NOAA/WDS Paleoclimatology - Healy-Oden Trans Arctic Expedition(HOTRAX) Grain Size, XRF, and Reflectance Data

Sediment clay and silt mineral assemblages provide an excellent means of assessing the provenance of fine-grained Arctic sediment especially when a unique mineral assemblage can be tied to specific source areas. The diffuse spectral reflectance (DSR) first derivative measurements and quantitative X-Ray Diffraction (qXRD) on a high-resolution sediment core from the continental slope north of Alaska constrain the sediment mineralogy. DSR results are augmented by measurements on several adjacent cores and compared to surface sediment samples from the northern Alaskan shelf and slope. Using Principal Component Analysis (PCA), we infer that the three leading DSR modes relate to mixtures of smectite + dolomite, illite + goethite, and chlorite + muscovite. This interpretation is consistent with the down core qXRD results. While the smectite + dolomite, and illite + goethite factors show increased variability down core, the chlorite + muscovite factor had highest positive loadings in the middle Holocene, between ca. 6.0 and 3.6 ka. Because the most likely source of the chlorite + muscovite suite in this vicinity lies in the North Pacific, we argue that the oscillations in chlorite + muscovite values likely reflect an increase in the inflow of Pacific water to the Arctic through the Bering Strait. The time interval of this event is associated in other parts of the globe with a non-linear response of the climate system to the decrease in insolation, which may be related to changes in water exchange between the Pacific and Arctic Ocean.

沉积物黏土与粉砂的矿物组合是评估北极细粒沉积物物源的极佳途径，尤其当独特的矿物组合可与特定源区建立对应关系时。本研究对阿拉斯加北部大陆坡的一根高分辨率沉积物岩芯开展了漫反射光谱（diffuse spectral reflectance, DSR）一阶导数测量与定量X射线衍射（quantitative X-Ray Diffraction, qXRD）分析，以此限定沉积物的矿物组成。研究通过对相邻多根岩芯的测量补充了DSR数据集，并将分析结果与阿拉斯加北部陆架及陆坡的表层沉积物样品进行对比。借助主成分分析（Principal Component Analysis, PCA），我们推断出前三个主导DSR模态分别对应蒙脱石-白云石、伊利石-针铁矿以及绿泥石-白云母的矿物组合。该解释与岩芯纵向的qXRD分析结果高度一致。尽管蒙脱石-白云石与伊利石-针铁矿这两个组分在岩芯纵向序列中表现出更强的变异性，但绿泥石-白云母组分在全新世中期（约6.0~3.6 ka之间）呈现最高正载荷。鉴于该区域内绿泥石-白云母组合最可能的物源来自北太平洋，我们认为绿泥石-白云母组分的浓度波动大概率反映了太平洋海水经白令海峡流入北冰洋的通量增加。该事件的时间区间在全球其他区域与气候系统对日射量减少的非线性响应相关联，这一现象可能与太平洋与北冰洋之间的水体交换变化存在关联。