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

Abstract

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.

The role of orbital forcing, carbon dioxide and regolith in 100 kyr glacial cycles

“…Saltzman and Maasch, 1988;Paillard and Parrenin, 2004;Tziperman et al, 2006). In the latter case, glacial cycles with a typical periodicity of 100 kyr exist in the system even without orbital forcing (i.e.…”

“…In view of this long-standing problem, it was proposed that the 100 kyr cycles do not originate directly from the orbital forcing but rather represent internal oscillations in the climate-cryosphere (Gildor and Tziperman, 2001) or climate-cryosphere-carbonosphere system (e.g. Saltzman and Maasch, 1988;Paillard and Parrenin, 2004), which can be synchronized (phase locked) to the orbital forcing (Tziperman et al, 2006). Alternatively, it was proposed that the 100 kyr cycles result from the terminations of ice sheet buildup by each second or third obliquity cycle (Huybers and Wunsch, 2005) or each fourth or fifth precessional cycle (Ridgwell et al, 1999) or they originate directly from a strong, nonlinear, climate-cryosphere system response to a combination of precessional and obliquity components of the orbital forcing (Paillard, 1998).…”

Assessing orbitally-forced interglacial climate variability during the mid-Pliocene Warm Period

“…Future work will look at these two additional feedbacks alongside changing orbit. We have not run simulations in which CO 2 covaried with orbit, but we do know there is a relationship between CO 2 and orbital forcing from the late Pleistocene (Saltzman and Maasch, 1988;Berger et al, 1999). However, most CO 2 reconstructions have relatively low temporal resolution.…”

Climate: Is the past the key to the future?

“…Most notably, the alternate growth and melting of ice sheets in the northern hemisphere has been attributed to waxing and waning of the radiation received from the sun (insolation) as a result of changes in the earth's orbital parameters (Milankovitch 1920(Milankovitch , 1930Emiliani and Geiss 1959;Hays et al 1976), amplified by positive feedback mechanisms (Saltzman et al 1984;Saltzman and Maasch 1988;Broecker 1995).…”