Increased Precipitation in the Norwegian Arctic: True or False?

Results from the WMO Solid Precipitation MeasurementIntercomparison and parallel precipitationmeasurements from Svalbard are used to evaluate andadjust models for estimating true precipitation underArctic conditions. The conclusion is that trueprecipitation in the Arctic may be estimatedreasonably well when the wind speed at gauge height isless than 7 m/s. It is possible to give good estimatesof true annual and seasonal precipitation at Svalbard,as only a small part of the precipitation is fallingat wind speeds above 7 m/s. For rough calculations,the correction factors for liquid precipitation isestimated to be 1.15 and for solid precipitation1.85.The developed correction models are used to estimateamounts and trends of true precipitation for two sitesin the Norwegian Arctic. In Ny-Ålesund the trueannual precipitation is more than 50% higher than themeasured amount. As the aerodynamic effects leading toprecipitation undercatch are dependent onprecipitation type and temperature, the observed andprojected increase in the air temperature in theArctic would also affect the measured precipitation,even if the true precipitation was unchanged. Sincethe mid 1960s the temperature at Svalbard Airport hasincreased by 0.5 °C per decade, resulting in areduced fraction of annual precipitation falling assnow. In the same period, the measured precipitationhas increased by 2.9% per decade and the `true' by1.7% per decade. Estimates are made of the fictitiousprecipitation increase that would result from ageneral temperature increase of 2, 4 and 6 °C. The increase in the measured annual precipitationwould be 6, 10 and 13%, respectively. The expectedfictitious precipitation increase is thus of the samemagnitude as the real precipitation increase whichaccording to recent GCM projections may be expected inNorthern Europe as a result of a doubling of theatmospheric CO₂ content.     

13C/12C ratio double cyclicity in a Miocene browncoal: isotopic signals and orbital forcing

A detailed stable carbon isotopic profile of a late Miocene browncoal seam from the Lower Rhine Embayment, Germany, reveals two clear separate cycles of different frequency: this is the first instance of this type of isotopic signature being recognized within coals. The ratio of the two frequencies suggests this isotopic signal possibly resulted from climatic or vegetational responses to orbital forcing. The cyclicity has been enhanced by the application of conventional filtering methods on the data set. An analysis of the seam's palynology indicates a correlation between heavier isotopic compositions and the presence of Sequoiapollenites polyformosus , whose parent plant is believed to have favoured moist climates and higher groundwater tables.     

Ecological consequences of land use change: Forest structure and regeneration across the forest-grassland ecotone in mountain pastures in Nepal

The ecotone, the spatial transition zone between two vegetation communities, is claimed to have more species than the adjoining communities. However, empirical studies do not always confirm higher richness at the ecotone. The ecotone position and structure are dynamic over time and space and it is driven by the changes in climate, land use or their interaction. In this context, we assessed the forest- grassland ecotone of temperate mountains in central Nepal by i） comparing species composition and richness across the ecotone, ii） analyzing if the forestgrassland ecotone is shifting towards the grassland center by colonizing them with trees, and iii） discussing the consequence of changed disturbance regime in the dynamics of this ecotone and the surrounding grasslands. We analyzed vegetation data sampled from belt transects laid across the forest- grassland ecotone in semi-natural grassland patches. Vegetation data consisting of species richness and composition, and size structure and regeneration of the two most dominant tree species, namely Rhododendron arboreum and Abies spectabilis, from the transects, were used to analyze the trend of the forest-grassland ecotone. Forest and grasslands were different in terms of floristic composition and diversity. Vascular plant speciesrichness linearly increased while moving from forest interior to grassland center. Spatial pattern of tree size structure and regeneration infers that forest boundary is advancing towards the grasslands at the expense of the grassland area, and tree establishment in the grasslands is part of a suceessional process. Temporally, tree establishment in grasslands started following the gradual decline in disturbance. We argue that local processes in terms of changed land use may best explain the phenomenon of ecotone shift and consequent forest expansion in these grasslands. We underpin the need for further research on the mechanism, rate and spatial extent of ecotone shift by using advaneed tools to understand the process indepth.     

Trace element modelling of pelite-derived granites

The presence or absence of a vapour phase during incongruent-melt reactions of muscovite and biotite together with the composition of the protolith determines the trace-element characteristics of the resulting melt, provided that equilibrium melting occurs for those phases that host the tracc elements of interest. For granitic melts, Rb, Sr and Ba provide critical constraints on the conditions that prevailed during melting, whereas REE are primarily controlled by accessory phase behaviour. Mass-balance constraints for eutectic granites that are formed by the incongruent melting of muscovite in pelites indicate that melting in the presence of a vapour phase will result in a large melt fraction, and deplete the restite in feldspar. Hence the melt will be characterized by low Rb/Sr and high Sr/Ba ratios. In contrast, vapour-absent melting will result in a smaller melt fraction, and an increase in the restitic feldspar. Consequently high Rb/Sr and low Sr/Ba ratios are predicted. Vapour-absent melting will also enhance the negative Eu anomaly in the melt. Granites that result from the incongruent melting of biotite in the source will be characterized by higher Rb concentrations than those that result from the incongruent melting of muscovite. The Himalayan leucogranites provide an example of unfractionated, crustally derived eutectic melts that are enriched in Rb but depleted in Sr and Ba relative to their metasedimentary protoliths. These compositions may be generated by the incongruent melting of muscovite as a low melt fraction (F0.1) from a pelitic source under vapour-absent conditions.     

