Detecting crevasses in Antarctica

Travel in Antarctica can be slow and dangerous. Glacial land ice is always moving, and this stress causes the ice to crack. Sea ice is also dynamic and under stress. The stress causes crevasses – holes and deep cracks in the ice. 

Crevasses have been an issue for humans from the early days of dog sleds and tractors – even for today’s PistenBully and Hägglund vehicles. Technology has helped to make the trip safer, but not always faster. 

Remote sensing radar from satellites is often the first step to mapping a journey. It can spot cracks that are not visible due to snow cover. 

Journeys to remote field sites also use ground-penetrating radar – fixed on a gantry fitted to the front of the PistenBully. The gantry is 20 m long, so travel is slow and careful observation is a must! 

Antarctica does have ice roads – for example, the South Pole Traverse is a 1,500 km route across the Ross Ice Shelf to the South Pole. Ice roads are constructed by levelling snow and filling in and/or avoiding crevasses and other dangers. The roads are not paved, so they are marked with flags to aid navigation. 

There are shorter roads that link Scott Base with the local airfields and the United States McMurdo Station. 

Professor Dave Prior, from the University of Otago, tells us what makes crevasses so dangerous and how radar helps to identify their locations. 

Jargon alert 

• POB – people on board. 

Questions for discussion 

• What makes crevasses so dangerous? 

• What do crevasses look like in the radar images?  

• Why do you think the vehicles in the tractor train are so spread out when travelling? 

Transcript

Pepper Cook (Driver)

Hey there, just crossing the American Transition with eight POB heading out to the AFT camp for the night. Over.

Voiceover

Travel in Antarctica – whether on foot or in a vehicle – requires careful preparation due to the many risks.

Professor Dave Prior

One of the big risks on any bit of ice are crevasses. And you can have crevasses which a person could fall down and you can have them big enough that a Hägglund could fall down. So we definitely want to avoid that kind of thing. So one of the things we went through right at the start of this is that one of the guys who works part-time for Antarctica New Zealand, Dan Price, did a thing called a satellite-informed crevasse advisory. So he uses a certain type of satellite image, which enables you to see through the snow because it’s not a visible image, it’s a radar image, so that you can see cracks everywhere.

Voiceover

A trek across the polar landscape to a distant field site then uses radar that’s much closer to the ground to add another layer of safety. This radar is attached to a leading vehicle in a tractor train.

A tractor train is an innovative system of modified tractors and sleds that move people and equipment. The first vehicle in the train is usually a PistenBully with a crevasse detector on the front. This is a safety device that scans the ground for cracks, holes or potential danger within the ice. Inside the PistenBully, someone must carefully monitor the video screen. The vehicle has about 20 metres in which to stop, so the monitoring crew needs to be very, very vigilant.

Acknowledgements

Professor Dave Prior, University of Otago
Pepper Cook, Antarctica New Zealand

Crevasse warning sign, man near radar arm, tractor train stills, and vehicle with radar arm, Neil Silverwood
Person scaling crevasse, inside a crevasse and satellite image, Daniel Price
All footage courtesy of Carol Brieseman and Dianne Christenson
Carol Brieseman and Dianne Christenson visited Antarctica with support from the Antarctica New Zealand Community Engagement Programme