Streamflow response to the rapid retreat of a lake‐calving glacier

There has been increasing attention over the last decade to the potential effects of glacier retreat on downstream discharge and aquatic habitat. This study focused on streamflow variability downstream of Bridge Glacier in the southern Coast Mountains of BC between 1979 and 2014, prior to and during a period in which the glacier experienced enhanced calving and rapid retreat across a lake‐filled basin. Here we combined empirical trend detection and a conceptual‐parametric hydrological model to address the following hypotheses: (1) streamflow trends in late summer and early autumn should reflect the opposing influences of climatic warming (which would tend to increase unit‐area meltwater production) and the reduction in glacier area (which would tend to reduce the total volume of meltwater generated), and (2) winter streamflow should increase because of displacement of lake water as ice flows past the grounding line and calves into the lake basin. In relation to the first hypothesis, we found no significant trends in monthly discharge during summer. However, applying regression analysis to account for air temperature and precipitation variations, weak but statistically significant negative trends were detected for August and melt season discharge. The HBV‐EC model was applied using time‐varying glacier cover, as derived from Landsat imagery. Relative to simulations based on constant glacier extent, model results indicated that glacier recession caused a decline in mean monthly streamflow of 9% in August and 11% in September. These declines in late‐summer streamflow are consistent with the results from our empirical analysis. The second hypothesis is supported by the finding of positive trends for December, January, and February discharge. Despite the modelled declines in late‐summer mean monthly streamflow, recorded discharge data exhibited neither positive nor negative trends during the melt season, suggesting that Bridge Glacier may currently be at or close to the point of peak water. Further analysis of the impact of lake‐terminating glaciers on downstream discharge is needed to refine the peak water model. Copyright © 2016 John Wiley & Sons, Ltd.     

In Situ Oxygen Isotope Determination in Serpentine Minerals by SIMS: Addressing Matrix Effects and Providing New Insights on Serpentinisation at Hole BA1B (Samail ophiolite,Oman)

The ability to constrain the petrogenesis of multiple serpentine generations recorded at the microscale is crucial for estimating the extent and conditions of modern versus fossil serpentinisation in ophiolites. To address matrix bias effects during oxygen isotope analysis by SIMS, we present the first investigation analysing antigorite in the compositional range Mg# = 77.5–99.5 mole %, using a CAMECA IMS‐1280 secondary ion mass spectrometer. Spot‐to‐spot homogeneity is ≤ 0.5‰ (2s) for the new antigorite reference materials. The relative bias between antigorite reference materials with different Mg/Fe ratios is described by a second‐order polynomial, and a maximum difference in bias of ~ 1.8‰ was measured for Mg# ~ 78 to 100. We observed a bias up to ~ 1.0‰ between lizardite and antigorite attributed to their different crystal structures. Orientation effects up to ~ 1‰ were observed in chrysotile. The new analytical protocol allowed the identification of oxygen isotope zoning up to ~ 7‰ in serpentine minerals from two serpentinites recovered from an area of active serpentinisation in the Samail ophiolite. Thus, in situ analysis is capable of resolving isotopic heterogeneity that may directly reflect changes in the physical and chemical conditions of multiple serpentinisation events in the Samail ophiolite.     

Excrétion de carbone organique par le phytoplancton lémanique

The release of soluble organic carbon by the phytoplankton in the trophogenic layer of Lake Geneva has been investigated by¹⁴C method from March to November 1984. The carbon excretion rate varied from 0.01 to 0.5 mg C·m⁻³·h⁻¹ and depended primarily upon the rate of its photosynthetic assimilation. The carbon excretion rate varied generally between 2 and 5% of photoassimilated carbon and exceptionally exceeded 6%. These values were underestimated from part of heterotrophic reassimilation. The study of the carbon balance over 24 hours has shown that night excretion represents less than 10% of losses due to respiration. Heterotrophic activity measured by¹⁴C glucose assimilation exhibited seasonal variations following the same general pattern as excretion. The quantity of phytoplankton excretion products appeared to be superior to the needs in organic compounds of heterotrophic organisms in the trophogenic layer.      

