Abrupt hydrographic change in the Alboran Sea (western Mediterranean) around 8000 yrs BP

This paper discusses planktonic foraminiferal fauna results from the Alboran Sea, western Mediterranean. In this new record, as well as in previously published records, a rather abrupt faunal change occurs around 8000 BP, from dominance of Neogloboquadrina pachyderma (dextrally coiled) with Globigerina bulloides, to dominance of Globorotalia inflata with Globigerina bulloides. The paper argues that this change marks the onset around that time of more or less modern conditions with distinct geostrophic fronts separating the jet of Atlantic inflow from ambient Mediterranean waters. According to a previously published hydraulic control model for the Strait of Gibraltar with variable sea level, the inflow volume of Atlantic water around 8000 BP (sea level at about −30 m) may have amounted to a maximum of about 86% of its present value. Our reconstruction suggests, therefore, that the modern front-dominated conditions in the Alboran Sea prevail only when the inflow volume is at least 86% of the present volume, which should be confirmed in realistic models of the circulation through the Strait of Gibraltar and in the Alboran Sea.