31 July, 1997

Nevins journal 07/31/97

I spent the morning with Dr. Nelson and we reviewed the project work so far and I had a chance to see how the land forms that we are going to see look in a slide presentation.

The first land forms that we looked at were ice polygons and we talked a little about the possible causes for the differences in the structures. We also looked at the sampling process and noted that if you do not take care, you could wind up sampling in a way that hit only one type of condition. This could happen because the polygons are rather regular or uniform in size and if you happen to pick the right sample interval, you might miss entire sets of conditions when probing the depth of the active layer.

We also discussed the formation of lakes in the area we will visit and I was quite surprised to find out that the lakes had a shape and direction of orientation that was wind dependant. When I first saw the lake photographs I guessed that the long axis of the lake was oriented in the direction of the prevailing wind. It turns out that the direction of the long axis of the lake is perpendicular to the wind direction and a type of erosion of the permafrost is greatest at the ends of the lake that are at right angles to the wind.

Next we looked at another landform found that is known as a pingo. A pingo forms when a tundra lake drains part way and as the land refreezes, the liquid water is gradually squeezed into the center of the area and begins to push up the surface of the tundra into a large mound. A pingo continues to grow as long as this ice center is protected from melting by the covering tundra soil.

Another form that occurs in the bog areas is known as a palsa, which is a peat bog mound caused when an area in a bog is covered by a thinner layer of snow in a winter. The resulting greater freeze depth at that point causes a rising of that section of the bog and during the next thaw cycle the bog moss at that point dries out a little more than the surroundings do and the dry moss is a better insulator which reduces the thaw depth which causes the heaved area to stay higher than the surroundings which in turn causes another thin snow layer the next year and the repeating cycle causes the mound of the palsa to grow taller.

After we took a break, Dr. Nelson discussed the methods of data collection that are in use for this study. The data collected include thaw depth, temperature at several levels in the soil and above ground, vegetation type, soil type, altitude, direction of slope, and time interval. For those of you who have been working with graphing data in the lab, we also discussed the linear functions that the data showed along with the correlation coefficient of the function. More on this later.

In the late afternoon I met two more of the people that I will be working with, Kolia Shiklomanov and Mike Walegur, and they transferred the program to run the data loggers to my laptop and we did a few trial runs with a thermal logger. I went out to a site near Albany, (Thatcher Park, on the Heldeburg Escarpment) that Mike has running as part of his own project, and looked at his setup. Saturday we plan on visiting another site that he has in the Adirondack Mts. To check the site.

We ended the day by trying to work with a Global Positioning System (G.P.S.) which we will use to find some of the sites in Alaska. It is quite amazing to see the G.P.S. show a change in your coordinates as you walk. I need to sign off now to work with the G.P.S. for a while.