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  • 1. Booth, Adam D.
    et al.
    Mercer, Andrew
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Clark, Roger
    Murray, Tavi
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Axtell, Charlotte
    A comparison of seismic and radar methods to establish the thickness and density of glacier snow cover2013In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 54, no 64, 73-82 p.Article in journal (Refereed)
    Abstract [en]

    We show that geophysical methods offer an effective means of quantifying snow thickness and density. Opportunistic (efficient but non-optimized) seismic refraction and ground-penetrating radar (GPR) surveys were performed on Storglaciaren, Sweden, co-located with a snow pit that shows the snowpack to be 1.73 m thick, with density increasing from similar to 120 to similar to 500 kg m(-3) (with a +50 kg m(-3) anomaly between 0.73 and 0.83 m depth). Depths estimated for two detectable GPR reflectors, 0.76 +/- 0.02 and 1.71 +/- 0.03 m, correlate extremely well with ground-truth observations. Refraction seismic predicts an interface at 1.90 +/- 0.31 m depth, with a refraction velocity (3730 +/- 190 m s(-1)) indicative of underlying glacier ice. For density estimates, several standard velocity-density relationships are trialled. In the best case, GPR delivers an excellent density estimate for the upper snow layer (observed = 321 +/- 74 kg m(-3), estimated = 319 +/- 10 kg m(-3)) but overestimates the density of the lower layer by 20%. Refraction seismic delivers a bulk density of 404 +/- 22 kg m(-3) compared with a ground-truth average of 356 +/- 22 kg m(-3). We suggest that geophysical surveys are an effective complement to mass-balance measurements (particularly for controlling estimates of snow thickness between pits) but should always be validated against ground-truth observations.

  • 2.
    Clason, Caroline C.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Coch, Caroline
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jarsjö, Jerker
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Brugger, K.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Rosqvist, Gunhild
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Dye tracing to determine flow properties of hydrocarbon-polluted Rabots glaciar, Kebnekaise, Sweden2015In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 19, no 6, 2701-2715 p.Article in journal (Refereed)
    Abstract [en]

    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.

  • 3.
    Dahlke, Helen E.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Karlin, Torbjörn
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Rosqvist, Gunhild
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Isotopic investigation of runoff generation in a glacierized catchment in northern Sweden2014In: Hydrological Processes, ISSN 0885-6087, E-ISSN 1099-1085, Vol. 28, no 3, 1383-1398 p.Article in journal (Refereed)
    Abstract [en]

    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.

  • 4.
    Dahlke, Helen E.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Lyon, Steve W.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Stedinger, J. R.
    Rosqvist, Gunhild
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Contrasting trends in floods for two sub-arctic catchments in northern Sweden - does glacier presence matter?2012In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 16, no 7, 2123-2141 p.Article in journal (Refereed)
    Abstract [en]

    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.

  • 5. Fredin, Ola
    et al.
    Beylich, A
    Nesje, Atle
    Larsen, E
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Burki, Valentin
    Recycling of glacial and non-glacial sediments duringt the 'Little Ice Age' advance around Jostedalsbreen, south-central Norway2007In: Abstracts and Proceedings of the Geological Society of Norway, 2007, 27-28 p.Conference paper (Other (popular science, discussion, etc.))
  • 6. Gusmeroli, Alessio
    et al.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Pettersson, Rickard
    Murray, Tavi
    Twenty years of cold surface layer thinning at Storglaciaren, sub-Arctic Sweden, 1989-20092012In: Journal of Glaciology, ISSN 0022-1430, E-ISSN 1727-5652, Vol. 58, no 207, 3-10 p.Article in journal (Refereed)
    Abstract [en]

    This paper presents the changes in the thermal structure of the polythermal glacier Storglaciaren, northern Sweden, over the 20 year period 1989-2009 derived by comparing maps of the depth of the englacial transition between cold ice (permanently frozen) and temperate ice (which contains water inclusions). The maps are based on interpreted ice-penetrating radar surveys from 1989, 2001 and 2009. Complex thinning of the cold layer, first identified between 1989 and 2001, is still ongoing. A volume calculation shows that Storglaciaren has lost one-third of its cold surface layer volume in 20 years, with a mean thinning rate of 0.80 +/- 0.24 m a(-1). We suggest that the thinning of the cold layer at Storglaciaren is connected to the climatic warming experienced by sub-Arctic Scandinavia since the 1980s and we argue that repeated ice-penetrating radar surveys over the ablation area of polythermal glaciers offer a useful proxy for evaluating glacier responses to changes in climate.

  • 7. Gusmeroli, Alessio
    et al.
    Murray, Tavi
    Clark, Roger A.
    Kulessa, Bernd
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Vertical seismic profiling of glaciers: appraising multi-phase mixing models2013In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 54, no 64, 115-123 p.Article in journal (Refereed)
    Abstract [en]

    We have investigated the speed of compressional waves in a polythermal glacier by, first, predicting them from a simple three-phase (ice, air, water) model derived from a published ground-penetrating radar study, and then comparing them with field data from four orthogonally orientated walkaway vertical seismic profiles (VSPs) acquired in an 80 m deep borehole drilled in the ablation area of Storglaciaren, northern Sweden. The model predicts that the P-wave speed increases gradually with depth from 3700 m s(-1) at the surface to 3760 m s(-1) at 80 m depth, and this change is almost wholly caused by a reduction in air content from 3% at the surface to <0.5% at depth. Changes in P-wave speed due to water content variations are small (<10 m s(-1)); the model's seismic cold-temperate transition surface (CTS) is characterized by a 0.3% decrease downwards in P-wave speed (about ten times smaller than the radar CTS). This lack of sensitivity, and the small contrast at the CTS, makes seismically derived water content estimation very challenging. Nevertheless, for down-going direct-wave first arrivals for zero- and near-offset VSP shots, we find that the model-predicted travel times and field observations agree to within 0.2 ms, i.e. less than the observational uncertainties.

