主题：Cenozoic sea ice and climate history of the Arctic Ocean: Milestones from past and future IODP drilling
报告人：Prof. Ruediger Stein
Alfred Wegener Institute
Helmholtz Centre for Polar and Marine Research
The sea-ice cover with its strong seasonal variability in the marginal (shelf) seas has a large influence on the entire environment and climate of the Arctic Ocean, such as surface albedo, energy balance, temperature and salinity structure of the upper water masses, biological productivity, and deep water formation in the North Atlantic that drives the global thermo-haline circulation. Over the last decades, coincident with global warming and atmospheric CO2 increase, the Arctic Ocean and surrounding areas, together with the extent and thickness of Arctic sea ice, are today subject to rapid and dramatic change, of which the driving forces are not fully understood. In this context, not only high-resolution studies of the most recent (Holocene) climate history are of importance, but also detailed studies of the earlier Earth history characterized by a much warmer (Greenhouse-type) global climate with elevated atmospheric CO2 concentrations.
The long-term Cenozoic sea ice and climate history of the Arctic Ocean with its transition from a Greenhouse World with a warm ice-free Arctic Ocean to an Icehouse World with a cold ice-covered Arctic Ocean is still poorly known. The paleoclimate results from the first IODP Expedition in the Arctic Ocean (Expedition 302, Arctic Ocean Coring Expedition – ACEX) give important insight into the long-term Arctic climate history. The warm ice-free Arctic Ocean with euxinic conditions during the Eocene and the early onset of seasonal sea ice in the central Arctic Ocean during the middle Eocene might be highlighted. However, major questions related to the climate development of the Arctic Ocean from Greenhouse to Icehouse conditions during early Cenozoic times remain unanswered, largely due to the major mid-Cenozoic hiatus and partly to the poor recovery of the ACEX record. In order to decipher the pre-Quaternary climate (and sea ice) history of the Arctic in more detail, long continuous sedimentary records are planned to be recovered within a new IODP drilling campaign on southern Lomonosov Ridge during IODP Expedition 377 Arctic Ocean Paleoceanography - ArcOP in August-October 2018.