Reconstructing global overturning from meridional density gradients

Despite the complexity of the global ocean system, numerous attempts have been made to scale the strength of the meridional overturning circulation (MOC), principally in the North Atlantic, with large-scale, basin-wide hydrographic properties. In particular, various approaches to scaling the MOC with meridional density gradients have been proposed, but the success of these has only been demonstrated under limited conditions. Here we present a scaling relationship linking overturning to twice vertically-integrated meridional density gradients via the hydrostatic equation and a “rotated” form of the geostrophic equation. This provides a meridional overturning streamfunction as a function of depth for each basin. Using a series of periodically forced experiments in a global, coarse resolution configuration of the general circulation model NEMO, we explore the timescales over which this scaling is temporally valid. We find that the scaling holds well in the upper Atlantic cell (at 1000 m) for multi-decadal (and longer) timescales, accurately reconstructing the relative magnitude of the response for different frequencies and explaining over 85 % of overturning variance on timescales of 64–2048 years. Despite the highly nonlinear response of the Antarctic cell in the abyssal Atlantic, between 76 and 94 % of the observed variability at 4000 m is reconstructed on timescales of 32 years (and longer). The scaling law is also applied in the Indo-Pacific. This analysis is extended to a higher resolution, stochastically forced simulation for which correlations of between 0.79 and 0.99 are obtained with upper Atlantic MOC variability on timescales >25 years. These results indicate that meridional density gradients and overturning are linked via meridional pressure gradients, and that both the strength and structure of the MOC can be reconstructed from hydrography on multi-decadal and longer timescales provided that the link is made in this way

Archäometrische Untersuchungen phönizischer Keramik aus Tavira (Portugal)

Tavira gehört zu den Städten auf der Iberischen Halbinsel, die auf eine jahrtausendealte Besiedlung zurückblicken können. In der ersten Hälfte des 1. Jts. v. Chr. war Tavira eine wichtige eisenzeitliche Siedlung mit einem bedeutenden phönizischen Niederschlag. Diese Erkenntnis beruht vor allem auf den archäologischen Untersuchungen, die in den letzten zwanzig Jahren im alten Stadtkern durchgeführt wurden. Im Rahmen des Projektes »Archäometrische Untersuchungen phönizischer Keramik von der Iberischen Halbinsel« wurden 40 Proben phönizischer Keramik aus Tavira, die zwischen dem Ende des 8. und der Mitte des 5. Jhs. v. Chr. datieren, mit mehreren Methoden auf ihre chemische Zusammensetzung hin untersucht. Der Großteil der Proben clustert in eine Gruppe und ist demnach wohl in einem über längere Zeit tätigen Produktionszentrum hergestellt worden. Dieses Zentrum ist wahrscheinlich in Tavira selbst oder in der Region zu lokalisieren.Tavira is one of the cities on the Iberian Peninsula looking back on an extremely longstanding occupation. In the first half of the 1st millennium BC, Tavira was an important Iron Age settlement with a significant Phoenician material fallout. This conclusion is primarily based on archaeological investigations in the old town carried out in the last twenty years. Within the framework of the project »Archaeometric Investigations of Phoenician Pottery from the Iberian Peninsula« 40 samples of Phoenician pottery from Tavira, dating between the end of the 8th and the mid-5th century BC, were analyzed with multiple methods for their chemical composition. The majority of the samples is clustered in one group and therefore was manufactured in a single production center which was active over a long period of time. Most likely, this center can be localized in Tavira itself or in its surroundings.Tavira es una de las ciudades de la Península Ibérica en la que se puede echar la vista atrás sobre un asentamiento milenario. En la primera mitad del 1er milenio antes de Cristo Tavira fue un asentamiento importante de la Edad de Hierro, con significativos restos de materiales fenicios. Estas conclusiones se basan principalmente en las investigaciones arqueológicas llevadas a cabo en los últimos veinte años en el casco antiguo. En el marco del proyecto »Invesj. tigaciónes Arqueométricas de la Cerámica Fenicia de la Península Ibérica« se analizaron con múltiples métodos la composición química de 40 muestras de cerámica fenicia de Tavira, que datan del periodo comprendido entre el final de los siglos VIII y la mitad del siglo V antes de Cristo. La mayoría de las muestras se agrupan en un grupo y, por tanto, fueron fabricadas en un único centro de producción que estuvo trabajando durante un largo período de tiempo. Este centro estuvo probablemente localizado en la propia Tavira o en la región