scholarly journals The Holocene lake-evaporation history of the afro-alpine Lake Garba Guracha in the Bale Mountains, Ethiopia, based on δ18O records of sugar biomarker and diatoms

2021 ◽  
pp. 1-14
Author(s):  
Lucas Bittner ◽  
Graciela Gil-Romera ◽  
Dai Grady ◽  
Henry F. Lamb ◽  
Eva Lorenz ◽  
...  
Keyword(s):  
Lake Water ◽  
Regional Climate ◽  
Regional Climate Change ◽  
Eastern Africa ◽  
The Holocene ◽  
Evaporation Ratio ◽  
History Of ◽  
Lake Evaporation ◽  
High Altitude Lake ◽  
Specific Sugar

Abstract In eastern Africa, there are few long, high-quality records of environmental change at high altitudes, inhibiting a broader understanding of regional climate change. We investigated a Holocene lacustrine sediment archive from Lake Garba Guracha, Bale Mountains, Ethiopia, (3,950 m asl), and reconstructed high-altitude lake evaporation history using δ18O records derived from the analysis of compound-specific sugar biomarkers and diatoms. The δ18Odiatom and δ18Ofuc records are clearly correlated and reveal similar ranges (7.9‰ and 7.1‰, respectively). The lowest δ18O values occurred between 10–7 cal ka BP and were followed by a continuous shift towards more positive δ18O values. Due to the aquatic origin of the sugar biomarker and similar trends of δ18Odiatom, we suggest that our lacustrine δ18Ofuc record reflects δ18Olake water. Therefore, without completely excluding the influence of the ‘amount-effect’ and the ‘source-effect’, we interpret our record to reflect primarily the precipitation-to-evaporation ratio (P/E). We conclude that precipitation increased at the beginning of the Holocene, leading to an overflowing lake between ca. 10 and ca. 8 cal ka BP, indicated by low δ18Olake water values, which are interpreted as reduced evaporative enrichment. This is followed by a continuous trend towards drier conditions, indicating at least a seasonally closed lake system.

The Impact of Climate Change on the River Jordan-Lake Kinneret (Israel) Ecosystem

2020 ◽  
pp. 1-12
Author(s):  
Moshe Gophen
Keyword(s):  
Climate Change ◽  
Lake Water ◽  
Regional Climate ◽  
Nitrogen Deficiency ◽  
Regional Climate Change ◽  
Lake Kinneret ◽  
Ecosystem Structure ◽  
Nutrient Inputs ◽  
Lake Water Level ◽  
The Impact

The long-term record of River Jordan-Lake Kinneret ecosystem indicates some significant climate condition changes: water temperature increase, decline in rainfall, and diminishing river discharges and lake water inflows accompanied by a reduction in nitrogen and a slight increase in phosphorus in the Lake upper layers (Epilimnion). Lake Water level decreased, Prolongation of Residence Time was documented, nutrient inputs and dynamics modifications resulting water quality deterioration. As a result of temperature elevation and nitrogen deficiency, the biomass of Peridinium spp significantly reduced and was replaced by Cyanobacterial biomass enhancement. Dryness trend expressed as enhanced frequency of drought seasons initiated an elevation of lake water salinity. It has been suggested that these changes in the phytoplankton community structure are caused by regional climate change. This study evaluates a multi-annual respective approach although the summer is the most critical. The objective of this research is evaluate the background of the ecosystem structure modification aimed at define future potential management design.

Holocene lake water-aquifer interactions in La Ballestera Playa-lake (southern Spain) recorded by stable isotopes (δ18O and δD) of gypsum hydration water

2021 ◽  
Author(s):  
Fernando Gazquez ◽  
Antonio García-Alix ◽  
Gonzalo Jiménez-Moreno ◽  
Francisco Jíménez-Espejo ◽  
Miguel Rodríguez-Rodríguez
Keyword(s):  
Stable Isotopes ◽  
Lake Water ◽  
Environmental Conditions ◽  
Sediment Cores ◽  
Southern Spain ◽  
Hydration Water ◽  
The Holocene ◽  
Playa Lake ◽  
Lake Evaporation ◽  
Southern Iberia

