Guest essay by Eric Worrall
Global warming models have predicted the emergence of an Indian Ocean version of the Pacific El-Nino / La-Nina cycle. Paleo climate research suggests this was active during the last ice age.
MAY 6, 2020
Climate change could reawaken Indian Ocean El Nino
Global warming is approaching a tipping point that during this century could reawaken an ancient climate pattern similar to El Niño in the Indian Ocean, new research led by scientists from The University of Texas at Austin has found.
“Our research shows that raising or lowering the average global temperature just a few degrees triggers the Indian Ocean to operate exactly the same as the other tropical oceans, with less uniform surface temperatures across the equator, more variable climate, and with its own El Niño,” said lead author Pedro DiNezio, a climate scientist at the University of Texas Institute for Geophysics, a research unit of the UT Jackson School of Geosciences.
According to the research, if current warming trends continue, an Indian Ocean El Niño could emerge as early as 2050.
Computer simulations of climate change during the second half of the century show that global warming could disturb the Indian Ocean’s surface temperatures, causing them to rise and fall year to year much more steeply than they do today. The seesaw pattern is strikingly similar to El Niño, a climate phenomenon that occurs in the Pacific Ocean and affects weather globally.
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.
…Read more: https://phys.org/news/2020-05-climate-reawaken-indian-ocean-el.html
The abstract of the study which predicts an Indian Ocean El Nino;
Emergence of an equatorial mode of climate variability in the Indian Ocean
Science Advances 06 May 2020:
Vol. 6, no. 19, eaay7684
Presently, the Indian Ocean (IO) resides in a climate state that prevents strong year-to-year climate variations. This may change under greenhouse warming, but the mechanisms remain uncertain, thus limiting our ability to predict future changes in climate extremes. Using climate model simulations, we uncover the emergence of a mode of climate variability capable of generating unprecedented sea surface temperature and rainfall fluctuations across the IO. 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. These predictions are supported by modeling and proxy evidence of an active mode during glacial intervals that favored such a state. Because of its impact on hydrological variability, the emergence of such a mode would become a first-order source of climate-related risks for the densely populated IO rim.Read more: https://advances.sciencemag.org/content/6/19/eaay7684
The study which identified paleo-climate evidence of an ice age Indian Ocean El-nino;
An El Niño Mode in the Glacial Indian Ocean?
Despite minor variations in sea surface temperature (SST) compared to other tropical regions, coupled ocean‐atmosphere dynamics in the Indian Ocean cause widespread drought, wildfires, and flooding. It is unclear whether changes in the Indian Ocean mean state can support stronger SST variability and climatic extremes. Here we focus on the Last Glacial Maximum (19,000–21,000 years before present) when background oceanic conditions could have been favorable for stronger variability. Using individual foraminiferal analyses and climate model simulations, we find that seasonal and interannual SST variations in the eastern equatorial Indian Ocean were much larger during this glacial period relative to modern conditions. The increase in year‐to‐year variance is consistent with the emergence of an equatorial mode of climate variability, which strongly resembles the Pacific El Niño and is currently not active in the Indian Ocean.Read more: https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019PA003669
Assuming the studies are correct, if the Indian Ocean El-nino can occur in glacial conditions and warm conditions, clearly its something which can occur under a range of conditions, maybe even spontaneously, so promoting this prediction as a climate risk seems pretty thin.
If an Indian Ocean El-Nino / La-Nina cycle does start, it won’t necessarily be a bad thing; a good drenching for Western Australia on a regular basis might increase water availability in Australia’s arid interior.