Abstract
Abstract. Deep-sea and ice-core records show that interglacial periods were overall less "warm" before about 420 000 years ago than after, with relatively higher ice volume and lower greenhouse gases concentration. This is particularly the case for the interglacial Marine Isotope Stage 13 which occurred about 500 000 years ago. However, by contrast, the loess and other proxy records from China suggest an exceptionally active East Asian summer monsoon during this interglacial. A three-dimension Earth system Model of Intermediate complexity was used to understand this seeming paradox. The astronomical forcing and the remnant ice sheets present in Eurasia and North America were taken into account in a series of sensitivity experiments. Expectedly, the seasonal contrast is larger and the East Asian summer monsoon is reinforced compared to Pre-Industrial time when Northern Hemisphere summer is at perihelion. Surprisingly, the presence of the Eurasian ice sheet was found to reinforce monsoon, too, through a south-eastwards perturbation planetary wave. The trajectory of this wave is influenced by the Tibetan plateau.
Highlights
Most of the δ18O records in deep-sea sediments show a significantly reduced amplitude of the ice volume variations before Marine Isotope Stage (MIS) 11, about 400 ka ago, with less warm interglacials and generally less cold glacials (Imbrie et al, 1984; Bassinot et al, 1994; Tiedemann et al, 1994; Shackleton, 2000; Lisiecki and Raymo, 2005)
Numerical experiments made for MIS-13.1 show that the precipitation over China associated to the East Asian Summer Monsoon (EASM) is much stronger when Northern Hemisphere summer is at perihelion rather than when Southern Hemisphere summer is at perihelion, and that it gets reinforced again after the ice sheets are introduced
A series of modelling experiments have been made to understand the palaeo-environmental data showing an exceptionally strong East Asian summer monsoon occurring during the cool MIS-13 interglacial
Summary
Most of the δ18O records in deep-sea sediments show a significantly reduced amplitude of the ice volume variations before Marine Isotope Stage (MIS) 11, about 400 ka ago, with less warm (cooler) interglacials and generally less cold glacials (Imbrie et al, 1984; Bassinot et al, 1994; Tiedemann et al, 1994; Shackleton, 2000; Lisiecki and Raymo, 2005). Qiuzhen Yin et al.: East Asian summer monsoon during the interglacial 500 000 years ago (NH) is cold overall From the latter, one could expect a moderate monsoon at MIS-13 because this interglacial was not as warm and deglaciated as the more recent interglacials, Masson et al (2000) suggested that glacial conditions at MIS-6.5 do not prevent high insolation to produce a strong monsoon. One could expect a moderate monsoon at MIS-13 because this interglacial was not as warm and deglaciated as the more recent interglacials, Masson et al (2000) suggested that glacial conditions at MIS-6.5 do not prevent high insolation to produce a strong monsoon This seeming paradox of a strong EASM occurring during the relatively “cool” MIS-13 is addressed here by means of simulations with the climate model of intermediate complexity LOVECLIM Note that the Wang et al (2003) definition of the East Asia subtropical monsoon area is adopted throughout this article (105–140◦ E, 22.5–45◦ N)
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call