The oceanographic variability along the North Atlantic margins through the last 2000 yrs: climatic impacts and forcing mechanisms reconstructed from high-resolution diatom records

Several locations along the North Atlantic margins are investigated to provide high-resolution paleoceanographic reconstructions based on diatom records for the last 2000 yrs: the Tagus pro-delta (SW Portuguese margin), the Skagerrak (NE North Sea) and the Laurentian fan (South of Newfoundland). The North Atlantic Oscillation (NAO) is considered as the main climatic factor controlling the northeastward heat flux associated with the Gulf Stream, the wind pattern and the distribution of the precipitation over the North Atlantic realm. The major climatic periods of the last 2000 yrs, the Dark Ages (DA), the Medieval Warm Period (MWP) and the Little Ice Age (LIA), are identifiable in the sedimentary sequences and the climatic events identified correspond to NAO type situations, even at the Tagus pro-delta, the oceanic response is not in phase with the others locations during the DA, showing that the NAO mechanism by itself is not sufficient to explain all the observed oceanographic variability. Besides, the centennial frequencies and timing of the cooling indicated by the diatom record over the Laurentian fan suggest the impact of the solar forcing.