Estimating the Anthropogenic Impact on Water Bodies Using a Simulation Mathematical Model of Phosphorus System

A simulation model of the phosphorus system is used to study the ecosystems functioning in the Dautkul'skoe Reservoir and Shegekul Lake (Mezhdurech'e). Dependence of the internal flows (turnover) and normal annual concentrations of P forms in the water body on its external load onto the ecosystem is established. The budgets of P and its production–destruction flows (1993–1999), calculated using the model, are presented and analyzed. Comparison estimates are made for the anthropogenic impact on the water bodies of the southern Aral Sea region.     

1990-2019年咸海水量平衡及其影响因素分析

咸海地处中亚,气候和人类的双重影响下湖面急剧萎缩引发区域生态危机,定量解析其水量平衡互动关系及影响因素对咸海地区水资源管理和生态保护有重要意义.基于1990-2019年密集时序Landsat影像、T/P卫星、Jason1/2测高卫星及咸海数字测深模型(DBM),提取近30年咸海面积、水位变化信息,重建咸海水位-面积-库...     

Variations in the Hydrological Regime of Kara-Bogaz-Gol Gulf,Lake Issyk-Kul,and the Aral Sea Assessed Based on Data of Bottom Sediment Studies

The isotopic and material composition of bottom deposits, examined in the Kara-Bogaz-Gol Gulf, Lake Issyk-Kul, and the Aral Sea, is considered. The obtained data are used to characterize variations in the regime of the water bodies in the Holocene.     

Space monitoring of Aral Sea degradation

The results of remote sensing survey of the Aral Sea in its degradation period are given. Satellite images are used to map shoreline retreat from 1961 to 2008 and to measure the decrease in the area. Seasonal variations in shoreline and water area are identified, suggesting seasonal level variations and correlating well with data of satellite altimetry surveys of sea level. Observations covered surge phenomena, seasonal dynamics of landscapes, and the seasonal salinization rhythm in coastal territories with the subsequent formation and weathering of salt crusts. The character of river runoff input into the Great Sea resulting from overbank flooding in artificial water bodies in the Amu Darya delta is identified.     

Modélisation du bilan hydrologique de la partie sud de la Mer d'Aral entre 1993 et 2001 / Hydrological balance modelling of the southern Aral Sea between 1993 and 2001

Abstract

Since the beginning of the 1990s, the Aral Sea is made of two separate entities: the Small Aral in the north and the Great Aral in the south. In this study, the water and salt balance of the Great Aral is analysed using newly available data: on the one hand, altimetric data of the sea level provided by the TOPEX/Poseidon satellite; and on the other, climate data provided by the ECMWF and NOAA within the framework of global climate re-analysis. These data indicate that the Great Aral received a mean groundwater inflow of about 4 km³ year^-1 between 1993 and 2001. Without this contribution, the Aral Sea would disappear even faster than is being observed today. Moreover, the temporal resolution of the data shows a systematic phase difference between the model prediction and satellite measurements. This phase shift is considered to be due to the formation of temporary lakes between the last station measuring the Amu-Darya discharge and its mouth in the Great Aral.     

Paleomagnetic correlation of sedimentary sequences: The use of secular geomagnetic variations for the differentiation and correlation of Holocene Aral Sea deposits

The paper presents results demonstrating the possibility of using data on paleosecular magnetic variations for correlation of young deposits. Using Holocene deposits of the Aral Sea as an example, it is shown that the combination of paleo-and petromagnetic data can be used to reliably correlate sections in presently isolated parts of a basin, as well as to correlate paleohydrologic events and estimate their age with regard for absolute radiocarbon datings. It is established that the most significant drop in the Aral Sea level occurred more than 2000–2500 yr ago and less significant drops that occurred later are dated at about 1500, 750–1050, and 270–500 yr ago.     

Irrigation Effects on Hydro-Climatic Change: Basin-Wise Water Balance-Constrained Quantification and Cross-Regional Comparison

Hydro-climatic changes driven by human land and water use, including water use for irrigation, may be difficult to distinguish from the effects of global, natural and anthropogenic climate change. This paper quantifies and compares the hydro-climatic change effects of irrigation using a data-driven, basin-wise quantification approach in two different irrigated world regions: the Aral Sea drainage basin in Central Asia and the Indian Mahanadi River Basin draining into the Bay of Bengal. Results show that irrigation-driven changes in evapotranspiration and latent heat fluxes and associated temperature changes at the land surface may be greater in regions with small relative irrigation impacts on water availability in the landscape (here represented by the Mahanadi River Basin) than in regions with severe such impacts (here represented by the Aral region). Different perspectives on the continental part of Earth’s hydrological cycle may thus imply different importance assessments of various drivers and impacts of hydro-climatic change. Regardless of perspective, however, actual basin-wise water balance constraints should be accounted to realistically understand and accurately quantify continental water change.     

