Exploring the Arctic Ocean Climate History - A challenge within the International Ocean Discovery Program (IODP).

Within IODP’s main theme „Climate and Ocean Change: Reading the Past, Informing the Future“, studying the polar regions, especially the Arctic Ocean, has been identified as key aspect. Continuous central Arctic Ocean sedimentary records, allowing a development of chronologic sequences of climate and environmental change through Cenozoic times and a comparison with global climate records, were missing prior to the IODP Expedition 302 (Arctic Ocean Coring Expedition – ACEX), the first scientific drilling in the central Arctic Ocean (Backman, J., Moran, K., McInroy, D. et al., 2006). By studying the unique ACEX sequence, a large number of scientific discoveries that describe previously unknown Arctic paleoenvironments, were obtained during the last decade (for most recent review and references see Stein et al., 2014). While these results from ACEX were unprecedented, key questions related to the climate history of the Arctic Ocean remain unanswered, in part because of poor core recovery, and in part because of the possible presence of a major mid-Cenozoic hiatus or interval of starved sedimentation within the ACEX record. In order to fill this gap in knowledge, international, multidisciplinary expeditions and projects for scientific drilling/coring in the Arctic Ocean are needed. Key areas and approaches for drilling and recovering undisturbed and complete sedimentary sequences are depth transects across the major ocean ridge systems, such as the Lomonosov Ridge. These new detailed climate records spanning time intervals from the Early Cenozoic Greenhouse world to the Neogene-Quaternary Icehouse world will give new insights into our understanding of the Arctic Ocean within the global climate system and provide an opportunity to test the performance of climate models used to predict future climate change. During the Polarstern Expedition PS87 in August-September 2014, new site survey data including detailed multibeam bathymetry, multi-channel seismic and Parasound profiling as well as geological coring, were obtained on Lomonosov Ridge (Stein, 2015). These data were the basis for a more precise planning of future Arctic Ocean drilling and update of an IODP proposal (IODP Proposal 708; http://www.iodp.org/expeditions). Most recently (April 2015), this proposal has been accepted by the IODP review panels and scheduled for drilling in 2018