<p>Oxygen and hydrogen stable isotopes (δ<sup>18</sup>O and δD) of lake water are sensitive to long-term changes in environmental conditions, including relative humidity, temperature and the evaporation/outflow ratio of the lake. Lacustrine gypsum (CaSO<sub>4</sub>·2H<sub>2</sub>O) forms in equilibrium with its parent fluid, so the isotopic composition of its structurally bonded hydration water (GHW) can reflect the δ<sup>18</sup>O and δD of lake water at the time of mineral formation, with insignificant effects of temperature and salinity on the water-GHW isotope fractionation factors. Using the stable isotope content of gypsum-rich sediment cores as a paleoclimatic proxy, the environmental conditions prevailing in the lake setting at the time of gypsum crystallization can be investigated.</p><p>Here we apply this method to reconstruct the δ<sup>18</sup>O and δD of paleo-water in La Ballestera Playa-lake (Seville, southern Spain) throughout the Holocene, from 11.2 cal kyr BP to the present. Gypsum crystallization took place punctually at 11.2 and 4.4 cal kyr BP, and did continuously from 2.9 cal kyr BP to the present. The δ<sup>18</sup>O and δD showed the lowest values at ~11.2 cal kyr BP (2.3‰ and -1.1‰, respectively) and were significantly higher at ~4.4 cal kyr BP (8.8‰ and 29.2‰, respectively). Likewise, relatively higher values (8.2‰ and 29.8‰, respectively) were recorded at ~2.9 cal kyr BP. Thereafter, the isotopic ratios increased until the present (11.4‰ and 37.1‰, respectively), suggesting increasing aridity and/or hydrological closeness of the lake. A relative minimum in δ<sup>18</sup>O and δD occurred at ~2.3 cal kyr BP, during the wetter stage of the Iberian Roman Humid Period, while a relative maximum at ~1.1 cal kyr BP was recorded during the Medieval Warm Period.</p><p>We use a steady-state Isotope Mass Balance to investigate the paleo-hydrological conditions in the lake setting at different stages of the Holocene. Our results suggest that at ~11.2 cal kyr BP La Ballestera Playa-lake was a flow-through lake closely connected to the aquifer with and evaporation/outflow ratio <0.5. At 4.4 cal kyr BP and from ~2.9 cal kyr BP until the present, the system behaved as a terminal lake (evaporation/outflow ratio close to 1), with less connection to the aquifer and the main water output occurred via evaporation. The studied system turned into a playa lake because of a regional water table lowering. This most likely resulted from increasing aridity in southern Iberia during the late Holocene, which has previously been suggested by other lake sediment records in this region. </p><p> </p><p><strong>Acknowledgement</strong></p><p>This study was supported by the Junta del Andalucía PY18-871 to FG, the project<strong> </strong>CGL2017-85415-R of the Ministerio de Economía y Competitividad of Spain and Fondo Europeo de Desarrollo Regional FEDER, the project B-RNM-144-UGR18, Proyectos I+D+i del Programa Operativo FEDER 2018 and the research groups RNM-189 y RNM-190 (Junta de Andalucía). Dr. Antonio García-Alix acknowledges the Ramón y Cajal fellowship, RYC-2015-18966. Fernando Gázquez acknowledges the postdoctoral “HIPATIA” program of University of Almería.</p>

Terminal Pleistocene/Early Holocene Environmental Change at the Sunshine Locality, North-Central Nevada, U.S.A.

