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  • Abstract: During glacial/interglacial cycles, changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC) modified the intermediate and deep-water mass proportions and high latitude productivity in the Atlantic Ocean. These factors influence the distribution and geochemical partitioning of trace metals in the ocean. Mercury is a redox and productivity-sensitive trace metal, making it a potential proxy of paleoenvironmental changes. Therefore, this work examines the effect of Atlantic Ocean circulation changes during the last two glacial/interglacial cycles on the biogeochemistry of Hg. For this, a high-resolution record of the total Hg concentration was determined in core GL-1090 collected from the Southwestern Subtropical Atlantic that represents the last 185 thousand years. During the reported glacial/interglacial cycles, Hg showed a distinct trend throughout Marine Isotope Stages with higher concentrations during periods of enhanced penetration of northern component water into the southwestern Atlantic. This is supported by the similarity of mercury variability with benthic foraminifera δ¹³C, suggesting a strong influence of deep ocean circulation on the availability and accumulation of this metal in deep-sea sediments. Mercury geochemistry and particle scavenging were correlated with organic matter (OM) input at the core site. We also noted that mercury responded to redox variation in sediment after Termination II, which can be explained by the increase in deep ocean ventilation due to AMOC strengthening. This hypothesis was confirmed by the antiphase behavior of Hg and Total Organic Carbon when compared with Mn/Al ratios and CaCO3. Our work, therefore, allows for a better understanding of the processes leading to long-term mercury removal to sediments. Category: geoscientificInformation Source: Not Available Supplemental Information: Not Availble Coverage: Not Available
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  • Abstract: Quality-controlled meteorological/snow measurement data obtained from a research-oriented automated weather station (AWS) installed in the observation field of the Institute of Low Temperature Science (ILTS), Hokkaido University, Sapporo, Japan maintained by the Meteorological Research Institute, Japan Meteorological Agency (MRI/JMA) and ILTS are presented. Originally, the AWS was installed to utilize the data for process studies related to the snow-atmosphere interaction, then contributed to the development of a physically based snow albedo model of MRI/JMA. After the success, the data were used again for the development of a detailed physical snowpack model by MRI/JMA. Apart from that, the data were used to propose a light scattering model of snow grains and snow impurities for accurate radiative transfer modeling and satellite remote sensing. Some of the data presented here have ever contributed to the international snow model inter-comparison project ESM-SnowMIP, where this observation site is the only station chosen from Asia. The dataset includes 1. Gap-filled half-hourly meteorological/snow data from November to April to drive snow models (snow depth, precipitation, wind speed, air temperature, relative humidity, surface pressure, downward shortwave and longwave radiant fluxes, solar zenith and azimuth angles, direct and diffuse components of downward visible and near-infrared radiant fluxes, ground surface heat flux, and soil temperature at 100 cm depth), 2. Half-hourly radiation measurement data for snow physical process studies from November to April (snow depth, shortwave, visible, and near-infrared albedos, snow surface temperature, downward and upward radiant fluxes, and diffuse and direct components of downward radiant fluxes), and 3. Spectral albedo and diffuse fraction data measured with a ground-based spectral radiometer system for albedo and flux (GSAF). Category: geoscientificInformation Source: Not Available Supplemental Information: Not Availble Coverage: Not Available
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  • Abstract: The object of research is the Holocene massive ice veins on the Eastern coast of the Daurkin Peninsula, the easternmost part of the Chukotka. Peat bogs with ice veins occur on the surface of marine terraces (near Uelen and Lorino settlements) and on flood plain of the Koolen' Lake; the thickness of peat varies from 0.7 to 2.5 m. Radiocarbon dating of the peat enclosing the investigated ice veins near Uelen and Lorino indicated that the beginning of peat accumulation began at the end of Late Pleistocene - early Holocene, about 11 cal ka BP. On the flood plain of the Koolen' Lake peat bogs began to accumulate in the middle Holocene, i.e. around 6 cal ka BP. At the initial stage of peat bogs formation the rate of peat accumulation was high and could reach 1 cm/10 years. Ice veins occur at a depth of 0.5-1 m, and their lower parts are located in the underlying peat sandy loams and loams. In the upper levels of the peat bogs, narrow present-day ice veins are found, which are sometimes embedded in the upper parts of Holocene veins. A clear sign of syngenetic growth of veins is the upward bending of the layers of the host peat at the lateral contacts with the veins. The main source of water for the formation of ice veins is snow, as evidenced by the ratio of stable isotopes of oxygen and