|Title:||Ice-core Records of Atmospheric Halogen Concentrations over Western Antarctica - Past and Present|
|Author:||Maselli, O., McConnell, J.R., Sigl, M., Layman, L., Pasteris, D., Das, S.B. and Chriscitiello, A.S.|
|Periodical:||American Geophysical Union, Fall Meeting 2012, abstract #A51E-0103|
High temporal resolution halogen records from Western Antarctica will be presented which cover the transition from present day into the Pleistocene epoch (25,000 years B.P.). The WAIS Divide Ice Core (79°28' S, 112°05' W) was analysed for Chlorine, Bromine and Iodine at annual resolution (up to ~16,000 years B.P.) using a continuous melt system coupled with parallel mass spectrometers (ICP-MS) – a technique developed at the Desert Research Institute in Reno, Nevada. The ICP-MS technique measures both the soluble species and insoluble particulate species that have been trapped in the ice. The high resolution, continuous record allows us to observe the annual concentration cycles of halogens trapped in the ice and compare the seasonal timings of the signals from 16,000 years ago to present. Seasonal cycles observed in an array of shallow ice cores in south western Antarctica give insight into the present day spatial distribution of the halogen species. The results from the ice cores are compared to satellite imaging that shows the daylight distributions of halogen oxides over the entire Antarctic continent. Dramatic changes in absolute Iodine concentrations are observed through the transition from the glacial to interglacial period whilst average bromine concentrations remain relatively unchanged. This observation supports a source or sink of the iodine which is independent of bromine. The temporal variability of all halogen concentrations observed in the ice on a decadal scale appears to be closely linked to the regional temperature proxy (δ18O of water) which may be a reflection of changes in deposition mechanisms as well as of sources or sinks.