Cloud dynamic contribution to high-elevation peatland growth during the Holocene (Escalerani, Central Andes, Bolivia)

The Holocene ◽  
2018 ◽  
Vol 28 (8) ◽  
pp. 1334-1344 ◽  
Author(s):  
Katerine Escobar-Torrez ◽  
Teresa Ortuño ◽  
Ilham Bentaleb ◽  
Marie-Pierre Ledru
Keyword(s):  
Amazon Basin ◽  
Environmental Changes ◽  
Rainfall Variability ◽  
High Elevation ◽  
Annual Rainfall ◽  
Global Changes ◽  
Lake Titicaca ◽  
Climate Conditions ◽  
The Holocene ◽  
Wet Climate

Changes in climate conditions during the Holocene are documented in different parts of South America, showing contrasting responses to global changes. This study was conducted in the wet puna at an elevation of 4040 m a.s.l. on the eastern side of the Cordillera Real in Bolivia near Lake Titicaca. Pollen, charcoal, and stable isotopes in a sediment core collected in the peatland of Escalerani were analyzed. Results revealed environmental changes during the past 7500 yr BP, with an increase in wet climate conditions from 5900 to 4700 cal. yr BP and 3500 to 1300 cal. yr BP, and two dry periods between 4700 and 3500 cal. yr BP and 1300 to 560 cal. yr BP. Changes in hydrological conditions ranged from local changes because of glacier melting to regional changes in annual rainfall variability, related to South American monsoon activity. Moreover, our results highlight the importance of cloud convective activity from the Amazon basin along the adiabatic gradient, which maintained moist conditions at high elevations even during the mid-Holocene dry phase. The last 70 years have been characterized by the degradation of the peatland because of human activity.

scholarly journals Likely Ranges of Climate Change in Bolivia

2013 ◽  
Vol 52 (6) ◽  
pp. 1303-1317 ◽  
Author(s):  
Christian Seiler ◽  
Ronald W. A. Hutjes ◽  
Pavel Kabat
Keyword(s):  
Climate Change ◽  
Amazon Basin ◽  
Rainfall Variability ◽  
Annual Rainfall ◽  
Amazon Forest ◽  
Climate Change Scenarios ◽  
Wet Season ◽  
Global Circulation Models ◽  
The Andes ◽  
Interannual Rainfall Variability

AbstractBolivia is facing numerous climate-related threats, ranging from water scarcity due to rapidly retreating glaciers in the Andes to a partial loss of the Amazon forest in the lowlands. To assess what changes in climate may be expected in the future, 35 global circulation models (GCMs) from the third and fifth phases of the Coupled Model Intercomparison Project (CMIP3/5) were analyzed for the Bolivian case. GCMs were validated against observed surface air temperature, precipitation, and incoming shortwave (SW) radiation for the period 1961–90. Weighted ensembles were developed, and climate change projections for five emission scenarios were assessed for 2070–99. GCMs revealed an overall cold, wet, and positive-SW-radiation bias and showed no substantial improvement from the CMIP3 to the CMIP5 ensemble for the Bolivian case. Models projected an increase in temperature (2.5°–5.9°C) and SW radiation (1%–5%), with seasonal and regional differences. In the lowlands, changes in annual rainfall remained uncertain for CMIP3 whereas CMIP5 GCMs were more inclined to project decreases (−9%). This pattern also applied to most of the Amazon basin, suggesting a higher risk of partial biomass loss for the CMIP5 ensemble. Both ensembles agreed on less rainfall (−19%) during drier months (June–August and September–November), with significant changes in interannual rainfall variability, but disagreed on changes during wetter months (January–March). In the Andes, CMIP3 GCMs tended toward less rainfall (−9%) whereas CMIP5 tended toward more (+20%) rainfall during parts of the wet season. The findings presented here may provide inputs for studies of climate change impact that assess how resilient human and natural systems are under different climate change scenarios.