  • 8. Gusmeroli, Alessio
    et al.
    Murray, Tavi
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Pettersson, Rickard
    Aschwanden, Andy
    Booth, Adam D.
    Vertical distribution of water within the polythermal glacier Storglaciären, Sweden2010In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 115, F04002- p.Article in journal (Refereed)
    Abstract [en]

    Knowledge of water content and its distribution in polythermal glaciers is required tomodel their flow and thermal state. However, observations of water content variations withdepth in polythermal glaciers are scarce. Water content can be estimated from radiowave speed because they depend on one another. We obtained continuous profiles of radiowave speed variations with depth from zero‐offset radar profiles collected in boreholesapproximately 80 m deep in the upper ablation area of Storglaciären, northern Sweden.These profiles show that the microcrystalline water system in the temperate ice is relativelyhomogeneous. The overall hydrothermal structure at this location is composed of a 20 mthick upper layer of cold, water‐free ice, underlain by a temperate ice layer whose averagewater content is 0.6% ± 0.3%. These results are corroborated by surface radar andthermistor measurements, which show that the depth of the cold temperate transition is21 m and the calculated water content at that transition is 0.6% ± 0.1%. These findingsimply that the whole temperate ice layer is from 3 to 4 times softer than the cold ice and,consequently, that realistic ice flow models of polythermal glaciers should include theeffect of water content on viscosity.

  • 9.
    Helanow, Christian
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Meierbachtol, Toby
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Steady-state water pressures in subglacial conduits: corrections to a model and recommendations for its use2015In: Journal of Glaciology, ISSN 0022-1430, E-ISSN 1727-5652, Vol. 61, no 225, 202-204 p.Article in journal (Refereed)
  • 10.
    Ingvander, Susanne
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Brown, Ian A.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Johansson, Cecilia
    Rosqvist, Gunhild
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Method study: Grain size sampling and digital object oriented image analysis for explanation of snow grain size, shape and distributionIn: Journal of Glaciology, ISSN 0022-1430, E-ISSN 1727-5652Article in journal (Refereed)
    Abstract [en]

    We have developed a digital image processing method for snow particle size and shape analysis suitable for quick and reliable analysis in the eld. Snow particle size is an important parameter strongly aecting snow cover albedo from seasonally snow covered areas and ice sheets. It is also important in remote sensing analysis because it influences the reflectance and scattering properties of the snow. Alternatively traditional methods based on visual inspection of samples can be used but they do not yield quantitative data. Our method provides an additional alternative to both simpler and more complex methods by providinga tool that limits the subjective eect of the visual analysis and provides a quantitativeparticle 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 results from the analysis are a two dimensional analysis of particle size, shape and distributions for each sample. The developed method improves snow particle analysis being quantitative, reproducible and applicable for dierent types of eld sites.

  • 11.
    Ingvander, Susanne
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Brown, Ian A.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Peter
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Johansson, Cecilia
    Rosqvist, Gunhild
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Particle Size Sampling and Object-Oriented Image Analysis for Field Investigations of Snow Particle Size, Shape, and Distribution2013In: Arctic, Antarctic and Alpine research, ISSN 1523-0430, E-ISSN 1938-4246, Vol. 45, no 3, 330-341 p.Article in journal (Refereed)
    Abstract [en]

    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.

  • 12.
    Ingvander, Susanne
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Brown, Ian
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Spatial snow grain size variability along the JASE 2007/2008 traverse route in Dronning Maud Land, Antarctica, and its relation to MOA NDSI index, MEDRIS and MODIS sattelite data2010In: Proceedings of ESA Living Planet Symposium: 28 June - 2 July 2010, Bergen, Norway / [ed] H. Lacoste-Francis, Noordwijk: ESA (European Space Agency) , 2010Conference paper (Other academic)
    Abstract [en]

    Snow grain size is an important parameter for determining albedo of the ice sheets and for calibration of optical and microwave remote sensing scattering processes. Snow grain size is a function of the local climate determined by moisture content, air and snow temperature, their gradients within the snow and firn, and wind patterns. Furthermore, it is an indicator on snow metamorphism. We have developed The Digital Grain Size Properties method (DGSP-method) using object oriented image analysis of very high resolution snow grain size images. Commonly used methods are based on visual interpretation, which is a subjective method providing only mean grain size does not retrieve size distribution within each sample.

    This is a first attempt to validate satellite information by the in situ measurements from JASE (Japanese Swedish Antarctic Expedition) 2007/2008 using digital image processing. The DSGP-method is based on in-field photography of snow and pixel-based object oriented image analysis. The results show shows decreasing grain size towards the centre of Antarctica and larger grains in the coastal areas. The data used to validate is three different products based on two different types of optic satellite sensors; MERIS (Medium Resolution Imaging Spectrometer) and MODIS (Moderate Resolution Imaging Spectroradiometer).  A first validation captures a cluster relation between grain size in the coastal and at the plateau and optical satellite reflection.

  • 13.
    Ingvander, Susanne
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Dahlke, Helen E.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Surdyk, Sylviane
    In situ sampled snow particle sizes of the East Antarctic ice sheet and their relation to physical and remotely sensed snow surface parameters2013In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 54, no 62, 166-174 p.Article in journal (Refereed)
    Abstract [en]

    Knowledge of snow properties across Antarctica is important in estimating how climate could potentially influence the mass balance of the Antarctic ice sheet. However, measuring these variables has proven to be challenging because appropriate techniques have not yet been developed and extensive datasets of field estimates are lacking. The goal of this study was to estimate the relationship between field-observed snow particle-size parameters from across the East Antarctic ice sheet and a suite of spatial datasets (i.e. topography, remote-sensing data) using a principal component analysis (PCA). Five snow particle-size parameters were correlated to spatial datasets of the following five groups: (1) relief properties such as elevation and slope; (2) remote-sensing data from Moderate Resolution Imaging Spectroradiometer (MODIS) and synthetic aperture radar (SAR) sensors; (3) spatially interpolated data (i.e. 10 m maps of temperature and approximate snow accumulation in kg m(-2) a(-1)); (4) field-retrieved data on surface roughness; and (5) in situ elevation and distance from the coast. The results show that the relief parameter slope correlated best with the snow particle length and area (r=0.76, r=0.80). Further, the PCA indicated that the different remote-sensing parameters correlated differently with the size parameters and that the most common parameter in visual analysis, particle length (grain diameter), is not always the optimal parameter to characterize the snow particle size as, for example, area correlates better to slope and aspect than length.

