Development of a hydrodynamic model of the Bay of Biscay. Validation of hydrology

The hydrology of the Bay of Biscay was investigated using the regional ocean model MARS3D (Model for Application at Regional Scale). The simulated hydrology is compared to a set of various data encompassing monthly climatology, remote sensing SST, CTD casts, and coastal salinity measurements. Special focus was put on the validation over the continental shelf. This paper reports that despite some misfits, the climatological hydrology and its seasonal variability are correctly simulated. Various statistics computed over the period from 1999–2004 highlight different aspects of the hydrology. The biases and root mean square errors (RMSE) remain very weak at all depths when comparing salinity (<0.1 and <0.6 psu respectively). The predicted temperature shows a global overestimation of temperature (bias of around 0.8 °C) and the maximum errors are located near the thermocline (rmse of 1 °C at 20–40 m). The model is shown to properly reproduce the annual dynamics of sea surface temperature, as well as the dynamics of large river plumes observed by high frequency time series from coastal salinity gauges. The misfits highlighted by these various comparisons between model and observations are attributed to heat fluxes and mixing parameterisation.     

Magnetic fields in methanol maser condensations based on data for related regions. Seven sources: Astrophysical parameters

The astrophysical parameters of seven OH maser condensations are estimated based on magnetic fields obtained from polarization observations carried out on the Nan cay Radio Telescope (France) in the 1665 and 1667 MHz lines in four Stokes parameters. Regions in the studied sources containing the observed clusters of maser condensations, as well as clusters of Class I and II methanol masers, have been identified. The associations of the masers are real; i.e., the magnetic field in the clusters can also extend to groups of methanol masers. The linear dimensions of these associations have been found. The ratio of the mass to the magnetic flux, ratio of the thermal to the magnetic pressure, and virial relationships between energies (kinetic, magnetic, and gravitational) in the regions containing the OH andmethanol masers have been obtained. In sources whose magnetic fields have been determined fairly reliably, the ratio of the mass to the magnetic flux exceeds a critical value, and the energies of chaotic motions and of the magnetic field are considerably smaller than the gravitational binding energy. On the other hand, in all cases, the ratio of the thermal to the magnetic pressure is <1, suggesting that the clouds may be in amagnetically dominated regime. This inconsistency is related to probable uncertainties in the the magnetic field values and the estimated distances to the sources, which may lead to overestimation of the sizes of the regions studied.     

Calcium,Na, K and Mg Concentrations in Seawater by Inductively Coupled Plasma‐Atomic Emission Spectrometry: Applications to IAPSO Seawater Reference Material,Hydrothermal Fluids and Synthetic Seawater Solutions

We report a measurement procedure to determine simultaneously the major cation concentrations (Na, Ca, K and Mg) of seawater‐derived solutions by inductively coupled plasma‐atomic emission spectrometry. The best results were obtained when the IAPSO (‘standard’) seawater reference material was diluted by thirty times with Milli‐Q^® water. We obtained an average reference value r_K (the ratio of the mass fraction of potassium to that of chlorine, i.e., (g kg^?1)/(g kg^?1)) for IAPSO seawater of 0.0205 ± 0.0006 (2.9% RSD), not significantly different from 0.0206 ± 0.0005 (2.4% RSD) for seawater composition reported in the literature. The measured Na, Ca and Mg concentrations correspond to r_Na, r_Ca and r_Mg values of 0.5406 ± 0.0026 (0.5% RSD), 0.02192 ± 0.00048 (2.2% RSD) and 0.06830 ± 0.00047 (0.7% RSD), respectively, in line with previous values measured by wet‐chemistry and atomic absorption spectrophotometry or wet‐chemical titration. Our measurement procedure was used successfully on synthetic seawater solutions and high‐temperature hydrothermal fluids.     

Contribution of climatic and anthropogenic effects to the hydric deficit of peatlands

The present study makes use of a detailed water balance to investigate the hydrological status of a peatland with a basal clay‐rich layer overlying an aquifer exploited for drinking water. The aim is to determine the influence of climate and groundwater extraction on the water balance and water levels in the peatland. During the two‐year period of monitoring, the hydrological functioning of the wetland showed a hydric deficit, associated with a permanent unsaturated layer and a deep water table. At the same time, a stream was observed serving as a recharge inflow instead of draining the peatland, as usually described in natural systems. Such conditions are not favourable for peat accumulation. Field investigations show that the clay layer has a high hydraulic conductivity (from 1·10^?7 to 3·10^?9 m.s^?1) and does not form a hydraulic barrier. Moreover, the vertical hydraulic gradients are downward between the peat and the sand aquifer, leading to high flows of groundwater through the clay layer (20–48% of the precipitation). The observed hydric deficit of the peatland results from a combination of dry climatic conditions during the study period and groundwater extraction. The climatic effect is mainly expressed through drying out of the peatland, while the anthropogenic effect leads to an enhancement of the climatic effect on a global scale, and a modification of fluxes at a local scale. The drying out of the peatland can lead to its mineralisation, which thus gives rise to environmental impacts. The protection of such wetlands in the context of climate change should take account of anthropogenic pressures by considering the wetland‐aquifer interaction. Copyright © 2011 John Wiley & Sons, Ltd.     

