scholarly journals Simulating thermal dynamics of the largest lake in the Caucasus region: The mountain Lake Sevan

2021 ◽  
Author(s):  
Muhammed Shikhani ◽  
Chenxi Mi ◽  
Artur Gevorgyan ◽  
Gor Gevorgyan ◽  
Amalya Misakyan ◽  
...  
Keyword(s):  
Climate Change ◽  
Algal Blooms ◽  
Thermal Structure ◽  
Meteorological Conditions ◽  
Mountain Lake ◽  
Thermal Dynamics ◽  
The Caucasus ◽  
Lake Sevan ◽  
Caucasus Region

Lake Sevan is the largest freshwater body in the Caucasus region, situated at an altitude of 1,900 m asl. While it is a major water resource in the whole region, Lake Sevan has received little attention in international limnological literature. Although recent studies pointed to algal blooms and negative impacts of climate change and eutrophication, the physical controls on thermal dynamics have not been characterized and model-based assessments of climate change impacts are lacking. We compiled a decade of historical data for meteorological conditions and temperature dynamics in Lake Sevan and used a one-dimensional hydrodynamic model (GLM 3.1) in order to study thermal structure, the stratification phenology and their meteorological drivers in this large mountain lake. We then evaluated the representativeness of meteorological data products covering almost 4 decades (EWEMBI-dataset: 1979-2016) for driving the model and found that these data are well suited to restore long term thermal dynamics in Lake Sevan. This established model setting allowed us to identify major changes in Lake Sevan’s stratification in response to changing meteorological conditions as expected from ongoing climate change. Our results point to a changing mixing type from dimictic to monomictic as Lake Sevan will experience prolonged summer stratification periods and more stable stratification. These projected changes in stratification must be included in long-term management perspectives as they will intensify water quality deteriorations like surface algal blooms or deep water anoxia.

Dissolved oxygen stratification and response to thermal structure and long-term climate change in a large and deep subtropical reservoir (Lake Qiandaohu, China)

2015 ◽  
Vol 75 ◽  
pp. 249-258 ◽  
Author(s):  
Yunlin Zhang ◽  
Zhixu Wu ◽  
Mingliang Liu ◽  
Jianbo He ◽  
Kun Shi ◽  
...  
Keyword(s):  
Climate Change ◽  
Dissolved Oxygen ◽  
Thermal Structure

scholarly journals Mediating the Effects of Climate on the Temperature and Thermal Structure of a Monomictic Reservoir through Use of Hydraulic Facilities

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1128
Author(s):  
Maurice Alfonso Duka ◽  
Tetsuya Shintani ◽  
Katsuhide Yokoyama
Keyword(s):  
Climate Change ◽  
Surface Water ◽  
Climate Warming ◽  
Thermal Structure ◽  
Heat Content ◽  
Thermal Conditions ◽  
Long Term Effects ◽  
Air Temperatures ◽  
Lower Heat

Climate warming can alter the thermal conditions of reservoirs. However, some hydraulic interventions can be explored to mitigate this impact. This study investigates the long-term effects of climate on the temperature and thermal structure of a monomictic reservoir that has had varying operations from 1959 to 2016. Reservoir progressively operated through three distinct periods, namely, (A) deep penstock withdrawal (DPW; 1959–1991), (B) purely selective withdrawal (SW; 1992–2001), and (C) combination of SW and vertical curtain (VC; 2002–2016). Although annual air temperatures are increasing (+0.15 °C decade−1) in the long term, the reservoir’s surface water temperatures have been found to be decreasing (−0.06 °C decade−1). Periods B and C produced colder profiles and exhibited lower heat content and higher potential energy anomaly than Period A. Furthermore, stronger thermoclines, as indicated by Brunt–Vaisala frequency, were observed in the two latter periods. The results of this study show that varying operations bear a stronger influence on the reservoir’s temperature and thermal structure than climate change itself. Mitigating the thermal impacts of climate warming in reservoirs appears promising with the use of SW and VC.

Impact of climate change on steppe environments around Lake Sevan in Armenia during the Holocene

2020 ◽  
Author(s):  
Mary Robles ◽  
Odile Peyron ◽  
Guillemette Ménot ◽  
Elisabetta Brugiapaglia ◽  
Vincent Ollivier ◽  
...  
Keyword(s):  
Climate Change ◽  
Aquatic Vegetation ◽  
Climate Reconstruction ◽  
Neolithic Period ◽  
The Caucasus ◽  
Lake Sevan ◽  
The Holocene ◽  
Impact Of Climate Change ◽  
Climate Reconstructions ◽  
The Impact

<p>Armenia is located in the Caucasus Mountains and today, its vegetation is largely dominated by steppes closely linked with human practices. Armenian human history roots back to the Neolithic period, which questions long human influences on steppe and therefore climate reconstructions from vegetation data. Moreover, vegetation records from this region are often low resolution and do not cover the entire Holocene. Pollen-based climate reconstruction coupled to independent climate reconstructions appear necessary to fully understand climate forcing in the region during the Holocene. In this study, we introduce high-resolution pollen, geochemical analyses and temperature reconstruction based on pollen and branched glycerol dialkyl glycerol tetraethers (brGDGTs) from Vanevan peat in Armenia. The wetland studied show major ecological changes observed through aquatic vegetation and sediment composition (XRF data). At the beginning of the Holocene, the study site is expected to be integrated in a larger Lake Sevan, then it became an independent lake and finally a peatland at 5700 cal BP. A drying phase is also attested around 4.2 kyrs, probably corresponding to the 4.2 ka climate event. Along the sequence, the vegetation is characterized by steppes dominated by Poaceae, Artemisia and Chenopodiaceae. However, forests composed of Quercus, Betula, Carpinus betulus and Ulmus, are more developed on slopes between 7600 cal BP and 5500 cal BP. Agriculture is observed since 5700 cal BP and correlates with occupation periods reported in archeological studies. Over this 10000 yrs-long record, we suppose that differences in response of wetland and vegetation to climate might be linked to ecological processes and human influence. The comparison between pollen-based climate reconstruction and temperature obtained with brGDGT calibrations promisingly illustrate these differences. Finally, we contextualize these results with other regional records to understand the impact of climate change on steppe vegetation in the Caucasus at a larger scale.</p>

scholarly journals Climate Change Effects on Aquaculture Production: Sustainability Implications, Mitigation, and Adaptations

