correlation of fluctuations in cladoceran planktonic littoral ratio between three cores from a small lake in southern finland holocene water level changes the main aim of the study was to test the cladoceran planktonic littoral p l method in holocene lake level studies with three cores from a small lake iso lehmalampi 60 21 n 24 36 e in south

the effect of geomorphological setting on holocene lake sediment variability northern swedish lapland the effect of geomorphological setting on holocene lake sediment variability northern swedish lapland

internal waves in a small reservoir horizontally distributed temperature time series recorded in the thermocline of a small reservoir during autumn are used to identify both basin scale and higher frequency internal waves stationary and nonstationary spectral analyses are used to identify dominant frequencies the horizontal distribution of data allows a map of the basin scale wave energy to be determined three layer normal mode modeling incorporating damping emulates the basin scale behavior well this provides estimates of velocity shear and hence the internal stability the nonstationary frequency analysis identifies times of high frequency internal wave activity wave periods of 2 10 min this is definitely linked to the basin scale wave driven shear and hence to deceases in stability estimates of dissipation for the thermocline and hypolimnion are 3 10 8 and 6 10 9 m 2 s 3 respectively the inferred variability in the hypolimnetic value is demonstrated

annual climate variability in the holocene interpreting the message of ancient trees abstract over vast areas of the world s landmasses where climate beats out a strong seasonal rhythm tree growth keeps unerring time in their rings trees record many climate melodies played in different places and different eras recent years have seen a consolidation and expansion of tree ring sample collections across the traditional research areas of north america and europe and the start of major developments in many new areas of eurasia south america and australasia from such collections are produced networks of precisely dated chronologies records of various aspects of tree growth registered continuously year by year across many centuries their sensitivities to different climate parameters are now translated into ever more detailed histories of temperature and moisture variability across expanding dimensions of time and space with their extensive coverage high temporal resolution and rigid dating control dendroclimatic reconstructions contribute significantly to our knowledge of late holocene climates most importantly on timescales ranging from 1 to 100 years in special areas of the world where trees live for thousands of years or where subfossil remnants of long dead specimens are preserved work building chronologies covering many millennia continues apace very recently trees have provided important new information about major modes of general circulation dynamics linked to the el nino southern oscillation and the north atlantic oscillation and about the effect of large volcanic eruptions as for assessing the significance of 20th century global warming the evidence from dendroclimatology in general supports the notion that the last 100 years have been unusually warm at least within a context of the last two millennia however this evidence should not be considered equivocal the activities of humans may well be impacting on the natural growth of trees in different ways making the task of isolating a clear climate message subtly difficult

chironomid response to environmental drivers during the holocene in a shallow treeline lake in northwestern fennoscandia the significance of different environmental drivers for the chironomid compositional changes during the holocene was assessed using partial redundancy analysis these drivers included pollen inferred mean july air temperature vegetation cover as pollen percentages diatom inferred water ph and total organic carbon toc and sediment properties as loss on iginition loi variance partitioning showed that on the holocene timescale chironomid assemblages were significantly responding to changes in betula percentages this is explained by the co occurring response of chironomids to the holocene climatic development which has also been responsible for the development of vegetation in the catchment however during the very early holocene period from 10 500 cal yr bp to 8300 cal yr bp chironomids were responding more directly to the changes in water quality ie ph during the latter part of the holocene no environmental variable appeared to be significant in explaining the variation in chironomid assemblages this may be due to the underestimation of the actual water toc by the diatom based toc model however for the latter part of the holocene from 5000 cal yr bp to the present the importance of limnological changes attributed to the development of marginal mires on the midges is evident our study shows that factors other than climate may have had more direct influence on the chironomid abundances at certain time periods although these factors are probably indirectly connected to climate through catchment processes more understanding of the catchment mediated climate effects on lake ecology and chironomids in high latitudes is needed in addition to careful site selection in order to better understand the environmental reconstructions