hydrogen and the values of deuterium excesses in the ice. A slight admixture of saline water (probably from a seasonally thawed layer) was noted in the veins near the Lorino settlement. Reconstructions of winter air paleotemperatures, performed on the basis of data of isotope-oxygen composition of ice from the veins, did show that at the period between 11 and 6 cal Ka BP, the mean winter air temperature on the Daurkin Peninsula was by 2-5 °C lower than today, but the air temperature of the coldest month (January or February) was still lower (by 4-8 °C) than today. The noticeable trend of increase of stable isotope values in the ice veins from early Holocene to the present time is indicative of a steady positive trend of mean winter air temperatures in the Holocene. Category: geoscientificInformation Source: Not Available Supplemental Information: Data was submitted and proofread by Yurij K Vasil'chuk and Lyubov Bludushkina at the faculty of Geography, department of Geochemistry of Landscapes and Geography of Soils, Lomonosov Moscow State University. Coverage: Not Available
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  • Abstract: The study focuses on the structure of thick peatlands with syngenetic ice wedges in the Yamal and Gydan Peninsulas (northern West Siberia). Thick polygonal peatlands formed in floodplains and laidas or in lacustrine-palustrine inliers within hypsometrically higher terraces. Peat accumulated at rates of several mm per year so the peatland reached thicknesses of 4-5 m in 700-1000 years. The presence of Boreal (Holocene) tree macrofossils at the base of many peat sections confirms the tree line advance as far as the contemporary tundra during the Holocene optimum. Category: geoscientificInformation Source: Not Available Supplemental Information: Data was submitted and proofread by Yurij K Vasil'chuk and Lyubov Bludushkina at the faculty of Geography, department of Geochemistry of Landscapes and Geography of Soils, Lomonosov Moscow State University. Coverage: Not Available
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  • Abstract: The Duvanny Yar cross-section located in the Lower Kolyma River valley of Northern Yakutia (69°N, 158°E, height above the Kolyma River level 55 m), has been studied and dated in detail by radiocarbon. The sequence mainly consists of sandy loam sediments with large syngenetic ice wedges. Their width at the top is 1-3.5 m. Allochthonous organic material occurs in high content, concentrating as 0.5-0.7 m lenses. Shrub fragments, twigs, and mammoth bones are accumulated in peaty layers. Through interpolation based on a series of ¹⁴C dates, dating of the host sediments provides an approximate age for the ice wedges. The ¹⁴C dates of various types of organic material are sometimes very close, but not all in agreement. Therefore, the dates do not accurately show the age of the δ¹⁸O and δ²H plots. A new approach is developed to a ¹⁴C dating strategy of syncryogenic sediments with high admixture of allochthonous organic material. The main purpose of this study is to consider detection of inversions or disturbances in the syngenetic permafrost sediment at the Duvanny Yar cross-section by ¹⁴C date series. Direct accelerator mass spectrometry (AMS) dating of the ice confirmed the relatively young age of ice wedges. Category: geoscientificInformation Source: Not Available Supplemental Information: Data was submitted and proofread by Yurij K Vasil'chuk and Lyubov Bludushkina at the faculty of Geography, department of Geochemistry of Landscapes and Geography of Soils, Lomonosov Moscow State University. Coverage: Not Available
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  • Abstract: The purpose of this work is to prove the genetic diversity, i.e., heterogeneity of the Duvanny Yar edoma sequence, as well as its nonsimultaneous formation, i.e., the heterochronous nature of its different parts along both vertical and lateral directions, based on the study of the cryogenic structure of the whole massif and the correlation of previously obtained radiocarbon ages with the AMS and other new data on the ages of organic microinclusions, alkaline extracts, and spore-pollen concentrate, which have been extracted directly from the Late Pleistocene syngenetic recurrent ice wedge complex. The results obtained have made it possible to propose a fundamentally new version of the structure, age, and formation conditions of the studied Late Pleistocene polygonal ice-wedge complex. Category: geoscientificInformation Source: Not Available Supplemental Information: Data was submitted and proofread by Yurij K Vasil'chuk and Lyubov Bludushkina at the faculty of Geography, department of Geochemistry of Landscapes and Geography of Soils, Lomonosov Moscow State University. Coverage: Not Available
