Unravelling Greenland Ice Sheet and Arctic climate history over the last 30 Million years – Results from IODP Expedition 400

Understanding the history of the northern Greenland Ice Sheet (NGrIS) and its connection to long-term changes in the Arctic is crucial for assessing glacial instability thresholds and the cryosphere's response to greenhouse gas emissions. To fill knowledge gaps in the evolution of the GrIS and its climate role, IODP Expedition 400 collected sedimentary records from Sites U1603–U1608 along the northwest Greenland margin and into Baffin Bay. These sites recover a range of deep ocean-to-shelf depositional settings and lithofacies which form proximal archives of NGrIS evolution through the late Cenozoic era.  Across six sites, 2299 meters of core material were recovered, and wireline logging was conducted at four sites. The expedition targeted high-accumulation contourite drifts within, and below, a well-mapped trough mouth fan system. At Site U1607, deep time objectives were achieved with cores extending to 978 meters below the seafloor, capturing Miocene and late Oligocene sediments. This presentation summarizes the initial results in alignment with the key scientific objectives pursued by the expedition scientists: (1) evaluating near-complete NGrIS deglaciations during the Pleistocene and mid-Pleistocene orbital shifts, (2) examining NGrIS expansion timing and links to Pliocene marine heat transport, and (3) studying climate-ecosystem conditions under higher atmospheric CO2 levels over the past 30 million years. The X400 shipboard results, and the ensuing post-cruise research, will enable the assessment of the forcings—oceanic, atmospheric, orbital, and tectonic—affecting the GrIS over various timescales and improve models of glacial inception and interglacial transitions.