lateglacial vegetation dynamics in the eastern baltic region between 14 500 and 11 400 cal yr bp a complete record since the bolling gi 1e to the holocene abstract this paper discusses a complete record of vegetation history since the bolling gi 1e warming 14 500 cal yr bp up to the holocene in latvia to date this is the only complete record of such age in the eastern baltic area and the northernmost area for which bolling records are present combining pollen evidence pollen accumulation rates par and plant macrofossil data we assess the local and regional vegetation development and we attempt to separate the true lateglacial vegetation signal by removing the obviously redeposited thermophilous pollen however we remove not only their signal we discuss the possibilities of separating the redeposition signal of the so called local lateglacial trees pine and birch by looking at their corrosion and degradation the results show that the bolling warming in the eastern baltic area was a treeless tundra community consisting of the shrubs betula nana dryas octopetala and salix polaris the older dryas cold spell is clearly recognised as a decline in the total concentration of plant macrofossils and pars at between 14 200 and 13 500 cal yr bp at 13 460 cal yr bp the b nana macrofossils disappear and tree birch betula sect albae appears marking the start of tree birch forest the presence of pine forest is confirmed by a variety of macrofossils including bark wood needles and seeds since 13 400 cal yr bp at the same time at which pine stomata are found the first identified pine stomata finds are associated with a pinus par over 3000 grains cm 2 yr 1 and pine macrofossil finds with a pinus par over 4000 grains cm 2 yr 1 during the warmest period of the gi 1a allerod at 13 000 12 700 cal yr bp a pine forest with deciduous trees birch betula pendula and aspen populus tremula developed in the study area the younger dryas gs 1 cooling strongly affected the floral composition in eastern latvia the par of the tree taxa declined abruptly from a maximum value at 12 700 to below 1000 grains cm 2 yr 1 at 12 600 cal yr bp the response time for the pine forest to collapse was 100 years according to the par data pine macrofossils disappear simultaneously with the pollen signal at 12 600 cal yr bp yet occasional pinus stomata are recorded throughout the younger dryas gs 1 the landscape was treeless shrub tundra again with d octopetala s polaris b nana and juniperus present picea is introduced in the region within the cold younger dryas and is represented by stomata 12 400 12 200 cal yr bp needles seeds and wood since 12 050 cal yr bp up to the holocene the pleistocene holocene boundary at 11 650 cal yr bp is marked by changes both in vegetation composition and sediment type the organic rich gyttja accumulated instead of silts and clays and the start of the holocene warm period permitted forest re expansion in eastern latvia

applications of organic geochemistry to paleolimnological reconstructions a summary of examples from the laurentian great lakes the organic matter content of lake sediments contains information that helps to reconstruct past environmental conditions evaluate histories of climate change and assess impacts of humans on local ecosystems the elemental isotopic and molecular compositions of organic matter buried in sediment provide evidence of the biota that have lived in a lake and its catchment area and they serve as proxies of organic matter delivery and accumulation sedimentary records from the north american great lakes provide examples of applications of organic geochemistry to paleolimnological reconstructions the records of these lakes date from retreat of the laurentide ice sheet around 12 ka include the mid holocene hypsithermal and show consequences of recent human changes low corg ntotal ratios indicate that most of the sediment organic matter in the great lakes is from algal production yet changes in biomarker molecule compositions also show that varying amounts of land plant organic matter have been delivered to the lakes elevated algal productivity that accompanies nutrient enrichments of lake waters is recorded as excursions to less negative 13c values in the organic matter of sediments that were deposited in the 1960s and 1970s increased organic carbon mass accumulation rates mirror the isotopic excursions in most parts of the great lakes accumulations of petroleum residues and pyrogenic polycyclic aromatic hydrocarbons in sediments identify fluvial and eolian delivery of organic matter components to different parts of the great lakes emerging applications of multiple and novel organic geochemical proxies to paleolimnological reconstructions are promising yet some potentially important measurements remain underutilized

