Phosphorus distribution in the sediments of a shallow eutrophic lake,Lake Chaohu,China

In this study, the sediment profiles of total phosphorus (TP), inorganic phosphorus (P_i), organic phosphorus (P_o), C/P and N/P were used to investigate time-dependent P distribution changes in Lake Chaohu. The characteristics of P_i and P_o fractions in the surface sediments were studied and the difference between east and west lake region was also discussed. The P_i and P_o contents displayed a clear gradient from east to west in sediments of Lake Chaohu, and the P_o/P ratios were lower in sediments with industrial and urban pollution sources input in west lake region. The study indicated that different sediments area had diverse concentrations and distributions of P_o fractions due to their different drainage basin and pollution sources. The profile distribution of the C/P and N/P ratios decreased with increasing depths and stayed relatively constant ratios at the depths of 15–30 cm. The C/P and N/P ratios were always below Redfield ratios in sediment profile, indicating P enrichment but likely due to the preferential loss of carbon in respect to phosphorus. The rank order of P_i-fractions extracted was HCl-P_i > NaOH-P_i > NaHCO₃-P_i in surface sediments. The relative distribution of NaHCO₃-P_i and HCl-P_i was in agreement with the trophic conditions of the regions studied. Among the sequentially extracted P_o forms, the rank order of P_o fractions was residual P_o > HCl-P_o > fulvic acid-P > humic acid-P > NaHCO₃-P_o, with mean relative proportion of 5.4:3.4:2.2:1.1:1.0.     

The limnology and paleolimnology of a shallow eutrophic lake in Eastern China

Xuanwu Lake (3.7 km²) is a shallow (mean depth 1.4 m) hypereutrophic lake (annual productivity greater than 600 g cm^–2) located in East China's flood plain near the N end of Nanjing, China's ninth largest city. Paleolimnological data based on a 16 cm long sediment core removed from near the center of the lake indicated that nutrient pollution tolerant diatoms have replaced pollution intolerant taxa which were common near the base of the core (approximately 35 years before present). These paleolimnological observations support the hypothesis that progressive eutrophication is occurring in Xuanwu Lake. This conclusion is corroborated by direct comparisons of the present day phytoplankton and zooplankton species composition within the lake and published accounts of its species composition during the mid 1970's.During the last decade, zooplankton density has increased 153% and zooplankton species' richness has declined by 33%. Phytoplankton biomass has increased over 10-fold and the lake's photic zone has decreased to its current (1987) condition (1% surface light intensity at 0.7 m).Xuanwu Lake, like many similar shallow polymictic lakes in E China, has not been depleted of dissolved oxygen near its bottom. This is due to frequent wind mixing, of the entire lake. Thus its progressive hypereutrophication does not result in the same suite of problems experienced by lakes whose hypolimnion is stagnant for long periods of time.     

A Lateglacial and Holocene lake record from the Nianbaoyeze Mountains and inferences of lake, glacier and climate evolution on the eastern Tibetan Plateau

Our 12.81 m long record from Lake Ximencuo provides insight into the Lateglacial and Holocene evolution of the lake and the Nianbaoyeze glacier in its catchment, and the regional climate history since 19 kyr. Lake Ximencuo was a permanent deep lake throughout its history. In contrast to numerous lakes on the Tibetan Plateau which experienced shallow lake levels or even desiccation during the Lateglacial, Lake Ximencuo was fed by large quantities of meltwater in the Lateglacial. The existence of glaciated upper catchment areas is apparently a prerequisite for lakes on the Tibetan Plateau which maintained relatively high water levels during the generally cold and dry periods following the global LGM (21 kyr). A minor re-advance of the Nianbaoyeze glacier was recorded coeval with the Greenland Stadial 2a (16.4 and 14.5 kyr), followed by rapid warming apparently synchronous with the Greenland Interstadial 1. Warmest conditions were recorded at Lake Ximencuo during the early Holocene which was punctured by a remarkable pulse of climate deterioration around 8.3 kyr. This spell represents probably the 8.2 kyr event of the North Atlantic region, suggesting that it had a significant impact on the Tibetan Plateau. Colder conditions of longer duration occurred from 4.7 to 3.7 kyr, apparently in phase with numerous records signalling colder and drier conditions on the Tibetan Plateau. Two minor spells of colder conditions and probably catchment erosion were recorded in the late Holocene between 2.0 and 1.4 kyr and between 0.5 and 0.1 kyr with the latter representing the Little Ice Age. It is unclear, whether human activities may have accelerated or even solely triggered the late Holocene erosion events.     

