HEINRICH EVENT RELATED CHANGES IN THE ALBORAN SEA WATER PROPERTIES

Millennial scale climate variability during the last glacial period had an strong impact in the Mediterranean region, particularly in the surface water properties of the Alboran Sea (the westernmost basin of the Mediterranean Sea). The combined approach of parallel measurements of Mg/Ca and d ¹⁸O in different species of planktonic and benthic foraminifers permits a detailed reconstruction of water properties (temperature, sea water d ¹⁸O/salinity) at different water depths. Here we study the last glacial interval in core MD 95-2043 from the Alboran Sea, the resolution of which is good enough to resolve centennial scale changes. HEs at this location, away from the deposition of IRD, are identified by sharp cooling events recorded in the alkenone SST estimates and the concurrent presence of the polar foraminifer N. pachyderma (s). These SST cold events are also confirmed by the Mg/Ca record from G. bulloides. However, while the warming phase at the end of HEs match in both timing and intensity, the onset cooling phase is less pronounced in the Mg/Ca record, as a result of the relatively cold temperatures of the previous interstadials. These differences in shape and also absolute values between alkenone and Mg/Ca SST records are interpreted in terms of seasonal differences, suggesting a more abrupt cooling phase for the cold season. Detailed analyses of the different temperature and isotope records across HEs 1-5 illustrate the consistent occurrence of a complex three-phase pattern during HEs. This pattern is particularly pronounced in those records related to the thermocline and deep waters masses whose properties are modelled by climatic/oceanographic conditions in the Mediterranean region. In particular, sea water d ¹⁸O reconstructed by N. pachyderma (d) evolves following an enrichment-depletion-enrichment sequence. This middle HE light isotopic phase of the thermocline is synchronous with a very short warming of the deep water mass as indicated by Mg/Ca in Cibicidoides and is also coincident with a very short intra-stadial warming event recorded in Greenland ice d ¹⁸O records. These results show a complex HE evolution and outline the rapid responses and links between properties of the different Mediterranean water masses.