Lake Stage Research Articles

Leveraging explainable machine learning for enhanced management of lake water quality

Freshwater lakes worldwide suffer from eutrophication caused by excessive nutrient loads, particularly nitrogen (N) and phosphorus (P) from wastewater and runoff, affecting aquatic life and public health. Using a large (1800 km2) subtropical lake as an example (Lake Okeechobee, Florida, USA), this study aims to (1) predict key water quality parameters using machine learning (ML) algorithms based on easily measurable variables, (2) identify spatial patterns of these parameters, and (3) determine environmental drivers influencing turbidity levels. The study employs four ML algorithms—Extreme Gradient Boosting (XGB), Light Gradient-Boosting Machine (LGBM), Support Vector Regression (SVR), and Random Forests (RFs)—to predict total phosphorus (TP), total nitrogen (TN), nitrate + nitrite (NOx-N), and turbidity, via station-specific and lake-wide modeling approaches. The station-specific models uncover spatial patterns, while the lake-wide models support operational decision-making. Results indicated that lake stage (water level), water temperature, and, most notably, turbidity were the main nutrient predictors, with XGB demonstrating superior prediction performance. Spatial analysis using K-means clustering identified three distinct lake regions based on nutrient levels and turbidity. Due to its importance, SHapley Additive exPlanations (SHAP) were employed to identify and quantify environmental factors affecting turbidity. Inflows and lake stage were found as primary drivers of turbidity near lake inlets, while wind speed and air temperature affected turbidity in the middle of the lake. This research advances the understanding of lake water quality dynamics, emphasizing the importance of frequent monitoring of turbidity and its environmental drivers for enhanced management and future mitigation efforts.

From paleolake to peatland: Paleo environmental changes over glacial and interglacial cycles (Mid-Pleistocene) in the Colônia Basin, Brazil

Diatom and geochemical elements were used to analyze the transition from lake to peatland in the Colônia basin, São Paulo, Brazil; local versus regional driving factors were examined. Sediment core COL17–1, section 1470–800 cm depth shows five distinct diatom intervals offering insights into environmental changes and ecological characteristics based on sediment sources, diatom productivity, and bog wetness. Colônia basin evolution exhibited a progressive transition from mineral elements, associated with catchment instability during the lake stage, to higher levels of organic-rich sediments towards the uppermost section of the core. This shift was accompanied by the increasing presence of elements reflecting redox/productivity dynamics under changing conditions. Simultaneously, Br concentrations increased during peat formation indicating alterations in organic matter were influenced by atmospheric circulation and precipitation. During the transition from lake to peatland, the paleolake shallowing process showed successive colonization by benthic acidophilus diatom taxa, indicating a broader littoral zone and subsequent disappearance of diatoms under dry conditions. After a benthic stage, the diatom content shifted to one of planktonic dominance characterized by Aulacoseira sp., marking the return to cold-wet conditions and a moderately deep, flooded environment. Subsequently, the basin evolved into a completely flooded, turbulent peatland dominated by the Aulacoseira granulata complex. An uppermost layer sterile in diatom was associated with warmer and drier conditions and decrease in the concentration of mineral elements. Present results compared with core CO14 and Lake Titicaca showed benthic-rich levels during the penultimate glacial period and low benthic abundances. This differed the glacial-interglacial transition from those of COL17–1, which was dominated by planktonic-rich levels, suggesting the need for either a reassessment of our age model or the influence of local factors on diatom content. These findings highlight the sensitivity of diatoms to climate shifts, particularly in tropical regions, across different glacial-interglacial cycles.

Water Budget for Lake Trafford, a Natural Subtropical Lake in South Florida: An Example of Enhanced Groundwater Influx in a Subtropical Lake Subsequent to Organic Sediment Dredging

A very detailed water budget analysis was conducted on Lake Trafford in South Florida. The inflow was dominated by surface water influx via five canals (61%), with groundwater influx constituting 12% and direct rainfall constituting 27%. Lake discharge was dominated by sheet flow (69%) and evapotranspiration (30.5%), with groundwater recharge of the hydraulically connected unconfined aquifer accounting for only 0.5%. The removal of 30 M tons (4.4 × 106 m3) of organic sediment impacted the groundwater influx, causing enhanced groundwater flow into the deeper parts of the lake and mixed flow along the banks, creating a rather unusual pattern. The large number of groundwater seepage meters used during this investigation led to a very reliable set of measurements with occasional failure of only a few meters. A distinctive relationship was found between the wet-season lake stage, heavy rainfall events, and pulses of exiting sheet flow from the lake. Estimation of the evapotranspiration loss using data collected from a weather station on the lake allowed the use of three different models, which, when averaged, produced results comparable to Lake Okeechobee (South Florida). A limitation of this investigation was the inability to directly measure sheet-flow discharges, which had to be estimated as a residual within the calculated water budget.

