3:45 PM - 4:00 PM
[ACC29-14] The 40-kyr glacial cycles in the Early Pleistocene (~1.6-1.2Ma): Roles of precession, eccentricity, and obliquity
Keywords:Glacial Cycles, Orbital Parameters, Ice Sheet
In our presentation last year, we simulated the 40-kyr cycles in the Early Pleistocene (~1.6-1.2 Ma) and explained the formation mechanism using a three-dimensional ice sheet model IcIES with climate parameterization based on MIROC (IcIES-MIROC; Abe-Ouchi et al., 2013). In this presentation, we compare the typical 40-kyr cycle with the typical 100-kyr cycle and focus on the role of the 20-kyr variation of precession in the Early Pleistocene. We show that precession is important in (1) determining the timing of the threshold for deglaciations, (2) making the deglaciation usually faster than the glaciation, (3) sometimes forming thin but extensive ice-sheet at the glacial maximum, which waxes and wanes in one precession cycle, and (4) shaping the time-series of the ice-volume, such as ‘pulse-like’, ‘U-shaped’, and ‘saw-toothed’ patterns in the early Pleistocene, which is consistent with the proxy record (e.g. Lisiecki and Raymo, 2005; Hodell and Channell, 2016).
We further infer that the relatively high 100-kyr power of eccentricity in our experiment period (Lisiecki, 2010a) helped form the 40-kyr glacial cycles. This allows the 40-kyr variation of obliquity to assist the deglaciation even when eccentricity is small, and this makes the 40-kyr cycles in the experiment period (~1.6-1.2 Ma) clear.