Modeling Caspian Sea water level oscillations under different scenarios of increasing atmospheric carbon dioxide concentrations

Abstract

The rapid rise of Caspian Sea water level (about 2.25 meters since 1978) has caused much concern to all five surrounding countries, primarily because flooding has destroyed or damaged buildings and other engineering structures, roads, beaches and farm lands in the coastal zone. Given that climate, and more specifically climate change, is a primary factor influencing oscillations in Caspian Sea water levels, the effect of different climate change scenarios on future Caspian Sea levels was simulated. Variations in environmental parameters such as temperature, precipitation, evaporation, atmospheric carbon dioxide and water level oscillations of the Caspian sea and surrounding regions, are considered for both past (1951-2006) and future (2025-2100) time frames. The output of the UKHADGEM general circulation model and five alternative scenarios including A1CAI, BIASF, BIMES WRE450 and WRE750 were extracted using the MAGICC SCENGEN Model software (version 5.3). The results suggest that the mean temperature of the Caspian Sea region (Bandar-E-Anzali monitoring site) has increased by ca. 0.17°C per decade under the impacts of atmospheric carbon dioxide changes (r=0.21). The Caspian Sea water level has increased by ca. +36cm per decade (r=0.82) between the years 1951-2006. Mean results from all modeled scenarios indicate that the temperature will increase by ca. 3.64°C and precipitation will decrease by ca. 10% (182 mm) over the Caspian Sea, whilst in the Volga river basin, temperatures are projected to increase by ca. 4.78°C and precipitation increase by ca. 12% (58 mm) by the year 2100. Finally, statistical modeling of the Caspian Sea water levels project future water level increases of between 86 cm and 163 cm by the years 2075 and 2100, respectively.

Long‐term Caspian Sea level change

“…The original Volga river discharge fluxes (in units m 3 /s) are converted into equivalent monthly CSL height change rates, by evenly allocating the monthly integrated Volga discharge water volumes over the Caspian Sea (using an area of~371,000 km 2 ). The Volga river is believed to account for~80% of total discharge (or runoff) into the Caspian Sea [Arpe et al, 2000;Ozyavas et al, 2010;Roshan et al, 2012]. However, considering year-to-year fluctuations of climatic conditions in different river basins, the actual percentage of the Volga's share would be expected to fluctuate.…”

“…As an enclosed basin, CSL variation is controlled mainly by water inflow from rivers and precipitation, and loss from evaporation and discharge to the Kara-Bogaz-Gol (KBG) Bay [Kosarev et al, 2009]. With a relatively wet climate, it contributes over 80% of total influx to the Caspian Sea [Arpe et al, 2000;Renssen et al, 2007;Ozyavas et al, 2010;Roshan et al, 2012]. The length of the Caspian Sea watershed from north to south is about 2500 km and from west to east is about 1000 km [Zonn and Kostianoy, 2016].…”

“…The Volga river basin to the north comprises more than half the catchment, with an area of~1.38 × 10 6 km 2 . With a relatively wet climate, it contributes over 80% of total influx to the Caspian Sea [Arpe et al, 2000;Renssen et al, 2007;Ozyavas et al, 2010;Roshan et al, 2012].…”

“…large-magnitude increase and decrease evident during the past several decades, prediction of CSL is challenging. Long-term CSL trends predicted by different climate models show substantially large discrepancy and are often contradictory with each other [e.g., Elguindi and Giorgi, 2006;Roshan et al, 2012]. The main motivation of the present study is to develop an understanding of these past changes through a comprehensive analysis of historical tide gauge measurements and more recent satellite altimeter observations [Lebedev and Kostianoy, 2008;Cretaux et al, 2016;Chen et al, 2017], observed river discharge (R), and climate model estimates of precipitation (P) and evaporation (E) fluxes.…”

Considering Climate Change in the Estimation of Long‐Term Flood Risks of Devils Lake in North Dakota

“…The main driver of this decline is excessive irrigation water abstraction from two Aral Sea tributaries, Amu Darya and Syr Darya, primarily for booming cotton production (Cai et al ., ; Kirilenko et al ., ). In contrast, the level of the world's largest lake, the Caspian Sea, located in the same region, has risen over 2 m since the late 1970s due to changes in both the climate and land use (Arpe and Leroy, ; Renssen et al ., ); the lake is projected to rise by an additional 0.8‐1.6 m by 2100 (Roshan et al ., ). In North Africa, the area of Lake Chad has decreased by 94% since the 1960s (i.e., from 26,000 to 1,500 km 2 ) due to the changing climate and human activities (Okonkwo, ; Luxereau et al ., ; Sebag et al ., ).…”