  • 14.
    Ingvander, Susanne
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Brown, Ian A.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Fujita, Shuji
    Sugyama, Shin
    Surdyk, Sylviane
    Enomoto, Hiroyouki
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Regional and local Snow Grain Size variations in Dronning Maud Land, Antarctica and analysis of various distribution scalesManuscript (preprint) (Other academic)
    Abstract [en]

    Understanding spatial snow particle size variations are key to help interpretation of remotely sensed data of snow cover. In the case of Antarctica, remote sensing is the only viable option to estimate the surface mass balance of the ice sheet on continental scale. We have investigated snow particle size variability along a transect from the coast onto the polar plateau in Dronning Maud Land, Antarctica, to better understand the spatial and temporal variations in surface snow properties. Two daily samples were collected during a 55 day traverse to capture the regional variability. Local variability was assessed by sampling in grids at selected locations and the particle size and shape distributions for each site was analysed through digital image analysis, which has the benefit of yielding large quantities of reproducible quantitative data without the need for advanced laboratory analysis. The results provide an understanding of the complexity of snow particle size variability at different scales and show a variability range from 0.18–3.31 mm depending on the sample type (surface, grid or pit). We can verify relationships between grain size and both elevation and distance to the coast (moisture source) but have also identified regional seasonal changes, particularly on the lower elevations of the polar plateau. Our data provide possibilities to quantitatively assess the optical properties of the surface snow for remote sensing. The details of the spatial and temporal variations observed in our data provides a basis for further studies of the complex and coupled processes affecting snow particle size and the interpretation of remote sensing of snow covered areas.

  • 15.
    Ingvander, Susanne
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Brown, Ian A.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Fujita, Shuji
    Sugyama, Shin
    Surdyk, Sylviane
    Enomoto, Hiroyuki
    Hansson, Margareta
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Snow particle sizes and their distributions in Dronning Maud Land, Antarctica, at sample, local and regional scales2016In: Antarctic Science, ISSN 0954-1020, E-ISSN 1365-2079, Vol. 28, no 3, 219-231 p.Article in journal (Refereed)
    Abstract [en]

    In this study, snow particle size variability was investigated along a transect in Dronning Maud Land from the coast to the polar plateau. The aim of the study was to better understand the spatial and temporal variations in surface snow properties. Samples were collected twice daily during a traverse in 2007-08 to capture regional variability. Local variability was assessed by sampling in 10 x 10m grids (5m spacing) at selected locations. The particle size and shape distributions for each site were analysed through digital image analysis. Snow particle size variability is complex at different scales, and shows an internal variability of 0.18-3.31 mm depending on the sample type (surface, grid or pit). Relationships were verified between particle size and both elevation and distance to the coast (moisture source). Regional seasonal changes were also identified, particularly on the lower elevations of the polar plateau. This dataset may be used to quantitatively analyse the optical properties of surface snow for remote sensing. The details of the spatial and temporal variations observed in our data provide a basis for further studies of the complex and coupled processes affecting snow particle size and the interpretation of remote sensing of snow covered areas.

  • 16.
    Ingvander, Susanne
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Johansson, Cecilia
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Pettersson, Rickard
    Comparison between digital and manual methods of snow grain size determination2012In: Hydrology Research, ISSN 0029-1277, Vol. 43, no 3, 192-202 p.Article in journal (Refereed)
    Abstract [en]

    Maintaining long time series of observations of the Cryosphere is a key issue in climate research. Long observational time series involve problems due to change in methodology or observers. In order to extend time series and introduce new methods, careful comparisons must be made to ensure homogeneity in the observational data. We have compared an established method for snow grain-size observations used by the Abisko Scientific Research Station (ASRS) in northern Sweden, based on visual interpretation, with a newly developed method for Digital Snow Particle Properties (DSPP) analysis. Transition from subjective visual method into digital reproducible analysis creates less subjective and more comparable results. The ASRS method generates size classifications excluding quantitative analysis size ranges. By determining the sizes of the classified snow using the DSPP-method, actual size ranges for classified snow can be established. By performing a digital analysis of the reference samples and the snow samples classified, we can compare the ASRS classification system to existing official classification systems. The results indicate underestimation of the visual particle size in comparison to the reference samples. Our results show how to quantify the historical data set, which enables us to perform quantitative analysis on the historical data set.

  • 17.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Ice sheet hydrology from observations2010Report (Other academic)
    Abstract [en]

    This report summarizes our understanding of ice sheet hydrology as reported on observations from Antarctica and Greenland. Much of our general understanding of ice sheet hydrological processes are based on work performed on valley glaciers. Since processes do not differ in function but perhaps in magnitude, the understanding gained from smaller glaciers work applies to ice sheets. Hence, this report does not deal with such basic processes. Glacier hydrological investigations on ice sheets have been few but are perhaps accelerating in numbers with the increased focus on both Greenland and Antarctica from the scientific community in the light of effects from climate change. The process oriented studies carried out over the past 50 years or so have not generally been much applied to ice sheets and observations on the morphology of ice sheet and valley glacier hydrological systems have not been connected although most glacier hydrologists would not consider such parallels a stretch of their imagination. Much of the new studies on ice sheet hydrology, thus far, fits in two categories. One concerns verification of well-documented processes but on an ice sheet scale; the other concerns ice sheet specific features. These categories constitute the basis for this report.

