An international team of scientists has confirmed links between an Indian Ocean phenomenon and extreme weather events in southeast Australia that will enable farmers, industry, communities and governments to better anticipate and prepare for droughts and increased bushfire risk, up to six months in advance of the event.
Cover image – Nature Geoscience
The phenomenon, the Indian Ocean Dipole, is the difference in sea-surface temperatures between the western and eastern part of the Indian Ocean, and until recently has been one of the most influential but the least understood natural forces affecting Australia’s climate.
In a study published today in the journal Nature Geoscience, the team led by CSIRO Wealth from Ocean Flagship’s Dr Wenju Cai, confirmed the link between the Dipole and extreme weather events in southeast Australia.
Just as the El Niño Southern Oscillation (ENSO) affects weather patterns across the Pacific Ocean, the Indian Ocean Dipole influences weather and extreme events across the Indian Ocean. While ENSO fluctuates between ‘El Nino’, ‘neutral’ and ‘La Nina’ phases, the Dipole fluctuates between ‘positive’, ‘neutral’ and ‘negative’ phases approximately every three to eight years.
The positive phase is characterised by greater-than-average sea-surface temperatures, more rain in the western Indian Ocean region and cooler waters in the eastern Indian Ocean. It tends to cause droughts in East Asia and Australia, and flooding in parts of the Indian subcontinent and East Africa.
Positive Dipole activity has, to date, preconditioned major wildfires in southeast Australia, caused coral reef death across western Sumatra, and exacerbated malaria outbreaks in East Africa.
Dr Cai said that the findings allow greater confidence in predicting weather events and climate variability in the future, potentially providing four to six months (two seasons) advanced warning.
“Over the past 50 years, the Dipole has been trending upwards, increasing the number of positive events, occurring an unprecedented 11 times over the past 30 years.
“For example, there were three consecutive positive Dipole events between 2006 and 2008, which preconditioned the catastrophic Black Saturday bushfires in Victoria,” Dr Cai said.
He said the increased frequency is due to the tropical Indian Ocean warming faster in the west than the east, due in part to the increasing temperature of Earth’s surface.
“This warming pattern will continue in the decades to come, according to the state-of-the-art global climate models used in the study,” said Dr Cai.
He said that as the warming pattern continues, future changes will include drier winter and spring seasons over southern Australia, particularly during positive Indian Ocean Dipole years.
Research into the Indian Ocean by CSIRO’s Wealth from Oceans Flagship enables better understanding of climate processes affecting Australia, detecting our changing climate, and reducing uncertainty in Australian climate projections.