Hydrochemical Characteristics of the Aral Sea in 2012–2013

The decrease in Aral Sea area, which started in the 1960s, caused considerable changes in the hydrological, chemical, and biological structure of sea water. Regular observations of Aral water chemistry ceased in the early 1990s. There were no observations of the concentrations of biogenic element compounds in water (the so-called “first-day analyses”). During expeditions of the Institute of Oceanology, RAS, in September 2012 and October 2013, integrated hydrochemical observations were carried out, including measuring the concentrations of biogenic element compounds, dissolved oxygen, hydrogen sulfide, and carbonate equilibrium components. An objective of this study was to develop methods of hydrochemical studies under high water salinity (mineralization). In addition to the standard hydrochemical complex, water samples were taken to determine total water mineralization and the concentration of dissolved and suspended metal forms. The results of these studies are given.     

Mesoscale activity in the North Sea as seen in ensemble simulations

A set of two simulation ensembles of the ocean circulation in the North Sea, the Skagerrak and bordering seas has been run for the ten year period that started in January 1992. The ensembles differed only in the horizontal grid resolution. The main purposes of this investigation are (1) to quantify the variability that can be expected in multi-year simulations due to noise-like perturbations in the initial fields, and (2) to examine the robustness of model results for mesoscale features that form on the front between the Norwegian Coastal Current and water masses that are of an Atlantic Ocean origin. It is shown that the model resolution has a substantial impact on the ensemble variability, and that the role of small perturbations become more significant as the grid mesh is refined. Nevertheless, it is demonstrated that in a region to the west of the southern tip of Norway, eddies are occasionally found in the same positions at the same time in the results from all members of the ensembles. This is particularly the case in the aftermath of outbreak events of low salinity water masses from the Skagerrak into the North Sea.     

The exceptional Oder flood in summer 1997 — distribution patterns of the oder discharge in the Pomeranian Bight

The exceptional Oder flood in summer 1997 was a unique event in order to investigate the impacts on and the consequences for the ecosystem of the Baltic Sea of about 6.5 km³ additional water loaded with nutrients and contaminants and discharged within only 5 weeks. About 15 institutions participated in this investigation in both the Szczecin Lagoon and the Pomeranian Bight. The Baltic Sea Research Institute Warnemünde studied the water and nutrient inflow, the spreading of the Oder discharge, and the impact of the discharge on the ecosystem. The main topic of the presented investigations is a detailed study of the spatial and temporal spreading of the extreme river discharge in the Pomeranian Bight and the southern Baltic Sea by satellite data, ship observations and continuous buoy measurements as well as numerical modelling. The meteorological conditions were characterized by mainly easterly winds which guided the outflowing riverine water along the German coast into the Arkona Sea. The spatial and temporal development of the distribution patterns of the Oder discharge was monitored by about 80 Sea Surface Temperature (SST) images of NOAA satellites. Shipborne measurements showed that the vertical extent of the Oder plume ranged between 5 and 7 metres. The concentrations of inorganic nutrients, except higher silicate, were comparable to typical winter/early spring values (seasonal maximum) in this region. The high dilution effect of the flood water reduced the concentration of contaminants and thus, prevented a direct negative impact of trace metals and chlorinated organic compounds on the marine environment. Coupled physical-biochemical modelling in combination with SST-images demonstrated the temporal development and satellite data in the visible spectral range delivered the maximum extent of discharged river water into the southern Arkona Sea where a further western transport was limited by the upwelling region off Hiddensee. Thus, all detected effects of the Oder flood were confined to the Pomeranian Bight and the southern Arkona Sea, without long-term consequences for the ecosystem.     