a high resolution record of climate variability and landscape response from kettle lake northern great plains north america abstract a decadal scale multiproxy record of minerals pollen and charcoal from kettle lake north dakota provides a high resolution record of climate and vegetation change spanning the entire holocene from the northern great plains ngp in north america the chronology is established by over 50 ams radiocarbon dates this record exhibits millennial scale trends evident in other lower resolution studies but with much more detail on short term climate variability and on the rapidity and timing of major climatic shifts as a proxy for precipitation we utilize the rate of endogenic carbonate sedimentation which depends on groundwater inflow which in turn depends on precipitation independent cluster analyses of mineral and pollen data reveal major holocene mode shifts at 10 73 ka ka cal yr bp 9 25 ka and 4 44 ka the early holocene 11 7 9 25 ka was generally wet with perhaps a trend to higher evaporation associated with warming temperatures a switch from calcite to aragonite deposition associated with a severe but brief drought occurred at 10 73 ka from 10 73 ka to 9 25 ka climate was generally humid but punctuated at 100 300 yr intervals by brief droughts including the most severe drought of the entire holocene at 9 25 ka this event was coeval with the 9 3 9 2 ka event in the greenland ice cores and observed at a number of sites worldwide in contrast the prominent 8 2 ka event in greenland is not remarkable at kettle lake the prominence of the 9 25 event locally in the ngp may be due to a major drawdown and northward retreat of lake agassiz at this time reducing its mesoclimatic effect on the ngp and thrusting the region into an insolation controlled regime the mid holocene 9 25 4 44 ka was characterized by great variability in moisture on a multi decadal scale with severe droughts alternating with more humid periods the high abundance of the weedy but drought intolerant ambrosia generally during the mid holocene and specifically during the multi decadal drought periods is seemingly paradoxical but can be explained by high interannual variability of moisture overlaid on the multi decadal variability the late holocene 4 44 ka present was also characterized by multi decadal variability in moisture but was generally wetter than the mid holocene and the magnitude of variability was less the trends in wet dry mineral pollen and charcoal proxies were similar to the mid holocene but late holocene mineral pollen assemblages are distinct from mid holocene the shift to wetter climate in the late holocene was more gradual than the abrupt shift to arid conditions 9 25 ka which may explain the asymmetric retreat and readvance of forest along the eastern margin of the ngp precipitation variations in the ngp have been linked with pacific and atlantic sea surface temperatures and mid holocene drought in the ngp has been linked with sustained la nina like conditions in the pacific these linkages may explain the decadal and millennial scale variations seen in the ngp but cause of the prominent century scale variations remains elusive

the effects of channels and shoals on exchange between the chesapeake bay and the adjacent ocean the role of bathymetric changes in determining the transport of water and salt in the lower chesapeake bay lcb was investigated using high resolution acoustic doppler current profiler adcp and conductivity temperature depth profiles a cross channel transect was repeated eight times during neap tides on october 6 7 1993 which illustrated the lateral structure of the longitudinal and transverse flow fields and the intratidal variations in the flow structure across the lcb amplitude and phase of the m2 tidal component as well as the mean flow velocity were calculated using least squares fitting at every point of a uniform grid obtained from the adcp data the results differ from the classical two layer pattern of estuarine circulation modified by coriolis effects but are consistent with recent hydrographic observations semidiurnal flow was highest over the navigational channels and lateral gradients were strongest in regions of sharp bathymetric changes the phase lag of the semidiurnal flow also showed lateral and vertical gradients that represented advances at the bottom with respect to the surface and over the shoals in relation to the channels the section of the water column measured indicated a mean outflow of 0 7 104 m3 s and a mean inflow of 1 3 104 m3 s the apparent gain of water by the estuary during the period of observation can be explained by meteorologically forced net barotropic inflow the depth averaged mean longitudinal flow consisted of inflow in the navigational channels and outflow over the shoals the mean transverse flow showed near surface convergence over the channels we propose a possible explanation for the observed flow and density structure as follows the barotropic and baroclinic forcing interact with the bathymetry to extend the inflow from the bottom to the surface thereby inducing a transverse circulation that yields near surface convergence over the channels