Spatial-seasonal dynamics of chromophoric dissolved organic matter in Lake Taihu, a large eutrophic, shallow lake in China

From 2005 to 2009, the spatial distribution and the seasonal dynamics of chromophoric dissolved organic matter (CDOM) were explored in Lake Taihu in eastern China. The spatial-seasonal dynamics of CDOM absorption and three CDOM composition variables, including spectral slope (S), spectral slope ratio (S_R) and the M value, defined as the ratio of absorption at 250 nm/365 nm, were analyzed and discussed. Furthermore, river input processes and degradation of phytoplankton were studied to assess their impact on CDOM composition and the factors involved in the spatial-seasonal variability of CDOM. The CDOM absorption coefficient at a wavelength of 350 nm, a(350), ranged from 1.37-9.55 m⁻¹ with a mean of 3.33 ± 1.32 m⁻¹. Spatially, higher a(350) values, but lower spectral slope, spectral slope ratio and M values, were recorded in the northern algae dominated bays while lower values were recorded in southeastern macrophyte dominated bays. The a(350) was significantly higher in inshore waters than in offshore waters. Values of S, S_R and M decreased during the flood and algal bloom season in spring and summer whereas a(350) increased. In the three river profiles, the gradual decrease of a(350) along the trajectory from the river mouth into the lake during the flood season showed the contribution of allochthonous CDOM. A laboratory phytoplankton degradation experiment was conducted to determine the contribution of CDOM production from phytoplankton. The significant increase of a(350) with time in the CDOM production experiment underlines the importance of autochthonous CDOM production during the algal bloom season. In summary, the significant increase of a(350) in spring and summer (algal bloom season) may be due to both the allochthonous CDOM input from the surrounding rivers and the autochthonous production of CDOM from degrading phytoplankton.     

Holocene climate variability from lake sediment core in Larsemann Hills,Antarctica

A sediment core (L2) from Larsemann Hills, Antarctica was analyzed for Biogenic Silica (BSi), Sand (%) and Total Organic Carbon (TOC). The 78 cm core length represents the time span of ∼8.3 cal ka BP. The values of BSi from the core show prominent high productivity from ∼8.3 to ∼6 cal ka BP in comparison to less productivity in mid-late Holocene (∼6 cal ka BP to recent). Moreover, high sand (%) infers the glacio-fluvial deposition from ∼8.3 to ∼5 cal ka BP TOC shows little variation through out the core, except in the upper ∼10 cm (∼4 cal ka BP) part wherein it is comparatively high. The increased TOC in the upper part of the core possibly indicates presence of algal mat due to exposure of the lake to the ice free (glacier free) conditions.     

Multi-proxy climate and environmental records from a Holocene eutrophic mire,southern taiga subzone,West Siberia

Palaeoenvironmental reconstructions from peat are strongly focused on ombrotrophic mires, but this study demonstrates that eutrophic mires can also be used. A multi-proxy approach was applied to a eutrophic mire on a floodplain terrace in the southern taiga of West Siberia. The results of the reconstruction were considered in the wide geographic context of the surrounding regions, including Siberia and Central Asia. Different palaeoecological proxies (analysis of plant macrofossils, testate amoebae, oribatid mites, molluscs, peat humification, ash content and spectral characteristics of humic acids) were used in this study. The results of different proxies showed a high level of consistency among themselves, which allowed for a robust interpretation of Holocene mire development. Throughout the ~7800 years history of the mire, there was a high level of surface wetness. The presence of mineral matter in the peat between 7800 and 5100 cal. a BP indicates regular flooding caused by the intensive fluvial activity, apparently resulting from increased precipitation. This was followed by a trend towards a gradual decrease in surface wetness from conditions of high surface moisture (stagnant water) between 5100 and 3000 cal. a BP to present day conditions of moderate surface moisture with a water table slightly below the mire surface. This pattern is consistent with the well-documented long-term trend from palaeoecological records throughout the taiga and arctic zones in West Siberia and central arid Asia. Our data further support the idea that the westerlies were the dominant driver of climate for the southern taiga of West Siberia during the Middle to Late Holocene.     

