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

Abstract

Abstract. Measurements of the complete isotopic composition of atmospheric CO ( 13 CO, 14 CO, C 17 O, C 18 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.

Carbon monoxide isotopic measurements in Indianapolis constrain urban source isotopic signatures and support mobile fossil fuel emissions as the dominant wintertime CO source

“…Novelli et al, 1998), CO mole fraction is strongly influenced by seasonal changes in OH, with CO increasing during the fall to a maximum in mid-winter, and decreasing to a minimum during the late summer (Figure 2) (Figure 2). Again, this result is similar to the Mount Sonnblick study (Gros et al, 2001) and differs from the high latitude background site (Rockmann et al, 2002). However, compared to the high latitude site (Rockmann et al, 2002), and the Mount Sonnblick site (Gros et al, 2001), the amplitude of the seasonal cycles in our study are muted.…”

“…Again, this result is similar to the Mount Sonnblick study (Gros et al, 2001) and differs from the high latitude background site (Rockmann et al, 2002). However, compared to the high latitude site (Rockmann et al, 2002), and the Mount Sonnblick site (Gros et al, 2001), the amplitude of the seasonal cycles in our study are muted. The difference between Indianapolis and these other sites is expected.…”

“…This result is similar to those found at another midlatitude continental site, Mount Sonnblick in the Austrian Alps (47°N, 3106 m above sea level) (Gros et al, 2001). This pattern deviates from a typical high latitude background site, where d 13 CO tends to lag behind both CO mole-fraction and dC 18 O (Rockmann et al, 2002). Our results show significant scatter in CO mole fraction and dC…”

“…The difference between Indianapolis and these other sites is expected. At high latitude sites such as Spitsbergen (79°N) and Alert (82°N) (Rockmann et al, 2002) the amplitude of the OH seasonal cycle is greater than Indianapolis' (39°N) and will drive stronger variations in CO mole fraction, d…”

Uncertainties of fluxes and <sup>13</sup>C ∕ <sup>12</sup>C ratios of atmospheric reactive-gas emissions

“…This is too rough an approximation, considering the intensive chemistry in the summer and characteristic CO lifetime that is shorter than a month. Indeed, the isotopic composition of background CO undergoes significant changes from spring to autumn, and the competition of the CO + OH reaction KIE and the varying in situ contribution from methane are the two non-negligible effects (Brenninkmeijer, 1993;Manning et al, 1997;Röckmann et al, 2002;Gromov et al, 2010). Besides the temporal variation, the global average value does not represent the variable spatial distribution of the biogenic sources, which is important, since biogenic CO is mainly a product of the rapid oxidation of NMHCs.…”