Mechanisms controlling the intra-annual mesoscale variability of SST and SPM in the southern North Sea

Thermal and optical remote sensing data were used to investigate the spatial and temporal distribution of sea surface temperature (SST) and of suspended particulate matter (SPM) in the southern North Sea. Monthly SST composites showed pronounced seasonal warming of the southern North Sea and delineated the English coastal and continental coastal waters. The East-Anglia Plume is the dominant feature of the English coastal waters in the winter and autumn SPM composites, and the Rhine region of freshwater influence (ROFI), including the Flemish Banks, is the dominant feature of the continental waters. These mesoscale spatial structures are also influenced by the evolution of fronts, such as the seasonal front separating well-mixed water in the southern Bight, from the seasonally stratified central North Sea waters. A harmonic analysis of the SST and SPM images showed pronounced seasonal variability, as well as spring-neap variations in the level of tidal mixing in the East Anglia Plume, the Rhine ROFI and central North Sea. The harmonic analysis indicates the important role played by the local meteorology and tides in governing the SST and near-surface SPM concentrations in the southern North Sea. In the summer, thermal stratification affects the visibility of SPM to satellite sensors in the waters to the north of the Flamborough and Frisian Fronts. Haline stratification plays an important role in the visibility of SPM in the Rhine ROFI throughout the year. When stratified, both regions typically exhibit low surface SPM values. A numerical model study, together with the harmonic analysis, highlights the importance of tides and waves in controlling the stratification in the southern North Sea and hence the visibility of SPM.     

Observation of the seasonal evolution of the Yellow Sea Cold Water Mass in 1996–1998

We use the hydrographic data obtained during the joint survey of the Yellow Sea by the First Institute of Oceanography, China and the Korea Ocean Research and Development Institute, Korea, to quantify the spatial structures and temporal evolution of the southern Yellow Sea Cold Water Mass (YSCWM). It is indicated that the southern YSCWM is a water mass that develops in summer and decays in fall. In winter, due to the intrusion of the Yellow Sea Warm Current (YSWC), the central area (approximately between 34°N and 35°N, 122°E and 124°E) of the Yellow Sea is mainly occupied by relatively high temperature water (T>10 °C). By contrast, from early summer to fall, under the seasonal thermocline, the central area of Yellow Sea is occupied by cold water (T<10 °C). In summer, the southern YSCWM has two cold cores. One is formed locally southeast of Shandong Peninsula, and the other one has a tongue-like feature occupying the area approximately between 34°N and 37°N, 123°E and 126°E. The bottom layer temperature anomalies from February to July in the cold tongue region, along with the trajectories of the bottom floaters, suggest that the cold water mass in the northeast region has a displacement from the north to the central area of the Yellow Sea during the summer.     

Changes in the hydrochemical composition and diatomic flora of bottom sediments in the zone of influence of metal mining production (Kola Peninsula)

Paleoecological studies of small water bodies were carried out in a model subarctic lake-river system. The degree of transformations of aquatic ecosystems under a set of anthropogenic factors is shown to vary depending on the load and individual features of water bodies. Data on the state of aquatic ecosystems before the industrial development of the region are collected. The species composition of diatom algae and their ecological characteristics are examined.     

A Scenario of Possible Effect of Changes in the Hydrological Conditions on the Medical and Environmental Situation: On the Problem of Global Hydroclimatic Changes

The effect of transformation of the human habitat on the medical and ecological situation is considered in the context of anticipated changes in the hydrological situation. The results of earlier studies of environmental crises (transgression of the Caspian Sea and degression of the Aral Sea) are used to show the possibility of a considerable increase in the rates of infectious and noninfectious diseases caused by a direct or indirect effect of significant changes in the hydrological and hydrogeological conditions. Regularities in the dynamics of this process have been established, which allows us to discuss possible changes in public health under new hydroclimatic conditions, in particular, under global climate changes. It is shown that the scientific principles and methods for prediction of the consequences of changes in the regime, quantity, and quality of continental waters should be improved in order to allow the assessment of their effect on public health and the development of timely preventive measures.     

The late Holocene mollusc fauna of the Aral Sea and its biogeographical and ecological interpretation

The Aral Sea, in 1960 the fourth largest lake on Earth, has since experienced a catastrophic environmental change, which appears to be mainly a result of human impact. Here, we attempt to add to a better understanding of environmental changes during the last millennium by using fossil mollusc assemblages obtained from 10 sediment cores, which were taken by gravity coring in 1991. The biogeographical analysis demonstrates that no endemic molluscs have existed in the Aral Sea during the last 1000 years. The investigated taxa are of Caspian and Palaearctic origin. The molluscan biodiversity is much lower than previously assumed and particularly low for such a large lake, indicating unstable ecological conditions during the period investigated. Using comparative ecological analyses of thanatocoenoses and stable isotope ratios in gastropod shells, we conclude that the main lake level changes of the last millennium were strong and abrupt, showing relative high stands at about 1300 AD and 1650 AD.     

