Millennial-scale climate change and oceanic processes in the late Pliocene and early Pleistocene

We generated 200-500 year resolution records of oceanic processes in the North Atlantic (Ocean Drilling Program Site 983, 60 degrees 24'N, 23 degrees 38'W, 1983 meters water depth) for intervals in the latest Pliocene (1.86-1.93 Ma) and the earliest Pleistocene (1.75-1.83 Ma) in order to examine the linkages between millennial-scale variations in the ocean and background glacial-interglacial climate change. Within glacial intervals we fmd evidence for variations similar to those observed in the late Pleistocene. We find discrete ice-rafted debris (IRD) events that reoccur every 2-5 kyr. These events are preceded by a short cooling and accompanied by a reorganization of glacial deep waters. The timing of IRD events in the late Pliocene and early Pleistocene intervals is similar to that of Dansgaard-Oeschger cycles, but we find no HD events comparable in timing to late Pleistocene Heinrich events. Although interglacial intervals are much more stable, we do find evidence for low-amplitude variations in deep water properties that reoccur every similar to2 kyr within interglacial intervals. The similarity between our late Pliocene-early Pleistocene records and late Pleistocene records implies that the mechanism driving millennial-scale variations cannot be uniquely attributed to the strongly nonlinear linkage between climate and insolation and the large ice sheets of the late Pleisfocene.