Westerlies Asia and monsoonal Asia: Spatiotemporal differences in climate change and possible mechanisms on decadal to sub-orbital timescales

The Holocene is probably the most intensively studied series/epoch within the geological record, and embodies a wide array of geomorphological, climatic, biotic and archaeological evidence; yet little attention has hitherto been paid to a formal subdivision of this series/epoch. Here we report a tripartite division of the Holocene into the Greenlandian, Northgrippian and Meghalayan stages/ages and their corresponding Lower/Early, Middle, Upper/Late subseries/subepochs, each supported by a Global Boundary Stratotype Section and Point (GSSP). The GSSP for the lowermost stage, the Greenlandian, is that of the Holocene as previously defined in the NGRIP2 Greenland ice core, and dated at 11,700 yr b2k (before 2000 CE). The GSSP for the Northgrippian is in the NGRIP1 Greenland ice core, and dated at 8236 yr b2k, whereas that for the Meghalayan is located in a speleothem from Mawmluh Cave, Meghalaya, northeast India with a date of 4250 yr b2k. The proposal on which this subdivision is based was submitted by the Subcommission on Quaternary Stratigraphy, approved by the International Commission on Stratigraphy, and formally ratified by the Executive Committee of the International Union of Geological Sciences on 14th June 2018.

Formal ratification of the subdivision of the Holocene Series/Epoch (Quaternary System/Period) : two new Global Boundary Stratotype Sections and Points (GSSPs) and three new stages/subseries.

Assessment of Climate Change over the Indian Region : A Report of the Ministry of Earth Sciences (MoES), Government of India

Stalagmite is one kind of secondary carbonates formed in limestone caves (speleothem). After cave water droplets containing Ca2+ and $$\rm{HCO}_3^-$$
 drip onto floor, carbonate in the water might become supersaturated due to CO2 degassing under certain conditions, resulting in the formation of stalagmite in a process year after year. Stalagmite is one of important geological archives for paleoclimate research. The advantages include wide spatial distribution, suitable for U-Th and U-Pb dating, enriched in climate proxies, continuity, long time span, comparability and lower sampling cost etc. These factors have propelled stalagmite paleoclimate research to the forefront of global paleoclimatology with an irreplaceable role. The stalagmite paleoclimate study started in the western countries, mainly in Europe and America in 1960s–1970s, while the relevant research in China was progressively developed in the 1980s–1990s after the Reform and Opening up. Although there was a huge gap between the overall research level in China and western countries, a solid research foundation, as well as a number of talent teams were established during the period. In the 21st century, starting from the publication of stalagmite records from Hulu Cave in Nanjing in 2001, the stalagmite paleoclimate research in China has ushered in a flourishing development and a real leap on the basis of international cooperation, resulting in significant international impacts. The landmark achievements, including establishment of the world’s longest (640000 years) East Asian monsoon stalagmite record, as well as the longest Indian monsoon (280000 years), South American monsoon (250000 years), North American westerly climate (330000 years), Central Asian westerly climate (135000 years), and northwestern China westerly climate (500000 years), have laid a milestone in the paleoclimate study in these climate domains. Importantly, these stalagmite records have revealed the relationship of Asian monsoon variations with solar insolation climate change in polar regions, and the South American monsoon changes on orbital-suborbital timescales, which have provided new geological observations for the development of orbital-suborbital climate theory; elaborated coupling and differentiation relationships between the Asian monsoon and the westerly climate; reconstructed the history of Asian monsoon changes in the Holocene in detail, and thus the hydrological and climate variances behind Chinese and Indian civilization-cultural evolutions. Furthermore, a large number of high-resolution stalagmite records over the past 2000 years have been reconstructed, which are important for understanding short-term climate variability and magnitude, events, cycles, and thus the future climate projection. The achievements have also involved the improvements of a number of important techniques, such as U-Th dating method, the establishments of various hydroclimatic proxies, as well as the contributions to the reconstruction of the atmosphere 14C variation history over the past ∼54000 years. On the perspective of the future, the Chinese stalagmite community should continue to develop key techniques, further clarify the hydroclimatic significance of stalagmite proxies, impel the integration of related disciplines, and concentrate on key scientific issues in global climate change and major social demands.

