Environment

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Peter Lorimer/AP
New South Wales, Australia in 2006.

Indian Ocean Pinpointed as Cause of Australia’s Drought

February 06, 2009 07:28 AM
by Anne Szustek
A team of researchers found evidence that a drought in Australia is due to a climate pattern known as the Indian Ocean Dipole.

An Ocean of Effects

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Southern Australia has been wracked with drought for the past several years. Generally, scientists have drawn links between rainfall in the region and the weather pattern known as El Niño, which stems from temperature changes in the Pacific Ocean, or its reverse, La Niña.

But a study conducted by a group of Australian researchers indicates that another ocean-based climate pattern may be the cause of southern Australia’s lack of rainfall: the Indian Ocean Dipole (IOD).

Dr. Caroline Ummenhofer of the Climate Change Research Center at Australia’s University of New South Wales was quoted as saying by the Australian Broadcasting Corporation (ABC), “We have found the Indian Ocean plays a profound role in driving [the southern Australian] drought.”

ABC writes, “In its negative phase, the IOD is characterised by cool water to the west of Australia and warm water to the north, leading to winds that bring warm moist, rain-bearing air to the continent.”

During its reverse, fewer humidity-carrying winds pass over Australia, resulting in less rainfall.

According to 100 years of data surveyed by Ummenhofer and her team, all of Australia’s long-lasting droughts occurred during periods when the IOD had few negative phases. There is some evidence that positive IOD cycles may be occurring more often; however, this needs further study.

The aberrant weather cycle is located some 2,000 kilometers off the coast of Australia in an area of the Indian Ocean that is seeing “unprecedented warming,” writes Australian paper The Age.

Related Topic: Other effects of the Indian Ocean Dipole

Scientists have also drawn links between the Indian Ocean Dipole and malaria rates in East Africa, as well as coral reef mortality.

A study by three Japanese researchers approved in 2008 suggests that “the number of malaria cases in the western Kenyan highlands increases” in the months following times when the Indian Ocean Dipole shows a higher surface temperature difference.

In 2003, a team of Australian and Indonesian researchers published a study in Science magazine showing a correlation between Indian Ocean Dipole activity and death in coral reefs off the coast of Sumatra in 1997. The study found that iron fertilization from wildfires, combined with the effects of the IOD, caused red tide that choked off the reef’s oxygen supply.

Reference: Guides to Australia, Environmental Science

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