Measuring a Glacier’s Motion
WHILLANS ICE STREAM, ANTARCTICA– There are two basic projects that we are working on through our field work in Antarctica. One is looking at changes in the ice surface motion through time. To do this we make three types of GPS measurement: 1) continuous stations which measures a position every 10 to 30 seconds; 2) repeated measurements of poles stuck in the ice surface. 3) Kinematic lines (GPS is affixed to a snowmobile and we drive it around). The last technique does not give us velocity information, but the topography of the ice sheet.
See us installing a new GPS station in the video below. We previously assembled the tower, which contains solar panels and wind turbines, to charge the batteries. The batteries and the GPS hardware are in the gray cases. We use towers to keep the solar panels from being buried by accumulation and drifting snow. Note the old station in the foreground and how close it is to the snow surface. This video is played back at 15x speed.
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We always have a handheld GPS on while we’re driving our snowmobiles, just in case we get lost or conditions change and we can’t see. This way we can know where we have gone and were safety lies. I compiled all of our GPS tracks and made this map.
We have ten GPS station around the ice sheet, plus a few other locations of interest (seismic instrumentation or flag pole to re-measure) which we visited at least once each during our field season. I drove over 400 km during our 4 week field season.
We can use this kinematic set up to measure surface elevation and if we have multiple measurements, as in the image below, we can see changes in the ice surface topography.