  • 18.
    Jansson, Peter
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Fredin, Ola
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Ice sheet growth under dirty conditions: implications of debris cover for early glaciation advances2002In: Quaternary International, ISSN 1040-6182, E-ISSN 1873-4553, Vol. 95-96, 35-42 p.Article in journal (Refereed)
    Abstract [en]

    Debris-covered glaciers respond differently to any given set of climatic conditions than clean glaciers. This difference stems from change in ablation rate caused by a debris cover, approaching zero ablation with sufficiently thick protective cover, a mechanism not yet considered in the context of ice sheet growth. Critical to applying the mechanism to ice sheets is supply of debris. We postulate that periods after major interglacials offer the best conditions for dirty advances. This is because the volume of debris, previously deposited and weathered in interglacial time, the latter a function of exposure length, should be at a maximum. Advances of dirty ice sheets generate landforms and in positions deviating from clean-ice advances under similar climatic conditions. Hence, inferences of both ice sheet properties inferred from such dirty ice advances and the climate conditions related to such advances must be cautious. Furthermore, modeling of past ice sheets must consider the effect of debris cover whenever indications exist for such a cover.

  • 19.
    Jansson, Peter
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Tarfala forskningsstation.
    Linderholm, Hans W.
    Pettersson, Rickard
    Karlin, Torbjörn
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Mörth, Carl-Magnus
    Department of Geology and Geochemistry.
    Assessing the possibility to couple chemical signals in winter snow on Storglaciären to atmospheric climatology2007In: Annals of Glaciology, ISSN 1727-5644, Vol. 46, 335-341 p.Article in journal (Refereed)
  • 20.
    Jansson, Peter
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Näslund, Jens-Ove
    Svensk Kärnbränslehantering AB.
    Spatial and temporal variations in glacier hydrology on Storglaciären, Sweden2009Report (Other academic)
    Abstract [en]

    The purpose of this report is to summarize the experimental work on glacier hydrology and basal hydraulic conditions performed on Storglaciären, northern Sweden, during the years 2003–2005. The aim of the project has been to provide a framework of real conditions within which to interpret theory and extrapolate conditions beneath a future ice sheet over Fennoscandia. Surface fed subglacial hydrological systems are extremely dynamic because the input rates of rain and temperature-contolled surface melt fluctuate and the geometry of flow paths is constantly changing due to ice deformation which tends to close the flow paths. The hydrological system of a glacier is unique since water is flowing through conduits made of its solid phase (ice). A possible analogy is lava flowing through rock of the same composition. Hence understanding the expected dynamic range of the glacier hydrological system is best studied by in situ measurements. The processes studied on Storglaciären can be expected to apply to ice sheet scale, albeit on different spatial scales. Since Storglaciären is a polythermal glacier with a large fraction of ice below freezing and at the melting point and with a surface-fed hydrological system of conduits and tunnels, results apply to the margins (ablation zone) of the past Fennoscandian Ice Sheet, at least along its southern margin.

    In this report we discuss the measurements made to assess the subglacial conditions that provide an analogue for conditions under the Fennoscandian Ice Sheet. We have also included a large quantity of unpublished data from Storglaciären from different research projects conducted since 1990. Together these data provide a good picture of the temporal and spatial water pressure conditions in and under Storglaciären. The report is the first comprehensive analysis of these subglacial water pressure records.

  • 21.
    Jansson, Peter
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Tarfala forskningsstation.
    Pettersson, Rickard
    Spatial and temporal characteristics of a long mass balance record, Storglaciären, Sweden2007In: Arctic, Antarctic and Alpine Research, ISSN 1523-0430, Vol. 39, no 3, 432-437 p.Article in journal (Refereed)
  • 22.
    Jaquet, Olivier
    et al.
    In2Earth Modelling Ltd.
    Namar,, Rabah
    In2Earth Modelling Ltd.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Groundwater flow modelling under ice sheet conditions: Scoping calculations2010Report (Other academic)
    Abstract [en]

    SKB, POSIVA (Finland) and NWMO (Canada) have established in 2009 the GAP project (Greenland Analogue Project). These organisations want to improve current understanding of continental ice sheet and permafrost effects on groundwater flow and water chemistry in crystalline rocks at depths of a potential repository. The idea is to apply the Greenland ice sheet as an analogue to future glaciations in Fennoscandia and Canada. The GAP project will enable to perform geological and geophysical investigations, measurements of glacial hydrology and hydrogeology as well as geochemical analyses in relation to current ice sheet conditions in Greenland.

  • 23.
    Johansson, A. Malin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Brown, Ian A.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Spatial and temporal variations in lakes on the Greenland Ice Sheet2013In: Journal of Hydrology, ISSN 0022-1694, E-ISSN 1879-2707, Vol. 476, 314-320 p.Article in journal (Refereed)
    Abstract [en]

    Surface lakes on the Greenland Ice Sheet provide temporary storage for meltwater that influences both the surface and basal water fluxes. Thus, to understand the effects of variations in surface melt on ice sheet dynamics it is necessary to understand the surface hydrology. We have used satellite imagery, acquired at 5-day intervals, to map lake initiation and cessation on two sub-sections on the south west Greenland Ice Sheet over three melt seasons (2007–2009). We observe that lake initiation is closely tied to a threshold energy input of approximately 40 ± 18.5 positive-degree-days. This applies to all studied melt seasons, regardless of evolution and melting index anomalies. Lake longevity averages 24 days with little variation between different melt seasons. Our observed median lake area is larger than previously reported. Approximately 50% of all lakes have a life span of <10 d. Cessation of identified lakes is caused by two processes: drainage during the melt season (88% – 2007, 78% – 2008 and 88% – 2009) and freezeup at the end of the season (12% – 2007, 22% – 2008 and 12% – 2009). Inclusion of the energy needed for lake initiation and number of lakes that freeze up at the end of the season into supra-glacial lake models will add further insight into the hydrological system dynamics.

