A selection from Stockholm University publication database

• Accelerating climate and land-use pressure on environment and people in Arctic Sweden: challenges for sustainable land use planning

  Gunhild Rosqvist (et al.).

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• An evaluation of a chironomid-based summer temperature reconstruction from west 1 central Sweden covering the last millennium

  Annika Berntsson (et al.).

  Here we present a lake sediment study from west central Sweden that covers the last thousand years. The study site Lake Spåime is a shallow, hydrologically open lake situated above the present tree line. We applied chironomid analysis with the aim to reconstruct mean July air temperature at a high temporal resolution and we evaluated our reconstruction with significance tests and comparison with observed meteorological data. We examined the relationship between changes in chironomid-inferred July temperature, isotope hydrology and minerogenic detrital input. We also assessed the influence of running water and semi-terrestrial/terrestrial chironomids. The inferred July air temperatures ranged from 8.5˚C to 11.6˚C (mean 9.6˚C) over the past millennium. The temperatures inferred with running water- and terrestrial taxa removed was similar, but with a 0.6 ˚C higher amplitude. The results of significance testing were inconclusive. Comparison with meteorological data showed that the chironomid-based July air temperatures were similar during the last 110 years. Individual years when chironomid-inferred July air temperatures were lower than the instrumental data were characterized by low June air temperatures and high amounts of winter precipitation. From this, we assume that late snowmelt led to cool melt water input in July which in turn caused a decoupling between water and air temperatures causing too low inferred temperatures. Inferred July temperatures show similarities and discrepancies with reconstructions derived from other proxies in the region, such as tree-ring and sea surface temperature records, and fail to reconstruct the cold summer conditions characteristic of the years between AD 1650 and 1750. We conclude that the Spåime July temperature reconstruction was partly biased, possibly because of major changes in the Spåime catchment system that influenced the chironomids. For example, changes in hydrology caused by shifts in seasonality and amount of precipitation may have triggered changes in sediment erosion and deposition rates, affecting the chironomid composition to a larger extent than mean July air temperatures. Future challenges include examination of the temperature sensitivity of chironomid taxa and continued critical assessment of individual chironomid inferred temperature reconstructions, not only against other temperature proxies but also against proxies for variations in hydrology.

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• Climatic impacts on an Arctic lake since 1300 AD: a multi-proxy lake sediment reconstruction from Prins Karls Forland, Svalbard

  2023. L. C. Orme (et al.). Journal of Paleolimnology 69 (3), 249-266

  Article

  On the remote Arctic archipelago of Svalbard, there is increasing evidence of environmental impacts from climate change. The analysis of lake sedimentary records can be used to assess how strongly these recent changes have altered lake ecosystems. Sediments deposited during the last millennium from Lake Blokkvatnet, Prins Karls Forland, were analysed using a multiproxy approach, including stable isotope and X-ray fluorescence analysis. The results were interpreted as reflecting variability of (1) soil organic matter inwash, and potentially catchment and lake primary production, and (2) catchment weathering and erosion. Organic content began increasing after 1920 AD to the present, likely in response to warming. Earlier peaks of a similar magnitude occurred on three occasions since 1300 AD, with evidence indicating that these may have coincided with multidecadal-scale periods with higher temperatures, reduced sea ice and negative phases of the North Atlantic Oscillation. Catchment weathering and fluvial erosion began to increase around 1800 AD and peaked during the early twentieth century, potentially due to rising temperatures in autumn and winter causing increased liquid water availability. The records suggest that similar levels of erosion and weathering occurred between approximately 1300 and 1600 AD, spanning the transition from the Medieval Climate Anomaly to the Little Ice Age. 

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• Catchment-scale microbial sulfate reduction (MSR) of acid mine drainage (AMD) revealed by sulfur isotopes

  2022. Sandra Fischer (et al.). Environmental Pollution 292, Part B

  Article

  Laboratory experiments and point observations, for instance in wetlands, have shown evidence that microbial sulfate reduction (MSR) can lower sulfate and toxic metal concentrations in acid mine drainage (AMD). We here hypothesize that MSR can impact the fate of AMD in entire catchments. To test this, we developed a sulfur isotope fractionation and mass-balance method, and applied it at multiple locations in the catchment of an abandoned copper mine (Nautanen, northern Sweden). Results showed that MSR caused considerable, catchment-scale immobilization of sulfur corresponding to a retention of 27 ± 15% under unfrozen conditions in the summer season, with local values ranging between 13 ± 10% and 53 ± 18%. Present evidence of extensive MSR in Nautanen, together with previous evidence of local MSR occurring under many different conditions, suggest that field-scale MSR is most likely important also at other AMD sites, where retention of AMD may be enhanced through nature-based solutions. More generally, the developed isotope fractionation analysis scheme provides a relatively simple tool for quantification of spatio-temporal trends in MSR, answering to the emerging need of pollution control from cumulative anthropogenic pressures in the landscape, where strategies taking advantage of MSR can provide viable options.

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• Direct photogrammetry with multispectral imagery for UAV-based snow depth estimation

  2022. Kathrin Maier (et al.). ISPRS journal of photogrammetry and remote sensing (Print) 186, 1-18

  Article

  More accurate snow quality predictions are needed to economically and socially support communities in a changing Arctic environment. This contrasts with the current availability of affordable and efficient snow monitoring methods. In this study, a novel approach is presented to determine spatial snow depth distribution in challenging alpine terrain that was tested during a field campaign performed in the Tarfala valley, Kebnekaise mountains, northern Sweden, in April 2019. The combination of a multispectral camera and an Unmanned Aerial Vehicle (UAV) was used to derive three-dimensional (3D) snow surface models via Structure from Motion (SfM) with direct georeferencing. The main advantage over conventional photogrammetric surveys is the utilization of accurate Real-Time Kinematic (RTK) positioning which enables direct georeferencing of the images, and therefore eliminates the need for ground control points. The proposed method is capable of producing high-resolution 3D snow-covered surface models (<7 cm/pixel) of alpine areas up to eight hectares in a fast, reliable and affordable way. The test sites’ average snow depth was 160 cm with an average standard deviation of 78 cm. The overall Root-Mean-Square Errors (RMSE) of the snow depth range from 11.52 cm for data acquired in ideal surveying conditions to 41.03 cm in aggravated light and wind conditions. Results of this study suggest that the red components in the electromagnetic spectrum, i.e., the red, red edge, and near-infrared (NIR) band, contain the majority of information used in photogrammetric processing. The experiments highlighted a significant influence of the multi-spectral imagery on the quality of the final snow depth estimation as well as a strong potential to reduce processing times and computational resources by limiting the dimensionality of the imagery through the application of a Principal Component Analysis (PCA) before the photogrammetric 3D reconstruction. The proposed method is part of closing the scale gap between discrete point measurements and regional-scale remote sensing and complements large-scale remote sensing data and snow model output with an adequate validation source.

