Friday, June 28, 2013

Third day is a charm...

Our first two days in Nome consisted of warm temperatures and clear skies. Today's forecast shows no change in temperature, but a possible chance of rain in the afternoon. Weather in Alaska, particularly along the coast, is hard to predict so we left Nome prepared for whatever conditions Mother Nature had in store for us. We knew that mosquitoes would be part of the forecast, that we could definitely count on!

Our group got together last night and looked over a series of satellite images that Santonu had prepared and brought with him. After some discussion, it was decided that we would visit a more recent drained thaw lake basin along the Kougarok Road. The lake basins we worked at earlier in the week were, according to Guido, several thousand years old. The basin that we had picked out for today was much younger; in aerial images it showed up as a wetland in the 1950s, a lake in the 1970's, and then drained just within the last 5 years. This meant that it was a good analog for what might be expected in a changing climate. That is, a landscape in transition at time scales relevant for inclusion in climate models. 

We arrived at the site mid-morning and went about our routine. Jenny and Guido quickly set up the GPS base station, while the rest of us walked a short distance across the tundra to the basin of interest. What we found was a basin 150 to 200 meters in diameter. The basin was 5 to 10 meters below that of the surrounding tundra. Guido mentioned that the lake most likely drained when the down-slope rim for the basin was breached by high water and set-up conditions favorable for thermal erosion. Indeed, when we walked down to that area, there was strong evidence of a deep thermal gully running out into the tundra. The basin itself was dotted with small ponds several meters in diameter and large rounded mounds that were rich in peat. These mounds were exceptionally dry and plant mortality was severe. In some cases, large areas were completely lacking live vegetation. This was similar to what we see in terms of vegetation dynamics on high-centered polygons in Barrow.

As we had in previous days ,we laid out transects and began collecting data. Guido was curious about the ponds within this basin and started mapping their location. Although polygonal structures within the basin were only weakly visible, the ponds to my eye were mostly in trough intersections. Guido probed a little to determine their depth and they were maybe on average a meter deep. However, in one there was a much deeper area that ran lengthwise across the pond, leading Guido to speculate that this could be an area were the underlying ice-wedge had melted. In some cases the water was actively running through these areas and in others the ponds were static. In the latter case, the water was 13 to 15C, warm enough to certainly contribute to a deepening or expansion of these ponds. The surface and subsurface interactions are undoubtedly strong in these young and changing drained thaw lake basins. Since our team has such a good geophysical characterization capability, this is something that we are interested in pursuing further.


Having worked hard, we left the field today very satisfied with what we had seen and accomplished. It did rain, but not enough to stop our work for very long. The topic of discussion over dinner was whether we could locate any more of the young basins along either the Kougarok or Council Roads out of Nome. Guido, Dan, and Santonu were going to take a more extensive look at their maps and see. Last year, we saw small drained lake basins out the road to Council and Larry Hinzman, Chief Scientist for the NGEE Arctic project, has studied several "disappearing lakes" in this region over the last decade. Whether these lakes drain due to surface water drainage in continuous permafrost like the one we saw today or more subtle connection to groundwater in areas of discontinuous permafrost like Council would be an interesting research question. If such features become more prevalent in the future because of regional warming, then they represent processes that could be incorporated into climate models for improved predictions. This is, of course, the goal of our project.