Abstract: The article considers the current problems of predicting the Earth's collision with asteroids and comets. Mathematical modeling of analyzed process of asteroids falling into oceans and seas is especially complex. Such models are based on solving the classical Euler-Navier-Stokes equations. The relevance of abovementioned problem is also justified by a number of features of the Black Sea basin, including the presence of a large amount of hydrogen sulfide and methane. An estimate of the concentration of hydrogen sulfide in the air during an asteroid fall into the Black Sea was obtained. It is shown that the main emission is associated with expected release of deep waters to the surface in the area of the fall, due to which the concentration of hydrogen sulfide in the surface layer of the atmosphere can reach one gram / cubic meter. In the cloud formed by the steam emission, the concentration of hydrogen sulfide does not exceed 0.04 gram/cubic meter.
Based on obtained results of their study, authors come to conclusion that the content of hydrogen sulfide in the steam, and then in resulting cloud, is half the dangerous values at which the evacuation of the population is necessary. The principal difference between an asteroid hitting water and hitting a solid surface is that it does not immediately explode or melt but goes under water. In certain areas of the sea, the fall of an asteroid to the bottom can cause methane emissions, including due to the melting of gas hydrates. In this case, an explosive concentration of the gas-air mixture can be achieved. Perhaps the greatest danger is associated with the impact of the asteroid on the bottom and the subsequent exit of deep waters to the surface.

Abstract: The relevance of this study is due to the fact that the Black Sea is the largest body of water with a hydrogen sulfide zone. The proven reserves of hydrogen sulfide in the water column of the Black Sea amount to five billion tons. In terms of volume, this corresponds to 3.5 trillion cubic meters. At the same time, a mixture of hydrogen sulfide with air is explosive starting with a concentration of hydrogen sulfide in the air of 50 g/ m3. In addition, hydrogen sulfide is toxic, since it is a nerve gas, deadly already at 1 g/ m3. It is of interest to assess the possibility of the release of hydrogen sulfide waters of the sea to the surface with their subsequent degassing, as well as the consequences of increasing the concentration of hydrogen sulfide in surface waters and in the air for coastal areas.  The distribution of hydrogen sulfide in the Black Sea is well studied. Especially a lot of measurement data was obtained for the top layer at a depth of 1000 m. Data on the concentration of hydrogen sulfide at depths from 1000 m to 2000 m is significantly less for technical reasons. The maximum concentration of hydrogen sulfide in the sea is reached at depths above 1500 m. A numerical assessment of the consequences of the release of deep waters to the surface has been obtained. It is shown that the concentration of hydrogen sulfide in the air will not exceed 1 g/m3, which is almost two orders of magnitude less than the explosive concentration. The balance estimates of oxygen and hydrogen sulfide fluxes in the Black Sea are considered in connection with forecasts of a rise in the boundary of the hydrogen sulfide zone. It is shown that the rise of the boundary is a consequence of the imbalance of these flows, however, the amount of net hydrogen sulfide production cannot be estimated accurately enough. With an accuracy of estimates of the fluxes themselves of 20–30%, the resulting increase in the amount of hydrogen sulfide per year is a statistically insignificant amount. The release of hydrogen sulfide to the surface in the foreseeable future is possible if the stratification of waters is disrupted by mechanical intervention.

Abstract: The possibility of a repetition of the limnological catastrophe in the Black Sea is considered. It is shown that, in contrast to the volcanic lakes of Africa Nyos and Manun, where limnological catastrophes occurred in the 1980s, the concentration of dissolved gases in deep waters is significantly less than the saturation value. This eliminates the mechanism of so called “eruption” of carbon dioxide such as gas lift. However, on a smaller scale, significant methane releases are possible during strong eruptions of underwater mud volcanoes. The mechanism for the release of carbon dioxide from the lake into the atmosphere is so similar to a volcanic eruption that mathematical models developed for ordinary volcanoes are used to describe it. In both cases, the rise of erupted masses occurs due to an increase in the buoyancy of the gas-liquid mixture, which carries with it particles of the environment. The formation and growth of gas bubbles at intermediate depths occurs provided that the total partial pressure of all gases inside the bubble exceeds the hydrostatic pressure at a given depth. The article shows that the concentration of dissolved methane in the Black Sea is much less than the saturation level. Due to the relatively low solubility of methane in water, methane bubbles are able to overcome a significant depth range. And as additional components of the gas mixture, together with methane, carbon dioxide and hydrogen sulfide can thus enter the atmosphere. It was concluded that as the water temperature in the Black Sea increases due to climate change, the reserves of methane gas hydrate at the bottom of the sea will begin to decompose, which will also be accompanied by jet gas release. At the same time, methane can escape to the surface from depths of no more than 900 m.

Abstract: The North Crimean Canal is considered as a continuation of the Dnieper River. This makes it possible to analyze its overlap in 2014 as one of the classic problems of transboundary water use associated with partial or complete restriction of flow in the middle or lower reaches of the river. As a similar example, the conflict between Turkey and Syria over the water resources of the Euphrates River is considered. It is shown that such cross-border conflicts are often caused by both economic reasons and arise in connection with a decrease in runoff in some years due to increased aridity of the climate. This article presents game-theoretic models of interaction between the parties and substantiates the need for compensation payments between the countries participating in a cross-border dispute. Based on the results of the analysis carried out in this article, it was concluded that one of the consequences of the possible destruction of the dam of the Kakhovsky reservoir will be the cessation of water supply to the North Crimean Canal. The fact is that in the first section with a length of more than 200 km, water from the reservoir flows into the channel by gravity, so that when the level drops at the water intake point by 16 m, the filling of the channel will stop.

Abstract: This article is dedicated to assessment of the climate changes of the Republic of Crimea over the last few decades. Throughout the analysis, the research utilized data on air temperature changes in the temperate latitudes of Europe by paleoclimatic data, as well as by changes in average temperature of surface waters in the Black Sea according coastal measurements. It is demonstrated that on the background of global warming there are natural manifestations of climatic fluctuations with periods of up to 20 years that relate to warm episodes such as El Niño and North-Atlantic fluctuation. The research methodology is based on the modern theory of global warming, which replaced the Milankovitch cycles concept used until the 1980’s. One of the main consequences of global warming for Russia lies in the significant increase in the frequency of reoccurrence of dangerous hydrometeorological phenomena. Examples of such phenomena include strong floods and heat waves. In a number of regions, the increase in temperature is also accompanied by spread of agents of dangerous diseases – ticks and marsh mosquitoes. However, the most notable damage caused by the climate change in Russia comes from drought.