The 3.6-Ma aridity and westerlies history over midlatitude Asia linked with global climatic cooling

Abstract

Midlatitude Asia (MLA), strongly influenced by westerlies-controlled climate, is a key source of global atmospheric dust, and plays a significant role in Earth’s climate system . However, it remains unclear how the westerlies, MLA aridity, and dust flux from this region evolved over time. Here, we report a unique high-resolution eolian dust record covering the past 3.6 Ma, retrieved from the thickest loess borehole sequence (671 m) recovered to date, at the southern margin of the Taklimakan desert in the MLA interior. The results show that eolian dust accumulation, which is closely related to aridity and the westerlies, indicates existence of a dry climate, desert area, and stable land surface, promoting continuous loess deposition since at least ∼3.6 Ma. This region experienced long-term stepwise drying at ∼2.7, 1.1, and 0.5 Ma, coeval with a dominant periodicity shift from 41-ka cyclicity to 100-ka cyclicity between 1.1 Ma and 0.5 Ma. These features match well with global ice volume variability both in the time and frequency domains (including the Mid-Pleistocene Transition), highlighting global cooling-forced aridity and westerlies climate changes on these timescales. Numerical modeling demonstrates that global cooling can dry MLA and intensify the westerlies, which facilitates dust emission and transport, providing an interpretive framework. Increased dust may have promoted positive feedbacks (e.g., decreasing atmospheric CO2 concentrations and modulating radiation budgets), contributing to further cooling. Unraveling the long-term evolution of MLA aridity and westerlies climate is an indispensable component of the unfolding mystery of global climate change.

Mineral Dust Coupled With Climate‐Carbon Cycle on Orbital Timescales Over the Past 4 Ma

“…In combination, these processes would have the effect of increasing dust outbreaks from the Asian interior due to strengthened aridification and less summer rainfall in Asian inland regions (Fang et al, 2020). As a result, the frequency and amplitude of Asian dust outbreaks deeply imprint the signal of expansion and contraction of the Arctic ice sheet, thus explaining the very similar orbital-scale variations of K and δ 18 O benthic (Figures 1a1 and 1c1).…”

“…Asian dust is a very important source of global dust, even being recorded in the Arctic ice cores; and is a key component of global dust circulation (e.g., Fang et al, 2020;Uno et al, 2009). Therefore, in this study, we use Asian dust flux as a representative of global dust flux in order to investigate the interaction processes between mineral dust fluxes, climate-cryosphere system, global carbon cycle, and orbital parameters over the past 4 Ma.…”

“…Since the late Miocene, the uplift of the Tibetan Plateau and coeval global cooling led to the disappearance of intermittent lakes and deepening desertification in the Tarim Basin of central Asia (Liu et al, 2020). Subsequently, accumulation of loess began at 3.6 Ma in the Western Kunlun (Fang et al, 2020). During the Quaternary, continued expansion of the Arctic ice sheet led to further enhancement of aridity in inland Asia, eventually prompting the formation of numerous deserts, including the present size of the Taklamakan Desert at 0.7-0.5 Ma (Liu et al, 2020), the Tengger Desert at ∼1 Ma (Li et al, 2014), the Kubuqi Desert at ∼1.3-1.17 Ma (Li et al, 2017), and the Badain Jaran Desert at ∼1.1 Ma (Wang et al, 2015).…”

Mineral magnetic properties of loess–paleosol couplets of northern Serbia over the last 1.0 Ma

“…For example, the pollen record of the central Chinese Loess Plateau (Chaona section) indicates major shifts in vegetation from forest–steppe to open forest–steppe at 0.95 Ma, and then to steppe at 0.5 Ma (Wu et al, 2004). Grain-size and dust-flux records from a loess core from midlatitude Asia on the southern margin of the Tarim basin reveal long-term stepwise increases at 1.1 Ma and 0.5 Ma (Fang et al, 2020), and that a stepwise expansion of the Mu Us Desert occurred at 1.1 Ma and 0.6 Ma (Ding et al, 1999).…”

Chronological and rock magnetic constraints on the transition of the Quaternary paleoclimate in the western Qaidam Basin, NE Tibetan Plateau

“…The most prominent climatic feature in central Asia is Quaternary desertification, such as the formation of the desert, the Yardangs, and the arid inland that covers the westerly dominated mid-latitude areas (Fig. 1; An et al, 2001; Zan et al, 2010; Kapp et al, 2011; Fang et al, 2020). This large east–west longitudinal distribution of arid lands in the Asian interior has long been thought to have a link with global cooling (Kutzbach et al, 1989; Raymo and Ruddiman, 1992; Felzer et al, 1995; Ramstein et al, 1997), the uplift of the Tibetan Plateau (Ruddiman and Kutzbach, 1989; Kutzbach et al, 1993; Molnar et al, 1993; Wang et al, 1999) and its interactions (Wang et al, 1999; An et al, 2001; Dupont-Nivet et al, 2007), and the retreat of the Para-Tethys Sea (Ramstein et al, 1997; Bosboom et al, 2011, 2014).…”