cold event at 8200 yr b p recorded in annually laminated lake sediments in eastern europe a quantitative annual mean temperature reconstruction from an annually laminated lake sediment sequence in estonia eastern europe shows a distinct cold period at 8400 8080 yr b p before a d 2000 the timing is consistent with that seen in the greenland ice core data and various high resolution records from western europe during maximal cooling at 8250 8150 yr b p the annual mean temperature in estonia was 2 0 c colder than prior to and 3 0 c colder than after the cooling the pollen stratigraphic and sedimentological data suggest especially cold and snowy winter conditions the duration and amplitude of the cold event agree with the modeled impact of a sudden freshening of the north atlantic surface water and subsequent perturbation of the thermohaline circulation provided that the cold event was caused by a pulse of freshwater from the melting laurentide ice sheet to the north atlantic the results indicate a strong teleconnection between the north atlantic oceanic forcing and the east european climate at least up to long 26 e mediated probably by the changing intensity of the zonal atmospheric circulation

airborne lidar in support of geomorphological and hydraulic modelling this paper considers the application of airborne laser altimetry lidar to the provision of elevation data at accuracies and spatial densities commensurate with the current generation of high resolution hydraulic models three sets of issues are addressed with reference to a telemac 2d model of a morphologically complex estuary in eastern england first the quality of airborne lidar data is assessed via multiscale calibration against surveyed sections and supplementary control points second image processing techniques are used for i identification of multiple regions of interest within large lidar mosaics ii subregional infilling of voids left by data drop outs iii filtering and subsampling to match topographic information content with model resolution and the density of the computational mesh third the implications of improved terrain data are considered with reference to the estimation of elevations and potential tidal volumes for a number of discrete flood compartments and the modelling of hypothetical inundation scenarios after minor offset correction to ensure registration with local benchmarks the quality of lidar elevation data within a 12 km x 4 kin coverage is found to be consistent with the published specification 0 10 to 0 15 m image processing tools provide an efficient means of managing information content and interfacing this with the gis based functionality of the preprocessing software used in conjunction with the hydraulic model the accuracy and spatial resolution of the lidar data allow the identification of subtle but important topographic variations between adjacent flood compartments in many cases differences in model results obtained using these data relative to previously estimated average flood compartment elevations are small importantly however lidar provides topographic information at an accuracy and resolution close to the present limits of model representation reliable representation of form allows the modeller to concentrate on the physical aspects of model parameterization whilst minimizing the conflation of parameter effects with those of poorly constrained geometric representation copyright c 2003 john wiley sons ltd

a two dimensional analytic tidal model for a narrow estuary of arbitrary lateral depth variation the intratidal motion an innovative method is introduced to solve a two dimensional depth averaged analytic model for narrow estuaries or tidal channels with arbitrary lateral depth variations the solution is valid if the lateral variation of the amplitude of tidal elevation a is small i e a a where a is the amplitude of the tidal elevation this assumption is supported by a 60 day observation of elevation in the james river estuary using pressure sensors at both sides of a cross section of the estuary the error introduced by the solution is of the order of a a which has a maximum of 5 in the james river estuary the propagation of the tidal wave elevation is therefore essentially one dimensional along the estuary regardless of the depth distribution whereas tidal velocity has a strong transverse shear and is three dimensional in general dozens of depth functions in six groups of various forms are used to calculate the solution the tidal velocity is highly correlated with the bathymetry the largest amplitude of the along channel velocity is in the deepest water the phase of the along channel velocity in the shallow water leads that in deep water causing a delay in time of flood or ebb in the deep water the transverse velocity is generally small in the middle of a channel but reaches its maximum over the edges of bottom slopes the depth function has a significant effect on the ellipticity and the sense of rotation of the tidal ellipses by fitting the observed phase of semidiurnal tide in the james river estuary to the phase of the momentum equation we have obtained optimal values of the drag coefficient 1 5 10 3 and 1 8 10 3 for the spring and neap tides respectively then we apply these values of the drag coefficient and the model to the james river estuary using the real bathymetry results show remarkable agreement between the observations and the model along the transects for both spring and neap tides the cross channel phase difference of the along channel velocity between the channel and the shoal is found to be 1 hour a value consistent with that from the model the model estimated lateral variation of elevation is 2 5 of the tidal amplitude which is slightly smaller than the observed value

