Download or read book Characterization of Paleoclimate and Marine Processes Associated with Holocene Sedimentation on the Chukchi Margin, Arctic Ocean written by Chandawimal H. E. R. Siriwardana and published by . This book was released on 2014 with total page 171 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reconstructing sedimentary processes associated with the deglacial events in the Chukchi Margin is necessary to evaluate the deglacial and Holocene flow regime in the Chukchi margin area, which was the purpose of this study. To provide context for the paleoceanographic reconstruction, the modern system was explored using multispectral band ratio analysis of the marine portions of Landsat images. Terrestrial processes were investigated using visual geomorphic description and unsupervised classification to define land cover classes and sediment sources. Thermal images and band ratios clearly demonstrate that flow regimes influence sediment transport, variations of the plant pigment, sea ice content and particle density. Using 1040 samples from five sediment cores and 27 surface samples from the Chukchi Margin, sediment composition was evaluated by comparison of visible and near infrared (VNIR) derivative spectroscopy, while sediment texture was explored using laser-particle grain size analysis. Varimax-rotated principal component analysis (VPCA) on several different multivariate data sets was employed to address the multi-colinearity inherent in this type of dataset. VNIR derivative spectroscopy was used to identify mineralogical compositions of dolomite + illite; goethite + chlorophyllide-a; smectite + chlorite and calcite in the Chukchi Margin area. Strong influence of Arctic Oscillation from the mid-Holocene to present enhanced the iron minerals with a provenance from Russian seas. Enhancement of the smectite + chlorite component during 6000 to 3500 yr BP exhibits an influx of Pacific waters related to mid Holocene Warming. The enhancement of the dolomite + illite component in recent years might indicate dominant sediment provenance from east in the Victoria Island/McKenzie River basin. IIlite was identified as an appropriate water mass tracer for a reverse flow from the Arctic into the North Pacific because of its prominence and abundance in the Mackenzie River drainage basin and on the west Arctic Sea shelf (Nwadua, 2013). The overall trends in the grain size and mineralogy of the surface samples and remote sensing data of modern processes suggest possible changes in flow regime and the sediment transport in the west and east of the Barrow canyon area. In terms of grain size, four principal components of sediment deposition related to anchor ice, nepheloid flows, suspension freezing and intermittent suspension were observed. Grain size components documents that periods of high anchor ice formation are correlated with low nepheloid flows. Intermittent suspension dominates in ice-free intervals with low contributions from suspension freezing. There was evidence of an enhanced offshore transport of sediment, reworked by bottom currents when intermittent suspension was high and suspension freezing was low. High amplitude fluctuations of grain size VPCA modes around 8000 yrs BP (in JPC6 and JPC8) and in recent years (in JPC6, JPC8 and JPC 16) may be correlated with the prevalence of Holocene paleoclimatic cycles related to Mid-Holocene melting with enhanced Pacific inflow and recent cooling/ warming and volcanic events. Shorter oscillations (multi-centennial) shown in these VPCA modes may relate to possible variations of atmosphere-ocean circulation patterns, primarily the low frequency patterns associated with the Arctic Oscillation (AO). Wavelet analysis suggests cyclicity of ~1500 or > 2000 yr are common for all components in Holocene.