Tuesday, January 14, 2014

More radar: Bisgletscher

Last week we took the radar to another spectacular spot: We flew up to Domhuette in Mattertal to look at Bisgletscher across the valley. Bisgletscher has been moving pretty rapidly and there is concern that pieces could fall off and threaten the road and railway near Randa.

Below is a view from Domhuette. The mountain across is Weisshorn, at 4,506 m. This picture shows 3000 m of vertical relief. The other side goes up by the same amount, making this the deepest valley in Europe. Just below the summit of Weisshorn is a hanging glacier that has lost major parts in the past. Further down is Bisgletscher, which we tried to survey this time. In the lower right corner are the leftovers from a massive rockfall that occurred in the early 90s.

Below is a radar interferogram calculated from two images taken 15 minutes apart. The colorscale extrapolates the motion that occurred in those 15 minutes (about 10 mm) to meters/day. So the glacier (circled in red) is moving at nearly 1 m/d towards us observers. The non-zero motion that shows up for bedrock is atmospheric noise that I have not yet removed.

Monday, January 6, 2014

Glacier speed with radar

We did a short day trip to Kleine Scheidegg (on the way to Jungfraujoch) to see how well we can measure the flow of hanging ice with a ground based radar interferometer. This is a nice instrument, built by Gamma Remote Sensing that can measure displacements as small as a few millimeters. In the case of Eigergletscher it took a few hours to get sufficient displacements.

The radar, ready to go.

And here is Eigergletscher as seen by the radar. The picture shows an interferogram taken from two images separated by several hours. The colored fringes near the center correspond to 8 mm of motion for one color cycle. Since we can count about three cycles, that corresponds to 24 mm of displacement.