Holocene climate variability and associated paleoenvironmental changes in the eastern lowlands of Guatemala revealed by a lake sediment from Lake Izabal

2021 ◽  
Author(s):  
Edward Duarte ◽  
Jonathan Obrist-Farner ◽  
Alex Correa-Metrio ◽  
Byron A. Steinman
Keyword(s):  
Central America ◽  
Principal Component ◽  
Sharp Decrease ◽  
Progressive Increase ◽  
Lake Productivity ◽  
Climate Conditions ◽  
The Holocene ◽  
Lake Water Chemistry ◽  
The Caribbean ◽  
Wet Climate

<p>Sediment records have been widely used to reconstruct Holocene environmental and climate conditions around the world. As new Holocene records from Central America and the Caribbean have become available, new hypotheses have emerged to explain the complex hydroclimate variability in the region. Here we present results from a radiocarbon-dated sediment core recovered from Lake Izabal, eastern Guatemala, that covers the last ~9,500 years. We combined sedimentological, XRF elemental abundances, and principal component (PC) analyses to reconstruct changes in erosion/precipitation, lake productivity, and lake water chemistry during the Holocene. Our results indicate that during the early Holocene, Lake Izabal was a shallow lake with minimal catchment erosion/precipitation as indicated by the abundance of organic-rich mud, coupled with the lowest PC scores and titanium (Ti) abundance of the entire record. An overall increase in the PC scores and a progressive increase in Ti suggest that precipitation/erosion increased from 8,300 to 4,800 cal yr BP and remained high until 1,200 cal yr BP. There was then a significant reduction in erosion and precipitation at ca. 1,200 cal yr BP, as evidenced by a sharp decrease in magnetic susceptibility, terrigenic derived elements, and PC scores. We suggest that the transition towards wetter conditions from the early to the middle Holocene, followed by a stable wet climate until ca. 1,200 cal yr BP, was strongly influenced by a progressive increase in autumn insolation throughout the Holocene, which could have caused an increase in Caribbean sea surface temperatures, increasing moisture availability leading to greater precipitation amounts in the Caribbean coast of Central America.</p>

scholarly journals Global Patterns of the Contributions of Storm Frequency, Intensity, and Seasonality to Interannual Variability of Precipitation

2015 ◽  
Vol 29 (1) ◽  
pp. 3-15 ◽  
Author(s):  
Stephen P. Good ◽  
Kaiyu Guan ◽  
Kelly K. Caylor
Keyword(s):  
Interannual Variability ◽  
Amazon Basin ◽  
Cross Correlation ◽  
Rainfall Variability ◽  
Precipitation Variability ◽  
Individual Variability ◽  
Precipitation Event ◽  
Annual Rainfall ◽  
Eastern United States ◽  
Wet Season

Abstract Interannual variation in precipitation totals is a critical factor governing the year-to-year availability of water resources, yet the connection between interannual precipitation variability and underlying event- and season-scale precipitation variability remains unclear. In this study, tropical and midlatitude precipitation characteristics derived from extensive station records and high-frequency satellite observations were analyzed to attribute the fraction of interannual variability arising as a result of individual variability in precipitation event intensity, frequency, and seasonality, as well as the cross-correlation between these factors at the global scale. This analysis demonstrates that variability in the length of the wet season is the most important factor globally, causing 52% of the total interannual variability, while variation in the intensity of individual rainfall events contributes 31% and variability in interstorm wait times contributes only 17%. Spatial patterns in the contribution of each of these intra-annual rainfall characteristics are informative, with regions such as Indonesia and southwestern North America primarily influenced by seasonality, while regions such as the eastern United States, central Africa, and the upper Amazon basin are strongly influenced by storm intensity and frequency. A robust cross-correlation between climate characteristics is identified in the equatorial Pacific, revealing an increased interannual variability over what is expected based on the variability of individual events. This decomposition of interannual variability identifies those regions where accurate representation of daily and seasonal rainfall statistics is necessary to understand and correctly model rainfall variability at longer time scales.

