Knowledge of the past variability of climate at high northern latitudes during astronomical analogues of the present interglacial may help to inform our understanding of future climate change. Unfortunately, long-term continuous records of ice-sheet variability in the Northern Hemisphere only are scarce because records of benthic 18O content represent an integrated signal of changes in ice volume in both polar regions. However, variations in Northern Hemisphere ice sheets influence the Siberian High (an atmospheric pressure system), so variations in the East Asian winter monsoon (EAWM)—as recorded in the aeolian dust deposits on the Chinese Loess Plateau—can serve as a useful proxy of Arctic climate variability before the ice-core record begins. Here we present an EAWM proxy record using grain-size variations in two parallel loess sections representative of sequences across the whole of the Chinese Loess Plateau over the past 900,000 years. The results show that during periods of low eccentricity and precessional variability at approximately 400,000-year intervals, the grain-size-inferred intensity of the EAWM remains weak for up to 20,000 years after the end of the interglacial episode of high summer monsoon activity and strong pedogenesis. In contrast, there is a rapid increase in the EAWM after the end of most other interglacials. We conclude that, for both the 400,000-year interglacials, the weak EAWM winds maintain a mild, non-glacial climate at high northern latitudes for much longer than expected from the conventional loess and marine oxygen isotope records. During these times, the less-severe summer insolation minima at 65° N (ref. 4) would have suppressed ice and snow accumulation, leading to a weak Siberian High and, consequently, weak EAWM winds.

Delayed build-up of Arctic ice sheets during 400, 000-year minima in insolation variability confirmed by Chinese loess

Chemical weathering is an important process that controls the evolution of the Earth’s surface. By accurately and reliably estimating the intensity of chemical weathering, we can improve our understanding of the processes occurring at the Earth’s surface as well as environmental changes. However, chemical weathering indices, which are influenced by source rocks and grain size, may not always accurately reflect the intensity of chemical weathering. Therefore, the use of chemical weathering indices to reliably reflect the changes in the intensity of chemical weathering in deserts remains uncertain. In this study, several chemical weathering indices, including the chemical index of alteration, Parker’s weathering index, chemical index of weathering, plagioclase index of alteration, chemical proxy of alteration, Rb/Sr, and αAlE indices, were calculated for 521 eolian sand samples collected from across twelve deserts in northern China. The results show that, for all the chemical weathering indices, eolian sands from the different deserts differed significantly. Rather than the climatic conditions in the studied deserts. factors such as source rocks and grain size had a larger impact on these indices. These indices cannot generally be used to reflect the intensity of chemical weathering. However, results showed that when the mean annual precipitation varies greatly between deserts, the changes in the WIP values of the fine fraction samples (

Applicability of chemical weathering indices of eolian sands from the deserts in northern China

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2020GL088950

Machine Learning for Source Identification of Dust on the Chinese Loess Plateau

Variations of the East Asian monsoon over the past 800 kyr constrained by the boron isotope composition of paleo-rainwater inferred from loess-paleosol deposits in NE China

The periodicity and forcing mechanism of the past East Asian summer monsoon (EASM) precipitation are the natural background for predicting future precipitation changes, but they are controversial and intensely debated. Here, we present a high-resolution EASM precipitation record reconstructed from the loess redness in North China over the past 720 kyr. The average precipitation for interglacials is 420 mm/yr, higher than present (~280 mm/yr). Combing through our EASM records and previously published data exhibits a dominated periodicity of 100 kyr on the orbital timescale, and thus supports the hypothesis of high-latitude climate forcing. More importantly, we found the precession cycle appears only after the Mid-Brunhes Transition (MBT, ~430 ka) in the EASM records and it follows the global ice volume prior to the MBT in the interglacials interiors. We argue that during the post-MBT interglacials, abruptly appearing Arctic perennial sea ice resulted southward shift of the Northern Hemisphere Westerlies jet, thereby decreasing the EASM precipitation in North China. This suggests that the precession rhythm in the EASM possibly is a result of Arctic perennial sea ice or Northern Hemisphere ice sheets changes. In the warm Marine Isotope Stages (MIS) 5e and 11e, the strongest EASM precipitation may be related to the strengthening of the moisture transport from the warming tropical ocean. Therefore, the variation of the mid-latitude EASM precipitation intensity during the interglacial interiors is the integrated effect between the North Hemisphere high latitude ice volume and low latitude climate changes.

Significant influence of Northern Hemisphere high latitude climate on appeared precession rhythm of East Asian summer monsoon after Mid-Brunhes Transition interglacials recorded in the Chinese loess

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2018GL081551

Wancang Zhao

Papers

Significant influence of Northern Hemisphere high latitude climate on appeared precession rhythm of East Asian summer monsoon after Mid-Brunhes Transition interglacials recorded in the Chinese loess

Distant Taklimakan Desert as an Important Source of Aeolian Deposits on the Chinese Loess Plateau as Evidenced by Carbonate Minerals