Deglaciation and catchment ontogeny in coastal south‐west Greenland: implications for terrestrial and aquatic carbon cycling

Here we present Holocene organic carbon, nitrogen, sulphur, carbon isotope ratio and macrofossil data from a small freshwater lake near Sisimiut in south‐west Greenland. The lake was formed c. 11 cal ka BP following retreat of the ice sheet margin and is located above the marine limit in this area. The elemental and isotope data suggest a complex deglaciation history of interactions between the lake and its catchment, reflecting glacial retreat and post‐glacial hydrological flushing probably due to periodic melting of local remnant glacial ice and firn areas between 11 and 8.5 cal ka BP. After 8.5 cal ka BP, soil development and associated vegetation processes began to exert a greater control on terrestrial–aquatic carbon cycling. By 5.5 cal ka BP, in the early Neoglacial cooling, the sediment record indicates a change in catchment–lake interactions with consistent δ¹³C while C/N exhibits greater variability. The period after 5.5 cal ka BP is also characterized by higher organic C accumulation in the lake. These changes (total organic carbon, C/N, δ¹³C) are most likely the result of increasing contribution (and burial) of terrestrial organic matter as a result of enhanced soil instability, as indicated by an increase in Cenococcum remains, but also Sphagnum and Empetrum. The impact of glacial retreat and relatively subdued mid‐ to late Holocene climate variation at the coast is in marked contrast to the greater environmental variability seen in inland lakes closer to the present‐day ice sheet margin. Copyright © 2012 John Wiley & Sons, Ltd.     

Validation of ERS scatterometer‐derived soil moisture data in the central part of the Duero Basin,Spain

The objective of this study was to validate the soil moisture data derived from coarse‐resolution active microwave data (50 km) from the ERS scatterometer. The retrieval technique is based on a change detection method coupled with a data‐based modelling approach to account for seasonal vegetation dynamics. The technique is able to derive information about the soil moisture content corresponding to the degree of saturation of the topmost soil layer (∼5 cm). To estimate profile soil moisture contents down to 100 cm depth from the scatterometer data, a simple two‐layer water balance model is used, which generates a red noise‐like soil moisture spectrum. The retrieval technique had been successfully applied in the Ukraine in a previous study. In this paper, the performance of the model in a semi‐arid Mediterranean environment characterized by low annual precipitation (400 mm), hot dry summers and sandy soils is investigated. To this end, field measurements from the REMEDHUS soil moisture station network in the semi‐arid parts of the Duero Basin (Spain) were used. The results reveal a significant coefficient of determination (R² = 0·75) for the averaged 0–100 cm soil moisture profile and a root mean square error (RMSE) of 2·2 vol%. The spatial arrangement of the REMEDHUS soil moisture stations also allowed us to study the influence of the small‐scale variability of soil moisture within the ERS scatterometer footprint. The results show that the small‐scale variability in the study area is modest and can be explained in terms of texture fraction distribution in the soil profiles. Copyright © 2004 John Wiley & Sons, Ltd.     

The potential of point clouds for the analysis of rock kinematics in large slope instabilities: examples from the Swiss Alps: Brinzauls,Pizzo Cengalo and Spitze Stei

Landslides - Lidar measurements and UAV photogrammetry provide high-resolution point clouds well suited for the investigation of slope deformations. Today, however, the information contained in...     

Segmental closure of the Mongol-Okhotsk Ocean: Insight from detrital geochronology in the East Transbaikalia Basin

The Late Paleozoic–Early Mesozoic Mongol-Okhotsk Ocean extended between the Siberian and Amur–North China continents.The timing and modalities of the oceanic closure are widely discussed.It is largely accepted that the ocean closed in a scissor-like manner from southwest to northeast(in modern coordinates),though the timing of this process remains uncertain.Recent studies have shown that both western(West Transbaikalia)and eastern(Dzhagda)parts of the ocean closed almost simultaneously at the Early–Middle Jurassic boundary.However,little information on the key central part of the oceanic suture zone is available.We performed U-Pb(LA-ICP-MS)dating of detrital zircon from wellcharacterized stratigraphic sections of the central part of the Mongol-Okhotsk suture zone.These include the initial marine and final continental sequences of the East Transbaikalia Basin,deposited on the northern Argun-Idemeg terrane basement.We provide new stratigraphic ages for the marine and continental deposits.This revised chronostratigraphy allows assigning an age of~165–155 Ma,to the collisionrelated flexure of the northern Argun-Idemeg terrane and the development of a peripheral foreland basin.This collisional process took place 5 to10 million years later than in the western and eastern parts of the ocean.We demonstrate that the northern Argun-Idemeg terrane was the last block to collide with the Siberian continent,challenging the widely supported scissor-like model of closure of the MongolOkhotsk Ocean.Different segments of the ocean closed independently,depending on the initial shape of the paleo continental margins.     

