A core transect across the southwestern Greenland Sea reveals coeval events of extremely negative planktic and benthic δ13C 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 °C. The amplitude, timing, and geographic pattern of the δ13C events suggest that this bottom-water warming triggered clathrate instability along the East Greenland slope and a methane-induced depletion of δ13CDIC (DIC— dissolved inorganic carbon). Since δ13C 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.