Contribution from natural causes and human activities to climate variability in the westernmost Mediterranean over the last millennium

Abstract

The Mediterranean is particularly sensitive and vulnerable to climate change due to its semi–enclosed configuration and latitudinal position. Over the last millennium, the interplay of natural and human induced environmental changes has resulted in a high degree of land degradation and desertification in this region. Two high–resolution deep–sea records from the westernmost Mediterranean (Alboran Sea basin) enabled the reconstruction of climate conditions during this period as well as to disentangle human fingerprints. The integration of inorganic and organic geochemical proxies (Si, Zr, TEXH86, UK'37 and BIT indexes, δ13Cn-alkanes) showed consistent climatic signals of warm and mostly dry phases during the Medieval Climate Anomaly alternating with humid and cold periods during the Little Ice Age. The industrial period was characterized by increasing humidity. Human influence has been evidenced in the sedimentary record by the unprecedented rise of temperatures, progressive aridification and increasing concentration of pollutants elements (Pb, Hg, Zn, Cu). Causes of climate variability seem to be promoted by solar forcing and the modulation of the North Atlantic Oscillation during the last millennium and recent anthropogenic contributions since Industrial times.