A New 3035.22m Deep Ice Core At Dome Fuji, Antarctica And Reconstrction Of Global Climate And Environmental Change Over Past 720kyr

The Japanese Antarctic Research Expedition succeeded in a deep ice core down to 3,035.22m in depth at Dome Fuji station (77 19'S, 39 42'S, 3,810m a.s.l.) in January 26, 2007. A previous deep ice core of 2503m length was drilled at Dome Fuji in December 1996, going back to past 340kyr. Due to the lack of hole liquid, the drill got stuck in the borehole and we could not recover it. On the assumption that the snow depositional condition from surface to 2,503m deep continues to the bottom of the ice sheet, one million-year-old ice can be expected to lie near the bedrock. For this reason, the second deep ice core drilling at Dome Fuji was started with the aim of drilling down to the bedrock. The new drilling site was constructed and ice core drilling was started in December 2003 using a new excellent deep ice core drill developed in Japan. Average coring length was 3.7m/run and the ice core drilling speed was 178m/week until 3000m deep. Under 3,000m deep, it is difficult to drill the ice sheet because of warm ice near the bedrock. Around 3,030m, the small inclusion was collected in ice. It seems to be the rock or organic matter. The water in the basal ice (or the subglacial water) cozed out to the borehole and was frozen again. The freezing water was also corrected. The ice core was transported to Japan and many kinds of analysis were started at various ice core laboratories. The oxygen isotope profile of Dome Fuji ice core suggests that the deeper part of ice goes back to 720kyr, which corresponds to MIS (Marine Isotope Stage) 17. We think that the age of bottom of ice core, which is younger than we estimated, is based on discontinuous melting of ice sheet near bedrock. Analysis carried out so far confirms that the Dome Fuji ice core have the reliable environmental and climatic record at least back to 720kyr. Overwintering glaciological and meteorological observations were performed during the past four years at Dome Fuji station. Moreover, these scientific observations were carried out between traverse routes from Syowa station to Dome Fuji station These scientific research turns into the important information when we clarify the environment information from ice core.