Indian Ocean heats up Australia

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Changes in the Indian Ocean’s surface temperature are causing hotter and drier conditions in southeast Australia, researchers have found.

Work by the Australia National University and the ARC Centre of Excellence for Climate Extremes is helping to improve the understanding of climate variations and managing the risk caused by Indian Ocean variability.

Lead researcher Professor Nerilie Abram said the phenomenon known as the Indian Ocean Dipole was a major reason for the severe drought and record hot temperatures in 2019.

Professor Abram of the Research School of Earth Sciences and the Centre of Excellence for Climate Extremes at ANU, said, “The 2019 event, known as a positive Indian Ocean Dipole, was a big one. It cut off one of the major sources for southern Australia’s winter and spring rainfall, and set up the extremely hot and dry conditions for the terrible fires that ravaged Australia this summer.”

The researchers studied coral records from the eastern equatorial Indian Ocean to reconstruct Indian Ocean Dipole variability over the last millennium.

Professor Abram said, “Historically, strong events like the one we saw in 2019 have been very rare. Over the reconstruction beginning in the year 1240, we see only 10 of these events, but four of those have occurred in just the last 60 years.”

Co-researcher Professor Matthew England said the research showed a tight coupling has existed between the variability of the Indian Ocean Dipole and the El Nino-Southern Oscillation (ENSO) in the Pacific Ocean during the last millennium.

He said, “Our research indicates that while Indian Ocean Dipole and El Nino events can occur independently, periods of large year-to-year swings in Indian Ocean variability also had heightened ENSO variability in the Pacific.”

Professor England added, “Looking at the tropical oceans in this interconnected way improves our understanding of seasonal to decadal climate variations in regions that profoundly impact Australia, helping us to be better prepared for future climate risks caused by the Indian Ocean Dipole.”

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