scholarly journals The Role of the Rainfall Variability in the Decline of the Surface Suspended Sediment in the Upper Madeira Basin (2003–2017)

2021 ◽  
Vol 3 ◽  
Author(s):  
Irma Ayes Rivera ◽  
Jorge Molina-Carpio ◽  
Jhan Carlo Espinoza ◽  
Omar Gutierrez-Cori ◽  
Wilmar L. Cerón ◽  
...  
Keyword(s):  
Suspended Sediment ◽  
Amazon Basin ◽  
Environmental Changes ◽  
Rainfall Variability ◽  
Water Discharge ◽  
Critical Issue ◽  
Base Flow ◽  
Rainfall Time Series ◽  
Madeira River

The Madeira River rises in the Andes, draining the southwestern Amazon basin and contributing up to 50% of the Amazon River sediment load. The Porto Velho station monitors the Upper Madeira basin and is located just downstream of the Jirau and Santo Antonio hydropower dams. At this station, decreasing trend (p < 0.10) of the surface suspended sediment concentration (SSSC) has been documented during the sediment peak season (December to February) for the 2003–2017 period. This study aims to evaluate the role of the rainfall variability on this documented decreasing trend. For this purpose, we applied correlation and trend analysis in water discharge, SSSC and rainfall time series over the main tributaries of the Upper Madeira basin. The decline of SSSC in December is attributed to the reduction of rainfall in the Madre de Dios sub-basin from the start of the rainy season in October. However, the SSSC negative trend (p < 0.10) in January and February is associated with a shift in the magnitude of rainfall during these months in the Andean region after 2008, and the dilution associated with base flow. These results reveal that the decline of SSSC in the Madeira River should not be evaluated just on the basis of the data downstream from the dams, but also of the processes upstream in the Andean part of the basin. In a context of drastic anthropogenic climate and environmental changes, understanding the combined influence of regional hydroclimate variability and human actions on erosion and sediment transport remains a critical issue for the conservation of the Amazon-Andes system.

scholarly journals Southeast Australia Autumn Rainfall Reduction: A Climate-Change-Induced Poleward Shift of Ocean–Atmosphere Circulation

2013 ◽  
Vol 26 (1) ◽  
pp. 189-205 ◽  
Author(s):  
Wenju Cai ◽  
Tim Cowan
Keyword(s):  
Rainfall Variability ◽  
Southern Annular Mode ◽  
Annual Rainfall ◽  
Sea Level Pressure ◽  
Southeastern Australia ◽  
Northern Latitudes ◽  
Poleward Shift ◽  
Rainfall Reduction ◽  
Wet Climate ◽  
Subtropical Ridge

Abstract Since the 1950s annual rainfall over southeastern Australia (SEA) has decreased considerably with a maximum decline in the austral autumn season (March–May), particularly from 1980 onward. The understanding of SEA autumn rainfall variability, the causes, and associated mechanisms for the autumn reduction remain elusive. As such, a new plausible mechanism for SEA autumn rainfall variability is described, and the dynamics for the reduction are hypothesized. First, there is no recent coherence between SEA autumn rainfall and the southern annular mode, discounting it as a possible driver of the autumn rainfall reduction. Second, weak trends in the subtropical ridge intensity cannot explain the recent autumn rainfall reduction across SEA, even though a significant relationship exists between the ridge and rainfall in April and May. With a collapse in the relationship between the autumn subtropical ridge intensity and position in recent decades, a strengthening in the influence of the postmonsoonal winds from north of Australia has emerged, as evident by a strong post-1980 coherence with SEA mean sea level pressure and rainfall. From mid to late autumn, there has been a replacement of a relative wet climate in SEA with a drier climate from northern latitudes, representing a climate shift that has contributed to the rainfall reduction. The maximum baroclinicity, as indicated by Eady growth rates, has shifted poleward. An associated poleward shift of the dominant process controlling SEA autumn rainfall has further enhanced the reduction, particularly across southern SEA. This observed change over the past few decades is consistent with a poleward shift of the ocean and atmosphere circulation.

