This study describes the origin, bedrock geology, geomorphology, hydrological stability and physical and chemical characteristics of a representative set of 29 lakes in the ice-free parts of the Ulu Peninsula, James Ross Island, located close to the northern tip of the Antarctic Peninsula. Based on these features, six different types of lakes were defined: stable shallow lakes on higher-altitude levelled surfaces, shallow coastal lakes, stable lakes in old moraines, small unstable lakes in young moraines, deep cirque lakes and kettle lakes. We observed a significant relationship between lake type and water chemistry. Bedrock, lake age and morphometry together with altitude were the most important factors underlying the observed limnological variability. Our results further suggested possible nitrogen limitation in the lake ecosystems. However, physical factors such as low temperature and light were also likely to be limiting.

a b s t r a c tMore than 2000 of mountain lakes covering more than 0.1 ha exist in a territory of Kyrgyzstan. Nearly 20% of them are dangerous because of instability of lake dams, frequent overflows and melting of buried ice inside the moraine dams. According to the Kyrgyz lake inventory, 328 lakes are at risk of outburst and 12 lakes are considered as actually dangerous. Since 1952 more than 70 disastrous cases of lake outbursts have occurred. The majority of the endangered lakes belong to one of the three genetic types: morainic-glacier, supraglacial and lake dammed by landslides and debris flows. Petrov, Adygine and Koltor lakes were selected and studied in the Tien-Shan Mountains as case studies of the most frequent genetic types of hazardous lakes. Observations were focused on the morphology of the lake basin and the surrounding relief, outflow pattern and processes controlling the development of lake. For the hazard assessment, evolution of glaciers and lakes was reconstructed using historical reports, aerial photographs and satellite images.

An interdisciplinary study of glacier-related hazards in the Petrov lake region (Ak-Shiirak Range, the Inner Tien-Shan, Kyrgyzstan) has been undertaken to identify potential dangers to the area. A cooperative effort from experts in the fields of hydrology, glaciology, geomorphology and geophysics has been employed in this study. For the hazard assessment, evolution of the Petrov glacier and lake was reconstructed using historical reports, aerial photographs and satellite images. Geomorphological mapping and geophysical soundings was applied to the lake territory and the moraine dam. This has identified potentially hazardous areas of the dam including subsurface drainage zones and cracks that could cause a sudden extremely high discharge. In the past three decades, the Petrov lake has doubled in size, while in recent years, its area has been increasing by more than 92,000 square metres per year. Although there is no evidence for an imminent outburst, the dramatic increase in the lake's size emphasizes the importance of this study.

The Hercynian mountain ranges were islands of mountain glaciation and alpine tundra in a Central European ice‐free corridor during the Late Pleistocene. Today they are notable areas of glacial landforms, alpine‐forest free areas, peatlands and woodlands. However, our knowledge of the Lateglacial and early Holocene environmental changes in this region is limited. We present a new multi‐proxy reconstruction of a mid‐altitude environment in the Bohemian Forest spanning this period. A core (5.2 m length) in the Černé Lake cirque (1028 m a.s.l.) was subjected to lithological, geochemical, pollen and macrofossil analysis supplemented by two optically stimulated luminescence (OSL) and 10 AMS radiocarbon dates. We determined the impact of regional and supraregional climate changes on the environment. The two most significant changes in sedimentation during the Lateglacial (17.6 and 15.8–15.5 cal. ka BP) were synchronous with regional glacial chronostratigraphy. Unlike Central European mountain ranges, in the Bohemian Forest the Younger Dryas was not coincident with glacier re‐advance, but was a dry, cold episode with low lake levels, which prevailed until the early Preboreal. Plant macrofossils indicate local establishment of Betula nana and Betula pendula/pubescens at 15.4–13.4 cal. ka BP. Comparison with Holocene records from Central Europe shows a similar immigration history of vegetation at mid and higher altitudes. The tree line exceeded an altitude of ~1000 m a.s.l. around 10.5 cal. ka BP and coincided with rapid geochemical changes in the sediment. The 8.2 ka BP event did not have any response in the sedimentary record, but corresponded to stabilization of the Picea abies population and expansion of Fagus. Fagus colonized the Bohemian Forest earlier than other Hercynian mid‐mountains, but never predominated in the composition of the forest at higher elevations. Abies alba was the last tree species that immigrated to the study area.

