Signal and distribution of volatile Mercury (Hg0) in the Marine High Arctic During Polar Summer in the Sequel of Enhanced Atmospheric Deposition of HgⅡ

1 Introduction It has been elucidated that high levels of neurotoxic mercury (Hg) in the Arctic is related to a rapid, near-compete depletion of Hg0 (MDE) in the atmospheric boundary-layer occurring episodically during the Polar spring[1].     

Radio continuum surveys

The Rhodes University radio astronomy group has been involved in radio continuum mapping of southern extended radio sources since 1976. We describe the various mapping projects undertaken with the HartRAO telescope, particularly the Rhodes/HartRAO 2300 MHz all-sky survey, and speculate on future projects.     

The Alpine Seed Conservation and Research Network–a new initiative to conserve valuable plant species in the European Alps

Safeguarding plants as seeds in ex situ collections is a cost effective element in an integrated plant conservation approach. The European Alps are a regional centre of plant diversity. Six institutions have established a regional network covering the European Alps which will conserve at least 500 priority plant species and which will improve the conservation status of plant species in grassland communities in the subalpine, alpine and nival altitudinal belts. Targeted research will expand the knowledge of the ecology of target species. Public engagement activities will raise the awareness for the importance of specific conservation actions in the European Alps.     

High‐resolution diatom δ18O records,from the last 150 years,reflecting changes in amount of winter precipitation in two sub‐Arctic high‐altitude lakes in the Swedish Scandes

Waters from high‐altitude alpine lakes are mainly recharged by meteoric water. Because of seasonal variations in precipitation and temperature and relatively short hydraulic residence times, most high‐altitude lakes have lake water isotopic compositions (δ¹⁸O_lake) that fluctuate due to seasonality in water balance processes. Input from snowmelt, in particular, has a significant role in determining lake water δ¹⁸O. Here we compare two high‐resolution δ¹⁸O_diatom records from lake sediments in the Swedish Scandes with instrumental data from the last century obtained from nearby meteorological stations. The time period AD 1900–1990 is characterised by an increase in winter precipitation and high winter/summer precipitation ratios and this is recorded in δ¹⁸O_diatom as decreasing trends. Lowest δ¹⁸O_diatom values and highest amount of winter precipitation are found around AD 1990 when the winter North Atlantic Oscillation index was above +2. We conclude that for the last 150 a the main factor affecting the δ¹⁸O_diatom signal in these sub‐Arctic high‐altitude lakes with short residence times has been changes in amount of winter precipitation and that δ¹⁸O_diatom derived from high‐altitude lakes in the Swedish Scandes can be used as a winter precipitation proxy. Copyright © 2010 John Wiley & Sons, Ltd.     

The Langeland Fault System unravelled: Quaternary fault reactivation along an elevated basement block between the North German and Norwegian–Danish basins

The reactivation of faults and possible impact on barrier integrity marks a critical aspect for investigations on subsurface usage capabilities. Glacial isostatic adjustments, originating from repeated Quaternary glaciations of northern Europe, cause tectonic stresses on pre-existing fault systems and structural elements of the North German and Norwegian–Danish basins. Notably, our current understanding of the dynamics and scales of glacially induced fault reactivation is rather limited. A high-resolution 2D seismic data set recently acquired offshore northeastern Langeland Island allows the investigation of a fault and graben system termed the Langeland Fault System. Seismo-stratigraphic interpretation of reflection seismic data in combination with diffraction imaging unravels the spatial character of the Langeland Fault System along an elevated basement block of the Ringkøbing–Fyn High. In combination with sediment echosounder data, the data set helps to visualize the continuation of deep-rooted faults up to the sea floor. Initial Mesozoic faulting occurred during the Triassic. Late Cretaceous inversion reactivated a basement fault flanking the southern border of the elevated basement block of the Ringkøbing–Fyn High while inversion is absent in the Langeland Fault System. Here, normal faulting occurred in the Maastrichtian–Danian. We show that a glacial or postglacial fault reactivation occurred within the Langeland Fault System, as evident by the propagation of the faults from the deeper subsurface up to the sea floor, dissecting glacial and postglacial successions. Our findings suggest that the Langeland Fault System was reactivated over a length scale of a minimum of 8.5 km. We discuss the causes for this Quaternary fault reactivations in the context of glacially induced faulting and the present-day stress field. The combination of imaging techniques with different penetration depths and vertical resolution used in this study is rarely realized in the hinterland. It can therefore be speculated that many more inherited, deep-rooted faults were reactivated in Pleistocene glaciated regions.     

