scholarly journals Paleoclimatic and archaeological evidence from Lake Suches for highland Andean refugia during the arid middle-Holocene

The Holocene ◽  
2018 ◽  
Vol 29 (2) ◽  
pp. 328-344 ◽  
Author(s):  
Benjamin R Vining ◽  
Byron A Steinman ◽  
Mark B Abbott ◽  
Arielle Woods
Keyword(s):  
Residence Time ◽  
Water Levels ◽  
Human Populations ◽  
Atmospheric Moisture ◽  
Tropical Andes ◽  
Isotopic Enrichment ◽  
Middle Holocene ◽  
Ecological Stress ◽  
Andean Flora ◽  
Precipitation Trends

Severe aridity during the mid-Holocene, ca. 8.0–4.0 kyr BP, led to extreme ecological stress in the tropical Andes. Here, we report paleolimnological and archeological data from Lake Suches in southern Peru (70° 24’ 12” W, 16° 55’ 35” S) spanning 13.6–4.4 kyr BP. Integrated paleoclimate and archeological data reveal that moisture was locally available and the basin served as an ecological refugium throughout the mid-Holocene. Mid-Holocene aridity was established no later than 7.2 kyr BP, with maximum aridity ca. 5.5–4.8 kyr BP. However, water levels in Lake Suches were sustained throughout peak middle-Holocene aridity, even as other systems desiccated. Isotopic enrichment of water in Lake Suches (δ18Olake) and extensive wetlands (δ18Obofedal) surrounding the lake indicate prolonged residence time. These reservoirs, combined with elevation-linked hydrographic factors, mitigated mid-Holocene net decreases in atmospheric moisture. Archeological data from Suches indicate successive population increases beginning ca. 11.0–9.8 kyr BP as drier but more stable early Holocene conditions were established regionally. Population maxima in Suches during the mid-Holocene/mid-Archaic period ca. 9.0–7.0 kyr BP coincide with peak aridity in the Titicaca and Atacama systems, as well as documented archeological hiatuses in these regions. Population decreases coincide with peak aridity recorded in Lake Suches ca. 6.0–5.0 kyr BP, but the basin was never fully abandoned. Evidence for refugial microenvironments is key to understanding the persistence of human populations and other endemic Andean flora and fauna during the highly adverse climates of the middle-Holocene. We outline several mechanisms which likely explain the formation of refugia linked to bofedales and hydrographic characteristics of Suches. Understanding refugial dynamics will be key to understanding the effects of past climatic change, as well as addressing current warming and decreased precipitation trends in the tropical Andes.

Flow pattern and residence time of conduit flow and diffuse flow in calcareous sandstones (Bohemian Cretaceous Basin, Czech Republic)

2021 ◽  
Author(s):  
Iva Kůrková ◽  
Jiří Bruthans
Keyword(s):  
Czech Republic ◽  
Groundwater Flow ◽  
Residence Time ◽  
Dispersion Model ◽  
Tracer Tests ◽  
Water Levels ◽  
Northwestern Part ◽  
Residence Times ◽  
Karst Springs ◽  
Bohemian Cretaceous Basin

<p>Localities containing karst features were studied in the northwestern part of Bohemian Cretaceous Basin. Namely Turnov area in facies transition between coarse-delta sandstones and marlstones (Jizera Formation, Turonian) and Miskovice area in limestones and sandy limestones - sandstones (Peruc-Korycany Formation, Cenomanian). Evolution of karst conduits is discussed elsewhere (Kůrková et al. 2019).</p><p>In both localities, disappearing streams, caves and karst springs with maximum discharge up to 100 L/s were documented. Geology and hydrogeology of this area was studied from many points of view to describe formation of karst conduits and characterize groundwater flow. Tracer tests were performed using NaCl and Na-fluoresceine between sinkholes and springs under various flow rates to evaluate residence times of water in conduits and to describe geometry of conduits. Breatkthrough curves of tracer tests were evaluated by means of Qtracer2 program (Field 2002). Groundwater flow velocity in channels starts at 0.6 km/day during low water levels up to 15 km/day during maximum water levels, the velocity increases logarithmically as a function of discharge. Similar karst conduits probably occur in other parts of Bohemian Cretaceous Basin where lot of large springs can be found.</p><p>Mean residence time of difussed flow based on tritium, CFC and SF<sub>6</sub> sampled at karst springs is 20 years for 75% of water and 100 years for remaining 25%, based on binary mixing dispersion model. This shows that most of the water drained by karst conduits is infiltrated through the soil and fractured environment with relatively high residence time. Residence times in different types of wells and springs were also measured in whole north-western part of Bohemian Cretaceous Basin. Results indicate long residence times in semi-stagnant zones represented by monitoring wells and short residence times in preferential zones represented by springs and water-supply wells.</p><p> </p><p>Research was funded by the Czech Science Foundation (GA CR No. 19-14082S), Czech Geological Survey – internal project 310250</p><p> </p><p>Field M. (2002): The QTRACER2 program for Tracer Breakthrough Curve Analysis for Tracer Tests in Karstic Aquifers and Other hydrologic Systems. – U.S. Environmental protection agency hypertext multimedia publication in the Internet at http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=54930.</p><p>Kůrková I., Bruthans J., Balák F., Slavík M., Schweigstillová J., Bruthansová J., Mikuš P., Grundloch J. (2019): Factors controlling evolution of karst conduits in sandy limestone and calcareous sandstone (Turnov area, Czech Republic). Journal of Hydrology: 574: 1062-1073</p>

