Trend and recovery of the total ozone column in South America and Antarctica

Abstract

South America is one of the most vulnerable areas to stratospheric ozone depletion; consequently, an increased amount of UV radiation reaches the Earth's surface in this region. In this study, we analyzed the long-term trend in the total ozone column (TOC) over the southern part of the South American continent from 1980 to 2009. The database used was obtained by combining several satellite measurements of the TOC on a 1A degrees (latitude) x 1.25A degrees (longitude) grid. Analysis of the long-term trend was performed by applying the Theil-Sen estimator and the Mann-Kendall significance test to the deseasonalized time series. The long-term trend was also analyzed over several highly populated urban zones in the study area. Finally, multiple linear regression (MLR) modeling was used to identify and quantify the drivers of interannual variability in the TOC over the study area with a pixel-by-pixel approach. The results showed a decrease in the TOC ranging from -0.3 to -4% dec(-1) from 1980 to 2009. On a decadal timescale, there is significant variability in this trend, and a decrease of more than -10% dec(-1) was found at high latitudes (1980-1989). However, the trends obtained over much of the study area were not statistically significant. Considering the period from 1980 to 1995, we found a decrease in the TOC of -2.0 +/- 0.6% dec(-1) at latitudes below 40A degrees S and -6.9 +/- 2.0% dec(-1) at latitudes above 40A degrees S, for a 99.9% confidence level over most of the study area. Analysis of the period from 1996 to 2009 showed a statistically significant increase of 2.3 +/- 0.1% dec(-1) at high latitudes (> 60A degrees S), confirming the initial TOC recovery in the Antarctic. Despite evidence for initial recovery of the TOC in some parts of the study area between 1996 and 2009, the long-term increase from September to November is not yet statistically significant. In addition, large parts of the study area and most of the urban areas continue to show a decreasing trend in the TOC. The MLR results show that at high latitudes, the main driver of interannual variability in the TOC is the total effective amount of halogens, followed by the eddy heat flux.