NZ scientists to drill vast ice sheet

Study to ask how warming oceans might impact frozen mass storing 3m of global sea level rise

ANew Zealand scientist is leading an expedition to investigate how warming oceans could affect an Antarctic ice sheet that stores an equivalent three metres of global sea level rise.

Victoria University geologist Dr Rob McKay is heading a 30-strong team from the International Ocean Discovery Programme (IODP) who, from next month, will spend nearly 10 weeks drilling at six sites around the Ross Sea.

The drilling, reaching up to a kilometre below the sea floor at each of the sites, aims to better understand the interplay of the ocean and the West Antarctic Ice Sheet, which, according to satellite data, is losing around 150 cu km of ice each year.

It packed about 10 per cent of the volume of the 25.4 million cu km of the wider Antarctic ice sheet.

“We want to understand how the ocean and the ice sheets interact,” said McKay, an associate professor at Victoria’s Antarctic Research Centre, who will travel to the ice on the JOIDES Resolution, a 140m-long scientific research ship operated by the IODP.

“So what happens when you put warm water next to the ice sheets? Do they melt? If so, how quickly do they melt? And what’s the impact of that melt on the oceans?”

By drilling down so deeply into the sea floor, the team would be able to gain a glimpse into the past — up to 20 million years ago — and “greenhouse worlds” that contained the same level of carbon dioxide as that now in our atmosphere.

“Using these geological records to see what the planetary response was to the current carbon dioxide levels means we can better understand what the scale of change could be for us, and what the Earth is capable of in a warmer world,” McKay said.

“Antarctica today acts as a giant heat-sink that keeps the planet cold.

“If you change that, you’re changing a major part of the global climate system.

“We’re trying to understand what happened the last time that was changed.”

If the West Antarctic Ice Sheet were to melt — as it has in the past — McKay said the global sea level would rise about three metres.

The impact from the collapse of the Eastern Antarctic Ice Sheet would be even more dramatic, because it contained enough ice to cause an estimated 20m rise in sea levels.

“The consequences of that for coastal living, globally, are obvious, but we’re also trying to understand the implications for the biosphere in the Southern Ocean,” he said.

“This is one of the largest biological habitats on the planet and we don’t know how it will respond to these changes.”

An important difference between then and now was also the fact that the increase in carbon dioxide levels that took many thousands of years to occur as part of natural cycles has happened in just a couple of centuries due to human emissions and is continuing.

No stranger to the coldest, driest, windiest continent on Earth, McKay travelled to Antarctica when he was 20 for his first overseas trip — which he describes as a “sensory overload”.

Two decades later and the five years he has spent planning the current expedition are about to pay off, because he will follow in the footsteps of several pioneering Victoria University researchers.

“One of the reasons I was invited to be the co-chief scientist on this expedition is that we have a very strong link with records of previous drillings, led by Victoria,” McKay said.

“It’s been almost 50 years since the — Jamie Morton first drilling in Antarctica, which was carried out by scientists that included Victoria University Emeritus Professor Peter Barrett — former director of the Antarctic Research Centre.

“He revolutionised the way we view Antarctica, in terms of its geological record, and really pioneered core sample drilling on the continent.

“He developed a record that is . . . fundamental to interpreting Antarctica’s role in global climate change.”