USAP-DC

This award supports the analysis, in Antarctic ice cores, of the ozone depleting substances methyl bromide (CH3Br) and methyl chloride (CH3Cl), and the sulfur-containing gas, carbonyl sulfide (OCS). The broad scientific goal is to assess the level and variability of these gases in the preindustrial atmosphere. This information will allow testing of current models for sources and sinks of these gases from the atmosphere, and to indirectly assess the impact of anthropogenic activities on their biogeochemical cycles. Longer-term records will shed light on the climatic sensitivity of the atmospheric burden of these gases, and ultimately on the biogeochemical processes controlling them. These gases are present in ice at parts per trillion levels, and the current database consists entirely of a small number of measurements made in from a shallow ice core from Siple Dome, Antarctica. This project will involve studies of ice core samples from three Antarctic sites: Siple Station, Siple Dome, and South Pole. The sampling strategy is designed to accomplish several objectives: 1) to verify the atmospheric mixing ratios previously observed in shallow Siple Dome ice for OCS, CH3Br, and CH3Cl at sites with very different accumulation rates and surface temperatures; 2) to obtain a well-dated, high resolution record from a high accumulation rate site (Siple Station), that can provide overlap in mean gas age with Antarctic firn air samples; 3) explore Holocene variability in trace gas mixing ratios; and 4) to make the first measurements of these trace gases in Antarctic glacial ice. In terms of broader impact on society, this research will help to provide a stronger scientific basis for policy decisions regulating the production and use of ozone-depleting and climate-active gases. Specifically, the methyl bromide results will contribute to the current debate on the impact of recent regulation (via the Montreal Protocol and its Amendments) on atmospheric levels. Determination of pre-industrial atmospheric variability of ozone-depleting substances will help place more realistic constraints on scenarios used for future projections of stratospheric ozone and its climatic impacts. This research will involve the participation of both graduate and undergraduate students.

Person	Role
Saltzman, Eric	Investigator
Aydin, Murat	Co-Investigator
Williams, Margaret	Co-Investigator
Tatum, Cheryl	Co-Investigator

Antarctic Glaciology

Award # 0338359

NSIDC-0313_1
NSIDC-0279_1
NSIDC-0131_1

None in the Database

Repository	Title (link)	Format(s)	Status
USAP-DC	Ice Core Air Carbonyl Sulfide Measurements - SPRESSO Ice Core	None	exists
USAP-DC	Methane and Carbonyl Sulfide Analysis of Siple Dome Ice Core Subsamples	None	exist
USAP-DC	Analysis of Siple Dome Ice Core: Carbonyl Sulfide (COS), Methyl Chloride (CH3Cl), and Methyl Bromide (CH3Br)	None	exist
USAP-DC	Antarctic Ice Cores: Methyl Chloride and Methyl Bromide	None	exist