I've never stood on a glacier, but I've been near them. Glaciers are like volcanoes: beautiful, dangerous, very hard to get to, and even harder to study. But scientists are getting inside glaciers, sometimes very far inside, by using virtual eyes or by putting their actual hands on the glacier's belly.
Glacier Radar
Radar interferometry is one tool recently turned upon Antarctic glaciers. It involves taking a pair of radar images of the same place, acquired by satellite at different times, and lining them up. By mathematically extracting the difference between the images, we can create a wild-looking picture that shows the ice motions in total detail for the whole glacier at once. (The technique is used similarly in earthquake displacement studies, for instance after the Hector Mine earthquake in 1999.)
In one such project, Hermann Engelhardt's team from Caltech used the technique to measure exquisitely small changes in the elevation of Rutford Ice Stream. On the images they could pick out the hidden point where the ice stream runs into the sea. They showed that this grounding line has moved inland measurably—more than a kilometer—since 1980. Nobody can say yet whether that is due to rising sea level or something else.
Glacial Penetration
Another approach is to get onto the glacier and give it the third degree. The Worthington Glacier Project is a good example. This project of the University of Wyoming and the Institute for Arctic and Alpine Research (INSTAAR) took a small, fairly tame Alaskan glacier in the Chugach Mountains and examined its innards closely.
The interrogation began with ice radar mapping, which penetrated the ice to the rock bed beneath. Then 30 boreholes were drilled into the ice with an ingenious hot-water drill. Instruments tracked the bends and twists of the holes for a whole summer (including downhole video), then the data were visualized to show graphically how the ice actually moves inside a glacier. Other more traditional techniques included aerial photography, and laying out lines of stakes on top of the ice and recording their motions throughout the summer.
Under the Glacier's Belly
But to me the ultimate thing would be to actually stand at the bottom of a glacier and watch it work, grinding its way along its rocky bed. The geophysicists who make numerical models of glacier behavior are interested in that region, too.
It turns out that there are at least three places where that has been done. One is France's Argentière Glacier in Chamonix, near Switzerland, where temporary studies have been conducted. The other two are in Norway, beneath the glaciers Bondhusbreen and Engabreen. In these cases the local hydroelectric power company bored tunnels to collect meltwater, and some accommodations were made for scientific research. One group from the University of Minnesota went to Engabreen in the mid-1990s and cemented instruments at the bottom of the moving ice, including some thick quartz windows, and settled down to watch the glacier grinding along. Their results are listed below.
LINKS
Worthington Glacier Project home page at the University of Wyoming
Svartisen Subglacial Lab at Engabreen by the Norwegian energy agency NVE