sediment transport modeling review current and future developments the use of computational models for solving sediment transport and fate problems is relatively recent compared with the use of physical models several considerations govern the choice between physical and computational models namely the nature of the problem that needs to be solved the available resources and the overall cost associated with the problem solution in some specific problems a combination of physical and computational models can be used to obtain a better understanding of the processes under investigation de vries 1973 using computational hydrodynamic sediment transport models in general involves the numerical solution of one or more of the governing differential equations of continuity momentum and energy of fluid along with the differential equation for sediment continuity an advantage of computational models is that they can be adapted to different physical domains more easily than physical models which are typically constructed to represent site specific conditions another advantage of computational models is that they are not subject to distortion effects of physical models when a solution can be obtained for the same flow conditions identical reynolds and froude numbers same length scale in the three directions etc as those present in the field with the rapid developments in numerical methods for fluid mechanics computational modeling has become an attractive tool for studying flow sediment transport and associated pollutant fate processes in such different environments as rivers lakes and coastal areas representative processes in these environments include bed aggradation and degradation bank failure local scour around structures formation of river bends fining coarsening and armoring of streambeds transport of point source and nonpoint

effect of sediment transport boundary conditions on the numerical modeling of bed morphodynamics abstractexperimental sediment transport and river morphologic studies in laboratory flumes can use two sediment supply methods an imposed feed at the upstream end or a recirculation of sediment f

two dimensional hydraulic flood modelling using a finite element mesh decomposed according to vegetation and topographic features derived from airborne scanning laser altimetry airborne scanning laser altimetry lidar is an important new data source that can provide two dimensional river flood models with spatially distributed floodplain topography for model bathymetry together with vegetation heights for parameterization of model friction methods are described for improving such models by decomposing the model s finite element mesh to reflect floodplain vegetation features such as hedges and trees having different frictional properties to their surroundings and significant floodplain topographic features having high height curvatures the decomposition is achieved using an image segmentation system that converts the lidar height image into separate images of surface topography and vegetation height at each point the vegetation height map is used to estimate a friction factor at each mesh node the spatially distributed friction model has the advantage that it is physically based and removes the need for a model calibration exercise in which free parameters specifying friction in the channel and floodplain are adjusted to achieve best fit between modelled and observed flood extents the scheme was tested in a modelling study of a flood that occurred on the river severn uk in 1998 a satellite synthetic aperture radar image of flood extent was used to validate the model predictions the simulated hydraulics using the decomposed mesh gave a better representation of the observed flood extent than the more simplistic but computationally efficient approach of sampling topography and vegetation friction factors on to larger floodplain elements in an undecomposed mesh as well as the traditional approach using no lidar derived data but simply using a constant floodplain friction factor use of the decomposed mesh also allowed velocity variations to be predicted in the neighbourhood of vegetation features such as hedges these variations could be of use in predicting localized erosion and deposition patterns that might result in the event of a flood copyright 2003 john wiley sons ltd

impact of a lisbon type tsunami on the u k coastline and the implications for tsunami propagation over broad continental shelves 1 we investigate the propagation of tsunamis toward the european shelf break using six different initial conditions based on the 1755 lisbon earthquake in order to assess the hazard to this region only one of our source models an assumed earthquake magnitude of 8 7 mw with a zonal fault orientation resulted in significant wave heights at the u k coastline because of wave spreading only a fraction of the tsunami energy from such an event reaches the northwest european shelf which itself provides a further buffer through reflection and frictional dissipation however we found significant local reamplification due to wave interactions and resonance on the continental shelf the maximum elevations obtained were comparable to severe winter storm conditions but with extreme local variability in the tsunami amplitude our results suggest that the impact of any repeat of this event would be very sensitive to the precise location and orientation of the source deformation as well as by complex topographic interactions on the shelf the uncertainties arising from the combination of source orientation and bathymetric interaction suggest that any assessment of risk for places where tsunamis are likely should consider a large ensemble of initial conditions

