Australia — There are many theories about the causes of Victoria’s devastating bushfires, and the latest is that the Indian Ocean may have played a part.
Researchers from the CSIRO have found cooler ocean sea-surface temperatures in the eastern Indian Ocean contributed to the very dry conditions that preceded the February 7 fires and Ash Wednesday in 1983.
And a phenomenon known as the Indian Ocean dipole may to be blame.
It refers to the see-sawing nature of sea-surface temperatures in the east and western Indian Ocean.
When the dipole is in a “positive phase,” waters off the Sumatra-Java coast, northwest of Australia, tend to be cooler than normal.
It also leads to a reduction in the rainfall that would normally reach Victoria during spring.
Dr Wenju Cai said the Victorian bushfires occurred during a long drought made worse by three consecutive Indian Ocean dipole events from 2006 to 2008.
“The sequence of these dipole events were captured by Argo measurements, which use robotic floats that spend most of their life drifting below the ocean surface,” Dr Cai said in a statement.
Temperature records from the last 100 years show that the frequency of positive Indian Ocean dipoles in the past three decades is much higher than over the previous 70 years, he said.
The research will be presented at the Greenhouse 2009 Conference in Perth this week.