Lacustrine deposition in response to the middle eocene climate evolution and tectonic activities, Bohai Bay Basin, China

The lower unit of the third member of the Eocene Shahejie Formation (Es3L, 42.5 to ∼40Ma) is one of the most important petroleum exploration targets in the Bohai Bay Basin. Lacustrine deposits are widely distributed in the Es3Lunit of the Shulu Sag and display strong vertical and horizontal variations in lithofacies and geochemical characteristics. Based on core data, thin-section petrography, stable δ13C isotope analyses, and organic geochemistry data, eight lithofacies and six evolutionary lake stages are identified. Combining the results of the astronomical time scale (ATS) and the radiometric age, the correlation between the evolutionary lake stages of Es3Land the Eocene global climate curve was illustrated. Tectonic movement caused the basin to subside and resulted in shallow lake formation (Stage 1) during the cooling phase prior to the Middle Eocene Climatic Optimum (MECO); then, the lake level began to rise (Stage 2) with an increasingly warm and humid climate. Stage 3 corresponds to the peak of the MECO and was influenced by the warm and humid climate during the thermal maximum period, forming a deep, freshwater lake. This stage was followed by highly turbulent lake conditions (Stage 4), which were influenced by both the cooling climate and intensive tectonic activity. Subsequently, a stable lake (Stage 5) was formed, which was mainly controlled by the slightly warming climate since the tectonic movement was relatively stable, followed by another stage of turbulent lake conditions (Stage 6). The results show that the global mid-Eocene climate played an important role on the relative lake level changes and TOC enrichment. The MECO led to a rise in the relative sea-level and the obviously rise in relative lake-level in the Bohai Bay Basin. The evolution of the depositional settings was controlled by both global climate and tectonic activities and accounted for the deposition and distribution of lithofacies with distinctly different characteristics and origins.

Formation mechanism of a disaster chain in Loess Plateau: A case study of the Pucheng County disaster chain on August 10, 2023, in Shaanxi Province, China

Under the heavy rainfall risk due to global warming, a new trend has emerged in geological disasters of loess, which have often evolved into a chain form of disaster chain of loess (DCL) in recent years. The DCL is characterized by multiple, hidden, catastrophic, and complex characteristics that seriously affect the construction and operation of large-scale infrastructure on the Loess Plateau. To understand the formation mechanism of a disaster chain of loess, we took the Shiyangpo DCL, a typical disaster chain occurring recently on the Loess Plateau, as an example to investigate the geomorphic features and deformation characteristics of DCL using new technologies and methods such as Unmanned Aerial Vehicle (UAV) mapping and Geographic Information Systems (GIS) spatial analysis technology. A series of special laboratory tests considering the vibration of the loess subgrade was conducted to explore the changes in physical and mechanical properties of loess samples in the study area under natural, saturated, and vibration conditions. Additionally, the trigger factors and evolution process of this DCL were analyzed, and the formation mechanism of recently emerging typical DCL was revealed as well. The triggering factors of the disaster were summarized as follows: loess nature, heavy rainfall, irrigation, irrational excavation, incomplete drainage channels, and long-term vehicle vibration of roadbeds. Furthermore, extreme rainfall was identified as the primary inducing factor of Shiyangpo DCL. Finally, the development and evolution of Shiyangpo DCL were divided into five stages: the formation of the loess sinkhole stage, the occurrence of the loess subsidence stage, the occurrence of the loess collapse stage, the occurrence of the loess landslide stage, and the formation of river-blocking and dammed lake stage. This study reveals the cause and evolution process of the newly emerged DCL in the Loess Plateau, and the new techniques and methods involved can provide references for the theoretical research and prevention of loess geological disasters in other places.