Effects of climate change on shallow landslides in a small coastal catchment in southern Italy

In different areas of the world, shallow landslides represent a remarkable hazard inducing fatalities and economic damages. Then, the evaluation about potential variation in frequency of such hazard under the effect of climate changes should be a priority for defining reliable adaptation measurements. Unfortunately, current performances of climate models on sub-daily scales, relevant for heavy rainfall events triggering shallow landslides, are not reliable enough to be used directly for performing slope stability analysis. In an attempt to overcome the constrains by gap in time resolution between climate and hazard models, the paper presents an integrated suitable approach for estimating future variations in shallow landslide hazard and managing the uncertainties associated with climate and sub-daily downscaling models. The approach is tested on a small basin on Amalfi coast (southern Italy). Basing on available basin scale critical rainfall thresholds, the paper outlines how the projected changes in precipitation patterns could affect local slope stability magnitude scenarios with different relevances as effect of investigated time horizon and concentration scenario. The paper concludes with qualitative evaluations on the future effectiveness of the local operative warning system in a climate change framework.     

A 2000-year record of solar forcing on varved lake sediment in eastern Finland

A high-resolution study was performed on varved sediments from Lake Lehmilampi in eastern Finland. Varve data was collected by digital image analysis using standard 1.8 mm thick samples impregnated in epoxy and X-rayed. Climatic variability is imprinted on varve properties (varve thickness and accumulation of mineral and organic matter) during the last 2000 years. The cumulative counting error of the varve record is estimated as 2.3%. Qualitative comparison of varve parameters and residual Δ¹⁴C constructed from tree-rings revealed close correspondence between the two records, suggesting solar forcing on lake sedimentation. Classical climatic periods of the last millennia, Medieval Climate Anomaly (1060–1280 in the varve record) and Little Ice Age (cooler phases culminating in 1340, 1465, 1545, 1680, 1850 and also in 1930 in the varve record) are clearly evident in the varve record. At present the physical link between solar activity levels and lake sedimentation has not been established.     

Abrupt Holocene climate change and potential response to solar forcing in western Canada

Several abrupt climate events during the Holocene, including the widely documented oscillation at 8.2 thousand years before present (ka), are attributed to changes in the North Atlantic thermohaline circulation. Additional mechanisms, such as interactions between atmospheric circulation, ice-sheet dynamics, and the influence of solar irradiance, also have been proposed to explain abrupt climatic events, but evidence remains elusive. This study presents evidence from multi-proxy analyses on the Holocene sediments of Eleanor Lake, interior British Columbia. Climatic inferences from our decadal-resolution record of biogenic silica (BSi) abundance are supported by changes in diatom and pollen assemblages from the same core and correlations with existing regional climate records. The BSi record reveals abrupt and persistent climatic shifts at 10.2, 9.3, and 8.5 ka, the latter two of which are coeval with major collapses of the Laurentide Ice Sheet. The record also reveals a short-term cooling at 8.2 ka that is distinct from the 8.5 ka event and similar in magnitude to several other late-Holocene coolings. BSi is correlated with solar-irradiance indices (r = 0.43–0.61), but the correlation is opposite in sign to that expected from direct solar forcing and weakens after 8 ka. Possible mechanisms causing the abrupt and persistent climate changes of the early Holocene include 1) sudden losses of ice and proglacial lake extent, causing a shift in the meridional structure of atmospheric circulation, 2) a possible link between solar minima and El Niño-like conditions that are correlated with warm spring temperature in interior British Columbia, and 3) the influence of solar irradiance variability on the position of the polar jet, possibly via effects on the strength of the glacial anticyclone.     

Holocene climate changes in southern Greenland: evidence from lake sediments

A Holocene lake sediment record is presented from Lake N14 situated on Angissoq Island 15 km off the main coast of southern Greenland. The palaeoclimatic development has been interpreted on the basis of flux and percentage content of biogenic silica, clastic material, organic material and sulphur as well as sedimentation rate, moss content and magnetic susceptibility. A total of 43 radiocarbon dates has ensured a reliable chronology. It is argued that varying sediment composition mainly reflects changing precipitation. By analogy with the present meteorological conditions in southern Greenland, Holocene climate development is inferred. Between 11 550 and 9300 cal. yr BP temperature and precipitation increase markedly, but this period is climatically unstable. From 9300 yr BP conditions become more stable and a Holocene climatic optimum, characterised by warm and humid conditions, is observed from 8000 to 5000 cal. yr BP. From 4700 cal. yr BP the first signs of a climatic deterioration are observed, and from 3700 cal. yr BP the climate has become more dry and cold. Superimposed on the climatic long‐term trend is climate variability on a centennial time‐scale that increases in amplitude after 3700 cal. yr BP. A climatic scenario related to the strength and position of the Greenland high‐pressure cell and the Iceland low‐pressure cell is proposed to explain the Holocene centennial climate variability. A comparison of the Lake N14 record with a terrestrial as well as a marine record from the eastern North Atlantic Ocean suggests that the centennial climate variability was uniform over large areas at certain times. Copyright © 2004 John Wiley & Sons, Ltd.     

