With the instrument panel safely in the lab now it is Pete and Denis's job to clean it thoroughly and repair the load sensors. As they are doing that Miriam is up in the ice cave taking a sample of the sediment that has frozen itself into the ice. As the gradation of the rocks occurs from the glacier sliding it makes a lot of fine particles of rock that oddly get mixed into the ice in large layered bands. Miriam will later look at the density of the sediment and the rock sizes to get information about the glacier. She has sampled in the same place over multiple years. The ice core samples are long vertical chunks of ice that she dislodges with a chain saw. It is pretty loud in the cave, and these electric chain saws are four times more powerful that the ones in the US because they run off of twice the voltage here.
To get a sample of the sediment layers in the ice you have to chainsaw a long vertical section. They use an electric chain saw operating off of 220volts resulting in a very powerful saw.There are many bands of sediment separated by clear ice. The pattern seems organized yet the spacing seems random. The final layer that touches the blue ice is very distinct. The sediment if from the grinding of rocks at the bedrock interface. It is not known why you have layers like this.
Small ice crystals develop at the base of the glacier. Elsewhere you can see pockets of liquid water trapped in the ice.. the temperature is right at freezing.
We use the freezer to store samples and to store food. Lots of sausage on the first shelf.
A very important sensor is the friction plate that goes into the vertical shaft. Pete and Denis continue the process of testing the sensors. It is a really unique sensor, no one else in the world tries to do this kind of experiment. The granite friction plate will measure the forces exerted by the glacier. To do this they will measure pressure using four load sensors that must first be tested to see if they are operational. The sensors work by using a very simple principle. Imagine holding a rubber band in your hand. As you make it longer or shorter you can change the pitch that you can hear when you pluck it. Inside the load cell is a tiny wire. It changes its length when the top and bottom are smushed by the glacier. This means that it will emit a different "pinging frequency" when the weight of the glacier is on it. You can actually hear the soft musical pings coming from the instrument when they ring it like a bell, It is comforting to know the glacier will have something to listen to as it grinds about. The friction plate must only measure the friction on the top of it, where the glacier is...and not where the glacier is not. So the bottom off the glacier has a ball bearing plate to rotate about. It is very rusted and takes awhile to clean up. Since this is the only instrument of its kind, the data it produces is curious. The researchers published a paper on their results several years ago. It shows that the shear stress gradually increases, that is the drag of the glacier seems to get stronger over then next 100 days or so and then levels off. There appears to be a dip in the shear around May 15th or so that correlates with observations weight changes of the glacier and water pressure readings, the drop in shear likely means the glacier is slipping over water. The overall conclusion is not known. So this is a work in progress, by repeating the experiment it would be hoped that something consistent will result. In geology, it is difficult to repeat things because of the cost and trouble of replacing sensor in such remote regions.
The bearings on the friction plate are all rusted and need to be greased before they are placed back in the ice. The bearings are needed because you want to measure the friction of the glacier, not the friction of the holder, they allow the granite slab to rotate.
This is a very rare sight. It is an extremely rare opportunity to be able to actually see a glacier sliding on the bedrock from beneath. While everything here is grey, you can still see to the right the darker color is the dirty ice, while to the left is the granite bedrock, In another day this ice will have moved about half a foot. Eventually it was melted away.
This is custom made, only one of these in the world. This is the only place where you can measure the friction of glacier ice over bedrock. This plate of granite is where the glacier will slide across. All the instruments are placed under this slab.
Ultimately it all comes down to the data. Prior years have shown interesting things, like a decline in shear when the water is present, and a gradual increase in shear for the first twenty or so days the instrument is in place.
A typical field lab is rather crowded, this is in a small mobile home.Lunch is in a separate warm room with a sink. The lunch is mostly fish, salami, cheese and Wasa bread.You have to wear slickers like these to keep off the constant drip of water from the ceilings and walls and melt hose. If you are in a drier area you have to wear overalls.The ice is constantly moving, it has almost completely shut off the horizontal shaft from the vertical shaft.
The evening is spent in the lab working and in clearing out rocks above until midnight again. I listen carefully to the sounds in the tunnel as I walk back, I have concern for Jens and Arla.
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