Quick Dips

Digging up the Climates of the Past

Victoria University has begun a major programme to investigate and model past climate change in New Zealand. An important part of the programme is a new Luminescence Dating Laboratory, the first of its kind in New Zealand.

The project, funded by a $300,000 grant from the Foundation for Research, Science and Technology for its first year, is expected to produce results which will help scientists predict the effects on New Zealand of possible global warming caused by the greenhouse effect.

Project leader Dr James Shulmeister, a geologist at Victoria University, says that over the next six years his team hopes to drill deep bores hundreds of metres into the ground and to analyse the bore materials for clues to past climates in different parts of New Zealand.

"New luminescence dating equipment, bought from Denmark at a cost of $125,000, will help us date the different levels in the bores," says Shulmeister.

"This new technology has two main advantages over the more usual radio-carbon dating techniques: it can work on common materials like mud and sand, whereas radiocarbon dating needs organic material, and it can go further into the past -- up to 100,000 years with accuracy, and in exceptional circumstances to nearly a million years.

"We will be drilling cores in most parts of New Zealand, aiming to establish a detailed climate history in New Zealand on a regional scale, covering the last 250,000 years. The first of the cores has already been drilled, next to Lake Poukawa near Hastings, and analysis of that material has begun. The initial results show 28 layers of ash from volcanic eruptions, which will also help us determine the age of the core."

Victoria University is sub-contracting two Crown Research Institutes, the Institute of Geological and Nuclear Sciences and the National Institute of Water and Atmospheric Research, to help with this programme, and is also collaborating with scientists at other CRIs and universities.

The material from the cores will provide a number of clues to the climate of the past, says Shulmeister.

"There are different sorts of micro-fossils, of which pollen is the most important. The pollen will tell you what sort of vegetation was growing in an area at a certain time -- trees, shrubs, grassland and so on -- and this will tell you a lot about the climate, because different types of plants thrive in different sorts of climates."

Fossils of animals with shells can also give indications of past temperatures -- to as close as 1^oC -- through the chemical analysis of the ratio of two different types of oxygen trapped in the shells.

With the help of a grant from the Lotteries Board, Victoria University has established a new Luminescence Dating Laboratory to take part in this work. The new Risoe luminescence machine establishes the age of materials like silt and sand by counting the number of light flashes the materials give off when subjected to heat or strong light. These flashes are in turn related to the materials' exposure to natural levels of radiation, and this exposure relates to how long they have been buried.

The equipment for this facility arrived in March 1997 and Dr Olav Lian (a graduate and co-worker of the pre-eminent luminescence scientist, Prof D.J. Huntley of Simon Fraser University in Canada) has recently joined Victoria to establish and run the facility.

"This programme will give us much more information about the history of climate in New Zealand," Shulmeister says. "Results from the drilling programme will be used by climate scientists at NIWA to model past changes in the climate of New Zealand. This data will then be of vital importance in understanding how future climate changes could affect this country."