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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.
The Arctic Ocean sediment (AOS) is highly sensitive to global climate changes and has become a focus of much paleoclimatic research. In this study, paleoclimatic characteristics of the AOS have been studied using downcore X-Ray Fluorescence (XRF) data from 13 Healy-Oden TransArctic Expedition cores. Lithological and multi-element variations representing glacial and interglacial cycles were correlated using the variable-based Varimax-rotated Principal Component Analysis (VPCA) of the XRF data. The main components generated by the VPCA have been interpreted as related to terrigenous (erosional) sources (F1, Ti-K-Rb-Fe-Ba-Cr), changes in Laurentide Ice Sheet (LIS) (F3, Ca-P-I), pore water concentration/ biogenic productivity (F5, P-Cl-S), bottom-water ventilation (F6, Mn-Ni-Cu) and siliciclastics (F7, Sr-Zr). Component variations are well consistent with glacial ("gray beds")-interglacial("brown beds") cycles and associated deglacial carbonate pulses in the core 8JPC with identified age controls of Adler et al., 2009 and Polyak et al., 2009. Mn-rich layers (corresponding F6 peaks) of interglacial origin are generally anticorrelated with Ca pulses (F3 peaks) generated during deglaciations. Cl data show general enhancement with interglacials and glacial gray beds with coarse detrital sand pulses suggesting saline pore water trapped within the porosity of these coarser beds. Pleistocene sedimentation is characterized with only a few shallow carbonate spikes, which indicate a weakened Beaufort Gyre and stronger Transpolar Drift as indicated by the lower abundance of Laurentide material in the Eurasian Basin. The Visible-Near Infrared (VNIR) derivative spectroscopy study of the sediment core P1-92AR-P25 (or P25) demonstrates cyclic variations in downcore mineralogy. VPCA of the downcore VNIR data show three mineral assemblages reflecting glacial-interglacial cyclicity. The results are consistent with clay mineral cycles identified by previous studies (Yurco et al. 2010). The downcore mineralogical cyclicity provides a glacial-interglacial portrait of changes in sediment provenance indicative of both Laurentide and Eurasian sources and delivery mechanisms associated with changes in sea level, configurations of Arctic ice sheets and oceanic/atmospheric circulation. The study further reveals that the VNIR spectroscopy can be used as an effective tool in semi quantitative prediction of dolomites. Wavelet analysis in component scores of 8JPC (XRF data) and P25 (VNIR data) identifies significant periodicities; eccentricity (~100 kyr), Obliquity (~40 kyr) and precession (~21 kyr). In both 8JPC and P25 glacial-interglacial variations show eccentricity whereas in 8JPC, LIS changes and biogenic productivity represent precession cycles and in P25 carbonate sedimentation displays strong obliquity (~40 kyr) cycles with moderate influence of precession (~21 kyr) cycles probably representing IRD events in stadial/ interstadial cycles associated with Heinrich and Bond cycles. These findings agree with Adler et al., 2009 that AOS reflects insolation-controlled paleoclimatic processes with longer-term glacial cycles interrupted with abrupt iceberg/melt water discharges of both Laurentide and Eurasian sources. High resolution age control is critical for better evaluation of periodicities of paleoclimatic variations.
The delivery of sediment to the Alaskan continental shelf is largely associated with sea-ice drift and wind driven Arctic Ocean circulation patterns that have varied during the Holocene. This study presents a comparison of two high-resolution proxy records from the western Arctic over the past 2,000 years. To provide variations of sedimentation patterns in the Arctic Ocean (e.g., sea-ice transport, density flows, ocean currents), the grain size distributions were measured in a piston core (HLY02-04 JPC16) from the eastern Chukchi Sea at a higher resolution than previously reported. A revised JPC16 age-depth model was used in this analysis (Darby et al., 2012). The sediment core, collected on the east flank of Barrow Canyon (72.1555°N, 153.50817°W, ~1300 mwd), preserves a record of local variations in sedimentation mechanisms in the Chukchi-Beaufort Seas. A Varimax-rotated Principle Component Analysis (VPCA) was conducted on the grain-size data from JPC16. We inferred three principal components (PCs) of sediment deposition at the core site related to anchor ice, nepheloid flows, and suspension freezing based on variations in grain-size distributions from a Malvern Mastersizer sediment analysis. This interpretation is consistent with previous downcore analysis by Darby et al. (2009) on multiple western Arctic Ocean cores. A fourth, much less significant mode, is related to resuspension and deposition connected to intermittent suspension and ocean currents. While all VPCA modes showed increased variability since 200 yr BP, components related to sea-ice showed the highest positive loadings between 2000-1300 cal yr BP. The most likely cause of positive anomalies observed in these two components is associated with increased ice melt and settling of sediment, or a greater influx of sea-ice into Alaskan waters. It can therefore be argued that oscillations in these modes are closely related to changes in atmospheric temperature or oscillations in the atmosphere-ocean circulation patterns, primarily the Arctic Oscillation. The high-resolution record of sediment deposition in the Arctic Ocean allowed for direct correlation with an atmospheric climate proxy as recorded by varve thickness measurements retrieved from a glacial lake located in the Brooks Range (Bird et al., 2009). The time interval investigated here shows a significant relationship between marine sea-ice sedimentation and atmospheric temperature (r = 0.7). This analysis suggests that warmer atmospheric intervals are likely related to greater sea-ice melt and sedimentation of entrained sediments.
