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Understanding millennial‐scale East Asian summer monsoon (EASM) variability is critical for climate projection in East Asia in the context of slowing Atlantic Meridional Overturning Circulation (AMOC) caused by global warming. This study performs two groups of sensitivity experiments at 8.2 and 4.2 ka BP, both forced by the same North Atlantic freshwater hosing and corresponding orbital parameters using the Community Earth System Model, to explore the orbital effect on millennial‐scale EASM variability. Our simulations reveal that EASM variability differs significantly between these two cold events. During the 8.2 ka BP (4.2 ka BP) (0 BP = 1950 AD) cold event, North Atlantic freshwater forcing weakens the EASM, generating a meridional tripole (dipole) pattern of EASM precipitation anomalies. Furthermore, the same freshwater discharge causes a greater decline in the EASM, contrasting to a slight weaker AMOC slowdown, at 4.2 ka BP than at 8.2 ka BP. This suggests orbital parameters significantly influence the EASM response to North Atlantic cold events. The East Asian subtropical westerly jet, whose meridional position and intensity are controlled by summer insolation on an orbital timescale, plays a key role in this orbital effect. The westerly jet's meridional position determines the spatial pattern of EASM precipitation anomalies, while its intensity affects the amplitude of the EASM's response to freshwater forcing. Because of a larger EASM decline due to freshwater hosing with lower summer insolation, we anticipate a profound declining EASM precipitation in the future with low summer insolation if the AMOC continues to weaken. Key Points: Millennial‐scale East Asian summer monsoon (EASM) variability is modulated by Earth's orbital parametersThe EASM weakens more pronounced in response to North Atlantic freshwater forcing under lower summer insolationSummer insolation influences the EASM response to North Atlantic freshwater forcing via the westerly jet [ABSTRACT FROM AUTHOR]

In the East Asian monsoon region, Chinese speleothem δ18O records exhibit a maximum monsoon strength during the early Holocene. However, other proxy data from lakes or loess, interpreted as monsoon rainfall, show a mid‐Holocene monsoon optimum. This discrepancy may come from specific climate interpretation of different proxies. Here we report multiproxy records from a single loess–palaeosol sequence at Yulin in the monsoon marginal northern China, based on an independent and high‐precision chronology. Our long‐chain n‐alkane δD values, together with related biomarker proxies including the average chain length and concentration of long‐chain n‐alkanes, reveal a weakening trend in monsoon strength and less woody vegetation since ~6 ka. However, other soil formation‐related proxies, such as magnetic susceptibility, grain‐size distribution and total organic carbon, show a decreasing trend since 4–3 ka. We find that monsoon and vegetation are controlled by insolation variation, while soil formation is more related to temperature and humidity changes. Our multiple proxy comparison reveals different controlling mechanisms leading to different interpretations in monsoon, vegetation and soil formation reconstructions. This finding suggests that previous debates on Holocene monsoon changes in East Asia probably stem from the specific proxy interpretation. [ABSTRACT FROM AUTHOR]

Paleoclimatic records reveal spatially asynchronous changes of East Asian summer monsoon (EASM) precipitation during the Holocene, but the underlying mechanisms are not fully understood. This study explores the role of the zonal shift of the Asian westerly jet (AWJ) core on the spatial‐temporal variability of EASM precipitation based on Holocene climate simulations using the KCM and CESM forced by orbital variations. We analyzed the composite differences of summer precipitation and associated atmospheric circulations between the early (middle) and middle (late) Holocene. Simulations suggest a dipole pattern of summer precipitation with increasing (decreasing) precipitation in central (southern) China from the early to late Holocene, which was shaped by the eastward shift of the AWJ core. The eastward shift of the AWJ core and the accompanied eastward movement of the upper‐level convergence over the AWJ's right exit region weakened the low‐level downward motions over central China. Meanwhile, the low‐level upward motions over southern China were weakened by the concurrent eastward (westward) migration of the South Asian High (western Pacific subtropical High) during the Holocene. Consequently, summer precipitation increased (decreased) in central (southern) China from the early to late Holocene. The eastward shift of the AWJ core was primarily driven by amplified meridional insolation gradient at middle latitudes via strengthening upper‐level westerly intensity during the Holocene. In addition, land cover difference between East Asia and central Asia caused a greater enhancement of westerlies intensity in East Asia, further modulating the eastward movement of the AWJ core during the Holocene. Key Points: Our simulations reveal a dipole pattern of summer precipitation between central and southern China during the HoloceneThe dipole precipitation pattern was strongly modulated by zonal shift of the Asian westerly jet coreInsolation variation and land cover caused the eastward shift of the Asian westerly jet core during the Holocene [ABSTRACT FROM AUTHOR]

