North atlantic arctic Gateways II

Abstract

Leg 162 is the second of two legs designed to investigate what role three major northern geographical areas (the Northern Gateway region, the Greenland-Norway sea, and the Southern Gateway region) have played in regulating the global climate system. To accomplish this goal the biogenic fluxes (CaCO3, opal, and organic carbon), lithologic fluxes, and geochemical records contained in the cores were, and will continue to be, analyzed in order to reconstruct the temporal and spatial variability of the oceanic heat budget, the history of intermediate and deep water formation, and the history of glaciation on the surrounding land masses on millennial, Milankovitch, and tectonic time scales. In addition, because of the very high sedimentation rates (10-20 cm/ky) at some of the drilled sites, we will be able to analyze the sediments on century (Dansgaard-Oeschger events) time scales. Perhaps more importantly, these paleoceanographic reconstructions will span millions of years instead of the 100,000-year time-spans typical of piston cores. Before generating time scales for these sedimentary sequences, composite records were constructed at each site based on continuous data obtained by the multisensor track (including magnetic susceptibility, natural gamma radiation, and gamma-ray attenuation, or GRAPE, which measures bulk density), as well as on color spectral reflectance measurements. The sites are arrayed, in combination with the Leg 151 sites, as broad north-south and east-west transects to examine the evolution of vertical and horizontal gradients in water-mass properties over time and to date the inception of high northern latitude glaciation. The drilling schedule included 56 days at sea with coring operations at nine sites (Sites 907, 980, 981, 982, 983, 984, 985, 986, 987). We began on the sediment drifts south of Iceland, eventually moving northward to the Svalbard Margin, Fram Strait, and the East Greenland Margin as sea ice retreated through the month of August. Overall, we recovered 6730.74 m of core, setting a new record for recovery during a single leg, and made over 1 million shipboard measurements.