Assessing atmospheric and oceanic teleconnections between the eastern and western Mediterranean over the past 8000 years

Abstract

Holocene climate records from the Mediterranean are marked by pervasive millennial to centennial-scale climate variability. Here, we investigate East-West Mediterranean atmospheric and oceanic teleconnections by computing phase-relationships between oxygen isotope (δ18O) records generated on Soreq (East) and Chorchia (West) spelaeothems, as well as between δ18O and carbon isotope (δ13C) records from planktonic and benthic foraminifera from core PS009PC (East, Levantin Basin), ODP Site 963D (Central, Sicily Strait), and core KESC9-14 (West, Ligurian Basin). These marine sites are all located at intermediate water depths (560–460 m depth). Hence, the benthic foraminiferal δ18O records reflect mainly the intermediate ocean temperature/δ18O of the water mass, and the benthic δ13C is a proxy for the intensity of water flowing at the studied depth called Levantine Intermediate Water (LIW). For both western and eastern cores, the planktonic stable isotopic records reflect the climate-induced activity of the nearby river system. We find broadly in-phase relationships between the spelaeothem δ18O records and between the planktonic δ18O and δ13C records at most multi-centennial and millennial periodicities. This is indicative of closely linked (hydro-) climatic conditions in Southern Europe, the Levant, and North Africa over the last 8000 years. Conversely, at intermediate water depths, we find a distinct out-of-phase relationship between the East/Central and West Mediterranean benthic δ18O and δ13C records at 1000–2000 years periodicities. We interpret this see-saw pattern as indicative of a persistent regional influence of LIW on oceanographic conditions in the intermediate depths of the eastern basin. Conversely, we suggest a strong influence of the modified Atlantic Ocean inflow (MAW) in the intermediate water formation in the Western Mediterranean (‘Winter Intermediate Water’; WIW). This WIW overprints, at least partially, the LIW signal that reaches the western Mediterranean causing the out-of-phase relationship between the east and the west oceanographic signals at intermediate depths.