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Posts Tagged ‘ice layers’

Last summer, just before IGERT cohort 3 journeyed up to Summit Camp, the Greenland ice sheet experienced extensive surface melting. Much of the top layer of snow melted and dripped through the snow near the surface. But of course in the cold weather, it didn’t remain as water for very long! This water refroze in the snow, forming flat layers of ice which are connected to one another by vertical columns of ice (see the picture below for an idea of what this looks like). Since last summer, it has snowed quite a bit at Summit, so now the ice layers and the columns that connect them are buried. We would like to know what this ice layer looks like and how many of these ice columns formed in areas around Summit Camp. Now don’t get me wrong, I love digging a good snow pit, but unfortunately, we can’t dig up miles of snow. What we would like is to see what’s under the snow without having to break our backs.

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A view inside of our snow pit. I am pointing to the vertical ice column which is right beneath an ice layer that extends all the way across the snow pit. (Photo: Jim Lever)

Using ground penetrating radar (GPR), we can look down below us and “see” the layers of snow upon which we stand. We can also see when there is something different in the snow, like ice which is visible because it has a much higher density.  In our first week, we have spent some time getting the radar system running and testing it out by setting it in a sled and pulling it behind as we walk. One question lingered – is the radar “seeing” what we would see in real life? For that, we had to dig! We dug up a snow pit to see just how prominent the ice layer actually is and to determine if we could see any vertical ice columns. Sure enough, both the ice layer and even a vertical column were easy to find in the snow pit!

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Walking off into the distance with the ground penetrating radar in tow. (Photo: Jim Lever)

Though pulling sleds wasn’t so bad, I would sometimes sink nearly to my knees in snow drifts which made keeping a constant walking pace tough. Enter Cool Robot – an autonomous robot (designed right at Dartmouth’s Thayer School of Engineering and wired up by IGERTeer Ben Walker!) that can follow preset directions and drive itself in nice, well-paced patterns across the snow while towing the radar system. We set up a square grid for the robot to follow that was 50 meters on each side. The robot is light and reliable – not sinking into the snow, keeping a constant pace and following our directions within about a meter of the set path. So I’ll admit, Cool Robot has me beat by far in the ability to run a GPR survey. But hey, at least I know not to run straight into the flag markers all around camp! : )

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Cool Robot crushing the competition in quality of GPR surveys! (Photo: Jim Lever)

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