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• Impacts of climate warming on reindeer herding require new land-use strategies

  2022. Gunhild C. Rosqvist, Niila Inga, Pia Eriksson. Ambio 51 (5), 1247-1262

  Article

  Climate in the Arctic has warmed at a more rapid pace than the global average over the past few decades leading to weather, snow, and ice situations previously unencountered. Reindeer herding is one of the primary livelihoods for Indigenous peoples throughout the Arctic. To understand how the new climate state forces societal adaptation, including new management strategies and needs for preserved, interconnected, undisturbed grazing areas, we coupled changes in temperature, precipitation, and snow depth recorded by automatic weather stations to herder observations of reindeer behaviour in grazing areas of the Laevas Sami reindeer herding community, northern Sweden. Results show that weather and snow conditions strongly determine grazing opportunities and therefore reindeer response. We conclude that together with the cumulative effects of increased pressures from alternative land use activities, the non-predictable environmental conditions that are uniquely part of the warming climate seriously challenge future reindeer herding in northern Sweden.

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• Microbial Sulfate Reduction (MSR) as a Nature-Based Solution (NBS) to Mine Drainage: Contrasting Spatiotemporal Conditions in Northern Europe

  2022. Sandra Fischer (et al.). Water resources research 58 (4)

  Article

  An emerging solution in mine waste remediation is the use of biological processes, such as microbial sulfate reduction (MSR), to immobilize metals, reducing their bioavailability and buffering the pH of acid mine drainage. Apart from laboratory tests and local observations of natural MSR in, for example, single wetlands, little is known about spatiotemporal characteristics of freshwater MSR from multiple locations within entire hydrological catchments. We here applied an isotopic fractionation (δ34S values in SO42−) and a Monte Carlo-based mixing analysis scheme to detect MSR and its variation across two major mining regions (Imetjoki, Sweden and Khibiny, Russia) in the Arctic part of Europe under different seasonal conditions. Results indicate a range of catchment-scale MSR values in the Arctic of ∼5%–20% where the low end of the range was associated with the non-vegetated, mountainous terrain of the Khibiny catchment, having low levels of dissolved organic carbon (DOC). The high end of the range was related to vegetated conditions provided by the Imetjoki catchment that also contains wetlands, lakes, and local aquifers. These prolong hydrological residence times and support MSR hot spots reaching values of ∼40%. The present results additionally show evidence of MSR persistence over different seasons, indicating large potential, even under relatively cold conditions, of using MSR as part of nature-based solutions to mitigate adverse impacts of (acid) mine drainage. The results call for more detailed investigations regarding potential field-scale correlations between MSR and individual landscape and hydroclimatic characteristics, which, for example, can be supported by the isotopic fractionation and mixing scheme utilized here.

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• Reindeer husbandry and climate change: Challenges for adaptation

  2022. Sirpa Rasmus (et al.). Reindeer Husbandry and Global Environmental Change, 99-117

  Chapter

  Reindeer and reindeer herders in the circumpolar North are exposed to harsh and often hard-to-predict weather conditions. Herding communities have previously adapted to these external disturbances by flexible pasture use, seasonal mobility, changing herding practices, diversifying livelihoods and continuously developing traditional or experience-based knowledge. However, few places in the world experience ongoing climate change as clearly and rapidly as the high northern latitudes. The effects of climate change and increased frequency of extreme weather events are transforming the biophysical environment of reindeer husbandry. These changes challenge the adaptive capacity of herders who operate in a landscape they share with, and which is highly impacted by, other forms of land use. Thus, sociopolitical factors play a major role in developing adaptation strategies that are perceived as desirable and possible. This chapter summarizes the observed and expected changes in climate and impacts thereof within the reindeer herding area (RHA) of northern Fennoscandia. The chapter further presents a range of strategies adopted by herders to cope with adverse, seasonal weather conditions and indirect impacts of climate change. Finally, it situates these strategies in the context of more proactive and institutional adaptation.

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• A first continuous three-year temperature record from the dimictic arctic-alpine Lake Tarfala, northern Sweden

  2021. Nina Kirchner (et al.). Arctic, Antarctic and Alpine research 53 (1), 69-79

  Article

  Arctic lakes are exposed to warming during increasingly longer ice-free periods and, if located in glaciated areas, to increased inflow of meltwater and sediments. However, direct monitoring of how such lakes respond to changing environmental conditions is challenging not only because of their remoteness but also because of the scarcity of present and previously observed lake states. At the glacier-proximal Lake Tarfala in the Kebnekaise Mountains, northern Sweden, temperatures throughout the water column at its deepest part (50 m) were acquired between 2016 and 2019. This three-year record shows that Lake Tarfala is dimictic and is overturning during spring and fall, respectively. Timing, duration, and intensity of mixing processes, as well as of summer and winter stratification, vary between years. Glacial meltwater may play an important role regarding not only mixing processes but also cooling of the lake. Attribution of external environmental factors to (changes in) lake mixing processes and thermal states remains challenging owing to for example, timing of ice-on and ice-off but also reflection and absorption of light, both known to play a decisive role for lake mixing processes, are not (yet) monitored in situ at Lake Tarfala.

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• Reindeer husbandry in peril?-How extractive industries exert multiple pressures on an Arctic pastoral ecosystem

  2021. Christian Fohringer (et al.). People and Nature 3 (4), 872-886

  Article

  Environmental changes and their consequences on biodiversity are known to have far-reaching effects on the resilience of animal populations and associated livelihoods around the world. To counteract negative demographic and economic effects on pastoralism, knowledge about the historical and current status of the environment is essential. In this study, we show how extractive industries, especially large-scale mining, induced a cascade of land conversions which are affecting animal populations and pastoralists' adaptive responses in northern Sweden. We examine social-ecological vulnerability in Arctic reindeer husbandry by integrating herders' knowledge, population statistics for semi-domesticated reindeer Rangifer t. tarandus, public data on socio-economic variables and geospatial tools. We determine that approximately 34% of Laevas reindeer herding community's grazing grounds are functionally unavailable to reindeer at present due to the accumulation of multiple competing land use pressures. Reindeer numbers currently only remain stable due to increased management efforts. Moreover, we identified current hotspots of high cumulative impact and mineral exploration as the spatially dominating land use factor in this area. Our approach and results provide new insights for scientifically robust cumulative impact assessments of anthropogenic stressors by creating a baseline of current developments via a combination of reindeer herder's knowledge with historical data of trends and extents of human activity over the last century.

