Caspian Sea level changes during the last millennium: historical and geological evidences from the south Caspian Sea

Abstract

Historical literature may constitute a valuable source of information to reconstruct sea level changes. Here, historical documents and geological records have been combined to reconstruct Caspian sea-level (CSL) changes during the last millennium. In addition to a literature survey, new data from two short sediment cores were obtained from the south-eastern Caspian coast to identify coastal change driven by water-level changes. Two articulated bivalve shells from the marine facies were radiocarbon dated and calibrated to establish a chronology and to compare them with historical findings. The overall results indicate a high-stand during the Little Ice Age, up to −19 m, with a −28 m low-stand during the Medieval Climate Anomaly, while presently the CSL stands at −26.5 m. A comparison of the CSL curve with other lake systems and proxy records suggests that the main sea-level oscillations are essentially paced by solar irradiance. Although the major controller of the long-term CSL changes is driven by climatological factors, the seismicity of the basin could create locally changes in base level. These local base-level changes should be considered in any CSL reconstruction

Reconstructions of deltaic environments from Holocene palynological records in the Volga delta, northern Caspian Sea

“…Salinity of the surface waters is lowest ( c. 3‰ or less) close to the Volga outflow, increasing to around 13.5‰ in the central and southern basins (Kosarev and Yablonskaya, 1994). The surface of the Caspian Sea is currently about 26.5 m below global sea level (Arpe et al, 2012; Naderi Beni et al, 2013a) and not connected directly to the world’s oceans at the present time, although connections are known to have occurred in the recent geological past. A marine connection existed at the end of the Pliocene to beginning of the Pleistocene (Akchagylian stage) between c. 3.2 and 2 million years ago (Kosarev and Yablonskaya, 1994; Van Baak et al, 2013), and connections were re-established at various times throughout the Pleistocene (Badertscher et al, 2011; Forte and Cowgill, 2013; Rychagov, 1977; Tudryn et al, 2012).…”

“…Subsequently, it is generally agreed that Caspian Sea levels were variable, but mostly high, in the early to mid-Holocene with maximum levels of around −24 to −20 m below present-day global sea level ( c. 3–7 m above present-day levels) between c. 9000 and c. 5000 years ago (Chepalyga, 2007; Rychagov, 1997). Further highstands then occurred, with Caspian Sea levels reaching −25 to −19 m below present-day global sea level (Naderi Beni et al, 2013a, 2013b) within the last few hundred years, following a late Holocene lowstand event known regionally as the Derbent. Overeem et al (2003) showed how the very recent sediments and vegetation in the Damchik region have evolved over a period of (mainly) sea level fall since 1935, based on aerial photographs and vegetation maps.…”

“…Between 1935 and 1977, Caspian Sea levels fell by c. 3 m, from c. −26 to c. −29 m (Kosarev and Yablonskaya, 1994) leading to an outbuilding of the delta by about 10 km (Alekseevskiy et al, 2010). Deposition was then fairly stable during a period of Caspian Sea level rise of around 2.7 m between 1978 and 1995; a minor fall has since been recorded and present-day levels fluctuate at around −26.5 m (Arpe et al, 2012; Naderi Beni et al, 2013a).…”

“…For example, storm surges of 2–3 m above normal occurred in 1952 and caused flooding as far north as the city of Astrakhan (Kroonenberg et al, 1997). True tides are absent in the Caspian Sea (Naderi Beni et al, 2013a), although ‘seiches’ do occur (Kosarev and Yablonskaya, 1994) resulting in minor ‘tidal’ ranges of 10 cm or less in the coastal regions (Spidchenko, 1973).…”

An early ‘Little Ice Age’ brackish water invasion along the south coast of the Caspian Sea (sediment of Langarud wetland) and its wider impacts on environment and people

“…These dramatic sea level changes have affected the surrounding populations and their activities. The Italian traveller Marin Sanudo already documented that the early 14th-century water-level rise destroyed many important cities around the CS (see Naderi Beni et al, 2013a). The recent and rapid CSL changes have directly affected tens of thousands of people in the lowlands of Iran, Azerbaijan, Dagestan and the Volga Delta (Rucevska et al, 2006).…”