Composition and origin of organic matter in surface sediments of Lake Sarbsko: A highly eutrophic and shallow coastal lake (northern Poland)

We present an organic geochemical study of surface sediments of Lake Sarbsko, a shallow coastal lake on the middle Polish Baltic coast. The aim was to provide evidence concerning the origin of the organic matter (OM) and its compositional diversity in surface deposits of this very productive, highly dynamic water body. The content and composition of the OM in the bottom sediments were investigated at 11 sampling stations throughout the lake basin. OM sources were assigned on the basis of bulk indicators [total organic carbon (TOC), total nitrogen (TN), δ¹³C_TOC and δ¹⁵N and extractable OM yield], biomarker composition of extractable OM and compound-specific C isotope signatures. The source characterization of autochthonous compounds was verified via phytoplankton analysis. The distribution of gaseous hydrocarbons in the sediments, as well as temporal changes in lake water pH, the concentration of DIC (dissolved inorganic carbon) and δ¹³C_DIC were used to trace OM decomposition.The sedimentary OM is composed mainly of well preserved phytoplankton compounds and shows minor spatial variability in composition. However, the presence of CH₄ and CO₂ in the bottom deposits provides evidence for microbial degradation of sedimentary OM. The transformation of organic compounds in surface, bottom and pore waters via oxidative processes influences carbonate equilibrium in the lake and seasonally favours precipitation or dissolution of CaCO₃.The data enhance our understanding of the relationships between the composition of sedimentary OM and environmental conditions within coastal ecosystems and shed light on the reliability of OM proxies for environmental reconstruction of coastal lakes.     

Diatom community response to multiple scales of Holocene climate variability in a small lake on Victoria Island, NWT, Canada

A lake sediment core spanning 9900 years, collected from a small lake on western Victoria Island, NWT, Canada, provides a high-resolution record of diatom community dynamics over the Holocene. Ten radiocarbon dates and ²¹⁰Pb dating provided the core chronology. Loss-on-ignition (LOI), magnetic susceptibility, biogenic silica content, and diatom concentrations provided information on changes in the sedimentary environment. LOI gradually increased over the Holocene whereas magnetic susceptibility showed an inverse trend. Biogenic silica content showed three distinct peaks spaced approximately 3000 years apart. Major shifts in diatom assemblages occurred at 8100–8000, 5800–5700, and 3800–3500 cal yr BP. There is evidence of diatom community response to centennial-scale variations such as the ‘Medieval Warm Period’ (1000–700 cal yr BP), ‘Little Ice Age’ (800–150 cal yr BP) and recent warming. Although recent changes in diatom community composition, productivity, and species richness are apparent they were surpassed at other periods throughout the Holocene. Variations of the taxa within the genera Staurosira, Pseudostaurosira, Fragilaria, and Staurosirella, usually combined into one genus in Arctic lake sediment studies, suggest these taxa provide useful insight into paleonvironmental questions.     

Seasonal variations of zinc in a eutrophic lake

Depth profiles of dissolved zinc were measured monthly over one year in Lake Greifen, a eutrophic lake. The concentrations are in the range 10–40 nM and show systematic variations over time and depth. Due to the increased binding to particles and subsequent settling, concentrations of zinc in the epilimnion decrease during summer stagnation. Clear correlations between Zn and major nutrients (P, Si) are, however, not observed in the water column. No accumulation of Zn occurs in the anoxic hypolimnion. The Zn sedimentation is related to the sedimentation of algae and of manganese oxide. A mass-balance calculation shows that 87% of the Zn input is retained in the sediments of Lake Greifen.     

