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This paper presents a review on more than hundred years of palaeoenvironmental research in Sweden; from early descriptions of peat and tufa deposits in the late nineteenth and early twentieth centuries to multiproxy transfer function studies in the late twentieth and early twenty-first centuries CE. Research on Holocene climate variability has a long history in Sweden and many ideas and concepts about changes in temperature and precipitation during the Holocene originated in Fennoscandia. The Holocene climate evolution in Sweden follows a pattern in common for many northern latitude records with a rapid warming starting at the Pleistocene–Holocene boundary at c. 11 650 cal a BP, followed by the middle Holocene thermal maximum between c. 8000 and 5000 cal a BP. A change to colder and wetter conditions starts c. 4000 cal a BP and lasts until the late 1800 s CE. There is evidence for climatic anomalies such as the 8.2 and 4.2 ka BP events and the Little Ice Age (LIA) but only inconclusive evidence for other events, such as the 10.3 ka BP event. The main pattern of Holocene climate and environmental evolution is well known for most parts of Sweden, but the present review also shows that several research questions remain to be addressed. [ABSTRACT FROM AUTHOR]

In this paper we test the performance of the Regional Estimates of VEgetation Abundance from Large Sites (REVEALS) model using pollen records from multiple small sites. We use Holocene pollen records from large and small sites in southern Sweden to identify what is/are the most significant variable(s) affecting the REVEALS-based reconstructions, i.e. type of site (lakes and/or bogs), number of sites, site size, site location in relation to vegetation zones, and/or distance between small sites and large sites. To achieve this objective we grouped the small sites according to (i) the two major modern vegetation zones of the study region, and (ii) the distance between the small sites and large lakes, i.e. small sites within 50, 100, 150, or 200 km of the large lakes. The REVEALS-based reconstructions were performed using 24 pollen taxa. Redundancy analysis was performed on the results from all REVEALS-model runs using the groups within (i) and (ii) separately, and on the results from all runs using the groups within (ii) together. The explanatory power and significance of the variables were identified using forward selection and Monte Carlo permutation tests. The results show that (a) although the REVEALS model was designed for pollen data from large lakes, it also performs well with pollen data from multiple small sites in reconstructing the percentage cover of groups of plant taxa (e.g. open land taxa, summer-green trees, evergreen trees) or individual plant taxa; however, in the case of this study area, the reconstruction of the percentage cover of Calluna vulgaris, Cyperaceae, and Betula may be problematic when using small bogs; (b) standard errors of multiple small-site REVEALS estimates will generally be larger than those obtained using pollen records from large lakes, and they will decrease with increasing size of pollen counts and increasing number of small sites; (c) small lakes are better to use than small bogs if the total number of small sites is low; and (d) the size of small sites and the distance between them do not play a major role, but the distance between the small sites and landscape/vegetation boundaries is a determinant factor for the accuracy of the vegetation reconstructions. [ABSTRACT FROM AUTHOR]

Aim This paper seeks to elucidate the first post-glacial arrival of tree species to high elevations in the Scandes. This enables testing of general theories concerning glacial refugia, immigration routes and palaeoclimate. Location The study site, 1360 m a.s.l., was close to the summit of Mt Åreskutan in the alpine region of the southern Swedish Scandes, 400–500 m above modern tree-limits. Methods Tree megafossils (trunks, roots, cones) were retrieved (and radiocarbon-dated) from the ground surface in the forefields of receding `perennial' snow-patches. This approach allows elevational range-margin reconstructions to be made with an accuracy not possible with any other method. Results and conclusions Megafossils were recovered substantially higher and earlier than previously recorded or inferred for tree growth in this part of Europe. The species were Betula pubescens Ehrh. ssp. tortuosa (Ledeb.) Nyman, Picea abies (L.) Karst. and Pinus sylvestris (L.). The oldest dates obtained are c . 14,000, 11,000 and 11,700 BP for these species, respectively. For the first time, explicit evidence of tree growth in the Late-Glacial (including the Younger Dryas stadial) is demonstrated for central/northern Scandinavia. The swift appearance of boreal tree species at high northern latitudes and altitudes on the western fringe of Scandinavia and near the most extended margin of the Weichselian ice sheet hypothetically suggests that the first immigration of the trees considered here was from the west. Glacial refugia for these species (other plants and animals as well) on the exposed continental shelf areas west and southwest of Norway is hypothesized. By extension, the results fit into a more general pattern, suggesting the presence of boreal and temperate trees quite close to the full glacial (Weichselian) ice margins in central Europe. Thus, the Quaternary forest and landscape history of Europe seems more complex than previously believed. [ABSTRACT FROM AUTHOR]