2001 ◽  
Vol 55 (3) ◽  
pp. 303-312 ◽  
Author(s):  
Gary Huckleberry ◽  
Charlotte Beck ◽  
George T. Jones ◽  
Amy Holmes ◽  
Michael Cannon ◽  
...  
Keyword(s):  
Environmental Change ◽  
Great Basin ◽  
Sand Dunes ◽  
Regional Climate ◽  
Regional Climate Change ◽  
Early Holocene ◽  
Faunal Remains ◽  
North Central ◽  
History Of ◽  
Terminal Pleistocene

AbstractSedimentological, faunal, and archaeological investigations at the Sunshine Locality, Long Valley, Nevada reveal a history of human adaptation and environmental change at the last glacial–interglacial transition in North America's north-central Great Basin. The locality contains a suite of lacustrine, alluvial, and eolian deposits associated with fluvially reworked faunal remains and Paleoindian artifacts. Radiocarbon-dated stratigraphy indicates a history of receding pluvial lake levels followed by alluvial downcutting and subsequent valley filling with marsh-like conditions at the end of the Pleistocene. A period of alluvial deposition and shallow water tables (9,800 to 11,000 14C yr B.P.) correlates to the Younger Dryas. Subsequent drier conditions and reduced surface runoff mark the early Holocene; sand dunes replace wetlands by 8,000 14C yr B.P. The stratigraphy at Sunshine is similar to sites located 400 km south and supports regional climatic synchroneity in the central and southern Great Basin during the terminal Pleistocene/early Holocene. Given regional climate change and recurrent geomorphic settings comparable to Sunshine, we believe that there is a high potential for buried Paleoindian features in primary association with extinct fauna elsewhere in the region yet to be discovered due to limited stratigraphic exposure and consequent low visibility.

Influence of Late Holocene climate on Lake Eggers hydrology, McMurdo Sound

2021 ◽  
pp. 1-13
Author(s):  
E.J. Chamberlain ◽  
A.J. Christ ◽  
R.W. Fulweiler
Keyword(s):  
Late Holocene ◽  
Ross Sea ◽  
Regional Climate ◽  
Ice Cores ◽  
Lake Ice ◽  
Mcmurdo Sound ◽  
Ice Accumulation ◽  
History Of ◽  
Ground Penetrating ◽  
Western Ross Sea

Abstract Ice-covered lakes in Antarctica preserve records of regional hydroclimate and harbour extreme ecosystems that may serve as terrestrial analogues for exobiotic environments. Here, we examine the impacts of hydroclimate and landscape on the formation history of Lake Eggers, a small ice-sealed lake, located in the coastal polar desert of McMurdo Sound, Antarctica (78°S). Using ground penetrating radar surveys and three lake ice cores we characterize the ice morphology and chemistry. Lake ice geochemistry indicates that Lake Eggers is fed primarily from local snowmelt that accreted onto the lake surface during runoff events. Radiocarbon ages of ice-encased algae suggest basal ice formed at least 735 ± 20 calibrated years before present (1215 C.E.). Persisting through the Late Holocene, Lake Eggers alternated between periods of ice accumulation and sublimation driven by regional climate variability in the western Ross Sea. For example, particulate organic matter displayed varying δ15N ratios with depth, corresponding to sea ice fluctuations in the western Ross Sea during the Late Holocene. These results suggest a strong climatic control on the hydrologic regime shifts shaping ice formation at Lake Eggers.

scholarly journals Incorrect Asian aerosols affecting the attribution and projection of regional climate change in CMIP6 models

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Zhili Wang ◽  
Lei Lin ◽  
Yangyang Xu ◽  
Huizheng Che ◽  
Xiaoye Zhang ◽  
...  
Keyword(s):  
Climate Change ◽  
Radiative Forcing ◽  
Impact Analysis ◽  
Climate Model ◽  
Regional Climate ◽  
Eastern China ◽  
Coupled Model ◽  
Regional Climate Change ◽  
Anthropogenic Aerosol ◽  
Wide Range

AbstractAnthropogenic aerosol (AA) forcing has been shown as a critical driver of climate change over Asia since the mid-20th century. Here we show that almost all Coupled Model Intercomparison Project Phase 6 (CMIP6) models fail to capture the observed dipole pattern of aerosol optical depth (AOD) trends over Asia during 2006–2014, last decade of CMIP6 historical simulation, due to an opposite trend over eastern China compared with observations. The incorrect AOD trend over China is attributed to problematic AA emissions adopted by CMIP6. There are obvious differences in simulated regional aerosol radiative forcing and temperature responses over Asia when using two different emissions inventories (one adopted by CMIP6; the other from Peking university, a more trustworthy inventory) to driving a global aerosol-climate model separately. We further show that some widely adopted CMIP6 pathways (after 2015) also significantly underestimate the more recent decline in AA emissions over China. These flaws may bring about errors to the CMIP6-based regional climate attribution over Asia for the last two decades and projection for the next few decades, previously anticipated to inform a wide range of impact analysis.