scholarly journals The residence time of water in the atmosphere revisited

2017 ◽  
Vol 21 (2) ◽  
pp. 779-790 ◽  
Author(s):  
Ruud J. van der Ent ◽  
Obbe A. Tuinenburg
Keyword(s):  
Residence Time ◽  
Hydrological Cycle ◽  
State Of The Art ◽  
Average Residence Time ◽  
Atmospheric Moisture ◽  
Atmospheric Water ◽  
Time And Space ◽  
Global Average ◽  
High Precipitation ◽  
Global Mean

Abstract. This paper revisits the knowledge on the residence time of water in the atmosphere. Based on state-of-the-art data of the hydrological cycle we derive a global average residence time of 8.9 ± 0.4 days (uncertainty given as 1 standard deviation). We use two different atmospheric moisture tracking models (WAM-2layers and 3D-T) to obtain atmospheric residence time characteristics in time and space. The tracking models estimate the global average residence time to be around 8.5 days based on ERA-Interim data. We conclude that the statement of a recent study that the global average residence time of water in the atmosphere is 4–5 days, is not correct. We derive spatial maps of residence time, attributed to evaporation and precipitation, and age of atmospheric water, showing that there are different ways of looking at temporal characteristics of atmospheric water. Longer evaporation residence times often indicate larger distances towards areas of high precipitation. From our analysis we find that the residence time over the ocean is about 2 days less than over land. It can be seen that in winter, the age of atmospheric moisture tends to be much lower than in summer. In the Northern Hemisphere, due to the contrast in ocean-to-land temperature and associated evaporation rates, the age of atmospheric moisture increases following atmospheric moisture flow inland in winter, and decreases in summer. Looking at the probability density functions of atmospheric residence time for precipitation and evaporation, we find long-tailed distributions with the median around 5 days. Overall, our research confirms the 8–10-day traditional estimate for the global mean residence time of atmospheric water, and our research contributes to a more complete view of the characteristics of the turnover of water in the atmosphere in time and space.

scholarly journals Atmospheric moisture residence time affects rainwater isotope ratios

Eos ◽  
2012 ◽  
Vol 93 (33) ◽  
pp. 324-324
Author(s):  
Atreyee Bhattacharya
Keyword(s):  
Residence Time ◽  
Isotope Ratios ◽  
Atmospheric Moisture

Geoscience Medallist 1. Understanding the Holocene Closed-Basin Phases (Lowstands) of the Laurentian Great Lakes and Their Significance

2016 ◽  
Vol 43 (3) ◽  
pp. 179 ◽  
Author(s):  
C.F.M. Lewis
Keyword(s):  
Great Lakes ◽  
Natural Experiment ◽  
Water Levels ◽  
Laurentian Great Lakes ◽  
Middle Holocene ◽  
Closed Basin ◽  
Large Water ◽  
A Chain ◽  
Changements Climatiques ◽  
St Lawrence River