An Amphibole Perspective on the Recent Magmatic Evolution of Mount St. Helens

Abstract Compositional variations of amphibole stratigraphically recovered from multiple eruptions at a given volcano have a great potential to archive long-term magmatic processes in its crustal plumbing system. Calcic amphibole is a ubiquitous yet chemically and texturally diverse mineral at Mount St. Helens (MSH), where it occurs in dacites and in co-magmatic enclaves throughout the Spirit Lake stage (last ~4000 years of eruptive history). It forms three populations with distinct geochemical trends in key major and trace elements, which are subdivided into a high-Al (11–14.5 wt% Al2O3), a medium-Al (10–12.5 wt% Al2O3), and a low-Al (7.5–10 wt% Al2O3) amphibole population. The oldest investigated tephra record (Smith Creek period, 3900–3300 years BP) yields a bimodal amphibole distribution in which lower-crustal, high-Al amphibole cores (crystallized dominantly from basaltic andesite to andesite melts) and upper-crustal, low-Al amphibole rims (crystallized from rhyolitic melt) document occasional recharge of a shallow silicic mush by a more mafic melt from a lower-crustal reservoir. The sudden appearance of medium-Al amphiboles enriched in incompatible trace elements in eruptive periods younger than 2900 years BP is associated with a change in reservoir conditions toward hotter and drier magmas, which indicates recharge of the shallow silicic reservoir by basaltic melt enriched in incompatible elements. Deep-crystallizing, high-Al amphibole, however, appears mostly unaffected by such incompatible-element-enriched basaltic recharge, suggesting that these basalts bypass the lower crustal reservoir. This could be the result of the eastward offset position of the lower crustal reservoir relative to the upper crustal storage zone underneath the MSH edifice. Amphibole has proven to be a sensitive geochemical archive for uncovering storage conditions of magmas at MSH. In agreement with geophysical observations, storage and differentiation have occurred in two main zones: an upper crustal and lower crustal reservoir (the lower one being chemically less evolved). The upper crustal silicic reservoir, offset to the west of the lower crustal reservoir, has captured compositionally unusual mafic recharge (drier, hotter, and enriched in incompatible trace elements in comparison to the typical parental magmas in the region), resulting in an increased chemical diversity of amphiboles and their carrier intermediate magmas, in the last ~3000 years of MSH’s volcanic record.

Assessing the Diversity of Metazoan Parasites of Sarotherodon melanotheron (Cichlidae) from Inlands Waters in Southern Benin (West Africa)

Aims: This paper presents a snapshot of the metazoan parasite fauna of Sarotherodon melanotheron collected from two stations across lake Nokoué.
 Study Design: Fish samplings were done at the landing stage of Lake Nokoué (sampling site 1) and Tota (sampling site 2) from october 2016 to march 2017. Water physicochemical parameters such as pH, salinity, temperature, and conductivity were measured monthly. 
 Methodology: A total of 246 specimens of Sarotherodon melanotheron comprising 149 males and 97 females were investigated. Size and weight were measured. Then,fish were dissected and parasites were checked in several organs. Collected parasite were identified using adequate keys of identification. The chi square test was used to compare the prevalence of different parasite groups whereas Student T-test was applied to assess difference between parasite mean abundance within the two sampling stations. The pearson correlation coefficient was used to appraise possible influence of water parameters on parasite prevalence.
 Results: The total prevalence was 86.58%. Eight parasite species were collected belonging to Myxosporidia, Monogena, Digena, Cestoda, Acanthocephala and Copepoda. Epidemiological parameters were calculated in order to appreciate the diversity of the parasitofauna according to sampling site, sex, and fish size. Females were significantly more infected than males (χ2 = 10.093; p < .05). Among the parasites, only monogenean prevalence (41.46%) was significantly different (χ2 = 149.645; p < .05). Correlation between physicochemical parameters and the prevalence of parasite groups showed that monogenea and cestoda were the most abundant in rainy season in opposite to the Digena that are mainly recorded in the dry season.

Climatic controls on the water balance of a pilot-scale oil sands mining pit lake in the Athabasca oil sands region, Canada

ABSTRACT Energy companies in the Athabasca Oil Sands Region in Alberta, Canada are evaluating the viability of incorporating pit lakes into reclamation closure designs to both sequester tailings and re-integrate the mining lease into the broader natural landscape. Lake Miwasin is a pilot-scale oil sands pit lake encompassed by a constructed catchment where the volume of the water cap is not actively managed. This study compared the water balance during the open water season over two consecutive years with contrasting levels of summertime precipitation. The first year had above average rainfall triggering surface water inflow events that diluted the over-winter water volume by ~ 25%. Flushing of the deepest layers of the water column was restricted from May – September as thermal stratification inhibited complete lake mixing. The second year had below average rainfall resulting in minimal surface water inflow and a drop in lake stage of ~ 30 cm. As the constructed catchment lacks both natural water bodies and connectivity to a legacy groundwater system, freshwater additions to the lake during the summer season were governed by rainfall. This research highlights challenges with constructing sustainable reclamation landscapes within a region characterised by variations in interannual and decadal water cycles.