Lateglacial and Holocene environmental history of the central Kola region,northwestern Russia revealed by a sediment succession from Lake Imandra

Bolshaya Imandra, the northern sub-basin of Lake Imandra, was investigated by a hydro-acoustic survey followed by sediment coring down to the acoustic basement. The sediment record was analysed by a combined physical, biogeochemical, sedimentological, granulometrical and micropalaeontological approach to reconstruct the regional climatic and environmental history. Chronological control was obtained by ¹⁴C dating, ¹³⁷Cs, and Hg markers as well as pollen stratigraphy and revealed that the sediment succession offers the first continuous record spanning the Lateglacial and Holocene for this lake. Following the deglaciation prior to c. 13 200 cal. a BP, the lake's sub-basin initially was occupied by a glacifluvial river system, before a proglacial lake with glaciolacustrine sedimentation established. Rather mild climate, a sparse vegetation cover and successive retreat of the Scandinavian Ice Sheet (SIS) from the lake catchment characterized the Bølling/Allerød interstadial, lasting until 12 710 cal. a BP. During the subsequent Younger Dryas chronozone, until 11 550 cal. a BP, climate cooling led to a decrease in vegetation cover and a re-advance of the SIS. The SIS disappeared from the catchment at the Holocene transition, but small glaciers persisted in the mountains at the eastern lake shore. During the Early Holocene, until 8400 cal. a BP, sedimentation changed from glaciolacustrine to lacustrine and rising temperatures caused the spread of thermophilous vegetation. The Middle Holocene, until 3700 cal. a BP, comprises the regional Holocene Thermal Maximum (8000–4600 cal. a BP) with relatively stable temperatures, denser vegetation cover and absence of mountain glaciers. Reoccurrence of mountain glaciers during the Late Holocene, until 30 cal. a BP, presumably results from a slight cooling and increased humidity. Since c. 30 cal. a BP Lake Imandra has been strongly influenced by human impact, originating in industrial and mining activities. Our results are in overall agreement with vegetation and climate reconstructions in the Kola region.     

The Effect of Heavy Tamping on Structured Residual Clay Site

This paper examines the effect of heavy tamping (dynamic compaction) on highly porous structured residual clayey soil. The aim of this study is to analyse the feasibility of this technique when applied on lightly bonded residual soil sites, which are commonly found in tropical and subtropical regions. This soil has some interesting characteristics, such as high fine grain soil percentages (56% clay and 22% silt), a plastic index of 11%, high porosity (initial void ratio of 1.21), high hydraulic conductivity (about 10^?5 m/s) and a high stiffness at small strains (E?=?49.2-MPa). The research involves field [Cone Penetration Test (CPT) and the dynamic compaction] and laboratory (triaxial tests, characterization and hydraulic conductivity) investigation. According to laboratory tests, the void ratio decreased to 0.96, hydraulic conductivity decreased to 2.8?×?10^?7 m/s, the effective peak friction angle (?′) increased from 30.5° (in natural conditions) to about 35.5°, and the triaxial stiffness at small strains decreased to E?=?20-MPa due to dynamic compaction. CPT results have shown an improved depth in which CPT tip strength (q_t) increased from nearly 650-kPa to an average of 1700-kPa and CPT sleeve friction (f_s) increased from approximately 50-kPa to about 130-kPa. Horizontal displacements were observed up to about 4.0 m of depth (approximately the same depth at which CPT results showed soil improvement). It was concluded that heavy tamping reduces soil voids and substantially increases soil strength, but also breaks soil structure and decreases soil stiffness. It is thus not a suitable ground improvement solution for highly porous structured residual clayey soil.

     

Effects of seed particle size and composition on heterogeneous nucleation of n-nonane

Heterogeneous nucleation of supersaturated n-nonane vapour on seed particles of different size and composition has been investigated using a fast expansion chamber. Monodisperse seed particle sizes were ranging from about 4 nm up to about 24 nm in diameter. By using different types of particle generators WO_x, Ag and (NH₄)₂SO₄ particles were generated. For direct comparison between different particle compositions overlapping sizes have been generated for WO_x and Ag at about 7 nm particle diameter as well as for Ag and (NH₄)₂SO₄ at about 15 nm. Nucleation temperature was kept constant at about 278 K. Experimental data were compared to Kelvin equation and Fletcher theory including the effect of line tension. It was found that heterogeneous nucleation of n-nonane seems to be independent of seed particle composition and starts well below the Kelvin curve. Good agreement was achieved with Fletcher theory including the effect of line tension.     

