ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-2-147-2002 Using <sup>14</sup>C, <sup>13</sup>C, <sup>18</sup>O and <sup>17</sup>O isotopic variations to provide insights into the high northern latitude surface CO inventory Röckmann T. 1 2 Jöckel P. 2 Gros V. 2 Bräunlich M. 2 Possnert G. 3 Brenninkmeijer C. A. M. 2 Max-Planck-Institut für Kernphysik, Bereich Atmosphärenphysik, Heidelberg, Germany Max-Planck-Institut für Chemie, Abteilung Luftchemie, Mainz, Germany Uppsala University, Angdtrömlaboratoriet, Uppsala, Sweden 24 06 2002 2 2 147 159 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/2/147/2002/acp-2-147-2002.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/2/147/2002/acp-2-147-2002.pdf

Measurements of the complete isotopic composition of atmospheric CO (<sup>3</sup>CO, <sup>14</sup>CO, C<sup>17</sup>O, C<sup>18</sup>O) have been carried out at the high northern latitude stations Spitsbergen, Norway, and Alert, Canada. The annual changes of the isotope signatures reflect the seasonally varying contributions from the individual CO sources and the OH sink. Short-term variability is small at the remote sampling locations. Nevertheless, the interannual variability is considerable, in particular for the summer minimum. The most prominent event was a strong increase in CO in 1998 that persisted for several months. Using the isotope signatures it is possible to clearly identify extraordinarily strong biomass burning during that season as the cause for this large-scale CO anomaly. In 1997, on the other hand, biomass burning emissions were very low, leading to an unusually low summer minimum and corresponding isotope signatures. The results underscore that monitoring of CO and its isotopic composition at remote high latitude stations is a valuable tool to better understand long-term variations of CO that are representative for the whole high northern latitude region.