Pleistocene glacial cycles

PLIO-PLEISTOCENE GLACIAL CYCLES AND MILANKOVITCH VARIABILITY... 

A tremendous amount of data on past climate has been collected from deep-sea sediment cores, ice cores, and terrestrial archives such as lake sediments. However, several of the most fundamental questions posed by this data remain unanswered. In particular, the Plio-Pleistocene glacial cycles which dominated climate during the past 2.8My have puzzled scientists. More often than not during this period large parts of North America and northern Europe were covered by massive ice sheets up to 3 km thick, which at regular intervals rapidly retreated, giving a sea level rise of as much as 120 m. 

The Plio-Pleistocene glacial cycles represent some of the largest and most significant changes in past... 

In addition to the challenge of modeling the mid-Pleistocene transition, no model has successfully reproduced the relatively clean 41000-year cycles preceding the transition, hollowing the transition, the models only exhibit a good match with the observed glacial cycles when forced with reconstructed CO2 from Antarctic ice cores together with orbital insolation. 

Hoorn, C., Palynology of the Pleistocene glacial/interglacial cycles of the Amazon fan (holes 940A, 944A, and 946A), Proc. ODP, Sci. Results, 155, 397, 1997. 

The last ice age caused reductions in the diversity of terrestrial vertebrate faunas in most continents and many islands at the end of the Pleistocene and the start of the Holocene. Such extinctions were not random because species of large body size were more severely affected than those with body masses under 25-50 kg. Human predation played a part as well. However, if environmental fluctuations are offered in order to explain Late Pleistocene extinctions, why did similar ones not occur during previous glacial/interglacial cycles of which there have been a minimum of 22 during the past 870,000 years The unsolved question is whether the Pleistocene/Holocene change was triggered by some factor or factors which were fundamentally different from other environmental fluctuations and if so what were they. 

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