On the Identification of The Downward Propagation of Arctic Stratospheric Temperature Changes over Recent Decades

Arctic ozone loss is very variable due to its strong dependence on lower stratospheric temperatures, which are highly variable from year to year. Rex et al. (2006) suggested that there was a trend in the five-year maximum volume of polar stratospheric clouds over the past 40 years; thus, there has been a suggestion that the extreme Arctic winters are becoming even more severe. Kuttippurath and Nikulin (2012) described an inverse relationship between the chemical ozone loss in the Arctic and the intensity and timing of major warmings in the stratosphere; as the occurrence of a major sudden stratospheric warming, resulting in either a displacement or splitting of the vortex, results in a weaker polar vortex once it reforms.

In this study, we examine temperatures and ozone changes in the lower stratosphere comparing periods when the Arctic was dynamically quiescent and did not experience major sudden warmings. We find that spring season temperatures in the Arctic lower stratosphere for recent years without major sudden warmings are cooler than they were prior to the 1990s. Furthermore, this change can be related to changes in temperature earlier in the season and to the Northern Annular Mode Index at 10 hPa. The decadal-scale relationships between the upper stratosphere in February and lower stratosphere in March are consistent with the downward phase propagation during strong vortex events in single winters, as described by Baldwin and Dunkerton (2001). Conversely, the temperature changes for Arctic winters with major sudden warmings are much weaker in February at 10 hPa and in March in the lower stratosphere. Thus the large variability due to the occurrence of major sudden warmings has confounded understanding Arctic stratospheric temperature changes due to the opposing relationships of years with major sudden warmings and those without major sudden warmings.

References

Baldwin, M. P., and T. J. Dunkerton (2001), Stratospheric Harbingers of Anomalous Weather Regimes, Science, 294, 581-584.

Kuttippurath, J., and G. Nikulin (2012), A comparative study of the major sudden stratospheric warmings in the Arctic winters 2003/2004-2009/2010, Atmos. Chem. Phys., 12, 8115-8129.

Rex, M., et al. (2006), Arctic winter 2005: Implications for stratospheric ozone loss and climate change, Geophys. Res. Lett., 33, L23808.