Abrupt climate changes in the last two deglaciations simulated with different Northern ice sheet discharge and insolation

Fuyuki Saito,Ayako Abe-Ouchi,Takashi Obase

doi:10.1038/s41598-021-01651-2

Abstract

There were significant differences between the last two deglaciations, particularly in Atlantic Meridional Overturning Circulation (AMOC) and Antarctic warming in the deglaciations and the following interglacials. Here, we present transient simulations of deglaciation using a coupled atmosphere–ocean general circulation model for the last two deglaciations focusing on the impact of ice sheet discharge on climate changes associated with the AMOC in the first part, and the sensitivity studies using a Northern Hemisphere ice sheet model in the second part. We show that a set of abrupt climate changes of the last deglaciation, including Bolling–Allerod warming, the Younger Dryas, and onset of the Holocene were simulated with gradual changes of both ice sheet discharge and radiative forcing. On the other hand, penultimate deglaciation, with the abrupt climate change only at the beginning of the last interglacial was simulated when the ice sheet discharge was greater than in the last deglaciation by a factor of 1.5. The results, together with Northern Hemisphere ice sheet model experiments suggest the importance of the transient climate and AMOC responses to the different orbital forcing conditions of the last two deglaciations, through the mechanisms of mass loss of the Northern Hemisphere ice sheet and meltwater influx to the ocean.

Highlights

There were significant differences between the last two deglaciations, in Atlantic Meridional Overturning Circulation (AMOC) and Antarctic warming in the deglaciations and the following interglacials
Significant differences occurred after the middle stage of the deglaciation; the greater orbital eccentricity of the EMOD experiment compared with the control experiment induced greater summer insolation and negative mass balance of the ice sheets after 16 ka BP (Fig. 4e)
These results are consistent with a previous study wherein a longer duration of meltwater formation in the deglaciation was found to be needed for Antarctic warming of the LIG22

Summary

Introduction

There were significant differences between the last two deglaciations, in Atlantic Meridional Overturning Circulation (AMOC) and Antarctic warming in the deglaciations and the following interglacials. Clark et al.[27] conducted transient simulation of T2 using reconstructed climate forcing and greater meltwater flux than T1 They compared the results with the simulation of T125 and showed that the greater meltwater flux of T2 corresponding to Heinrich event 11 led to longer weakening in the AMOC and significant Antarctic warming that was sufficient to cause the mass loss of the WAIS. It is still unclear which phase of the deglaciation was important for the AMOC and Antarctic warming, and what the cause of significant ice sheet retreat during deglaciation was. We discuss the roles of orbital forcing and climate system feedbacks in the differences of the last two glacial terminations and the following interglacials

Methods

Results

Conclusion