Two figures clamber up a metal tower in boots and hard hats. The wind is cold, just a few degrees above freezing, but the sky is sunny and cloudless. The tower is at the highest point on the Greenland ice sheet, and the scientists climbing it are setting up instruments that will measure ozone moving in and out of the snowpack below.
The scientists are at Summit, Greenland, a scientific research station in one of the world’s most pristine environments. They are a long way from their homes at the Institute of Arctic and Alpine Research at the University of Colorado-Boulder and Michigan Tech, looking for answers about how ozone is created and destroyed in snow.
In snow-covered landscapes, ozone in the atmosphere can be both destroyed and formed through chemical and biological processes occurring in the snow. The limited measurements available to date show that these processes are big enough collectively to affect arctic ozone levels over large regions; but we don’t yet know enough to understand the size of these impacts. Further, climate changes in the Arctic are more pronounced than in any other area on earth. The snow and ice environments are responding to these changes, and future trends in snow cover extent, snow depth, sea-ice extent, and permafrost extent are expected to be significant. As a result, it is important that we understand the current impacts of air-snow exchange upon ozone in the troposphere so that we can predict the effects of future changes in these processes.
Until recently, snow-covered surfaces were believed to be nearly inert with respect to ozone. However, in the last ten years it has been recognized that sunlit snowpacks are active photochemical environments that can significantly alter the composition of the overlying atmosphere. Snowpack processes affect ozone in the air in two ways: through destruction within the snowpack and through photochemically mediated release of ozone precursors that cause ozone production above the snowpack.
We know that snowpack processes on ozone can be significant and complex. We want to understand them better and fill in some of the gaps in our knowledge. To do that, we are going to measure and analyze ozone fluxes at Summit.
Detlev and Brie climb the instrument tower at Summit to set up some of their meteorological instruments, including a sonic anemometer (visible at left, behind Detlev's elbow). Photo: Brie Van Dam (INSTAAR).
This insulated, heated box at the base of the tower protects electronics for several of the instruments mounted on the tower. Over this winter, snowdrifts completely covered the box. Jacques will have to dig it out during a trip to Summit in February 2009. Photo: Brie Van Dam (INSTAAR).