neoglacial activity in finland dating the evidence from glaciolacustrine sediment sequences in the halti ridnitsohkka region palaeomagnetic dating of sediment sequences from lakes pihtsusjarvi and haltijarvi in enontekio northwestern finnish lapland provided a chronology for a study of the palaeohydrological and glacier history of the haltiridnits yohkka fells area both sequences exhibited a stable primary component of the nrm direction allowing a comparison of the secular variation records with the chronology of lake nautajarvi reference curves nrm to provide a chronological framework for the present study the basins of lakes pihtsusjarvi and haltijarvi were formed 10 500 and 5500 cal bp respectively minerogenic layers found from studied lake pihtsusjarvi sequences provided evidence of postglacial activity of the halti fell valley glacier the results indicated that the halti glacier was active soon after the continental ice sheet had retreated from the area at around 10 000 9000 cal bp during which time the kovdajohka valley terminal and recessional moraines were formed this was followed by a holocene thermal maximum htm in northern fennoscandia which was interrupted by climate cooling at around 6000 cal bp the basal age of the lake haltijarvi sediment core and lake pihtsusjarvi sediment stratigraphy indicated minor short term neoglacial activity in the halti fell vicinity between c 6000 and 5500 cal bp

anatomy of turbulence in thermally stratified lakes turbulence within the thermocline of two thermally stratified lakes lake biwa japan and lake kinneret israel was investigated using a portable flux profiler this instrument provided high resolution profiles of temperature conductivity and two components of velocity within a measuring volume of approximately 8 mm 3 each data profile was segmented into statistically stationary segments a range of properties of the turbulence including direct estimates of the vertical mass flux were then calculated for each segment it was found that turbulence in the thermocline was generally patchy but within a patch dissipation levels were relatively high the turbulent motions were found to be fine grained with small thorpe scales and a large skewness of the distribution of the displacement scale this is distinct to that found in the ocean where shear instability produces large overturns the measurement showed that the net vertical mass flux in the thermocline was negligible and less than that predicted by osborn 1980 this is explained by noting that the net buoyancy flux consisted of two opposing parts a down gradient irreversible flux due to turbulent mixing and an up gradient reversible flux due to restratification that often cancel each other within a segment the low measured net buoyancy flux within the interior of the lakes suggested that other processes such as gravitational adjustments and benthic boundary layer processes should be responsible for the basin averaged vertical transport in these lakes

stability and meromixis in a water filled mine pit a field experiment examined stability and stratification in a disused mine fit filled with 1 75 x lo7 m3 of water vertical profiles of conductivity and temperature indicated that due to substantial chemical stratification spring and autumn overturn did not penetrate to the base of the pit although parameterization indicated that double diffusion should be expected we found only circumstantial evidence of associated step structure the available data suggest that groundwater inflow created a warm salty pool of water at the base of the water column giving the appearance of a meromictic structure with a monimolimnion however this pool was noi a consistent feature suggesting both a variable inflow and significant diffusion rates from the temperature data estimates indicated that hypolimnetic vertical eddy diffusivity varied between 1 x 10e7 and 5 x lo m s l the observations identify short term relatively energetic internal wave events that may have a significant impact on this value the present study is useful in two ways first it shows how pit lakes form a natural laboratory fcr a range of processes and second it illustrates how these processes relate to diffusion paranieterization it is clear that reliable parameterization is vital for long term modeling required for prediction of water quality over decadal timescales with the closure of an open cut mining operation come the dual problems of rehabilitation of the mine pit and containment of deleterious material generated by the mine during its life in many cases the pit fills with water either naturally or through mine activities thus an artificial lake of moderate volume is created davis and ashenberg 1989 characterization of the transport processes within the water column is important for two reasons first the pit is likely to contain hazardous levels of dissolved metals and second if vertical transport rates are low then the pit may prove suitable as a storage location for hazardous material water filled mine pit lakes pit lakes have received consideration in the literature but with a biological or geochemical emphasis e g klapper and schultz 1995 crater lakes are the natural system most similar to these artificial water bodies martin 1985 macintyre and melack 1985 pit lakes are unique for several reasons they are often deep relative to natural lakes of similar surface area they have high surrounding walls that often generate a microclimate different to that outside the pit they typically have very thin sediment layers they may undergo substantial and rapid changes in water level and they are likely to contain significant concentrations of dissolved material the final point is important if the dissolved material is environmentally harmful or if it leads to meromixis with these departures from what might be associated with typical natural lakes

