University of New Hampshire, United States

In 2004, the Integrated Ocean Drilling Program conducted the Arctic Coring Expedition (ACEX). This technically-challenging expedition recovered the first Cenozoic sediment record from the Arctic Ocean. The many results contributed by over 40 investigators from ACEX have transformed our view of the Arctic's paleoclimate. For example, during ACEX, the massulae from fresh water ferns were found at 49 Ma that suggests fresh water dominated the Arctic at that time. Ice-rafted debris was found to have occurred much earlier than previously thought during the Eocene and in an environment of high organic carbon content. Early analyses also revealed an unexpected hiatus that occurred between several of the most spectacular sediment cores in terms of color, e.g. turquoise, and structure, starkly contrasting black and white cross-bedding that is now dubbed the "zebra" core. The Paleocene-Eocene Thermal Maximum (PETM) was also recovered. Analyses have revealed surprisingly high Arctic Ocean surface water temperatures and a hydrologically active system during the PETM. ACEX results have also enabled interpretation of a major oceanographic reorganization at 17.5 Ma with ventilation of the Arctic Ocean to the North Atlantic through the Fram Strait. Here we summarize these transformational findings and the most recent results from the ACEX record that highlight sea ice and iceberg history reconstructions and descriptions of the age and depositional environments and their link to tectonic histories.