Age determination, planktic foraminifera and stable istopes of sediment core MSM05/5_712-2

A sediment core from the West Spitsbergen continental margin was studied to reconstruct climate and paleoceanographic variability during the last ~9 ka in the eastern Fram Strait. Our multiproxy evidence suggests that the establishment of the modern oceanographic configuration in the eastern Fram Strait occurred stepwise, in response to the postglacial sea-level rise and the related onset of modern sea-ice production on the shallow Siberian shelves. The late Early and Mid Holocene interval (9 to 5 ka) was generally characterized by relatively unstable conditions. High abundance of the subpolar planktic foraminifer species Turborotalita quinqueloba implies strong intensity of Atlantic Water (AW) inflow with high productivity and/or high AW temperatures, resulting in a strong heat flux to the Arctic. A series of short-lived cooling events (8.2, 6.9. and 6.1 ka) occurred superimposed on the warm late Early and Mid Holocene conditions. Our proxy data imply that simultaneous to the complete postglacial flooding of Arctic shallow shelves and the initiation of modern sea-ice production, strong advance of polar waters initiated modern oceanographic conditions in the eastern Fram Strait at ~5.2 ka. The Late Holocene was marked by the dominance of the polar planktic foraminifer species Neogloboquadrina pachyderma, a significant expansion of sea ice/icebergs, and strong stratification of the water column. Although planktic foraminiferal assemblages as well as sea surface and subsurface temperatures suggest a return of slightly strengthened advection of subsurface Atlantic Water after 3 ka, a relatively stable cold-water layer prevailed at the sea surface and the study site was probably located within the seasonally fluctuating marginal ice zone during the Neoglacial period.

Visibilidad de los archivos universitarios hispanoamericanos a través de Internet

Este trabajo busca detectar la presencia en Internet de archivos universitarios existentes en países del continente americano cuyo idioma oficial sea la lengua española, y analizar sus sitios web prestando especial atención a los contenidos difundidos en ellos. Se relevaron a junio de 2013 un total de 56 sitios web. Como conclusiones principales pueden señalarse las siguientes: a) se observa un lento incremento en la cantidad de sitios web, pasando de 42 en 2005 a 56 en 2013; b) 52 por ciento corresponden a la fase histórica; c) México es el país con mayor cantidad de archivos; d) 64 por ciento posee sitio web propio; e) 80 por ciento incluye misión del archivo; f) cerca de un 20 por ciento no incluye datos de contacto; g) 74 por ciento señala los servicios ofrecidos; h) 53 por ciento disponen información descriptiva general sobre los fondos custodiados; i) 21 por ciento ofrece la posibilidad de hojear documentos a texto completo; j) 28 por ciento difunde su reglamento y procedimientos de trabajo; k) poco más del 45 por ciento incluye información sobre pautas para el acceso, consulta y reproducción de documentos; l) un bajo porcentaje incluye informaciones adicionales, predominando noticias (39 por ciento) y fotos (18 por ciento), así como legislación archivística (20 por ciento) y recursos archivísticos de interés (27 por ciento); m) en cuanto a las herramientas de la Web 2.0, 18 por ciento posee blog, 16 por ciento canales de RSS, 27 por ciento Facebook y 23 por ciento Twitter

Visibilidad de los archivos universitarios hispanoamericanos a través de Internet