origin and evolution of the greisenizing fluid at the east kemptville tin deposit nova scotia canada the process responsible for greisen hosted tin mineralization at east kemptville was investigated using petrographic chemical and fluid inclusion analyses of samples from a single deep drill hole 90 1 in the western part of the deposit baby zone based on their trace element chemistry the greisens intersected in the hole appear to have all formed from a single leucogranite protolith alteration developed as symmetrically zoned halos around central fractures as a result of the interaction of a fluoride rich orthomagmatic fluid with evolved leucogranite during alteration k feldspar was first replaced by albite with further alteration albite was replaced by muscovite resulting in the formation of quartz sericite greisen ore minerals are locally present in this zone closer to veins muscovite is replaced by topaz and quartz producing a quartz topaz greisen with which the most intense mineralization is associated this latter greisen is enriched in f fe s zn and sn suggesting that these elements were added by the mineralizing fluid next to the vein dissolution of pyrrhotite sphalerite and cassiterite characterizes quartz greisen in which the concentration of ore forming elements sn fe s f zn cu is lower than in the quartz topaz greisen microthermometric measurements of fluid inclusions in quartz from the various alteration zones show that this alteration sequence was formed by only one greisenizing event and that temperature was approximately constant 450 degrees c the fluid responsible for greisen formation was an nacl brine containing subordinate and variable concentrations of fe mn and k measured eutectic temperatures of fluid inclusions are lowest in quartz topaz greisen as a result of an increase in the fe concentration due to pyrrhotite dissolution oxygen fugacity which was calculated from the co 2 ch 4 ratio in gases released by crushing fluid inclusion rich samples displays a corresponding minimum since pyrrhotite dissolution releases fe super 2 the distribution of pyrrhotite and the fluid inclusion data indicates that pyrrhotite was precipitated close to the vein during early stages of the alteration and reprecipitated farther out as alteration progressed this suggests that alteration zones moved away from the vein and widened with time the salinity of fluid inclusions varies between 27 and 41 wt percent nacl equiv and increases linearly with increasing distance from the vein even in the absence of na bearing phases it therefore follows that sodium was transported toward the fracture vein down a chemical potential gradient this occurred through compensated infiltration i e a regime in which flow was dominantly parallel to the fracture but individual aliquots of fluid followed complex paths back and forth between the fracture and the rock cassiterite precipitated in quartz topaz greisen in response to a ph increase of the mineralizing fluid due to its interaction with the wall rock other components affecting cassiterite solubility were either constant temperature or acted against its precipitation f sub o 2 and a sub cl super

the contribution of salt fingers to vertical mixing in the north atlantic tracer release experiment abstract the north atlantic tracer release experiment natre was performed in an area moderately favorable to salt fingers however the classic finger signature of a distinct thermohaline staircase caused by upgradient density flux was absent this is likely because mixing by turbulence was sufficiently strong to disrupt the formation of permanent step and layer systems despite the lack of a staircase optical shadowgraph profiles revealed that small scale tilted laminae previously observed in a salt finger staircase were abundant at the natre site using microstructure observations the strength of salt finger mixing has been diagnosed using a nondimensional parameter related to the ratio of the diffusivities for heat and buoyancy the dissipation ratio by examining the dissipation ratio in a parameter space of density ratio r and richardson number ri the signal of salt fingers was discerned even under conditions where turbulent mixing also occurred while the model for turbulence descr

deflation and redeposition of sand dunes in finnish lapland abstract deflation and redeposition of aeolian sands in finnish lapland have been studied by analysis of their sedimentology and stratigraphy by dating buried charcoal layers and by obtaining tl dates the thickness of redeposited sands on buried soils ranges from a few decimetres to more than two metres original dune formation after deglaciation finished around 7000 bp subsequent aeolian activity has been mainly destructive in nature deflation started in some regions about 4800 bp continuing with several breaks until the present some deflation basins have stayed active for at least 1300 years however it is too early to draw general conclusions for the whole area forest fires have been important reactivators of aeolian sand drift but tend to be rather local events change in the ground water table is a basic factor affecting deflation at present human impact and overgrazing by reindeer seem to increase deflation

