scholarly journals A high-altitude peatland record of environmental changes in the NW Argentine Andes (24 ° S) over the last 2100 years

2016 ◽  
Vol 12 (5) ◽  
pp. 1165-1180 ◽  
Author(s):  
Karsten Schittek ◽  
Sebastian T. Kock ◽  
Andreas Lücke ◽  
Jonathan Hense ◽  
Christian Ohlendorf ◽  
...  
Keyword(s):  
High Altitude ◽  
Environmental Changes ◽  
Regional Scale ◽  
Central Andes ◽  
High Accumulation ◽  
Climate Conditions ◽  
Climate Anomalies ◽  
Dry Conditions ◽  
Induced Changes ◽  
The 19Th Century

Abstract. High-altitude cushion peatlands are versatile archives for high-resolution palaeoenvironmental studies, due to their high accumulation rates, range of proxies, and sensitivity to climatic and/or human-induced changes. Especially within the Central Andes, the knowledge about climate conditions during the Holocene is limited. In this study, we present the environmental and climatic history for the last 2100 years of Cerro Tuzgle peatland (CTP), located in the dry Puna of NW Argentina, based on a multi-proxy approach. X-ray fluorescence (XRF), stable isotope and element content analyses (δ13C, δ15N, TN and TOC) were conducted to analyse the inorganic geochemistry throughout the sequence, revealing changes in the peatlands' past redox conditions. Pollen assemblages give an insight into substantial environmental changes on a regional scale. The palaeoclimate varied significantly during the last 2100 years. The results reflect prominent late Holocene climate anomalies and provide evidence that in situ moisture changes were coupled to the migration of the Intertropical Convergence Zone (ITCZ). A period of sustained dry conditions prevailed from around 150 BC to around AD 150. A more humid phase dominated between AD 200 and AD 550. Afterwards, the climate was characterised by changes between drier and wetter conditions, with droughts at around AD 650–800 and AD  1000–1100. Volcanic forcing at the beginning of the 19th century (1815 Tambora eruption) seems to have had an impact on climatic settings in the Central Andes. In the past, the peatland recovered from climatic perturbations. Today, CTP is heavily degraded by human interventions, and the peat deposit is becoming increasingly susceptible to erosion and incision.

scholarly journals Environmental and climatic history in the NW Argentine Andes (24° S) over the last 2100 years inferred from a high-altitude peatland record

2015 ◽  
Vol 11 (3) ◽  
pp. 2037-2076 ◽  
Author(s):  
K. Schittek ◽  
S. T. Kock ◽  
A. Lücke ◽  
C. Ohlendorf ◽  
J. J. Kulemeyer ◽  
...  
Keyword(s):  
High Altitude ◽  
Environmental Changes ◽  
Regional Scale ◽  
Moisture Flux ◽  
Central Andes ◽  
High Accumulation ◽  
Climate Conditions ◽  
Climate Anomalies ◽  
Climatic History ◽  
The 19Th Century

Abstract. High-altitude cushion peatlands are versatile archives for high-resolution palaeoenvironmental studies, due to their high accumulation rates, range of proxies and sensitivity to climatic and/or human-induced changes. Especially within the central Andes, the knowledge about climate conditions during the Holocene is limited. In this study, we present the environmental and climatic history for the last 2100 years of Cerro Tuzgle peatland (CTP), which is located in the dry Puna of NW Argentina, based on a multi-proxy approach. X-ray fluorescence (XRF), stable isotope and element content analyses (δ13C, δ15N, TN and TOC) were conducted to analyse the inorganic geochemistry throughout the sequence, revealing changes in the peatland's past redox conditions. Pollen assemblages give an insight into substantial environmental changes on a regional scale. The palaeoclimate varied significantly during the last 2100 years. The results reflect prominent late Holocene climate anomalies and provide evidence that Northern Hemisphere temperature oscillations were extensive and affected the southward migration of the Intertropical Convergence Zone (ITCZ), and hence, the intensity of moisture flux within the South American Summer Monsoon (SASM) belt. Volcanic forcing at the beginning of the 19th century (1815 Tambora eruption) seems to have had an impact on climatic settings in the central Andes. In the past, the peatland recovered from climatic perturbations. Nowadays, CTP is heavily degraded by human interventions, and the peat deposit becomes increasingly susceptible to erosion and incision.

scholarly journals Vegetation and geochemical responses to Holocene rapid climate change in Sierra Nevada (SE Iberia): The Laguna Hondera record