The Laurentian Great Lakes are a chain of five large water bodies and connecting rivers that constitute the headwaters of the St. Lawrence River. Collectively they form one of the largest reservoirs of surface freshwater on the planet with an aggregate volume of >22,000 km3. Early interpretations of the postglacial lake history implicitly assumed that the Great Lakes always overflowed their outlets. A study of Lake Winnipeg which concluded that lack of water in a dry climate had dried that lake for millennia led to re-evaluation of the Great Lakes water-level history. Using the empirical information of glacioisostatic rebound derived from 14C-dated and uptilted Great Lake paleo-shorelines, a method of computation was developed to test the paradigm of continuous lake overflow. The method evaluated site and outlet uplift independently, and lowlevel indicators such as submerged tree stumps rooted beneath the present Great Lakes were found to be lower than the lowestpossible corresponding basin outlet. Results confirmed the low-level, closed-basin hydrological status of the early Great Lakes. This status is consistent with paleoclimatic inferences of aridity during the early Holocene before establishment of the present patterns of atmospheric circulation which now bring adequate precipitation to maintain the overflowing lakes. In a sense, the early to middle Holocene phase of dry climate and low water levels is a natural experiment to illustrate the sensitivity of the Great Lakes to climate change in this era of global warming, should their climate shift to one much drier than present, or future major diversions of their waters be permitted.RÉSUMÉLes Grands Lacs Laurentiens sont une chaine de cinq grandes étendues d’eau connectées par des rivières, constituant la source du Fleuve St-Laurent. Collectivement, ils forment un des plus grands réservoirs d’eau douce de surface de la planète avec un volume total de plus de >22,000 km3. Les premièresinterprétations de l’histoire postglaciaire des lacs supposaient implicitement que les Grands Lacs débordaient à leurs exutoires. Une étude du Lac Winnipeg, qui concluait qu’un déficit en eau durant un épisode de climat aride avait desséché le lac pendant des millénaires dans le passé, a mené à la réévaluation de l’histoire du niveau de l’eau des Grands Lacs. En utilisant des données empiriques du relèvement glacio-isostatique, dérivées de littoral anciens surélevés datés au 14C, une méthode de calcul a été développée pour tester le paradigme d’unedécharge lacustre continue. La méthode a évalué le soulèvement des sites et des exutoires indépendamment, et il a été constaté que les indicateurs de bas niveau tels que des troncs d’arbres submergés, enracinés en dessous des Grands Lacs actuels, étaient en fait sous le niveau de l’exutoire correspondant le plus bas. Les résultats confirment le bas niveau et le statut de basin hydrologique fermé des Grand Lacs dans le passé. Ce statut est cohérent avec des évidences paléoclimatiques d’aridité au début de l’Holocène, avant l’établissement des modes de circulation atmosphérique actuels qui apportent des quantités de précipitation adéquates au maintien des décharges lacustres. Dans un sens, la période climatique aride du début et du milieu de l’Holocène, et les bas niveaux d’eau constituent une expérience naturelle qui illustre la sensibilité des Grands Lacs aux changements climatiques, pertinent dans le contexte actuel de réchauffement global, surtout s’il s’avérait que leur climat devienne plus aride que présentement, ou que des diversions majeures des eaux soient permises.

scholarly journals Stable isotopes in global precipitation: A unified interpretation based on atmospheric moisture residence time

2012 ◽  
Vol 39 (11) ◽  
pp. n/a-n/a ◽  
Author(s):  
Pradeep K. Aggarwal ◽  
Oleg A. Alduchov ◽  
Klaus O. Froehlich ◽  
Luis J. Araguas-Araguas ◽  
Neil C. Sturchio ◽  
...  
Keyword(s):  
Stable Isotopes ◽  
Residence Time ◽  
Atmospheric Moisture ◽  
Global Precipitation

Continuous Holocene Record of Diatom Stratigraphy, Paleohydrology, and Anthropogenic Activity in a Spring-Mound in Southwestern United States

1994 ◽  
Vol 42 (2) ◽  
pp. 197-205 ◽  
Author(s):  
Dean W. Blinn ◽  
Richard H. Hevly ◽  
Owen K. Davis
Keyword(s):  
United States ◽  
Water Level ◽  
Water Levels ◽  
Anthropogenic Activity ◽  
Southwestern United States ◽  
Middle Holocene ◽  
Temperature And Precipitation ◽  
Diatom Stratigraphy ◽  
Diatom Density ◽  
Montezuma Well