a quantitative holocene climatic record from diatoms in northern fennoscandia abstract a diatom based calibration model for predicting summer temperatures was developed using climatically sensitive subarctic lakes in northern fennoscandia the model was applied to a sediment core from a treeline lake to infer trends in holocene climate the record exhibits long term variations as well as a series of shorter term fluctuations on a time scale of centuries summers were warmest in the area about 6200 cal yr b p and featured distinct cooling episodes around 8300 7200 4200 3000 and 400 cal yr b p most of these coinciding with some known climate events e g the 8200 cal yr b p event and the little ice age the similarity of the observed shifts with the pacings of climate events from marine and ice core records represents evidence for coupled ocean atmosphere forcing of the regional climate

mid holocene warming in the northwest kola peninsula russia northern pine limit movement and stable isotope evidence a set of 40 subfossil scots pines pinus sylvestris l was sampled in small lakes beyond the modernpine limit in the northwest kola peninsula russia radiocarbon dating suggests that the pine exp

the disturbance regime of an early holocene swamp forest in the czech republic as revealed by dendroecological pollen and macrofossil data abstract a unique remnant of forest dating back to the period 9733 7897 yr bc and consisting of hundreds of tree bases was discovered in the czech republic we aimed to reveal the complex disturbance history of this sub fossil forest using dendrochronology and to describe its detailed plant species composition changes using palaeobotanical techniques analysing such early holocene forest dynamics should help us understand the ability of the forest community to actively adapt to climate change and generally to understand the role of dynamic instability in ecosystem evolution we anatomically identified woody species in 488 samples and determined the ages growth suppressions releases and fire scars in 116 well preserved tree ring series using a modern boundary line approach this image of the forest structure and dynamics was supplemented with analyses of pollen spectra and plant macrofossils in excavated profiles in order to achieve accurate dating we dated 87 samples using 14c and synchronized tree ring series and compared them with an existing pinus sylvestris chronology the developmental trajectory of the forest was unique and did not match the general trend of postglacial pine growth in central europe palaeobotanical proxies indicated that during the circa 2000 years the forest persisted this early holocene ecosystem passed through several phases reflected in the species composition of the vegetation as well as in habitat conditions nevertheless the dominance of pine and the complex fine scale disturbance regime were relatively robust and did not change fundamentally low severity fires and short term changes in soil moisture regime were crucial disturbance agents in the ecosystem stand replacing disturbances were not found up to the gradual collapse of the forest around 8300 yr bc replaced by a swamp community the disturbance regime was relatively stable suggesting a mitigating effect of changing climate due to the predominance of pine in the forest

lake level fluctuations at ljustjarnen central sweden and their implications for the holocene climate of scandinavia abstract a detailed reconstruction of water level fluctuations in ljustjarnen a small kettle lake in south central sweden provides a preliminary outline of holocene changes in water balance for that region lake levels were generally high from 9200 to 8000 yr b p falling from then until c 6500 6000 yr b p and rising again by 5000 yr b p temporary lowerings were recorded c 4000 yr b p and c 2000 yr b p and water levels have risen dramatically since c 500 yr b p the reconstruction is based on sedimentologic and fossil analyses of multiple cores as well as on geomorphological evidence comparison of lake level fluctuations in south central sweden with those from southern sweden and western finnish lapland and with records of glacier fluctuations in the scandinavian mountains suggest a distinct north south contrast in water balance from 9000 to 5000 yr b p consistent with strongly zonal atmospheric circulation during that period between 7000 and 5000 yr b p the mid holocene dry period appears to have been time transgressive across scandinavia perhaps as a result of a gradual shift in the position of the atlantic polar front and its associated cyclonic stormtrack since 4000 yr b p however most detectable fluctuations are synchronous across scandinavia with the most prominent and widespread change being increased net moisture during the little ice age

direct transformation of tree ring measurements into palaeoclimate reconstructions in three dimensional space here we propose a new method for dendroclimatic reconstructions this direct reconstruction technique direct performs modelling of the age dependent association between climate and growth in thre

