Lake holds key climate data

Geologist Richard Levy says the Lake Ohau research is extremely valuable to scientists. Photo / Nicole Stahlmann

Scientists hope deep drilling programme will provide clues to what the future holds.

One of New Zealand's most spectacular tourist destinations could also provide a key to better understanding the large-scale changes in store for the planet.

A team of scientists is preparing for a major drilling project at Lake Ohau - a picturesque corridor in Canterbury's Mackenzie Basin, best known for its skifields and postcard-worthy mountain backdrop.

Using a huge rig, mounted on a twin-pontoon barge, the researchers plan to bore 140m down, recovering a rich climate record they hope will span back to the tail-end of the Last Glacial Maximum 17,500 years ago.

At Lake Ohau, this freezing period in the planet's recent history is marked only by the terraced slopes of the U-shaped valley surrounding it - a reminder that a vast glacier once muscled through and carved out lines as it receded while the climate gradually warmed.

From core samples collected by the drill from 70m below the lake-bed, the team will learn about what has happened in New Zealand's climate and rainfall since then, gathering enough detail to create annual records going back at least 10,000 years.

The lake is of enormous value to the international science community - its surrounds have been particularly influenced by the boundary of westerly winds and it remains one of the few places in the planet's mid-latitudes where previous behaviour of glaciers can be accurately reconstructed.

Further, the two rivers that flow into the lake have delivered a vault of sediments containing an excellent geological record - something that has already been demonstrated in a shorter, 1200-year-old core sample.

The evidence may also answer questions about the mysterious Little Ice Age - a period in AD 1300 when the globe cooled and southern New Zealand saw increased rainfall.

And by better understanding how environments have changed in past climate scenarios, scientists will be able to better predict what a climate between 2C and 3C warmer, coupled with sea levels 1m higher, by the end of the century could mean for New Zealand and the rest of the world.

GNS Science geologist Dr Richard Levy, who will undertake the Marsden Fund-supported project alongside colleagues Dr Marcus Vandergoes, Dr Gavin Dunbar and PhD student Heidi Roop, said the research was "extremely important" - especially given the lack of detailed climate data on this part of the planet.

"There's a massive data gap, so we think it's going to be a fundamental and critical piece of the puzzle.

"If the instrumental models that already exist have been able to accurately simulate the records we will find under the lake, then we'll know they've been doing a good job in capturing the previous natural variability in the climate system."

The team expects to report its findings in 2017.

What Lies Beneath

• Scientists plan to lower a barge-mounted drill 70 metres through Lake Ohau - a stunning tourist destination in Canterbury's Mackenzie Basin - and another 70 metres into the earth below.

• They hope to collect core samples dating back as far as 17,500 years ago - at the end of the Last Glacial Maximum - with enough geological detail to provide annual climate records for the entire period.

• With this record, scientists will be able to test instrumental models of past climate records against it, while also better understanding what will happen to our environment under future climate change.