Depositional controls in an ancient, closed lake system: A high-resolution and multi-scalar case study from the Yacoraite Formation (Salta Basin, Argentina)

The Yacoraite Formation (Cretaceous–Paleogene) is a mixed carbonate–siliciclastic microbialite-bearing lacustrine succession deposited in the intra-continental Salta rift basin (Argentina). In the northern sub-basin of Tres Cruces, the spectacular exposures and high lateral continuity of the outcrops provide a suitable setting to investigate and reconstruct the paleoenvironments of deposition and the resulting facies architecture of this closed, saline lake system. The Yacoraite Formation deposited in a predominantly shallow-water ramp-like lake system, characterized by eighteen main facies, classified within four main facies associations, each defining a particular depositional environment along the lake profile. From proximal (shallow) to distal: i) Palustrine Facies Association; ii) Littoral Facies Association; iii) Sub-littoral Facies Association; and lastly iv) Profundal Facies Association. In the Yacoraite paleo-lake extensive fringing mud-flat environments surrounded the lake margins, while the littoral marginal areas hosted extensive wave-dominated oolitic–bioclastic grainstones forming shoals and bars parallel to the lake margins and provided a sheltered environment in the back-shoals that allowed prolific microbialite development. In proximity to river inputs, shallow-water deltas and shoreline sandstones accumulated in the littoral margins. In the sub-littoral zone, mud-supported carbonates such as ostracod wackestones and mudstones deposited below the fair-weather wave base, and in the profundal settings deep-water organic-rich shales deposited. The Yacoraite paleo-lake evolved from a relatively stable and perennial lake system (lake stage 1) into a rapidly fluctuating ephemeral lake system (stage 2), as a result of progressively changing environmental and climatic conditions toward more arid settings. Climate control is also critical in the facies architecture, with the development of short-term cyclicity, represented by meter-scale transgressive–regressive (T–R) cycles being the result of lacustrine expansion–contraction cycles. The regressive hemicycles represent shallowing-upward succession of sub-littoral and littoral carbonate-dominated facies, whereas the transgressive hemicycles are mostly represented by sub-littoral and profundal mudstones and shales. Stacking of short-term cycles resulted in the development of medium- and long-term cyclicity at the scale of tens of meters, which represent the long-term evolution of the lake system. Lastly, a comparison with two well-documented closed lake systems highlights the role of allogenic factors acting at a regional scale (e.g., climate and tectonics) in controlling the lake-basin type, facies association and the resulting architecture. Factors at the lake-basin scale (e.g., lake margin profile, bathymetry) modulate the expression of facies and cyclicity. Ultimately, the characterization of the kilometer-scale outcrops of the Yacoraite paleo-lake provides a reference analog study to support the characterization of similar depositional systems and reservoirs of other ancient, closed lake systems, including the Pre-Salt Carbonates of the South Atlantic.

Depositional cycles in a rift lacustrine basin linked with tectonics, climate, and source rocks and reservoirs development: Lower Cretaceous in Naiman sag, Songliao Basin, Inner Monglia, Northeast China

In order to improve understanding of the depositional evolution processes in rift lacustrine basins in Northeast China under Early Cretaceous greenhouse climate fluctuations, the roles of tectonics and climate along with the development of source rocks and reservoirs in the evolution of continental rift lacustrine basins in Naiman sag, Songliao Basin, Inner Monglia, were studied. Based on the detailed facies analysis of the subsurface boreholes, eight facies were identified in the Lower Cretaceous strata of Naiman sag and were grouped into three facies associations, namely fan delta, littoral to sublittoral lacustrine, and deep lacustrine. Based on the depositional characteristics, in combination with lacustrine evaporites and carbonate deposition, organic matter preservation, and lake depth, the Lower Cretaceous strata of the Naiman sag was further subdivided into four lake stages, namely initial formation of lake (Stage 1), sediment-fill shallow lake (Stage 2), rising to a high lake (Stage 3), and lake closure (Stage 4), respectively. The lake evolution in the Naiman sag was driven by both tectonics and climate changes. Fault-driven subsidence was likely contributed to episodic changes in accommodation and lake formation (Stage 1), expansion (Stage 3) and shrinkage (Stage 4). A combination of regional and global climate overprint controlled the sedimentary characteristics, depositional trends, and sediment and water supply. The global climate of ocean anoxic events 1a and 1b (OAE1a and OAE1b) may have effects on anoxic conditions of Stages 1 and 3, respectively. During regional climate changes between arid, hot and humid, seasonal climate tended to form evaporite deposits and multiple layers of oil shale deposits in Stage 1. During the more humid regional climate, steady runoff tended to form fan delta deposits prograding into the lake basin in Stages 2 and 4 and thick-bedded oil shale deposits in Stage 3. The development of source rocks is linked with lake formation and expansion stages (Stages 1 and 3), and the source rocks are mainly preserved in the deep lacustrine and littoral to sublittoral lacustrine environment. The development of reservoirs is associated with lake formation, sediment-fill, and shrinkage stages (Stages 1, 2, and 4), and the reservoirs are mainly preserved in the fan delta environment.

