Wanganui reveals prehistoric climate

The Victoria University drill at Siberia Station near Taihape. It is assisting with research into the change in sea level over the past three million years.PHOTO/SUPPLIED

Below much of the Wanganui region lies an accessible, well preserved record of New Zealand's prehistoric climate.

It has attracted a group of researchers from Victoria University who are in the area to drill into the past to get an idea of what the future might hold.

Over the past month a group of scientists have been based at Siberia Station near Taihape drilling about 350 metres into the ground and taking sediment samples.

Director of the Antarctic Research Centre at Victoria University Tim Naish said the Wanganui region provided one of the best records of what the sea level and the climate was like three million years ago.

"What we are looking for is evidence of sea level change," he said.

The nature of the land under the Wanganui region, which is quickly being pushed up, means scientists don't have to drill too far down to find such evidence. Mr Naish said they were particularly focused on records three million years ago because ocean and atmospheric CO2 levels then were about what they are now.

"It's interesting to us because it's the last time that our planet was as warm as it is today and will be in the coming century. It's the last time we had the same levels of greenhouse gas, so we're sort of asking how high were sea levels then. There were different reasons why the CO2 levels were high [but it it is] still useful to see how the environment responded. It's not quite the same in terms of how fast things are happening right now."

At their peak, ocean levels reached the Ruahine Ranges with Taranaki, Wanganui and Manawatu underwater, Mr Naish said.

At Siberia Station the researchers drilled to about 350m and brought up "mud rock".

"It's old ocean sediment, so in this part of Wanganui we would've been under water," Mr Naish said.

"It came up in the last million years, even the last 500,000 years. So we've got this really neat record."

The rock will be taken back to Wellington for further analysis.

"We're going to cut it open so we can really see what's going on."

He said there could be anywhere between five and 25 ice age cycles in that three million years.

"We don't know exactly and that's what we've to find out."