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The Atlantic-Mediterranean exchange of water at Gibraltar represents a significant heat and freshwater sink for the North Atlantic and is a major control on the heat, salt and freshwater budgets of the Mediterranean Sea. Consequently, an understanding of the response of the exchange system to external changes is vital to a full comprehension of the hydrographic responses in both ocean basins. Here, we use a synthesis of empirical (oxygen isotope, planktonic foraminiferal assemblage) and modeling (analytical and general circulation) approaches to investigate the response of the Gibraltar Exchange system to Atlantic freshening during Heinrich Stadials (HSs). HSs display relatively flat W-E surface hydrographic gradients more comparable to the Late Holocene than the Last Glacial Maximum. This is significant, as it implies a similar state of surface circulation during these periods and a different state during the Last Glacial Maximum. During HS1, the gradient may have collapsed altogether, implying very strong water column stratification and a single thermal and delta O-18(water) condition in surface water extending from southern Portugal to the eastern Alboran Sea. Together, these observations imply that inflow of Atlantic water into the Mediterranean was significantly increased during HS periods compared to background glacial conditions. Modeling efforts confirm that this is a predictable consequence of freshening North Atlantic surface water with iceberg meltwater and indicate that the enhanced exchange condition would last until the cessation of anomalous freshwater supply into to the northern North Atlantic. The close coupling of dynamics at Gibraltar Exchange with the Atlantic freshwater system provides an explanation for observations of increased Mediterranean Outflow activity during HS periods and also during the last deglaciation. This coupling is also significant to global ocean dynamics, as it causes density enhancement of the Atlantic water column via the Gibraltar Exchange to be inversely related to North Atlantic surface salinity. Consequently, Mediterranean enhancement of the Atlantic Meridional Overturning Circulation will be greatest when the overturning itself is at its weakest, a potentially critical negative feedback to Atlantic buoyancy change during times of ice sheet collapse.

The eastern Mediterranean sapropels are amongst the most intensively investigated phenomena in the palaeoceanographic record , but relatively little has been written regarding the origin of the equivalent of the sapropels in the western Mediterranean, the Organic Rich Layers (ORL's). ORL's are recognised as sediment layers containing enhanced Total Organic Carbon that extend throughout the deep basins of the Western Mediterranean, and are associated with enhanced total barium concentration and a reduced diversity (dysoxic but not anoxic) benthic foraminiferal assemblage. Consequently, it has been suggested that ORL's represent periods of enhanced productivity coupled with reduced deep ventilation, presumably related to increased continental runoff, in close analogy to the sapropels. We demonstrate that despite their superficial similarity, the timing of the deposition of the most recent 1 ORL in the Alboran Sea is different to that of the approximately coincident sapropel, indicating that there are important differences between their modes of formation. We go on to demonstrate, through physical arguments, that a likely explanation for the origin of the Alboran ORLs lies in the response of the Western Mediterranean basin to a strong reduction in surface water density and a shoaling of the interface between intermediate and deep water during the deglacial period. Furthermore, we provide evidence that deep convection had already slowed by the time of Heinrich Event 1, and explore this event as a potential agent for preconditioning deep convection collapse. Important differences between Heinrich-like and deglacial-like influences are highlighted, giving new insights into the response of the western Mediterranean system to external forcing.

Introduccion. El diagnostico del trastorno por deficit de atencion con o sin hiperactividad (TDAH) es un proceso controvertido, que en cierta manera puede condicionarse por el sistema de clasificacion diagnostico, por el instrumento de medida, por la poblacion elegida y por la fuente de informacion. Esta disparidad de factores se pone de manifiesto en los estudios epidemiologicos, donde los indices de prevalencia varian tan ampliamente que oscilan entre el 1 y el 30%, aunque la mayoria de los estudios la situan entre un 3 y un 5%. Objetivo. Estudiar la utilidad de la escala para la evaluacion del trastorno por deficit de atencion con hiperactividad (EDAH) como instrumento de cribado de la sintomatologia TDAH en el ambito escolar. Sujetos y metodos. Se estudian 2.401 escolares de ambos sexos, de 6-12 anos y escolarizados en 10 centros de Barcelona y del Valles Occidental. Resultados. El analisis de los datos obtenidos nos indica que un 12% de nuestra muestra tiene riesgo de TDAH, por lo que uno de cada ocho escolares podria presentar el trastorno en cuestion. Los ninos obtienen puntuaciones superiores en casi todas las subescalas del EDAH respecto a las ninas, y se constata una proporcion de 4:1. Conclusion. Dada la prevalencia encontrada del fenomeno, los autores sugerimos profundizar en el estudio para determinar la prevalencia del trastorno como entidad diagnostica.