Este trabajo busca detectar la presencia en Internet de archivos universitarios existentes en países del continente americano cuyo idioma oficial sea la lengua española, y analizar sus sitios web prestando especial atención a los contenidos difundidos en ellos. Se relevaron a junio de 2013 un total de 56 sitios web. Como conclusiones principales pueden señalarse las siguientes: a) se observa un lento incremento en la cantidad de sitios web, pasando de 42 en 2005 a 56 en 2013; b) 52 por ciento corresponden a la fase histórica; c) México es el país con mayor cantidad de archivos; d) 64 por ciento posee sitio web propio; e) 80 por ciento incluye misión del archivo; f) cerca de un 20 por ciento no incluye datos de contacto; g) 74 por ciento señala los servicios ofrecidos; h) 53 por ciento disponen información descriptiva general sobre los fondos custodiados; i) 21 por ciento ofrece la posibilidad de hojear documentos a texto completo; j) 28 por ciento difunde su reglamento y procedimientos de trabajo; k) poco más del 45 por ciento incluye información sobre pautas para el acceso, consulta y reproducción de documentos; l) un bajo porcentaje incluye informaciones adicionales, predominando noticias (39 por ciento) y fotos (18 por ciento), así como legislación archivística (20 por ciento) y recursos archivísticos de interés (27 por ciento); m) en cuanto a las herramientas de la Web 2.0, 18 por ciento posee blog, 16 por ciento canales de RSS, 27 por ciento Facebook y 23 por ciento Twitter

(Table 2) Distribution of alkenone unsaturation index UK37 of the eastern North Atlantic

This paper reports the concentrations and within-class distributions of long-chain alkenones and alkyl alkenoates in the surface waters (0-50 m) of the eastern North Atlantic, and correlates their abundance and distribution with those of source organisms and with water temperature and other environmental variables. We collected these samples of >0.8 µm particulate material from the euphotic zone along the JGOFS 20°W longitude transect, from 61°N to 24°N, during seven cruises of the UK-JGOFS Biogeochemical Ocean Flux Study (BOFS) in 1989-1991; the biogeographical range of our 53 samples extends from the cold (<10°C), nutrient-rich and highly productive subarctic waters of the Iceland Basin to the warm (>25°C) oligotrophic subtropical waters off Africa. Surface water concentrations of total alkenone and alkenoates ranged from <50 ng/l in oligotrophic waters below 40°N to 2000-4500 ng/l in high latitude E. huxleyi blooms, and were well correlated with E. huxleyi cell densities, supporting the assumption that E. huxleyi is the predominant source of these compounds in the present day North Atlantic. The within-class distribution of the C37 and C38 alkenones and C36 alkenoates varied strongly as a function of temperature, and was largely unaffected by nutrient concentration, bloom status and other surface water properties. The biosynthetic response of the source organisms to growth temperature differed between the cold (<16°C) waters above 47°N and the warmer waters to the south. In cold (<16°C) waters above 47°N, the relative amounts of alkenoates and C38 alkenones synthesized was a strong function of growth temperature, while the unsaturation ratio of the alkenones (C37 and C38) was uncorrelated with temperature. Conversely, in warm (>16°C) waters below 47°N, the relative proportions of alkenoates and alkenones synthesized remained constant with increasing temperature while the unsaturation ratios of the C37 and C38 methyl alkenones (Uk37 and Uk38Me, respectively) increased linearly. The fitted regressions of Uk37 and Uk38Me versus temperature for waters >16°C were both highly significant (r**2 > 0.96) and had identical slopes (0.057) that were 50% higher than the slope (0.034) of the temperature calibration of Uk37 reported by Prahl and Wakeham (1987; doi:10.1038/330367a0) over the same temperature range. These observations suggest either a physiological adjustment in biochemical response to growth temperature above a 16-17°C threshold and/or variation between different E. huxleyi strains and/or related species inhabiting the cold and warm water regions of the eastern North Atlantic. Using our North Atlantic data set, we have produced multivariate temperature calibrations incorporating all major features of the alkenone and alkenoate data set. Predicted temperatures using multivariate calibrations are largely unbiased, with a standard error of approximately ±1°C over the entire data range. In contrast, simpler calibration models cannot adequately incorporate regional diversity and nonlinear trends with temperature. Our results indicate that calibrations based upon single variables, such as Uk37, can be strongly biased by unknown systematic errors arising from natural variability in the biosynthetic response of the source organisms to growth temperature. Multivariate temperature calibration can be expected to give more precise estimates of Integrated Production Temperatures (IPT) in the sedimentary record over a wider range of paleoenvironmental conditions, when derived using a calibration data set incorporating a similar range of natural variability in biosynthetic response.