scholarly journals Post-abortion family planning use, method preference, and its determinant factors in Eastern Africa: a systematic review and meta-analysis

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Asmamaw Demis Bizuneh ◽  
Getnet Gedefaw Azeze
Keyword(s):  
Family Planning ◽  
Marital Status ◽  
Meta Analysis ◽  
Grey Literature ◽  
Eastern Africa ◽  
Determinant Factors ◽  
Unintended Pregnancies ◽  
Pooled Prevalence ◽  
History Of ◽  
Post Abortion

Abstract Background Utilization of post-abortion family planning is very critical to reduce high levels of unintended pregnancy, which is the root cause of induced abortion. In Eastern Africa, it is estimated that as many as 95% of unintended pregnancies occurred among women who do not practice contraception at all. Therefore, this meta-analysis aimed to assess post-abortion family planning utilization and its determinant factors in Eastern Africa. Methods Published papers from Scopus, HINARI, PubMed, Google Scholar, and Web of Science electronic databases and grey literature repository were searched from database inception to January 30, 2020, with no restriction by design and date of publishing. We screened records, extracted data, and assessed risk of bias in duplicate. Cochrane I2 statistics were used to check the heterogeneity of the studies. Publication bias was assessed by Egger and Biggs test with a funnel plot. A random-effects model was calculated to estimate the pooled prevalence of post-abortion family planning utilization. Results A total of twenty-nine cross-sectional studies with 70,037 study participants were included. The overall pooled prevalence of post-abortion family planning utilization was 67.86% (95% CI 63.59–72.12). The most widely utilized post-abortion family methods were injectable 33.23% (95% CI 22.12–44.34), followed by implants 24.71% (95% CI 13.53–35.89) and oral contraceptive pills 23.42% (95% CI 19.95–26.89). Married marital status (AOR=3.20; 95% CI 2.02–5.05), multiparity (AOR=3.84; 95% CI 1.43–10.33), having a history of abortion (AOR=2.33; 95% CI 1.44–3.75), getting counselling on post-abortion family planning (AOR=4.63; 95% CI 3.27–6.56), and ever use of contraceptives (AOR=4.63; 95% CI 2.27–5.21) were factors associated with post-abortion family planning utilization in Eastern Africa. Conclusions This study revealed that the marital status of the women, multiparity, having a history of abortion, getting counselling on post-abortion family planning, and ever used contraceptives were found to be significantly associated with post-abortion family planning utilization.

scholarly journals Regional Climate Change Competitiveness—Modelling Approach

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3704
Author(s):  
Agnieszka Karman ◽  
Andrzej Miszczuk ◽  
Urszula Bronisz
Keyword(s):  
Climate Change ◽  
Regional Climate ◽  
Regional Climate Change ◽  
Measurement Scale ◽  
Practical Application ◽  
Adaptation To Climate Change ◽  
Regional Competitiveness ◽  
The Face ◽  
Competitiveness Index ◽  
Modelling Approach

The article deals with the competitiveness of regions in the face of climate change. The aim was to present the concept of measuring the Regional Climate Change Competitiveness Index. We used a comparative and logical analysis of the concept of regional competitiveness and heuristic conceptual methods to construct the index and measurement scale. The structure of the index includes six broad sub-indexes: Basic, Natural, Efficiency, Innovation, Sectoral, Social, and 89 indicators. A practical application of the model was presented for the Mazowieckie province in Poland. This allowed the region’s performance in the context of climate change to be presented, and regional weaknesses in the process of adaptation to climate change to be identified. The conclusions of the research confirm the possibility of applying the Regional Climate Change Competitiveness Index in the economic analysis and strategic planning. The presented model constitutes one of the earliest tools for the evaluation of climate change competitiveness at a regional level.

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