Prior to 2004, geological sampling in the Arctic Ocean was mainly restricted to near-surface Quaternary sediments. Thus, the long-term Pre-Quaternary geological history is still poorly known. With the successful completion of the Arctic Coring Expedition – ACEX (IODP Expedition 302) in 2004, a new era in Arctic research has begun. Employing a novel multi-vessel approach, the first Mission Specific Platform (MSP) expedition of IODP has proven that drilling in permanently ice-covered regions is possible.

The original ACEX sequence possibly contains a large hiatus spanning the time interval from late Eocene to middle Miocene (based on the original biostratigraphic age model) or an interval of strongly reduced sedimentation rates (new Os-Re-isotope-based age model). This is a critical interval, as it spans the time when prominent changes in global climate took place during the transition from the early Cenozoic Greenhouse world to the late Cenozoic Icehouse world.

The overall goal of the proposed drilling campaign is the recovery of a continuous stratigraphic record of the long-term Cenozoic climate history of the central Arctic Ocean. This sedimentary sequence from the central Arctic Ocean will be studied to answer the following key questions:

  • Did the Arctic Ocean climate follow the global climate evolution during its course from early Cenozoic Greenhouse to late Cenozoic Icehouse conditions?
  • Are the Early Eocene Climate Optimum and the Oligocene and Mid-Miocene warmings also reflected in Arctic Ocean records?
  • Did extensive glaciations (e.g., the OI-1 and Mi-1 glaciations) develop synchronously in both the Northern and Southern Hemispheres?
  • What is the sedimentary record of timing of repeated major (Plio-)Pleistocene Arctic glaciations as compared to that postulated from sediment echosounding and multi-channel seimic reflection profiling?
  • What was the variability of sea-ice in terms of frequency, extent and magnitude?
  • When and how did the change from a warm, fresh-water-influenced, biosilica-rich and poorly ventilated Eocene ocean to a cold, fossil-poor, and oxygenated Neogene ocean occur?
  • How critical is the exchange of water masses between the Arctic Ocean and the Atlantic and Pacific for the long-term climate evolution as well as rapid climate change?
  • What is the history of Siberian river discharge and how critical is it for sea-ice formation, water mass circulation and climate change?
  • How did the Arctic Ocean evolve during the Pliocene warm period and subsequent cooling? How do the ACEX2 records correlate with the terrestrial record from the Siberian Lake El’gygytgyn?
  • What is the cause of the major hiatus recovered in the ACEX record? Does this hiatus in fact exist?

Proposal: 708-Full (cover) and Addendum 708-Add “Arctic Ocean Paleoceanography: Towards a Continuous Cenozoic Record from a Greenhouse to an Icehouse World (ACEX2).