holocene climate of the kola peninsula evidence from the oxygen isotope record of diatom silica holocene climate variability was studied in a lake sediment record covering the last c 9000 years from lake chuna on the kola peninsula north west russia using the oxygen isotope composition of diatom silica 18odiatom the evaporation of the lake waters is likely to be minimal and thus the isotopic composition of the lake waters recorded by the 18odiatom reflects the isotopic composition of summer precipitation overall the 18odiatom signal seems to record a predominance of the polar arctic air mass bringing cold summer air temperatures immediately after the last glaciation and again after 4000 years to present time the atlantic maritime air mass is likely to have supplied warm summer rainfall especially in the mid holocene the pattern is broadly consistent with a quantitative pollen reconstruction from chuna lake which suggests higher mean july temperatures from deglaciation to 5500 years bp with a rather steep decline to lower temperatures after 4000 years bp our results support the general regional scenario of a mid holocene warm period deduced from the higher tree line vegetation changes and glacier fluctuations in fennoscandia however the 18odiatom record from the kola peninsula suggests a relatively cold early holocene with a gradual shift to warmer conditions to a maximum at around 5000 4000 years bp assuming that the modern precipitation temperature relationship has been constant throughout the holocene

the properties of reservoir water in post mining excavations of cambrian and devonian quartzite sandstones holy cross mountains in the holy cross mountains southern poland there are numerous disused quarries some of these are filled with water and some despite their nearby location have extremely diverse physicochemical and chemical properties of their waters one such object is the wi niowka mala reservoir its waters contain large amounts of sulfates 700 mg l and iron 24 mg l which are weathering products of rocks containing metal sulfides mainly pyrite in the direct drainage zone as a consequence there is an increase in the electrolytic conductivity of the water supplying the reservoir resulting in very low ph values 4 this article presents the detailed limnological characteristics of this reservoir and explains the process that led to its water acidification a control reservoir barcza was also selected for the tests although it is also a post mining excavation it has a neutral ph and a low concentration of sulfates and iron the examined reservoirs differ in the hydrochemical type of waters the wi niowka mala reservoir represents a sulfate calcium double ion type so42 ca2 and the barcza reservoir a bicarbonate calcium type hco3 ca2 the concentrations of the main ions occurring here are shaped by the lithological features of the surrounding rocks respectively upper cambrian quartzite sandstones with pyrite mineralization zones lower devonian sandstones cut by mudstones and claystones with tuffite inserts

dating raised bogs new aspects of ams 14c wiggle matching a reservoir effect and climatic change abstract high resolution ams dating of holocene raised bog deposits engbertsdijksvenen the netherlands shows natural 14c variations wiggles which can be matched with the dendrochronological calibration curve comparison of our results with other conventionally dated peat cores and the 14c record shows an unexpected and as yet unreported reservoir effect and a marked and sudden wetting of the bog surfaces coinciding with the advent of a sporer type solar minimum the homeric minimum the potential of ams dating to vastly improve the accuracy of holocene chronologies is demonstrated

humic and fulvic acid stratigraphy of the holocene sediments from a small lake in finnish lapland holocene sediments from a small lake hirvaslompolo in eastern finnish lapland have been ana lysed for their content of humic substances the amount and proportion of humic and fulvic acids were f

fennoscandian summers from ad 500 temperature changes on short and long timescales quantitative estimates of 1480 years of summer temperatures in northern fennoscandia have previously been derived from continuous treering records from northern sweden here we show the results of spectral analyses of these data only a few peaks in the spectra are consistently significant when the data are analyzed over a number of sub periods relatively timestable peaks are apparent at periods of 2 1 2 5 3 1 3 6 4 8 32 33 and for a range between 55 100 years these results offer no strong evidence for solar related forcing of summer temperatures in these regions our previously published reconstruction was limited in its ability to represent long timescale temperature change because of the method used to standardize the original tree ring data here we employ an alternative standardization technique which enables us to capture temperature change on longer timescales considerable variance is now reconstructed on timescales of several centuries in comparison with modern normals 1951 70 generally extended periods when cool conditions prevailed prior to the start of the instrumental record include 500 700 790 870 1110 1150 1190 1360 1570 1750 a d with the most significant cold troughs centred on about 660 800 1140 1580 1620 and 1640 predominantly warm conditions occurred in 720 790 870 1110 and 1360 1570 with peaks of warmth around 750 930 990 1060 1090 1160 1410 1430 1760 and 1820