accumulation of metals and changes in composition of freshwater lake organic sediments during the holocene abstract the distribution of metals in the strata of sediments deposited in the freshwater environment formed during the holocene in the territory of latvia has been studied rather insufficiently considering the large volume of accumulated organic matter in sediments studies on the content of metallic elements in sediments can help to determine the peculiarities of the metal accumulation process in limnic systems and the biogeochemical cycling of metals lake pilvelis which is located in the eastern part of latvia the northern part of europe was selected as the main study site lake pilvelis is a small lake of a glacial origin and 90 of its depression is filled with organic rich sediments the development stages of lake pilvelis since circa 10 000 cal bp are described in detail via reconstruction of the holocene palaeoenvironmental conditions using multi proxy sedimentary records the elemental composition and content of metallic elements in sapropel are analysed with the main objectives of characterising the accumulation rate of metals in the full profile of sapropel and determining the anthropogenic impact depending on the evolution of the lake and the genesis of sediment organic matter the correlation among the components characterising sediments such as sapropel and metallic elements revealed that the elemental distribution could be divided into three main groups according to the content of the elements associated with organic compounds e g for zn and mn and mineral compounds for ni co cr k fe mg and cu ni and co are partly associated with mineral compounds and partly associated with carbonates a principal component analysis revealed the main factors indicating the origin of metallic elements and the accumulation tendencies of metals in sediment layers the input of the mineral matter the characteristics of organic matter and human impact the content of metallic elements in sapropel from lake pilvelis is mainly affected by the composition of mineral matter not by the size of the particles

peat stratigraphy and changes in peat formation during the holocene in latvia mires represented by raised bogs fens and transitional mires cover approximately 10 of latvia they started to form towards the end of the last glacial period and the beginning of the holocene under varying geological and palaeoecological conditions the aim of the study was to evaluate how the results of peat palaeobotanical investigation can reveal changes in the conditions of peat formation and allow a subdivision to be made of the holocene according to the scheme suggested by the intimate group walker et al 2012 records from 21 mires have been evaluated to find evidence of changes in mire vegetation and peat formation and to discover whether these records define boundaries allowing the holocene deposits to be subdivided into the early holocene middle holocene or the holocene thermal maximum htm and the late holocene information from earlier studies and data from recent investigations are used for the revision of peat stratigraphy revision peat accumulation and fen formation during the early holocene took place in the oldest mires which started to develop by the infilling of shallow lake depressions during the second part of the early holocene before 9500 cal yr bp the climate became warmer and less humid and the eutrophic plant species were gradually replaced by mesotrophic species at the end of the early holocene parts of fens gradually turned to transitional mires and the first layers of raised bog peat started to form the boundary between the early and middle holocene or the htm can be established at the interval of 8100 to 8000 cal yr bp based on sharp changes in peat formation conditions the further development of raised bogs and fens including coastal areas where ground paludification and bog development in the depressions caused by groundwater rise because of water level rise due to transgression of the baltic sea littorina sea stage took place the boundary between the htm and the late holocene in this study is established at 4200 cal yr bp as suggested by the intimate group during the late holocene the bog plant phytocenoses were formed essentially of sphagnum and cotton grass which on decay produced slightly decomposed sphagnum magellanicum sphagnum fuscum and sphagnum cotton grass peat an intensive accumulation of peat occurred all over followed by intensive development of bog cupolas after the regression of the littorina sea stage of the baltic sea terrestrialisation processes and peat formation were initiated in the former lagoonal areas the interdune mires started to form in the north western coastal area of latvia before 3500 3000 cal yr bp this study shows that pollen nonpollen and the botanical composition of peat in mire deposits together with 14c dating can yield valuable information about environmental conditions during peat accumulation and provide insights into peat stratigraphy which help to understand the development of mires and mire ecosystems the findings of this study and comparison with earlier work enable us to conclude that peat stratigraphy and the subdivision of the holocene in latvia can generally use the scheme suggested by the intimate group walker et al 2012 however the local peculiarities of mires should also be taken in account

examination of generation mechanisms for an english channel meteotsunami combining observations and modeling abstracton the morning of 23 june 2016 a 0 70 m meteotsunami was observed in the english channel between the united kingdom and france this wave was measured by several tide gauges and coincided

