Going wireless in Greenland
17 June 2019
Glaciers are beginning to move faster than they have ever done before.
Our warming world is melting the ice on top of glaciers, causing meltwater to trickle down through cracks and holes and act as a lubricant over which the glacier can roll – much like shopping items on a conveyer belt.
When a glacier slides downstream and eventually meets the ocean, it melts and causes sea levels to rise with potentially devastating effects for coastal communities around the world.
Naturally, scientists have been trying to measure the amount of meltwater that sits beneath glaciers for a long time in order to better understand why they are moving so fast and how they will change in the future.
However, it is a task that is a lot more challenging than it initially sounds.
That’s why scientists from Cardiff University, who head out to Greenland this month on two separate expeditions, are embracing modern wireless technology and employing never-before-used techniques with a rather unusual array of scientific kit.
Leading the work is Dr Liz Bagshaw, from the School of Earth and Environmental Sciences, who, for the past 10 years, has been developing tiny wireless sensors that can gather measurements from more than 2000 metres inside a glacier, whilst at the same time withstanding the extreme conditions.
“Scientists have traditionally sent sensors down to the bottom of glaciers on extremely long and flexible cables,” said Dr Bagshaw.
“The problem is that if you leave them there for long enough to get accurate readings over a longer time scale, the movement of the glacier ends up snapping the cables. That’s why we need wireless sensors.”
The initial prototypes developed by Dr Bagshaw and colleagues from Bristol University were made from Christmas baubles, which provided a perfect shell from which the case of the sensors could be moulded.
“After exploring a number of different possibilities, it turned out that Christmas bauble moulds were absolutely perfect, because they were cheap, could be made strong, and could fit into meltwater channels under the ice,” continued Dr Bagshaw.
The technology, now known as a ‘Cryoegg’, has been scaled up to the size of a grapefruit (around 12 cm in diameter) and includes a tiny circuit board within a mould that can measure the pressure, electrical conductivity and temperature of the surrounding meltwater.
The individual measurements that the sensors collect are very simple; however, combined they provide the team with a very detailed picture of the conditions underneath the glacier.
One of the biggest challenges the team face is retrieving the data from deep within the thick ice.
The project is helped by two international ice boring missions: RESPONDER, which is using hot water to make a deep hole in the ice, and EGRIP, which is extracting a 2.5 km long ice core using a specially designed drill.
The Cryoegg team will use these boreholes to access the bottom of the ice. Once the sensors are inserted into the boreholes, it’s more than likely that the ice will freeze over, making it impossible to physically retrieve the sensors.
As such, they rely on the wireless transmission of the data; but finding the right frequency is key.
“We find that VHF radio signals – slightly higher than those used for FM radio - are the best to use as they have a low enough frequency to penetrate the ice,” said Dr Mike Prior-Jones, an electrical engineer from the School of Earth and Environmental Sciences.
Finding radio technology that could be integrated into the sensors proved to be difficult, but a solution was found using components from gas smart meters that are commonly used in Germany.
“This technology was ideal for us because it is intended to be used in battery powered devices,” continued Dr Prior-Jones.
“For gas metering, they power the radio using a battery that lasts more than five years. The whole radio technology is optimised around using very little power from the battery. In our case, we want the instrument to make a few measurements a day and send them back to the surface. The rest of the time it’s asleep, in order to save the battery.
“So this technology was a great match – Cryoegg wakes up, makes its measurements, transmits them, and then goes back to sleep again within a few seconds. We expect that it will operate for more than a year underneath the glacier.”
The final piece of the jigsaw was finding a way to retrieve the signals on the surface of the glacier. As radio signals have a low frequency, a relatively large TV-style antenna is needed to pick up the signals. Furthermore, the antenna must be suspended so that it can point down towards the ice.
Dr Prior-Jones found the perfect solution after friends suggested using Quadro – a children’s climbing frame product that can be constructed like scaffolding to produce support structures in a variety of size and shapes. More importantly, it is very lightweight and can be easily transported, which is vital when planning an expedition to Greenland.
“The Quadro system is perfect, because it’s non-metallic and very versatile. Any metal in the antenna support would disturb the radio waves and might cause us to lose the signal. It also packs up very conveniently for transport, and we can build it into different shapes to fit around the terrain if we need to,” said Dr Prior-Jones. “We’re grateful to the Quadro company in Hamburg for donating us their product for the expedition.”
The overall result is a system that will be able to accurately monitor conditions within the glacier over an extended period of time. In practice, the sensors will be dropped into boreholes that will be drilled into the ice and will power up a couple of times a day to take its readings, after which it will ping data up to the antenna before going back to sleep to preserve its battery.
“The most exciting part of this project is the way in which we’ve been able to adapt to the extreme conditions posed in Greenland using cheap and readily available kit that already exists. This is true science in action – tackling large-scale problems using knowledge, creativity and teamwork,” said Dr Bagshaw.
The project is funded by the UK Engineering and Physical Sciences Research Council.