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  • Abstract: Accelerator mass spectrometry (AMS) radiocarbon dates of pollen concentrate were obtained from multistage syngenetic ice wedges of cross-sections from the Late Pleistocene Bison site, located along the Lower Kolyma River (68°34'N, 158°34'E), from ∼43,600 to ∼26,200 BP, and 3 AMS ¹⁴C dates of pollen concentrate in ice wedges from the Seyaha site cross-section, located on the east coast of the Yamal Peninsula (70°10'N, 72°34'E), from ∼22,400 to ∼25,200 BP. Pollen concentrate samples were prepared using a special pretreatment procedure. Pollen and spores from ice-wedge ice signalize a regional pollen rain. Therefore, ¹⁴C-dated extracts of pollen and spores from ice-wedge ice enable an adequate reconstruction and chronology of landscape dynamics on a regional scale. The pollen and spores were well preserved despite numerous redepositions in the penecontemporaneous structure in which they were found. Thus, a comparison with dates on other fractions from the same sample is necessary. The youngest date is the most reliable among the intersample AMS ¹⁴C dates from the ice and permafrost sediments. Category: geoscientificInformation Source: Not Available Supplemental Information: Data was submitted and proofread by Yurij K Vasil'chuk and Lyubov Bludushkina at the faculty of Geography, department of Geochemistry of Landscapes and Geography of Soils, Lomonosov Moscow State University. Coverage: Not Available
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  • Abstract: The stable oxygen isotope composition of Late Holocene syngenetic ice wedges from the Erkutayakha River valley in the Yamal Peninsula and from the Adventdalen valley in Svalbard was studied. It was demonstrated that the studied ice wedges located 2000 km apart were formed during the last 2-3.5 ka and continue to grow at present. Variations of δ¹⁸O values of the ice of both ice wedges do not exceed 2-3.5‰. Based on the oxygen isotope variations is has been calculated that mean winter air temperatures did not change by more than 3 °C during the Late Holocene. Category: geoscientificInformation Source: Not Available Supplemental Information: Data was submitted and proofread by Yurij K Vasil'chuk and Lyubov Bludushkina at the faculty of Geography, department of Geochemistry of Landscapes and Geography of Soils, Lomonosov Moscow State University. Coverage: Not Available
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  • Abstract: Paleomagnetic results derived from sixteen Black Sea sediment cores. The natural remanent magnetization (NRM) and the anhysteretic remanent magnetization (ARM) were measured with a 2G Enterprises 755 SRM (cryogenic) long-core magnetometer equipped with a sample holder for eight discrete samples at a separation of 20 cm. The magnetometer's in-line tri-axial alternating field (AF) demagnetizer was used to demagnetize the NRM and ARM of the samples. The NRM was measured after application of AF peak amplitudes of 0, 5, 10, 15, 20, 30, 40, 50, 65, 80, and 100 mT. Directions of the characteristic remanent magnetization (ChRM) were determined by principle component analysis (PCA) according to Kirschvink (1980). The error range of the ChRM is given as the maximum angular deviation (MAD). The ARM was imparted along the samples' z-axis with a static field of 0.05 mT and an AF field of 100 mT. Demagnetization then was performed in steps of 0, 10, 20, 30, 40, 50, 65, and 80 mT. The median destructive field of the ARM (MDFARM) was determined to estimate the coercivity of the sediments. The slope of NRM versus ARM of common demagnetization steps was used to determine the relative paleointensity (rPI). In most cases, demagnetization steps from 20 to 65 mT were used to determine the rPI. Note, in all studied Black Sea sediment cores, samples with SIRM/κ~LF~ ratios >10 kAm^-1^ (SIRM: saturated iso-thermal remanent magnetization, κ~LF~: low-field magnetic susceptibility), empirically found to indicate the presence of diagenetically formed greigite, were omitted for paleomagnetic studies. I chrm: characteristic inclination D chrm: characteristic declination Slope-rPI: relative paleointensity determined by slope NRM/ARM during alternating field demagnetization; NRM: natural remanent magnetization, ARM: anhysteretic remanent magnetization Category: geoscientificInformation Source: Not Available Supplemental Information: Not Availble Coverage: Not Available
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  • Abstract: Age models of M72/5 cores were constrained by 16 accelerator mass spectrometry (AMS) 14C dating in core M72/5-24GC3 (Nowaczyk et al., 2012), and by identifications of the Campanian Ignimbrite tephra at 39.3 ± 0.11 ka ('Y5', e.g., De Vivo et al., 2001) and the Cape Riva tephra at 21.8 ± 0.4 ka ('Y2' e.g., Fabbro et al., 2013) in Black Sea sediments reported by Cullen et al. (2014) and Nowaczyk et al. (2012). The cores' age models were further refined by tuning sedimentologic parameters, e.g., ice rafted debris (IRD) counts and X-ray fluorescence (XRF) logs (mainly Ca/Ti and K/Ti ratios) presented by Nowaczyk et al. (2012), to the oxygen isotope (δ18O) record from Greenland ice cores (NGRIP) based on the GICC05 age model ( Svensson et al., 2008). For MSM33 cores, age models were also achieved by correlating their XRF elementary ratios (mainly Ca/Ti and K/Ti), as proxies for the 'Dansgaard-Oeschger' (D-O) warming events (Dansgaard et al., 1993), to the NGRIP δ18O record. Four intervals of K/Ti ratio peaks and low S-ratios identified in M72/5 and MSM33 cores (Liu et al., 2018) were correlated to the reddish layers related to meltwater events during the decay of the Fennoscandian ice sheet, with AMS 14C ages from about 17 to 15 ka, described from the western Black Sea (Bahr et al. 2006; Soulet et al., 2013). Category: geoscientificInformation Source: Not Available Supplemental Information: Not Availble Coverage: Not Available
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