Open AccessStable carbon isotope ratios of ethane over the North Pacific: Atmospheric measurements and global chemical transport modeling
Author(s) -
Saito Takuya,
Stein Olaf,
Tsunogai Urumu,
Kawamura Kimitaka,
Nakatsuka Takeshi,
Gamo Toshitaka,
Yoshida Naohiro
Publication year - 2011
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2010jd014602
Subject(s) - isotopologue , isotopes of carbon , atmospheric sciences , δ13c , mixing ratio , isotope , environmental science , pacific ocean , chemical transport model , stable isotope ratio , troposphere , atmospheric chemistry , oceanography , climatology , geology , ozone , total organic carbon , environmental chemistry , chemistry , meteorology , geography , physics , organic chemistry , quantum mechanics , molecule
The atmospheric mixing ratios of ethane and its stable carbon isotope ratios ( δ 13 C) were measured over the North Pacific (2°N to 38°N, 140°E to 90°W) during oceanographic cruises in summer and autumn. The measured mixing ratios were relatively low (mostly <1 ppbv) over the North Pacific, whereas elevated ethane levels (>1 ppbv) were observed over the western North Pacific near Japan, with lower δ 13 C values (approximately −25‰), suggesting recent emissions from neighboring source regions. The most 13 C‐enriched values of ethane (approximately −16‰) were observed over the western equatorial Pacific rather than the central and eastern equatorial Pacific. This is likely caused by the kinetic isotope effect (KIE) for the removal of ethane during the atmospheric transport from potential upwind source regions to the most remote region under the prevailing trade easterly winds. The measurements were compared with the results of a global chemical transport model including two ethane isotopologues ( 12 C 2 H 6 and 13 C 2 H 6 ). The model‐estimated δ 13 C values were too high compared with the observations. It is likely that this discrepancy is partly due to an approximately 40% overestimation of the reported KIE for the reaction between ethane and OH radicals.