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The Holocene is the current geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene together form the Quaternary period. The Holocene is an interglacial period within the ongoing glacial cycles of the Quaternary, and is equivalent to Marine Isotope Stage 1.
The Younger Dryas (YD) was a period in Earth's geologic history that occurred circa 12,900 to 11,700 years Before Present (BP), at the end of the Pleistocene epoch. It is named after the alpine–tundra wildflower Dryas octopetala, because its fossils are abundant in the European sediments dating to this timeframe. The two earlier geologic periods where this flower was abundant in Europe are the Oldest Dryas and Older Dryas, respectively. The Younger Dryas ended when the entire globe had warmed consistently, which marks the beginning of the current Holocene epoch.
A monsoon is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with annual latitudinal oscillation of the Intertropical Convergence Zone (ITCZ) between its limits to the north and south of the equator. Usually, the term monsoon is used to refer to the rainy phase of a seasonally changing pattern, although technically there is also a dry phase. The term is also sometimes used to describe locally heavy but short-term rains.
A loess is a clastic, predominantly silt-sized sediment that is formed by the accumulation of wind-blown dust. Ten percent of Earth's land area is covered by loesses or similar deposits.
Before Present (BP) or "years before present (YBP)" is a time scale used mainly in archaeology, geology, and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because the "present" time changes, standard practice is to use 1 January 1950 as the commencement date (epoch) of the age scale. The abbreviation "BP" has been interpreted retrospectively as "Before Physics", which refers to the time before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere, which scientists must account for.
The Holocene Climate Optimum (HCO) was a warm period in the first half of the Holocene epoch, that occurred in the interval roughly 9,500 to 5,500 years BP, with a thermal maximum around 8000 years BP. It has also been known by many other names, such as Altithermal, Climatic Optimum, Holocene Megathermal, Holocene Optimum, Holocene Thermal Maximum, Hypsithermal, and Mid-Holocene Warm Period.
Lajia is a Bronze Age archaeological site in the upper reaches of the Yellow River, on the border between the Chinese provinces of Gansu and Qinghai. As at other sites of the Qijia culture, the people of Lajia had an agricultural economy based primarily on millet cultivation and sheep herding. They also kept pigs for use in ritual activities, including making oracle bones, and experimented with a high temperature-fired pottery described as proto-porcelain. The world's oldest known noodles were discovered at the site in 2005.
The East Asian monsoon is a monsoonal flow that carries moist air from the Indian Ocean and Pacific Ocean to East Asia. It affects approximately one-third of the global population, influencing the climate of Japan, the Korean Peninsula, Taiwan, China, the Philippines and Mainland Southeast Asia but most significantly Vietnam. It is driven by temperature differences between the East Asian continent and the Pacific Ocean. The East Asian monsoon is divided into a warm and wet summer monsoon and a cold and dry winter monsoon. This cold and dry winter monsoon is responsible for the aeolian dust deposition and pedogenesis that resulted in the creation of the Loess Plateau. The monsoon influences weather patterns as far north as Siberia, causing wet summers that contrast with the cold and dry winters caused by the Siberian High, which counterbalances the monsoon's effect on northerly latitudes.
The 4.2-kiloyear BP aridification event, also known as the 4.2 ka event, was one of the most severe climatic events of the Holocene epoch. It defines the beginning of the current Meghalayan age in the Holocene epoch.
In climatology, the 8.2-kiloyear event was a sudden decrease in global temperatures that occurred approximately 8,200 years before the present, or c. 6,200 BC, and which lasted for the next two to four centuries. It defines the start of the Northgrippian age in the Holocene epoch. The cooling was significantly less pronounced than during the Younger Dryas cold period that preceded the beginning of the Holocene. During the event, atmospheric methane concentration decreased by 80 ppb, an emission reduction of 15%, by cooling and drying at a hemispheric scale.
The Piora Oscillation was an abrupt cold and wet period in the climate history of the Holocene Epoch; it is roughly dated to c. 3900-3000 BC. Some researchers associate the Piora Oscillation with the end of the Atlantic climate regime, and the start of the Sub-Boreal, in the Blytt–Sernander sequence of Holocene climates.
Bond events are North Atlantic ice rafting events that are tentatively linked to climate fluctuations in the Holocene. Eight such events have been identified. Bond events were previously believed to exhibit a roughly c. 1,500-year cycle, but the primary period of variability is now put at c. 1,000 years.
Owing to tremendous differences in latitude, longitude, and altitude, the climate of China is extremely diverse. It ranges from tropical in the far south to subarctic in the far north, and alpine in the higher elevations of the Tibetan Plateau. Monsoon winds, caused by differences in the heat-absorbing capacity of the continent and the ocean, dominate the climate. During the summer, the East Asian Monsoon carries warm and moist air from the south and delivers the vast majority of the annual precipitation in much of the country. Conversely, the Siberian anticyclone dominates during winter, bringing cold and comparatively dry conditions. The advance and retreat of the monsoons account, in large degree, for the timing of the rainy season throughout the country. Although most of the country lies in the temperate belt, its climatic patterns are complex.
Zhuye Lake is the terminal lake of the Shiyang River, which is located in the east of the Hexi Corridor in Gansu Province, China. Zhuye Lake is located in the marginal area of the Asian monsoon and is affected by both the Asian monsoon system and the Westerly jet. By understanding the Holocene record in Zhuye Lake, the interaction of different climate systems during the Holocene can be studied. At the same time, the Asian monsoon system is climatically dynamic; changes in its sphere of influence can result in severe drought or flood over large, densely populated, regions. In addition, Zhuye Lake and the surrounding area in arid NW China are in ecological imbalance – a consequence of human impacts and climate. Understanding the environmental history here can assist climatological forecasting of the Asian monsoon system and ecosystem reconstruction.
