Reconstruction of surface water dynamics in the North Atlantic during the Mid-Pleistocene (~540–400 ka), as inferred from coccolithophores and planktonic foraminifera

Abstract

Abstract Changes in paleoclimate and paleoproductivity patterns have been identified by analyzing the coccolithophore assemblages from the IODP Site U1314, located in the subpolar North Atlantic, together with other proxy data available during the time interval from the Marine Isotope Stages (MIS) 14 to MIS 11 (ca. 540 to 400 ka). The comparison of this data with that of MD03–2699, located off the Iberian Margin, allowed us to study their common response to environmental changes in terms of paleoproductivity and temperature variability. Statistical analyses of the composition of coccolithophore assemblages revealed that the calcareous plankton dynamics were mainly driven by eccentricity, which controlled the alternating migration of the Polar Front (PF) and the North Atlantic Current (NAC) at glacial-interglacial timescales. The high frequency variability of paleoproductivity, over imposed onto glacial/interglacial variability at both sites, were related to NAC intensifications on a precessional timescale. The northward (southward) migration of the PF caused a strengthening (weakening) of the NAC, which created an intensification (weakening) of the Irminger Current (IC) at Site U1314 and the Portugal Current (PC) at MD03–2699. Furthermore, low-latitude processes have been shown to influence climate in the high-latitude during the late Pleistocene. During MIS 14 and 12, enhanced glacial strength affected both coccolithophores and planktonic foraminifera, indicating a southward movement of the NAC. Using the same proxies, a northward movement of the NAC is recorded during MIS 13 and 11. Alternatively, the spectral analyses performed on calcareous plankton assemblages allowed the identification of a pattern of periodic response of the plankton at the orbital and, in some cases, millennial level, as well as abrupt Heinrich-type time-scale variability during Termination V (TV). This was the most extreme event and was related to a massive iceberg discharge from high to mid-latitudes.