structure and origin of holocene cold events abstract the present interglacial the holocene spans the period of the last 11 700 years it has sustained the growth and development of modern society the millennial scale decreasing solar insolation in the northern hemisphere summer lead to northern hemisphere cooling a southern shift of the intertropical convergence zone itcz and a weakening of the northern hemisphere summer monsoon systems on the multidecadal to multicentury scale periods of more stable and warmer climate were interrupted by several cold relapses at least in the northern hemisphere extra tropical area based on carefully selected 10 000 year long time series of temperature and humidity precipitation as well as reconstructions of glacier advances the spatiotemporal pattern of six cold relapses during the last 10 000 years was analysed and presented in form of a holocene climate atlas hoclat see http www oeschger unibe ch research projects holocene atlas a clear cyclicity was not found and the spatiotemporal variability of temperature and humidity precipitation during the six specific cold events 8200 6300 4700 2700 1550 and 550 years bp was very high different dynamical processes such as meltwater flux into the north atlantic low solar activity explosive volcanic eruptions and fluctuations of the thermohaline circulation likely played a major role in addition internal dynamics in the north atlantic and pacific area including their complex interaction were likely involved

formal subdivision of the holocene series epoch a discussion paper by a working group of intimate integration of ice core marine and terrestrial records and the subcommission on quaternary stratigraphy international commission on stratigraphy this discussion paper by a working group of intimate integration of ice core marine and terrestrial records and the subcommision on quaternary stratigraphy sqs of the international commission on stratigraphy ics considers the prospects for a formal subdivision of the holocene series epoch although previous attempts to subdivide the holocene have proved inconclusive recent developments in quaternary stratigraphy notably the definition of the pleistocene holocene boundary and the emergence of formal subdivisions of the pleistocene series epoch mean that it may be timely to revisit this matter the quaternary literature reveals a widespread but variable informal usage of a tripartite division of the holocene early middle or mid and late and we argue that this de facto subdivision should now be formalized to ensure consistency in stratigraphic terminology we propose an early middle holocene boundary at 8200 a bp and a middle late holocene boundary at 4200 a bp each of which is linked to a global stratotype section and point gssp should the proposal find a broad measure of support from the quaternary community a submission will be made to the international union of geological sciences iugs via the sqs and the ics for formal ratification of this subdivision of the holocene series epoch copyright 2012 john wiley sons ltd

the oleaginous botryococcus from the triassic yanchang formation in ordos basin northwestern china morphology and its paleoenvironmental significance high abundance but rather low diversity algal fossils were found in the hydrocarbon source rocks of the ch 7 2 ch 7 3 section triassic yanchang formation in the xifeng area of southwest ordos basin which are mainly composed of prolific leiosphaeridia and botryococcus botryococcus colonies are of various forms the majority is nubbly with some of cluster and cotton shape the nubbly colonies appear globular cordiform ternate petal obtuse triangle chrysanthemum shape and so on most botryococcus are saffron or brown and are frequently covered with clay under transmission microscope and shows strong yellow and light brown under fluorescence microscope botryococcus could live in freshwater and brackish water the botryococcus colonies that lived in fresh water are small with small single cells arranged radially with undulant or indented edges the botryococcus colonies that lived in brackish water are bigger with larger single cells arranged irregularly with slippery contours the most of botryococcus are discovered from the organic rich argillaceous sediment with abundant pyrites in the semi and deep lake facies and shows they were preserved in low energy reducing environments taphonomic characteristics of various microfossils and the present of pediastrum in the phytoplankton flora indicate that they are in situ or near burial the lake area of the ordos basin was gradually expanding and reaching its most extensive flood surface in the ch 7 of yanchang formation interval during the middle and late triassic with warm climate plentiful rainfall and luxuriant vegetation as determined by the environmental analysis with botryococcus in xifeng area the presence of two ecological types of botryococcus indicates that the salinity of lake water was fluctuating in the ch 7 interval the occurrence of symbiotic acritarchs and geochemical salinity indices show that the ordos lake was a typical fresh water lake which was gradually desalted and its salinity fluctuation was narrow during the mid later triassic the ecological type of the palynological flora discovered from the ch 7 to ch 8 in xifeng area is similar to that from the fuxian lake with abundant botryococcus in the yungui plateau of china these findings imply that the ordos basin was in a lower latitude area of temperate to subtropical climate during the middle and late triassic

