Becky Alexander


The West Antarctic Ice Sheet (WAIS) Divide ice core recently (January 1, 2012) reached its final depth of 3,405 meters (ice at the bottom is 62,000 years old). So far, our group has been funded to measure the isotopic composition of nitrate and sulfate from ice as far back as 2,400 years before present. The oxygen isotopic composition of nitrate and sulfate can be used to infer their production pathways in the past, and hence information about the chemistry of the troposphere. For this first phase, we are focusing on anthropogenic (human) impacts on atmospheric chemistry and the oxidative capacity of the atmosphere.

The figure below shows our measurements of δ15N and Δ17O of nitrate, and Δ17O of sulfate from the WAIS Divide ice core over the past 2,400 years. Interpretation of this data is in progress – stay tuned!

WAIS Divide Data


  • Eric Steig (lead P.I.), Becky Alexander (co-P.I.), Andrew Schauer (IsoLab manager), Shelley Kunasek (former graduate student), and Eric Sofen (graduate student) (UW)
  • Mark H. Thiemens (co-P.I.) (UCSD)


NSF-ANT 0538049

Publications so far

Kunasek, S.A., B. Alexander, E.J. Steig, E.D. Sofen, T.L. Jackson, M.H. Thiemens, J.R. McConnel, D.J. Gleason, H.M. Amos, Sulfate sources and oxidation chemistry over the past ~230 years from sulfur and oxygen isotopes of sulfate in a West Antarctic ice core, J. Geophys. Res., 115, D18313, doi:10.1029/2010JD013846 (2010). Highlighted in Eos Vol. 91, No. 49, 7 December 2010 “Research Spotlight”