Deep Breaths in the Snow
Dec 8, 2012
This year, my research project will be to analyze the gas exchange between the snowpack and the atmosphere. Gaseous chemicals such as ozone, nitrogen oxides, methyl mercury, and others are all related in a photochemical cycle that change their speciation (molecular form) in the presence of light. Even though there are 24hrs of sunlight in Antarctica during the austral summer, the sun is stronger at noon than it is at midnight, and these chemicals can either travel down into the interstitial air of the snowpack (the space between snow flakes) or rise up into the air above, depending on the sunlight and the chemicals’ reactivity and concentration gradient. This creates a diurnal cycle where certain chemicals rise into the air above during the day, while others bury themselves below, and they each reverse this process at ‘night’, even when the sun is still out (because the sun is very slightly ‘weaker’ at night).
In order to measure the concentration of these gases at various depths, my lab team built two instruments we called ‘snow towers’, shaped sort of like small ladders, that we buried within the snow. Each rung of the buried ladder very slowly and gently measures gases over time so that a depth profile can tell us how the gases move into and out of the snowpack. A nearby met (meteorological) tower measures the same gases at increasing heights in the air above, along with wind turbulence and air flow, and together all of this data is compared to solar radiation levels in order to identify this cycling activity.
One of the snow towers and a view of the Antarctic Plateau behind it. The grey tubes slowly capture gases and funnel them through buried tubing into our underground lab, where they are all measured and analyzed.
One of my teammates climbing up the met tower, where gases are measured up to 10 meters high. I quickly learned that climbing the narrow met tower in large Antarctic boots is much more difficult than it seems.
After climbing the tower one day, I made a short video showing these instruments. I’m a little winded in the video because we’ve only been at Concordia for a few days so far and it takes a while to acclimate to the very high altitude here (the ice sheet at Dome C is at a physioaltitude of 12,460ft, which means there is less oxygen and it takes a few days to adjust) but the video offers a simple view of our lab. Now, one last thing- in the video, why do I keep repeating the phrase ‘snow surface’ instead of saying ‘underground’? Because since the continent is covered by the very large Antarctic Ice Sheet, we’re actually standing on roughly 10,500ft of ICE, not ground/earth. (Even though I do still slip and say ‘underground’ often, but not in a literal way.) This means that depths of snow are relative; we base everything off of what the surface is when we start measuring, and if things get slightly buried by new snow on top (not much, since there is actually very little snow accumulation here), we can simply say the instruments sunk a few centimeters below what the ‘new’ surface levels are.