  • 24.
    Johansson, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Brown, Ian A.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Multi-temporal, multi-sensor investigations of supra-glacial lakes on the Greenland Ice Sheet2011In: Proceedings of ESA Living Planet Symposium: 28 June - 2 July 2010, Bergen, Norway(DVD) / [ed] H. Lacoste-Francis, Noordwijk: ESA (European Space Agency) , 2011Conference paper (Other academic)
    Abstract [en]

    The stability of the ice sheets is affected by the ongoing climate change through changes in the meltwater budget and effects on ice sheet dynamics. Surface lakes on the Greenland Ice Sheet have attracted much attention, but assessing their number and size as well as the variability over time of these parameters is not straight-forward. We present a satellite image-based survey of the total lake area and number of supra-glacial lakes in a specific region on the western margin of the Greenland Ice Sheet. Optical images from two different sensors (Moderate Resolution Imaging Spectroradiometer (MODIS) and Landsat) and images from three different synthetic aperture radar (SAR) satellites (Radarsat, ERS and Envisat) from 2001, 2006 and 2007, were used in order to manually digitize the extent of supra-glacial lakes. The image spatial resolution ranges from high (Radarsat, ERS and Landsat) to moderate (Envisat and MODIS) where high resolution corresponds to 6.25 to 25 m, and a moderate resolution corresponds to 50 to 250 m. SAR imagery was tested as a supplement to the more commonly used optical data to fill gaps in the time series caused by frequent cloud cover. In total 709 individual lakes were studied. High resolution images were shown to be preferable in the beginning of the melt season, due to the smaller size of the lakes. In the middle of the melt season the resolution was of limited importance. Our work suggests that the use of a combination of active radar and optical images enables successful lake monitoring with high temporal and spatial resolution in both cloudy and clear weather conditions.

  • 25.
    Johansson, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Brown, Ian A.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Characteristics of supra-glacial lakes on the south-west Greenland Ice SheetManuscript (preprint) (Other academic)
    Abstract [en]

    Supra-glacial lake form and store melt water during the ablation season every year on the Greenland Ice Sheet (GrIS). This melt water influences both the surface and basal water fluxes. Using an adaptive object-oriented classification approach supra-glacial lakes on the west GrIS are mapped in Terra Moderate Resolution Imaging Spectroradiometer (MODIS) imagery 2001–2010. Lake size shape and distribution parameters are extracted for approximately 5-day intervals from the available cloud free imagery. Using temperature data measured within this region we correlate the lake parameters to melt proxies such ascumulative positive degree days (PDD). The analysis shows that simple parameters such as number of lakes and mean lake area, measures that have been used to describe the development of the surface hydrological system, are largely uncorrelated with melt proxies. Years with higher relative melt, expressed as negative surface mass balances and high PDDs, may exhibit long, predominantly mild melt seasons. Alternatively, a short but intense melt season may have occurred. Given the short duration of the time series, it is difficult to establish statistical relationships between parameters. However, parameters such as median lake size, reflectance and distance between lakes may provide valuable ancillary information to measures such as total lake area, median lake area and lake size distribution data.

  • 26.
    Johansson, Malin
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Brown, Ian A.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Spatial and temporal variations of the Greenland Ice Sheet surface lake systemManuscript (preprint) (Other academic)
    Abstract [en]

    Surface lakes on the Greenland Ice Sheet provide temporary storage for meltwater that influences both the surface and basal water fluxes. Thus, to understand the effects of variations in surface melt on ice sheet dynamics it is necessary to understand the surface hydrology. We have used satellite imagery, acquired at 5-day intervals, to map lake initiation and cessation on two sub-sections on the south west Greenland Ice Sheet over three melt seasons (2007-2009). We observe that lake initiation is closely tied to a threshold energy input of approximately 40 ± 18.5 positive-degree-days. This applies for all studied melt season, regardless of evolution and melt index anomalies. Lake longivity averages 24 days with little variation between different melt seasons. Our observed median lake area is larger than previously reported. Approximately 50% of all lakes have a life span of <10 days. Cessation of identified lakes is caused by two processes: drainage during the melt season (88% 2007, 78% 2008 and 88% 2009) and freeze-up at the end of the season (12% 2007, 22% 2008 and 12% 2009). Inclusion of energy needed for lake initiation and amount of freeze-up lakes into supra-glacial lake models will add further insight into the hydrological system dynamics.

  • 27.
    Koblet, Thomas
    et al.
    Department of Geography, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
    Gärtner-Roer, Ingrid
    Department of Geography, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
    Zemp, Michael
    Department of Geography, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Thee, Patrick
    Swiss Federal Institute for Forest, Snow and Landscape Research, Zürcherstrasse 111, 8903 Birmensdorf, Switzerland.
    Haeberli, Wilfried
    Department of Geography, University of Zurich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Reanalysis of multi-temporal aerial images of Storglaciären, Sweden (1959–99) – Part 1: Determination of length, area, and volume changes2010In: The Cryosphere, ISSN 1994-0416, Vol. 4, 333-343 p.Article in journal (Refereed)
    Abstract [en]

    Storglaciären, located in the Kebnekaise massif in northern Sweden, has a long history of glaciological research. Early photo documentations date back to the late 19th century. Measurements of front position variations and distributed mass balance have been carried out since 1910 and 1945/46, respectively. In addition to these in-situ measurements, aerial photographs have been taken at decadal intervals since the beginning of the mass balance monitoring program and were used to produce topographic glacier maps. Inaccuracies in the maps were a challenge to early attempts to derive glacier volume changes and resulted in major differences when compared to the direct glaciological mass balances. In this study, we reanalyzed dia-positives of the original aerial photographs of 1959, -69, -80, -90 and -99 based on consistent photogrammetric processing. From ther esulting digital elevation models and orthophotos, changes in length, area, and volume of Storglaciären were computed between the survey years, including an assessment of related errors. Between 1959 and 1999, Storglaciären lost an ice volume of 19×106 m3, which corresponds to a cumulative ice thickness loss of 5.69 m and a mean annual loss of 0.14 m. This ice loss resulted largely from a strong volume loss during the period 1959–80 and was partly compensated during the period 1980–99. As a consequence, the glacier shows a strong retreat in the 1960s, a slowing in the 1970s, and pseudo-stationary conditions in the 1980s and 1990s.