on solar forcing of holocene climate evidence from scandinavia the focus of this study is the possible correlation between changes in the climate of scandinavian and changes in solar irradiation reliable information about holocene climatic change in sweden and norway is currently available from two main sources the 14c dating of pine wood retrieved from above the present pine tree limit and studies of glacier variations based on proglacial lacustrine sediments and on moraines the reconstructed alpine tree limit reveals that summer temperature in general was warmer during the early holo cene than it was during the late holocene superimposed on this general trend are several fluctuations of a few hundred years duration relatively cold periods with a duration of the order of 300 600 years occurred frequently during the holocene in this paper dates of the major climatic events are compared with an index of solar activity the so called 14c anomalies for most of the last 9000 years a good correspondence is demonstrated between the timing of cold events in scandi

holocene temperature changes in northern fennoscandia reconstructed from chironomids using bayesian modelling the recently developed bayesian multinomial calibration model bummer was applied to the fossil chironomid assemblages of a lake situated at the present tree line in northern fennoscandia to reconstruct patterns in holocene climates the results are compared with inferences derived using non bayesian weighted averaging partial least squares regression the reconstruction exhibits both long term trends as well as a series of shorter term oscillations abrupt climatic excursions were particularly characteristic for the early holocene period with cooling episodes around 9200 8600 and 8200 cal yr bp the interval from ca 8000 to 5800 cal yr bp appeared to be warm and stable but was followed by a pronounced climatic cooling around 5800 cal yr bp leading to a relatively long lasting mid holocene temperature minimum between ca 5800 and 4000 cal yr bp the reconstruction during the latter part of the holocene is relatively featureless which may partly be due to gradual shallowing of the lake by sedimentation that may have affected chironomid compositions thereby masking the climate signal the major climatic patterns in our reconstruction agree well with inferences from greenland ice and marine sediments and are also in line with the previous reconstructions based on diatoms and pollen from the same core although the finer scale variations reflected by the three proxies do not always match the overall results provide evidence for climatic complexity during the holocene epoch and demonstrate that bayesian modelling is highly suitable for reconstruction purposes

holocene humidity changes in northern finnish lapland inferred from lake sediments and submerged scots pines dated by tree rings conclusive evidence for a rise in water levels has been found in connection with lake sediment studies undertaken partly in collaboration with the pine megafossil sampling and dendrochronological work in northern finnish lapland the change in lake level stands is shown by slow sedimentation rate in the early to mid holocene and an increase thereafter these data indicate a regional rise in water levels during the latter part of the holocene following a relatively dry period between 8000 and 4000 bp synchronous changes also indicating rising water levels have been observed in the diatom and cladoceran assemblages of the sediment cores subfossil scots pines pinus sylvestris l have been preserved in large quantities in small lakes in lapland because in many cases the rising water level has inundated the trunks after death the position of the subfossil trunks and stumps often indicates that the pines have been growing on dry land at the sides of the lakes in which they are now submerged traces of

vertical diffusion in meromictic powell lake british columbia simple diffusion models are developed to describe vertical diffusion in powell lake a meromictic former fjord containing trapped seawater measurements of the vertical distribution of chlorinity are used to determine the dependence of vertical diffusivity on depth near the bottom of the lake the vertical diffusivity is about 4 times that of the molecular diffusivity of salt on this basis ions with different molecular diffusion coefficients will be lost from the bottom of the lake at different rates which partially explains differences observed in the ratios of concentrations of ions in saline bottom water from ratios characteristic of seawater the observed increase in temperature with depth is shown to result from the geothermal heat flux through the lake s bottom

