Monash Magazine

Its effects have been blamed for everything from devastating droughts and floods to an increase in shark attacks and even outbreaks of encephalitis.

The scientific community is still trying to unravel the mysteries of El Nino -- the phenomenon that starts with the warming of Pacific Ocean waters off the west coast of South America and impacts on climatic conditions around the globe.

The Monash researchers sometimes face challenging conditions in the course of gathering their data.

Researchers are currently focusing their attention on Indonesia and the northern-most part of Australia, a region considered vital to the world's moisture generation and rainfall distribution but so far little studied due to access problems.

Among them is a team of about 10 palaeontologists, archaeologists, climatologists and research students from Monash University's School of Geography and Environmental Science.

For about eight years now, supported by grants from Monash and the Australian Research Council, the team has been studying charcoal and pollen samples embedded in sediment 'cores' taken from the floor of the ocean, lakes and swamps at a number of sites across the study region.

"A rainforest, with its moist environment, is a buffer against severe environmental effects. If you take that buffer away, the consequences for the area itself and also adjacent areas can be fairly dramatic."

The marine sediment cores -- some up to 500 metres long and extracted from beneath two to three kilometres of water -- have been collected by international drilling vessels on behalf of research organisations. Fossils contained inside provide a record of how marine environments, vegetation and climates have changed over the past 140,000 to 300,000 years.

These records are supported by more detailed studies of lake and peatland forest sediments and analysis of climate data.

Professor Peter Kershaw, left, Logan Fellow Dr Sander van der Kaars and other team members spend much time involved in land and marine fieldwork in West Java and the region. The map shows the breadth of their projects.

Project leader Professor Peter Kershaw says early analysis of marine cores shows cyclical changes in vegetation and climate patterns about every 100,000 years, linked to the expansion and contraction of northern Atlantic ice sheets.

But in some areas, particularly northern Australia over the last few hundred thousand years, there has been a general drying trend not apparent in the rest of the world.

"We believe this could be due to increased sea surface temperatures indicated in other data, like evidence in the cores that the Great Barrier Reef is only 300,000 or 400,000 years old. It's not geologically ancient, as previously thought, and this indicates that there's been something happening in this region," he says.

"We're suggesting that this temperature increase gave rise to the West Pacific Warm Pool which set El Nino in operation.

"It's a long-term trend, but it's interesting that the suggested rise in sea temperatures of three to four degrees is what the rest of the world is waiting for. This is the predicted greenhouse temperature rise, but northern Australia has already experienced it and it seems to have led to greater variability in El Nino operation."

Also emerging from core analysis is evidence that the arrival of people in the study region, and subsequent increase in burning of forest and grassland areas, accelerated the trend to drier or more variable environmental conditions.

"A rainforest, with its moist environment, is a buffer against severe environmental effects. If you take that buffer away, then the consequences for the area itself and also adjacent areas can be fairly dramatic," Professor Kershaw says.

"It results in a reduction of moisture carried by the monsoons and that affects agriculture in eastern Asia and the rainfall of northern Australia. It has also been suggested that it has influenced the degree of rainfall penetration in the arid part of the Australian continent."

Professor Kershaw says some degree of warming is expected as Australia continues to gradually drift north towards Southeast Asia, but the move appears to have changed atmospheric and oceanic circulation.

"Over a period of 10 million years, there's been a gradual change due to tectonic continental plate movements and volcanic activity in this shallow gap between Indonesia and Australia," he says.

"There's always water from the Pacific Ocean passing through to the Indian Ocean, but if this is blocked off to a large degree, the tropical water will build up in this area. Perhaps something happened, maybe 400,000 years ago, that's caused a change in circulation and this large temperature increase in the area."

The biggest challenge faced by researchers has been gaining permission to research in environmentally and politically sensitive areas. But strong international contacts and a cooperative approach with other researchers has enabled the team to not only access specific sites of interest, but also expand into new areas.

"We've got good collaboration with scientists in other international institutions who have really facilitated our study, rather than having to go individually to government officials and others to get this permission, which can be a real problem," Profesor Kershaw says.

He says that while much work is yet to be done, he hopes his team's research will help scientists more accurately predict future El Nino activity through better understanding of how it is triggered and what causes it to change intensity.

"There's no real solution to the El Nino problem, but the more background information there is for making decisions in the future, the better."



		The Centre for Palynology and Palaeoecology provides consulting services in pollen and diatom analysis and in more general biostratigraphic, environmental and palaeoecological investigation. For details, contact Professor Peter Kershaw on +61 3 9905 2927.