  • 28. Lindbäck, K.
    et al.
    Pettersson, R.
    Doyle, S. H.
    Helanow, Christian
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kristensen, S. S.
    Stenseng, L.
    Forsberg, R.
    Hubbard, A. L.
    High-resolution ice thickness and bed topography of a land-terminating section of the Greenland Ice Sheet2014In: Earth System Science Data, ISSN 1866-3508, E-ISSN 1866-3516, Vol. 6, no 2, 331-338 p.Article in journal (Refereed)
    Abstract [en]

    We present ice thickness and bed topography maps with a high spatial resolution (250-500 m) of a land-terminating section of the Greenland Ice Sheet derived from ground-based and airborne radar surveys. The data have a total area of similar to 12 000 km(2) and cover the whole ablation area of the outlet glaciers of Isunnguata Sermia, Russell, Leverett, Orkendalen and Isorlersuup up to the long-term mass balance equilibrium line altitude at similar to 1600m above sea level. The bed topography shows highly variable subglacial trough systems, and the trough of Isunnguata Sermia Glacier is overdeepened and reaches an elevation of similar to 500m below sea level. The ice surface is smooth and only reflects the bedrock topography in a subtle way, resulting in a highly variable ice thickness. The southern part of our study area consists of higher bed elevations compared to the northern part. The compiled data sets of ground-based and airborne radar surveys cover one of the most studied regions of the Greenland Ice Sheet and can be valuable for detailed studies of ice sheet dynamics and hydrology. The combined data set is freely available at doi:10.1594/pangaea.830314.

  • 29. Linderholm, Hans W.
    et al.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Reconstruction of Storglaciären glacier mass balance from 1500 AD using tree-ring data2007In: Annals of Glaciology, ISSN 1727-5644, Vol. 46, 261-267 p.Article in journal (Refereed)
  • 30. Linderholm, Hans W.
    et al.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Deliang, Chen
    A high-resolution reconstruction of Storglaciären mass balance back to 1780/1781 using tree-ring data and circulation indices.2007In: Quaternary Research, ISSN 0033-5894, Vol. 67, no 1, 12-20 p.Article in journal (Refereed)
    Abstract [en]

    Storglaciären in northernmost Sweden has the world’s longest ongoing continuous mass-balance record, starting in 1946. To extend this mass-balance record, we have reconstructed summer (bS) and winter (bW) mass balances separately back to the mass balance year 1780/81 with annual resolution. We used tree-ring data for bS and a set of circulation indices, based on the sea level pressure, for bW. Both proxies have correlation coefficients with respective mass balance components of ca. 0.7. The reconstructed net balance (bN) of Storglaciären was well correlated to the observations during 1946–1980 (r = 0.8, p<0.05). Our reconstruction agrees well with previously obtained results of northern Sweden glacier variability, where the predominantly positive bN years between 1890 and 1910 correspond to the well documented post-Little Ice Age advance of Storglaciären. Furthermore, the results suggest that bS, as a function of summer temperatures, is more important than bW in determining the bN, which is contrary to glaciers in the maritime parts of western Scandinavia. In general, bN has been negative over the last 220 yr, suggesting a predomination of continental conditions over northern Sweden. However, the influence of bW increased in the late twentieth century, indicating a shift to a more oceanic climate regime.

  • 31. Moore, Peter L.
    et al.
    Iverson, Neal R.
    Brugger, Keith A.
    Cohen, Denis
    Hooyer, Thomas S.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Effect of a cold margin on ice flow at the terminus of Storglaciären, Sweden: implications for sediment transport2011In: Journal of Glaciology, ISSN 0022-1430, E-ISSN 1727-5652, Vol. 57, no 201, 77-87 p.Article in journal (Refereed)
    Abstract [en]

    The cold-based termini of polythermal glaciers are usually assumed to adhere strongly toan immobile substrate and thereby supply significant resistance to the flow of warm-based ice upglacier.This compressive environment is commonly thought to uplift basal sediment to the surface ofthe glacier by folding and thrust faulting. We present model and field evidence from the terminus ofStorglaci¨aren, Sweden, showing that the cold margin provides limited resistance to flow from up-glacier.Ice temperatures indicate that basal freezing occurs in this zone at 10−1 –10−2 ma−1, but model resultsindicate that basal motion at rates greater than 1ma−1 must, nevertheless, persist there for surface andbasal velocities to be consistent with measurements. Estimated longitudinal compressive stresses of 20–25 kPa within the terminus further indicate that basal resistance offered by the cold-based terminusis small. These results indicate that where polythermal glaciers are underlain by unlithified sediments,ice-flow trajectories and sediment transport pathways may be affected by subglacial topography andhydrology more than by the basal thermal regime

  • 32. Moore, Peter L.
    et al.
    Iverson, Neal R.
    Cohen, Denis O.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Compressional tectonics in a polythermal glacier terminus2007In: 2007 GSA Denver Annual Meeting (28–31 October 2007), 2007Conference paper (Other (popular science, discussion, etc.))
  • 33. Moore, Peter L.
    et al.
    Iverson, Neal R.
    Uno, Kevin T.
    Dettinger, Matthew P.
    Brugger, Keith A.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Entrainment and emplacement of englacial debris bands near the margin of Storglaciären, Sweden2013In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 42, no 1, 71-83 p.Article in journal (Refereed)
    Abstract [en]

    Internal structure, stable isotope composition and tritium concentration were measured in and around debrisbearingice at the margin of Storglaciären, where englacial debris bands have previously been inferred to form bythrusting. Two types of debris bands were distinguished: (i) an unsorted diamicton band that is laterally continuousfor more than 200 m, and (ii) well-sorted sand and gravel bands that are lenticular and discontinuous.Above-background tritium levels and enrichment of d18O and dD in ice from the diamicton band indicateentrainment by basal freeze-on since 1952. Isotopic enrichment and tritium-free ice in the sandy debris bands alsoindicate entrainment in freezing water, but prior to 1952. The lenticular cross-section, sorting and stratification ofthe sandy bands suggest that they were deposited englacially. The basally accreted diamicton band has beenelevated tens of metres above the bed and presently overlies the englacially deposited sandy bands, suggesting thatthe stratigraphy has been disrupted. Three interpretations could account for these observations: (i) thrusting offast-moving ice over slow, marginal ice uplifting recently accreted basal ice along the fault; (ii) folding near themargin, elevating young basal ice over older basal and englacial ice; and (iii) debris-band formation by anunknown mechanism and subsequent contamination of ice geochemical properties by meltwater flow throughdebris bands. Although none of these interpretations is consistent with all measurements, folding is mostcompatible with observations and local ice-flow kinematics.

