the last two millennia
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2022 ◽  
pp. 235-259
Author(s):  
Elhoucine Essefi ◽  
Soumaya Hajji ◽  
Mohamed Ali Tagorti

The Sidi El Hani Wetland is located in Eastern Tunisia. It represents the natural outlet of an endorheic system, Mechertate-Chrita-Sidi El Hani, and it collects all the eroded sediment from this watershed. In this chapter, the visual core description focused on three reference sandy bands and on the concept of grey scale variability in order to infer the clay pan response to the climatic variability and erosion during the last two millennia. First, in the uppermost part, the stage Warming Present (WP) stretches from (1954-80= 1874) to 1993, i.e. ≈120yrs; the establishment of modern conditions is characterized by stable conditions with high grey scale. Added to a small salt crust, this period is dominated by a clayey sedimentation. Second, the stage C4 is called the Late Little Ice Age (Late LIA); it stretches between the 80yrBP and 400yrBP, i.e., 320yrs. It is characterized by intermediate GS values; the clayey sedimentation makes up the twofold and threefold laminates. Based on laser granulometer, the genetic approach shows the interplay of eolian and hydraulic erosion.


Author(s):  
Anna Agatova ◽  
◽  
Roman Nepop ◽  
Igor Slyusarenko ◽  
Piotr Moska ◽  
...  

Multidisciplinary studies of various natural archives indicate contrasting changes in the human habitat in the high-mountainous southeastern part of the Russian Altai during the last 20,000 years. This period includes the final stage of the last glaciation and its degradation, the formation of the last giant ice-dammed lakes in the intermountain basins and their cataclysmic draining, considerable transformation of glacial landscapes to modern diverse and mosaic structure. Warmer and more humid climate in the first half of the Holocene was followed by cooling and repeated advances of mountain glaciers. The general trend to cooling and aridization in the second half of the Holocene is the most pronounced during the last two millennia. Deglaciation and final drying of intermountain basins boosted a renovation of the local ecosystems and established an environmental baseline of human occupation in the region. The arid climate, widespread permafrost and low population density determined a good preservation of archaeological heritage in the region, which is located at the crossroad between East and West, North and South. This paper presents the analysis of previously published and new data including newly obtained 14C and OSL dates, which allow to correlate climatically driven landscape transformations with habitat of ancient communities and cultures shifting in the region during the last 20, 000 years, as well as to assess the anthropogenic impact on the environment.


2021 ◽  
Author(s):  
Valdir Novello ◽  
Francisco Cruz ◽  
Mathias Vuille ◽  
Jose Campos ◽  
Nicolas Strikis ◽  
...  

2021 ◽  
pp. 1-16
Author(s):  
Xiner Wu ◽  
Anne de Vernal ◽  
Bianca Fréchette ◽  
Matthias Moros ◽  
Kerstin Perner

Abstract Climate changes over the past two millennia in the central part of the Gulf of St. Lawrence are documented in this paper with the aim of determining and understanding the natural climate variability and the impact of anthropogenic forcing at a regional scale. The palynological content (dinocysts, pollen, and spores) of the composite marine sediment core MSM46-03 collected in the Laurentian Channel was used to reconstruct oceanographic and climatic changes with a multidecadal temporal resolution. Sea-surface conditions, including summer salinity and temperature, sea-ice cover, and primary productivity, were reconstructed from dinocyst assemblages. Results revealed a remarkable cooling trend of about 4°C after 1230 cal yr BP (720 CE) and a culmination with a cold pulse dated to 170–40 cal yr BP (1780–1910 CE), which likely corresponds to the regional signal of the Little Ice Age. This cold interval was followed by a rapid warming of about 3°C. In the pollen assemblages, the decrease of Pinus abundance over the past 1700 yr suggests changes in wind regimes, likely resulting from increased southerly incursions of cold and dry Arctic air masses into southeastern Canada.


2021 ◽  
Vol 268 ◽  
pp. 107115
Author(s):  
Marco Roman ◽  
David B. McWethy ◽  
Natalie M. Kehrwald ◽  
Evans Osayuki Erhenhi ◽  
Amy E. Myrbo ◽  
...  

2021 ◽  
Vol 18 (13) ◽  
pp. 4185-4209
Author(s):  
Ramesh Glückler ◽  
Ulrike Herzschuh ◽  
Stefan Kruse ◽  
Andrei Andreev ◽  
Stuart Andrew Vyse ◽  
...  