In a comment on the paper by Sundqvist et al. (2007a), Hammarlund and Edwards suggest that the oxygen isotope signal of the speleothem records K1 and L4 from northwestern Sweden as well as for the earlier published stalagmite SG93 from northern Norway should mainly reflect variation in the δ18O of mean annual precipitation. The main argument used by the authors is that the SG93 dδ18O record should show remarkable similarities with the lacustrine carbonate dδ18O record from Lake Tibetanus. The similarities between SG93 and Lake Tibetanus are mainly seen for the period between 10 and 9 ka BP, which is a period where both records have higher dδ18O values compared with later in the Holocene. If true, this would indicate that temperatures in northern Scandinavia would have reached their Holocene maximum between 10 and 9 ka BP, which is contrary to what has been reported from other archives in the region which place the Holocene climatic optimum somewhere between 8 and 5 ka BP. Several factors affect the dδ18O of speleothems and definitely also by annual mean dδ18O of the local precipitation. However, for Holocene speleothems from northern Scandinavia as well as from the Alps this signal seems to be overridden by other factors, such as variable mixing of summer and winter precipitation of cave drip water as well as the temperature-dependent fractionation between calcite and water. But the relative importance of the factors can differ between different timescales, caves and even speleothems from the same cave, depending on hydrological pathways. To better understand the factors controlling the stable oxygen isotopes in precipitation and proxy archives back in time there is a need for more highly resolved records as well as for more atmospheric and hydrological modelling. [ABSTRACT FROM AUTHOR]

Loess deposits are common in the mid‐latitudes and are excellent records of past climate, landscape change and dust. However, loess deposits are seldom reported from Fennoscandia. Here we investigate two former glaciofluvial areas in central Sweden, Brattforsheden and Bonäsheden, where post‐glacial loess and sand dune activity have been documented previously. Based on detailed mapping, grain size, scanning electron microscopy and optically stimulated luminescence dating analyses, we confirm the presence of loess deposits at the sites and extend the known area of loess coverage. Our results suggest that loess deposits are more common than previously thought in Sweden. The results also demonstrate that basal parts of the loess are often mixed with underlying sediment, which may be a common feature of thin loess deposits close to former ice margins. Quartz luminescence is well suited for dating these deposits, but ages from the mixed basal loess layers are older than expected, while ages from undisturbed loess extend to c. 5 ka. The loess ages contrast with the timing of main dune activity in these areas, which is dominantly in the 1–3 kyr post‐deglaciation (c. 10.9–10.5 cal kyr BP). We suggest that either sediment mixing during soil formation is responsible for the mid‐Holocene loess ages, or that the loess deposits record periodic landscape destabilization into the mid‐Holocene. Furthermore, there is a clear topographic control on aeolian sedimentary facies, with loess mantling high ground and dunes restricted to valleys. Loess deposits are also primarily found to the south and southwest of source areas, implying transport from the north and east. This pattern contrasts with evidence for NW winds inferred from associated sand dunes. At present, the reasons for this mismatch are unclear, although one possible explanation is that silts deposited at higher elevations were affected by Ekman flow deflection of NW surface winds. [ABSTRACT FROM AUTHOR]

