Open Access2,000‐year record of atmospheric methyl bromide from a South Pole ice core
Author(s) -
Saltzman Eric S.,
Aydin Murat,
Tatum Cheryl,
Williams Margaret B.
Publication year - 2008
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2007jd008919
Subject(s) - ice core , firn , atmospheric sciences , southern hemisphere , climatology , geology , atmosphere (unit) , air mass (solar energy) , environmental science , snow , meteorology , geography , geomorphology , physics , boundary layer , thermodynamics
This study reports measurements of methyl bromide (CH 3 Br) in air bubbles from a South Pole ice core, with gas ages covering the past two millennia. The air was extracted by mechanical shredding of the core under vacuum and the evolved gases were analyzed by gas chromatography with high resolution mass spectrometry and isotope dilution. These samples had estimated mean gas ages ranging from 160 BCE to 1860 CE. The mean CH 3 Br mixing ratio in the ice core samples was 5.39 ±.06 ppt (1s.e., n = 113). The CH 3 Br measurements from this core agree with those from a Siple Dome ice core for mean gas ages between 1671 and 1860 CE, where there is overlap between the cores. The data show no linear trend over the 2000 year period prior to industrialization. Together, Antarctic ice core and firn air measurements clearly demonstrate that the increase in atmospheric CH 3 Br during the twentieth century exceeds natural variability during the past 2000 years. There is evidence of centennial‐scale variability in CH 3 Br on the order of ±10–20% that may indicate a natural climate sensitivity of the atmospheric levels of this ozone depleting substance. The analysis of CH 3 Br in additional Antarctic ice cores will be needed to confirm that the centennial‐scale variability observed in this core represents a southern hemisphere atmospheric history.