The Pliocene-Pleistocene transition marks an important climatic transition when Northern Hemisphere ice sheets expanded. However, the rhythm of Greenland ice sheet change and its contribution to global ocean oxygen isotope records have remained difficult to quantify.
To address this, the team used the IPSL-CM5A Earth system model together with the GRISLI three-dimensional thermo-mechanical ice sheet model. They ran simulations under multiple atmospheric CO 2 scenarios and orbital forcing (summer insolation at 65 degrees north), then analyzed the simulated ice-volume time series with wavelet and wavelet-coherence methods to identify dominant cycles and phase relationships.
The simulations indicate that when the Greenland ice sheet was small, its variability tracked summer insolation more closely and showed a stronger precession signal. As the ice sheet expanded, the 41,000-year obliquity cycle became dominant. After about 2.7 million years ago, variability at sub-orbital to millennial timescales intensified, suggesting increased dynamical instability as the ice sheet reached a larger state.
Comparisons with the LR04 benthic oxygen-isotope stack suggest Greenland ice volume contributed more to the 41,000-year signal after about 2.7 million years ago. At the same time, the results imply that Greenland ice changes alone cannot fully explain the persistence of the 41,000-year cycle and longer-period strengthening in marine records, highlighting the need to consider other Northern Hemisphere ice sheets, Antarctic ice changes, and ocean processes.
See the article:
Tan N, Guo Z, Xu C, Hu B, Zhang Z. 2026. The cyclicity of Greenland ice sheet evolution during the Pliocene-Pleistocene transition. Science China Earth Sciences, 69(2): 621–629, https://doi.org/10.1007/s11430-025-1796-4
Science China Earth Sciences