The influence of particle composition on thorium scavenging in the NE Atlantic ocean (POMME experiment)

²³⁰Th, ²³²Th and ²³⁴Th were analyzed in sinking particles collected by moored and drifting sediment traps in the NE Atlantic Ocean (POMME experiment) in order to constrain the phase(s) carrying Th isotopes in the water column. It reveals a contrasted behaviour between ²³⁴Th and ²³⁰Th. ²³⁴Th is correlated to the particulate organic carbon suggesting that it is primarily scavenged by organic compounds in the surface waters. ²³⁰Th_xs is correlated with Mn, Ba and the lithogenic fraction that are enriched in small suspended particles and incorporated in the sinking particulate flux throughout the water column. The lack of correlation between ²³⁰Th_xs and CaCO₃ or biogenic silica (bSi) indicates that CaCO₃ and bSi are not responsible for ²³⁰Th scavenging in the deep waters of this oceanic region. ²³⁰Th is generally correlated with the lithogenic content of the trapped material but this correlation disappears in winter during strong atmospheric dust inputs suggesting that lithogenic matter is not directly responsible for ²³⁰Th scavenging in the deep waters or that sufficient time is required to achieve particle–solution equilibration. MnO₂ could be the prevalent ²³⁰Th_xs-bearing phase. The narrow range of K_{d_MnO2}^Th obtained for very contrasted oceanic environments supports a global control of ²³⁰Th_xs scavenging by MnO₂ and raises the possibility that the ²³⁰Th–²³¹Pa fractionation is controlled by the amount of colloidal MnO₂ in seawater.     

Temporality of disasters: The politics of women's livelihoods ‘after’ the 2004 tsunami in Sri Lanka

The devastation caused by the 2004 Indian Ocean tsunami in Sri Lanka is represented as a ‘natural disaster’. Yet, the tsunami did not occur in a sociopolitical and historical vacuum. How people responded to the tsunami, the challenges of and attitudes to relocation and post‐tsunami livelihoods, were/are shaped by uneven development, social exclusion and ethnonationalist war. All these responses are embedded in structures of gender, caste, class, and ethnicity. The tsunami, thus, brought to the forefront preexisting inequalities, showing up complexities in the temporality of disasters. Drawn from fieldwork in two coastal areas in the Southern and Eastern provinces, this paper shows how gendered structures within the local political economy influenced the ways that institutional actors as well as the displaced communities and women initially devised livelihood strategies. These reactions show how place matters as much as preexisting gendered political economy conditions and reveal the complex ways in which women continue to mediate and negotiate everyday responses in the aftermath of a ‘natural’ disaster.     

The European Marine Strategy: Contribution and challenges from a Portuguese perspective

The EU Marine Strategy Framework Directive (MSFD) is considered to be the environmental pillar of the EU Integrated Maritime Policy, establishing a framework within which member states must take the necessary measures to achieve, or maintain, good environmental status in their marine waters. This study presents Portugal's contributions to the Directive development, describes the Portuguese institutional framework within the MSFD and, finally, highlights the opportunities and threats to the success of the MSFD implementation in Portugal. The latter entails an analysis of the Directive's long term adequacy in its link to (1) marine spatial planning, (2) climate change and (3) the economic/financial crisis. With one of Europe's largest exclusive economic zones. Portugal's interest in the MSFD is paramount. Efforts towards the approval of the final document were assured during the Portuguese presidency of the European Council of Ministers, in 2007, while chairing a thorough discussion between the Council and the European Parliament. In the Portuguese context, the Directive implementation will rely on the Water Institute as the authoritative entity, which will be responsible for coordinating all necessary efforts at the national level. The success of such process depends on a close cooperation among the institutions involved as well as on how approved measures account for long term issues. In addition, the MSFD implementation must be built on lessons learned within the Water Framework Directive, in order to be successful. Although it poses a methodological challenge to Portugal, the MSFD implementation is expected to contribute significantly to the improvement of coastal/marine conservation and management at the national level.     

Organic matter of the North Atlantic

The areas that we studied in the North Atlantic (53 and 60°N) and in the Labrador Sea in the summer were characterized by a wide variability of the concentrations of dissolved and particulate organic matter and its elemental composition both in the surface and in the deep waters. The concentrations of dissolved and particulate C_org varied within 69–360 μM and 0.7–25.6 μM, respectively; the N_org and P_org contents varied within 1.4–22.2 μM and 0.02–0.86 μM, respectively. The maximal concentrations were registered in the photic layer and in the zones of mixing between the waters of different genesis. The particulate matter contribution to the total organic matter (OM) content varied from 0.5 to 15.4%. The waters of the photic layer contained more particulate C_org than those of the near-bottom layer. The values of the C/N molar ratios from the surface to the bottom over the entire aquatic area surveyed varied 5-to 6-fold; at that, the values of the C/P molar ratios varied more than tenfold. In the most productive waters, the values of the C/N ratios were close to the Redfield ratios (6–10). The values of the C/P molar ratios varied from 160 in the photic layer to 4831 in the deep waters. The pronounced non-uniformity in the spatial distribution of the OM and its elemental composition is caused not only by the penetration of the waters of different origins but also by the changes in the microplankton metabolism under mixing of these waters.     