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• Social-ecological-technological systems consequences of mining: An analytical framework for more holistic impact assessments

  2021. Annika E. Nilsson, Dag Avango, Gunhild Rosqvist. The Extractive Industries and Society 8 (4)

  Article

  Understanding the impacts of extractive industries on sustainable development requires analyzing them as part of dynamic social-ecological-technological systems. Building on insights from studies of social-ecological systems and socio-technical systems, as well as fieldwork on the impacts of mining in the Nordic Arctic, this article presents an analytical framework for co-production of knowledge about the role of industrial or infrastructure projects for regional development. We use this framework to analyze Swedish mining policy, assessment guidelines, and environmental impact assessments for three mining projects in Arctic Sweden. We conclude that Swedish mining policy and guidelines for impact assessments neglect key aspects of social-ecologicaltechnological systems, including the impacts of climate change, and treat many social aspects of sustainable development in a cursory manner. We suggest that more systematic analysis of the dynamics of social-ecologicaltechnological systems would facilitate more transparent decision making and help identify the potential role of proposed mining projects in pathways towards sustainable development in northern regions.

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• Disproportionate Water Quality Impacts from the Century-Old Nautanen Copper Mines, Northern Sweden

  2020. Sandra Fischer (et al.). Sustainability 12 (4)

  Article

  Pollution from small historical mining sites is usually overlooked, in contrast to larger ones. Especially in the Arctic, knowledge gaps remain regarding the long-term mine waste impacts, such as metal leakage, on water quality. We study the small copper (Cu) mines of Nautanen, northern Sweden, which had been in operation for only six years when abandoned approximately 110 years ago in 1908. Measurements from field campaigns in 2017 are compared to synthesized historical measurement data from 1993 to 2014, and our results show that concentrations of Cu, Zn, and Cd on-site as well as downstream from the mining site are order(s) of magnitude higher than the local background values. This is despite the small scale of the Nautanen mining site, the short duration of operation, and the long time since closure. Considering the small amount of waste produced at Nautanen, the metal loads from Nautanen are still surprisingly high compared to the metal loads from larger mines. We argue that disproportionately large amounts of metals may be added to surface water systems from the numerous small abandoned mining sites. Such pollution loads need to be accounted for in sustainable assessments of total pollutant pressures in the relatively vulnerable Arctic environment.

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• High-resolution bathymetric mapping reveals subaqueous glacial landforms in the Arctic alpine lake Tarfala, Sweden

  2019. Nina Kirchner (et al.). Journal of Quaternary Science 34 (6), 452-462

  Article

  In Arctic alpine regions, glacio-lacustrine environments respond sensitively to variations in climate conditions, impacting, for example,glacier extent and rendering former ice-contact lakes into ice distal lakes and vice versa. Lakefloors may hold morphological records of past glacier extent, but remoteness and long periods of ice cover on such lakes make acquisition of high-resolution bathymetric datasets challenging. Lake Tarfala and Kebnepakte Glacier, located in the Kebnekaise mountains, northern Sweden, comprise a small, dynamic glacio-lacustrine system holding a climate archive that is not well studied. Using an autonomous surface vessel, a high-resolution bathymetric dataset for Lake Tarfala was acquired in 2016, from which previously undiscovered end moraines and a potential grounding line feature were identified. For Kebnepakte Glacier, structure-from-motion photogrammetry was used to reconstruct its shape from photographs taken in 1910 and 1945. Combining these methods connects the glacial landform record identified at the lakefloor with the centennial-scale dynamic behaviour of Kebnepakte Glacier. During its maximum 20(th) century extent, attained c. 1910, Kebnepakte Glacier reached far into Lake Tarfala, but had retreated onto land by 1945, at an average of 7.9 m year(-1).

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• A late Holocene pollen record from proglacial Oblong Tarn, Mount Kenya

  2017. Colin J. Courtney Mustaphi (et al.). PLOS ONE 12 (9)

  Article

  High-elevation ecosystems, such as those on Mount Kenya are undergoing significant changes, with accelerated glacial ice losses over the twentieth century creating new space for alpine plants to establish. These ecosystems respond rapidly to climatic variability and within decades of glacial retreat, Afroalpine pioneering taxa stabilize barren land and facilitate soil development, promoting complex patches of alpine vegetation. Periglacial lake sediment records can be used to examine centennial and millennial scale variations in alpine and montane vegetation compositions. Here we present a 5300-year composite pollen record from an alpine tarn (4370 m asl) in the Hausberg Valley of Mount Kenya. Overall, the record shows little apparent variation in the pollen assemblage through time with abundant montane forest taxa derived and transported from mid elevations, notably high abundances of aerophilous Podocarpus pollen. Afroalpine taxa included Alchemilla, Helichrysum and Dendrosenecio-type, reflecting local vegetation cover. Pollen from the ericaceous zone was present throughout the record and Poaceae percentages were high, similar to other high elevation pollen records from eastern Africa. The Oblong Tarn record pollen assemblage composition and abundances of Podocarpus and Poaceae since the late Holocene (similar to 4000 cal yr BP-present) are similar to pollen records from mid-to-high elevation sites of nearby high mountains such as Mount Elgon and Kilimanjaro. These results suggest a significant amount of uphill pollen transport with only minor apparent variation in local taxa. Slight decreasing trends in alpine and ericaceous taxonomic groups show a long-term response to global late Holocene cooling and a step decrease in rate of change estimated from the pollen assemblages at 3100 cal yr BP in response to regional hydroclimatic variability. Changes in the principal component axis scores of the pollen assemblage were coherent with an independent mid-elevation temperature reconstruction, which supported the strong influence of uphill pollen transport from montane forest vegetation and association between temperatures and montane vegetation dynamics. Pollen accumulation rates showed some variability related to minerogenic sediment input to the lake. The Oblong Tarn pollen record provides an indication of long term vegetation change atop Mount Kenya showing some decreases in local alpine and ericaceous taxa from 5300-3100 cal yr BP and minor centennial-scale variability of montane taxa from mid elevation forests. The record highlights potentials, challenges and opportunities for the use of proglacial lacustrine sediment to examine vegetation change on prominent mountain massifs.