Valley morphology and Quaternary seismic stratigraphy of the Manicouagan impact crater lake (Eastern Canada)

ABSTRACTLakes in formerly glaciated regions can provide valuable paleoclimate archives. Lake Manicouagan (Manikuakan, according to Innu toponymy), formed in the basin of the ~214‐Ma Manicouagan impact crater of eastern Québec, is a key area for reconstructing long‐term environmental change, as it was directly affected by the Pleistocene glaciations and the waxing and waning of the Laurentide Ice Sheet. Here, we present high‐resolution seismic data revealing an overdeepened bedrock valley filled with a sedimentary sequence. We assess its potential to serve as a paleoclimate archive. The varying shape of the overdeepened valley indicates complex erosional processes. A lower narrow V‐shaped gorge is indicative of either pressurized subglacial meltwater or pre‐Quaternary fluvial erosion, or a combination of both. Three scenarios are discussed regarding deposition of the sedimentary sequence: (i) deposition only during and after retreat of the last glacial episode; (ii) deposition during multiple glacial–interglacial cycles; and (iii) deposition mainly during a subglacial lake stage. We suggest subglacial followed by proglacial sedimentation as the most probable scenario for deposition of the sedimentary succession. We recommend considering the sediments of Lake Manicouagan as a paleoclimate archive reaching back at least to 7.5 ka, but the lake also probably contains sediments deposited before the last deglacial period.

Tectonic and climatic controls on carbonate sedimentation in active orogen proximal lakes, Cenozoic Qaidam Basin, northern Tibetan Plateau

AbstractPalustrine‐lacustrine carbonates of the well‐dated Xichagou section (ca. 43 to ca. 13 Ma) next to the active Altyn Tagh Fault (ATF) are investigated in terms of abundance, lithofacies, strontium, carbon and oxygen isotopes, to differentiate tectonic and climatic controls on the evolution of intermontane lakes in the Tibetan Plateau. Volumetrically dominant siliciclastic strata document five depositional stages: mid‐Eocene alluvial fan (onshore), late Eocene fan delta (nearshore), Oligocene semi‐deep lake (offshore), early Miocene braided fluvial delta (nearshore) and mid‐Miocene fluvial plain (onshore). Carbonates are most abundant in the middle three lacustrine stages and contain various lithofacies, including calcretes, microbialites, grainstones and marlstones. Oxygen isotopes show two positive excursions (−1.17‰ and −2.59‰) at the first nearshore and late offshore stages, indicating two relatively saline stages linked to the Eocene and late Oligocene global warming climates. Carbon isotopes show a positive excursion (from −4.0‰ to +2.9‰) at the middle semi‐deep lake stage and meanwhile strontium isotopes of carbonates show a large negative excursion (from 0.7120‰ to 0.7113‰), both in response to the early Oligocene global humid and cooling climate and resultant lake expansion at the Qaidam Basin. Except for this lake expansion event, the first‐order lake transgressing, shallowing and regressing evolution at the Xichagou section were not consistent with Cenozoic global climatic change trends. Instead, the two‐stage strike‐slip faulting of the ATF probably induced the northeastward and eastward migration of basin depocenter and resulted in the lake transgression‐regression at the Xichagou section. The widespread presence and relatively minor variation in oxygen isotopes (from −7.5‰ to −7.0‰) of early Miocene microbialites in the northern Tibetan Plateau suggest a warm climate and a low relief before ca. 15 Ma.