Although it is generally accepted that the Arctic Ocean is a very sensitive and important region for changes in the global climate, this region is the last major physiographic province of the earth whose short-and long-term geological history is much less known in comparison to other ocean regions. This lack of knowledge is mainly caused by the major technological/logistic problems in reaching this harsh, ice-covered region with normal research vessels and in retrieving long and undisturbed sediment cores. During the the last about 20 years, however, several international and multidisciplinary ship expeditions, including the first scientific drilling on Lomonosov Ridge in 2004, a break-through in Arctic research, were carried out into the central Artic and its surrounding shelf seas. Results from these expeditions have greatly advanced our knowledge on Arctic Ocean paleoenvironments. Published syntheses about the knowledge on Arctic Ocean geology, on the other hand, are based on data available prior to 1990. A comprehensive compilation of data on Arctic Ocean paleoenvironment and its short-and long-term variability based on the huge amount of new data including the ACEX drilling data, has not been available yet. With this book, presenting (1) detailed information on glacio-marine sedimentary processes and geological proxies used for paleoenvironmental reconstructions, and (2) detailed geological data on modern environments, Quaternary variability on different time scales as well as the long-term climate history during Mesozoic-Tertiary times, this gap in knowledge will be filled. *Aimed at specialists and graduates *Presents background research, recent developments, and future trends *Written by a leading scholar and industry expert
The deglacial behavior of the sub-Arctic North Pacific is poorly constrained, with many published records suffering from limited age control due to extensive post- depositional biogenic carbonate dissolution. Potential alternative dating methods could include the correlation of stable-isotopic and/or paleomagnetic secular variation records to an independently-dated regional template, however no such template currently exists. Cores EW0408-85JC (59°33.32'N, 144°9.21'W, 682 m water depth) and EW0408-79JC (59°33.32'N, 144°9.21'W, 682 m water depth) are located above the carbonate compensation depth on the Gulf of Alaska margin, affording an opportunity to inter- compare stable-isotopic and paleomagnetic variability from a single location, as well as to place observations of Northeast Pacific paleoclimate and paleomagnetic secular variation in a global context via an independent radiocarbon-based chronology. We evaluate three possible age models for core EW0408-85JC and their implications for North Pacific stable isotopic and paleoventilation behavior. These include calibrated planktonic and benthic foraminiferal radiocarbon dates, assuming constant reservoir ages, as well as a correlation of planktonic [delta]18O in foraminifera to [delta]18O in a layer-counted Greenland ice core (NGRIP). We conclude that the calibrated planktonic dates provide the most accurate chronology. Benthic foraminiferal radiocarbon dates evaluated on this age model indicate that intermediate-depth ventilation ages at the site increased to>2,670 ± 180 during Termination 1, implying reduced ventilation relative to the Holocene average of 1,740 ± 210 yr. The shift to lower ventilation ages occurs at ~10,500 cal ybp, coeval with the flooding of Beringia and the opening of the Bering Strait, suggesting that flooded shelves and net export of low- salinity surface waters enhanced ventilation of the North Pacific. Oxygen isotope data from planktonic and benthic foraminifera, interpreted on this age model, document surface freshening by 16,650 ± 170 cal ybp, likely due to freshwater input from retreating regional glaciers. A sharp transition to laminated hemipelagic sedimentation at 14,790 ± 380 cal ybp is coincident with abrupt warming and/or freshening of the surface ocean (i.e. additional [delta]18O reduction of 0.9 [per mil]), essentially coincident with the Bolling Interstade of Northern Europe and Greenland. Cooling and/or higher salinities returned during the Allerod interval, coeval with the Antarctic Cold Reversal and continuing until 11,740 ± 200 cal ybp, when the onset of warming coincides with the end of the Younger Dryas. This may indicate convolved Northern and Southern drivers of climate variability in the North Pacific. Two laminated opal-rich intervals record episodes of high productivity are observed from 14,790 ± 380 to 12,990 ± 190 cal ybp, and from 11,160 ± 130 to 10,750 ± 220 cal ybp. These events likely correlate to similar observations elsewhere on the margins of the North Pacific, and may be driven my remobilization of iron from newly inundated continental shelves during episodes of rapid sea-level rise. High-resolution paleomagnetic secular variation (PSV) records from the Gulf of Alaska constrain regional field behavior and provide information on larger scale geomagnetic dynamics. Both cores studied (EW0408-79JC and 85JC) preserve a generally strong and relatively stable (MAD
New geophysical techniques (multibeam echo sounding and 3D seismics) have revolutionized high-resolution imaging of the modern seafloor and palaeo-shelf surfaces in Arctic and Antarctic waters, generating vast quantities of data and novel insights into sedimentary architecture and past environmental conditions. The Atlas of Submarine Glacial Landforms is a comprehensive and timely summary of the current state of knowledge of these high-latitude glacier-influenced systems. The Atlas presents over 180 contributions describing, illustrating and discussing the full variability of landforms found on the high-latitude glacier-influenced seafloor, from fjords and continental shelves to the continental slope, rise and deep-sea basins beyond. The distribution and geometry of these submarine landforms provide key information on past ice-sheet extent and the direction and nature of ice flow and dynamics. The papers discuss individual seafloor landforms, landform assemblages and entire landsystems from relatively mild to extreme glacimarine climatic settings and on timescales from the modern margins of tidewater glaciers, through Quaternary examples to ancient glaciations in the Late Ordovician.