Evidence for Holocene climate variability from the sediments of a Scottish remote mountain lake

High resolution sampling of sediment cores covering approximately the last 4000 yr from Lochan Uaine, a small corrie loch in the Scottish Cairngorm Mountains, show quasi‐periodic cycles in organic matter (measured as percentage loss on ignition). Analysis of these cycles show correspondences between loss on ignition, δ¹³C values and chironomid head capsule abundance. We interpret the changes as reflecting changes in lake productivity and hypothesise that they are driven by climate variability. However, it is not yet clear whether the periods of relatively high organic matter production and preservation are associated with colder or with warmer conditions. Nevertheless the results indicate the value of using sediments from remote, undisturbed mountain lakes as recorders of Holocene climate variability. Copyright © 2001 John Wiley & Sons, Ltd.     

Streamflow modeling in a fluctuant climate using SWAT: Yass River catchment in south eastern Australia

Hydrological models play vital roles in understanding and management of surface water resources. The physically based distributed model Soil and Water Assessment Tool (SWAT) was applied to a small catchment in south eastern Australia to determine its ability to mimic low and high streamflows. The model was successfully calibrated using 1993–2002 streamflow data and validated using 2003–2011 data with a combination of manual and auto-calibration techniques for both monthly and daily time steps. Sensitivity analysis indicated that curve number for moisture condition II (CN2) is the most sensitive parameter for both time steps. In general, the model performance statistics indicated “very good” agreement between measured and simulated discharges for both calibration and validation periods. The model was able to satisfactorily simulate both low and high flows of the Yass River. Analysis of water balance components indicated that more than 90 % of the rainfall is lost as evapotranspiration and about 45 % of the streamflow is base flow. The calibrated and validated SWAT model can be used to analyze the effect of climate and land use changes on catchment wide hydrologic process.     

Holocene lake salinity changes in the Wimmera,southeastern Australia,provide evidence for millennial-scale climate variability

Palaeosalinity records for groundwater-influenced lakes in the southwest Murray Basin were constructed from an ostracod-based, weighted-averaging transfer function, supplemented with evidence from Campylodiscus clypeus (diatom), charophyte oogonia, Coxiella striata (gastropod), Elphidium sp. (foraminifera), Daphniopsis sp. ephippia (Cladocera), and brine shrimp (Parartemia zietziana) faecal pellets, the δ¹⁸O of ostracods, and > 130 μm quartz sand counts. The chronology is based on optically stimulated luminescence and calibrated radiocarbon ages. Relatively wet conditions are marked by lower salinities between 9600 yr and 5700 yr ago, but mutually exclusive high- and low-salinity ostracod communities suggest substantial variability in effective precipitation in the early Holocene. A drier climate was firmly in place by 4500 yr and is marked at the groundwater-dominated NW Jacka Lake by an increase in aeolian quartz and, at Jacka Lake, by a switch from surface-water to groundwater dominance. Short-lived, low-salinity events at 8800, 7200, 5900, 4800, 2400, 1300 and 400 yr are similar in timing and number to those recorded on Australia's southern continental shelf, and globally, and provide evidence for the existence of the ~ 1500-yr cycle in mainland southern Australia. We surmise that these are cool events associated with periodic equatorward shifts in the westerly wind circulation.     

Application of equilibrium partitioning approach to derive sediment quality criteria for heavy metals in a shallow eutrophic lake, Lake Chaohu, China

In this study, the equilibrium partitioning approach was used to derive the sediment quality criteria (SQC) recommended values of eight heavy metals (Cr, Cu, Pb, Zn, Cd, As, Fe and Mn) for surface sediments taken from Lake Chaohu. The concentration of the heavy metal in the interstitial water (C _IW) was determined by the film diffusion gradient technology to obtain the metal partitioning coefficient (K _P). Moreover, the metal fractionation of the sediments were analyzed using European Community Bureau of Reference sequential extraction procedure and the partitioning of bound phases including total organic carbon (TOC), grain sizes and acid volatile sulfide (AVS) were also investigated. The values of K _P for Cr, Cu, Pb, Zn, Cd, As, Fe and Mn were 3,924.84, 2,276.23, 17,811.30, 738.35, 10,986.54, 718.74, 5,875.34 and 341.20 L/kg, respectively. Sediment quality criteria were normalized on the basis of fine materials, AVS, TOC and the residual metals (M _R). SQC values for Cr, Cu, Pb, Zn, Cd, As, Fe and Mn based on Chinese surface water quality criteria were derived with the values of 78.53, 56.95, 362.93, 74.68, 23.90, 71.84, 3,546.53 and 68.42 mg/kg, respectively. The suggested SQC values in this study were compared SQCs from different countries and areas, which indicated SQCs from different countries or regions appeared to have great discrepancies attributed to the difference of the physical and chemical characteristics of sediments.     