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• Late Holocene glacier reconstruction reveals retreat behind present limits and two-stage Little Ice Age on subantarctic South Georgia

  2017. Willem G. M. van der Bilt (et al.). Journal of Quaternary Science 32 (6), 888-901

  Article

  Observational data show that climate in the Southern Ocean region is rapidly changing. However, past the instrumental period, our understanding of climate variability in the region is limited by a scarcity of highresolution palaeoclimate records. Alpine glaciers, present on many Southern Ocean islands, may provide such data because changes in their mass balance, extent and erosion rates often mark a response to climate shifts. Rock flour, the fine-grained fraction of the glacial erosion process, is suspended in meltwater streams and transferred into the sediments of downstream lakes, continuously recording glacier variations. Here, we utilize this relationship to present a reconstruction of the Late Holocene glacier history of subantarctic South Georgia, using sediments from the glacier-fed Middle Hamberg Lake. To fingerprint a glacial erosion/size signal, we used titanium counts, validated against changes in sediment density and grain size, allowing a continuous reconstruction of glacier variations over the past similar to 1250 years. Together with local moraine evidence and supporting evidence from other Southern Hemisphere glaciers on New Zealand and in Patagonia, our findings reveal a series of consecutively diminishing Late Holocene advances. In addition to a glacier maximum before 1250 cal a BP, these include a twostage Litle Ice Age with advances around 300 and 120 cal a BP, in line with evidence from southern Patagonia. In addition, we present evidence for an unreported retreat behind present limits around 500 cal BP.

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• Changing Arctic snow cover: A review of recent developments and assessment of future needs for observations, modelling, and impacts

  2016. Stef Bokhorst (et al.). Ambio 45 (5), 516-537

  Article

  Snow is a critically important and rapidly changing feature of the Arctic. However, snow-cover and snowpack conditions change through time pose challenges for measuring and prediction of snow. Plausible scenarios of how Arctic snow cover will respond to changing Arctic climate are important for impact assessments and adaptation strategies. Although much progress has been made in understanding and predicting snow-cover changes and their multiple consequences, many uncertainties remain. In this paper, we review advances in snow monitoring and modelling, and the impact of snow changes on ecosystems and society in Arctic regions. Interdisciplinary activities are required to resolve the current limitations on measuring and modelling snow characteristics through the cold season and at different spatial scales to assure human well-being, economic stability, and improve the ability to predict manage and adapt to natural hazards in the Arctic region.

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• Deglaciation of Fennoscandia

  2016. Arjen P. Stroeven (et al.). Quaternary Science Reviews 147 (SI), 91-121

  Article

  To provide a new reconstruction of the deglaciation of the Fennoscandian Ice Sheet, in the form of calendar-year time-slices, which are particularly useful for ice sheet modelling, we have compiled and synthesized published geomorphological data for eskers, ice-marginal formations, lineations, marginal meltwater channels, striae, ice-dammed lakes, and geochronological data from radiocarbon, varve, optically-stimulated luminescence, and cosmogenic nuclide dating. This is summarized as a deglaciation map of the Fennoscandian Ice Sheet with isochrons marking every 1000 years between 22 and 13 cal kyr BP and every hundred years between 11.6 and final ice decay after 9.7 cal kyr BP. Deglaciation patterns vary across the Fennoscandian Ice Sheet domain, reflecting differences in climatic and geomorphic settings as well as ice sheet basal thermal conditions and terrestrial versus marine margins. For example, the ice sheet margin in the high-precipitation coastal setting of the western sector responded sensitively to climatic variations leaving a detailed record of prominent moraines and other ice-marginal deposits in many fjords and coastal valleys. Retreat rates across the southern sector differed between slow retreat of the terrestrial margin in western and southern Sweden and rapid retreat of the calving ice margin in the Baltic Basin. Our reconstruction is consistent with much of the published research. However, the synthesis of a large amount of existing and new data support refined reconstructions in some areas. For example, the LGM extent of the ice sheet in northwestern Russia was located far east and it occurred at a later time than the rest of the ice sheet, at around 17-15 cal kyr BP. We also propose a slightly different chronology of moraine formation over southern Sweden based on improved correlations of moraine segments using new LiDAR data and tying the timing of moraine formation to Greenland ice core cold stages. Retreat rates vary by as much as an order of magnitude in different sectors of the ice sheet, with the lowest rates on the high-elevation and maritime Norwegian margin. Retreat rates compared to the climatic information provided by the Greenland ice core record show a general correspondence between retreat rate and climatic forcing, although a close match between retreat rate and climate is unlikely because of other controls, such as topography and marine versus terrestrial margins. Overall, the time slice reconstructions of Fennoscandian Ice Sheet deglaciation from 22 to 9.7 cal kyr BP provide an important dataset for understanding the contexts that underpin spatial and temporal patterns in retreat of the Fennoscandian Ice Sheet, and are an important resource for testing and refining ice sheet models.

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• Dye tracing to determine flow properties of hydrocarbon-polluted Rabots glaciar, Kebnekaise, Sweden

  2015. Caroline C. Clason (et al.). Hydrology and Earth System Sciences 19 (6), 2701-2715

  Article

  Over 11 000 L of kerosene was deposited on the surface of Rabots glaciar on the Kebnekaise Massif, northern Sweden, following the crash of a Royal Norwegian Air Force aircraft in March 2012. An environmental monitoring programme was subsequently commissioned, including a series of dye tracing experiments during the 2013 melt season, conducted to investigate the transport of pollutants through the glacier hydrological system. This experimental set-up provided a basis from which we could gain new insight into the internal hydrological system of Rabots glaciar. Results of dye tracing experiments reveal a degree of homogeneity in the topology of the drainage system throughout July and August, with an increase in efficiency as the season progresses, as reflected by decreasing temporary storage and dispersivity. Early onset of melting likely led to formation of an efficient, discrete drainage system early in the melt season, subject to decreasing sinuosity and braiding as the season progressed. Four distinct meltwater flow regimes are identified to summarize the temporal and spatial evolution of the system. Analysis of turbidity-discharge hysteresis further supports the formation of discrete, efficient drainage, with clockwise diurnal hysteresis suggesting easy mobilization of readily available sediments in channels. Dye injection immediately downstream of the pollution source zone reveals prolonged storage of dye followed by fast, efficient release. Twinned with a low dye recovery, and supported by sporadic detection of hydrocarbons in the proglacial river, we suggest that meltwater, and thus pollutants in solution, may be released periodically through an efficient, and likely pressurized, hydrological system within the upper reaches of the glacier.