A 5500-year record of coastal dune evolution along the shores of Lake Michigan in the North American Great Lakes: The relationship of lake-level fluctuations and climate

Dune fields line much of the ∼1750-km long shore of Lake Michigan that extends from northwestern Indiana, north along the west coast of Lower Michigan, and west across southern Upper Michigan. Numerous geomorphic studies at specific sites or defined coastal reaches have demonstrated that dune formation began during the Nipissing maximum (∼5500–4500 calendar year Before Present (cal yr BP) and continued episodically to the present. Dune formation in these geographically confined areas is linked mostly to high lake stages and periods of increased storminess. Some recent research has also invoked drought as a potential causal mechanism on a site-specific basis. Although more than 250 collective absolute carbon-14 (14C) and optically stimulated luminescence (OSL) ages have been acquired in these many studies, a comprehensive statistical assessment of this robust dataset has yet to be conducted to reconstruct a full chronological reconstruction of dune evolution.This study statistically analyzes the dataset of all known OSL (118) and 14C ages (175) acquired directly from sand dunes. Application of a kernel density estimation (KDE) algorithm function to both datasets revealed the temporal patterns in the ages. Analysis of OSL ages indicates three major periods of dune growth, beginning between ∼5.0 and 3.8 ka during the Nipissing high stand and subsequent regression. The second phase occurred between ∼3.0 and 2.0 ka during the Algoma high stand and regression. Finally, the most recent interval of dune growth transpired between ∼1.3 and 0.8 ka in the aftermath of a high lake stage at ∼1.7 ka and another, shorter peak in lake level at ∼1.0 ka. These findings indicate that major pulses of dune building mostly occur during lake regressions. They also correspond to the relatively warmer and drier conditions of the Holocene Climate Optimum, Roman Climate Optimum, and Medieval Warm Period, respectively, as well as periods of relative drought in the region. These associations indicate that drier conditions may have contributed to dune activation.Plotting of 14C data reveals no single variable, such as stability or burial, explains the timing of the four peaks in the kernel distribution of ages derived from organic remains. Intervals of higher 14C age frequencies occurred between ∼4500 and 3800 cal yr BP, ∼3500 and 2600 cal yr BP, ∼2300 and 1600 cal yr BP, and ∼700 and 200 cal yr BP. The peak at ∼4200 cal yr BP corresponds with a similar OSL pattern, indicating that 14C ages derived from weakly developed Entisols during this interval reflects their burial by eolian sand. Peaks in 14C densities within the latter intervals at ∼3200, ∼1800, and ∼400 cal Yr BP align with distinct drops in the OSL distribution. This pattern indicates that 14C ages from these intervals reflect episodes of stability and soil formation subsequent to episodes of dune building. Although this study demonstrates the general patterns of dune growth and stability, local variations in behavior likely occurred.

Glacier retreat analysis in the context of climate change impact over the Satopanth (SPG) and Bhagirathi-Kharak (BKG) glaciers in the Mana basin of the Central Himalaya, India: A geospatial approach

• Glacier retreat footprints over the Mana Basin. • Spatio-temporal changes in the snout/glacier over the period of 50 years. • Estimation of ice velocity using the SAR technique. • Negative trend in snow cover area and increase of temperature. This study explores the dynamics of the Satopanth (SPG) and Bhagirathi-Kharak (BKG) glaciers of the Mana basin in the Central Himalayan region of India under the scenario of climate change. The spatio-temporal changes in the glacier area, volume, and shift in snout positions during the period from 1968 to 2017 were assessed based on the CORONA photograph and satellite data . The study also intended to identify the common drifts in glacier areas for observing temporal and seasonal (during the winter-spring-summer transition) changes in the glacial landscapes and ably evaluate glacier velocity and ice-marginal lake stage. The ice velocity was found to vary from 0.117 md −1 to 0.165 md −1 for January to October months. It was found to have increased during the winter-spring-summer transition periods used to estimate the ice flow intensity and its phase information regular basis. Besides this, the linear trends of the MOD11A2 land surface temperature product were obtained and temperature variability has been analyzed from 2001 to 2020. The results show significant warming over the basin along with a significant negative trend in snow cover area during different seasons. The derived information is quite useful in analyzing the climate change footprints such as snowline movement, snow volume changes, and glacier mass balance-related studies.

Sedimentary facies and clay mineralogy of the late Pleistocene Landsort Deep sediments, Baltic Sea — Implications for the Baltic Ice Lake development