Värmland in south western Sweden lies across the established zone of marine-terrestrial transition of the Scandinavian Ice Sheet (SIS) margin. The region lies inside the Younger Dryas maximum limit reached at 12.7 cal ka BP and the area of rapid final SIS retreat from 11.5 cal ka BP. LiDAR data across Värmland allows more detailed observation and analysis of glacial landforms formed during this stage than previously possible. This study synthesises geomorphological mapping performed on highly detailed digital elevation models (DEMs) and field observations across the region around Torsby in northern Värmland to reconstruct the dynamics of the ice sheet as it retreated. Several landforms that developed during deglaciation are identified and clearly reflect the change from a marine to terrestrially terminating ice margin. Ice-marginal deltas suggest a slowing of retreat at the point of marine-terrestrial transition. Increased topographic control on ice-sheet flow, pattern of drainage and ice sheet decay is indicated by the distribution of streamlined terrain, eskers, and outwash material. Hummocky terrain across low ground and incised valleys suggest persistence of ice in topographic lows beyond the retreat of the main ice front. Combined analysis of identified landforms allows a model for the pattern of retreat to be produced that traces the retreating ice sheet margin in far greater detail than previously has been possible in this area. This provides important data for understanding the final retreat of the SIS and details processes likely occurring beneath the margin of the Greenland Ice Sheet today. [ABSTRACT FROM AUTHOR]

We present a quantitative reconstruction of local forest history at two sites, Stavsåkra (hemiboreal zone) and Storasjö (southern boreal zone), in southern Sweden (province of Småland) to evaluate possible causes of contrasting Holocene fire histories in mid- and late Holocene. The Landscape Reconstruction Algorithm (LRA) is applied to evaluate between-site differences in the relative abundance of deciduous trees and Pinus (pine) and landscape/woodland openness during the Holocene. The LRA estimates of local vegetation abundance are compared with other proxies of local vegetation, that is, plant and beetle remains. The LRA results suggest that Pinus was a major tree taxon in the woodlands of Storasjö during mid- and late Holocene, while Tilia (linden) and Betula (birch) were dominant at Stavsåkra. The contrasting fire histories are shown to be strongly related to between-site differences in tree composition during mid-Holocene, 4000–2000 bc in particular. The archaeological/historical and beetle data indicate contrasting land uses from c. 1000 bc (late Bronze Age/early Iron Age), grazing in open Calluna heaths at Stavsåkra and woodland grazing at Storasjö. Between-site differences in fire history during late Holocene were likely due to different land-use practices. Between-site differences in tree composition in mid-Holocene are best explained by local climatic and geological/geomorphological differences between the hemiboreal and southern boreal zones of Småland, which might also be the primary cause of between-site differences in land-use histories during late Holocene. Maintenance of biodiversity at the landscape scale in the study area requires that existing old pine woodlands and Calluna heath are managed with fire and cattle grazing. Further climate warming might lead to higher probabilities of climate-induces fire, in particular in pine-dominated woodlands. [ABSTRACT FROM AUTHOR]

Holocene mean July (TJul) and mean January (TJan) temperatures were reconstructed at Lake Trehörningen in southwest Sweden using pollen–climate calibration functions and converted into anomalies relative to modern temperatures. The anomalies were applied to 28 meteorological stations in Denmark, with each station adjusted to account for spatial variability in both TJul and TJan. The resulting reconstructions were merged to create composite TJul and TJan records. The individual reconstructions were also used to establish the parameterization of the TJul and TJan values, resulting in Holocene temperature maps for all of Denmark. Low TJul values characterised southern Sweden and Denmark at the start of the Holocene, followed by an increase during the early Holocene. Likewise, TJan was initially low at the start of the Holocene, followed by an increase between 10 500 and 9900 cal. BP. Thereafter, TJan was relatively stable between 9900 and 8000 cal. BP. The general increase in temperature during the early Holocene was accompanied by a decrease in the amplitude of the mean monthly temperature record, indicating that a maritime climate was established at this time. Maximum TJul and TJan are recorded during the mid-Holocene interval from 8000 to 4500 cal. BP, with consistently high July temperatures (>18°C) between 6700 and 5400 cal. BP. During the late Holocene, both TJul and TJan gradually decreased. The Holocene temperature maps of Denmark reveal spatial patterns in both summer and winter temperature. In the summer, an east–west decreasing temperature gradient, related to a maritime effect, has persisted in Denmark throughout the Holocene. In contrast, the temperature in winter has varied spatially along subtle coastal–inland and topographical gradients. Various mechanisms have been invoked to explain the Holocene trends in temperature, including the melting of the Scandinavian Ice Sheet, changes in insolation, and changes in the dominant type of atmospheric circulation affecting northern Europe. [ABSTRACT FROM PUBLISHER]

