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Methane and nitrous oxide distributions across the North American Arctic Ocean during summer, 2015
Author(s) -
Fenwick Lindsay,
Capelle David,
Damm Ellen,
Zimmermann Sarah,
Williams William J.,
Vagle Svein,
Tortell Philippe D.
Publication year - 2017
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2016jc012493
Subject(s) - oceanography , water column , canada basin , arctic , bay , halocline , transect , hydrography , sink (geography) , seawater , environmental science , methane , sea ice , geology , chemistry , salinity , geography , cartography , organic chemistry
We collected Arctic Ocean water column samples for methane (CH 4 ) and nitrous oxide (N 2 O) analysis on three separate cruises in the summer and fall of 2015, covering a ∼10,000 km transect from the Bering Sea to Baffin Bay. This provided a three‐dimensional view of CH 4 and N 2 O distributions across contrasting hydrographic environments, from the oligotrophic waters of the deep Canada Basin and Baffin Bay, to the productive shelves of the Bering and Chukchi Seas. Percent saturation relative to atmospheric equilibrium ranged from 30 to 800% for CH 4 and 75 to 145% for N 2 O, with the highest concentrations of both gases occurring in the northern Chukchi Sea. Nitrogen cycling in the shelf sediments of the Bering and Chukchi Seas likely constituted the major source of N 2 O to the water column, and the resulting high N 2 O concentrations were transported across the Arctic Ocean in eastward‐flowing water masses. Methane concentrations were more spatially heterogeneous, reflecting a variety of localized inputs, including likely sources from sedimentary methanogenesis and sea ice processes. Unlike N 2 O, CH 4 was rapidly consumed through microbial oxidation in the water column, as shown by the 13 C enrichment of CH 4 with decreasing concentrations. For both CH 4 and N 2 O, sea‐air fluxes were close to neutral, indicating that our sampling region was neither a major source nor sink of these gases. Our results provide insight into the factors controlling the distribution of CH 4 and N 2 O in the North American Arctic Ocean, and an important baseline data set against which future changes can be assessed.