  • 34. Näslund, Jens-Ove
    et al.
    Wohlfarth, Barbara
    Stockholm University, Faculty of Science, Department of Geology and Geochemistry.
    Alexanderson, Helena
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Helmens, Karin
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hättestrand, Martina
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Kleman, Johan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Lundqvist, Jan
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Brandefelt, Jenny
    Houmark-Nielsen, Michael
    Kjellström, Erik
    Strandberg, Gustav
    Knudsen, Karen-Luise
    Krog Larsen, Nikolai
    Ukkonen, Pirkko
    Mangerud, Jan
    Fennoscandian paleo-environment and ice sheet dynamics during Marine Isotope Stage (MIS) 3: Report of a workshop held September 20–21, 2007 in Stockholm, Sweden2008Report (Other academic)
  • 35.
    Pettersson, Rickard
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Peter
    Blatter, Heinz
    Spatial variability in water content at the cold-temperate transition surface of the polythermal Storglaciären, Sweden2004In: Journal of Geophysical Research, ISSN 0148-0227, Vol. 109, no F02009Article in journal (Refereed)
    Abstract [en]

    The volume fraction of liquid water in temperate glacier ice is important not only for the flow of glaciers and the analysis and processing of ground penetrating radar data from glaciers but also for the stability of the thermal layering in polythermal glaciers. However, little is known about the spatial variations of water content in glaciers. We use relative backscatter strength of ground-penetrating radar signals to estimate the spatial distribution of water content close to the cold-temperate transition on Storglaciären, northern Sweden, in an area close to the equilibrium line. The values of relative backscatter strength are calibrated using determinations of absolute water content from temperature measurements across the cold-temperate transition and the thermodynamic boundary condition at the freezing front. The results show a water content of 0.80%, 0.75%, and 0.58% at three calibration points and a mean water content of 0.8% with a standard deviation of ±0.26% for the extrapolated water content. The extrapolated water content shows a distinct pattern, with lower water content on one side of the glacier center line and higher water content on the other side, with higher water content on the northern side. We hypothesize that the different water contents result from the fact that the ice on either side of the center line originates from different cirques, thus implying spatial variations in the entrapment of water in the firn-ice transition process in the different cirques.

  • 36.
    Pettersson, Rickard
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Holmlund, Per
    Cold surface layer thinning on Storglaciären, Sweden, observed by repeated ground penetrating radar surveys2003In: Journal of Geophysical Research, ISSN 0148-0227, Vol. 108, no F1, 5.1-5.9 p.Article in journal (Refereed)
    Abstract [en]

    A characteristic feature of ground penetrating radar (GPR) surveys on polythermal glaciers is an internal reflection presumably caused by the cold temperate transition surface (CTS), hence providing a possible tool for mapping thermal structure with high accuracy. Comparison of detailed temperature measurements in bore holes and GPR profiles at 345 MHz and 800 MHz center frequencies on Storglaciären, Sweden, show that the CTS can be detected and mapped with an accuracy of about ±1 m at both frequencies. A comparison between comprehensive GPR surveys of the cold surface layer, separated by 12 years (1989-2001), shows a substantial and complex thinning of the cold layer. An overall decrease of 8.3 m (22% of average thickness) of the CTS depth is much larger than uncertainties in CTS depth determinations. The stability of the cold surface layer depends on the net ice ablation at the surface and the downward migration of CTS. There is no evidence of substantial increased net ablation between the survey dates that could explain the observed thinning. However, small increase in average winter air temperature, a limiting factor for the temperature gradient through the cold surface layer, may provide a partial explanation. The weaker temperature gradient reduces the transport of latent heat from the CTS, thus slowing down its downward migration.

  • 37.
    Pettersson, Rickard
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology. Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Huwald, Hendrik
    Blatter, Heinz
    Spatial pattern and stability of the cold surface layer of Storglaciären, Sweden2007In: Journal of Glaciology, ISSN 0022-1430, Vol. 53, no 180, 99-109 p.Article in journal (Refereed)
    Abstract [en]

    The mechanisms controlling the spatial distribution and temporal fluctuations of the thermal structure in polythermal glaciers have, to date, been poorly investigated and are not fully understood. We have investigated the sensitivity of the cold surface layer thickness to different forcing parameters and the causes for an observed thinning of the cold surface layer on Storglacia¨ren, northern Sweden, between 1989 and 2001 using a one-dimensional thermomechanical model and measurements

    of ice surface temperature, vertical velocity and net mass balance. Similarities between the spatial patterns of the cold surface layer, net mass balance and emergence velocity together with modelled high sensitivity to variations in emergence velocities suggest that the net ablation and vertical ice advection are the dominant forcing parameters. Results from transient model experiments suggest that the cold surface layer reaches a new equilibrium after a perturbation in the forcing within a few decades. No significant change in ice flow or mass balance has been observed at Storglacia¨ren in recent decades.

    Instead, an increase of 18C in winter air temperature since the mid-1980s is probably the cause of the observed thinning of the cold surface layer. Increased winter temperatures at the ice surface result in a reduced formation rate of cold ice at the base of the cold surface layer and lead to a larger imbalance between net loss of ice at the surface and freezing of temperate ice at the cold–temperate transition surface. Model results indicate that the cold surface layer is more sensitive to changes in ice surface temperature in areas with lower emergence velocity, which explains the observed complex thinning pattern of the cold surface layer.

