Insolation-triggered Eurasian Ice Sheets collapse initiates the Last Termination

The collapse of Northern Hemisphere ice sheets has been deemed as a trigger for the chain of positive climate feedback during glacial terminations in Quaternary. Increasing boreal summer insolation is considered the ultimate driver of their collapse, however, the initiating mechanisms remain elusive. Here we report an unambiguous warming trend in the southern Nordic Seas, which coincides with the initial phase of Northern Hemisphere summer insolation increase at the end of the Last Glacial Maximum. A subsequent phase of surface cooling is observed, closely corresponding to the massive freshwater discharge attributed to the meltwater pulse at 19ka BP. Our reconstructions demonstrate that the initial collapse of Northern Hemisphere ice sheets during the Last Termination occurred in Eurasian Ice Sheet, driven by a chain of oceanic responses to the insolation increase. Specifically, increasing boreal insolation induced a northward migration of the mid-latitude Westerlies under a positive NAO phase, promoting poleward oceanic heat transport and hence subsequent warming in Nordic Seas, thereby accelerating the ablation of the marine-based Eurasian Ice Shelves. This led to a catastrophic release of icebergs into Nordic Seas, eventually triggering a series of ocean circulation feedbacks that further promoted the deglaciation.