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

我们建议在千年尺度上研究布莱克-巴哈马外脊系统(北大西洋西部)的陆源和生物通量，以监测最后一次冰期(10-70KYR)期间深西部边界流(DWBC)的三维变化。这项调查将基于对第172航次期间钻探的1055至1062个ODP点的元素强度(Ca、Fe、Ti、Al、Si、Ba)的厘米分辨率X射线荧光(XRF)测量。结合详细的年龄模型和对离散样品的校准测量，XRF记录将导致生物和陆源沉积物堆积的千年尺度分辨率时间序列。对布莱克外脊(1055至1061点)深度断面(水深2164至4775m)上的这些沉积物通量的合成将有助于推断深水和中流的位置变化，从而检验模型结果，这些结果表明，上一次冰期的显著气候循环与北大西洋深水(NADW)形成的三种模式(现代模式、冰川模式和海因里希模式)有关。DWBC的相对海流强度将通过对巴哈马外脊(1062号站点)上泥波迁移的详细研究得出。此外，元素比率(如Al/Ti、Ba/Ti)将有助于探索北大西洋西部陆源和生物生产力的千禧年变化。

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.