The Indian Ocean played a much larger role in driving climate change during the last ice age than previously believed, and could alter the tropical climate again in the future, according to a study. The study by researchers at the University of Texas at Austin in the United States could rewrite established theories centered on the Pacific on tropical climate change.
“The processes that we have discovered are particularly important in predicting future impacts of climate change,” said Pedro DiNezio, a research associate at the University of Texas Institute of Geophysics (UTIG), who led the research team. “A big climate change like this could have a big impact on the availability of water at the edge of the heavily populated Indian Ocean,” DiNezio said.
Scientists investigated changes in the climate of the tropics during the Last Glacial Maximum (LGM), a period of the last ice age 21,000 years ago when ice sheets covered much of North America, Europe and Asia. Although scientists know that the tropics changed radically during this time, until now they did not understand what was driving these climate changes.
Today, the Indian Ocean is characterized by uniformly warm and stable rainfall patterns. This is because the prevailing winds blow from west to east, keeping the waters warmer on the eastern side of the region and causing rainy conditions in countries like Thailand and Indonesia.
However, during the LGM, the tropics were affected by dramatic changes, including the reversal of prevailing winds and uncharacteristic changes in ocean temperatures. “The geological record tells us that Indonesia and the eastern monsoon regions of the Indian Ocean became colder and drier, while the west became wetter and warmer,” said Jessica Tierney, a paleoclimatologist at the University of Arizona in the United States. United.
To find out what drove these changes, the scientists used a climate model to simulate how various glacial conditions affected the climate. They compared simulated results with paleoclimate data (chemical signatures about our past climate stored in rocks and ocean sediments). The climate model suggests that as the ice sheets advanced over Canada and Scandinavia, sea levels dropped to nearly 400 feet, creating huge continental bridges that stretched from Thailand to Australia.
According to the model, these new land masses reversed the prevailing winds, blowing seawater westward and allowing cold water to flow to the surface in the eastern Indian Ocean. The results are important because they reveal that the Indian Ocean is capable of driving radical changes in the climate of the tropics and that climate models can simulate this complex process.
“Now that we have reproduced glacial climate conditions for the Indo-Pacific region, we are more confident that the same climate model can be used to predict the future of our planet,” said Bette Otto-Bliesner, climate modeler at the Center. National Institute for Atmospheric Research. (NCAR). The study also shows that the mechanisms driving climate change in the LGM may be unique to the Indian Ocean.
This is especially important for predicting how rainfall will change in the tropics because current theories focus on the influence of the Pacific Ocean. Although the study did not specifically investigate whether these climate mechanisms will emerge as the Earth warms, the researchers believe that the role of the Indian Ocean should not be forgotten when making predictions for our warming planet.
“As greenhouse gases increase, we could see a different kind of shakeup,” Tierney said. “If that happens, it could really change our predictions of what the rains and extremes of the weather will be like in the countries along the Indian Ocean coast,” he said.