OSL chronology of the Liena archeological site in the Yarlung Tsangpo valley throws new light on human occupation of the Tibetan Plateau

The Holocene ◽  
2020 ◽  
Vol 30 (7) ◽  
pp. 1043-1052
Author(s):  
Zhiyong Ling ◽  
Xiaoyan Yang ◽  
Yixuan Wang ◽  
Yanren Wang ◽  
Jianhui Jin ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Environmental Changes ◽  
Warm Period ◽  
Human Migration ◽  
The Tibetan Plateau ◽  
Human Occupation ◽  
Climate Conditions ◽  
The Holocene ◽  
Cultural Layers ◽  
Yarlung Tsangpo

Recent environmental archeological evidence has started to throw light on both the timing and processes of human colonization of the Tibetan Plateau (TP). Yarlung Tsangpo (YT) valley, a very important region of the southern TP for occupation, is home to not only modern Tibetans but also their ancestors. However, a lack of suitable sedimentary strata has limited the establishment of a secure chronology. Here, we report on a new stratigraphic section with prehistoric pottery and cultural layers that was discovered on a terrace of the YT at Liena, in Nyingchi County. The cultural layers are overlain by, and bedded within, eolian and lacustrine sediments. We used the quartz Optically Stimulated Luminescence (OSL) method to date 11 samples and performed geochemical analysis on 100 samples to derive paleoenvironmental indicators. The OSL analysis gave an age of 4.3 ka BP for the cultural layer, which makes it the earliest human activity in the YT valley of Nyingchi to date. In addition, commencement of eolian deposition was dated to at least 8.3 ka, coinciding with the Holocene warm period. We discuss possible causal factors for human occupation in the valley and show that climatic changes played a crucial role in prehistoric human migration c. 8.3–4.3 ka BP. Before the early Holocene, most of the river terraces in the valley were being actively reworked by rivers or covered by lakes. So there were no suitable places for occupation by ancient populations. With the recession of dammed lakes during the Holocene warm period, the relatively flat and wide valley terraces, blanketed with rich eolian deposits (such as sandy loess), provided an attractive place for ancient people engaged in nomadic and even agricultural activities. Hence, the climate conditions of the Holocene warm period drove the environmental changes that provided favorable conditions for ancient human activities.

Holocene Environmental Changes from the Rio Curuá Record in the Caxiuanã Region, Eastern Amazon Basin

2000 ◽  
Vol 53 (3) ◽  
pp. 369-377 ◽  
Author(s):  
Hermann Behling ◽  
Marcondes Lima da Costa
Keyword(s):  
Rain Forest ◽  
Amazon Basin ◽  
Environmental Changes ◽  
River System ◽  
High Water ◽  
Water Levels ◽  
Annual Rainfall ◽  
Terra Firme ◽  
Study Region ◽  
Amazon Rain Forest

AbstractHolocene environments have been reconstructed by multiproxy studies of an 850-cm-long core from Rio Curuá dating to >8000 14C yr B.P. The low-energy river lies in the eastern Amazon rain forest in the Caxiuanã National Forest Reserve, 350 km west of Belem in northern Brazil. Sedimentological, mineralogical, and geochemical dates demonstrate that the deposits correspond to two different environments, sediments of an active river before 8000 14C yr B.P. and later a passive river system. The pollen analytical results indicate four different local and regional Holocene paleoenvironmental periods: (1) a transition to a passive fluvial system and a well-drained terra firme (unflooded upland) Amazon rain forest with very limited development of inundated forests (várzea and igapó) (>7990–7030 14C yr B.P.); (2) a sluggish river with a local Mauritia palm-swamp and similar regional vegetation, as before (7030–5970 14C yr B.P.); (3) a passive river, forming shallow lake conditions and with still-abundant terra firme forest in the study region (5970–2470 14C yr B.P.); and (4) a blocked river with high water levels and marked increase of inundated forests during the last 2470 14C yr B.P. Increased charcoal during this last period suggests the first strong presence of humans in this region. The Atlantic sea level rise was probably the major factor in paleoenvironmental changes, but high water stands might also be due to greater annual rainfall during the late Holocene.

