Reconstructions of the Quaternary paleohydrological variability by planktonic foraminifers (North Atlantic, Reykjanes Ridge)

Climatic: stratigraphy in a sediment core (58degrees44.4'N, 27degrees17.3'W, water depth 2155 m, core length 460 cm) on the basis of radiocarbon, oxygen isotope, and lithological data is established for an interval of about 145 ky. The method of factor analysis and spline interpolation applied to the data on the distribution of planktonic foraminiferal species allowed us to reconstruct the mean annual and seasonal values of temperature and salinity at the surface and at a depth of 100 m. The optimum of the last interglacial (5e) is characterized by the maximum temperatures, small amplitudes of seasonal fluctuations, and increased thickness of the upper homogeneous layer. The glacial hydrological environment appeared here 115 ky BP. The coolings were ahead of the appropriate events of the global continental glaciation. The minimum mean annual temperatures (4.0-4.5degreesC) are reconstructed for 47-45, 42, 36, 30-29, and 10 ky BP. In the interval 50-30 ky BP, numerous strong fluctuations of temperature, which reflect migrations of the polar front, are established. The salinity increment between the surface and a depth of 100 m, which indicates the influence of the melting waters, was maximum at the beginning of the deglaciations (135 and 20 ky BP) and repeatedly arose in the interval 50-30 ky BR The last glacial maximum (18 ky BP) is characterized by the lowest salinity with no peak of low temperatures at the surface. The surface temperature has decreased until 10 ky BP. The mean annual surface temperature of the Holocene optimum was 2degreesC greater than the present-day one and 2degreesC smaller than in the interglacial optimum (5e); at that time, the thickness of the upper homogeneous layer exceeded 100 m.