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Global climate change could raise the sea temperatures off the east of New Zealand's South Island by as much as 2 degrees Celsius and change the whole marine ecosystems -- a phenomenon that last occurred 125,000 years ago, New Zealand scientists said Wednesday.
The seas would be warmed by more energetic wind patterns in the South Pacific that would sweep subtropical ocean currents further south, the scientists said in a statement from the government's GNS Science research institute.
As atmospheric carbon dioxide levels climbed and winds intensified, the East Australian current pattern would become stronger and move more heat southward, and the beginnings of this were already noticeable.
The scientists based their findings on the study of microscopic marine plankton fossils called foraminifera, which were found in more than a dozen seabed sediment cores collected from the Tasman Sea and east of New Zealand.
Analysis of the foraminifera enabled the scientists to reconstruct the last major global warm period about 125,000 years ago, when water temperatures were about 2 degrees warmer than today.
"The ocean warming has already started, with temperatures off Tasmania having risen by 1.5 degrees Celsius in the past 70 years, which is more than twice the global average rate," lead author Giuseppe Cortese, of GNS Science, said in the statement.
The warming off Tasmania had been accompanied by an invasion of sub-tropical marine life, which had replaced sub-Antarctic species.
As temperatures increase off Australia's east coast, ocean circulation patterns would change and the biggest amount of warming will be seen off the South Island's east coast, representing a significant change for marine ecosystems.
"From what we are seeing off the coast of Australia, both in recent observed trends and in our reconstruction from the past, such temperature changes are likely to have impacts on the whole marine ecosystem, and will ultimately impact on commercial fish stocks," said Cortese.