Creating a conceptual framework to improve the re‐usability of open geographic data in cities

Open data has a profound effect on the working environment within which information is created and shared at all levels. At the local government level, open data initiatives have resulted in higher transparency in policy, a greater engagement between decision‐makers and citizens, and have changed the culture about how data analysis and evidence are used to support local governance. This article, based on data collected through an on‐line survey, participatory workshops with data user communities in four cities (in Colombia and Spain), and interviews with Valencia good‐government office, identifies four elements for a conceptual framework to improve the re‐usability of open geographic data in cities. The essential elements defined in this research are the definition of data user communities and their needs, the creation of the community of reuse, user‐focused metadata, and reuse‐focused legal terms. The definition of these indicators provides a framework for authorities to re‐shape their current open data strategy to include data user requirements. At the end of this article, a roadmap for future research and implementation is presented, considering some reflections on the conceptual framework.     

On the warm/cold regime shift in the South China Sea: Observation and modeling study

Remote sensing data sets and a high-resolution three-dimensional regional ocean model were utilized to investigate the shifting of warm/cold regime and the associated sea level variation in the South China Sea (SCS) during 2000–2003. Both the altimetry data and the model results showed an increase in the sea level (warm phase) followed by an abrupt decrease (cold phase) in the SCS during 2000–2003. Heat budget calculations performed with the model revealed excess heat advection from the western Pacific warm pool into the SCS during the warm phase than the cold phase. The warm phase, which occurred during La Niña episodes, resulted from the intrusion of abnormally warmer western Pacific water that increased the heat content and thus sea level in the SCS. The cold phase, which occurred during El Niño episodes, was triggered by a reduction in the net atmospheric heat flux followed by cold water advection into the SCS. Decrease in the rate of precipitation minus evaporation (P?E) also accounted for the falling of sea level during cold phase. The present study integrated the available remote sensing data and advanced numerical model to identify the time-dependent three-dimensional dynamic and thermodynamic forcing that are important in governing the warm/cold regime shift in the SCS.     

Sur la chaleur de vaporisation d'une gouttelette de solution en suspension dans l'atmosphère

Résumé Dans ce travail, nous établissons la formule donnant la chaleur de vaporisation d'une gouttelette de solution en suspension dans l'atmosphère et nous montrons dans quels cas elle peut être remplacée par la formule donnant la chaleur de vaporisation de l'eau en masse.

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Summary Our purpose is to establish a formula giving the heat of vaporization of a solution droplet in suspension in the atmosphere. We show in which cases this formula can be replaced by another one giving the heat of vaporization relative to a plane interface.

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Zusammenfassung Es wird die Formel für die Verdampfungswärme eines in der Atmosphäre suspendierten Lösungströpfchens aufgestellt und gezeigt, in welchen Fällen sie durch die Formel der Verdampfungswärme einer ebenen Wasserfläche ersetzt werden kann.

     

A Non-Homogeneous Model for Kriging Dosimetric Data

Mathematical Geosciences - This paper deals with kriging-based interpolation of dosimetric data. Such data typically show some inhomogeneities that are difficult to take into account by means of...     