2018 ◽  
Author(s):  
Jose Manuel Mesa-Fernández ◽  
Gonzalo Jiménez-Moreno ◽  
Marta Rodrigo-Gámiz ◽  
Antonio García-Alix ◽  
Francisco J. Jiménez-Espejo ◽  
...  
Keyword(s):  
Climate Variability ◽  
High Altitude ◽  
Sierra Nevada ◽  
Environmental Changes ◽  
Regional Scale ◽  
Saharan Dust ◽  
Ice Age ◽  
Mountain Lake ◽  
High Mountain ◽  
Arid Conditions

Abstract. High-altitude peat bogs and lacustrine records are very sensitive to climate changes and atmospheric pollution. Recent studies show a close relationship between regional climate aridity and enhanced eolian input to lake sediments. However, changes in regional-scale dust fluxes due to climate variability at short-scales and how alpine environments were impacted by climatic- and human-induced environmental changes are not completely understood. Here we present a multi-proxy lake sediment record of climate variability in the Sierra Nevada (SE Iberian Peninsula) over the Holocene. Palynological, geochemical and magnetic susceptibility (MS) proxies obtained from the high mountain lake record of Laguna Hondera (LH) evidence humid conditions during the Early Holocene, while a trend towards more arid conditions is recognized since ~ 7000 cal yr BP, with enhanced Saharan eolian dust deposition until Present. This trend towards enhanced arid conditions was modulated by millennial-scale climate variability. Relative humid conditions occurred during the Iberian Roman Humid Period (2600–1450 cal yr BP) and predominantly arid conditions occurred during the Dark Ages and the Medieval Climate Anomaly (1450–650 cal yr BP). The Little Ice Age (650–150 cal yr BP) is characterized in the LH record by an increase in runoff and a minimum in eolian input. In addition, human impact in the area is noticed through the record of Olea cultivation, Pinus reforestation and Pb pollution during the Industrial Period (150 cal yr BP-present). Furthermore, a unique feature preserved at LH is the correlation between Zr and Ca, two important elements of Saharan dust source in Sierra Nevada lake records. This supports that present day biochemical observations, pointing to eolian input as main inorganic nutrient source for oligotrophic mountain lakes, are comparable to the past record of eolian supply to these high-altitude lakes.

scholarly journals Vegetation and geochemical responses to Holocene rapid climate change in the Sierra Nevada (southeastern Iberia): the Laguna Hondera record

2018 ◽  
Vol 14 (11) ◽  
pp. 1687-1706 ◽  
Author(s):  
Jose M. Mesa-Fernández ◽  
Gonzalo Jiménez-Moreno ◽  
Marta Rodrigo-Gámiz ◽  
Antonio García-Alix ◽  
Francisco J. Jiménez-Espejo ◽  
...  
Keyword(s):  
Magnetic Susceptibility ◽  
Climate Variability ◽  
High Altitude ◽  
Sierra Nevada ◽  
Environmental Changes ◽  
Regional Scale ◽  
Saharan Dust ◽  
Ice Age ◽  
High Mountain ◽  
Arid Conditions

Abstract. High-altitude peat bogs and lacustrine records are very sensitive to climate changes and atmospheric dust input. Recent studies have shown a close relationship between regional climate aridity and enhanced eolian input to lake sediments. However, changes in regional-scale dust fluxes due to climate variability at short scales and how alpine environments were impacted by climatic- and human-induced environmental changes are not completely understood. Here we present a multi-proxy (palynological, geochemical and magnetic susceptibility) lake sediment record of climate variability in the Sierra Nevada (southeastern Iberian Peninsula) over the Holocene. Magnetic susceptibility and geochemical proxies obtained from the high mountain lake record of Laguna Hondera evidence humid conditions during the early Holocene, while a trend towards more arid conditions is recognized since ∼7000 cal yr BP, with enhanced Saharan eolian dust deposition until the present. This trend towards enhanced arid conditions was modulated by millennial-scale climate variability. Relative humid conditions occurred during the Iberian Roman Humid Period (2600–1450 cal yr BP) and predominantly arid conditions occurred during the Dark Ages and the Medieval Climate Anomaly (1450–650 cal yr BP). The Little Ice Age (650–150 cal yr BP) is characterized in the Laguna Hondera record by an increase in runoff and a minimum in eolian input. In addition, we further suggest that human impact in the area is noticed through the record of Olea cultivation, Pinus reforestation and Pb pollution during the Industrial Period (150 cal yr BP–present). Furthermore, we estimated that the correlation between Zr and Ca concentrations stands for Saharan dust input to the Sierra Nevada lake records. These assumptions support that present-day biochemical observations, pointing to eolian input as the main inorganic nutrient source for oligotrophic mountain lakes, are comparable to the past record of eolian supply to these high-altitude lakes.

