DATE2018-05-17 11:15:56
AUTHORSLA Azibeiro (1), FJ Sierro (1), L Capotondi (2), F Lirer (3), A Cortina (4), JO Grimalt (4), B Martrat (4), I Cacho (5), JA Flores (1), M Canals (5)
  1. Department of Geology, University of Salamanca, Salamanca, Spain
  2. CNR, Instituto Scienze Marine (ISMAR), Bologna, Italy
  3. CNR, Instituto per l’Ambiente Marino Castiero, Napoli, Italy
  4. Department of Environmental Chemistry, Barcelona, Spain
  5. Geociències Marines, Universitat de Barcelona, Barcelona, Spain
ABSTRACTTermination V marks the transition from MIS 12, characterized by wide continental ice sheets in the northern Hemisphere and a prominent global sea level minimum, to MIS 11 a long interglacial stage with a sea-level highstand. In order to understand how that climate shift affected the surface Mediterranean waters, this study has compared two sites from western, ODP site 977, and eastern Mediterranean, KC01(B), through quantitative planktonic foraminifera analyses and stable isotopes. Planktonic oxygen isotopic composition measured in Globigerina bulloides and Neogloboquadrina pachyderma were corrected according to the average annual sea surface temperature (SST) obtained by Artificial Neural Networks (ANN) and the ice volume changes to obtain the sea water oxygen isotopic composition (d18Osw) relative to current values. Lower values than expected were found in d18Osw for MIS 12 at both sites, with a decreasing trend in the whole stage, but was especially significant during four episodes related with polar species increases – N. pachyderma (sinistral) and Turborotalita quinqueloba – and low temperatures. This evidences a high freshwater influence in the Mediterranean during TV and the straight coupling of both isotopic curves suggest a common freshwater source probably originated in the north Atlantic. However, the offsets observed between the western and eastern basins at certain times, point to possible different sources for this freshwater. The d18Osw decrease is reversed during the sharp warming at the onset of MIS 11 to reach values similar to current ones Surface temperatures and d18Osw millennial variability in western and eastern Mediterranean can clarify the timing, origins and dynamics of the fresh water entrance during glacial Termination.