Swamp kauri give up their climate secrets

22 May 2013

Carbon dating

Carbon dating: Waikato University scientists are analysing Northland swamp kauri to determine their environmental conditions over time.

Northland swamp kauri is helping University of Waikato scientists compile a timeline of changes in climate going back millennia.

The kauri is analysed at the University's carbon dating laboratory to determine the amount of Carbon 14 in the atmosphere over the tree's lifespan.

Associate Professor Alan Hogg says the research is providing an indication of the environmental conditions experienced by the trees.

Accurate evidence

Because kauri can live for 2000 years, they are unique in providing accurate evidence over long periods. The trees have been growing in Northland for more than 60,000 years and provide one of the best swamp wood archives.

"We can get a picture of what the climate was like 30-40,000 years ago when the world was quite different from today," he says.

The swamp kauri is dug up and cut into slabs, which can then be sent to scientists for analysis.

Carbon dating

Associate Professor Hogg analyses the amount of Carbon 14 in the samples, which reflect atmospheric levels at the time of growth. The amount varies in the tree rings because of two influences which have changed our climate in the past - output from the sun and the amount of carbon stored in the Earth’s various carbon reservoirs, such as oceans, soil and vegetation.

"The carbon dating work we do is part of a jigsaw with lots of different pieces - this is one small part. When you put all the parts together you get a clear picture of past climates, including rainfall and temperature. You can then understand the natural cycles of climate change, which in turn helps to understand human-induced impacts upon it."

The focus of the research is currently the Young Dryas period, from about 13,000 to 11,000 years ago, when parts of the Northern hemisphere experienced a sudden and dramatic lowering of temperatures.

"It's an important period," Associate Professor Hogg says.