New insights into upper MOW variability over the last 150kyr from IODP 339 Site U1386 in the Gulf of Cadiz

Abstract

The upper Mediterranean Outflow Water (MOW) paleo-oceanographic history in the Gulf of Cadiz is poorly constrained due to the lack of high-resolution records that pre-date the last glaciation. Existing proxy records concentrate on MOW variability along the middle slope of the Gulf of Cadiz. Here we present a continuous high-resolution benthic foraminifera δ18O record from the upper MOW core at IODP Expedition 339 Site U1386 in the Gulf of Cadiz of the past 150,000 years. Based on δ18O, grain-size and Zr/Al variability comparison of our results with existing Mediterranean Sea (MD01-2472, MD95-2043), open ocean (LR04) and Gulf of Cadiz (MD99-2339) records we have gathered new insights into the evolution of the upper MOW core on glacial–interglacial timescales. The influence of the upper MOW at Site U1386 was strongest during MIS 5 and MIS 1. Similar δ18O variability can be seen in the Levantine Intermediate Water (LIW) originating from the Levantine Basin of the Eastern Mediterranean Sea. We found clear indication for a vertical shift of the MOW from the upper to the middle slope of the Gulf of Cadiz during sea level lowstands coinciding with MIS 4 and MIS 2 but also during MIS 3. Additionally, our results indicate an increased upper MOW flow correlated with Heinrich Events 7 to 10 and the Younger Dryas, and also inversely relate to precession-forced monsoonal freshwater inputs into the Eastern Mediterranean. In the context of Sapropel formation, we could not find conclusive evidence of the proposed MOW shutdown in our data.