Abstract
AbstractEvidence from proxy records indicates that millennial‐scale abrupt climate shifts, called Dansgaard‐Oeschger events, happened during past glacial cycles. Various studies have been conducted to uncover the physical mechanism behind them, based on the assumption that climate mean state determines the variability. However, our study shows that the Dansgaard‐Oeschger events can regulate the mean state of the Northern Hemisphere ice sheets. Sensitivity experiments show that the simulated mean state is influenced by the amplitude of the climatic noise. The most likely cause of this phenomenon is the nonlinear response of the surface mass balance to temperature. It could also cause the retreat processes to be faster than the buildup processes within a glacial cycle. We propose that the climate variability hindered ice sheet development and prevented the Earth system from entering a full glacial state from Marine Isotope Stage 4 to Marine Isotope Stage 3 about 60,000 years ago.
Highlights
Millennial-scale abrupt shifts between cold and warm states, called Dansgaard-Oeschger (DO) events (Dansgaard et al, 1993), are observed in Greenland ice core records through the last glacial cycle
The results show that the ice sheets grow larger when the DO signals are absent, while the mean forcing states are the same (Figure 1b)
Our study shows that climate noise can significantly slow ice sheet development and influence the ice sheet mean state
Summary
Millennial-scale abrupt shifts between cold and warm states, called Dansgaard-Oeschger (DO) events (Dansgaard et al, 1993), are observed in Greenland ice core records through the last glacial cycle. The DO events began with a rapid warming of 8 to 15 ◦C within a few decades, followed by gradual cooling before a jump back to a cold state (Huber et al, 2006). In Antarctic ice cores, millennial-scale oscillations with nearly opposite phase compared to Greenland are found, showing that this phenomenon is global in scale and might be related to the Atlantic ocean heat transport (EPICA Community Members, 2006; Dima et al, 2018). No consistent theory of the physical mechanism of the cause of DO events is widely accepted (Ganopolski & Rahmstorf, 2001; Petersen et al, 2013; Zhang, Lohmann, et al, 2014)
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