Reanalysis of seasonal and interannual variability of Black Sea fields for 1993–2012

A retrospective analysis has been done for the hydrophysical fields of the Black Sea for 1993–2012 with the assimilation of undisturbed monthly average profiles of temperature and salinity that were obtained by using an original procedure of joint processing of satellite altimetry and rare hydrological observations. The accuracy of the reconstructed fields of temperature and salinity of the Black Sea is evaluated by comparison with the data of sounding from the hydrological stations and the Argo floats. A comparative analysis is performed for the integral characteristics of the fields of temperature, salinity, and kinetic energy with the same characteristics of the reanalysis for 1992–2012 that assimilated the average annual profiles of temperature and salinity, surface temperature and altimetry level of the sea after being adjusted with respect to climate seasonal variability. The proposed procedure of the reanalysis execution allows a more precise reconstruction of the interannual variability of temperature and salinity stratification in the main pycnocline. The correlation between the annual and seasonal variability of the eddy of the wind friction tangential stress and the average kinetic energy at the levels is revealed.     

Estimation of the deep density distribution in the lithosphere of central and Southern Asia using data about free mantle surface depth

The results of the selection of a model of the deep density distribution in the lithosphere of Central and Southern Asia, which explains the previously revealed dependence of the free mantle surface depth on the thickness of the crust [Artemjev, 1975], are described. It is shown that this dependence can be caused by variations in the mantle’s density with depth. Models of the continental and oceanic mantles with an increase in the linear density over depth are selected for the region of Asia. The level of the free surface depth in the oceanic mantle is higher than in the continental mantle. The observed dependence on the crustal thickness can also be used for determining nonlinear density variations with depth under the assumption that lateral density variations in this dependence are of a random character.     

Variability of sediment diatom assemblages in an upland,wind-stressed lake (Loch Fleet,Galloway, S.W. Scotland)

The variability of diatom distribution in an acidified, upland wind-stressed lake (Loch Fleet, Galloway, S. W. Scotland) was assessed by analysis of 28 surface sediment samples and 11 cores. Correspondence analysis (CA) and cluster analysis were used to illustrate the variability of the surface sediment and core samples. There was reasonable uniformity of taxa in most of the surface sediment samples, although 7 samples, as indicated by both CA and cluster analyses were atypical. Most cores recorded clearly the acidification of the lake, although percentages of individual taxa varied up to 20% between cores. Two cores had old, preacidification diatom assemblages (of indeterminate age) close to the sediment surface. These old sediments were probably the source of the re-worked diatoms found in the atypical surface sediment assemblages. Diatom trends, as CA ordinations and pH profiles, were less variable than the surface sediment assemblages. It is argued that non-uniform sediment accumulation rates and diatom deposition cause variability in surface sediment diatom samples. This variability may be reduced in core profiles by homogenization during further resuspension/deposition cycles and burial. Cores, and the associated time component they offer, may be useful in assessing the variability of surface sediment assemblages.     

Derivation of density and temperature from the Cassini–Huygens CAPS electron spectrometer

In this paper we present two methods to derive electron fluid parameters from the CAPS–ELS spectrometer on board the Cassini spacecraft currently in orbit around Saturn. In the first part of the paper we give a basic overview of the instrument and describe the challenges inherent in the derivation of density and temperature values using these techniques. We then describe a method to calculate electron moments by integrating the particle distribution function. We also describe a second technique in which we fit the electron energy spectrum with a Gaussian curve and use the peak energy of this curve to derive density and temperature values. We then compare the two methods with particular emphasis on their application to Cassini SOI observations in the saturnian environment and point out the limitations of the two techniques. We will show that results from the two very different methods are in agreement when the physical properties of the environment and of the observed electron populations have been inferred from inspection of the raw data. Finally we will suggest future developments that will remove these limitations.     

TropFlux wind stresses over the tropical oceans: evaluation and comparison with other products

In this paper, we present TropFlux wind stresses and evaluate them against observations along with other widely used daily air-sea momentum flux products (NCEP, NCEP2, ERA-I and QuikSCAT). TropFlux wind stresses are computed from the COARE v3.0 algorithm, using bias and amplitude corrected ERA-I input data and an additional climatological gustiness correction. The wind stress products are evaluated against dependent data from the TAO/TRITON, PIRATA and RAMA arrays and independent data from the OceanSITES mooring networks. Wind stress products are more consistent amongst each other than surface heat fluxes, suggesting that 10 m-winds are better constrained than near-surface thermodynamical parameters (2 m-humidity and temperature) and surface downward radiative fluxes. QuikSCAT overestimates wind stresses away from the equator, while NCEP and NCEP2 underestimate wind stresses, especially in the equatorial Pacific. QuikSCAT wind stress quality is strongly affected by rain under the Inter Tropical Convergence Zones. ERA-I and TropFlux display the best agreement with in situ data, with correlations >0.93 and rms-differences <0.012 Nm^?2. TropFlux wind stresses exhibit a small, but consistent improvement (at all timescales and most locations) over ERA-I, with an overall 17 % reduction in root mean square error. ERA-I and TropFlux agree best with long-term mean zonal wind stress observations at equatorial latitudes. All products tend to underestimate the zonal wind stress seasonal cycle by ~20 % in the western and central equatorial Pacific. TropFlux and ERA-I equatorial zonal wind stresses have clearly the best phase agreement with mooring data at intraseasonal and interannual timescales (correlation of ~0.9 versus ~0.8 at best for any other product), with TropFlux correcting the ~13 % underestimation of ERA-I variance at both timescales. For example, TropFlux was the best at reproducing westerly wind bursts that played a key role in the 1997–1998 El Niño onset. Hence, we recommend the use of TropFlux for studies of equatorial ocean dynamics.     

Circumstellar dust and circumstellar extinction curves

We have calculated the circumstellar extinction curves produced by dust grains which absorb and scatter the stellar radiation in the shells of pre-main-sequence stars. A Monte Carlo method was used to model the radiative transfer in non-spherical shells. The dependence on the particle size distribution and the dust shell parameters has been examined.The application of the theoretical results to explain the extinction and polarization of the Herbig Be star HD 45677 shows that the dust shell is not disk-like and that very small grains are absent in it.