Ozone at Summit, Greenland as Seen in Surface and Profile Observations

Continuous measurements of ozone at the surface have been made on the high elevation (3200m) Greenland ice cap at the Summit Observatory for over seven years. For the past five years ozone profile observations that extend from the surface to over 30km have been conducted using balloon-borne ozonesondes. This site is unique in the high latitude Arctic because of its elevation and isolation from nearby anthropogenic pollution sources. At the surface ozone is often representative of air in the free troposphere that is influenced by transport from the stratosphere but also by distant sources of air mixed into the free troposphere from the boundary layer. For the most part, however, the surface ozone distribution is dominated by what can be considered well mixed background air. During 2008 daily ozone profile measurements were made for three week periods during April and June-July that give a picture of the day to day variability throughout the troposphere and stratosphere. In the troposphere at the altitude of Summit and higher the seasonal pattern is similar to what is seen at other longer term ozonesonde locations such as Resolute, Eureka, and Alert. However, at lower altitudes the seasonal pattern at other arctic sites at both high latitudes (≥70N) and lower latitudes (~65N) is significantly different. Only during the winter of 2005 were temperatures in the stratosphere cold enough to indicate the significant presence of polar vortex air over Summit with possible stratospheric ozone depletion resulting from halogen activation. In subsequent winters the vortex has been positioned further to the east.