sedimentary cladocera as indicators of past water level changes in shallow northern lakes the usability of subfossil cladocera assemblages in reconstructing long term changes in lake level was examined by testing the relationship between cladocera based planktonic littoral p l ratio and water level inference model in a surface sediment dataset and in a 2000 yr sediment record in finland the relationships between measured and inferred water levels and p l ratios were significant in the dataset implying that littoral taxa are primarily deposited in shallow littoral areas while planktonic cladocerans accumulate abundantly mainly in deepwater locations the 2000 yr water level reconstructions based on the water level inference model and p l ratio corresponded closely with each other and with a previously available midge inferred water level reconstruction from the same core showing a period of lower water level around ad 300 1000 and suggesting that the methods are valid for paleolimnological and climatological use

environmental changes of a shallow kettle lake catchment in a young glacial landscape sumowskie lake catchment north central poland abstract on the basis of detailed analysis sedimentological palynological macroremains geochemical and gis analysis the development of the sumowskie paleolake was reconstructed obtained results led to distinguish three main stages of the evolution of the basin and its catchment during the late glacial and the holocene the lacustrine stage the lake overgrowth stage and the post lacustrine stage study site is located in the western part of the brodnica lakeland north eastern poland within the former sumowskie lake bottom multidisciplinary research was conducted for two cores sedimentological palynological plant macroremains sum a 149 cm and sum c 51 cm and the soil profile sum 3 sedimentological geochemical gis analyses land cover and water level changes were carried out for the nowadays sumowskie lakes catchment it was confirmed that climate was the most important factor influencing the evolution of the lake and its surrounding although the role of this factor decreased in the neo holocene period in favor of rapidly growing human impact changes of the water level were much more abrupt and lasted longer e g 9500 5000 bp hiatus caused by the water level decrease than in other described basins of the region due to the specific geomorphologic situation shallow kettle basins could alternately act as lakes and wetlands as they are well spread in the young glacial area the strong influence of this abrupt and long term events should be reconsidered

reconstruction of the holocene palaeoenvironmental conditions accordingly to the multiproxy sedimentary records from lake pilvelis latvia abstract reconstruction of the holocene palaeoenvironment conditions in southeastern latvia is based on multiproxy records from lake pilvelis pollen plant macrofossil and microfossil analysis loss on ignition loi measurements 14 c dating humic substances content humification index and elemental composition of gyttja organic mass the data complex obtained in the result of multiproxy studies of sediments in lake pilvelis indicates significant changes in the depositional environment during the lake development data from lake pilvelis show that the start of organic rich sediments formation before approximately 9750 cal bp when birch pine forest dominated in the surrounding landscape diagrams and data sets show six remarkable comparatively short cooling periods during the holocene which are related to changes in temperature and water level and influenced values and variability of remains the investigation recognized the 8 4 ka bp and 4 6 ka bp cold events while other cooling events can be recognised conditionally during the events of 4 0 ka bp the water level decreased extremely and the climate was probably drier indicated by the comparison of records from lake pilvelis mazais svetinu bog and lake razna a comparison of pollen data from lake pilvelis with lake kurjanovas mazais svetinu bog and lake razna shows some similarities revealing features of cooler climatic conditions approximately at the time characterised by an increase of betula and herb pollen

