监视我们一生的变化

Greenland, rugged and wild, is covered by a massive ice sheet that represents roughly 80 % of its surface. Glaciers break free of this ice sheet and become slow flowing rivers of ice that are constantly moving, being pushed by their own massive weight towards the sea. There are many reasons why researchers have recently taken an enormous interest in studying the secrets of Greenland’s ice. One is that Greenland is especially vulnerable to climate change; the ice sheet is melting faster than any other body of ice in the world and the glaciers are moving ten times faster towards the sea than they did just five years ago. Another reason is that this country’s ice represents roughly eight percent of all freshwater found on Earth. Should these glaciers melt, the meltwater would be enough to raise the sea level by over seven metres (20 feet), displacing millions of people on this planet. This will have serious consequences on our environment, making it extremely important to monitor these changes, which are occurring during our lifetime.

总部位于法国夏顿的一名冰川学家卢克·莫罗（Luc Moreau）一直在研究西格陵兰岛的四公里（两英里半）宽的埃克斯式Sermia冰川，已有三年多了。Luc, along with, the SPELEICE association and the MONALISA production company, recently organised an expedition to collect data on the speed of this glacier’s melt flow and to understand how this glacier’s ice moulins (deep holes that transport meltwater through glaciers) affect the speed of its melting. Accompanying them was Farouk Kadded, product manager of Geomatics at Leica Geosystems France, and together they set out using the state-of-the art Leica Nova MS50 MultiStation and real-time GNSS positioning instruments Leica GS14 antenna and Leica GS10 receiver. The MultiStation was chosen because it was capable of making accurate, reflectorless 3D scans from a distance of 1 – 2 km (0.6 – 1.2 mi), was lightweight and compact enough to be carried in a backpack and was proven to be reliable and rugged. It was also the only scanner on the market that offered all four technologies needed: total station, scanning, GNSS and imaging.

测量EQIP Sermia的运动流程
During his last expeditions, Luc set up a camera that took pictures daily over the last few years. He was able to identify the changes in the glacier size by piecing together a “timelapse” film from the images taken by this camera. This film, when accompanied by the collected topographic data of the Leica Geosystems equipment, could be used to calculate the length and speed of the flow of the Eqip Sermia glacier.

在Luc和Farouk发现GS10接收器作为参考点的稳定地面之后，他们开始寻找冰川上的理想测量位置。这是迅速转移冰川表面的危险任务，并具有深厚的致命的冰纹。携带多阶段，三脚架，反射器目标，崎leica GS14天线和杆子，他们首先在马stable左岸上设置了多阶段，并在顶部使用Leica GS14 GNSS天线，以获得MS50的精确坐标，以测量MS50选定点在1.3公里（0.8英里）的范围内。此后，他们危险地越过冰川以定位反射目标。连续四天，他们在一天中的同一时间收集了位置数据，以计算24小时内的冰川熔体流量。

The glacier moved at a rate of up to 30 centimetres (12 inches) an hour, so the team had to work fast. Images were first taken by the MultiStation of several seracs, or ice towers, to help Luc and Farouk easily relocate the same points the next day.

结果证明冰川的运动up to 7 metres (23 feet) a day. The last measurements taken in 2012, revealed the Eqip Sermia moved 3 metres (10 feet) daily. This flow, when compared with other glaciers around the world, moving roughly 30 centimetres (12 inches) a day, is alarmingly fast. The team also proved the glacier lost roughly 500 metres (1,640 feet) in just the previous month. Another goal the team had set out to accomplish, that of using the Leica MultiStation to make a 3D scan for posterity of the historic cabin that French polar explorer Paul-Émile Victor used as a base for his expeditions, was also successfully completed. Also, a large lake several kilometres inland on the Eqip Sermia’s surface was discovered. Should this water somehow find its way into a crack, it could cause a glacier meltdown. Finally results also proved that the glacier is melting 100 times faster below the surface of the ocean than above.

Measuring the inside the ice moulin
After making the same, day long trek on the path explorer Paul-Émile Victor took to reach the glacier’s ice cap 60 years ago, the team set up camp and searched for a “moulin” to make the 3D scan. This scan would determine if the water inside a moulin did indeed reach the rock bed below the glacier. Why are these moulins so important to researching glaciers? With Greenland feeling global warming much more than the rest of the world, lakes of meltwater appear on the surfaces of the glaciers on very warm days. The excess lake water produces rivers that melt the ice at an alarmingly rate. If this water gets into a moulin, it will begin to swirl and erode the ice and find its way to the bottom of the glacier on Greenland’s bedrock. This water builds up under the glacier and works like a lubricant. The glacier easily slides on this water surface and the forces of gravity push the massive weight of the ice even faster, towards the ocean.

融水的旅程
Luc and Farouk managed to set up the MultiStation on the tribach inside an ice moulin to scan the details of the ice crevasse. With some moulins reaching depths of up to 200 metres (650 feet) , it was truly exciting. Never before has such an accurate scan be done of how the water’s flow formed nooks and crannies inside a glacier moulin, recording its progress to the bottom of the ice.

Working inside this hole is not without its dangers. Should the surface temperature fluctuate as much as 1-2°C (34-36°F), glacier water could start to melt and flow into the moulin, flooding everything. Scanning took an entire day, but they were able to scan the moulin in its entirety, measuring vertically, bit by bit, from the river that created it to its deepest part, collecting roughly 500,000 highly detailed points. Depth, circumference and width can all be provided by a 3D scan taken by the Leica MS50 MultiStation and the results were fascinating.

“The idea of measuring this way was to have all the dimensions of a moulin in order to appreciate its development over time and the deformation of the ice. The results proved very effective, the model visuals are excellent and the device well suited for this type of opening — provided you have good weather!” says Luc Moreau excitedly.

The 3D scan proved the Leica MS50 MultiStation’s versatility and its robustness under extraordinary circumstances. Its new programs and features that work together, integrate new technologies, making measuring far more reliable, quicker and complete, enabling researchers to receive the information they require. Working together with companies that are at the forefront of their fields, can only help researchers to advance in their understanding the changing climate.

Written by Farouk Kadded and Luc Moreau