Hydrographic survey in the dying Aral Sea

Zavialov, Peter; Kostianoy, Andrey G.; Емельянов, С. В.; Ni, Anatoli; Ishniyazov, Durdibay P.; Khan, Valentina; Kudyshkin, T. V.

doi:10.1029/2003gl017427

Cited by 72 publications

(43 citation statements)

References 6 publications

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“…Zavialov et al (2003) report the same values for the surface water and 96 g kg À1 for the bottom water of the deep trench further south for November 2002. We observed lower Na/K ratios (15) in shallow waters close to the shore and higher ratios (18 -20) in deeper open waters comparable to those in the Small Aral.…”

Section: Large Aralsupporting

confidence: 48%

“…We assume that it is influenced by water from the eastern basin, being flushed in through a small and shallow channel at favorable wind conditions from May to August (Zavialov et al, 2003). The most striking feature in Chernishov Bay is the appearance of a strong pycnocline and the presence of a huge anoxic water body below it.…”

Section: Large Aralmentioning

confidence: 99%

“…Because we consider the western basin of being meromictic, the benthic salt input would accumulate in the bottom layer and not mix with waters above the pycnocline. As Zavialov et al (2003) found the main pycnocline at about 22 m depth in 40 m deep waters, we assume in a very simplified estimate that the bottom water body might fill half the volume of the western basin (38.1 km 3 ). Considering a bottom water inventory of 116 Mio tons sulphate and 154 Mio tons chloride, it would take 0.5 years to refill these inventories by benthic release only.…”

Section: Salt Release From the Sedimentsmentioning

confidence: 99%

“…In November 2002, the sea level in the western basin of the Large Aral approached the 30.5 m a.s.l. (Zavialov et al, 2003). GIS-derived surface of the Large Aral, based on satellite images from summer 2002 and accordingly, bathymetry map, derived volume values are as follows (Stanichny, personal communication): the surface area of the Large Aral has shrunk to 17,350 km 2 and the lake volume decreased to 109 km 3 .…”

Section: Large Aralmentioning

confidence: 99%

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Hydrochemical properties of the Aral Sea water in summer 2002

Friedrich

Oberhänsli

2004

Journal of Marine Systems

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In August 2002, new hydrochemical and hydrophysical data were collected in the Aral Sea. The survey includes crosssections in three locations: within the Small Aral close to Tastubek Bay, in the Large Aral at the northern tip that is Tschebas Bay and within the western basin at Chernishov Bay. All three locations represent different stages in the hydrochemical evolution of the Aral Sea.Depth profiles of pressure, temperature, conductivity, pH and dissolved oxygen were measured with a YSI 6600 profiler. Water samples were taken with a Niskin bottle and analyzed for dissolved oxygen and nutrients by standard photometric methods. Major anions and cations were analyzed by ion chromatography and ICP-OES, respectively. Benthic flux experiments were carried out with sediment cores in a batch mode assay on-site.In the Small Aral, the changes in the hydrochemical properties are not as dramatic as in the Large Aral. The Small Aral represents a brackish inland water body with salinities of 17 -18 g kg À1 . The wind-mixed layer reached 8 m during the survey. The salinity is vertically and horizontally almost uniform. Below 8 m, a temporally hypoxic layer forms during summer. Salt redissolution was found to be an important source of salt in the water. About 33.5 g SO 4 2À m À2 day À1 and about 30.7 g Cl À m À2 day À1 are released from the sediment in summer.In the Large Aral, the salinity distribution is uniform in shallow waters (less than 5 m) but varies strongly in deeper water. Tschebas Bay at the northern tip of the large Aral represents a shallow lagoon with a maximum depth of about 6 m. The water column was well mixed down to the bottom (f6 m) having salt concentrations of 82 g kg À1 on average. Almost no gradients in dissolved substances were observed. It is suspected that salinity is balanced by fresher water inflow originating from the Syr Darya flowing south and by groundwater exfiltration. Chernishov Bay in the north of the western basin is meromictic. Below a windmixed layer, a very strong pycnocline of 20 g kg À1 per m at 5 m depth isolates the water below from exchanges with the water above and led to the formation of huge anoxic water body down to the bottom at about 25 m depth. Below 10 m, the water contains hydrogen sulphide. The salt concentration increases from 82 g kg À1 in the surface water to 110 g kg À1 at depth. The salt release from the sediment is as high as 1143 g SO 4 2À m À2 day À1 and 1626 g Cl À m À2 day À1 . Benthic release of salt is considered as an important source for salt in the bottom water of the western basin and in sustaining the stable density stratification. D

