Ozone and Snow

Blog: January 2010 - Scientific results

January 14th, 2010

The snow surface near the instrument tower at Summit, during Greenland's summer.

It's a new year, and time we took a look at where we are in our measurement campaign.  We have been collecting data since 2008 at Summit, throughout the year and under many kinds of conditions.

Our results, shared with colleagues at the AGU Fall Meeting last month, are starting to take shape.

The sunlit snowpack appears to be one of the most photochemically active environments, capable of altering the oxidative capacity of the overlying atmosphere. Year-round measurements of reactive gas concentrations and fluxes inside and above the snowpack at Summit show a strong seasonal cycle. Consequently, in modeling, the use of commonly applied constant surface deposition rates does not provide an adequate description of fluxes to the snow surface. Gas emissions from the snow need to be considered as well. We have developed new flux parameterizations, shaped by our field data, that incorporate the snow physical and chemical properties and their seasonal changes.

Long-range transport of anthropogenic and biomass-burning emissions to the Arctic is known to impact ozone precursors and ozone both within the Arctic and downwind regions. We have gathered field data at Summit on nitrogen oxides, total reactive nitrogen species, peroxyacetyl nitrate (PAN), and non-methane hydrocarbons, providing the most complete seasonal coverage of these compounds affecting tropospheric ozone in the Arctic.  We analyzed the compounds to determine their interannual and seasonal variations and speciation in the Arctic with a focus on long-range pollution transport events and their impact on ozone production. The observations show a well-defined seasonal cycle in total reactive nitrogen species with higher mixing ratios during the arctic springtime. Throughout the year, total reactive nitrogen species exist primarily in the form of PAN and during specific pollution events PAN can account for up to 90% of total reactive nitrogen. We see large enhancements above background levels in NOy and NMHCs during the summers of 2008 and 2009, which are attributable to long-range transport of boreal fire emissions. One biomass burning event in particular, in August 2008, saw significantly elevated levels of carbon monoxide, NOy, PAN, and ozone at Summit over a 2-week period. Using FLEXPART transport simulations we identified a number of anthropogenic events during fall-winter 2008, which were strongly dominated by emissions from North America.