The influence of cloud structure and droplet concentration on the reflectance of shortwave radiation

The effects of cloud shadowing, channelling, cloud side illumination and droplet concentration are investigated with regard to the reflection of shortwave solar radiation. Using simple geometric clouds, coupled with a Monte Carlo model the transmission properties of idealized cloud layers are found. The clouds are illuminated with direct solar radiation from above. The main conclusion reached is that the distribution of the cloud has a very large influence on the reflectivity of a cloud layer. In particular, if the cloud contains vertical gaps through the cloud layer in which the liquid water content is zero, then, smaller more numerous gaps are more influential on the radiation than fewer, larger gaps with equal cloud fraction. At very low solar zenith angles channelling of the radiation reduces the reflection expected on the basis of the percentage cloud cover. At high solar zenith angles the illumination of the cloud edges significantly increases the reflection despite the shadowing of one cloud by another when the width of the gaps is small. The impact of droplet concentration upon the reflection of cloud layers is also investigated. It is found that at low solar zenith angles where channelling is important, the lower concentrations increase the transmission. Conversely, when cloud edge illumination is dominant the cloud distribution is found to be more important for the higher concentrations.     

Estimating the snow water equivalent from snow depth measurements in the Swiss Alps

The snow water equivalent (SWE) characterizes the hydrological significance of snow cover. However, measuring SWE is time-consuming, thus alternative methods of determining SWE may be useful. SWE can be calculated from snow depth if the bulk snow density is known. Thus, a reliable estimation method of snow densities could (a) potentially save a lot of effort by, at least partly, sampling snow depth instead of SWE, and would (b) allow snow hydrological evaluations, when only snow depth data are available. To generate a useful parameterization of the bulk density a large dataset was analyzed covering snow densities and depths measured biweekly over five decades at 37 sites throughout the Swiss Alps. Four factors were identified to affect the bulk snow density: season, snow depth, site altitude, and site location. These factors constitute a convenient set of input variables for a snow density model developed in this study. The accuracy of estimating SWE using our model is shown to be equivalent to the variability of repeated SWE measurements at one site. The technique may therefore allow a more efficient but indirect sampling of the SWE without necessarily affecting the data quality.     

Be exposure dating of river terraces at the southern mountain front of the Dzungarian Alatau (SE Kazakhstan) reveals rate of thrust faulting over the past ~ 400 ka

The mountain belts of the Dzungarian Alatau (SE Kazakhstan) and the Tien Shan are part of the actively deforming India–Asia collision zone but how the strain is partitioned on individual faults remains poorly known. Here we use terrace mapping, topographic profiling, and ¹⁰Be exposure dating to constrain the slip rate of the 160-km-long Usek thrust fault, which defines the southern front of the Dzungarian Alatau. In the eastern part of the fault, where the Usek River has formed five terraces (T₁–T₅), the Usek thrust fault has vertically displaced terrace T₄ by 132 ± 10 m. At two sites on T₄, exposure dating of boulders, amalgamated quartz pebbles, and sand from a depth profile yielded ¹⁰Be ages of 366 ± 60 ka and 360 ^+ 77/_− 48 ka (both calculated for an erosion rate of 0.5 mm/ka). Combined with the vertical offset and a 45–70° dip of the Usek fault, these age constraints result in vertical and horizontal slip rates of ~ 0.4 and ~ 0.25 mm/a, respectively. These rates are below the current resolution of GPS measurements and highlight the importance of determining slip rates for individual faults by dating deformed landforms to resolve the pattern of strain distribution across intracontinental mountain belts.     

Isotope geochemistry and modelling of the multi-aquifer system in the eastern part of Lithuania

A steady-state groundwater flow model of three Quaternary intertill aquifers in the eastern part of Lithuania has been compiled. The distinction of separate modelled layers is based on hydraulic and isotope-hydrochemistry data criteria. ³H data were used to estimate the corrected groundwater age and were coupled with a groundwater-flow-dynamics model of the Quaternary aquifer system along a cross-section flow pathway from the Baltic Upland recharge area in eastern Lithuania towards the discharge area in the lowlands near the city of Kaunas in central Lithuania. The bicarbonate content in groundwater (214–462 mg/l) increases downgradient towards the lowland area. The other major constituents and total dissolved solids (TDS) have a trend analogous to the bicarbonate. The ¹⁴C activity of dissolved inorganic carbon (DIC) in the groundwater ranges from 41.4 to 85.7 pMC. With aquifer-system depth, active precipitation of aqueous solution takes place by dissolving minerals of calcite and dolomite and leakage of “old” groundwater from lower aquifers; the process is also traced by lower ¹⁴C and ³H activities and by more positive δ¹⁸O values in lowland areas.