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Section: Large Aralsupporting

confidence: 48%

Section: Large Aralmentioning

confidence: 99%

Section: Salt Release From the Sedimentsmentioning

confidence: 99%

Section: Large Aralmentioning

confidence: 99%

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Hydrochemical properties of the Aral Sea water in summer 2002

Friedrich

Oberhänsli

2004

Journal of Marine Systems

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“…The western lobe, being much deeper (about 40 m), presents a lower salinity, although it is also very high -around 116 g/kg at the surface in June 2008 (Zavialov et al, 2008b). The importance of the exchange flux through the channel connecting the two lobes -sometimes referred to as the Kulandy channel -on the vertical structure of the western lobe was first discussed by Zavialov et al (2003) based on the existence, discovered in 2003, of a bottom layer with a thickness of about 20 m which was warmer and saltier than the bulk water. Measurements made one year later (Zavialov, 2005) showed that water at the bottom of the western lobe was also saltier but colder than the upper bulk water, suggesting a later inflow than in the previous year.…”

Section: E Roget Et Al: Geodynamical Processes Connecting the Two Lmentioning

confidence: 99%

Geodynamical processes in the channel connecting the two lobes of the Large Aral Sea

Roget

Zavialov

Khan

et al. 2009

Hydrol. Earth Syst. Sci.

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Abstract.Reasons for the existence of the channel connecting the two lobes of the present Large Aral Sea are discussed. In situ measurements in 2005 show that differences between the measured depths and those contained in the available digital bathymetry of the lake are considerably different at the channel (7.5±0.9 m, at nine measurement stations along it) and at the northern part of the eastern lobe (1.6±0.3 m, at six stations from the western to the eastern shore). Differences in the misfits observed in the two zones are discussed and thought to be a consequence of the variation of the transversal area of the channel as it enters the eastern lobe, which would affect the flow velocity and thus the strength of the erosion process at the bottom. Field data together with satellite images have been used to modify an original digital bathymetry of the lake and have been implemented into a 3-D hydrodynamical model. A numerical simulation shows that a wind of 12 m/s blowing from the east (112 • ) generates velocities of up to 45 cm/s in the channel, allowing denser water from the eastern lobe (salinity: 132 g/kg) to flow about 38 km towards the fresher western lobe (salinity: 98 g/kg) in one day. The effect of the inflow on the vertical structure of the western lobe is also illustrated. Although nowadays the channel will be soon a thing of the past, in a more general context, the Aral Sea is presented as an example showing that geomorphologic and geophysical processes, along with hydrological and atmospheric processes, must be taken into account for short-term predictions.

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Archaeology and climate: Settlement and lake‐level changes at the Aral Sea

et al. 2006

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New archaeological and geomorphologic data collected adjacent to the Aral Sea show lake-level stands during the late Pleistocene and the past 5000 years. On the northern and southern shores, archaeological sites from the Palaeolithic through the Late Middle Ages contain evidence of various cultures and economies. Changes in settlement activity during the mid-Holocene are related to several major lake-level oscillations. Some of them, especially those which occurred at approximately 350-450 cal B.P. (during the Little Ice Age), 700-780 cal B.P., around 1400 cal B.P., and 1600-2000 cal B.P., were accompanied by lithological changes in sediment cores retrieved from the Aral Sea and were observed in shoreline shifts. We show that a maximum lake level at 72-73 m above sea level cannot be corroborated. The highest lake level, which was reached at the beginning of the 20th century, probably never exceeded 54-55 m a.s.l. Furthermore, we documented a previously unknown low-level stand at 42-43 m a.s.l. that dated to the Bronze Age (~4000-3000 B.P.). The regression during 1200-1300 cal A.D. was formerly underestimated and was lower than the present-day lake level. The observed environmental changes, except those since the 1960s, are most probably driven by climate variability, though human activities (e.g., irrigation) can amplify the impact.

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Hydrographic survey in the dying Aral Sea

Cited by 72 publications

References 6 publications

Hydrochemical properties of the Aral Sea water in summer 2002

Hydrochemical properties of the Aral Sea water in summer 2002

Geodynamical processes in the channel connecting the two lobes of the Large Aral Sea

Archaeology and climate: Settlement and lake‐level changes at the Aral Sea

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