Arctic Ozone Depletion Events

Tropospheric ozone, and particularly its regionally diverse interactions with the Arctic ecosystem, make it another trace gas of interest for IASOA science.  For example, surface ozone depletion events were first observed at Alert and Barrow and were linked to atmospheric halogen chemistry (bromine) processes.  Recent research indicates that the ozone depletion events are related to increased open ocean area as the Arctic icepack retreats; the resulting open ocean provides a source for the ozone destroying halogens.  A side product of this reaction of particular concern is the conversion of mercury from a nonreactive to a toxic reactive form that precipitates into the terrestrial and ocean systems; ozone measurements are thus important as an indicator of mercury chemistry. Surface ozone measurements are made at five of the IASOA observatories (Alert, Barrow, Pallas/Sodankylä, Summit and Tiksi).  Comparisons between Barrow and Tiksi relate the timing of the ozone depletion events to a combination of offshore and onshore air flows and the timing of the sea-ice retreat . Monthly averages of ozone at Barrow, Alert, Tiksi, and Summit hve been compared for 2011.  The maximum variability and lowest ozone occurs in Barrow in March-April; for Tiksi and Alert, the ozone depletion period is shifted forward into April-May.  Summit which is a non-coastal site has generally higher ozone values year round (40-60 ppb as opposed to 5-50 ppb) than the other three sites; this is an expected result as Summit is the farthest removed from local open water bromine sources.