Stable sulfur isotope ratios (d34S) in a West Antarctic firn core: Assessment of sulfate source and deposition
Abstract
Stable sulfur isotopes can be a useful tracer of atmospheric sulfate sources, if the isotopic signature of each source is distinct. In Antarctica, there are assumed to be only three possible sources of sulfate (marine biogenic activity, sea-salt, and volcanic eruptions), with the marine and volcanic contributions having d34S values of approximately 16-21% and 2-5%, respectively. Therefore, d 34S data may be useful for estimating the relative contribution of marine and volcanic sulfate both spatially across Antarctica, and temporally in firn and ice core records. Here we present d34S data from a firn core in West Antarctica (RIDSA, 78_44' S, 116_20' W, 1804 m) covering the years 1935-1976, including the 1963 Agung eruption. The d34S value from the section of core including the 1963 Agung period is 4%, consistent with a volcanic sulfur signature. The range of d34S data from core sections on either side of the Agung eruption is 3-10%, suggesting that the contribution of volcanic sulfate on the West Antarctic polar plateau was significant not only during the Agung eruption, but during other times as well. Our results from the Agung layer are consistent with published data from the Vostok core (East Antarctica; 8' S, 115' E, 2850m), where a d34S value of 2.7% was reported. However, Vostok data display a significant marine influence, with d34S values of 15% to 22% on either side of the Agung eruption. Possible explanations for the discrepancy between West Antarctic and East Antarctic d34S values include: 1) different spatial patterns of sulfate deposition related to upper tropospheric/lower stratospheric circulation, and 2) regional-scale influence of sub-Antarctic volcanic island chains. We will discuss these possibilities in the context of new samples collected during recent ITASE traverses.
- Publication:
-
AGU Spring Meeting Abstracts
- Pub Date:
- May 2002
- Bibcode:
- 2002AGUSM.A41A..08P
- Keywords:
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- 0305 Aerosols and particles (0345;
- 4801);
- 0910 Data processing;
- 1030 Geochemical cycles (0330)