Lode–gold mineralization in the Tanami region, northern Australia

The Tanami region of northern Australia has emerged over the last two decades as the largest gold-producing region in the Northern Territory. Gold is hosted by epigenetic quartz veins in sedimentary and mafic rocks, and by sulfide-rich replacement zones within iron formation. Although limited, geochronological data suggest that most mineralization occurred at about 1,805–1,790 Ma, during a period of extensive granite intrusion, although structural relationships suggest that some deposits predate this period. There are three main goldfields in the Tanami region: the Dead Bullock Soak goldfield, which hosts the world-class Callie deposit; The Granites goldfield; and the Tanami goldfield. In the Dead Bullock Soak goldfield, deposits are hosted by carbonaceous siltstone and iron formation where a late (D₅) structural corridor intersects an early F₁ anticlinorium. In The Granites goldfield, deposits are hosted by highly sheared iron formation and are interpreted to predate D₅. The Tanami goldfield consists of a large number of small, mostly basalt-hosted deposits that probably formed at a high structural level during D₅. The D₅ structures that host most deposits formed in a convergent structural regime with σ ₁ oriented between E–W and ENE–WSW. Structures active during D₅ include NE-trending oblique thrust (dextral) faults and ESE-trending (sinistral) faults that curve into N- to NNW-trending reverse faults localized in supracrustal belts between and around granite complexes. Granite intrusions also locally perturbed the stress field, possibly localizing structures and deposits. Forward modeling and preliminary interpretations of reflection seismic data indicate that all faults extend into the mid-crust. In areas characterized by the N- to NW-trending faults, orebodies also tend to be N- to NW-trending, localized in dilational jogs or in fractured, competent rock units. In areas characterized by ESE-trending faults, the orebodies and veins tend to strike broadly east at an angle consistent with tensional fractures opened during E–W- to ENE–WSW-directed transpression. Many of these deposits are hosted by reactive rock units such as carbonaceous siltstone and iron formation. Ore deposition occurred at depths ranging from 1.5 to 11 km from generally low to moderate salinity carbonic fluids with temperatures from 200 to 430°C, similar to lode–gold fluids elsewhere in the world. These fluids are interpreted as the product of metamorphic dewatering caused by enhanced heat flow, although it is also possible that the fluids were derived from coeval granites. Lead isotope data suggest that lead in the ore fluids had multiple sources. Hydrogen and oxygen isotope data are consistent with both metamorphic and magmatic origins for ore fluids. Gold deposition is interpreted to be caused by fluid unmixing and sulfidation of host rocks. Fluid unmixing is caused by three different processes: (1) CO₂ unmixing caused by interaction of ore fluids with carbonaceous siltstone; (2) depressurization caused by pressure cycling in shear zones; and (3) boiling as ore fluids move to shallow levels. Deposits in the Tanami region may illustrate the continuum model of lode–gold deposition suggested by Groves (Mineralium Deposita 28:366–374, 1993) for Archean districts.     

Mapping ecosystem services at the regional scale: the validity of an upscaling approach

Mapping ecosystem services (ES) over large scales is important for environmental monitoring but is often prohibitively expensive and difficult. We test a hybrid, low-cost method of mapping ES indicators over large scales in Pará State, Brazil. Four ES indicators (vegetation carbon stocks, biodiversity index, soil chemical quality index and rates of water infiltration into soil) were measured in the field and then summarized spatially for regional land-cover classes derived from satellite imagery. The regionally mapped ES values correlated strongly with independent and local measures of ES. For example, regional estimates of the vegetation carbon stocks are strongly correlated with actual measures derived from field samples and validation data (significant anova test – p-value = 4.51^e?9) and differed on average by only 20 Mg/ha from the field data. Our spatially-nested approach provides reliable and accurate maps of ES at both local and regional scales. Local maps account for the specificities of an area while regional maps provide an accurate generalization of an ES’ state. Such up-scaling methods infuse large-scale ES maps with localized data and enable the estimation of uncertainty of at regional scales. Our approach is first step towards the spatial characterization of ES at large and potentially global scales.     

An innovative artificial fog production device improved in the European project “FOG”

Transport safety is a major goal in the European Union. Low visibility conditions, especially due to fog, increase the risk of major accidents (chain collision). Innovative products have been developed by the automotive industry, including equipment manufacturers, to increase the level of safety of car passengers and drivers. Testing of these products requires the simulation or artificial reproduction of low visibility (fog) conditions with good stability and reproducibility characteristics. We report on the results of the European Union funded “FOG” project to improve road transport safety through fog production in an experimental test chamber located at the Clermont-Ferrand laboratory for research on road safety and visibility. The project developed a prototype of a small-scale climatic chamber, an improved fog production spraying device, a laser-based visibility measurement device, a reduced scale transmissometer, and a combined indoor climate-fog production simulation software. The ability of the fog chamber to test for driver reaction was also investigated. Recent developments include a device able to produce stable visibility levels and homogeneous fog, representative of various types of natural water droplet distribution. The fog characteristics were determined and compared to natural fog. Results are presented for a selection of conditions including stabilized visibility levels for dense fog and two kinds of droplet distributions.