Irreversible intensification of the East Asian winter monsoon and aridity in Asian interior linked to the uplifted Tibetan Plateau: Evidence from magnetoclimatology of the Xining loess since 1.3 Ma

Abstract

The impact of the uplifted Tibetan Plateau on the East Asian monsoon (EAM) evolution is not an uncontroversial topic. Disentangling complex paleoclimatic signals derived from solar insolation, global ice volume, and the rise of Tibetan Plateau in the EAM domain is challenging because of the paucity of continuous Quaternary sedimentary records shed from the Tibetan Plateau. The 260-m-thick Xining loess deposits in the northeastern Tibetan Plateau (NETP) with ultra-high average accumulation rate of ∼23 cm/ka during 0.2–1.3 Ma provide an excellent opportunity to delineate the long-term influence of the uplifted Tibetan Plateau on paleoclimatic variations in the western margin of the EAM. High-resolution grain size and mineral magnetic analyses for this unique record reveal a much more significant long-term increasing trend of the East Asian winter monsoon strength and aridification compared with those of typical loess records on the Chinese Loess Plateau, confirming that the uplifted Tibetan Plateau may play an important part in enhancing the EAM circulation and aridity of Asian interior under global cooling. It is further proposed that the negative correlation between physical erosion and chemical weathering in the NETP does not contradict the prevailing uplift-weathering hypothesis, but probably suggests a strong climate-silicate-weathering feedback in this tectonically active region. This result provides robust evidence that the existence of the NETP and adjacent topography exerts a profound impact on the irreversible intensification of Asian interior aridity.