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• Isotopic investigation of runoff generation in a glacierized catchment in northern Sweden

  2014. Helen E. Dahlke (et al.). Hydrological Processes 28 (3), 1383-1398

  Article

  In this study, summer rainfall contributions to streamflow were quantified in the sub-arctic, 30% glacierized Tarfala (21.7km(2)) catchment in northern Sweden for two non-consecutive summer sampling seasons (2004 and 2011). We used two-component hydrograph separation along with isotope ratios (O-18 and D) of rainwater and daily streamwater samplings to estimate relative fraction and uncertainties (because of laboratory instrumentation, temporal variability and spatial gradients) of source water contributions. We hypothesized that the glacier influence on how rainfall becomes runoff is temporally variable and largely dependent on a combination of the timing of decreasing snow cover on glaciers and the relative moisture storage condition within the catchment. The results indicate that the majority of storm runoff was dominated by pre-event water. However, the average event water contribution during storm events differed slightly between both years with 11% reached in 2004 and 22% in 2011. Event water contributions to runoff generally increased over 2011 the sampling season in both the main stream of Tarfala catchment and in the two pro-glacial streams that drain Storglaciaren (the largest glacier in Tarfala catchment covering 2.9km(2)). We credit both the inter-annual and intra-annual differences in event water contributions to large rainfall events late in the summer melt season, low glacier snow cover and elevated soil moisture due to large antecedent precipitation. Together amplification of these two mechanisms under a warming climate might influence the timing and magnitude of floods, the sediment budget and nutrient cycling in glacierized catchments.

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• Late-Holocene temperature and precipitation changes in Vindelfjallen, mid-western Swedish Lapland, inferred from chironomid and geochemical data

  2014. Annika Berntsson, Gunhild C. Rosqvist, Gaute Velle. The Holocene 24 (1), 78-92

  Article

  In this article, we present results from a palaeolimnological study from Lake Vuoksjavratje in the mountain tundra region in the Vindelfjallen Mountains, northwest Sweden. We suggest that the influence of precipitation may be one of the factors causing discrepancies between chironomid-based late-Holocene July temperature (JulyT) reconstructions from Fennoscandia. We combine quantitative temperature reconstruction using chironomids for the last 5100 years with qualitative analysis of chironomid composition and geochemical analyses, such as x-ray fluorescence (XRF), total organic carbon (TOC) and C/N analysis. The studied sequence is dated by Pb-210, Cs-137 and 11 C-14 datings from terrestrial macrofossils. The aim of the study was to use chironomids to reconstruct late-Holocene summer temperature variation on a multi-centennial to centennial timescale and to use geochemical data to identify periods during which the changes in chironomid composition might have been forced by environmental variables other than temperature, such as within lake processes or precipitation. Based on ordination techniques, and a comparison between chironomid-inferred JulyTs and changes in minerogenic sedimentation with regional temperature and wetness records, it is concluded that the JulyT signal was modulated by precipitation. The proxies indicate that both JulyT and annual precipitation have influenced the chironomid communities in Lake Vuoksjavratje, and that catchment-related processes caused by enhanced precipitation have overridden the summer temperature signal between 3000 and 2200 cal. yr BP, and between 1050 and 100 cal. yr BP.

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• Particle Size Sampling and Object-Oriented Image Analysis for Field Investigations of Snow Particle Size, Shape, and Distribution

  2013. Susanne Ingvander (et al.). Arctic, Antarctic and Alpine research 45 (3), 330-341

  Article

  Snow particle size is an important parameter strongly affecting snow cover broadband albedo from seasonally snow covered areas and ice sheets. It is also important in remote sensing analyses because it influences the reflectance and scattering properties of the snow. We have developed a digital image processing method for the capture and analysis of data of snow particle size and shape. The method is suitable for quick and reliable data capture in the field. Traditional methods based on visual inspection of samples have been used but do not yield quantitative data. Our method provides an alternative to both simpler and more complex methods by providing a tool that limits the subjective effect of the visual analysis and provides a quantitative particle size distribution. The method involves image analysis software and field efficient instrumentation in order to develop a complete process-chain easily implemented under field conditions. The output from the analysis is a two-dimensional analysis of particle size, shape, and distributions for each sample. The results of the segmentation process were validated against manual delineation of snow particles. The developed method improves snow particle analysis because it is quantitative, reproducible, and applicable for different types of field sites.

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• Seasonal and interannual variability of elemental carbon in the snowpack of Storglaciaren, northern Sweden

  2013. Susanne Ingvander (et al.). Annals of Glaciology 54 (62), 50-58

  Article

  We studied the variability of elemental carbon (EC) over 3 years (2009-11) in the winter snowpack of Storglaciaren, Sweden. The goal of this study was to relate the seasonal variation in EC to specific snow accumulation events in order to improve understanding of how different atmospheric circulation patterns control the deposition of EC. Specifically, we related meteorological parameters (e.g. wind direction, precipitation) to snow physical properties, EC content, stable-isotope 8180 ratios and anion concentrations in the snowpack. The distribution of EC in the snowpack varied between years. Low EC contents corresponded to a predominance of weather systems originating in the northwest, i.e. North Atlantic. Analysis of single layers within the snowpacks showed that snow layers enriched in heavy isotopes coincided predominantly with low EC contents but high chloride and sulfate concentration. Based on this isotopic and geochemical evidence, snow deposited during these events had a strong oceanic, i.e. North Atlantic, imprint. In contrast, snow layers with high EC content coincided with snow layers depleted in heavy isotopes but high anion concentrations, indicating a more continental source of air masses and origin of EC from industrial emissions.