The role of the Kupferschiefer in the formation of hydrothermal base metal mineralization in the Spessart ore district, Germany: insight from detailed sulfur isotope studies

The Spessart district (SW Germany), located at the southwestern margin of the Permian Kupferschiefer basin in Central Europe, hosts abundant stratabound and structurally controlled base metal mineralization. The mineralization styles identified are (1) stratabound Cu-Pb-Zn-(Ag) ores in Zechstein sedimentary rocks, (2) structurally controlled Cu-As-(Ag) ores in Zechstein sedimentary rocks, (3) crosscutting Co-Ni-(Bi)-As and Cu-Fe-As veins, (4) stratabound metasomatic Fe-Mn carbonate ores in Zechstein dolomite, (5) barren barite veins, and (6) Fe-Mn-As veins in Permian rhyolites. Building on previous work that involved mineralogical, textural, and chemical characterization of the major mineralization types, we have performed a comprehensive sulfur isotope study that applied both conventional and novel laser-ablation multi-collector inductively coupled plasma mass spectrometry techniques. The δ³⁴S values of sulfide minerals from the different ore types are consistently negative and highly variable, in the range between −44.5‰ and −3.9‰, whereas the δ³⁴S values of barite are all positive in the range between 4.7‰ and 18.9‰. Remarkably, stratabound and structurally controlled mineralization in Zechstein sedimentary rocks has the least negative δ³⁴S values, whereas vein-type deposits have consistently more negative δ³⁴S values. The observed pattern of sulfide δ³⁴S values can be best interpreted in terms of fluid mixing at the basement-cover interface. Hydrothermal fluids originating from the crystalline basement migrated upward along subvertical fault zones and were periodically injected into groundwaters that were flowing in the post-Variscan sedimentary cover. These groundwaters had interacted with the Zechstein sedimentary rocks, resulting in fluids characterized by elevated concentrations of reduced sulfur (with negative δ³⁴S values) and alkaline pH. Repeated mixing between both chemically contrasting fluids caused rapid and efficient precipitation of sulfide ore minerals in hydrothermal veins with highly variable but distinctly negative δ³⁴S values.     

Swift observations of CSS081007:030559+054715

CSS081007:030559+054715 was discovered by the Catalina Real‐time Transient Survey. Optical spectroscopy revealed a multi‐peaked Hα emission line profile with radial velocities exceeding 1500 km/s, as well as strong Ne emission, suggestive of a neon nova. We monitored the source extensively with the Swift satellite, obtaining a unique dataset spanning 270 days in the soft X‐ray and UV bands. The data reveal a soft, blackbody‐like spectrum with a temperature around 55 eV (though dependent on the modelling), variable X‐ray and UV light curves with a 1.77 day period in both the X‐ray and UV bands, a longer timescale modulation of ∼ 50 days, followed by a slowly declining trend in the soft X‐ray and UV flux. We highlight the Swift observations and their implications for the SSS nature of this object (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Remotely sensed soil moisture integration in an ecosystem carbon flux model. The spatial implication

While remote sensing is able to provide spatially explicit datasets at regional to global scales, extensive application to date has been found only in the reporting and verification of ecosystem carbon fluxes under the Kyoto Protocol. One of the problems is that new remote sensing datasets can be used only with models or data assimilation schemes adapted to include a data input interface dedicated to the type and format of these remote sensing datasets. In this study, soil water index data (SWI), derived from the ERS scatterometer (10-daily time period with a spatial resolution of 50 km), are integrated into the ecosystem carbon balance model C-Fix to assess 10-daily Net Ecosystem Productivity (NEP) patterns of Europe from the remote sensing perspective on an approximate 1-by-1 km² pixel scale using NDVI-AVHRR data. The modeling performance of NEP obtained with and without the assimilation of remotely sensed soil moisture data in the carbon flux model C-Fix is evaluated with EUROFLUX data. Results show a general decrease of the RRMSE of up to 11 with an average of 3.46. C-Fix is applied at the European scale to demonstrate the potential of this ecosystem carbon flux model, based on remote sensing inputs. More specifically, the strong impact of soil moisture on the European carbon balance in the context of the Kyoto Protocol (anthropogenic carbon emissions) is indicated at the country level. Results suggest that several European countries shift from being a carbon sink (i.e., NEP > 1) to being a carbon source (i.e., NEP < 0) whether or not short-term water availability (i.e., soil moisture) is considered in C-Fix NEP estimations.