Preprints
https://doi.org/10.5194/cp-2021-47
https://doi.org/10.5194/cp-2021-47

  29 Apr 2021

29 Apr 2021

Review status: this preprint is currently under review for the journal CP.

Does a difference in ice sheets between Marine Isotope Stages 3 and 5a affect the duration of stadials?

Sam Sherriff-Tadano1,6, Ayako Abe-Ouchi1,2,3, Akira Oka1, Takahito Mitsui4,5, and Fuyuki Saito2 Sam Sherriff-Tadano et al.
  • 1Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwa, Japan
  • 2Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
  • 3National Institute of Polar Research, Tokyo, Japan
  • 4Department of Mathematics and Computer Science, Free University of Berlin, Berlin, Germany
  • 5Potsdam Institute for Climate Impact Research, Potsdam, Germany
  • 6School of Earth and Environment, University of Leeds, Leeds, United Kingdom

Abstract. Glacial periods undergo frequent climate shifts between warm interstadials and cold stadials on a millennial time-scale. Recent studies have shown that the duration of these climate modes varies with the background climate; a colder background climate and lower CO2 generally results in a shorter interstadial and a longer stadial through its impact on the Atlantic Meridional Overturning Circulation (AMOC). However, the duration of stadials was shorter during the Marine Isotope Stage 3 (MIS3) compared with MIS5, despite the colder climate in MIS3, suggesting potential control from other climate factors on the duration of stadials. In this study, we investigated the role of glacial ice sheets. For this purpose, freshwater hosing experiments were conducted with an atmosphere–ocean general circulation model under MIS5a, MIS3 and MIS3 with MIS5a ice sheet conditions. The impact of ice sheet differences on the duration of the stadials was evaluated by comparing recovery times of the AMOC after freshwater forcing was reduced. Hosing experiments showed a slightly shorter recovery time of the AMOC in MIS3 compared with MIS5a, which was consistent with ice core data. We found that larger glacial ice sheets in MIS3 shortened the recovery time. Sensitivity experiments showed that stronger surface winds over the North Atlantic shortened the recovery time by increasing the surface salinity and decreasing the sea ice amount in the deepwater formation region, which set favourable conditions for oceanic convection. In contrast, we also found that surface cooling by larger ice sheets tended to increase the recovery time of the AMOC by increasing the sea ice thickness over the deepwater formation region. Thus, this study suggests that the larger ice sheet in MIS3 compared with MIS5a could have contributed to the shortening of stadials in MIS3, despite the climate being colder than that of MIS5a, when the effect of surface wind played a larger role.

Sam Sherriff-Tadano et al.

Status: open (until 24 Jun 2021)

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Sam Sherriff-Tadano et al.

Sam Sherriff-Tadano et al.

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Short summary
Glacial periods underwent climate shifts between warm states and cold states on a millennial time-scale. Frequency of these climate shifts varied along time, and it was shorter during mid-glacial period compared to early-glacial period. In this study, from climate simulations of early and mid-glacial periods with a comprehensive climate model, we show that the larger ice sheet in mid-glacial compared to early-glacial could contributed to the frequent climate shifts during mid-glacial period.