Records of Northern Hemisphere Atmospheric Carbon Monoxide Back to ~1950 AD from Greenland Firn Air
V.V. Petrenko1, P. Martinerie2, P. Novelli3, D.M. Etheridge4, I. Levin5, Z. Wang6, T. Blunier7, J. Chappellaz2, J. Kaiser8, P. Lang3, L.P. Steele4, F. Vogel5, M.A. Leist4, J. Mak6, R.L. Langenfelds4, J. Schwander9, J.P. Severinghaus10, G. Forster8, W. Sturges8, G. Petron3, M. Rubino4 and J.W.C. White1
1Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309; 303-492-7132, E-mail: vasilii.petrenko@colorado.edu
2Laboratoire de Glaciologie et Géophysique de lEnvironement, University of Grenoble, Grenoble, France
3NOAA Earth System Research Laboratory, Boulder, CO 80305
4Centre for Australian Weather and Climate Research, Aspendale, Victoria, Australia
5Institut für Umweltphysik, University of Heidelberg, Heidelberg D-69120, Germany
6School of Marine and Atmospheric Sciences / Institute for Terrestrial and Planetary Atmospheres, State University of New York at Stony Brook, Stony Brook, NY 11794
7Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, København DK-2100, Denmark
8School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ, England
9University of Berne, Physics Institute, Bern CH-3012, Switzerland
10Scripps Institution of Oceanography, University of California at San Diego, La Jolla, CA 92093
Carbon monoxide (CO) plays a key role in global atmospheric chemistry by being the main sink of atmospheric hydroxyl radicals (OH). Records of past [CO] from both hemispheres are essential for understanding past changes in atmospheric [OH] because the atmospheric lifetime of CO is less than the interhemispheric mixing time. Earlier attempts at reconstruction of northern hemisphere (NH) [CO] suffered from apparent in situ CO production in ice and firn. We present a record of high-latitude NH [CO] to ~1950 AD, from measurements by four different laboratories of firn air collected from three different boreholes at the North EEMian (NEEM) ice core site in Greenland. Procedural blanks indicate no detectable [CO] contamination from sampling. Excellent agreement with a firn air record from another cold Greenland site North Greenland Ice Core Project is consistent with the NEEM firn CO record being unaltered. A preliminary analysis of our measurements, interpreted using two different firn air diffusion models, suggests that high-latitude NH [CO]: 1) was ~150 ppb in the year 1950, 2) increased from 1950 to the 1970s, 3) peaked above 160 ppb in the 1970s and 4) gradually declined after the 1970s. Work is in progress to finalize the [CO] reconstruction and interpret the record in the context of historical CO emissions estimates as well as changes in other relevant trace atmospheric constituents.
Figure 1. Depth – mixing ratio data for CO from the NEEM 2008 firn air campaign. H2, CO2 and CH4 depth profiles are also shown for reference.