lateglacial and early holocene environmental changes in northeastern lithuania abstract multiproxy data pollen diatoms plant macrofossils 14c and loss on ignition measurements obtained from two cores petrasi nai and juodonys were used to reconstruct the pattern of lateglacial and early holocene environmental changes in ne lithuania the flourishing of open pinus forest and presence of light demanding taxa on poor unstable soils surrounding shallow water basins have been recorded from about 13 100 13 000 cal bp to 12 600 cal bp in the study area after 13 000 cal bp expansion of betula dominated vegetation and increased abundance of cold tolerant plants together with a simultaneous drop of water temperature indicates a short climate deterioration tentatively correlated with the gerzensee oscillation a sudden reduction of the forest cover and extensive development of grass herb dominated landscape is suggestive of a regional expression of the younger dryas cooling dated to 12 600 11 500 cal bp climate aridification resulted in a progressive lowering of the water level and subsequent overgrowth of the basins early holocene vegetation changes show a pattern of forest development with dominance of spruce shortly after 11 500 cal bp based on palynological evidence and the presence of plant macrofossils seeds and needles early holocene immigration of picea sp to juodonys 9410 310 bp vs 1433 and petrasi nai 9420 65 bp tua 6177 df2471 is indicated further development of the vegetation cover indicates multiple flourishing of predominant open birch vegetation subsequently followed by pine spruce forest development caused by preboreal climate instability the most prominent climate shift e g drop of the temperature and humidity recorded shortly before 11 100 cal bp has been correlated with the preboreal oscillation bjorck s rundgren m ingolfsson o funder s 1997 the preboreal oscillation around the nordic seas terrestrial and lacustrine responces journal of quaternary science 12 455 465 expansion of birch predominant forest around shallow water basins has been identified during the late preboreal after 11 100 cal bp

the kettle hole mire as archives of postglacial changes in biogenic sedimentation tuchola forest north central poland abstract kettle holes are a circular shape product of ice decay and thus are strongly linked with young glacial landscapes once glaciation terminates these holes transform either into wetland and lakes or occasionally into kettle hole mires since an entire sediment sequence preserve in the kettle holes these provide an excellent settings to exploit any sensitive paleoenvironmental changes here the kettle hole mire located onto the brda river outwash plain tuchola forest is explored towards a better understanding of local and global environmental trends in the late glacial present day time frame to fulfill this multi proxy study as geochemical palynological and macrofossils analyses along with the radiocarbon dating are used therefore this study allows to distinguish five phases of steep environmental gradients in the investigated mire as follows 1 paludification after glaciation when dead ice melted and long term permafrost was degraded 2 lake started to disappear in the late glacial followed by a rich vegetation in the first part of the holocene 3 vegetation encroachment onto the lake in the first part of the holocene which consequently turned into an peat bog 4 the late holocene peat bog with a limited human influence and finally 5 the peat bog with a major human impact along with acidification as related to sandy underlying sediments leaching of calcium carbonate recharge from precipitation and pine monoculture as additionally apparent from this small ecosystem both local character of substrate sediments morphology of the area rate of permafrost melting climate conditions and human activity and regional climate changes and human activity are detectable nevertheless the record of these changes is sometimes unclear

holocene annual mean temperature changes in estonia and their relationship to solar insolation and atmospheric circulation patterns abstract we reconstructed annual mean temperature tann trends from three radiocarbon dated holocene pollen stratigraphies from lake sediments in estonia northern europe the reconstructions were carried out using a north european pollen climate calibration model based on weighted averaging partial least squares regression the cross validated prediction error of the model is 0 89 c and the coefficient of determination between observed modern tann values and those predicted by the model is 0 88 in the reconstruction the holocene thermal maximum htm is distinguishable at 8000 4500 cal yr b p with the expansion of thermophilous tree species and tann on average 2 5 c higher than at present the pollen stratigraphical data reflect progressively warmer and drier summers during the htm analogously with the modern decadal scale climatic variability in north europe we interpret this as an indication of increasing climatic continentality due to the intensification of anticyclonic circulation and meridional air flow post htm cooling started abruptly at around 4500 cal yr b p all three reconstructions show a transient ca 300 years cooling of 1 5 2 0 c at 8600 8000 cal yr b p we tentatively correlate this cold event with the north atlantic 8 2 ka event at 8400 8000 cal yr b p provided that the 8 2 ka event was caused by freshening of the north atlantic surface water our data provide evidence of the climatic and vegetational responsiveness of the boundary of the temperate and boreal zones to the weakening of the north atlantic thermohaline circulation and the zonal energy transport over europe no other cold events of comparable magnitude are indicated during the last 8000 years