C046-0007
Ice Core Carbonyl Sulfide Record over the Last 52,000 Years from the SPC14 Ice Core (SPICEcore)

Monday, 14 December 2020
Poster
Murat Aydin1, Melinda Renee Nicewonger2,3, Erich C Osterberg4, Karl J Kreutz5, Dominic Winski5, David G Ferris Mr.4, Jihong Cole-Dai6, Zayta Renay Thundercloud4, Eric S Saltzman1 and Armando Byron Vilchez7, (1)University of California Irvine, Irvine, CA, United States, (2)NOAA/ESRL Global Monitoring Laboratory, Boulder, CO, United States, (3)University of California, Irvine, Irvine, CA, United States, (4)Dartmouth College, Department of Earth Sciences, Hanover, NH, United States, (5)University of Maine, School of Earth and Climate Sciences, Orono, ME, United States, (6)South Dakota State University, Department of Chemistry and Biochemistry, Brookings, SD, United States, (7)University of California Irvine, Department of Earth System Science, Irvine, United States
Abstract:
Carbonyl sulfide (COS) is the most abundant sulfur gas in the troposphere and contributes to stratospheric sulfate aerosols. The present-day atmospheric mixing ratio is about 500 ppt. The largest sources of COS are direct and indirect (as CS2 and DMS) emissions from the world ocean. Anthropogenic COS and CS2 emissions are the second most important source of atmospheric COS today, accounting for about 30% of the atmospheric burden. The primary removal mechanism is uptake by terrestrial plants during photosynthesis. Because plants do not respire COS, atmospheric COS levels are directly linked to terrestrial gross primary productivity (GPP).

We measured COS in 574 samples spanning the length of the SPC14 ice core drilled at South Pole, Antarctica as part of the SPICEcore project. Ice core air was extracted using two different methods: 425 samples with dry extraction (by shredding ice) and 149 samples with wet extraction (by melting ice). Dry extraction does not yield good data from the bubble-clathrate transition, which coincides with the 20 to 9 ky (thousand years before 1950 CE) period in the SPC14 ice core. The wet extraction measurements require a solubility correction due to the high solubility of COS in sample melt water. We calculate the required solubility correction using overlapping dry and wet extraction data from the Holocene and construct a continuous COS record spanning the 52 to 0.1 ky period. After correction for gravitational enrichment in the firn, the mean COS mixing ratio measured during the Holocene (11.5 to 0.1 ky) is 313±17 ppt (±1s), ranging from 271 ppt to 416 ppt. The Holocene record is characterized by a minimum of about 290 ppt around 8 ky and a maximum of about 330 ppt near 1 ky. The measurements from the 16 to 12 ky period are among the lowest in the entire data set averaging about 270 ppt. The period from 52 to 17 ky is characterized by much higher variance (sample-to-sample variability) relative to measurements from younger periods, averaging 310±46 ppt (±1s) with a range of 243 ppt to 524 ppt. Measurements of major ions from the SPC14 ice core are used to investigate whether the high variance in the glacial COS data is linked to higher impurity levels in glacial ice. We find that high COS variance cannot be explained by changes in ice impurity levels. Atmospheric and biogeochemical implications will be discussed.

<< Previous Abstract | Next Abstract >>