode under modern climate:
Equatorial mode (ENSO-like) vs the IOD:
The images are from the study which is titled "Emergence of an equatorial mode of climate variability in the Indian Ocean". Read the paper at https://advances.sciencemag.org/content/6/19/eaay7684 .