Carbonyl sulfide in air extracted from a South Pole ice core: a 2000 year record M. Aydin1, M. B. Williams1,*, C. Tatum1,**, and E. S. Saltzman1 1Department of Earth System Science, University of California, Irvine, California, USA *now at: NASA Ames Research Center, Moffett Field, California, USA **now at: University of Miami, Florida, USA
Abstract. In this study, we present carbonyl sulfide (COS) measurements from an ice
core drilled near South Pole, East Antarctica (SPRESSO). The samples are
from 135–291 m, with estimated mean COS ages ranging from 278 to 2155 years
before present (defined as 2000 C.E.). When combined with the previous
records of COS from Antarctic ice cores and firn air, the current data
provide a continuous record of COS extending beyond the last two millennia.
The general agreement between ice cores, firn air, and modern air
measurements supports the idea that polar ice is a valid archive for
paleoatmospheric COS. The average COS mixing ratio of the SPRESSO data set
is (331±18) ppt (parts per trillion in mol/mol, ±1σ,
n=100), excluding 6 outliers. These data confirm earlier firn air and ice
core measurements indicating that the late 20th century COS levels of
500 ppt are greatly increased over preindustrial levels and represent the
highest atmospheric levels over the past 2000 years. The data also provide
evidence of climate-related variability on centennial time-scales, with
relative maxima at the peaks of Medieval Climate Anomaly and Little Ice Age.
There is evidence for a long-term increasing trend in COS of 1.8 ppt per 100
years. Further ice core studies will be needed to determine whether this
trend reflects secular variability in atmospheric COS, or a slow
post-depositional chemical loss of COS in the ice core.
Citation: Aydin, M., Williams, M. B., Tatum, C., and Saltzman, E. S.: Carbonyl sulfide in air extracted from a South Pole ice core: a 2000 year record, Atmos. Chem. Phys., 8, 7533-7542, doi:10.5194/acp-8-7533-2008, 2008.