ABSTRACT
The effect of the astronomical forcing on the northern hemisphere only becomes clear with the first episodes of widespread glaciation of the middle Pleistocene, after –3 Ma. There may however be complementary explanations to the dominating presence of obliquity cycles in the Early Pleistocene marine isotopic record. Compared to the cycles of the early Pleistocene, the late Pleistocene cycles carry the clear signature of non-linear dynamics. The Mid-Pleistocene Transition towards larger ice sheets, colder climates, and longer ice ages must have generated even more aridity on average. Ice-dammed lakes in the Siberian planes have been suggested to have such a positive influence by creating cold conditions which inhibit ice melt. Marine records have made it clear that Heinrich layers coincide with very cold conditions in the North Atlantic, little or no deep-water convection, and low salinity. Compared to Africa, South American vegetation appeared to be much more responsive to Heinrich events.
