Ocean corals provide key to climate changes

Deep ocean corals, recovered at depths of 1,000 metres in the Southern Ocean, are signalling a previously unknown pattern of temperate oceanic climate change, over the past 200 years.

This Wealth from Oceans Flagship project is using historical data to study and build marine climate scenarios. Recent analysis by CSIRO Marine Research and US scientists implies that key oceanographic features, influencing Australian climate and the coastal environment, are changing.

It is now known that the East Australian Current is shifting further southward into the Tasman Sea than has been recorded previously.

Chemical analysis of ocean corals, from the same area, indicates a similar, longer-term, temperature change, deep along the continental shelf, which is probably related to the shifts in the East Australian Current. As the surface water has warmed, the deeper regions off the coast are cooling.

“Modelling studies, and our observations of the ocean off the coast of Tasmania, indicate that both the shallow and deep-water changes can be linked to a long-term trend for the cold, rain-bearing winds that, historically, have buffeted southern Australia to move towards the south,” said CSIRO Marine Scientist, Dr Ron Thresher.

“The coral data suggests this trend has been occurring over the last several hundred years, much longer than our climate records allow us to observe directly.”

Dr Thresher said similar wind field changes, recorded south of Western Australia, have been linked to decreases in the rainfall patterns in that State’s south-west region and the retreat of glaciers in New Zealand.

“If the poleward shift in the westerly winds were experienced across temperate Australia, it could have had a substantial impact on land use and the ecology and distributions of terrestrial and marine species, starting about the time of European settlement,” he said.

“Our observations are also consistent with previous, somewhat contentious studies done in Victoria, that have shown declines in the levels of lakes, starting about the same time we’ve seen changes in deep-ocean temperatures.”

Dr Thresher said correlations between temperate Australia and Antarctic indicators suggest that these oceanic changes may also be relevant to Antarctic climate.

The research is a collaboration of the Wealth from Oceans Flagship involving CSIRO Marine Research, the Antarctic Climate and Ecosystems CRC, the Woods Hole Oceanographic Institute and the California Institute of Technology with funding provided by the Fisheries Research and Development Corporation, the Australian Greenhouse Office and the Land and Water Research Development Corporation.

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The Wealth from Oceans Flagship is a CSIRO initiative and part of the National Research Flagships program that aims to deliver scientific solutions to advance Australia's most important national objectives. One of the largest scientific initiatives ever mounted in Australia, it aligns closely with the Federal Government's National Research Priorities. The initiative brings together our national research resources to deliver breakthroughs in fields ranging from healthcare to light metals and the environment.