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"Frozen" Methane Escapes from the Sea Floor

The atmospheric concentrations of methane, a greenhouse gas, have been shown to increase in parallel with temperature increases in ice core records of glacial/interglacial cycles. Two different sources of this methane have been proposed: Methane hydrate stored in permafrost and on the sea floor, and bacterial processes in wetland environments. In this Perspective,
 Blunier
 discusses the implications of results reported by
 Kennett
 et al .
 of methane hydrate releases from the sea floor at times of rapid warming in the ice core records.