Past climate and environmental changes in the Central Andes of NW Argentina recorded in Laguna Comedero sediments

2020 ◽  
Author(s):  
Paula Vignoni ◽  
Rik Tjallingii ◽  
Francisco Córdoba ◽  
Birgit Plessen ◽  
Gonzalo Torres ◽  
...  
Keyword(s):  
Organic Matter ◽  
Large Scale ◽  
Environmental Changes ◽  
Southern Oscillation ◽  
Central Andes ◽  
Terrestrial Organic Matter ◽  
Rainfall Gradient ◽  
Climate History ◽  
Climate Conditions ◽  
Erosion Processes

<p>Due to the meridional extension and prominent orography, the Central Andes of NW Argentina act as a topographic barrier to the moisture-bearing easterly winds. This result in contrasting climate conditions and a steep E-W rainfall gradient with high precipitation on the eastern flanks and increasing aridity westwards into the Puna plateau. Laguna Comedero is a shallow lake located in the subtropical forest of the Yungas in the eastern flank of the Argentine Eastern Cordillera (24°06'54.7" S - 65°29'7.2" W, 2,035 m a.s.l.). About 80% of the total annual precipitation (~1300 mm, Los Nogales station 1958-1989) occurs between November and March, controlled by the dynamics of the South American Monsoon System (SAMS). This region is considered sensitive to shifts in the SAMS, as well as the superposition of other large-scale phenomena (e.g. El Niño Southern Oscillation, Pacific Decadal Oscillation) but the timing and extent of precipitation changes prior to the instrumental period in this area are still largely unknown.<br>Here we present a combination of XRF core scanning, CN elemental analyses and stable isotopes of an 11 m-long sediment record from this lake for reconstructing the regional late Holocene climate history in this region of South America. Our results reveal a prominent shift in sedimentation, from detrital brown event-triggered silt and clay deposition and sandy intervals in the lower part of the core to an alternation of gray clastic and black organic-rich intervals in the upper 3.5 m. Below this shift in sedimentation, low TOC values (mean 0.34%) and high values of elements indicative of detrital sediments (e.g. Ti) suggest a dominance of catchment erosion processes. High TOC values of up to 20.5% in the organic-rich intervals in the uppermost 3.5 m likely reflect substantial terrestrial organic matter influx as suggestd by C/N atomic ratios around 17. δ<sup>13</sup>C<sub>OM</sub> values in these intervals (-28.8 to -22.2‰) reflect the contribution of the Yungas forest (-27.9 to -27.2‰) surrounding the lake, dominated by <em>Alnus acuminata</em>, <em>Polypepis australis</em>, <em>Podocarpus parlatorei</em>, among other subtropical tree species. <em>Alnus</em> forest is related to >1000 mm/yr rainfalls. <br>The pronounced alternation of organic-rich and detrital sediments in the upper 3.5 m suggest highly variable lake conditions that might be either influenced by climate and/or catchment changes and is the focus of further investigations. Preliminary dating suggests that the increase in organic matter deposition in the lake occurred at the beginning of the last millennium (ca. AD 1,000). A more detailed chronological framework is in progress including a paleomagnetic reconstruction for this area. </p>

Paleoenvironmental analysis of wet meadow in the Deseado Massif: Implications for the Holocene occupation of Argentinian Patagonia

The Holocene ◽  
2021 ◽  
pp. 095968362110259
Author(s):  
Bruno Mosquera ◽  
María V Mancini
Keyword(s):  
Environmental Changes ◽  
Low Energy ◽  
Semiarid Region ◽  
Human Occupation ◽  
Wet Meadow ◽  
Radiocarbon Dates ◽  
Sedimentation Environment ◽  
Dry Conditions ◽  
Paleoenvironmental Analysis ◽  
Deseado Massif

Paleoenvironmental data from wet-meadow environments in the arid-semiarid region of Patagonia are still incipient and the paleoenvironmental records came from pollen sequences of caves and rockshelters. The main reasons to study wetland records are their undisturbed (by humans) sedimentologic continuity, in contrast to deposits in rock shelters and caves; and their regional presentation of environmental changes that can be compared to archeological data. The aim of this paper is to evaluate the past hydrological dynamic of a wet-meadow from Deseado Massif and its relationship with the human occupation. For this purpose, we present the results of the sediment and pollen analysis of Mallín La Primavera wet-meadow that provide a sequence starting in the mid-Holocene. The results indicate a lower water table in the mallín prior to 6900 cal yr BP. Sediment analysis indicates low energy sedimentation environment with flood events and very low energy streams. Human occupational data show chronological discontinuities in mid-Holocene in several regions of Patagonia and the southern cone. In the studied region, two chronological hiatuses (7828–6434 cal yr BP and 3005–2710 cal yr BP) where recognized that appear to correlate with shrub steppes, indicating dry conditions. These conditions may explain the lack of archeological radiocarbon dates in the area during this period. The integration of sediment and pollen results from the Deseado Massif indicates dry and windy conditions for the middle Holocene. The lack of archeological radiocarbon dates would have been influenced by the loss of moisture in water sources such as springs and their associated wet meadows ( mallines).

