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Indian Ocean temperature link to bushfires

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March 24, 2009

Image credit – Willem van Aken, CSIRO

Image credit – Willem van Aken, CSIRO

March 24, 2009 The weather conditions that lead to Southern Australia’s past two devastating bushfires may be linked to lower than normal sea-surface temperatures in the eastern Indian Ocean, according to CSIRO research presented at the Greenhouse 2009 Conference today. The Ash Wednesday bushfires in February 1983 and the Black Saturday bushfires in February were preceded by months of very dry conditions. Those dry conditions were partly caused by cooler ocean sea-surface temperatures in the eastern Indian Ocean, which contributed to a substantial reduction in spring-time rainfall over the south-east of Australia.

The see-sawing nature of sea-surface temperatures in the east and western Indian Ocean is commonly referred to as the Indian Ocean Dipole. When the dipole is in a positive phase sea-water off the Sumatra-Java coast, northwest of Australia, tends to be cooler than normal, leading to a reduction in the rain-bearing systems that normally extend to Victoria during spring.

According to CSIRO’s Dr Wenju Cai, the recent bushfires in Victoria occurred during a protracted drought made worse by an unprecedented three consecutive positive 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 says.

“Another study examining temperature records of the past 100 years shows that the frequency of positive Indian Ocean Dipoles in the past three decades is much higher than over the previous 70 years. This trend is consistent with climate change experiments from the IPCC Fourth Assessment Report, published in 2007, which projects a mean warming pattern across the Indian Ocean reminiscent of a positive dipole pattern.”

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About the Author
Mike Hanlon Mike grew up thinking he would become a mathematician, accidentally started motorcycle racing, got a job writing road tests for a motorcycle magazine while at university, and became a writer. As a travelling photojournalist during his early career, his work was published in a dozen languages across 20+ countries. He went on to edit or manage over 50 print publications, with target audiences ranging from pensioners to plumbers, many different sports, many car and motorcycle magazines, with many more in the fields of communication - narrow subject magazines on topics such as advertising, marketing, visual communications, design, presentation and direct marketing. Then came the internet and Mike managed internet projects for Australia's largest multimedia company, Telstra.com.au (Australia's largest Telco), Seek.com.au (Australia's largest employment site), top100.com.au, hitwise.com, and a dozen other internet start-ups before founding Gizmag in 2002. Now he writes and thinks. All articles by Mike Hanlon
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