Diverse Regional Sensitivity of Summer Precipitation in East Asia to Ice Volume, CO₂ and Astronomical Forcing

Abstract

The relative influence of insolation, CO2, and ice sheets on the East Asian summer monsoon (EASM) is not well understood especially at regional scale. Here a Gaussian emulator based on simulations with HadCM3 is used to quantitatively assess how astronomical forcing, CO2, and northern hemisphere ice sheets affect the variation of the summer precipitation over the last 800 ky. Our results show that in the EASM domain north of 25°N, the variation of the summer precipitation is dominated by precession, leading to strong 23‐ky cycles, while the ice sheets only modulate the effect of insolation by influencing the land‐sea pressure gradient. In the southern part, ice sheets play a more important role, generating 100‐ky cycles, through influencing the latitude of the Intertropical Convergence Zone and the Hadley cell. Obliquity and CO2 have little effect on the summer precipitation as compared to precession and ice sheets.

Magnetic Properties of the Ganzi Loess and Their Implications for Precipitation History in the Eastern Tibetan Plateau Since the Last Interglacial

“…The reconstructed ISM record of Ganzi loess is consistent with the stacked benthic δ 18 O records and atmospheric CO 2 concentrations on a glacial‐interglacial timescale, indicating an important influence of global ice volume on the monsoon (Bereiter et al., 2015; Lisiecki & Raymo, 2005; Lyu et al., 2021). To further evaluate the driving factors of the IMS, we conducted a spectral analysis.…”

Northern Hemisphere ice sheet expansion intensified Asian aridification and the winter monsoon across the mid-Pleistocene transition

“…Regardless, our minimum estimates from model results strongly support the hypothesis that intensi cation and southeastward expansion of Asian aridity, increased coarse dust availability, and winter monsoon wind strengthening caused increased coarse dust transport and loess coarsening across the CLP in response to Northern Hemisphere ice sheet expansion across the MPT. Our model output is broadly consistent with previous post-MPT simulations of marked ice sheet impacts on the Asian climate [49][50][51][52][53] , although those simulations used different boundary conditions. Consistent with the above scenario, new sandy deserts (e.g., Badain Jaran Desert, Tengger Desert) formed at ~ 1.2-0.9 Ma to the north of the CLP 16,54 , while existing sandy deserts (e.g., Mu Us Desert) expanded southward at ~ 1.25 Ma 17 (Fig.…”

Simulated Cycles of East Asian Temperature and Precipitation Over the Past 425 ka

“…However, previous transient simulations (Li et al, 2013;Xie et al, 2020) and Gaussian emulator based on HadCM3 simulations (Lyu et al, 2021), as well as our composited snapshot simulations, consistently demonstrate the dominance of the ∼20-kyr cycle for the seasonal precipitation in East Asia (Figure 5). Insolation modulated by the orbital parameters, in particular the precession, is the dominant forcing for the seasonal precipitation in East Asia.…”

“…One possible reason for these model discrepancies is the different experimental designs in previous individual studies. For example, some previous simulations only considered orbital parameters (e.g., Chen et al., 2011; Li et al., 2013), or generated the outputs by interpolating the simulation of various scenarios during glacial‐interglacial cycles (Lyu et al., 2021; Sun et al., 2019), which may cause uncertainties about the simulations. Moreover, not only experimental designs, but also precipitation schemes in models lead to differences (e.g., Clemens et al., 2018; Xie & Liu, 2020).…”

“…However, the cycles of simulated climate variables — and in particular precipitation — are complex and sometimes ambiguous. Although these simulations show a consistent ∼20‐kyr cycle of simulated summer precipitation in East Asia (e.g., Li et al., 2013; Lyu et al., 2021; Weber & Tuenter, 2011; Xie & Liu, 2020), they also demonstrate a remarkable model‐spread in the cycle of simulated annual precipitation (Clemens et al., 2018; Li et al., 2013; Li, Liu, Zhao., 2017; Lyu et al., 2021; Sun et al., 2019; Thomas et al., 2016). For example, the annual precipitation in NC according to the simulation with CCSM 3.0 shows a strong dominance of the ∼20‐kyr cycle (Li et al., 2013; Li, Liu, Zhao., 2017) while the ∼100‐kyr cycle is more or less absent.…”