A major and long-term Pliocene intensification of the Mediterranean outflow, 3.5-3.3 Ma ago

• Published in: Geology (Boulder) 2009-09, Vol.37 (9), p.811-814
• Main Authors: Khelifi, Nabil, Sarnthein, Michael, Andersen, Nils, Blanz, Thomas, Frank, Martin, Garbe-Schönberg, Dieter, Haley, Brian A, Stumpf, Roland, Weinelt, Mara
• Format: Article
• Language: English
• Subjects: Alboran Sea; alkaline earth metals; Atlantic Ocean; calcium; Cenozoic; convection; cores; Deep Sea Drilling Project; deep-water environment; DSDP Site 548; Foraminifera; geochemistry; Geological time; Geology; Globigerina; Globigerina bulloides; Globigerinacea; Globigerinidae; Globigerinoides; Globigerinoides ruber; Goban Spur; Invertebrata; IPOD; isotope ratios; isotopes; Leg 161; Leg 80; magnesium; marine sediments; Mediterranean Outflow Water; Mediterranean Sea; metals; Mg/Ca; microfossils; neodymium; Neogene; North Atlantic; North Atlantic Deep Water; O-18/O-16; Ocean Drilling Program; ODP Site 978; oxygen; paleo-oceanography; paleocirculation; paleoclimatology; paleosalinity; paleotemperature; Pliocene; Protista; rare earths; Rotaliina; sediments; stable isotopes; Stratigraphy; Tertiary; Water temperature; West Mediterranean
• ISSN: 0091-7613; 1943-2682
• DOI: 10.1130/G30058A.1

Largely continuous millennial-scale records of benthic δ18O, Mg/Ca-based temperature, and salinity variations in bottom waters were obtained from Deep Sea Drilling Project (DSDP) Site 548 (East Atlantic continental margin near Ireland, 1250 m water depth) for the period 3.7-3.0 Ma ago. High εNd values of -10.7 to -9 show that this site monitored changes in Mediterranean Outflow Water (MOW) throughout the mid-Pliocene. Bottom water variability at Ocean Drilling Program (ODP) Site 978 (Alboran Sea, 1930 m water depth) provides a complementary record of MOW composition near its West Mediterranean source. Both sites show a singular and persistent rise in bottom water salinities by 0.7-1.4 psu, and in densities by approximately 1 kg m-3 from 3.5 to 3.3 Ma ago, which is matched by an approximately 3°C increase in bottom water temperature at Site 548. This event suggests the onset of strongly enhanced deep-water convection in the Mediterranean Sea and a related increase in MOW flow as a result of major aridification in the Mediterranean source region. In harmony with model suggestions, the enhanced MOW flow has possibly intensified Upper North Atlantic Deep Water formation.