2021 ◽  
Vol 5 ◽  
Author(s):  
Sahya Maulu ◽  
Oliver J. Hasimuna ◽  
Lloyd H. Haambiya ◽  
Concillia Monde ◽  
Confred G. Musuka ◽  
...  
Keyword(s):  
Climate Change ◽  
Harmful Algal Blooms ◽  
Algal Blooms ◽  
Sea Surface Salinity ◽  
Mitigation Measures ◽  
Negative Effects ◽  
Surface Salinity ◽  
Climate Change Effects ◽  
Aquaculture Production

Aquaculture continues to significantly expand its production, making it the fastest-growing food production sector globally. However, the sustainability of the sector is at stake due to the predicted effects of climate change that are not only a future but also a present reality. In this paper, we review the potential effects of climate change on aquaculture production and its implications on the sector's sustainability. Various elements of a changing climate, such as rising temperatures, sea-level rise, diseases and harmful algal blooms, changes in rainfall patterns, the uncertainty of external inputs supplies, changes in sea surface salinity, and severe climatic events have been discussed. Furthermore, several adaptation options have been presented as well as some gaps in existing knowledge that require further investigations. Overall, climate change effects and implications on aquaculture production sustainability are expected to be both negative and positive although, the negative effects outweigh the positive ones. Adapting to the predicted changes in the short-term while taking mitigation measures in the long-term could be the only way toward sustaining the sector's production. However, successful adaptation will depend on the adaptive capacity of the producers in different regions of the world.

scholarly journals Long-term influence of climate and experimental eutrophication regimes on phytoplankton blooms

2019 ◽  
Author(s):  
Kateri R. Salk ◽  
Jason J. Venkiteswaran ◽  
Raoul-Marie Couture ◽  
Scott N. Higgins ◽  
Michael J. Paterson ◽  
...  
Keyword(s):  
Climate Change ◽  
Algal Blooms ◽  
Nutrient Loading ◽  
Data Availability ◽  
Change Scenario ◽  
Nutrient Loads ◽  
Phytoplankton Blooms ◽  
Experimental Lakes Area ◽  
Link Type

AbstractPhytoplankton blooms respond to multiple drivers, including climate change and nutrient loading. Here we examine a long-term dataset from Lake 227, a site exposed to a fertilization experiment (1969–present). Changes in nitrogen:phosphorus loading ratios (high N:P, low N:P, P-only) did not impact mean annual biomass, but blooms exhibited substantial inter- and intra-annual variability. We used a process-oriented lake model, MyLake, to successfully reproduce lake physics over 48 years and test if a P-limited model structure predicted blooms. The timing and magnitude of blooms was reproduced during the P-only period but not for the high and low N:P periods, perhaps due to N acquisition pathways not currently included in the model. A model scenario with no experimental fertilization confirmed P loading is the major driver of blooms, while a scenario that removed climate-driven temperature trends showed that increased spring temperatures have exacerbated blooms beyond the effects of fertilization alone.Significance StatementHarmful algal blooms and eutrophication are key water quality issues worldwide. Managing algal blooms is often difficult because multiple drivers, such as climate change and nutrient loading, act concurrently and potentially synergistically. Long-term datasets and simulation models allow us to parse the effects of interacting drivers of blooms. The performance of our model depended on the ratio of nitrogen to phosphorus inputs, suggesting that complex biological dynamics control blooms under variable nutrient loads. We found that blooms were dampened under a “no climate change” scenario, suggesting that the interaction of nutrient loading and increased temperature intensifies blooms. Our results highlight successes and gaps in our ability to model blooms, helping to establish future management recommendations.Data Availability StatementData and metadata will be made available in a GitHub repository (https://github.com/biogeochemistry/Lake-227). Upon manuscript acceptance, the repository will be made publicly available and a DOI will be provided. We request that data users contact the Experimental Lakes Area directly, per their data use policy (http://www.iisd.org/ela/wp-content/uploads/2016/04/Data-Terms-And-Conditions.pdf).

scholarly journals South Caucasus Region in the context of new geopolitical realities: "Transcaucasia" or "Greater Middle East"

2021 ◽  
pp. 20
Author(s):  
Norayr Dunamalyan
Keyword(s):  
Central Asia ◽  
New World ◽  
World Order ◽  
New World Order ◽  
The South ◽  
South Caucasus ◽  
The Caucasus ◽  
Caucasus Region ◽  
Rapid Changes

The events taking place on the periphery of the Heartland show a clear connection between the processes in the South Caucasus and Central Asia. The fact is that the independent republics (recognized and unrecognized) must still take their place in the new world order, as demonstrated by the turbulent 2020 in the Caucasus and the rapid changes in Central Asia (Tajikistan, Kyrgyzstan, Afghanistan). All these plots have their own logic and content. In this article, we will pay more attention to the South Caucasus, the countries of which, despite their long-term neighborhood, exist in various regional, cultural and political spaces with all its consequences.

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