Solar irradiance over and under seasonal land-fast sea ice off Barrow, Alaska, in 2010

The amount of solar radiation transmitted through Arctic sea ice is determined by the thickness and physical properties of snow and sea ice. Light transmittance is highly variable in space and time since thickness and physical properties of snow and sea ice are highly heterogeneous on variable time and length scales. We present field measurements of under-ice irradiance along transects under undeformed land-fast sea ice at Barrow, Alaska (March, May, and June 2010). The measurements were performed with a spectral radiometer mounted on a floating under-ice sled. The objective was to quantify the spatial variability of light transmittance through snow and sea ice, and to compare this variability along its seasonal evolution. Along with optical measurements, snow depth, sea ice thickness, and freeboard were recorded, and ice cores were analyzed for chlorophyll a and particulate matter. Our results show that snow cover variability prior to onset of snow melt causes as much relative spatial variability of light transmittance as the contrast of ponded and white ice during summer. Both before and after melt onset, measured transmittances fell in a range from one third to three times the mean value. In addition, we found a twentyfold increase of light transmittance as a result of partial snowmelt, showing the seasonal evolution of transmittance through sea ice far exceeds the spatial variability. However, prior melt onset, light transmittance was time invariant and differences in under-ice irradiance were directly related to the spatial variability of the snow cover.

Particulate and phytoplankton absorption during POLARSTERN cruises ANT-XXVI/3 and ANT-XXVIII/3

The euphotic depth (Zeu) is a key parameter in modelling primary production (PP) using satellite ocean colour. However, evaluations of satellite Zeu products are scarce. The objective of this paper is to investigate existing approaches and sensors to estimate Zeu from satellite and to evaluate how different Zeu products might affect the estimation of PP in the Southern Ocean (SO). Euphotic depth was derived from MODIS and SeaWiFS products of (i) surface chlorophyll-a (Zeu-Chla) and (ii) inherent optical properties (Zeu-IOP). They were compared with in situ measurements of Zeu from different regions of the SO. Both approaches and sensors are robust to retrieve Zeu, although the best results were obtained using the IOP approach and SeaWiFS data, with an average percentage of error (E) of 25.43% and mean absolute error (MAE) of 0.10 m (log scale). Nevertheless, differences in the spatial distribution of Zeu-Chla and Zeu-IOP for both sensors were found as large as 30% over specific regions. These differences were also observed in PP. On average, PP based on Zeu-Chla was 8% higher than PP based on Zeu-IOP, but it was up to 30% higher south of 60°S. Satellite phytoplankton absorption coefficients (aph) derived by the Quasi-Analytical Algorithm at different wavelengths were also validated and the results showed that MODIS aph are generally more robust than SeaWiFS. Thus, MODIS aph should be preferred in PP models based on aph in the SO. Further, we reinforce the importance of investigating the spatial differences between satellite products, which might not be detected by the validation with in situ measurements due to the insufficient amount and uneven distribution of the data.

Procesos de dominación cultural y reproducción de la desigualdad social: La cuestión social tabacalera en Argentina. 16H220

Se trata de describir sintéticamente (máximo 200 palabras) las principales características (tema, metodología, etc.) del proyecto. En este proyecto se investiga cómo se imbrican mutuamente la cultura y la economía en la constitución de la vida social de los productores tabacaleros en Argentina. Se estudia cómo se construyen y se van configurando históricamente los procesos de dominación cultural, en relación con la producción y reproducción de la desigualdad social. El interrogante central que se intenta responder es el siguiente: Si los procesos culturales son constitutivos de la vida social, ¿cómo operan en situaciones históricas de reproducción de la desigualdad social? Desde el postestructuralismo cultural, se conciben los procesos culturales como disputas por los símbolos, significados y categorías sociales claves. Estas disputas implican ideología, institucionalización y hegemonía. Desde esta perspectiva, la desigualdad material no se genera ni se sostiene sólo desde lo político-económico, sino también desde lo simbólico-ideológicocultural. Estas dos dimensiones son constitutivas de la cuestión social tabacalera en Argentina. Se utilizan métodos de investigación etnográficos y biográficos. Las unidades de estudio son las provincias de Jujuy y Misiones y las unidades de análisis las familias productoras de tabaco. Se utilizan relatos autobiográficos, historias de vida y análisis de documentos e información archivada.

Cloride and bromide concentrations and Br-/Cl- molar ratios in pore fluids at ODP Site 134-833

Other than halite diagenesis and organic matter degradation, Cl- and Br- are considered to be conservative in marine pore fluids. Consequently, Br-/Cl- ratios should remain constant during most diagenetic reactions. Nonetheless, Br-/Cl- molar ratios decrease to 0.00127 (~18% less than seawater value) in pore fluids from Site 833 in the Aoba Basin of the New Hebrides convergent margin despite the lack of halite diagenesis and little organic matter. Sediment at this site is largely volcanic ash, which becomes hydrated with depth as it converts to clay and zeolite minerals. These hydration reactions remove sufficient water to increase the concentrations of most solutes including Cl- and Br-. The resulting concentration gradients drive diffusion, but calculations indicate that diffusion does not decrease the Br-/Cl- ratio. Some Cl- may be leached from the ash, but insufficient amounts are available to cause the observed decrease in Br-/Cl- ratio. The limited source of Cl- suggests that proportionately more Br- than Cl- is lost from the fluids to the diagenetic solids. Similar nonconservative behavior of Cl- and Br- may occur during fluid circulation at ridge crests and flanks, thereby influencing the halide distribution in the crust.

Declaración pública por el derecho a la salud de las mujeres por la interrupción legal del embarazo por razones terapéuticas en Chile

MILES–Chile en este 28 de septiembre, Día por la Despenalización del Aborto en América Latina y el Caribe, hace un llamado urgente a la sociedad chilena como un imperativo humanitario velar por la salud de las mujeres. No se trata de imponer sino de que las mujeres y sus más cercanos tengan la posibilidad de optar frente a circunstancias tan difíciles como un problema grave de salud, una inviabilidad fetal y en caso de violación