AbstractThis study presents the first continuous record of fossil diatoms taken from an open spring-mound in southwestern United States. Diatoms were analyzed from a radiocarbon-dated core taken from Montezuma Well, a near thermally constant spring in northcentral Arizona. Fluctuations in total diatom density, oscillations in the relative abundance of Anomoeoneis sphaerophora, and intermittent deposition of calcite suggest that water levels in Montezuma Well underwent dramatic fluctuations to the degree of being intermittently dry, or at least very shallow, during the middle Holocene (∼8000-5000 yr B.P.). The fluctuations in water level probably correspond to oscillations in regional temperature and precipitation, which regulate hydrologic input and evaporation rates. The dramatic fluctuations in water level during the middle Holocene suggest that the endemic biota of Montezuma Well underwent relatively rapid speciation within the past ∼5000 yr. The appearance of endemic species (Gomphonema montezumense and Cyclotella pseudostelligera f. parva ) at ∼5000-3000 yr B.P. supports this hypothesis. Diatom indicators for organic enrichment (Aulacoseira granulata and A. islandica) closely coincide with the prehistoric native occupation of Montezuma Well.

scholarly journals Widespread population decline in South America correlates with mid-Holocene climate change

2018 ◽  
Author(s):  
Philip Riris ◽  
Manuel Arroyo-Kalin
Keyword(s):  
Climate Change ◽  
South America ◽  
Large Scale ◽  
Climatic Variability ◽  
Population Decline ◽  
Plant Management ◽  
Human Populations ◽  
Resource Base ◽  
Radiocarbon Dates ◽  
Middle Holocene

Quantifying the impacts of climate change on prehistoric demography is crucial for understanding the adaptive pathways taken by human populations. Archaeologists across South America have pointed to patterns of regional abandonment during the Middle Holocene (8200 to 4200 cal BP) as evidence of sensitivity to shifts in hydroclimate over this period. We develop a unified approach to investigate demography and climate in South America and aim to clarify the extent to which evidence of local anthropic responses can be generalised to large-scale trends. We achieve this by integrating archaeological radiocarbon data and palaeoclimatic time series to show that population decline occurred coeval with the transition to the initial mid-Holocene across South America. Through the analysis of radiocarbon dates with Monte Carlo methods, we find multiple, sustained phases of downturn associated to periods of high climatic variability. A likely driver of the duration and severity of demographic turnover is the frequency of exceptional climatic events, rather than the absolute magnitude of change. Unpredictable levels of tropical precipitation had sustained negative impacts on pre-Columbian populations lasting until at least 6000 cal BP, after which recovery is evident. Our results support the inference that a demographic regime shift in the second half of the Middle Holocene were coeval with cultural practices surrounding Neotropical plant management and early cultivation, possibly acting as buffers when the wild resource base was in flux.

scholarly journals Stratigraphy and paleoenvironments of the early to middle Holocene Chipalamawamba Beds (Malawi Basin, Africa)

2012 ◽  
Vol 9 (5) ◽  
pp. 5793-5822 ◽  
Author(s):  
B. Van Bocxlaer ◽  
W. Salenbien ◽  
N. Praet ◽  
J. Verniers
Keyword(s):  
Lacustrine Sediments ◽  
Lake Malawi ◽  
Water Levels ◽  
High Temporal Resolution ◽  
Lake Levels ◽  
Middle Holocene ◽  
Shell Beds ◽  
Low Levels ◽  
Early And Middle Holocene ◽  
Mollusk Assemblages

Abstract. We describe the Chipalamawamba Beds, early to middle Holocene deposits at the southern margin of long-lived Lake Malawi. The beds are exposed because of downcutting of the upper Shire River. The Chipalamawamba sediments are medium to coarse, yellow to brown sands deposited in lenses varying in horizontal extent from a few meters to several hundreds of meters. Four units are recognized; the first three mainly contain lacustrine sediments deposited during lake high-stands about 10.6–9.7 cal ka BP (Unit 1), 7.6–6.5 cal ka BP (Unit 2) and 5.9–5.3 cal ka BP. Sediments of Unit 4 top units 1 to 3, are coarser and display regular foresets and oblique-bedding, suggesting deposition in riverine environments after installation of the Shire River (~5.0 ka BP). Freshwater mollusk assemblages and bioturbations regularly occur in the lacustrine sediments, but are largely absent from Unit 4. Diverse and often contradicting hypotheses on the lake levels of Lake Malawi have been proposed for the early and middle Holocene. The Chipalamawamba Beds allow straight-forward recognition of water levels and provide strong evidence for oscillating lake levels during this period, rather than continuous high or low levels. Sedimentation rates have been high and individual shell beds have typically been deposited during a few decades. Because the Chipalamawamba Beds contain a sequence of mollusk assemblages with intervals between subsequent shell beds ranging from a century to a few millennia, they enable paleontological analysis of the fauna with unusually high temporal resolution. That some mollusk lineages inhabiting Lake Malawi are in the early stages of diversification and radiation increases the paleobiological relevance of these beds.

