During the period of instrumental records, the North Atlantic Oscillation (NAO) has strongly influenced inter-annual precipitation variations in the western Mediterranean, while some eastern parts of the basin have shown an anti-phase relationship in precipitation and atmospheric pressure. Here we explore how the NAO and other atmospheric circulation modes operated over the longer timescales of the Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). High-resolution palaeolimnological evidence from opposite ends of the Mediterranean basin, supplemented by other palaeoclimate data, is used to track shifts in regional hydro-climatic conditions. Multiple geochemical, sedimentological, isotopic and palaeoecological proxies from Estanya and Montcortés lakes in northeast Spain and Nar lake in central Turkey have been cross-correlated at decadal time intervals since AD 900. These dryland lakes capture sensitively changes in precipitation/evaporation (P/E) balance by adjustments in water level and salinity, and are especially valuable for reconstructing variability over decadal-centennial timescales. Iberian lakes show lower water levels and higher salinities during the 11th to 13th centuries synchronous with the MCA and generally more humid conditions during the 'LIA' (15th-19th centuries). This pattern is also clearly evident in tree-ring records from Morocco and from marine cores in the western Mediterranean Sea. In the eastern Mediterranean, palaeoclimatic records from Turkey, Greece and the Levant show generally drier hydro-climatic conditions during the LIA and a wetter phase during the MCA. This implies that a bipolar climate see-saw has operated in the Mediterranean for the last 1100. years. However, while western Mediterranean aridity appears consistent with persistent positive NAO state during the MCA, the pattern is less clear in the eastern Mediterranean. Here the strongest evidence for higher winter season precipitation during the MCA comes from central Turkey in the northeastern sector of the Mediterranean basin. This in turn implies that the LIA/MCA hydro-climatic pattern in the Mediterranean was determined by a combination of different climate modes along with major physical geographical controls, and not by NAO forcing alone, or that the character of the NAO and its teleconnections have been non-stationary.
Bibliographical noteFunding Information:
JL and EX were supported by the EU/FP6 project CIRCE (# 036961 ), the EU/FP7 project ACQWA (# 212250 ). JL acknowledges support by the Deutsche Forschungsgemeinschaft project PRIME ( LU1608/1-1, AOBJ: 568460 ) within the Priority Programme ‘INTERDYNAMIK’ and the project “Historical climatology of the Middle East based on Arabic sources back to ad 800” ( LU 1608/2-1 AOBJ 575150 ). This research has been partially funded by the Spanish InterMinistry of Science and Technology (CICYT) , through the projects GLOBALKARST ( CGL2009-08415 ) and GRACCIE-CONSOLIDER ( CSD2007-00067 ). AM also acknowledges the “Ramón y Cajal” postdoctoral programme for funding. MJ, JW and SA were supported by University of Plymouth research studentships. Research at Nar lake was supported by the British Institute in Ankara , the National Geographic fund and NERC . We thank Jane Reed and an anonymous reviewer for helpful comments, the Plymouth University cartographic unit and Andrea Toreti for the correlation maps and discussions.
Copyright 2012 Elsevier B.V., All rights reserved.
- Little Ice Age
- Medieval Climate Anomaly
- North Atlantic Oscillation
- Teleconnection patterns
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