Neural network estimation of chlorophyll a from MERIS full resolution data for the coastal waters of Galician rias (NW Spain)

The Tagus Prodelta (W Portugal) and the Muros Ro´a (NW Spain) are areas of high deposition rates registering high-resolution palaeoclimatic records for western Iberia. We compare the climatic conditions of the two areas over the last two millennia based on proxies of temperature (sea surface temperatures and oxygen isotopes), continental input (grain size, iron and magnetic susceptibility) and productivity (inorganic and organic carbon, carbon isotopes, benthic foraminifera and diatoms). Biogeochemical changes in the Tagus Prodelta reflect widely recognized North Atlantic climatic periods encompassing the Roman Period (AD 0 � 350), the Dark Ages (AD 400 � 700), the 'Mediaeval Warm Period' (MWP; AD 800 � 1200) and the 'Little Ice Age' (LIA; AD 1300 � 1750). The atmospheric North Atlantic Oscillation (NAO) drives the Tagus Prodelta multidecadal, long-term variability in precipitation-river input during cold periods (negative NAO) and marine upwelling during warmer periods (positive NAO), a scheme that is reversed in the Galician region. The Muros Ro ´a shows only local hydrodynamics until AD 1150, including a 'suboxic' event in the inner Ro ´a around AD 500 � 700. Since AD 1150 Atlantic warm upwelled waters have ventilated the outer Ro´a but only reach the inner Ro´a at AD 1750. The twentieth- century records are also interpreted as a reflex of the inverse NAO mode in both areas, resulting in amplification of the LIA biogeochemical water conditions. Centennial-scale solar activity appears to be another important forcing mechanism (or the only one, if solar activity drives the NAO and 'Bond-cycles') behind changes in the hydrography of the Tagus Prodelta, and primary production, bottom ventilation and organic carbon degradation in the Muros Ro ´a.

Climate change and coastal hydrographic response along the Atlantic Iberian margin (Tagus Prodelta and Muros Ría) during the last two millennia

http://www.ugr.es/~grupo179/pdf/Bernardez2008.pdf

Silvia Torres-López

Papers

A general view of the hydrographic and dynamical patterns of the Rías Baixas adjacent sea area