Dissolved methane in the US GEOTRACES Arctic section

Methane is a greenhouse gas with a warming potential greater than that of carbon dioxide. The sediments of the Arctic Ocean are host to large reservoirs of methane which may be released as a consequence of climate change and thereby serve as a positive feedback. Determination of the distribution of dissolved methane in the Arctic Ocean and fluxes of this gas to the atmosphere is thus of great interest. We are currently determining dissolved methane in the Arctic Ocean, both in discrete samples from Niskin bottles as well as in continuous underway surface sampling, as part of the US GEOTRACES Arctic section. This section began in the Aleutians, headed north through the Bering and Chukchi Seas and arrived at the North Pole on 5 Sept. 2015 aboard USCGC Healy before heading south again. Preliminary results show near-surface dissolved methane concentrations ranging from near atmospheric equilibrium to values at least double atmospheric. With depth, concentrations typically increase to maxima associated with either the chlorophyll max or with apparent off-shelf methane transport. In deep waters of the Makarov Basin, dissolved methane is near 1 nM in concentration, similar to deep waters of other ocean basins.