By Nander Wever
Earlier, we wrote how important snow is in the mass balance of Antarctica. During the campaign, we regularly survey the snow structure. We are particularly interested in the snow density.
The classical way would be to dig snow pits. However, snow pits are very time consuming, and you basically only get information from one specific spot.
We know that snow in Antarctica is highly variable. Not only is there a difference between snow in the interior of Antarctica and near the coast, even at meter distance the snow can be very different due to wind erosion and deposition.
We use a special device to survey the snow microstructure, called a Snow-Micro-Penetrometer (SMP). Whenever possible, we take SMP measurements. For example during our traverses to the drilling sites, regular stops to rest, eat, refuel are done every 30 km. We then quickly take about 10 to 20 samples of snow density in the upper 1 meter of the snowpack, spaced 4-5 meter apart.
This gives an estimate of the snow properties and the variability in that area. We also do this at important sites, such as near weather stations. With the instrument, we look for variability of snow properties, depending on location. We found already very different snow structure based on distance to the coast, elevation and wind speed.
The SMP is a high precision instrument, designed, built and provided to us by the Swiss WSL Institute for Snow and Avalanche Research SLF. It has a very sensitive force sensor, which measures the force needed to penetrate the snowpack with a constant speed.
This force can be related to density, and snow microstructure. It allows to quickly survey the snow surface; one measurement takes only about a minute. The deeper below the surface, the older the snow is. This way, we can investigate the history of the snowpack.
The area we are visiting has roughly 30 cm up to 1 m of snow accumulation per year, meaning that we can for example see how the snow looks like when it falls in winter, when no one is there to observe it.