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.

scholarly journals Debris Flows Occurrence in the Semiarid Central Andes under Climate Change Scenario

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 43
Author(s):  
Stella M. Moreiras ◽  
Sergio A. Sepúlveda ◽  
Mariana Correas-González ◽  
Carolina Lauro ◽  
Iván Vergara ◽  
...  
Keyword(s):  
Climate Change ◽  
Debris Flows ◽  
Environmental Changes ◽  
Urban Expansion ◽  
Central Andes ◽  
Semiarid Region ◽  
Change Scenario ◽  
Permafrost Degradation ◽  
Mountain Areas ◽  
Negative Impacts

This review paper compiles research related to debris flows and hyperconcentrated flows in the central Andes (30°–33° S), updating the knowledge of these phenomena in this semiarid region. Continuous records of these phenomena are lacking through the Andean region; intense precipitations, sudden snowmelt, increased temperatures on high relief mountain areas, and permafrost degradation are related to violent flow discharges. Documented catastrophic consequences related to these geoclimatic events highlight the need to improve their understanding in order to prepare the Andean communities for this latent danger. An amplified impact is expected not only due to environmental changes potentially linked to climate change but also due to rising exposure linked to urban expansion toward more susceptible or unstable areas. This review highlights as well the need for the implementation of preventive measures to reduce the negative impacts and vulnerability of the Andean communities in the global warming context.

Inca “Stone Ancestors” in Context at a High-Altitude Usnu Platform

2010 ◽  
Vol 21 (2) ◽  
pp. 173-194 ◽  
Author(s):  
Frank M. Meddens ◽  
Colin McEwan ◽  
Cirilo Vivanco Pomacanchari
Keyword(s):  
High Altitude ◽  
Central Andes ◽  
Vertical Shaft ◽  
Original Surface ◽  
Small Basin

AbstractRecent investigations at mountaintop sites around the Ayacucho Basin in the central Andes have identified a distinctive category of isolated Inca stone-faced platforms. Test excavations of the three-tiered platform at one site, Incapirqa/Waminan, revealed a narrow vertical shaft penetrating from the original surface through the fills to a small basin cut into the underlying andesite bedrock. A carefully arranged deposit of three unusual stones was found in this basin. Early Spanish chroniclers give firsthand accounts of a variety of Inca solar rituals observed in Cuzco in which revered objects were deployed, including some sculpted in stone. The detailed descriptions of these stone objects are corroborated by the excavated finds at Incapirqa/Waminan and offer suggestive analogies for interpreting their context and significance.

scholarly journals Holocene changes in African vegetation: tradeoff between climate and water availability

2014 ◽  
Vol 10 (2) ◽  
pp. 681-686 ◽  
Author(s):  
C. Hély ◽  
A.-M. Lézine ◽  
APD contributors
Keyword(s):  
West Africa ◽  
Water Availability ◽  
Regional Scale ◽  
Plant Distribution ◽  
Climate Conditions ◽  
Tropical Plants ◽  
Plant Migration ◽  
Spatio Temporal ◽  
The Individual ◽  
Instrumental Records

Abstract. Although past climate change is well documented in West Africa through instrumental records, modeling activities, and paleo-data, little is known about regional-scale ecosystem vulnerability and long-term impacts of climate on plant distribution and biodiversity. Here we use paleohydrological and paleobotanical data to discuss the relation between available surface water, monsoon rainfall and vegetation distribution in West Africa during the Holocene. The individual patterns of plant migration or community shifts in latitude are explained by differences among tolerance limits of species to rainfall amount and seasonality. Using the probability density function methodology, we show here that the widespread development of lakes, wetlands and rivers at the time of the "Green Sahara" played an additional role in forming a network of topographically defined water availability, allowing for tropical plants to migrate north from 15 to 24° N (reached ca. 9 cal ka BP). The analysis of the spatio–temporal changes in biodiversity, through both pollen occurrence and richness, shows that the core of the tropical rainbelt associated with the Intertropical Convergence Zone was centered at 15–20° N during the early Holocene wet period, with comparatively drier/more seasonal climate conditions south of 15° N.

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