Storm waves in Canadian waters: A major marine hazard

Abstract

In this paper, an overview of storm waves associated with intense weather systems affecting the east and west coasts of Canada is presented. The paper presents the wave climatology of the east and west coasts in terms of the 100‐year significant and maximum wave heights and further analyses the directional distribution of wave heights at selected locations in the Canadian east and west coasts offshore. The paper also analyses wave hazards associated with storm waves in the Beaufort Sea as well as the Canadian Great Lakes region. A section on ocean wave modelling provides a brief history of the development of ocean surface wave models and its present status. The paper further considers the impact of climate change scenarios on wave hazards and finally examines mitigation measures in terms of wave products available from operational wave models and related wave climatology.     

Evolution of the Parisian urban climate under a global changing climate

The evolution of the Parisian urban climate under a changing climate is analyzed from long-term offline numerical integrations including a specific urban parameterization. This system is forced by meteorological conditions based on present-climate reanalyses (1970–2007), and climate projections (2071–2099) provided by global climate model simulations following two emission scenarios (A1B and A2). This study aims at quantifying the impact of climate change on air temperature within the city and in the surroundings. A systematic increase of 2-meter air temperature is found. In average according to the two scenarios, it reaches +?2.0/2.4°C in winter and +?3.5/5.0°C in summer for the minimum and maximum daily temperatures, respectively. During summer, the warming trend is more pronounced in the surrounding countryside than in Paris and suburbs due to the soil dryness. As a result, a substantial decrease of the strong urban heat islands is noted at nighttime, and numerous events with negative urban heat islands appear at daytime. Finally, a 30% decrease of the heating degree days is quantified in winter between present and future climates. Inversely, the summertime cooling degree days significantly increase in future climate whereas they are negligible in present climate. However, in terms of accumulated degree days, the increase of the demand in cooling remains smaller than the decrease of the demand in heating.     

Impact of justice and solidarity variables on the acceptability of managed realignment

Sea-level rise due to climate change will have significant effects on coastal areas and populations. Adaptation policies recommend the managed realignment of the most vulnerable assets and activities. Despite their medium- and long-term benefits, these policies face significant friction due to social acceptability in the communities where they are implemented.

This article investigates the hypothesis that respecting principles of justice in the implementation of managed realignment should increase its acceptability. We compare preferences of those people who are exposed to the risk of climate-change-induced flooding and those who are not, as regards funding managed retreat policies and defining compensation criteria for assets at risk. The main theories of social justice provide the four principles included in the analysis: efficiency, need, responsibility and priority assigned to property rights.

A choice experiment survey was conducted with 258 residents of coastal and hinterland communities in the south of France. Four attributes were selected to define the managed realignment policy: the dialogue arrangements, the implementation period, the policy implementation schedule and the cost. The results show support for a relatively fast launch of these policies (within 15 years) but in stages and through a process of dialogue with the population. People's perceptions of the funding criteria reveal a preference for national solidarity. Finally, national funding of managed retreat policies and compensation criteria based on market prices have a significant positive influence on the acceptability of managed realignment policies, whereas introducing responsibility-based compensation criteria tends to favour the status quo over the adaptation policy.

Policy relevance

Prioritization of the funding criteria reveals the preference for national solidarity. Preferences for the justice criteria underpinning compensation reveal a great diversity of values. Besides implantation modalities, preferences for managed realignment policies depend on which level they are implemented at, on the expropriation criteria (the emphasis given to property rights, i.e. market price), on the attachment (people perceived as worst off, i.e. the property is their main residence rather than a second home or they have lower levels of income) and on the degree of responsibility (related to the date of purchase, i.e. on the information given at the time on the risk).     

The brightest OH maser in the sky: A flare of emission in W75 N

A flare of maser radio emission in the 1665-MHz OH line with a flux density of about 1000 Jy was discovered in the star-forming region W75 N in 2003. At the time of its observations, it was the strongest OH maser in the entire history of research since the discovery of cosmic OH masers in 1965. The linear polarization of the flare emission reached 100%. A weaker flare with a flux density of 145 Jy was observed in this source in 2000–2001; this was probably a precursor of the intense flare. The intensity of two other spectral features decreased when the flare emerged. This change in the intensity of the emission from maser condensations (a brightening of some of them and a weakening of others) can be explained by the passage of a magnetohydrodynamic shock through regions of enhanced gas concentration.