When the Indian Ocean’s ancient climate patterns return
About 19,000-21,000 years ago, ice-sheets covered North America and Eurasia, and sea-levels were much lower. This period, the peak of ice age conditions, is called the Last Glacial Maximum. Researchers analysed simulations of this past climate and predicted that the ongoing climate change could reawaken an ancient climate pattern of the Indian Ocean.
- They find that this could be similar to the El Niño phenomenon of the Pacific Ocean bringing more frequent and devastating floods and drought to several densely-populated countries around the Indian Ocean region.
- If current warming trends continue, this new Indian Ocean El Niño could emerge as early as 2050. The results were published in Science Advances.
Study on shells
- By studying microscopic zooplankton called foraminifera, the team had published a paper in 2019 which first found evidence from the past of an Indian Ocean El Niño.
- Foraminifera build a calcium carbonate shell, and studying these can tell us about the properties of the water. The team measured multiple individual shells of foraminifera from ocean sediment cores and reconstructed the sea surface temperature conditions of the past.
Lessons to learn
- “As it is, under present-day conditions, changes in the Indian Ocean Dipole and the El Niño–Southern Oscillation strongly affect Indian Monsoon variability from year to year. If the hypothesised ‘equatorial mode’ emerges in the near future, it will pose another source of uncertainty in rainfall prediction and will likely amplify swings in monsoon rainfall.”
- The paper adds that it could bring more frequent droughts to East Africa and southern India and increased rainfall over Indonesia. The team warns that further work is needed to accurately assess this new mode, particularly under lower-emission scenarios and taking into account past climatic states other than the Last Glacial Maximum.