Faunal communities have been shaped in different ways by past climatic change. The impact of the termination of the last Glacial and the onset of the present (Holocene) Interglacial on large-scale faunal shifts, extinction dynamics and gene pools of species are of special interest in natural sciences. A general pattern of climate-triggered range expansion and local extinction of vertebrate species is known for Europe, and shows that in the modern temperate zone the main faunal change took place mainly during the Late Glacial (14 700-11 700 years ago) and Early Holocene (11 700-9 100 years ago). Based on large datasets of new radiocarbon data, we present precise temporal dynamics of climate-driven disappearance and appearance of reindeer and pond turtle in southern Sweden. These two species are significant climate indicators in Late Quaternary biostratigraphy. Our data reveal that the reindeer disappeared from southern Sweden ca. 10 300 years ago, whereas the pond turtle colonized the area ca. 9 860 years ago, with a 450-year gap between each species. This provides evidence for a sudden environmental turnover, causing the replacement of an arctic faunal element by a thermophilic species. The postglacial range dynamics of pond turtle and reindeer are a unique model case, allowing insights into the faunal turnover of other vertebrates during the last dramatic natural global warming event at the Pleistocene-Holocene transition. [ABSTRACT FROM AUTHOR]

A Holocene sediment sequence from Lake Seukokjaure, a subarctic lake at tree-line in northern Sweden, was analyzed to assess major changes in the structure and functioning of the aquatic ecosystem in response to climate change and tree-line dynamics. The compiled multi-proxy data, including sedimentary pigments, diatoms, chironomids, pollen, biogenic silica (BSi), carbon (C), nitrogen (N) elemental and stable-isotope records, and total lake-water organic carbon (TOC) concentration inferred from near-infrared spectroscopy (NIRS), suggest that the Holocene development of Lake Seukokjaure was closely coupled to changes in terrestrial vegetation with associated soil development of the catchment, input of allochthonous organic carbon, and changes in the light regime of the lake. A relatively productive state just after deglaciation around 9700 to 7800 cal years BP was followed by a slight long-term decrease in primary production. The onset of the local tree-line retreat around 3200 cal years BP was accompanied by more diverse and altered chironomid and diatom assemblages and indications of destabilized soils in the catchment by an increase in variability and absolute values of δ13C. An abrupt drop in the C/N ratio around 1750 cal years BP was coupled to changes in the internal lake structure, in combination with changes in light and nutrient conditions, resulting in a shift in the phototrophic community from diatom dominance to increased influence of chlorophytes, likely dominated by an aquatic moss community. Thus, this study emphasizes the importance of indirect effects of climate change on tree-line lake ecosystems and complex interactions of in-lake processes during the Holocene. [ABSTRACT FROM AUTHOR]

Lacustrine sediments are often used for paleoclimate reconstructions as continuous archives of several physical and biological proxies. The relation between autochthonous and allochthonous sedimentation in alpine lakes is a complex system that may cause difficulties when interpreting biological and physical parameters. Results from previous studies of alpine lakes in northern Sweden have demonstrated that non-glacial processes produce minerogenic lake deposits with similar physical characteristics (density, LOI, magnetic susceptibility, grain-size) as those that have been associated with glacier fluctuations in proglacial lakes. In this study of two consecutive proglacial alpine lakes we show that fluvial redeposition of alluvial fan deposits significantly affects the Holocene lake sedimentation. Depending on the geomorphological setting, such fluvial redeposition signals may actually overprint a glaciofluvial signal. We also show that minerogenic laminations of fluvial origin are impossible to separate from the type of laminations usually used to infer glacier activity using the most common lithological sediment parameters. This emphasizes the complexity of sediment transport system in proglacial (paraglacial) settings where redeposition of older glacial sediment is of major importance. Our results highlight the need for thorough understanding of the geomorphological setting before inferences are made about climate variations from sedimentation in alpine lakes. Both lakes in this study contain sediment sequences with both episodic (turbidites) and continuously deposited sediments. Unfortunately we have too few radiocarbon dates to exactly date the turbidites but it is clear that turbidite layers in any case should be excluded from age model constructions since episodic sedimentation significantly influences the sediment age—depth relationship. In our age-model turbidites cause a potential dating error of several hundred, up to a thousand, years. [ABSTRACT FROM AUTHOR]