A Younger Dryas Ash Bed in western Norway,and its possible correlations with tephra in cores from the Norwegian Sea and the North Atlantic

A bed of volcanic ash up to 23 cm thick is found in lacustrine and marine sediments in western Norway. It is formally mamed the Vedde Ash Bed, and its age is approximately 10,600 yr B.P., i.e., mid-Younger Dryas. The bed consits of pure glass having a bimodal basaltic and rhyolitic somposition. The geochemistry of the glass shards suggests an Icelandic source. By means of stratigraphic position and geochemistry, the ash is correlated with ash zones found in cores from the continental shelf, the Norwegian Sea, and the North Atlatic.     

Late Quaternary sediments and stratigraphy on the continental shelf off Troms and west Finnmark, northern Norway

Lithologic, paleontologic, and chronostratigraphic investigation of 13 gravity cores indicates the following environmental evolution: a high- (mid-) arctic period with a slight influx of ice-rafted debris occurred during the early middle Weichselian followed by a mid- (high-) arctic environment with a high influx of iceberg-rafted debris during the remainder of the middle Weichselian. The continental ice sheet probably did not extend beyond the inner shelf during middle Weichselian and a minimum relative sea level was ca. −120 m. A low-arctic environment occurred during (parts of) the late Weichselian with an initial winnowing of the sediments. The Norwegian Current entered the area during this substage. A high- (mid-) boreal environment occurred during the Holocene with high winnowing activity in the early Holocene. Winnowing is still very active on the shallower banks in contrast to the deeper banks where it has ceased. Relatively high percentages of carbonate in the form of biogenic skeletal remains occur in the Holocene sediments.     

The proximity of sexual violence to schools: evidence from a township in South Africa

GeoJournal - Schools are unique places that greatly influence the daily lives of learners. Examining any factors that may be contributing to school absenteeism and dropout rates is vital as gaining...     

Twenty of the most thermophilous vascular plant species in Svalbard and their conservation state

An aim for conservation in Norway is preserving the Svalbard archipelago as one of the least disturbed areas in the Arctic. Information on local distribution, population sizes and ecology is summarized for 20 thermophilous vascular plant species. The need for conservation of northern, marginal populations in Svalbard is reviewed, using World Conservation Union categories and criteria at a regional scale. Thirteen species reach their northernmost distribution in Svalbard, the remaining seven in the western Arctic. Nine species have 1-8 populations in Svalbard and are assigned to Red List categories endangered or critically endangered: Campanula rotundifolia, Euphrasia frigida, Juncus castaneus, Kobresia simpliciuscula, Rubus chamaemorus, Alchemilla glomerulans, Ranunculus wilanderi, Salix lanata and Vaccinium uliginosum , the last four species needing immediate protective measures. Five species are classified as vulnerable: Betula nana, Carex marina ssp. pseudolagopina, Luzula wahlenbergii, Ranunculus arcticus and Ranunculus pallasii . Six species are considered at lower risk: Calamagrostis stricta, Empetrum nigrum ssp. hermaphroditum, Hippuris vulgaris (only occurring on Bjørnøya), Juncus triglumis, Ranunculus lapponicus and Rhodiola rosea . The warmer Inner Arctic Fjord Zone of Spitsbergen supports most of the 20 target species and is of particular importance for conservation. Endangered or vulnerable species were found in a variety of edaphic conditions; thus, several kinds of habitats need protection.     

Cretaceous plutonism in Central Tibet: an example of post-collision magmatism?

The magmatic province of the northern Lhasa Terrane includes an Early Cretaceous (120–130 Ma) plutonic event, and a Late Cretaceous (80–110 Ma) volcanic event. The plutonic association constitutes an older suite of granodiorites, monzogranites and tonalites and a younger peraluminous leucogranite facies. Plutonism occurred about 20 Ma after obduction of the Banggong ophiolite, following closure between the Lhasa and Qiantang Terranes.The earlier suite is of broadly calc-alkaline in composition but differs from arc-related magmas in that only more evolved compositions are represented (SiO₂ > 58%) and Rb/Zr ratios are elevated relative to the Gangdese batholith to the south. Trace-element and isotopic constraints are consistent with derivation from a Late Proterozoic amphibole-bearing crustal source requiring temperatures > 950°C during anatexis. The leucogranites require a pelitic source which is tentatively identified as the Nyaingentanglha basement exposed south of the plutonic province. Unlike the High Himalaya leucogranites, trace elements and field relations require a high degree of melting at source (> 50%) suggesting fluid-absent melting at temperatures > 850°C. Such high crustal temperatures indicate convective heat transfer from the mantle.Thermal constraints together with a tectonic setting of post-emplacement uplift followed by a marine transgression in the northern Lhasa Terrane can not be reconciled with a model of tectonically thickened crust but are consistent with post-collision attenuation of the lithosphere.