Minze Stuiver was a Dutch geochemist who was at the forefront of geoscience research from the 1960s until his retirement in 1998. He helped transform radiocarbon dating from a simple tool for archaeology and geology to a precise technique with applications in solar physics, oceanography, geochemistry, and carbon dynamics. Minze Stuiver's research encompassed the use of radiocarbon (14C) to understand solar cycles and radiocarbon production, ocean circulation, lake carbon dynamics and archaeology as well as the use of stable isotopes to document past climate changes.
Rengaswamy Ramesh (1956–2018) was an Indian climatologist, oceanographer, a former Prof. Satish Dhawan Professor at the Physical Research Laboratory and a senior professor at the National Institute of Science Education and Research, Bhubaneswar. He was known for paleo-climatic and paleo-oceanographic studies and was an elected fellow of all the three major Indian science academies viz. Indian National Science Academy, Indian Academy of Sciences, and the National Academy of Sciences, India as well as of The World Academy of Sciences. The Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, one of the highest Indian science awards for his contributions to Earth, Atmosphere, Ocean and Planetary Sciences in 1998.
The African humid period is a climate period in Africa during the late Pleistocene and Holocene geologic epochs, when northern Africa was wetter than today. The covering of much of the Sahara desert by grasses, trees and lakes was caused by changes in the Earth's axial tilt; changes in vegetation and dust in the Sahara which strengthened the African monsoon; and increased greenhouse gases. During the preceding Last Glacial Maximum, the Sahara contained extensive dune fields and was mostly uninhabited. It was much larger than today, and its lakes and rivers such as Lake Victoria and the White Nile were either dry or at low levels. The humid period began about 14,600–14,500 years ago at the end of Heinrich event 1, simultaneously to the Bølling–Allerød warming. Rivers and lakes such as Lake Chad formed or expanded, glaciers grew on Mount Kilimanjaro and the Sahara retreated. Two major dry fluctuations occurred; during the Younger Dryas and the short 8.2 kiloyear event. The African humid period ended 6,000–5,000 years ago during the Piora Oscillation cold period. While some evidence points to an end 5,500 years ago, in the Sahel, Arabia and East Africa, the end of the period appears to have taken place in several steps, such as the 4.2-kiloyear event.
The Medieval Warm Period (MWP), also known as the Medieval Climate Optimum or the Medieval Climatic Anomaly, was a time of warm climate in the North Atlantic region that lasted from c. 950 to c. 1250. Climate proxy records show peak warmth occurred at different times for different regions, which indicate that the MWP was not a globally uniform event. Some refer to the MWP as the Medieval Climatic Anomaly to emphasize that climatic effects other than temperature were also important.
Stephen Cummings Porter was an American geologist who taught in the department of Geological Sciences and directed the Quaternary Research Center at the University of Washington. He was chief editor of the journal Quaternary Research from 1976 until his retirement in 2001. He died in 2015 at the age of 80.
Paula Jo Reimer is a radiocarbon and archaeological scientist. Reimer is the former director of the 14Chrono Centre for Climate, the Environment, and Chronology at Queen's University Belfast.
References
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- ↑ Zhou, Weijian; Donahue, Douglas J.; Porter, Stephen C.; Jull, Timothy A.; Xiaoqiang, Li; Stuiver, Minze; Zhisheng, An; Matsumoto, Eiji; Guangrong, Dong (November 1996). "Variability of Monsoon Climate in East Asia at the End of the Last Glaciation". Quaternary Research. 46 (3): 219–229. Bibcode:1996QuRes..46..219W. doi:10.1006/qres.1996.0062. S2CID 129650707.
- ↑ Zhou, Weijian; Donahue, Douglas; Jull, A. J. T. (1997). "Radiocarbon AMS Dating of Pollen Concentrated from Eolian Sediments: Implications for Monsoon Climate Change Since the Late Quaternary". Radiocarbon. 39 (1): 19–26. Bibcode:1997Radcb..39...19Z. doi: 10.1017/S0033822200040868 .
- ↑ Jensen, Mari N. (2018-05-24). "Dusty Rainfall Records Reveal New Understanding of Climate". University of Arizona News. Retrieved 2021-08-17.
- ↑ Beck, J. Warren; Zhou, Weijian; Li, Cheng; Wu, Zhenkun; White, Lara; Xian, Feng; Kong, Xianghui; An, Zhisheng (2018-05-25). "A 550,000-year record of East Asian monsoon rainfall from 10 Be in loess". Science. 360 (6391): 877–881. doi: 10.1126/science.aam5825 . ISSN 0036-8075. PMID 29798878. S2CID 44104395.
- ↑ Wu, Shugang; Zhou, Weijian; Xiong, Xiaohu; Burr, G.S.; Cheng, Peng; Wang, Peng; Niu, Zhenchuan; Hou, Yaoyao (2021). "The impact of COVID-19 lockdown on atmospheric CO2 in Xi'an, China". Environmental Research. 197: 111208. doi:10.1016/j.envres.2021.111208. PMC 8061636 . PMID 33895110.
- ↑ "Division of Earth Sciences---Academic Divisions of the Chinese Academy of Sciences". english.casad.cas.cn. Retrieved 2021-08-17.