The temporal variations in distribution pattern of Scots pines (Pinus sylvestris L.) have been used as an annual resolution record of past lake-level changes. Logs, preserved for thousands of years in bog and lakes (subfossil wood), were sampled from small lakes of the Scandinavian Mountains in west-central Sweden to construct a tree-ring chronology from an area where pines are sensitive to growth season (ie, summer) temperature. The chronology spans from AD 2006 to 4868 BC, with two minor gaps at 1600 BC and AD 900 and one larger gap at 2900 BC. The dendrochronological approach can provide a high quality long-term perspective on lake level fluctuations, which possibly can be coupled to changes in humidity. Submerged trunks were found in situ, embedded in sediments, and because trees from the earliest periods were not necessarily found at the deepest levels, this shows clearly that lake levels must have been lower than present at the time of tree-growth. The lake levels must have fluctuated, creating alternating conditions of pine regeneration and mortality. The fluctuating lake levels recorded are suggested to be a result of regional humidity increases and decreases, mainly governed by precipitation changes. Periods of lower lake levels were inferred at 4900-4800 BC, 3800-3600 BC, 3400-3250 BC, 2400-2200 BC, 2100-1800 BC, 1500-1100 BC, 900-800 BC, 400-100 BC, AD 50-300, AD 400-600, AD 900-1100, AD 1350-1500 and AD 1700-1800. Periods of higher lake levels are tentatively encountered at 3600-3400 BC, 3200-2900 BC, 2200-2100 BC, 1700-1500 BC, 1100-900 BC, 800-400 BC, 100 BC-AD 50, AD 300-400, AD 750-900, AD 1100-1250 and AD 1550-1700. [ABSTRACT FROM AUTHOR]

The construction of a new highway between Uppsala and Mehedeby in northern Uppland, southeastern Sweden, has motivated extensive archaeological excavations. To describe changes in shoreline configuration over time, the isolation of nine lake basins has been interpreted from diatom analysis. Their isolation ages were determined from 45 AMS radiocarbon dates (five per site) of terrestrial macrofossils, mainly Betula and Alnus seeds. The isolation ages and the corresponding altitudes indicate a complicated pattern of isostatic uplift during the late Holocene. Neither the present-day isobases nor those for the 'Neolithic Sea' seem to explain their isolation ages and corresponding altitudes in relation to their geographic distribution. Since at least some of the lakes are situated in a relatively pronounced topographic landscape we are inclined to explain the observations as the result of small-scale irregular uplift. Earthquakes are rare in the area at present suggesting short-term tectonic activities along existing fault lines. [ABSTRACT FROM AUTHOR]

Analysis of the decomposition of peat has been used to identify climatic shifts over the last 10000 years in two raised bogs, Stömyren and Kortlandamossen, south-central Sweden. Age–depth curves have been constructed using radiocarbon dates and tephra layers. Peat humification data have been subjected to spectral analyses using the Lomb–Scargle Fourier method and reveal a periodicity of c. 250 years in both records. Cycles of c. 200 yr and c. 400 yr were found at Stömyren and at Kortlandamossen, respectively. These periodicities could correspond to changes in solar activity levels. A test estimating the possible level of noise has been applied to the spectral analyses. The humification indices indicate prominent shifts to wetter conditions at c. 7500, 4300–4200, 3700–3500 and 2800–2400 cal. yr BP. The most distinct drier phases start at c. 4500 and 3250 cal. yr BP. [ABSTRACT FROM AUTHOR]

