Sources and sinks of methane in sea ice

We report on methane (CH4) stable isotope (?13C and ?2H) measurements from landfast sea ice collected near Barrow (Utqiagvik, Alaska) Cape Evans (Antarctica) over the winter-to-spring transition. These provide novel insights into pathways of CH4 production consumption in ice. found substantial differences between two sites. Sea overlying shallow shelf was supersaturated with a clear microbial origin, most likely methanogenesis sediments. estimated that situ oxidation consumed fraction being supplied to ice, partly explaining large range isotopic values observed –68.5 –48.5 ‰ ?2H –246 –104 ‰). at also but surprisingly high ?13C (between –46.9 –13.0 ‰), whereas –313 –113 ‰) were those Barrow. are first composition Antarctic Our data set suggests potential combination hydrothermal source, vicinity Mount Erebus, aerobic formation although metabolic pathway for latter still needs be elucidated. observations show considered as an active biogeochemical interface, contributing consumption, which disputes standing paradigm is inert barrier passively accumulating ocean-atmosphere boundary.