Methane-driven late Pleistocene δ13C minima and overflow reversals in the southwestern Greenland Sea

A core transect across the southwestern Greenland Sea reveals coeval events of extremely negative planktic and benthic delta C-13 excursions between 40 and 87 ka. The most pronounced event, event 1, began at peak Dansgaard-Oeschger stadial 22 (85 ka) with a duration of 18 k.y. During this episode, incursions of Atlantic Intermediate Water caused a bottom-water warming of up to 8 degrees C. The amplitude, timing, and geographic pattern of the delta C-13 events suggest that this bottom-water warming triggered clathrate instability along the East Greenland slope and a methane-induced depletion of delta C-13(DIC) (DIC-dissolved inorganic carbon). Since delta C-13 event 1 matches a major peak in atmospheric CH4 concentration, this clathrate destabilization may have contributed to the rise in atmospheric CH4 and thus to climate warming over marine isotope stage 5.1.