A record of Holocene climate change from lake geochemical analyses in southeastern Arabia

Lacustrine sediments from southeastern Arabia reveal variations in lake level corresponding to changes in the strength and duration of Indian Ocean Monsoon (IOM) summer rainfall and winter cyclonic rainfall. The late glacial/Holocene transition of the region was characterised by the development of mega-linear dunes. These dunes became stabilised and vegetated during the early Holocene and interdunal lakes formed in response to the incursion of the IOM at approximately 8500 cal yr BP with the development of C3 dominated savanna grasslands. The IOM weakened ca. 6000 cal yr BP with the onset of regional aridity, aeolian sedimentation and dune reactivation and accretion. Despite this reduction in precipitation, the lake was maintained by winter dominated rainfall. There was a shift to drier adapted C4 grasslands across the dune field. Lake sediment geochemical analyses record precipitation minima at 8200, 5000 and 4200 cal yr BP that coincide with Bond events in the North Atlantic. A number of these events correspond with changes in cultural periods, suggesting that climate was a key mechanism affecting human occupation and exploitation of this region.     

Alpine climate during the Holocene: a comparison between records of glaciers,lake sediments and solar activity

The European Alps are very sensitive and vulnerable to climate change. Recent improvements in Alpine glacier length records and climate reconstructions from annually laminated sediments of Alpine Lake Silvaplana give the opportunity to investigate the relationship between these two data sets of Alpine climate. Two different time frames are considered: the last 500–1000 years as well as the last 7400 years. First, we found good agreement between the two different climate archives during the past millennium: mass accumulation rates and biogenic silica concentration are largely in phase with the glacier length changes of Mer de Glace and Unterer Grindelwaldgletscher, and with the records of glacier length of Grosser Aletschgletscher and Gornergletscher. Secondly, the records are compared with temporally highly resolved data of solar activity. The Sun has had a major impact on the Alpine climate variations in the long term, i.e. several centuries to millennia. Solar activity varies with the Hallstatt periodicity of about 2000 years. Hallstatt minima are identified around 500, 2500 and 5000 a. Around these times grand solar minima (such as the Maunder Minimum) occurred in clusters coinciding with colder Alpine climate expressed by glacier advances. During the Hallstatt maxima around 0, 2000 and 4500 a, the Alpine glaciers generally retreated, indicating a warmer climate. This is supported by archaeological findings at Schnidejoch, a transalpine pass in Switzerland that was only accessible when glaciers had retreated. On shorter timescales, however, the influence of the Sun cannot be as easily detected in Alpine climate change, indicating that in addition to solar forcing, volcanic influence and internal climate variations have played an important role. Copyright © 2011 John Wiley & Sons, Ltd.     

Holocene lake sediments from the Faiyum Oasis in Egypt: a record of environmental and climate change

The Qarun Lake in the Faiyum Oasis (Egypt) provides a unique record of Holocene environmental and climate change in an arid area largely devoid of fossil proxy records. Multiple lithological, palaeontological and geochemical proxies and 32 radiocarbon dates from the 26‐m‐long core FA‐1 provide a time series of the lake's transformation. Our results confirm that a permanent lake appeared in the Holocene at c. 10 cal. ka BP. The finely laminated lake sediments consist of diatomite, in which diatoms and ostracods together with lower concentrations of ions indicate a freshwater environment at the end of the early and middle Holocene. This freshwater supply was closely associated with regular inflows of the Nile water during flood seasons, when the Intertropical Convergence Zone (ITCZ) migrated northwards in Africa, although it has probably never reached the Faiyum Oasis. Local rainfall, possibly connected with a northern atmospheric circulation, may have been important during winter. Several phases in the lake's evolution are recognized, represented by oscillations between deep open freshwater conditions during more humid climate and shallow fresh to brackish water during drier episodes. After a long freshwater phase, the lake setting has become more brackish since c. 6.2 cal. ka BP as indicated by diatoms and increasing contents of evaporite ions in the sediment. This clearly shows that since that time the lake has occasionally become partly desiccated. This is a result of reduced discharge of the Nile. In the late Holocene the lake was mostly brackish and then gradually turned into a saline lake. This natural process was interrupted about 2.3 cal. ka BP when a man‐made canal facilitated water inflow from the Nile. The examined FA‐1 core can be used as a reference age model of climate change in the Holocene and its impact on the development and decline of ancient civilizations in northeastern Africa.