Reconstruction of sea-surface temperature, salinity, and sea-ice cover in the northern North Atlantic during the last glacial maximum based on dinocyst assemblages

Past sea-surface conditions over the northern North Atlantic during the las t glacial maximum were examined from the study of 61 deep-sea cores. The la st glacial maximum time slice studied here corresponds to an interval betwe en Heinrich layers H-2 and H-1, and spanning about 20-16 ka on a C-14 time scale. Transfer functions based on dinocyst assemblages were used to recons truct sea-surface temperature, salinity, and sea-ice cover. The results ill ustrate extensive sea-ice cover along the eastern Canadian margins and sea- ice spreading, only during winter, over most of the northern North Atlantic . On the whole, much colder winter prevailed, despite relatively mild condi tions in August (10-15degreesC at most offshore sites), thus suggesting a l arger seasonal contrast of temperatures than today. Lower salinity than at present is reconstructed, especially along the eastern Canadian and Scandin avianmargins, likely because of meltwater supply from the surrounding ice s heets. These reconstructions contrast with those established by CLIMAP on t he basis of plank tonic foraminifera. These differences are discussed with reference to the stratigraphical frame of the last glacial maximum, which w as not the coldest phase of the last glacial stage. The respective signific ance of dinocyst and foraminifer records is also examined in terms of the t hermohaline characteristics of surface waters and the vertical structure of upper water masses, which was apparently much more stratified than at pres ent in the northern North Atlantic, thus preventing deep-water formation.