09:45 〜 10:00
[ACC33-04] Perchlorate in Antarctic snow: A new index for Stratospheric ozone
キーワード：ozone, perchlorate, snow and ice, Antarctica
Stratospheric ozone can absorb ultraviolet radiation and consequently influences the radiation balance and the oxidation capacity of the earth’s atmosphere. Therefore, variability of stratospheric ozone can reflect changes in climate and environment. However, the history of stratospheric ozone variability, espeically before the 20th century, remains largely unknown, possibly due to the lack of ideal proxy of ozone. Natural perchlorate is widespread in the environment, which is mainly formed in the atmosphere through reactions between ozone and chlorine species. Therefore, natural perchlorate may contain information of ozone variability. However, perchlorate also has anthropogenic sources, and natural perchlorate in populated areas is always mixed with anthropogenic perchlorate. Our results show that perchlorte pollution from human activities and dust is confined to only local or regional environments. Thus perchlorate in polar regions is dominated by natural sources and polar snow provides one of the best records to investigate natural perchlorate.
Analysis of perchlorate concentrations in Antarctic snow shows that perchlorate concentrations are in the range of a few to a few hundred ng kg-1, which are generally one to two orders of magnitude higher than those in Arctic snow. There is an obvious seasonal cycle in perchlorate concentration, with highest values in the austral autumn and lowest in spring. The similar timing of the perchlorate minimum with total column ozone minimum suggests that during spring, perchlorate production over the Antarctic is dependent on stratospheric ozone. In spring when Antarctic ozone hole occurs, a large amount of perchlorate may be formed through reactions between reactive chlorine and ozone which also cause the significant depletion of stratospheric ozone over Antarctica. It would take several months for the stratospheric perchlorate to deposit on the surface snow. Thus, the maximum concentration in autumn may be associated with stratospheric perchlorate formed during spring. Due to the significantly lower frequency and extent of the ozone hole in the Arctic compared to the Antarctica, perchlorate production is considerably reduced, leading to much lower concentrations in the Arctic than in the Antarctica. All these facts suggest that perchlorate is an index of stratospheric ozone.
Analysis of perchlorate concentrations in Antarctic snow shows that perchlorate concentrations are in the range of a few to a few hundred ng kg-1, which are generally one to two orders of magnitude higher than those in Arctic snow. There is an obvious seasonal cycle in perchlorate concentration, with highest values in the austral autumn and lowest in spring. The similar timing of the perchlorate minimum with total column ozone minimum suggests that during spring, perchlorate production over the Antarctic is dependent on stratospheric ozone. In spring when Antarctic ozone hole occurs, a large amount of perchlorate may be formed through reactions between reactive chlorine and ozone which also cause the significant depletion of stratospheric ozone over Antarctica. It would take several months for the stratospheric perchlorate to deposit on the surface snow. Thus, the maximum concentration in autumn may be associated with stratospheric perchlorate formed during spring. Due to the significantly lower frequency and extent of the ozone hole in the Arctic compared to the Antarctica, perchlorate production is considerably reduced, leading to much lower concentrations in the Arctic than in the Antarctica. All these facts suggest that perchlorate is an index of stratospheric ozone.