  Read more about Seasonal and interannual variability of elemental carbon in the snowpack of Storglaciaren, northern Sweden

• Shifts in precipitation during the last millennium in northern Scandinavia from lacustrine isotope records

  2013. Gunhild C. Rosqvist (et al.). Quaternary Science Reviews 66, 22-34

  Article

  Here we present delta P-18(diatom) data from two high-latitude lakes; one has short residence time and a water isotopic composition (delta O-18(lake)) that fluctuate due to seasonal variations in precipitation and temperature, and the other has delta O-18(lake) that is influenced by longer lake water residence times and evaporation. The delta O-18(diatom) records reveal common responses to precipitation forcing over the past millennium. Relatively wet summers are inferred from delta O-18(diatom) between 1000 and 1080 AD, 1300 and 1440 AD, and during the early 19th century, coincided with periods of high cloud cover inferred from tree-ring carbon isotopes, and other data for high Arctic Oscillation index. While relatively dry summers with increasing influence of winter snow are indicated between 1600 and 1750 AD. The co-response between carbon isotopes in trees and oxygen isotopes in diatoms strengthens the relationship between cloud cover and precipitation and the hypothesis that these changes were the result of significant regional shifts in atmospheric circulation.

  Read more about Shifts in precipitation during the last millennium in northern Scandinavia from lacustrine isotope records

• Contrasting trends in floods for two sub-arctic catchments in northern Sweden - does glacier presence matter?

  2012. Helen E. Dahlke (et al.). Hydrology and Earth System Sciences 16 (7), 2123-2141

  Article

  Our understanding is limited to how transient changes in glacier response to climate warming will influence the catchment hydrology in the Arctic and Sub-Arctic. This understanding is particularly incomplete for flooding extremes because understanding the frequency of such unusual events requires long records of observation not often available for the Arctic and Sub-Arctic. This study presents a statistical analysis of trends in the magnitude and timing of flood extremes and the mean summer discharge in two sub-arctic catchments, Tarfala and Abisko, in northern Sweden. The catchments have different glacier covers (30% and 1%, respectively). Statistically significant trends (at the 5% level) were identified for both catchments on an annual and on a seasonal scale (3-months averages) using the Mann-Kendall trend test. Stationarity of flood records was tested by analyzing trends in the flood quantiles, using generalized least squares regression. Hydrologic trends were related to observed changes in the precipitation and air temperature, and were correlated with 3-months averaged climate pattern indices (e.g. North Atlantic oscillation). Both catchments showed a statistically significant increase in the annual mean air temperature over the comparison time period of 1985-2009 (Tarfala and Abisko p < 0.01), but did not show significant trends in the total precipitation (Tarfala p = 0.91, Abisko p = 0.44). Despite the similar climate evolution over the studied period in the two catchments, data showed contrasting trends in the magnitude and timing of flood peaks and the mean summer discharge. Hydrologic trends indicated an amplification of the streamflow and flood response in the highly glacierized catchment and a dampening of the response in the non-glacierized catchment. The glacierized mountain catchment showed a statistically significant increasing trend in the flood magnitudes (p = 0.04) that is clearly correlated to the occurrence of extreme precipitation events. It also showed a significant increase in mean summer discharge (p = 0.0002), which is significantly correlated to the decrease in glacier mass balance and the increase in air temperature (p = 0.08). Conversely, the non-glacierized catchment showed a significant decrease in the mean summer discharge (p = 0.01), the flood magnitudes (p = 0.07) and an insignificant trend towards earlier flood occurrences (p = 0.53). These trends are explained by a reduction of the winter snow pack due to higher temperatures in the winter and spring and an increasing soil water storage capacity or catchment storage due to progressively thawing permafrost.

  Read more about Contrasting trends in floods for two sub-arctic catchments in northern Sweden - does glacier presence matter?

• Holocene tephrochronology of the Hualaihue region (Andean southern volcanic zone, similar to 42 degrees S), southern Chile

  2011. Sebastian F. L. Watt (et al.). Quaternary International 246, 324-343

  Article

  Late Glacial and Holocene soils and sediments in southern Chile contain an important record of explosive volcanic activity since the end of the last glaciation, and have considerable potential for the development of a regional tephrostratigraphical framework. This paper reports the discovery of several new tephra deposits from the Hualaihue region (similar to 42 degrees S) of southern Chile. Eruption sizes, constrained from field observations, and ages, constrained by 25 new radiocarbon dates, show that the volcanoes of the Hualaihue peninsula have had relatively few explosive, tephra-generating eruptions during the Holocene. An eruption of Apagado deposited similar to 1 km(3) of bedded basaltic scoria at similar to 2.6 calibrated (cal) ka BP, and Hornopiren produced a similar, but volumetrically-smaller unit at similar to 5.7 cal ka BR Activity at Yate over the same time period has been predominantly characterised by lava production, although small explosive eruptions, the products of which span a range of compositions, have also occurred, including one at similar to 0.9 cal ka BR The northern part of the regional tephra sequence is dominated by andesitic pumice fall deposits derived from Calbuco volcano. These include deposits from several eruptions during a 3500-year-long period at the start of the Holocene, as well as two large explosive eruptions in the past 2000 years. A distinctive rhyolitic tephra layer that is interbedded with the locally derived tephra sequence is the Cha1 unit, from Chaiten volcano, 108 km south of Hornopiren. This rhyolitic pumice deposit, dated at similar to 9.75 cal ka BP, is the largest volumetrically of those described here, with a volume of 3.5 km(3). This new tephrostratigraphy covers a region whose volcanic history was previously very little known, and contributes to a regional record of large explosive eruptions that now spans a 500 km-long segment of the southern Andean arc, between Calbuco and Hudson volcanoes.