a b s t r a c tChanges in the water properties and biological characteristics of the highly acidic Hromnice Lake (Western Bohemia) were investigated. This 110-year-old lake, formed as a consequence of the mining of pyritic shales, is permanently meromictic. Two chemoclines separate an extremely acidic (pH ∼ 2.6) mixolimnion from a metal-rich anoxic monimolimnion. The absence of spring mixolimnetic turnover due to ice melting and very slow heat propagation through the chemocline with a 6-month delay were observed. Extreme mixolimnetic oxygen maxima (up to 31 mg l −1 ) in phosphorus-rich lake (PO 4 3− up to 1.6 mg l −1 ) well correlated with outbursts of phytoplankton. Phytoplankton consist of several acido-tolerant species of the genera Coccomyxa, Lepocinclis, Chlamydomonas and Chromulina. Surface phytoplankton biomass expressed as chlorophyll-a varies from 2 to 140 g l −1 . Multicellular zooplankton are almost absent with the exception of Cephalodella acidophila, a small rotifer occurring in low numbers. Large red larvae of the midge Chironomus gr. plumosus were found at the bottom close to the shore, with larvulae in the open water. Developmental stages (protonemata) of a moss, resembling filamentous algae, dwell in the otherwise plant-free littoral zone.

No abstract

Abstract. The formation and development of glacial lakes in mountainous regions is one of the consequences of glacier recession. Such lakes may drain partially or completely when the stability of their dams is disturbed or as a consequence of impacts. We present a case study from the Central Asian mountain range of Tien Shan – a north-oriented tributary of the Adygine Valley, where the retreat of a polythermal glacier surrounded by permafrost has resulted in the formation of several generations of lakes. The aim of this study was to analyse the past development of different types of glacial lakes influenced by the same glacier, to project the site's future development, and to evaluate the outburst susceptibility of individual lakes with an outlook for expected future change. We addressed the problem using a combination of methods, namely bathymetric, geodetic and geophysical on-site surveys, satellite images and digital elevation model analysis, and modelling of glacier development. Based on this case of the glacial lakes being of varied age and type, we demonstrated the significance of glacier ice in lake development. Lake 3, which is in contact with the glacier terminus, has changed rapidly over the last decade, expanding both in area and depth and increasing its volume by more than 13 times (7800 to 106 000 m3). The hydrological connections and routing of glacier meltwater have proved to be an important factor as well, since most lakes in the region are drained by subsurface channels. As the site is at the boundary between continuous and discontinuous permafrost, the subsurface water flow is strongly governed by the distribution of non-frozen zones above, within, or beneath the perennially frozen ground. In the evaluation of lake outburst susceptibility, we have highlighted the importance of field data, which can provide crucial information on lake stability. In our case, an understanding of the hydrological system at the site, and its regime, helped to categorise Lake 2 as having low outburst susceptibility, while Lake 1 and Lake 3 were labelled as lakes with medium outburst susceptibility. Further development of the site will be driven mainly by rising air temperatures and increasingly negative glacier mass balance. All three climate model scenarios predicted a significant glacier areal decrease by 2050, specifically leaving 73.2 % (A1B), 62.3 % (A2), and 55.6 % (B1) of the extent of the glacier in 2012. The glacier retreat will be accompanied by changes in glacier runoff, with the first peak expected around 2020, and the formation of additional lakes.

Anthropogenic lakes (lakes that have developed in mined-out pits as a consequence of mineral raw material mining) exhibit many interesting phenomena. Specific water features are the most remarkable, including physical, chemical and the biological characteristics. Other very specific morphometric feature of anthropogenic lake basins include the unusual location of the lake’s water surface: often several dozen meters below the adjacent terrain and the specific character of the mined-out raw materials. All of these factors affect the qualitative characteristics of lake’s water, even decades after flooding. The interaction of the factors mentioned above has resulted in the creation of a permanent meromixis in some anthropogenic lakes. The author’s primary objectives are to present some physical and chemical symptoms of meromixis at selected localities, to discuss the mutual interaction between the physical and chemical characteristics of lake water and to explore some probable causes of the origin of meromixis at the selected localities.