A 2000 year atmospheric history of methyl chloride from a South Pole ice core: Evidence for climate-controlled variability
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چکیده
[1] Methyl chloride (CH3Cl) is a naturally occurring ozone-depleting gas with a complex biogeochemical cycle involving tropical vegetation, soils, biomass burning and the oceans. This study presents CH3Cl measurements in air extracted from a 300 m ice core from South Pole, Antarctica, covering the time period from 160 BC to 1860 AD. The data exhibit an increasing trend of 3 ppt (parts per trillion) over 100 years and higher frequency variations that appear to be climate-related. CH3Cl levels were elevated from 900–1300 AD by about 50 ppt relative to the previous 1000 years, coincident with the warm Medieval Climate Anomaly (MCA). CH3Cl levels decreased to a minimum during the Little Ice Age cooling (1650–1800 AD), before rising again to the modern atmospheric level of 550 ppt. These variations most likely reflect changes in tropical and subtropical conditions, and raise the possibility that a warmer future climate may result in higher tropospheric CH3Cl levels. Citation: Williams, M. B., M. Aydin, C. Tatum, and E. S. Saltzman (2007), A 2000 year atmospheric history of methyl chloride from a South Pole ice core: Evidence for climatecontrolled variability, Geophys. Res. Lett., 34, L07811, doi:10.1029/2006GL029142.
منابع مشابه
Atmospheric variability of methyl chloride during the last 300 years from an Antarctic ice core and firn air
[1] Measurements of methyl chloride (CH3Cl) in Antarctic polar ice and firn air are used to describe the variability of atmospheric CH3Cl during the past 300 years. Firn air results from South Pole and Siple Dome suggest that the atmospheric abundance of CH3Cl increased by about 10% in the 50 years prior to 1990. Ice core measurements from Siple Dome provide evidence for a cyclic natural variab...
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