  Read more about Holocene tephrochronology of the Hualaihue region (Andean southern volcanic zone, similar to 42 degrees S), southern Chile

• High-resolution diatom delta O-18 records, from the last 150 years, reflecting changes in amount of winter precipitation in two sub-Arctic high-altitude lakes in the Swedish Scandes

  2010. Christina E. Jonsson (et al.). Journal of Quaternary Science 25 (6), 918-930

  Article

  Waters from high-altitude alpine lakes are mainly recharged by meteoric water. Because of seasonal variations in precipitation and temperature and relatively short hydraulic residence times, most high-altitude lakes have lake water isotopic compositions (delta O-18(lake)) that fluctuate due to seasonality in water balance processes. Input from snowmelt, in particular, has a significant role in determining lake water delta O-18. Here we compare two high-resolution delta O-18(diatom) records from lake sediments in the Swedish Scandes with instrumental data from the last century obtained from nearby meteorological stations. The time period AD 1900-1990 is characterised by an increase in winter precipitation and high winter/summer precipitation ratios and this is recorded in delta O-18(diatom) as decreasing trends. Lowest delta O-18(diatom) values and highest amount of winter precipitation are found around AD 1990 when the winter North Atlantic Oscillation index was above +2. We conclude that for the last 150 a the main factor affecting the delta O-18(diatom) signal in these sub-Arctic high-altitude lakes with short residence times has been changes in amount of winter precipitation and that delta O-18(diatom) derived from high-altitude lakes in the Swedish Scandes can be used as a winter precipitation proxy.

  Read more about High-resolution diatom delta O-18 records, from the last 150 years, reflecting changes in amount of winter precipitation in two sub-Arctic high-altitude lakes in the Swedish Scandes

• Late Holocene climate change in central Sweden inferred from lacustrine stable isotope data

  2010. Sofia Andersson (et al.). Journal of Quaternary Science 25, 1305-1316

  Article

  Stable isotopes (¹⁸O and ¹³C) of lacustrine carbonates (Chara spp algae and Pisidium spp molluscs) from a lake sedimentary sequence in central Sweden were analysed to infer changes in lake hydrology and climate during the late Holocene. Results from analysis of lake water isotopes (¹⁸O and ²H) show that Lake Blektjärnen water isotope composition is responsive to the water balance between evaporation and input water (E/I ratio). A high E/I ratio results from a dry and probably warmer climate, decreasing the relative importance of precipitation input. Under such conditions evaporation and atmospheric equilibration enrich lake water in ¹⁸O and ¹³C, respectively, which is reflected in the isotopic composition of the carbonates in the lake. From the relatively positive Chara ¹⁸O values we infer that conditions were dry and warm between 4400-4000 cal yr BP whereas more negative values indicate that conditions were wetter and probably cooler between 4000-3000 cal yr BP. A drier climate is inferred from more positive values between 2500-1000 cal yr BP. However, a successive depletion after ca 1750 cal yr BP, also detected in several other ¹⁸O records (carbonate and diatom), suggest increasingly wetter conditions in Scandinavia after that time, which is probably related to increased zonal flow.

  Read more about Late Holocene climate change in central Sweden inferred from lacustrine stable isotope data

• Reconstructing past atmosperic circulation changes using oxygen isotopes in lake sediments from Sweden

  2010. C. E. Jonsson (et al.). Climate of the Past 6 (1), 49-62

  Article

  Here we use lake sediment studies from Sweden to illustrate how Holocene-aged oxygen isotope records from lakes located in different hydrological settings, can provide information about climate change. In particular changes in precipitation, atmospheric circulation and water balance. We highlight the importance of understanding the present lake hydrology, and the relationship between climate variables and the oxygen isotopic composition of precipitation (d¹⁸O_p)and lake waters (d¹⁸O_lakewater) for interpretation of the oxygen isotopic record from the sediments (d¹⁸O). Both precipitation reconstructions from northern Sweden and water balance reconstructions from south and central Sweden show that the atmospheric circulation changed from zonal to a more meridional airflow over the Holocene. Superimposed on this Holocene trend are δ¹⁸O_p minima resembling intervals of the negative phase of the North Atlantic Oscillation (NAO), thus suggesting that the climate of Northern Europe is strongly influenced by atmospheric and oceanic circulation changes over the North Atlantic.

  Read more about Reconstructing past atmosperic circulation changes using oxygen isotopes in lake sediments from Sweden

• Influence of geomorphological setting, fluvial-, glaciofluvial- and mass-movement processes on sedimentation in alpine lakes

  2009. Lena Rubensdotter, Gunhild Rosqvist. The Holocene 19 (4), 665-678

  Article

  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. moth 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.

  Read more about Influence of geomorphological setting, fluvial-, glaciofluvial- and mass-movement processes on sedimentation in alpine lakes

• Reconstructing past atmospheric circulation changes using oxygen isotopes in lake sediments from Sweden

  2009. C. E. Jonsson (et al.). Climate of the Past Discussions 5 (3), 1609-1644

  Article

  Here we use lake sediment studies from Sweden to illustrate how Holocene-aged oxygen isotope records (from lakes located in different hydrological settings) can provide information about climate change. In particular changes in precipitation, atmospheric circulation and water balance. We highlight the importance of understanding the present and past lake hydrology, and the relationship between climate parameters and the oxygen isotopic composition of precipitation (d¹⁸O_p) and lake waters (d¹⁸O_lakewater) for interpretation of the oxygen isotopic record from the sediments (d¹⁸O). Both precipitation reconstructions from northern Sweden and water balance reconstructions from south and central Sweden show that the atmospheric circulation changed from zonal to a more meridional air flow over the Holocene. Superimposed on this Holocene trend are δ¹⁸O_p minima resembling intervals of the negative phase of the North Atlantic Oscillation (NAO), thus suggesting that the climate of Northern Europe is strongly influenced by atmospheric and oceanic circulation changes over the North Atlantic.

  Read more about Reconstructing past atmospheric circulation changes using oxygen isotopes in lake sediments from Sweden

• Stable oxygen and hydrogen isotopes in sub-Arctic lake wateras from northern Sweden

  2009. Christina E. Jonsson (et al.). Journal of Hydrology 376 (1-2), 143-151

  Article

  Lakes in sub-Arctic regions have the potential of retaining many different aspects of water isotope composition in their sediments which can be used for palaeoclimate reconstruction. It is therefore important to understand the modern isotope hydrology of these lakes. Here we discuss the significance of variations in water isotope composition of a series of lakes located in north-west Swedish Lapland. Climate in this region is forced by changes in the North Atlantic which renders it an interesting area for climate reconstructions. We compare δ¹⁸O_lake and δ²H_lake collected between 2001 and 2006 and show that the lakes in this sub-Arctic region are currently mainly recharged by shallow groundwater and precipitation which undergoes little subsequent evaporation, and that the d¹⁸O and δ²H composition of input to the majority of the lakes varies on a seasonal basis between winter precipitation (and spring thaw) and summer precipitation. Seasonal variations in the isotopic composition of the lake waters are larger in lakes with short residence times (<6 months), which react faster to seasonal changes in the precipitation, compared to lakes with longer residence times (>6 months), which retain an isotopic signal closer to that of annual mean precipitation. Lake waters also show a range of isotope values between sites due to catchment elevation and timing of snow melt. The lake water data collected in this study was supported by isotope data from lake waters, streams and ground waters from1995 to 2000 reported in other studies.

