Robot returns from the icy depths

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NIWA Oceanographer Dr Craig Stevens has returned, with stunning images and data, from a successful month-long research trip in Antarctica, where he led a team of international and New Zealand scientists.

The team deployed a suite of hi-tech sensors including an underwater robot, to measure how ocean turbulence affects ice shelves. Scientists looked at the ocean mixing that happens right at the face of the Erebus Glacier Tongue in McMurdo Sound, off Ross Island. They are using this as a laboratory to determine what drives ocean circulation beneath ice shelves.

Ice shelves are important from a climate and sea level-rise perspectives. By 2100 scientists are predicting a 50 – 80 cm sea-level rise, but with a huge uncertainty around the role of the ocean, and how it warms the underside of ice shelves. One of the big challenges in understanding sea-level rise is measuring the stability of ice shelves.

Dr Stevens says, “We think ice shelf stability may play a big part in sea-level rise. A future warmer ocean will melt the underside of an ice shelf more quickly. A thinner shelf is more prone to collapse, and this in turn unlocks the Antarctic ice sheet, that sits on the Antarctic continent, which may flow more rapidly in to the ocean. Suddenly we are in deep water! This is a worse case scenario - but the work all relates to understanding the likelihood of that happening. 

There have only been a few under-ice turbulence measurements made globally, and even fewer in the vicinity of ice shelves. Under-ice datasets will allow scientists to better understand ice-ocean interactions and provide valuable information for climate modellers.

“Our big success was that we got the whole map of the current flow at the lip of this giant floating glacier. We are all familiar with beautiful time lapse films of clouds going over mountain ridges - they shoot down the other side. The same thing happens in the ocean where it flows over or under a ridge. The data we have just captured are unique– it is very rare to see such strong vertical flows in the ocean,” says Dr Stevens.

The scientific research was funded by the Royal Society of New Zealand’s prestigious Marsden Fund. As the planning for the field experiment progressed it generated a lot of international interest. Scientists from the USA, Canada and the UK joined the kiwi group of scientists. Dr Stevens says, “It was really exciting working with world-leaders in this sort of science. They brought some fantastic equipment along, including the robot. We in turn did well with our turbulence sensors and showed them some unique and important oceanography. It’ll take a little while to unravel all the data but we plan on getting the results out to the international science community as quickly as possible.”

Dr Stevens’ team is planning to do further work in Antarctica next summer, on the Drygalski Glacier Tongue – one of the largest glacier tongues in Antarctica.

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Principal Scientist - Marine Physics
Dr Craig Stevens and an ADCP current meter with Mt Erebus in background. The 75 kHz ADCP send out pings into the water and then listen to the Doppler shift to gauge the flows. This ADCP is one of three providing new looks at flows in Cook Strait, Kaikoura Canyon, and McMurdo Sound.
Research subject: Climate changeIceOceans