New evidence of delamination in the Western Alboran Sea: Geodynamic evolution of the Alboran domain and its margins

The presence of continuous upper crustal blocks between the Iberian Betics and Moroccan Rif in the western and middle Alboran Sea, detected with tomography, can add new information about the lithosphere structure and geodynamic evolution in this region. A large volume of seismic data (P and S wave arrival times) has been collected for the period between 1 December 1988 and 31 December 2008 by 57 stations located in northern Morocco (National Institute of Geophysics, CNRST, Rabat), southern Portugal (Instituto de Meteorologia, Lisbon) and Spain (Instituto Geografico National, Madrid) and used to investigate the lithosphere in the western Alboran Sea region. We use a linearized inversion procedure comprising two steps: (1) finding the minimal 1-D model and simultaneous relocation of hypocenters and (2) determination of local velocity structure using linearized inversion. The model parameterization in this method assumes a continuous velocity field. The resolution tests indicate that the calculated images give near true structure imaged at 5 km depth for the Tanger peninsula, the Alhoceima region and southern Spain. At 15, 30 and 45 km depth we observe a near true structure imaged in northern Morocco, and southern Spain. At 60 and 100 km, southern Spain and the SW region of the Alboran Sea give a near true structure. The resulting tomographic image shows the presence of two upper crustal bodies (velocity 6.5 km/s) at 5–10 km depth between the Betics, Rif, western and central Alboran Sea. Low velocities at the base of these two bodies favor the presence of melt. This new evidence proves that the Tethysian ocean upper crust was not totally collapsed or broken down during the late Oligocene–early Miocene. These two blocks of upper crust were initially one block. The geodynamic process in the eastern of the Mediterranean is driven by slab rollback. The delamination process of the lithospheric mantle terminates with the proposed slab rollback in the western part of the Mediterranean. This can be explained by the removal of the major part of the lithosphere beneath the area, except in the SW part of the Alboran Sea where a small part of the lithospheric mantle is still attached and is extends and dips to SE beneath the Rif, slowly peeled back to the west. A second detached lithospheric mantle is located and extends to eastern part of the Rif and dips to the SE. The removal of lithosphere mantle from the base of the crust was replaced and heated by extrusion of asthenospheric material coming from depth to replace the part of crust detached. A combination of isostatic surface/topographic uplift and erosion induced a rapid exhumation and cooling of deep crustal rocks.     

南海大陆边缘动力学:科学实验与研究进展

国家重点基础研究发展计划(973)项目(2007CB411700)首次在南海南部大陆边缘及西南次海盆开展长排列大震源多道地震、海底地震仪(OBS)折射/反射地震等的综合地球物理探测,结合地质构造、地球化学、动力模拟等的综合研究,形成如下重要认识:南海海盆新生代发生了早、晚两期海底扩张.早期扩张发生于33.5～25 Ma...     

River flow regime and snow cover of the Pamir Alay (Central Asia) in a changing climate

Abstract

The Vakhsh and Pyandj rivers, main tributaries of the Amu Darya River in the mountainous region of the Pamir Alay, play an important role in the water resources of the Aral Sea basin (Central Asia). In this region, the glaciers and snow cover significantly influence the water cycle and flow regime, which could be strongly modified by climate change. The present study, part of a project funded by the European Commission, analyses the hydrological situation in six benchmark basins covering areas of between 1800 and 8400 km², essentially located in Tajikistan, with a variety of topographical situations, precipitation amounts and glacierized areas. Four types of parameter are discussed: temperature, glaciation, snow cover and river flows. The study is based mainly on a long-time series that ended in the 1990s (with the collapse of the Soviet Union) and on field observations and data collection. In addition, a short, more recent period (May 2000 to May 2002) was examined to better understand the role of snow cover, using scarce monitored data and satellite information. The results confirm the overall homogeneous trend of temperature increase in the mountain range and its impacts on the surface water regime. Concerning the snow cover, significant differences are noted in the location, elevation, orientation and morphology of snow cover in the respective basins. The changes in the river flow regime are regulated by the combination of the snow cover dynamics and the increasing trend of the air temperature.

Editor Z.W. Kundzewicz