evidence for enhanced mixing over rough topography in the abyssal ocean the overturning circulation of the ocean plays an important role in modulating the earth s climate but whereas the mechanisms for the vertical transport of water into the deep ocean deep water formation at high latitudes and horizontal transport in ocean currents have been largely identified it is not clear how the compensating vertical transport of water from the depths to the surface is accomplished turbulent mixing across surfaces of constant density is the only viable mechanism for reducing the density of the water and enabling it to rise however measurements of the internal wave field the main source of energy for mixing and of turbulent dissipation rates have typically implied diffusivities across surfaces of equal density of only approximately 0 1 cm2 s 1 too small to account for the return flow here we report measurements of tracer dispersion and turbulent energy dissipation in the brazil basin that reveal diffusivities of 2 4 cm2 s 1 at a depth of 500 m above abyssal hills on the flank of the mid atlantic ridge and approximately 10 cm2 s 1 nearer the bottom this amount of mixing probably driven by breaking internal waves that are generated by tidal currents flowing over the rough bathymetry may be large enough to close the buoyancy budget for the brazil basin and suggests a mechanism for closing the global overturning circulation

a new approach to calculating holocene winter precipitation by combining glacier equilibrium line altitudes and pine tree limits a case stud from hardangerjokulen central southern norway at hardangerjokulen central southern norway detailed knowledge of the number age and magnitude of holocene glacier fluctuations is used to reconstruct variations in equilibrium line altitude ela for the last 10 000 years present and past elas are based on an accumulation area ratio aar of 0 7 and are adjusted for land uplift a synchronous relationship between advanced glacier positions and the highest pine tree limits pinus sylvestris l is demonstrated for the early to mid holocene in southern scandinavia which indicates that warm summers were compensated for by high winter precipitation based on pine tree limit fluctuations as a measure of mean ablation season temperature holocene variations in winter precipitation at hardangerjokulen have been calculated by substitution in the close exponential relationship between mean ablation season temperature and winter precipitation at the ela of norwegian glaciers setting the winter precipitation during the period ad 1961 1990 at 100 mean values

holocene climatic change reconstructed from diatoms chironomids pollen and near infrared spectroscopy at an alpine lake sjuodjijaure in northern sweden the results of a multiproxy study reconstructing the climate history of the last 9300 years in northern sweden are presented it is based on diatom chironomid and pollen analyses as well as near

turbulent layering beneath the pycnocline in a strongly stratified pit lake temperature microstructure observations from a pit lake show alternate layers of high and low turbulence beneath a very strong pycnocline the layers were clearly defined around 0 3 0 5 m thick and were found both at the edge and in the center of the pit lake in the most energetic regions the turbulent energy dissipation rate reached 5 10 26 m 2 s 23 and the dissipation rate of thermal variance almost reached xu 5 10 24 8 c 2 s 21 the turbulent fluid in the middle of the lake had a higher dissipation ratio the thermal component of potential energy gain vs kinetic energy loss when compared with the sidewalls this is attributed to different forcing mechanisms for the turbulence we hypothesize that basin scale internal waves in conjunction with the topography create sidewall boundary layers in the interior regions of the pit lake the turbulent layers are probably generated by instability due to focusing of short wavelength internal waves a pit lake is a water body that forms in a mining void on the cessation of mining activity usually a lake only forms in regions where the accumulation of groundwater inflow and rainfall exceed evaporation alternately the pit lake can be actively filled as an aid to remediation or for storage some of the dissolved material that finds its way into a pit

