Rapid waxing and waning of Beringian ice sheet reconcile glacial climate records from around North Pacific

Abstract

Abstract. Throughout the Pleistocene the Earth has experienced pronounced glacial-interglacial cycles, which have been debated for decades. One concept widely held is that during most glacials only the Laurentide-Eurasian ice sheets across North America and Northwest Eurasia became expansive, while Northeast Siberia-Beringia remained ice-sheet-free. However, the recognition of glacial landforms and deposits on Northeast Siberia-Beringia and off the Siberian continental shelf is beginning to call into question this paradigm. Here, we combine climate and ice sheet modelling with well-dated paleoclimate records from the mid-to-high latitude North Pacific to demonstrate the episodic occurrences of an ice sheet across Northeast Siberia-Beringia. Our simulations first show that the paleoclimate records are irreconcilable with the established paradigm of Laurentide-Eurasia-only ice sheets, and then reveal that a Beringian ice sheet over Northeast Siberia-Beringia causes feedbacks between atmosphere and ocean, the result of which better explains these climate records from around the North Pacific during the past four glacial-interglacial cycles. Our simulations propose an alternative scenario for NH ice sheet evolution, which involves the rapid waxing and waning of the Beringian ice sheet alongside the growth of the Laurentide-Eurasian ice sheets. The new scenario settles the long-standing discrepancies between the direct glacial evidence and the climate evolution from around the mid-to-high latitude North Pacific. It depicts a high complexity in glacial climates and has important implications for our understanding of the dispersal of prehistoric humans through Beringia into North America.

A Modeling Study of the Tripole Pattern of East China Precipitation Over the Past 425 ka

“…The correlation coefficient between the simulated EASMI (or ICE6G‐EASMI) and atmospheric CO 2 levels is less than 0.04 (less than 0.25, or even negative) (Figures 5d–5f and 6d–6f), which is much lower than the correlation coefficient (∼0.49–0.73) between the EASMI (or ICE6G‐EASMI) and boreal summer insolation (Figures 5a–5c and 6a–6c). Moreover, the correlation coefficient between the simulated EASMI and the NH ice volume are low (less than 0.26; Figures 5g–5i; Zhang, Yan, et al., 2020). Such a weak correlation also appears in the simulated EASMI (or ICE6G‐EASMI) and LR04 δ 18 O from Lisiecki and Raymo (2005) (Figures 5j–5l and 6g–6i).…”

“… Correlation analysis between the simulated EASMI and external forcing factors. (a–c) are for insolation (Laskar et al., 2004); (d–f) are for atmospheric CO 2 levels (Luthi et al., 2008); (g–i) are for simulated Northern Hemisphere ice volume (Zhang, Yan, et al., 2020); and (j–l) are for global ice sheet (LR04, Lisiecki & Raymo, 2005). All the correlation analyses are on the same time scale.…”

“…The simulated NH ice sheets have been introduced in an experimental flow as described in Zhang, Yan, et al. (2020). The ICE6G reconstructed ice sheets are also implemented in the simulations during the last glacial‐interglacial cycle (Peltier et al., 2015).…”

“…In our simulations, the vegetation cover in East Asia remains the same as in the PI experiment. The details of the experimental set-up can be found in Zhang, Yan, et al (2020). In addition, PI and mid-Holocene (6 ka) simulations are also conducted according to the standardized experimental design from the Paleoclimate Modeling Intercomparison Project Phase 3 (PMIP3) (see the PMIP 3 website at https://pmip3.lsce.ipsl.fr/).…”

Simulating Marine Isotope Stage 7 with a coupled climate–ice sheet model

“…Most efforts so far, with the notable exception of Ziemen et al (2019), have used earth system models of intermediate complexity, EMICs, (Ganopolski and Brovkin, 2017;Ganopolski et al, 2010;Stap et al, 2014;Vizcaino et al, 2015;Heinemann et al, 2014;Willeit et al, 2019) or ice sheet models (ISMs) coupled with statistical relationships, based on a set of coupled general circulation model (CGCM) timeslice runs (Abe-Ouchi et al, 2013;Colleoni et al, 2014b) to simulate the transient evolution of the coupled atmosphere-ocean-ice sheet system. Bidirectional coupling between climate components and the ice sheets, typically not captured in offline ice-sheet simulations (Born et al, 2010;Dolan et al, 2015;Koenig et al, 2015), is crucial in representing important feedbacks such as the ice albedo (Abe-Ouchi et al, 2013), elevation-desertification (Yamagishi et al, 2005) and the stationary-wave-ice-sheet (Roe and Lindzen, 2001) feedbacks.…”