Landslide buries climate change link

Scientists at University of Canterbury are disputing evidence that is widely used as an example that climate change can happen simultaneously around the world.

The two geologists and an honours student have been studying the Waiho Loop glacial moraine on the plain between the Franz Josef township and the sea. Scientists have believed the Waiho Loop moraine, an 80 metre-high semi-circular ridge of rocky debris, was created during a brief cold snap about 13,000 years ago, called the Younger Dryas. Scientists believe that during the Younger Dryas temperatures dropped by up to 10° Celsius within just 10 years in Europe and North America. The sudden ice age is credited with making more than 40 species of large animals, such as the woolly mammoths, extinct. It also inspired the Hollywood blockbuster movie The Day After Tomorrow and the computer animated movie, Ice Age.

The Waiho Loop moraine is widely used throughout the world by scientists as evidence for direct linkage between the Northern and Southern hemispheres during climate change events (cooling or warming occurring simultaneously in both hemispheres).

However, one of the researchers, Professor Jamie Shulmeister, says they are throwing "a cat among the paleoclimate pigeons", as their new study suggests that the loop of debris, which sits near the South Island's Alpine fault line, is the result of a landslide, not climate change.

Professor Shulmeister, who worked on the research with Associate Professor Tim Davies and honours student Daniel Tovar, says there has been a huge scientific debate on the climatic implications of the Waiho Loop. But no one had ever studied its sediments.

"When graduate student Dan Tovar had a look he discovered to our surprise that it was mainly made up of a rock type known as greywacke which is different to the rocks that make up all the other moraines in front of the Franz Josef glacier.

"This rock type occurs about 13 kilometres up the valley from the Loop. All the other moraines are predominantly composed of schist which outcrops near Franz Josef township. The greywacke was also rather more angular than the rocks in the other moraines, suggesting it had not been transported in water or at the base of a glacier."

As a result of its findings, Professor Shulmeister's team believes a large landslide dumped a huge volume of rock on top of the glacier causing it to advance and, when the advance stopped, the moraine was created. With this revision the theories about climate change in New Zealand at the end of the last ice age needs reconsideration.

The findings were published in the prestigious international science journal, Nature Geoscience in early July. With an advanced online version published on 29 June 2008.