To investigate the Holocene vegetation history and shoreline displacement along the southeastern Swedish coast, two radiocarbon dated pollen, macrofossil and mineral magnetic sequences were studied in the western Blekinge coast: Hunnemara Lake and Smygen Bay. Both pollen records show mosaic vegetation with grasslands, heaths and woodlands prior to 11 300 cal. BP. Pinus -dominated mixed forest was initially established by 11 000 cal. BP. By 10 000 cal. BP, mixed forest with higher species diversity was fully established. Expansion of broad-leaved trees began at about 8600 cal. BP, indicating the onset of the mid-Holocene thermal maximum in Scandinavia. Following the Ulmus decline 5800 cal. BP, the regional forest became much more open due to increased human disturbance. Both basins were isolated during the period of 11 300 – 11 000 cal. BP, and subsequently in contact with the Ancylus Lake between 10 700 and 9800 cal. BP. Low abundance of brackish-water diatoms at Smygen suggests that this basin was connected with the Baltic Sea between 9800 and 8600 cal. BP, corresponding to the Early Littorina Sea phase. Hunnemara was isolated during this period. The two basins were in turn flooded at 8600 and 8300 cal. BP, as a result of global sea-level rise. A sedimentary hiatus (8300 – 7500 cal. BP) was present at Hunnemara, probably caused by a rapid sea-level rise related to global meltwater pulse 3. Aquatic macrofossil and mineral magnetic proxies reveal several minor transgressions at both sites, probably regulated by centennial-scale variations in regional storminess. Hunnemara was isolated from the Baltic Basin by 3100 cal. BP, concurrent with a lowering of the sea level at Smygen. [ABSTRACT FROM AUTHOR]

Cores of peat taken from two raised bogs in the near-coastal part of Halland, SW Sweden, were examined for their content of wind-transported clastic material. The Boarps Mosse core has a length of 262 cm and covers the last 2850 years (age model based on three radiocarbon dates), while the Hyltemossen core has a length of 347 cm and records the last 7000 years (age model based on eight radiocarbon dates). The peat contains aeolian quartz silt and sand (from trace amount to more than 10 weight % of the dry peat sample), and the grain-size composition of the minerogenic sediment indicates that the material is composed of both far-travelled dust and local wind-eroded silt and sand. Grains larger than 0.2 mm are present in many intervals and probably record niveo-aeolian transport in connection with severe snowstorms. A systematic count of quartz grains between 0.2-0.35 mm and larger than 0.35 mm was carried out to determine variations in aeolian sand influx (ASI) and winter wind climate with time. The Boarps Mosse site is situated in a hilly terrain and is primarily open to southerly and northerly winds, while the Hyltemossen site is situated in a more flat landscape open to winds from most directions. Furthermore, at Boarps Mosse dense forest stands seem to have protected the site from significant aeolian sand influx until about AD 1000, while aeolian sand influx apparently was less influenced by local forest development at Hyltemossen. However, using periods with low ASI values as marker horizons it is possible to identify a number of periods of high ASI values during the last 2500 years. These periods, which probably record high winter storminess, are dated to 130, 300, 400, 475, (700), 900, (1000), (1100), (1150), (1350), (1450), 1675, (1800), 1875, 1950-2000, (2050), 2150, 2225 and (2300) cal. yr BP. In addition, the Hyltemossen site documents peak storminess at 2450, 2725, 2850-3050, 3275, 3675, 4100-4200, 4550, 4900, 5100-5200 and 5450 5700 cal. yr BP. Most of the aeolian activity phases in Halland correlate with well-known cold periods in northwest Europe, suggesting a link between winter storminess in southern Scandinavia and expansion of the polar vortex. [ABSTRACT FROM AUTHOR]

Palaeomagnetic analyses were conducted on two varved lake-sediment sequences in northern Sweden. The magnetic properties of the sediment sequences are dominated by stable single-domain magnetite with characteristics typical of bacterial magnetosomes. Alternating field demagnetization measurements indicate that the single-domain magnetite is the dominant carrier of a stable natural remanent magnetization. Temporal variations in inclination and declination were obtained from a total of four cores and the data points were stacked according to their independent calendar-year (varve) ages. Statistically significant patterns in inclination and declination form a regional palaeomagnetic secular variation (PSV) curve, which possesses features that are identical in form to the UK Holocene PSV master curve. However, the calibrated radiocarbon ages of UK features identified prior to 1500 BC are approximately 500 years older than their Swedish varve-dated equivalents, which points to dating errors and/or drifting of the geomagnetic field. The sediments meet the uniformity criteria proposed for palaeointensity reconstruction and estimates of relative geomagnetic field intensity are calibrated against global dipole-moment compilations. A calculated nuclide production curve is derived from the reconstructed geomagnetic field intensity, which empirically demonstrates the dominant modulation of cosmogenic nuclide production by dipole-moment between 5000 BC and AD 1500. [ABSTRACT FROM AUTHOR]

