Temporary pause in the growth of atmospheric ethane and propane in 2015–2018

Abstract

Abstract. Atmospheric non-methane hydrocarbons (NMHCs) play an important role in the formation of secondary organic aerosols and ozone. After a multidecadal global decline in atmospheric mole fractions of ethane and propane – the most abundant atmospheric NMHCs – previous work has shown a reversal of this trend with increasing atmospheric abundances from 2009 to 2015 in the Northern Hemisphere. These concentration increases were attributed to the unprecedented growth in oil and natural gas (O&NG) production in North America. Here, we supplement this trend analysis building on the long-term (2008–2010; 2012–2020) high-resolution (∼3 h) record of ambient air C2–C7 NMHCs from in situ measurements at the Greenland Environmental Observatory at Summit station (GEOSummit, 72.58 ∘ N, 38.48 ∘ W; 3210 m above sea level). We confirm previous findings that the ethane mole fraction significantly increased by +69.0 [+47.4, +73.2; 95 % confidence interval] ppt yr−1 from January 2010 to December 2014. Subsequent measurements, however, reveal a significant decrease by −58.4 [−64.1, −48.9] ppt yr−1 from January 2015 to December 2018. A similar reversal is found for propane. The upturn observed after 2019 suggests, however, that the pause in the growth of atmospheric ethane and propane might only have been temporary. Discrete samples collected at other northern hemispheric baseline sites under the umbrella of the NOAA cooperative global air sampling network show a similar decrease in 2015–2018 and suggest a hemispheric pattern. Here, we further discuss the potential contribution of biomass burning and O&NG emissions (the main sources of ethane and propane) and conclude that O&NG activities likely played a role in these recent changes. This study highlights the crucial need for better constrained emission inventories.

Sources and Distribution of Light NMHCs in the Marine Boundary Layer of the Northern Indian Ocean During Winter: Implications to Aerosol Formation

“…Ethane has a longer atmospheric lifetime than other anthropogenic NMHCs, such as propane, butane, pentane, etc. due to its slower reaction rate with OH (Angot et al., 2021; Helmig et al., 2014). Therefore, the mixing ratio of ethane in remote regions can be used as an indicator of continental influences.…”

“…Ethane and propane are the most abundant NMHCs emitted from common sources such as industrial oil and gas production, processing, and transportation of natural gas (Angot et al., 2021). However, the lifetime of ethane is ∼5 times longer than propane due to different OH reaction rate constants of 0.89 × 10 −12 and 0.18 × 10 −12 cm 3 molecule −1 s −1 , respectively (Atkinson & Arey, 2003).…”

Year-round trace gas measurements in the central Arctic during the MOSAiC expedition

“…Monitoring GHG atmospheric abundances in the Arctic is, however, challenging because it is a remote and harsh environment with a sparsity of locations with appropriate infrastructure. As a consequence, observations have mostly been performed at ground-based coastal stations or during short-term aircraft or ship-based campaigns 16 . In that context, the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC; https://mosaic-expedition.org/ ) expedition offered an unprecedented opportunity to monitor the year-round atmospheric composition of the central Arctic.…”