x Abu Dhabi, UAEFriday 28 July 2017

New York University Abu Dhabi scientists probe glacier's secrets

As the Earth's temperature climbs and the ice sheets slowly melt, the global sea level is rising. Not only that, the breaking up of the ice shelves has been linked to the severe storms and coastal erosion seen on every continent in recent years.

The Pine Island Glacier Ice Shelf is the site of a mission to measure the polar ice's temperature. Michael Studinger / Nasa
The Pine Island Glacier Ice Shelf is the site of a mission to measure the polar ice's temperature. Michael Studinger / Nasa

Miles below the surface of the vast ice sheets at the earth's extremities, something is constantly stirring.

These are the planet's most remote corners, with conditions so harsh and dangerous that they are all but unknown to man. Yet the currents that flow beneath the ice could have profound consequences for all of us.

As the Earth's temperature climbs and the ice sheets slowly melt, the global sea level is rising. Not only that, the breaking up of the ice shelves has been linked to the severe storms and coastal erosion seen on every continent in recent years.

What no one knows is just how fast the sheets are melting and how fast they are likely to melt in the future. To make a decent estimate, scientists need data about the speed and direction of ocean currents, the water temperature and salinity, seismic activity, ice thickness and fracturing.

Most of all, they need to know about the flow of ocean water under the ice.

But that information, hidden as it is kilometres below the frozen wastelands, is hard to come by.

A team led by David Holland, the head of New York University Abu Dhabi's Centre for Sea-Level Change and a professor of maths and atmosphere-ocean science, is trying to fill in some of the gaps.

Dr Holland this year led one of three international teams into West Antarctica to plant a fibre-optic cable deep under the belly of the fast-moving Pine Island Glacier.

The project - funded by the US National Science Foundation, Nasa and the British Antarctic Survey - was so logistically complicated that it took seven frustrating years to plan.

Even with that degree of organisation, the venture was still incredibly harrowing at times for the 800 people involved, and sometimes even tragic.

In January, three people died in a plane crash while returning to the main base from the site.

The challenges and successes of the two-month endeavour are being highlighted this week at an international workshop on glacial ice fracturing at NYU Abu Dhabi.

Gathering readings from the hard-to-reach places under the ice has required somewhat unorthodox methods in the past.

Dr Holland, who is from Newfoundland and Labrador on the icy north-east coast of Canada, teamed up with the Greenland department of natural resources last year to tag ringed seals in the Arctic with transmitters.

They sent back details of water temperature, salinity and depth from locations under the glaciers and through the fjords that no human could reach. Some data was extracted from more than 500 metres down.

However, it is underneath the largest mass of ice in the world in the Antarctic that scientists have been most eager to explore. Data from the most remote glaciers has been limited to satellite-based measurements and temperature probes dropped from helicopters.

"When you think about what is happening to sea levels, you have to take into consideration the big picture, the planetary picture - if the ice only behaves in response to the ocean, if the ocean only delivers warm water, or not, and does it push it one way or another," said Dr Holland. "What are the winds doing to the ocean? This is about filling in a missing piece. Right now there is just not enough knowledge."

The Pine Island Glacier Ice Shelf project began to take shape in 2006. The site, a floating part of the glacier more than 2,200 kilometres from the nearest research base, could only be reached a few months each year by aircraft that land on skis.

The biggest hiccup came when it was clear that a small fixed-wing aircraft would be too dangerous to fly the needed equipment to the site. A helicopter would have to transport the people and tools from a main camp about 80km from the site on the West Antarctic Ice Sheet. That required the construction of a 3km runway further inland, so that a ski-equipped US military cargo plane could safely land with the helicopter on board.

Once on the island, researchers would experience disorienting whiteout conditions, gale-force winds, temperatures well below freezing and a ground of pockmarked sharp ice where they had to set up camp.

Dr Holland and Robert Bindschadler, an emeritus glaciologist with Nasa's Goddard space flight centre, scouted out the Pine Glacier Island ice shelf in 2008, when Dr Holland installed a nearby automatic weather station. At the time, scientists had doubted it would be possible to reach the ice shelf.

The floating sheet of ice is "where the action is taking place in Antarctica", said Dr Bindschadler. "It only can be understood by making direct measurements, which is hard to do.

"We're doing this hard science because it has to be done. The question of how and why it is melting is even more urgent than it was when we first proposed the project."

This season, the three teams each spent two to three weeks at the site, for a total of two months. Permanent weather stations and video cameras were installed, and the ice shelf's cavities were mapped by detonating small explosions to track waves of energy, a technology known as reflective seismology.

Using a hot-water drill, engineers melted a small diameter hole through the ice shelf to reach a depth of 500m. A small motorised sensor was dropped through, attached to a fibre-optic cable anchored to the surface. The ice immediately refroze around it.

Through the cable, a laser light shoots down and back, and can read temperature at one-metre intervals based on how the water scatters the light.

The sensor, pacing up and down from the bottom of the ice to the sea floor, will continue to send back laser readings of distributed temperatures every 15 seconds over the course of the year. Weather stations established by Dr Holland will send the information back by satellite.

"This is the first time we have a year-round temperature and, as we collect this year-by-year, we can find out what the pattern of change is and what happens to this glacier through the seasons," he said. "When is it warm underneath? Is one year different from the next? This is what we will soon find out."

Comparing that data to planetary wind data will help the scientists explain any changes in water temperature under the glacier.

And that should help them work out how much the seas will rise - and when.