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During the Holocene, multiple thermal changes commonly occurred in the northern hemisphere. They are well-recorded in lakes with minimum human impact from the Arctic Circle area. The development of these lakes reflects ecological and climatic changes occurring from the formation of the lakes until present-day times. All environmental fluctuations affect biodiversity and are reflected in the number and composition of species. The goals of this study were to detect the ecological changes in a small Finnish lake using pollen, Cladocera and geochemical analyses. The research area is located within the northern zone of boreal coniferous forest and is the most sparsely populated region of Finland. The lake is located in Kuusamo uplands, E Finland, near the polar circle and over 20 km from the Russian border. Indicators of cold water were found only during the initial stage, after the 8.2 ka event and then the temperature was higher. Trophy was high at the beginning of the lake development and then a significant increase in trophy was found after 2600 BP. The impact of human activity is hardly traceable in Arctic Circle Finland throughout the Holocene Thermal Maximum. During the late-Holocene (after 4200 yr cal. BP), this impact is still weak and, even as late as the 20th century, only a few traces of human activity are recorded. General conclusion is that long-term climatic shift has been the most important factor driving changes in the limnology of Lake Talvilampi. [ABSTRACT FROM AUTHOR]

Lauterbach, S., Brauer, A., Andersen, N., Danielopol, D. L., Dulski, P., Hüls, M., Milecka, K., Namiotko, T., Plessen, B., von Grafenstein, U. & DecLakes participants 2010: Multi-proxy evidence for early to mid-Holocene environmental and climatic changes in northeastern Poland. Boreas, 10.1111/j.1502-3885.2010.00159.x. ISSN 0300-9483. We investigated the sedimentary record of Lake Hańcza (northeastern Poland) using a multi-proxy approach, focusing on early to mid-Holocene climatic and environmental changes. AMS C dating of terrestrial macrofossils and sedimentation rate estimates from occasional varve thickness measurements were used to establish a chronology. The onset of the Holocene at c. 11 600 cal. a BP is marked by the decline of Lateglacial shrub vegetation and a shift from clastic-detrital deposition to an autochthonous sedimentation dominated by biochemical calcite precipitation. Between 10 000 and 9000 cal. a BP, a further environmental and climatic improvement is indicated by the spread of deciduous forests, an increase in lake organic matter and a 1.7‰ rise in the oxygen isotope ratios of both endogenic calcite and ostracod valves. Rising δO values were probably caused by a combination of hydrological and climatic factors. The persistence of relatively cold and dry climate conditions in northeastern Poland during the first one and a half millennia of the Holocene could be related to a regional eastern European atmospheric circulation pattern. Prevailing anticyclonic circulation linked to a high-pressure cell above the retreating Scandinavian Ice Sheet might have blocked the influence of warm and moist Westerlies and attenuated the early Holocene climatic amelioration in the Lake Hańcza region until the final decay of the ice sheet. [ABSTRACT FROM AUTHOR]

During African Humid Period in the Holocene when the summer Intertropical Convergence Zone migrated to its northernmost position, the Qarun Lake in the Faiyum Oasis in Egypt was fed with regular inflows from the Nile River and rainfall brought by the Mediterranean winter circulation. Finely-laminated lake sediments, dated at 8.5–6.7 cal kyr B.P., were examined in terms of lithology, geochemistry, microfossils (diatom, pollen) and magnetic susceptibility. Based on the inferred geographical derivation of pollen, the environmental affiliation of diatom taxa and geochemistry of lake sediments, wind trajectories were distinguished, related to two main atmospheric circulation phases. During the earlier phase (8.50–7.83 cal kyr B.P.) there were northwestern wind trajectories followed by southern ones and during the later phase (7.83–6.70 cal kyr B.P.), the northern winds were followed by northwestern and southern ones. Northwestern and northern winds brought winter rainfall and caused water turbulence in the lake, and the southern winds were associated with regional aridification. This scenario of atmospheric circulation in northeastern Africa extends significantly our understanding of key modes of climatic variability and wind trajectories in the Early to Middle Holocene (Greenlandian to Northgrippian) transition. • Interaction of the Middle Holocene summer monsoon and palaeowesterlies in northeastern Africa • Middle Holocene atmospheric circulation in the eastern Mediterranean • Rain-bearing and dry wind episodes in Egypt in the Middle Holocene • Middle Holocene winter heavy rainfalls in northern Egypt [ABSTRACT FROM AUTHOR]