  • 38.
    Sannel, A. Britta K.
    et al.
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Hugelius, Gustaf
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Kuhry, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography.
    Permafrost Warming in a Subarctic Peatland - Which Meteorological Controls are Most Important?2016In: Permafrost and Periglacial Processes, ISSN 1045-6740, E-ISSN 1099-1530, Vol. 27, no 2, 177-188 p.Article in journal (Refereed)
    Abstract [en]

    Because climate change can affect the carbon balance and hydrology in permafrost peatlands, a better understanding of their sensitivity to changes in temperature and precipitation is needed. In Tavvavuoma, northernmost Sweden, meteorological parameters and ground thermal properties have been monitored in a peat plateau from 2006 to 2013. During this time period, the air temperature record shows no warming trend, and the late-season thaw depth has been relatively stable at around 55-60cm. Meanwhile, the mean annual ground temperature at 1m depth has increased by 0.06 degrees C/yr and at 2-5m depth the permafrost is currently warmer than -0.3 degrees C. Statistical analyses suggest that interannual changes in thaw depth and ground temperatures are affected by different meteorological factors. Summer air temperatures and annual thawing degree-days control thaw depth (p0.05), whereas winter precipitation/snow depth affects ground temperatures (p0.1). The permafrost in this peat plateau is likely relict and not in equilibrium with current climatic conditions. Since the early 20(th) century, there has been a regional increase in air temperature and snow depth. If the ongoing permafrost warming in Tavvavuoma is a result of these long-term trends, short-term variability in meteorological parameters can still have an impact on the rate of permafrost degradation, but unless pronounced climate cooling occurs, thawing of the peat plateau is inevitable.

  • 39. Schannwell, Clemens
    et al.
    Murray, Tavi
    Kulessa, Bernd
    Gusmeroli, Alessio
    Saintenoy, Albane
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    An automatic approach to delineate the cold-temperate transition surface with ground-penetrating radar on polythermal glaciers2014In: Annals of Glaciology, ISSN 0260-3055, E-ISSN 1727-5644, Vol. 55, no 67, 89-96 p.Article in journal (Refereed)
    Abstract [en]

    Ground-penetrating radar has been widely used to map the thermal structure of polythermal glaciers. Hitherto, the cold temperate transition surface (CTS) in radargrams has been identified by a labour-intensive and subjective manual picking method. We introduce a new automatic approach for picking the CTS that uses the difference in signal power exhibited by the cold and temperate ice layers. We compare our automatically computed CTS depths with manual picks. Our results show very good agreement between the two methods in most areas (r(2) > 0.7). RMSEs computed at each trace in two-way travel-time from three test sites range from 14 to 19 ns (2.4-3.2 m). The proposed automated method mostly fails in areas showing a rather gradual transition in signal power at the CTS. In some areas, high power originating from non-water sources is misinterpreted by the automatic picking method as 'temperate ice'.

  • 40. Zemp, M.
    et al.
    Thibert, E.
    Huss, M.
    Stumm, D.
    Denby, C. Rolstad
    Nuth, C.
    Nussbaumer, S. U.
    Moholdt, G.
    Mercer, Andrew
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Mayer, C.
    Joerg, P. C.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology.
    Hynek, B.
    Fischer, A.
    Escher-Vetter, H.
    Elvehoy, H.
    Andreassen, L. M.
    Reanalysing glacier mass balance measurement series2013In: The Cryosphere, ISSN 1994-0416, E-ISSN 1994-0424, Vol. 7, no 4, 1227-1245 p.Article in journal (Refereed)
    Abstract [en]

    Glacier-wide mass balance has been measured for more than sixty years and is widely used as an indicator of climate change and to assess the glacier contribution to runoff and sea level rise. Until recently, comprehensive uncertainty assessments have rarely been carried out and mass balance data have often been applied using rough error estimation or without consideration of errors. In this study, we propose a framework for reanalysing glacier mass balance series that includes conceptual and statistical toolsets for assessment of random and systematic errors, as well as for validation and calibration (if necessary) of the glaciological with the geodetic balance results. We demonstrate the usefulness and limitations of the proposed scheme, drawing on an analysis that comprises over 50 recording periods for a dozen glaciers, and we make recommendations to investigators and users of glacier mass balance data. Reanalysing glacier mass balance series needs to become a standard procedure for every monitoring programme to improve data quality, including reliable uncertainty estimates.

  • 41.
    Zemp, Michael
    et al.
    Department of Geography, University of Zurich.
    Jansson, Peter
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Holmlund, Per
    Stockholm University, Faculty of Science, Department of Physical Geography and Quaternary Geology (INK).
    Gärtner-Roer, Ingrid
    Department of Geography, University of Zurich.
    Koblet, Thomas
    Department of Geography, University of Zurich.
    Thee, Patrick
    Department of Geography, University of Zurich.
    Haeberli, Wilfried
    Department of Geography, University of Zurich.
    Reanalysis of multi-temporal aerial images of Storglaciären, Sweden (1959-1999) – Part 2: Comparison of glaciological and volumetric mass balances2010In: The Cryosphere, Vol. 4, 345-357 p.Article in journal (Refereed)
    Abstract [en]

    Seasonal glaciological mass balances have been measured on Storglaciären without interruption since 1945/46. In addition, aerial surveys have been carried out on a decadal basis since the beginning of the observation program. Early studies had used the resulting aerial photographs to produce topographic glacier maps with which the in-situ observations could be verified. However, these maps as well as the derived volume changes are subject to errors which resulted in major differences between the derived volumetric and the glaciological mass balance. As a consequence,the original photographs were re-processed using uniform photogrammetric methods, which resulted in new volumetric mass balances for 1959–69, 1969–80, 1980–90, and 1990–99. We compared these new volumetric mass balances with mass balances obtained by standard glaciological methods including an uncertainty assessment considering all related previous studies. The absolute differences between volumetric and the glaciological mass balances are 0.8 m w.e. for theperiod of 1959–69 and 0.3 m w.e. or less for the other survey periods. These deviations are slightly reduced when considering corrections for systematic uncertainties due to differences in survey dates, reference areas, and internal ablation, whereas internal accumulation systematically increases the mismatch. However, the mean annual differences between glaciological and volumetric mass balance are less than the uncertainty of the in-situ stake reading and stochastic error bars of both data series overlap. Hence, no adjustment of the glaciological data series to the volumetric one is required.

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