Abstract. Wildfires, as a key disturbance in forest ecosystems, are shaping the world's boreal landscapes. Changes in fire regimes are closely linked to a wide array of environmental factors, such as vegetation composition, climate change, and human activity. Arctic and boreal regions and, in particular, Siberian boreal forests are experiencing rising air and ground temperatures with the subsequent degradation of permafrost soils leading to shifts in tree cover and species composition. Compared to the boreal zones of North America or Europe, little is known about how such environmental changes might influence long-term fire regimes in Russia. The larch-dominated eastern Siberian deciduous boreal forests differ markedly from the composition of other boreal forests, yet data about past fire regimes remain sparse. Here, we present a high-resolution macroscopic charcoal record from lacustrine sediments of Lake Khamra (south-west Yakutia, Siberia) spanning the last ca. 2200 years, including information about charcoal particle sizes and morphotypes. Our results reveal a phase of increased charcoal accumulation between 600 and 900 CE, indicative of relatively high amounts of burnt biomass and high fire frequencies. This is followed by an almost 900-year-long period of low charcoal accumulation without significant peaks likely corresponding to cooler climate conditions. After 1750 CE fire frequencies and the relative amount of biomass burnt start to increase again, coinciding with a warming climate and increased anthropogenic land development after Russian colonization. In the 20th century, total charcoal accumulation decreases again to very low levels despite higher fire frequency, potentially reflecting a change in fire management strategies and/or a shift of the fire regime towards more frequent but smaller fires. A similar pattern for different charcoal morphotypes and comparison to a pollen and non-pollen palynomorph (NPP) record from the same sediment core indicate that broad-scale changes in vegetation composition were probably not a major driver of recorded fire regime changes. Instead, the fire regime of the last two millennia at Lake Khamra seems to be controlled mainly by a combination of short-term climate variability and anthropogenic fire ignition and suppression.


Author(s):  
Z. Daulet Singh

The article is based on the author’s most recent book Powershift: India-China Relations in a Multipolar World (2020). It retraces the most salient moments and episodes in the India China border issue ever since the crisis broke out in 1959. What we learn from history is Chinese leaders have often shaped their policy on India as part of a wider geopolitical calculus, typically linked to the degree of pressure Chinese perceive on other geopolitical fronts. For India too, the nature of great powers relations impacts how it formulates China policy. This basic framework has remained relevant until the present day.Over the past decade, as the world order began shifting to a multipolar balance of power, India and China have confronted challenges in their relationship. The relationship is at a crossroad, and both Delhi and Beijing are struggling to find an equilibrium that allows both sides to pursue their interests and visions. Nevertheless, as Asia is returning to what it was for 1,800 years of the last two millennia, and, it is that big picture trend that Indian and Chinese leaders must pay attention to. Ultimately, this means stabilising India China relations


2021 ◽  
Author(s):  
Perry Zurn ◽  
Dale Zhou ◽  
David M. Lydon-Staley ◽  
Danielle S Bassett

Most theories of curiosity emphasize the acquisition of information. Such conceptualizations focus on the actions of the knower in seeking units of knowledge. Each unit is valued as an unknown and appropriated in becoming known. Yet, recent advances across a range of disciplines from philosophy to cognitive science suggest that it may be time to complement the acquisitional theory of curiosity with a connectional theory of curiosity. This alternative perspective focuses on the actions of the knower in seeking relations among informational units, laying down lines of intersection, and thereby building a scaffold or network of knowledge. Intuitively, curiosity becomes edgework. In this chapter, we dwell on the notion of edgework, wrestle with its relation to prior accounts, and exercise its unique features to craft alternative reasons for curiosity's value to humanity. To begin, we engage in a philosophical discussion of the evidence for connectional curiosity across the last two millennia in the Western intellectual tradition. We then move to a contemporary operationalization of connectional curiosity in the mathematical language of network science. To make our discussion more concrete, we walk through a case study of humans browsing Wikipedia. The groundwork laid, we turn to the practical question of how (if at all) the paradigm of curiosity as edgework manifests in the contemporary lives of humans today. Does such a conceptualization help us to better understand the relations between curiosity and mental health? Might the edgework paradigm explain the drive to build specific structures of knowledge? Would the account help us to encode, test, and validate existing theories of curiosity, or propose new ones? Could it clarify why and how our culture values curiosity, in its multiple manifestations, plethora of practices, and kindred kinds in many bodies? In considering interdisciplinary answers to these questions, we find that the notion of edgework offers a fresh, flexible, and explanatory account of curiosity. More broadly, it uncovers new opportunities to use the lens of science to examine, probe, and interrogate this important dimension of the human experience.


2021 ◽  
Author(s):  
Upasana S. Banerji ◽  
Ravi Bhushan ◽  
Kumar Batuk Joshi ◽  
Jithu Shaji ◽  
A. J. Timothy Jull

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