• Environmental changes at the Allerød/Younger Dryas transition were gradual. • The rate of environment reaction to the cooling depended on local conditions. • An extra-climatic trigger factor activated morphogenetic processes. • Three stages of adaptation to the YD climate were recorded in the biotic sphere. The global climatic trend of the Younger Dryas is clearly registered in the Greenland ice core archives and is printed in terrestrial biogenic deposits. Abiotic landscape components, too, were subjected to changes. The article aims to indicate the dynamics of geomorphological processes activated in response to the cooling and to detect markers of these processes printed within a core of sediments of lacustrine origin and a lake catchment. The article also aims to quantify the extent to which the climate-influenced palaeobotanical record is correlated with local abiotic determinants. The study site lies in an isolated upland location in an old glacial area. The studies include geomorphological and geological analysis of the Younger Dryas palaeolandscape and studies of biogenic deposits of one of the thickest Younger Dryas lacustrine series in Central Poland using biotic proxies and geochemical analysis. A chronology is provided by an age–depth model based on series of radiocarbon datings. The studies demonstrated that for over a thousand years after the beginning of the Younger Dryas (12,653–11,764 modelled cal BP) environmental changes were gradual and thresholds were not exceeded. The morphogenetic processes intensified at the end of the Younger Dryas (11,764–11,533 modelled cal BP) but they also were not catastrophic. The palaeobotanical record is also gradual and reflects the vegetation cover's smooth adaptation to global climate changes, with three clear phases of vegetation development. However, the stability of the landscape system was disturbed, as supported by changes in organic life registered in the palaeolake. Traces of wildefires suggest the factor that triggered abiotic processes and affected the biotic sphere. A comprehensive regional case study has shown the importance of tracking local conditions to modify a global approach and will contribute to a better understanding of the complex environmental impact of the Younger Dryas. [ABSTRACT FROM AUTHOR]

Late glacial and Holocene environmental history of Lake Łukie and its catchment is reconstructed from the lake sediments. This shallow lake is situated in the marshy Polesie region in eastern Poland. Sediments began to accumulate in the lake in the Older Dryas. On the basis of macrofossils, pollen, and Oribatida remains, and with the use of Kohonen’s artificial neural network (self-organising map, SOM), six stages (corresponding to subclusters X 1 , X 2 , X 3 in cluster X, and Y 1 , Y 2 , Y 3 in cluster Y) of the lake history were distinguished, and indicator taxa of each stage were identified from the indicator value (IndVal) index. During the transition period corresponding to the border between X and Y, the ecosystem transformed in the broad sense from the protocratic to mesocratic phase in a 5-point scale transformation of the landscape in the glacial–interglacial cycle. All the steps involved in post-glacial history succession during interglacial cycles include changes in climate, soil, and biotic interactions. Indicator taxa for the subsequent SOM subclusters X 1 , X 2 , and X 3 are associated with the first phase of the protocratic glacial–interglacial cycle. The transformation that occurs on the level of cluster Y (subcluster Y 1 ) is the mesocratic phase (ca. 9000–5000 14 C age BP), which is characterised by high temperatures and development of closed forest (climax forest). Subcluster Y 2 corresponds to the transformation of forest cover during the oligocratic phase (ca. 5000–3000 14 C age BP), which is associated with decreasing forest share and deteriorating soils. Finally, subcluster Y 3 can be associated with the telocratic phase, characterised by the influence of a more oceanic climate (from ca. 2500 14 C age BP) with declining temperatures, higher humidity, and milder seasonal contrasts, which contributed to the development of more open vegetation and infertile soils. This stage also corresponds to an increased human activity and landscape transformation, such as from forests to cornfields and from wetlands to meadows. Interestingly, the currently strictly protected brittle naiad ( Najas minor ) was present in the lake during the Atlantic, Subboreal, and Subatlantic periods; however, this species is not listed as being part of the present vegetation and may have become extinct relatively recently. [ABSTRACT FROM AUTHOR]

In this study we investigate how climate fluctuation in the Late Glacial period influenced the development of a lake and its catchment located in the East European Plain. We analyzed the sediments of the lake for pollen, subfossil Cladocera, macrofossils and chemical composition. We aimed at disentangling: (1) the climate changes and their limno-ecological responses, (2) temperature dynamics with the use of Cladocera-based transfer function (MJT) and macrofossil-based reconstruction of mean minimum July temperature (MMJT), (3) timing of the response of different proxies to environmental changes. The results of multiproxy analyses explicitly suggest that the main driver for changes in aquatic and terrestrial ecosystems as well as geomorphological processes in the catchment was climate. Reconstructed temperatures generally follow the known trends showing the increase at the beginning of the Allerød and decrease at the beginning of the Younger Dryas. However, there are some discrepancies between the two reconstructions as well as between the generally accepted temperature trends in Late Glacial. The timing of the proxy response to climate change differs, the aquatic proxies responding first. [ABSTRACT FROM AUTHOR]