Chinese stalagmite paleoclimate researches: A review and perspective

. A large array of proxy records
suggests that the “4.2 ka event” marks an approximately
300-year long period ( ∼3.9 to 4.2 ka) of
major climate change across the globe. However, the climatic manifestation of
this event, including its onset, duration, and termination, remains less
clear in the Indian summer monsoon (ISM) domain. Here, we present new oxygen
isotope ( δ18O ) data from a pair of speleothems (ML.1 and ML.2)
from Mawmluh Cave, Meghalaya, India, that provide a high-resolution record of
ISM variability during a period ( ∼3.78 and 4.44 ka) that fully
encompasses the 4.2 ka event. The sub-annually to annually resolved ML.1
 δ18O record is constrained by 18 230Th dates with an
average dating error of ±13  years ( 2σ ) and a resolution of ∼40  years, which allows us to characterize the ISM variability with
unprecedented detail. The inferred pattern of ISM variability during the
period contemporaneous with the 4.2 ka event shares broad similarities and
key differences with the previous reconstructions of ISM from the Mawmluh
Cave and other proxy records from the region. Our data suggest that the ISM
intensity, in the context of the length of our record, abruptly decreased at
 ∼4.0  ka ( ∼ ± 13  years), marking the onset of a multi-centennial
period of relatively reduced ISM, which was punctuated by at least two
multi-decadal droughts between ∼3.9 and 4.0 ka. The latter stands out
in contrast with some previous proxy reconstructions of the ISM, in which the
4.2 ka event has been depicted as a singular multi-centennial drought.

/pdf/evaluating-the-timing-and-structure-of-the-4-2-ka-event-in-gzsp2s3euo.pdf

Evaluating the timing and structure of the 4.2 ka event in the Indian summer monsoon domain from an annually resolved speleothem record from Northeast India

The vast Indo-Gangetic Plain in South Asia has been home to some of the world’s oldest civilizations, whose fortunes ebbed and flowed with time—plausibly driven in part by shifts in the spatiotemporal patterns of the Indian summer monsoon rainfall. We use speleothem oxygen isotope records from North India to reconstruct the monsoon’s variability on socially relevant time scales, allowing us to examine the history of civilization changes in the context of varying hydroclimatic conditions over the past 5700 years. Our data suggest that significant shifts in monsoon rainfall have occurred in concert with changes in the Northern Hemisphere temperatures and the discharges of the Himalayan rivers. The close temporal relationship between these large-scale hydroclimatic changes and the intervals marking the significant sociopolitical developments of the Indus Valley and Vedic civilizations suggests a plausible role of climate change in shaping the important chapters of the history of human civilization in the Indian subcontinent.

The Indian monsoon variability and civilization changes in the Indian subcontinent

Along with economic development and technological innovation, rapid expansion of agricultural machinery has sparked widespread concern. In particular, the superiority of scrapped agricultural machinery recycling and remanufacturing in improving environmental sustainability, economic benefits, and carbon emission reduction has garnered public attention. Based on this reality, this study constructs models for five different agricultural machinery recycling channels according to different actors involved in recovery, dismantling, and remanufacturing. Each model’s equilibrium is determined by mathematical deduction. The applicable condition of each model and the influence of multiple factors are analyzed. The results indicate the following: (i) no single recycling channel is definitely superior to others, and different channels have their own applicable conditions that are influenced by transfer payments, supply chain cooperation, recycling prices, and supply and demand; (ii) cooperative scenarios are more conducive to attracting third-party enterprises to participate to increase supply chain revenue; (iii) rise in recovery and remanufacturing prices may lead to divergence among supply chain parties on channel selection; and (iv) oversupply requires government subsidies to maintain recycling and remanufacturing.

/pdf/channel-selection-of-closed-loop-supply-chain-for-scrapped-1qjcfwz1.pdf

Hangying Li

Papers

The Indian monsoon variability and civilization changes in the Indian subcontinent

Channel Selection of Closed-Loop Supply Chain for Scrapped Agricultural Machines Remanufacturing