ABSTRACT The Landsort Deep is the deepest part of the Baltic Sea and contains an excellent high-resolution late Pleistocene sediment record suitable to study the retreat history of the southern margin of the Fennoscandian Ice Sheet and the development of the ice-marginal Baltic Ice Lake (BIL) from ~13.5 to 10.5 ka BP. The studied cores are from the lithostratigraphic Units V and VI of Hole M0063C that were recovered during the Integrated Ocean Drilling Program (IODP) Expedition 347. The subdivision and interpretation of the studied BIL record are based on the identification of seven distinct sedimentary facies, grain size characteristics, detrital clay minerals, water and carbon content, and physical properties. The ice-rafted debris (IRD) in the lowermost part of Unit VI indicates a proximal glaciolacustrine environment. The onset of the Fennoscandian Ice Sheet deglaciation during the warm Bølling/Allerød interstadial caused a rise of the proglacial lake water level and the transition from ice-proximal (IRD-containing sediments) to ice-distal varved sediments (rhythmically laminated silty clays) detected within the middle part of Unit VI. This depositional unit of constant sedimentation was followed by the first drainage event of the BIL, which led to the deposition of a distinct clay-rich interval representing erosion and redeposition of the emerged lake bottom sediments. The reduced grain size of the overlying sediments is associated to the onset of cooler climate conditions and a possible ice sheet readvance during the Younger Dryas that resulted in a decrease of meltwater release and sediment availability. The higher sand content and kaolinite peak are associated to a rapid ice retreat and the release of abundant sediment laden meltwater plumes at the end of the Younger Dryas. The final drainage of the BIL enabled the erosion of coastal clay sediments, and the termination of the ice lake stage led to enhanced clay sedimentation to the Landsort Deep.

A chronology of depositional coastal landforms of the Baltic Sea: Luminescence dating of sandy sediments and patterns of human settlement at the ancient Ventspils Lagoon

The ancient Ventspils Lagoon is an area where human settlements have been located on former coastal landforms and sediments. However, the chronology of its development has so far not been studied in detail. Since the ancient lagoon is dominated by sand deposition, optically stimulated luminescence dating (OSL) was used to determine when the ancient coast was formed. Twenty-one OSL samples gave a wide age range, between 8.57 ± 0.65 ka and 73.8 ± 8.3 ka. Twelve of the ages fall in the Late Glacial and Holocene and document the development of the lagoon between the Baltic Ice Lake stage (∼16 ka) and the Littorina Sea stage (∼8 ka). The new dates correspond to some extent with previously modelled shorelines for the Ventspils Lagoon and to radiocarbon ages from archaeological sites in the area. One date, 16.0 ± 1.3 ka, falls in the period before the Baltic Ice Lake and represents either a very early Baltic Ice Lake stage or, less likely, the Venta glacial lake prior to the Baltic Ice Lake. One date, 5.09 ± 0.42, is likely underestimated. Seven samples yielded dates between 21.5 ± 1.5 ka and 73.8 ± 8.3 ka, which corresponds to the Early and Middle Weichselian in the Baltic region. The samples in this latter group are likely overestimating the true age due to insufficient exposure to sunlight during deposition.

Evolution of organic matter quantity and quality in a warm, hypersaline, alkaline lake: The example of the Miocene Nördlinger Ries impact crater, Germany

The Nördlinger Ries (NR) impact crater in southern Germany contains Miocene lacustrine fine-grained post-impact sediments, which were deposited under saline, alkaline, and hydrologically closed aquatic conditions. To obtain information on the organic matter quantity, quality and environmental evolution, samples from one central (NR 1973) and one more marginal (Enkingen SUBO-18) well were analyzed by pyrolytic, organic geochemical and micro-petrographic techniques. Deposits of the marginal drilling can be linked to the thicker stratigraphic units of the well from the lake center based on total organic carbon (TOC), hydrogen index (HI) and lithology. Central deposits contain mainly hydrogen-rich type I kerogen with a mean HI of 447 mg HC/g TOC, whereas the marginal sequence contains type II-III kerogen with an average HI of 206 mg HC/g TOC. In the center, high total sulfur (TS) over TOC ratios of 1.5 on average, and δ13C values of biomarkers in combination with low α-/total MTTC (α-/total methyl-trimethyltridecyl chromans ∼ <0.6) and Pr/Ph ratios <0.2 suggest the prevalence of hypersaline water. Salinity only decreased during deposition of the uppermost Miocene units, when the then shallow alkaline lake turned, at least temporarily, into acidic-neutral conditions during the time of peat deposition. A similar trend, but at overall lower salinities is recorded for the marginal site. Water stratification in the center is stronger than in the marginal domain based on salinity variation. Anoxic bottom water prevailed in the whole lake, as recorded by exceptionally low Pr/Ph ratios (∼<0.2), the occurrence of des-A-lupane and small pyrite framboids (<5 µm) except for the youngest layers of the Miocene lake. Autochthonous, halophilic red algae/plankton prevailed as reflected by abundant C27steranes, while terrestrial material and aerobic bacteria significantly contributed to the OM only in the latest stages of lake as evident from abundant vitrinite/inertinite particles, high values of diterpenes/C27sterane (up to 255) as well as low values of C27-29regular steranes/C29-32hopanes (<0.5). The same trend, but less well resolved, can be seen at the margin of the paleo-lake.