scholarly journals Demographic history and genomic response to environmental changes in a rapid radiation of wild rats

2021 ◽  
Author(s):  
Deyan Ge ◽  
Anderson Feijó ◽  
Zhixin Wen ◽  
Alexei V Abramov ◽  
Liang Lu ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Demographic History ◽  
Terrestrial Ecosystems ◽  
Tibet Plateau ◽  
Global Changes ◽  
Rapid Radiation ◽  
Protein Functions ◽  
Wild Rats ◽  
Qinghai Tibet Plateau ◽  
Genomic Response

Abstract For organisms to survive and prosper in a harsh environment, particularly under rapid climate change, poses tremendous challenges. Recent studies have highlighted the continued loss of megafauna in terrestrial ecosystems and the subsequent surge of small mammals, such as rodents, bats, lagomorphs, and insectivores. However, the ecological partitioning of these animals will likely lead to large variation in their responses to environmental change. In the present study, we investigated the evolutionary history and genetic adaptations of white-bellied rats (Niviventer Marshall, 1976), which are widespread in the natural terrestrial ecosystems in Asia but also known as important zoonotic pathogen vectors and transmitters. The southeastern Qinghai-Tibet Plateau (QHTP) was inferred as the origin center of this genus, with parallel diversification in temperate and tropical niches. Demographic history analyses from mitochondrial and nuclear sequences of Niviventer demonstrated population size increases and range expansion for species in Southeast Asia, and habitat generalists elsewhere. Unexpectedly, population increases were seen in N. eha, which inhabits the highest elevation among Niviventer species. Genome scans of nuclear exons revealed that among the congeneric species, N. eha has the largest number of positively selected genes. Protein functions of these genes are mainly related to olfaction, taste and tumor suppression. Extensive genetic modification presents a major strategy in response to global changes in these alpine species.

Species distribution modeling reveals the ecological niche of extinct megafauna from South America

2021 ◽  
pp. 1-8
Author(s):  
Thaísa Araújo ◽  
Helena Machado ◽  
Dimila Mothé ◽  
Leonardo dos Santos Avilla
Keyword(s):  
South America ◽  
Species Distribution ◽  
Environmental Changes ◽  
Species Distribution Modeling ◽  
Human Action ◽  
Northeastern Brazil ◽  
Climate Conditions ◽  
Middle Holocene ◽  
Distribution Modeling ◽  
The Impact

Abstract Climatic and environmental changes, as well as human action, have been cited as potential causes for the extinction of megafauna in South America at the end of the Pleistocene. Among megamammals lineages with Holarctic origin, only horses and proboscideans went extinct in South America during this period. This study aims to understand how the spatial extent of habitats suitable for Equus neogeus and Notiomastodon platensis changed between the last glacial maximum (LGM) and the middle Holocene in order to determine the impact that climatic and environmental changes had on these taxa. We used species distribution modeling to estimate their potential extent on the continent and found that both species occupied arid and semiarid open lands during the LGM, mainly in the Pampean region of Argentina, southern and northeastern Brazil, and parts of the Andes. However, when climate conditions changed from dry and cold during the LGM to humid and warm during the middle Holocene, the areas suitable for these taxa were reduced dramatically. These results support the hypothesis that climatic changes were a driving cause of extinction of these megamammals in South America, although we cannot rule out the impact of human actions or other potential causes for their extinction.

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