Summary: Climate driven changes in the oxidation pathways of
N. I. Barkov,2
R. J. Delmas,3
and M. H. Thiemens1
Received 7 February 2002; revised 8 April 2002; accepted 11 April 2002; published 24 July 2002.
 Ice cores have provided a wealth of information about
past atmospheric composition and climate variability.
However, relatively little is known about how the
chemistry of the atmosphere has responded to natural
climate change and anthropogenic influences. The oxygen
O and d18
O) of sulfate serve as a recorder of the
relative amounts of gas and aqueous-phase oxidation
pathways in the atmosphere. This quality, along with its
stability, renders sulfate an ideal proxy to investigate
changes in oxidation pathways of S(IV) species in present