Structure of Zoobenthos at Different Stages of Ecosystem Succession in Thermokarst Water Bodies of the Central Yamal Peninsula

The taxonomic composition, structure, and spatial distribution of zoobenthos have been studied in 25 water bodies of the Arctic tundra. Eight types of thermokarst water bodies, representing the stages of the succession cycle, have been identified for the central Yamal Peninsula. Water bodies of the initial stages of the cycle are located on the hills, the middle stages are at the edge of the valleys, and the latest stages are in the valleys. In total, 161 species of zoobenthos have been found; their abundance and diversity vary within a wide range according to reservoir type. The number of species per sample ranges 1–33, abundance 0.02–23.40 thousand ind./m2, and biomass 0.05–73.09 g/m2. The trophic status of studied water bodies changes gradually from hypereutrophic at the beginning of the cycle (bog stage) to ultraoligotrophic (lake stage), becoming hypereutrophic at the end of the cycle (khasyrei stage). During succession, the abundance of zoobenthos decreases due to the replacement of small forms by larger ones: a complex dominating by biomass changes from chironomid at the beginning of the cycle, through bivalves and oligochaetes at lake stages, to gastropods and gammarids at the end of the cycle. Feeding preferences of zoobenthos change from phytophagous, through a wide spectrum (including filter-feeding), to phytophagous and detritus-feeding.

Spring onset and seasonality patterns during the Late Glacial period in the eastern Baltic region

Abstract. Spring onset is an important phenological observation that is sensitive to modern climate change and can be traced back in geological time. The Late Glacial (∼ 14 500–11 700 cal yr BP) spring onset and growing season (growing degree days) dynamics in the eastern Baltic region were reconstructed using the micro-phenological approach based on the dwarf birch (Betula nana) subfossil leaf cuticles. The presented study sites, Lake Lielais Svetinu (eastern Latvia) and Lake Kosilase (central Estonia), are located ∼ 200 km apart in the region affected by the south-eastern sector of the Scandinavian Ice Sheet. During the Late Glacial period the region and its biota were influenced by the retreating glacier and the different stages of the Baltic Ice Lake. The plant macrofossil data confirm that the study sites were in different vegetation zones (arctic-to-boreal) during the Late Glacial period. The dynamics of the estimated length of the growing season and spring onset, combined with the regional collection of plant macrofossil records, suggest the importance of local settings to species migration. During the Late Glacial warming period (Bølling–Allerød), a notable spring warming and longer growing season was calculated based on micro-phenology, but the treeline did not extend beyond central Estonia. The comparison of pollen- and chironomid-inferred past temperature estimations with spring onset, growing degree days, and plant macrofossil data shows coherent patterns during the cooler Older Dryas and warmer Bølling–Allerød periods, while suggesting more complicated climate dynamics and possible warmer episodes during the Younger Dryas cold reversal.

Stable isotopes reveal the lake shrinkage and groundwater recharge to lakes in the Badain Jaran Desert, NW China

The evolutionary stages of the different lakes in the Badain Jaran Desert (BJD) are unknown, and there is a need to elucidate the hydrological implications of the hydrodynamic environmental differences among these lakes. In this study, a stable isotope mass balance model incorporating the effect of evaporation from the lake basins was developed, and the model was used to calculate the remaining water fraction f of 94 lakes relative to the high lake levels in the Middle Holocene, as well as the groundwater recharge rate χG to the lakes. The results show that only 10–20 % (average of 15 %) of the original lake water remains. One-third of the lakes have become terminal lakes, and half are still gradually drying. If the climatic conditions remain unchanged, the water levels of these lakes will drop by an average of 11 mm per year. χG has a certain degree of correlation with elevation, suggesting the likely presence of more water recharge sources for the north lakes, which may include the Beida Mountains and the Zongnai Mountains. The total annual groundwater recharge to all of the lakes in the BJD is 1.63 × 107 m3/yr. The δ18O evolution model of a typical lake (Cherigele Lake) reveals that humidity h and atmospheric vapor δa18O play the leading role in the evolution of the lake δ18O, suggesting that this model may serve as a tool for estimating lake evaporation and for reconstructing the paleoclimate. The findings of this study provide support for analyzing the evolution and future trends of lakes in arid desert areas, as well as deeper insights into the water cycle in the BJD.