Carbonyl sulfide in air extracted from a South Pole ice core: a 2000 year record

Abstract

Abstract. In this study, we present carbonyl sulfide (COS) measurements from an ice core drilled near South Pole, East Antarctica (SPRESSO). The samples are from 135–291 m, with estimated mean COS ages ranging from 278 to 2155 years before present (defined as 2000 C.E.). When combined with the previous records of COS from Antarctic ice cores and firn air, the current data provide a continuous record of COS extending beyond the last two millennia. The general agreement between ice cores, firn air, and modern air measurements supports the idea that polar ice is a valid archive for paleoatmospheric COS. The average COS mixing ratio of the SPRESSO data set is (331±18) ppt (parts per trillion in mol/mol, ±1σ, n=100), excluding 6 outliers. These data confirm earlier firn air and ice core measurements indicating that the late 20th century COS levels of 500 ppt are greatly increased over preindustrial levels and represent the highest atmospheric levels over the past 2000 years. The data also provide evidence of climate-related variability on centennial time-scales, with relative maxima at the peaks of Medieval Climate Anomaly and Little Ice Age. There is evidence for a long-term increasing trend in COS of 1.8 ppt per 100 years. Further ice core studies will be needed to determine whether this trend reflects secular variability in atmospheric COS, or a slow post-depositional chemical loss of COS in the ice core.

Carbonyl sulfide hydrolysis in Antarctic ice cores and an atmospheric history for the last 8000 years

“…Air is extracted from the bubbles in 400-600 g ice core samples in a dry extraction system that involves mechanical shredding at À50°C under vacuum [Aydin et al, 2007[Aydin et al, , 2008. Four different extraction chambers were used in this study.…”

“…South Pole: The South Pole Remote Earth Science and Seismological Observatory (SPRESSO) ice core from the South Pole was dry drilled to a depth of 291 m in 2001-2002. We measured COS in a total of 106 samples, including 6 outliers [Aydin et al, 2008]. The measurements from the SPRESSO ice core are presented with the previously published COS chronology derived from ice ages based on visual stratigraphy and a constant delta age of 1028 years based on firn modeling [Aydin et al, 2008].…”

“…Firn air studies showed that there had been large increases in atmospheric COS during the early part of the twentieth century, constraining the anthropogenic component in the present-day budget to about 30% of the total sources [Sturges et al, 2001;Montzka, 2004]. Previous measurements in dry-drilled, shallow Antarctic ice cores from Siple Dome and South Pole showed that preindustrial COS mixing ratios ranged from 300 to 400 ppt over the last two millennia [Aydin et al, 2008].…”

Observations of the uptake of carbonyl sulfide (COS) by trees under elevated atmospheric carbon dioxide concentrations

“…This estimate is highly dependent on the potential increase of anthropogenic sources. Such an increase is discussed based on reports by Montzka et al (2004) and Aydin et al (2008) indicating that present COS levels of 500 ppt are greatly increased over preindustrial levels with a drastic increase of 200 ppt in 19th and 20th centuries. With regard to such a steep increase which resembles that of the CO 2 record, the potential decrease by the acclimation of the metabolic background of COS uptake could be expected to be balanced by a higher uptake rates due to higher substrate availability.…”

Post-coring entrapment of modern air in some shallow ice cores collected near the firn-ice transition: evidence from CFC-12 measurements in Antarctic firn air and ice cores

“…The WAIS-D and SPRESSO samples were extracted and analyzed using an updated procedure described in detail by Aydin et al (2007). These techniques were previously used to measure CH 3 Cl, CH 3 Br, and COS Aydin et al, 2008;Saltzman et al, 2008) and were applied unchanged during the analysis of WAIS-D and SPRESSO samples. Since the validity of our results hinges on the integrity of our methodology, we present a summary in the rest of this section.…”