Millennial-scale changes in position and intensity of the Deep Western Boundary Current (DWBC) during the last glacial period

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We propose to study terrigenous and biogenic fluxes on the Blake-Bahama Outer Ridge system (Western North Atlantic) at millennial scale resolution to monitor changes of the Deep Western Boundary Current (DWBC) through the last glacial period (10-70 kyr) in 3 dimensions. The investigation will be based on cm-resolution X-ray fluorescence (XRF) measurements of element intensities (Ca, Fe, Ti, Al, Si, Ba) on ODP Sites 1055 to 1062 drilled during Leg 172. Combined with detailed age models and calibration measurements on discrete samples the XRF records will result in millennial-scale resolution time series of biogenic and terrigenous sediment accumulation. A synthesis of these sediment fluxes along a depth transect (2164 to 4775 m water depth) on the Blake Outer Ridge (Sites 1055 to 1061) will allow to infer changes in the position of deep and intermediate water flow and thus be a test for model results that suggest that the prominent climate cycles of the last glacial period known als Dansgaard/Oeschger and Heinrich events were linked to three modes of North Atlantic Deep Water (NADW) formation (modern-, glacial-, and Heinrich mode). The relative current intensity of the DWBC will be derived from a detailed study of mud wave migration on the Bahama Outer Ridge (Site 1062). Furthermore elemental ratios (e.g. Al/Ti, Ba/Ti) will help to explore millennial changes in terrigenous provenance and biogenic productivity in the western North Atlantic.