  Read more about Stable oxygen and hydrogen isotopes in sub-Arctic lake wateras from northern Sweden

• Holocene glaciations in the Ema Glacier valley, Monte Sarmiento, Tierra del Fuego

  2008. Jorge Strelin (et al.). Palaeogeography, Palaeoclimatology, Palaeoecology 260, 299-314

  Article

  Read more about Holocene glaciations in the Ema Glacier valley, Monte Sarmiento, Tierra del Fuego

• Preliminary Sampling Report from Stuor Guossásjavri, Northern Sweden

  2008. Laura Cunningham (et al.). European Climate of the Last Millennium, Millennium Milestone meeting 2, Cala Millor, Mallorca, 13th-15th March 2008, 80-81

  Conference

  Read more about Preliminary Sampling Report from Stuor Guossásjavri, Northern Sweden

• Reconstructing environmental and climate changes in Vindelfjällen, using lake sediments.

  2008. Annika Berntsson, Gunhild Rosqvist.

  Conference

  Read more about Reconstructing environmental and climate changes in Vindelfjällen, using lake sediments.

• North Atlantic region atmospheric circulation dynamics inferred from a late-Holocene lacustrine carbonate isotope record, northern Swedish Lapland

  2007. G. C. Rosqvist, M. J. Leng, C. Jonsson. The Holocene 17 (7), 867–873

  Article

  The first high-resolution record of climate variation based on the oxygen and carbon isotope composition of authigenic carbonate for northern Scandinavia is presented. Modern lake-water isotope data indicate that controls on its oxygen and hydrogen (δ18O_w and δD_w) composition are unlikely to be evaporation or temperature, and its variations must therefore reflect changes in, or at the source of, precipitation. Substantial and persistent changes of the isotopic composition of the precipitation are required to change the mean annual isotope composition of lake surface water. For this reason we argue that the recorded changes were significant and that the recurrence of such changes would greatly affect future regional climate conditions in the North Atlantic region. Oxygen isotope (δ¹⁸O) minima occurring at ~ 200, 500, 1300, 1600 and at 2900 cal. yr BP all coincide with major peaks in North Atlantic ice rafted debris deposition. We suggest that the depletion events in δ¹⁸O cycles recorded in several lakes in northern Swedish Lapland are caused by the same climatic shifts as those noted in the North Atlantic marine records. This is because changes of atmospheric circulation pattern and the lower ocean and atmospheric temperatures associated with the IRD events help to explain why 18O depletion of precipitation occurred during these events. Our findings indicate that the recorded changes in North Atlantic ice drift and surface hydrography are coupled to changes in atmospheric circulation. 

  Read more about North Atlantic region atmospheric circulation dynamics inferred from a late-Holocene lacustrine carbonate isotope record, northern Swedish Lapland

• Diatom oxygen isotopes in pro-galcial lake sediments from northern Sweden: A 5000 year record of atmospheric circulation.

  2004. G. Rosqvist (et al.). Quaternary Science Reviews 23 (7-8), 851-859

  Article

  We use a pro-glacial oxygen isotope record of diatom silica (δ¹⁸O_diatom) and a sedimentary proxy for glacier flutuations to determine centennial-millennial scale climate change during the last 5000 yeras in northern Sweden. We show that the lake water isotopic composition åredominantly reflects the isotopic composition of the precipitation. Superimposed on a general depletion trend of 3.5‰ over the past 5000 years we found that the isotopic composition of precipitation became depleted (> 1‰ excursions) during four occasions centered at 4400, 3000, 2000 and, after 1200 cal yr BP. Climate simultaneously sustained a positive glacier mass balance, taht caused the catchment glacier to advance. A peristan cgange in the atmopheric circulation pattern could potentially have caused the registered chnages in the δ¹⁸O_diatom because different air masses hold characteristics δ¹⁸O signatures of their precipitation. The glacier mass balance primarily responds to the influence of summer temperature on ablation. We suggest that the most likely cause for the recorded chnages in both these proxies is a steadily increasing but fluctuating dominance of colder and δ¹⁸O depleted air masses from the north/northeast during the past 5000 years. Theδ¹⁸O_diatom depletion and glacier events all occur at times of relative ice-rafted-debris maxima in the North Atlanic, consistent with cold conditions and changes in surface wind directions. Our results confirm that changes towards a predominace of north/northeasterly winds occured at these time intervals.

  Read more about Diatom oxygen isotopes in pro-galcial lake sediments from northern Sweden: A 5000 year record of atmospheric circulation.

• High-resolution diatom d18O records from two sub-Arctic high-altitude lakes in the Swedish Scandes

  C. E. Jonsson (et al.). Journal of Quaternary Science

  Article

  Waters from high altitude alpine lakes are mainly recharged by meteoric water. Because of seasonal variations in precipitation and temperature, and relatively short hydraulic residence times, most high altitude lakes have lake water isotopic compositions (δ¹⁸O_lake) that fluctuate due to seasonality in water balance processes. Input from snowmelt, in particular, has a significant role in determining lake water d¹⁸O. Here we compare two high resolution δ¹⁸O_diatom records from lake sediments in the Swedish Scandes with instrumental data from the last century obtained from nearby meteorological stations. The time period AD 1900 to AD 1990 is characterized by an increase in winter precipitation and high winter/summer precipitation ratios and this is recorded in δ¹⁸O_diatom as decreasing trends. Lowest δ¹⁸O_diatom values and highest amount of winter precipitation are found around AD 1990 when the winter North Atlantic Oscillation index was above +2. We conclude that for the last 150 years the main factor affecting the δ¹⁸O_diatom signal in these sub-Arctic high altitude lakes with short residence times has been changes in amount of winter precipitation and that δ¹⁸O_diatom derived from high altitude lakes in the Swedish Scandes can be used as a winter precipitation proxy.

  Read more about High-resolution diatom d18O records from two sub-Arctic high-altitude lakes in the Swedish Scandes

Show all publications by Gunhild Rosqvist at Stockholm University