3585 meters above sea level
After traveling all day, tonight we set camp at a location where satellite imagery told us we would experience very different snow structure across an expanse of several kilometers. Standing outside the vehicles and looking out across the expanse of the ice sheet, on casual inspection it looked pretty much the same in all directions; very small surface roughness with evidence of shifting winds, including occasional patches of shiny wind-induced surface polish.
Yet our crevasse-detection radar had recently begun showing signs of unusual vertical features in the top ten or so meters of snow, and upon closer inspection we found thin cracks across the snow surface that penetrated at least several meters into the snow. In addition, the surface wind pack surface layer concealed increasingly large snow crystals in the top meters.
We traveled several kilometers away and indeed found very different subsurface snow conditions, with no cracks, and snow crystals almost the same size through the top meters. An almost imperceptible rolling topography had induced different amounts of snow accumulation at the two sites, resulting in very different structures in the subsurface snow. From space the difference was clear, yet only after digging and sampling in the snow did the contrast become striking while standing on the ground!
This contribution is from the log of the Norwegian-US Scientific Traverse team, who are en route from Troll Station to South Pole Station. Much more information can be found here.
Image caption: The subsurface snow structure in the foreground area is strikingly different than at the camp site in the background, 2 kilometers away. The surface topography that induce the differences can barely be perceived in the image — see the vehicle track that disappears in the middle ground. Photo: Stein Tronstad.