Gas consortium

Names and contact details for chairs

Thomas Blunier (blunier@nbi.ku.dk)
Ed Brook (brooke@geo.oregonstate.edu)

Point of contact and procedure for joining the consortium mailing list

Please go to https://mailman.nbi.ku.dk/listinfo to sign up for the NEEM-gas mailing list. The list is managed by the consortium chairs.

A brief description of the work of the consortium.

What is the gas consortium about?
About 10% of the volume of an ice core consists of air of atmospheric origin. The air is enclosed at the bottom of an open porous zone of about 70m at NEEM. This so called firn contains the air back to the early 20th century. We study both firn air and air enclosed in bubbles in the ice for the composition of the past atmosphere.

The firn can provide very large amounts of air, allowing very precise measurements of concentrations as well as the isotopic composition of the gases such as methane (CH₄), nitrous oxide (N₂O), carbon dioxide (CO₂), carbon monoxide (CO), hydrogen (H₂). Further, more exotic components of the atmosphere like methyl halides (CH₃Cl, CH₃Br and CH₃I) and C1/C2 alkyl nitrates will be measured. The hope is that NEEM will provide an improved record of these species, a longer time history of all gases without any chemical perturbation. These measurements can tell us much about changes in the processes that produce and remove these gases to and from the atmosphere over the last several decades, and therefore help us understand how human and natural processes influence the chemistry of the atmosphere and the greenhouse effect.

In the ice below the firn, where air is trapped in the ice, only limited amounts of air are available from the deep drill, making measurements more challenging. Sharing of the samples efficiently between different collaborating institutes and for different purposes becomes very important and is one of the main tasks of the consortium. The majority of the planned measurements fall in three areas. First, a major effort will be made to reconstruct the concentration and isotope composition of CH₄ and N₂O, to better understand what controls their variability over the last ~ 160,000 years. An attempt will also be made to reconstruct the CO₂ concentration and its isotopic composition. So far reliable CO₂ measurements have been restricted to Antarctic ice cores, but a record from Greenland would allow important comparisons between climate change in Greenland and carbon dioxide. Second, several groups will use measurements of more abundant gases (N₂, O₂, Ar, Kr, Xe) to reconstruct temperature change, learn about physical processes controlling the gas record, and the global oxygen cycle. Third, within NEEM the possibility for new components like H₂ and CO will be explored. Both are important components of the atmospheric chemistry system.
Methyl halides (CH₃Cl, CH₃Br and CH₃I) and, carbonyl sulfide (COS) will be measured. These gases have varied natural sources, notably in the tropics, including emissions from marine organisms and terrestrial vegetation.

Work of the consortium
Coordinate the distribution of gas samples between laboratories for the various components.
Coordinate field work for firn gas sampling.
Contact point for sample requests concerning gas samples.
Circulate data at an early stage within the community.
Coordinate publications within the gas consortium.

See consortia minutes, reports and data (restricted access)