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One of the most important physical characteristics driving lifecycle events in lakes is stratification. Already subtle variations in the timing of stratification onset and break-up (phenology) are known to have major ecological effects, mainly by determining the availability of light, nutrients, carbon and oxygen to organisms. Despite its ecological importance, historic and future global changes in stratification phenology are unknown. Here, we used a lake-climate model ensemble and long-term observational data, to investigate changes in lake stratification phenology across the Northern Hemisphere from 1901 to 2099. Under the high-greenhouse-gas-emission scenario, stratification will begin 22.0 ± 7.0 days earlier and end 11.3 ± 4.7 days later by the end of this century. It is very likely that this 33.3 ± 11.7 day prolongation in stratification will accelerate lake deoxygenation with subsequent effects on nutrient mineralization and phosphorus release from lake sediments. Further misalignment of lifecycle events, with possible irreversible changes for lake ecosystems, is also likely.

Nitrogen is one of the most abundant chemical elements on the Earth and plays an important role in global environmental change. Leading Earth system models include coupled carbon and nitrogen cycle modules of varying complexity, but the INM RAS climate model family has not yet included an explicit N-cycle description. This paper presents a parameterization of the terrestrial N-cycle based on a simplification of the JULES-CN model, adapted for coupled use with the INM-CM land C-cycle module. Numerical simulations were carried out with a standalone carbon cycle model with nitrogen feedback disabled and enabled versions for the period 1850–2100. The simulated global pools show good agreement with results of other models with an implemented N-cycle. Taking into account the N-limitation of the C-cycle, the modelled dynamics of total carbon storage in terrestrial ecosystems from 1850 to the mid-20th century is specified. [ABSTRACT FROM AUTHOR]

The mechanistic model LAKE2.3 was tested for its capability to predict of methane (CH4) emissions from reservoirs. Estimates of CH4 emissions from the Mozhaysk reservoir (Moscow region) provided by the model showed good agreement with instrumental in situ observations for several parameters of the water ecosystem. The average CH4 flux calculated by the model is 37.7 mgC-CH4 m−2 day−1, while according to observations, it is 34.4 mgC-CH4 m−2 day−1. Ebullition makes the largest contribution to the emissions from reservoirs (up to 95%) due to low methane solubility in water and the high oxidation rate of diffusive methane flux. During the heating period, an increase in methane emission is observed both in the model and empirical data, with a maximum before the onset of the autumn overturn. An effective parameter for calibrating the diffusive methane flux in the model is the potential rate of methane oxidation. For ebullition flux, it is the parameter q10 (an empirical parameter determining the relationship between methane generation and temperature) because methane production in bottom sediments is the most important. The results of this research can be used to develop mechanistic models and provide a necessary step toward regional and global simulations of lacustrine methane emission using LAKE2.3. [ABSTRACT FROM AUTHOR]

The Arctic is warming at an above-average rate, and small, shallow waterbodies such as ponds are vulnerable to this warming due to their low thermal inertia compared to larger lakes. While ponds are a relevant landscape-scale source of methane under the current climate, the response of pond methane emissions to warming is uncertain. We employ a new, process-based model for methane emissions from ponds (MeEP) to investigate the methane emission response of polygonal-tundra ponds in northeastern Siberia to warming. MeEP is the first dedicated model of pond methane emissions which differentiates between the three main pond types of the polygonal-tundra, ice-wedge, polygonal-center, and merged polygonal ponds and resolves the three main pathways of methane emissions – diffusion, ebullition, and plant-mediated transport. We perform idealized warming experiments, with increases in the mean annual temperature of 2.5, 5, and 7.5 ∘ C on top of a historical simulation. The simulations reveal an approximately linear increase in emissions from ponds of 1.33 g CH 4 yr -1 ∘ C -1 m -2 in this temperature range. Under annual temperatures 5 ∘ C above present temperatures, pond methane emissions are more than 3 times higher than now. Most of this emission increase is due to the additional substrate provided by the increased net productivity of the vascular plants. Furthermore, plant-mediated transport is the dominating pathway of methane emissions in all simulations. We conclude that vascular plants as a substrate source and efficient methane pathway should be included in future pan-Arctic assessments of pond methane emissions. [ABSTRACT FROM AUTHOR]

We present the first mechanistic model LAKE2.3 for prediction of methane emissions from artificial reservoirs. Estimates of CH4 emissions from the Mozhaysk reservoir (Moscow region) surface provided by the model are demonstrated. The annual emission value was 361 tC-CH4 yr-1, the average flux 37.7 mgC-CH4 m-2 day-1. The methane emission according to the model were shown to be in good agreement with the observation data. The ebullition makes the largest contribution to the total emission (up to 95 %). During the heating period, an increase of methane emission is observed both in the model and empirical data with a maximum before the onset of the autumn overturn. Effective parameter for calibrating the diffusion component of methane flux in the model is the potential rate of methane oxidation in the Michaelis-Menten reaction, and the same for ebullition is the temperature dependence parameter for methane production in bottom sediments - q10. [ABSTRACT FROM AUTHOR]

The issues of civil society in post-communist Ukraine are analyzed, which were actualized during the Orange Revolution at the end of 2004. Results lead to the conclusion that optimistic perspectives for the Ukrainian civil society can be related to the trends in the transformation of personal identity toward the more self-reliable pattern of social activity, while the institutional structures of the civil society need popular support, need the people to be effective and helpful.