Abstract

A hydro-climatic reconstruction is proposed for the Minho region (NW Portugal), integrating two different proxies: grape harvest dates (GHD) as a proxy of temperature variations, and benthic marsh foraminifera as a proxy of salinity of sediment interstitial waters. The reconstructed and measured mean maximum temperatures (GSTmax) of grapevine-growing season (March to August) were combined with data on benthic foraminiferal assemblages from the Caminha tidal marsh (Minho River estuary) to characterize the main hydro-climatic episodes in the region during the last 154 years. Results emphasize that, in the brackish setting of the Minho estuary, where foraminiferal species usually associated with low salinity occur, higher GSTmax had an impact on the hydrological balance of the marsh by enhancing evapotranspiration and increasing interstitial salinity. These conditions favored the occurrence of marsh species such as Jadammina macrescens and Trochammina inflata.

The influence of the North Atlantic European meteorological teleconnection patterns on recent climatic variability of the Minho region was also examined from 1950–2009. Data support the hypothesis that persistent positive modes of spring-summer Scandinavian Oscillation Mode (SCA) and summer Eastern Atlantic/ Western Russia Oscillation Mode (EA/ WR) patterns triggered lower GSTmax, especially in the 1960s–1980s. Those conditions, in-phase with a positive precipitation anomaly (1958–1983), reduced the Caminha tidal marsh salinity, leading to the increase of low salinity species: Trochamminita salsa/irregularis, Haplophragmoides manilaensis, Miliammina fusca and Miliammina spp.

Both proxies provide valuable tools for understanding the interactions between large-scale circulation modes and hydro-climatic conditions at regional and local scales.

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