The lack of a precisely-dated, unequivocal climate proxy from northern China, where precipitation variability is traditionally considered as an East Asian summer monsoon (EASM) indicator, impedes our understanding of the behaviour and dynamics of the EASM. Here we present a well-dated, pollen-based, ~20-yr-resolution quantitative precipitation reconstruction (derived using a transfer function) from an alpine lake in North China, which provides for the first time a direct record of EASM evolution since 14.7 ka (ka = thousands of years before present, where the 'present' is defined as the year AD 1950). Our record reveals a gradually intensifying monsoon from 14.7-7.0 ka, a maximum monsoon (30% higher precipitation than present) from ~7.8-5.3 ka, and a rapid decline since ~3.3 ka. These insolation-driven EASM trends were punctuated by two millennial-scale weakening events which occurred synchronously to the cold Younger Dryas and at ~9.5-8.5 ka, and by two centennial-scale intervals of enhanced (weakened) monsoon during the Medieval Warm Period (Little Ice Age). Our precipitation reconstruction, consistent with temperature changes but quite different from the prevailing view of EASM evolution, points to strong internal feedback processes driving the EASM, and may aid our understanding of future monsoon behaviour under ongoing anthropogenic climate change. [ABSTRACT FROM AUTHOR]

• Single grain K-feldspar pIR 50 IR 170 dating effectively dates samples over past 1 kyr. • Highest lake levels in Qaidam Basin over past 1 kyr during Little Ice Age. • Out-of-phase Central and East Asian precipitation drive asynchronous lake change. • EASM did not penetrate as far inland as Qaidam Basin during past 1 kyr. The moisture and precipitation evolution of mid-latitude Asia are dominated by the East Asian summer monsoon (EASM) and mid-latitude Westerlies atmospheric systems. How these two systems interacted along their transition zone in the northern Tibetan Plateau remains unclear, especially over centennially to millennial timescales. This study investigates moisture evolution along the EASM-Westerlies transition zone using 10 Late Holocene paleolake shorelines from Toson Lake in the northern Tibetan Plateau. Shorelines are dated using a newly developed single-grain post infrared-infrared stimulated luminescence (pIR 50 IR 170) dating protocol for 14,500 K-feldspar grains and used to reconstruct the evolution of Toson Lake over the past millennium. Results show that Toson Lake was stable during the Medieval Warm Period (MWP), expanded during the Little Ice Age (LIA) with a distinct highstand from AD1600–1700 punctuated by short-duration low period at ∼ CE 1650. After which, Toson Lake dramatically contracted into the Current Warm period (CWP). Lake level changes are consistent with Westerlies precipitation variability across Central Asia, in contrast to records from the EASM dominated northeastern Tibetan Plateau and northern China documenting an arid LIA and wet MWP. Reanalysis of modern climatic data are combined with our lake chronology to reveal that although EASM strength influences precipitation variability across northeastern Tibetan Plateau (NETP) and northern China, EASM precipitation has not directly penetrated deep inland over the past millennium. Instead, Westerlies moisture, modulated by the see-saw of the North Atlantic Oscillation, together with the moisture controlled by the anticyclonic circulation over Mongolia and negatively related to the EASM strength, dominated water vapour transport to the mid-latitudes of Central Asia. Out-of-phase moisture transport and interaction between the Westerlies and EASM drives asynchronous lake evolution between Central and East Asia over centennial-millennial timescales. [ABSTRACT FROM AUTHOR]

• K-feldspar pIRIR dating can be used to date loess up to 250 ka in arid central Asia. • The lowland areas of central Asia are generally arid during the past 250 ka. • Ice volume controls glacial-interglacial moisture in-phase changes across Asia. • Interglacial moisture in ACA has an out of phase relation to that in East Asia. • Precessional forcing drove this out of phase relation over ACA and East Asia. Desertification is of pressing environmental concern in large parts of Asia and directly affects millions of people. Arid Central Asia (ACA) in particular is highly sensitive to desertification and environmental change. Climate change in ACA may be driven by westerly circulation or monsoon variation. However, no consensus exists over their relative importance during the Quaternary and this greatly restricts our understanding of how this region may be affected by future climate change. Here we use the most detailed luminescence dating age model yet produced for ACA for three loess records in the Tianshan Mountains spanning the past 250 ka to show a sharp dichotomy in moisture variation between lowland and high mountain areas. The lowland areas of ACA are subjected to persistent aridity during past 250 ka, while highland areas clearly show dry-glacial and moist-interglacial changes, synchronous to moisture variability in monsoonal East Asia, and both co-varying with global ice volume and greenhouse gas (GHG) variation. In contrast, moisture variability across ACA within interglacials varies inversely with insolation-driven precessional changes. This is directly out of phase with the moisture changes of East Asia, which co-vary with precessional insolation changes, and indicates the influence of Westerly circulation in ACA. Our Flexible Global Ocean-Atmosphere-Land System model simulations further reveal that coupled ice volume and GHG variations dominated climatic variability in both ACA and East Asia over glacial-interglacial cycles. However, the out of phase relationship between the intensity of the Westerly and East Asian monsoon systems during interglacial periods indicates that precessional forcing is responsible for differences in moisture patterns between ACA and East Asia. These observations indicate that moisture levels will not increase even in high altitude regions of ACA over the next several millennia; rather desertification is likely to worsen resulting from stabilization of the Westerlies as a result of low summer insolation. [ABSTRACT FROM AUTHOR]