Late Pleistocene Ice Ages Research Articles

A low‐order dynamical model of global climatic variability over the full Pleistocene

A previously formulated dynamical model of the late Pleistocene ice ages (based on the hypothesis that the global CO2 system can provide the instability to drive a natural oscillation involving feedbacks between the cryosphere, atmosphere, and ocean) is extended to include (1) additive earth orbital forcing (summer insolation changes at 65°N) and (2) tectonic forcing in the form of a postulated variation in the multiplicative parameters (rate constants) of the model system. The structural (e.g., bifurcation) properties of the model are examined in detail to reveal the regions of parameter space wherein the geologically inferred features of the full Pleistocene can be simulated, including the observed chronology, the phase relationships between ice, CO2, and North Atlantic Deep Water formation, and the mid‐Pleistocene transition.

The orbital-tuned marine oxygen isotope record applied to the middle and Late Pleistocene pollen record of Funza (Colombian Andes)

Assuming that orbital variations are the main external cause of the succession of Late Pleistocene ice ages, deep-sea stratigraphers developed an orbital-tuned chronology of the marine oxygen isotope record. The pollen record of Funza (Eastern Cordillera, Colombia) displays in great detail long-range altitudinal shifts of the forest line, being also an expression of long-range fluctuating global temperatures. Both records of palaeotemperature were visually correlated: 48 isotopic events are assumedly reflected in the pollen record. This enables an “orbital-tuning” of the initial time frame of the pollen record, which was based on 14 dated volcanic ash horizons, and provides a detailed record of changes in sediment accumulation in the sedimentary basin of Bogotá. Inferences for the time frame of the pollen record of Páramo de Agua Blanca from the same area are discussed.

Carbon cycle instability as a cause of the Late Pleistocene Ice Age Oscillations: Modeling the asymmetric response

A dynamical model of the Pleistocene ice ages, incorporating many of the qualitative ideas advanced recently regarding the possible role of ocean circulation, chemistry, temperature, and productivity in regulating long‐term atmospheric carbon dioxide variations, has been constructed. This model involves one additional term (and free parameter) beyond that included in a previous model (B. Saltzman and A. Sutera, 1987), providing the capacity for an asymmetic (for example, “saw‐toothed”) response. It is shown that many of the main features exhibited by the δ18O‐derived ice record and the Vostok core/δ13C‐derived carbon dioxide record in the late Pleistocene can be deduced as a free oscillatory solution of the model, including a rapid déglaciation during which a spike of high CO2 and a rapid surge in North Atlantic deep water production occurs. It is expected that the addition of reasonable levels of external (for example, Earth orbital) forcing will enable the model to account for a significant amount of the remaining observed variance and covariance of the slow response climatic variables over the full Pleistocene including the mid‐Pleistocene transition.

ON THE CONTINENTAL SHELVES AROUND THE JAPANESE ISLANDS

1 It is difficult to explain the uniformity of the depth of shelf margin, in some various geological provinces, with the uniformity of the amount of the crustal movement in the Pleistocene Age. 2 The continental shelves around the Japanese Island are divided into two terraces which related to glacial eustasy during the late Pleistocene Ice Age. 3 During that time, the Japan Sea have continued lagoonal cond-ition, and the delta developed at the river mouth. These deltas consist of the continental shelves of the Japan Sea. Contrary, the Pacific side of the Japanese Islands, in many areas, the continental shelves are consisted of basal rocks which are exposed by marine erosion. 4 The time of shelf forming was between Elephas namadicies naumanni Makiyama and Mammonteus primiganius prinigenius Blumenbach, namely it was early Wurm Ice Age.