holocene vegetation history and climate change on the northern kola peninsula russia a case study from a small tundra lake abstract a sediment core from lake kp3 unofficial name located near the coastline on the northern kola peninsula 100 km east south east from murmansk russia 69 04 19 n 36 00 40 e provides palynological evidence for the vegetation and climate history of the last 14 000 years during the younger dryas time the climate was cold and vegetation cover around the lake consisted of a shrub birch willow tundra with warming during the early holocene birch forest expanded across the kola peninsula and by 9500 cal yr bp a dense birch tree forests likely extended as far north as the modern barents sea coastline by about 7800 cal yr bp alnus incana was present as an admixture to birch in wet places as far north as the barents sea shoreline scots pine expanded to north of its modern limits on the kola peninsula between 7900 and 3700 cal yr bp with its maximum northward progress and abundance at 7300 6200 cal yr bp although scattered pines may have grown near the coastline pine forests did not reach the barents sea coastal area and the region remained covered with birth forest tundra as much as during earlier holocene the expansion of birch forest and pine forest in the early to mid holocene likely reflects the impact of higher amounts of summer radiation due to milankovitch forcing and warmer temperatures in the north atlantic ocean and barents sea the mid holocene summer warming in the barents sea coastal area likely ranged from 1 c to 1 5 c above modern conditions following 5900 cal yr bp shrub tundra communities began to replace birch forest and pines on the northernmost kola peninsula the modern tundra which occupies the coastal region near lake kp3 was established at about 3100 cal yr bp the vegetation and climatic changes evident on the northern kola peninsula are similar to those evident in northernmost fennoscandia

variations in apparent mixing efficiency in the north atlantic central water abstract microstructure data from the north atlantic tracer release experiment natre are presented providing detailed profiles of the thermal variance in the upper 360 m of the canary basin for the fall and spring seasons the osborn cox model is used to compute the diffusivity kt the diffusivity for the depth range 240 340 m is found to be 1 0 0 04 10 5 m2 s 1 in the fall and 2 2 0 1 10 5 m2 s 1 in the spring in good agreement with dye inferred diffusivities at similar depths measured turbulent kinetic energy tke dissipation rates were found to be contaminated by hydrodynamic noise so the osborn dissipation method was not used to compute k however data segments for which the tke dissipation rate e was large enough to be unaffected by noise were used to compute the apparent mixing efficiency d the computed d values are used to investigate variations in apparent mixing efficiency with respect to density ratio r and turbulence reynolds number e n2 in an attempt to eluci

ray waves in a pit lake 1 the special basin shape of island copper mine pit lake and its sharp salinity stratification make it an ideal place to investigate ray waves or internal wave beams as the more recent oceanographic literature tends to name the observed phenomenon a first mode internal seiche oscillates the deep water vertically over the regular bench structure of the sidewalls at a distinct frequency theoretical considerations show the disturbances result in internal wave beams traversing the stratified water body at a known angle steep sidewalls prevent the ray waves from being trapped in the beach zone instead the reflection at the extremely strong pycnocline creates a vertical interference pattern here we numerically derive the vertical length scale of this interference to be 0 43 m this scale is in full agreement with the repeated turbulence pattern discovered underneath the pycnocline

wind forced motions in stratified lakes and their effect on mixed layer shear the solution for the response of a rectangular n layered stratified lake to an arbitrarily varying in time wind stress is presented the case n 3 is considered in detail for a three layered lake the response is made up of the individual responses of one external and two internal modes when the upper layer is shallow relative to the other two layers the mixed layer shear is due almost entirely to the slower second mode response moreover the upper interface can tilt quite severely while the lower interface remains nearly flat calculations based on the three layer model are compared with measurements made in wellington reservoir western australia

holocene mean july temperature and winter precipitation in western norway inferred from palynological and glaciological lake sediment proxies reconstructions of mean july temperature tjul and winter precipitation pw for the last 11 500 years on the folgefonna peninsula are presented tjul was reconstructed using pollen climate transfer functions and pw was reconstructed based on the exponential relationship between mean solid winter precipitation and ablation season temperature at the equilibrium line altitude ela with a reconstructed former ela using tjul as the proxy for ablation season temperature the reconstructions from the folgefonna peninsula suggest that the early holocene was relatively cool and dry until c 8000 cal yr bp followed by a warm and humid mid holocene until c 4000 cal yr bp with inferred tjul above 128c and pw reaching as high as 225 of the present day subsequent to c 4000 cal yr bp a reduction is seen in both inferred tjul and pw with large fluctuations during the last 500 years in addition new calculations of pw from two glaciers hardangerjokulen and jostedalsbreen in southern norway are presented the results show that pw varied in phase at all glaciers probably as a response to the same climate forcing factor during the early holocene a major shift is suggested between winds from the west and the east