The isotopic record of Northern Hemisphere atmospheric carbon monoxide since 1950, implications for the CO budget

Abstract

We present a 60-yr record of atmospheric CO concentration and stable isotopic ratios at high northern latitude based on firn air samples collected in the frame of the North Greenland Eemian Ice Drilling (NEEM) project. Concentration, δ<sup>13</sup>C, and δ<sup>18</sup>O of CO from trapped gases in the firn were measured by gas chromatography coupled with isotope ratio mass spectrometry (gc-IRMS). Using models of trace gas transport in firn, the long-term trend of atmospheric CO and its stable isotopic composition at high northern latitudes since the 1950s were reconstructed. Our best firn air scenarios suggest that δ<sup>13</sup>C decreased slightly from −25.8‰ in 1950 to −26.4‰ in 2000, then dropped to −27.2‰ in 2008. δ<sup>18</sup>O decreased more regularly from 9.8‰ in 1950 to 7.1‰ in 2008. The best firn air scenarios also suggest that CO concentration increased gradually from 1950 and peaked likely in the late-1970s, followed by a gradual decrease by present day (Petrenko et al., 2011). An isotope mass balance model is applied to quantify the temporal evolution of CO source partitioning able to explain the combined mixing ratio and isotopic ratio changes. It suggests that a slight increase followed by a large reduction in CO derived from fossil fuel combustion occurred since 1950. The increase of CO concentration from 1950 to the mid-1970s is the result of a combined increase of multiple sources. The reduction of CO emission from fossil fuel combustion after the mid-1970s is the most plausible mechanism for the drop of CO concentration during this time. The mitigation policy for CO emission from vehicle exhaust such as application of catalytic converters and the growth of diesel engine vehicles market share are the main expected reasons for the CO source strength change from fossil fuel combustion

Relative changes in CO emissions over megacities based on observations from space

“…Paris shows a reduction in CO total column compared to 2000–2003 (−22%), while Delhi presents a large increase (+22.4%) (Table ). Over Europe as a whole, this decrease began with the invention (in 1975) and mandatory application (in 1993) of catalytic converters and the growth of diesel engine vehicle market share [ Wang et al ., ]. There may also be some connection to the 2008 economic crisis as explained by Castellanos and Boersma [], who observed a modification of the regional NO x concentrations due to changes in the economy in Europe, even if this crisis overlaps only the last year of our studied period.…”

Variation of atmospheric CO, δ 13 C, and δ 18 O at high northern latitude during 2004–2009: Observations and model simulations

“…The net emission of CO to the atmosphere is the summed contribution from all distinct sources, including anthropogenic, biomass burning, biogenic, and ocean. We know that, in the past, variations in the relative amounts of these sources have changed over time, in both the short term—seasonal to interannual—[ Novelli et al ., ; Park and Rhee , ; Park et al ., ] and the long term—multidecadal to centennial [ Wang et al ., , ]. Briefly, Novelli et al .…”

“…[] reported that CO varied from 38 to 55 ppbv mainly due to the change in biomass burning CO. Also, Wang et al . [] found from the analysis of the past 60 year record of CO from the Greenland firn air samples that CO varied from 90 to 160 ppbv and that the fossil fuel source is the primary contribution to the observed CO.…”

“…Observation sites located in the high‐latitude Northern Hemisphere (e.g., Barrow, Alaska, and Alert, Canada) are largely affected by the polluted air masses from the middle latitudes such as North America, Europe, and North Asia. An increase of CO at high northern latitudes over the past 200 years has been observed from Greenland ice cores [ Haan et al ., ], and a more recent significant decadal variation of CO since 1950 has been reconstructed from Greenland firn air measurements [ Wang et al ., ]. Both of these papers indicate long‐term variations in atmospheric CO. Because of the deduced stability of global atmospheric hydroxyl radical over the past few decades [ Montzka et al ., ], which is the most important variable in determining the removal rate of atmospheric CO, it is likely that changes in the source strengths of CO are the most important causal factor behind interannual variations of CO.…”

An Avoidable Tragedy at the Sea Cliff (Rincon) Oil Field

“…The d 13 C ratio of carbon monoxide in Well C-l0A (Table 3) falls in a narrow range from ¡41.19% to ¡43.29%. The d 13 C range in the atmosphere in the year 2000, is approximately in the range ¡31% to ¡22% (Wang et al, 2002). No CO was detected in the other two wells.…”