The lakes in the Dry Valleys have permanent ice cover with thicknesses measured in meters. But, the permanent ice does not extend all the way to shore. Shallower areas are covered with temporary ice that melts out each year to form a moat. Here is what F6 looked like when we arrived at the camp on November 10, 2014.
Before the moat forms we use the ATV to get to the nine gauges around Lake Fryxell. When the moat is narrow, we can step across it or use an extension ladder. Here is Rob setting up the second location for the extension ladder at F6.
The original location for the ladder is in the background, just to the right of the larger boulder in the shallows. You can see that the original location has melted out much farther. The new location worked for a few days, and then the ladder broke through. It was time for the SS Von Guerard.
We can get on the ice on the Von Guerard, and drive across the permanent ice to the Lake Fryxell camp where the ferry SS Fryxell operates. The Fryxell has a pulley arrangement so that more than one party can use the boat by pulling it to shore or to the ice. By using the SS Von Guerard and the SS Fryxell, we can continue to use the ATV to get to the Canada Stream and Huey Creek, saving us two long hikes.
Once the moat becomes too wide to step across safely at a gauge, we have to walk to that gauge. In the space of a week the moat grew to the point where we now have to walk to the seven other Fryxell gauges. Here is the moat on Lake Fryxell at the Delta Stream.
At the start of the season, the frozen moat, that is the ice that froze last fall, was very smooth and very clear. As the season progresses, the moat ice becomes an opaque white. I’m not sure why. Farther from shore was “cupped ice”, which is ice that has been frozen for more than one year, but not for many years. This ice will be thicker, as it has been through at least two cold winters. Permanent ice has been frozen for many years, and is meters thick. When the wind deposits sediment on it, the permanent ice can evolve into strange shapes.