The oxygen-isotope composition of local precipitation (δ[sup 18]O[sub P]) is reconstructed from carbonate lake-sediment components in a sediment core covering the last 10000 calendar years from Lake Tibetanus, a small, hydrologically open, groundwater-fed lake in the Abisko area, northern Sweden. Comparison of the δ[sup 18]O[sub P] history with a pollen-based palaeotemperature record from the same core clearly reveals pronounced deviations from the normally expected temporal δ[sup 18]O[sub P]-temperature relation (so-called 'Dansgaard relation') that may be a function of changing oceanicity. The transition from relatively moist, maritime conditions in the early Holocene to a much drier climate after 6500 cal. BP is reflected by major changes in forest extent and composition as recorded by pollen and plant macrofossil data. At the time of maximum influence of westerly air-mass circulation (high zonal index) c. 9500 cal. BP, brought about by high summer insolation and enhanced meridional pressure gradients, δ[sup 18]O[sub P] at Lake Tibetanus was about 2‰ higher than would be predicted by the modern isotope-temperature relation. The occurrence of long-term changes in δ[sup 18]O[sub P]-temperature relations, which are more sensitive measures of palaeoclimate than either δ[sup 18]O[sub P] or temperature alone, needs to be taken into account when extracting palaeoclimatic information from continental oxygen-isotope records. [ABSTRACT FROM AUTHOR]

Detailed mineral magnetic measurements were conducted on a 9000-year varved lake sediment sequence in northern Sweden (Lake Sarsjön). The results demonstrate that the paramagnetic susceptibility reflects the concentration of detrital minerogenic material in the lake sediments, which is controlled to a large extent by the intensity of the spring snow melt. In contrast, the concentration of ferrimagnetic magnetite (reflected by initial magnetic susceptibility and magnetic hysteresis parameters) is positively correlated to the concentration of organic carbon, which is most likely of an autochthonous origin. This magnetite has magnetic properties that are characteristic of stable single-domain magnetite grains produced by magnetotactic bacteria. The paramagnetic susceptibility record clearly points to a climatic excursion in the early Holocene between 6100 ± 174 bc and 5700 ± 167 bc, which can be correlated to an d 18 O excursion (a cold event) in the Greenland ice cores and lake sediments in southern Germany, and also to a short period of increased glacial activity in Scandinavia. The middle Holocene (4000–1760 bc) is characterized by sediment with a low concentration of detrital minerals and a high organic carbon content, whereas the late Holocene (1760 bc–ad 1918) is marked by more frequent and intense periods of detrital sedimentation. [ABSTRACT FROM AUTHOR]

Fluctuations of the altitudinal position and composition of the timberline in northern Sweden have occurred in response to climatic changes following deglaciation (c. 8800 yrs BP). In this study a soil sequence of predominantly Podzols (Spodosols) was analysed to determine if the soil profiles located above the present timberline were actively forming in the low-alpine environment, or whether they represent relict features of a once stronger pedogenic regime. The results of the soil analysis indicate a relatively uniform parent material with increasing fines near the surface reflecting aeolian influxed sediment. The soil profiles located above the timberline are generally characterized by darker colours, although with a lower accumulation of organic carbon and either similar or higher iron and aluminium in the spodic horizon than are found in the profiles located below the timberline. The alpine Podzols, generally located in protected swales, are quite distinct from Brunisols (Inceptisols) and Regosols (Entisols) found in slopes and swells on the predominantly undulating morainic and glaciofluvial landscape. This appears to indicate that Spodosols located above the present timberline are not actively being modified under the present low-alpine environmental conditions, but rather were initiated during the Atlantic Chronozone when a dwarf or stunted forest extended to approximately 900 m above sea level. [ABSTRACT FROM AUTHOR]