scholarly journals Atmospheric Moisture Pathways to the Highlands of the Tropical Andes: Analyzing the Effects of Spectral Nudging on Different Driving Fields for Regional Climate Modeling

Atmosphere ◽  
2018 ◽  
Vol 9 (11) ◽  
pp. 456 ◽  
Author(s):  
Katja Trachte
Keyword(s):  
Climate Modeling ◽  
Regional Climate ◽  
Regional Climate Modeling ◽  
Andes Mountains ◽  
Back Trajectory ◽  
Atmospheric Moisture ◽  
Tropical Andes ◽  
Air Masses ◽  
Spectral Nudging ◽  
The Andes

Atmospheric moisture pathways to the highlands of the tropical Andes Mountains were investigated using the Weather Research and Forecasting (WRF) model, as well as back-trajectory analysis. To assess model uncertainties according to the initial and lateral boundary conditions (ILBCs), the effects of spectral nudging and different driving fields on regional climate modeling were tested. Based on the spatio-temporal patterns of the large-scale atmospheric features over South America, the results demonstrated that spectral nudging compared to traditional long-term integration generally produced greater consistency with the reference data (ERA5). These WRF simulations further revealed that the location of the inter-tropical convergence zone (ITCZ), as well as the precipitation over the Andes Mountains were better reproduced. To investigate the air mass pathways, the most accurate WRF simulation was used as atmospheric conditions for the back-trajectory calculations. Three subregions along the tropical Andean chain were considered. Based on mean cluster trajectories and the water vapor mixing ratio along the pathways, the contributions of eastern and western water sources were analyzed. In particular, the southernmost subregion illustrated a clear frequency of occurrences of Pacific trajectories mostly during September–November (40%) when the ITCZ is shifted to the Northern Hemisphere and the Bolivian high pressure system is weakened. In the northernmost subregion, Pacific air masses as well reached the Andes highlands with rather low frequencies regardless of the season (2–12%), but with a moisture contribution comparable to the eastern trajectories. Cross-sections of the equivalent-potential temperature as an indicator of the moisture and energy content of the atmosphere revealed a downward mixing of the moisture aloft, which was stronger in the southern subregion. Additionally, low-level onshore breezes, which developed in both subregions, indicated the transport of warm-moist marine air masses to the highlands, highlighting the importance of the representation of the terrain and, thus, the application of dynamical downscaling using regional climate models.

scholarly journals Holocene Paleohydrology of the Tropical Andes from Lake Records

1997 ◽  
Vol 47 (1) ◽  
pp. 70-80 ◽  
Author(s):  
Mark B. Abbott ◽  
Geoffrey O. Seltzer ◽  
Kerry R. Kelts ◽  
John Southon
Keyword(s):  
Time Series ◽  
Late Pleistocene ◽  
Sediment Accumulation ◽  
Sedimentary Facies ◽  
Accumulation Rates ◽  
Tropical Andes ◽  
Abrupt Increase ◽  
Middle Holocene ◽  
Abrupt Changes ◽  
Cordillera Real

AbstractTwo century-scale time series in northern Bolivia constrain the ages of abrupt changes in the physical, geochemical, and biological characteristics of sediments obtained from lakes that formed during deglaciation from the late Pleistocene glacial maximum. The watersheds of Laguna Viscachani (16°12′S, 68°07′W, 3780 m) and Lago Taypi Chaka Kkota (16°13′S, 68°21′W, 4300 m), located on the eastern and western slopes of the Cordillera Real, respectively, contain small cirque glaciers. A high-resolution chronology of the lake sediments is provided by 23 AMS14C dates of discrete macrofossils. Late Pleistocene glaciers retreated rapidly, exposing the lake basins between 10,700 and 970014C yr B.P. The sedimentary facies suggest that after 890014C yr B.P. glaciers were absent from the watersheds and remained so during the middle Holocene. An increase in the precipitation–evaporation balance is indicated above unconformities dated to ∼230014C yr B.P. in both Lago Taypi Chaka Kkota and Laguna Viscachani. An abrupt increase in sediment accumulation rates after 140014C yr B.P. signals the onset of Neoglaciation. A possible link exists between the observed millennial-scale shifts in the regional precipitation–evaporation balance and seasonal shifts in tropical insolation.

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