Caspian Sea: State of the Environment 2019

of heat and moisture into the atmosphere is most intense, which helps the area to ventilate the en- tire sea. The Southern Caspian is the sea’s largest area, comprising 65.6 per cent of its volume and 39.5 per cent of its area, with an average depth of 345 metres. The Southern Caspian differs greatly from the Northern Caspian, not only in terms of its hydrometeorological conditions, but also in its response to climate change. The impact of climate conditions on the sea’s bi- ota is not limited to the effect of temperature on the physiology, biochemistry and behaviour of specific organisms. Rather, climate impacts the functioning of the sea’s entire ecosystem. The sensitivity of the Caspian Sea’s ecosystem to cli- mate (both the sea and its basins) is determined by several factors, such as isolation (drainless water body), morphology and consistency of the water column, among others. Due to its isolation, the Caspian Sea has only two sources of water supply: river run-off and precip- itation. The volume of water from river run-off is several times greater than the amount of pre- cipitation, which means that catchment areas are particularly sensitive to moistening. The Volga River provides a significantly larger volume of run-off than the combined flows of the remain- ing rivers, and therefore greatly influences the Caspian Sea’s water level fluctuations. As an iso- lated water body, the Caspian Sea has the poten- tial to serve as an indicator of the humidity of the East European Plain, as well as other large-scale climate changes. Anthropogenic climate change will impact the socioeconomic future of all the Caspian litto- ral states. The effects of climate change, such as the increasing frequency and intensity of ex- treme weather events, have shown that both human-made systems and natural ecosystems are vulnerable. The degree of people’s vulnera- bility largely depends on social factors, such as marginalization (IPCC 2013; IPCC 2014). The social costs of climate change are high and are closely related to impacts on ecosystems and the economy. The emission of greenhouse gases into the atmosphere today is a process of cost shift- ing, where the price of emissions will manifest through known and unknown possible future

impacts of climate change on people, ecosystems and economies. As greenhouse gas emitters, the Caspian litto- ral states are all contributing to climate change (GRID-Arendal 2011). Turkmenistan emits al- most the same volume of greenhouse gases as the Russian Federation per capita. Azerbaijan emits the least amount of CO 2 overall and per capita (Azerbaijan, State Statistical Committee of the Republic of Azerbaijan 2017), while Iran emits the second largest volume of greenhouse gases overall and per capita (The Guardian 2018). Thanks to an understanding of climate’s influ- ence on the Caspian Sea, it is possible to analyse the consequences of such influence for the 1961– 2015 period. Analysis revealed that increases in the temperature of the water’s surface layer con- tributed to a weaker winter convection as a result of cooling, and a stronger summer convection as a result of evaporation. Summer convections in the Caspian Sea did not play a particularly im- portant role in stimulating deep water mixing. In fact, the warming had a negative influence on the mixing and in recharging the upper layer of the water with biogenic elements. The period of climate warming in the Caspian re- gion can be divided into two time frames: increased river run-off, which increased the water’s level of nutrients, and decreased river run-off. In the 1980s and the first half of the 1990s, the decrease in the level of biogenic elements in the water’s deep lay- ers was supplemented by nutrients in river inflows. During this period, temperature increases encour- aged more active biochemical processes to occur, resulting in higher biological productivity in the Caspian Sea. At the start of the second half of the 1990s, the level of biogenic elements in the deep layers decreased, as did the amount of nutrients in the sea’s river inflows. The continuing rise in water temperature caused a nutritional deficiency in the sea, which led to an increase in various short-lived species and was most likely responsible for the out- break of the ctenophore Mnemiopsis leidyi 5 that oc- curred at the turn of the century. The alternation of dry and cold years with wet and warm years every 10–15 years is needed to maintain high productivity in the Caspian

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