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Radiocarbon in Marine Methane Reveals Patchy Impact of Seeps on Surface Waters
Author(s) -
Joung DongJoo,
Leonte Mihai,
Valentine David L.,
Sparrow Katy J.,
Weber Thomas,
Kessler John D.
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl089516
Subject(s) - petroleum seep , methane , radiocarbon dating , biogeochemistry , geology , seawater , oceanography , surface water , atmosphere (unit) , environmental science , chemistry , paleontology , geography , organic chemistry , environmental engineering , meteorology
Geological sources of methane (CH 4 ), such as hydrocarbon seeps, are significant yet poorly constrained sources of CH 4 to seawater and the overlying atmosphere . We investigate the radiocarbon content ( 14 C) and concentrations of dissolved CH 4 in surface waters from the Coal Oil Point seep field to test the hypothesis that geological sources can dominate the regional background signal of CH 4 . We find that surface waters with elevated CH 4 concentration were populated with seep‐CH 4 and that lower concentrations of CH 4 were well explained by mixing with the regional background of nongeological CH 4 . Substantial differences in concentration and 14 C‐CH 4 were observed over distances <5 km, demonstrating that surface currents mix background‐CH 4 into the seep field. These results indicate that even a prolific seep region like the Santa Barbara Basin exerts limited influence on the regional background of CH 4 in the surface layer but is a significant driver of patchiness in oceanic CH 4 biogeochemistry.