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  • 1. Abbühl, Luca M.
    et al.
    Norton, Kevin P.
    Jansen, John D.
    Schlunegger, Fritz
    Aldahan, Ala
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Tandem Laboratory.
    Erosion rates and mechanisms of knickzone retreat inferred from (10)Be measured across strong climate gradients on the northern and central Andes Western Escarpment2011In: Earth Surface Processes and Landforms, ISSN 0197-9337, E-ISSN 1096-9837, Vol. 36, no 11, p. 1464-1473Article in journal (Refereed)
    Abstract [en]

    A steep escarpment edge, deep gorges and distinct knickzones in river profiles characterize the landscape on the Western Escarpment of the Andes between similar to 5 degrees S and similar to 18 degrees S (northern Peru to northern Chile). Strong north-south and east-west precipitation gradients are exploited in order to determine how climate affects denudation rates in three river basins spanning an otherwise relatively uniform geologic and geomorphologic setting. Late Miocene tectonics uplifted the Meseta/Altiplano plateau (similar to 3000 m a.s.l.), which is underlain by a series of Tertiary volcanic-volcanoclastic rocks. Streams on this plateau remain graded to the Late Miocene base level. Below the rim of the Meseta, streams have responded to this ramp uplift by incising deeply into fractured Mesozoic rocks via a series of steep, headward retreating knickzones that grade to the present-day base level defined by the Pacific Ocean. It is found that the Tertiary units on the plateau function as cap-rocks, which aid in the parallel retreat of the sharp escarpment edge and upper knickzone tips. (10)Be-derived catchment denudation rates of the Rio Piura (5 degrees S), Rio Pisco (13 degrees S) and Rio Lluta (18 degrees S) average similar to 10 mm ky(-1) on the Meseta/Altiplano, irrespective of precipitation rates; whereas, downstream of the escarpment edge, denudation rates range from 10 mm ky(-1) to 250 mm ky(-1) and correlate positively with precipitation rates, but show no strong correlation with hillslope angles or channel steepness. These relationships are explained by the presence of a cap-rock and climate-driven fluvial incision that steepens hillslopes to near-threshold conditions. Since escarpment retreat and the precipitation pattern were established at least in the Miocene, it is speculated that the present-day distribution of morphology and denudation rates has probably remained largely unchanged during the past several millions of years as the knickzones have propagated headward into the plateau.

  • 2. Gurnell, Angela M.
    et al.
    O'Hare, Matthew T.
    O'Hare, Judith M.
    Scarlett, Peter
    Liffen, Thomas M. R.
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Ecology and Genetics, Limnology.
    The geomorphological context and impact of the linear emergent macrophyte, Sparganium erectum L.: a statistical analysis of observations from British rivers2013In: Earth Surface Processes and Landforms, ISSN 0197-9337, E-ISSN 1096-9837, Vol. 38, no 15, p. 1869-1880Article in journal (Refereed)
    Abstract [en]

    This paper explores the geomorphological context and impact of the widely-occurring, linear emergent macrophyte, Sparganium erectum. Forty-seven sites across Britain were selected for field investigation, spanning the range of environmental conditions within which Sparganium erectum had been found to be present in previous analyses of national data sets. A combination of descriptive graphs and statistics, principal components analysis, and Kruskal-Wallis tests were used to explore the large multivariate data set collected at the 47 sites. The analyses showed that Sparganium erectum is present in significant quantities in relatively narrow and shallow (< 18m wide and<0.9m deep to the limit of terrestrial vegetation), low gradient (maximum 0.004) channels of varying bed sediment calibre (cobble to silt). Within these environments, S. erectum stands (features) were associated with fine sediment retention, aggradation and submerged landform construction, leading to bench development and so, potentially, to adjustments in channel form and position. Sediment retention and landform construction within S. erectum features was most strongly apparent within reaches with a relatively high S. erectum cover and the presence of large area S. erectum features. It was also associated more weakly with S. erectum features that were comprised of relatively higher densities of plants with relatively smaller inter-plant spacing and fewer leaves. The sediment retained in S. erectum features and associated bench and bank toe deposits showed larger numbers and species of viable seeds, indicating the potential for colonization and growth of other species on S. erectum features once they aggrade above the low flow water level and are no longer a suitable habitat for S. erectum.

  • 3. Lu, Huayu
    et al.
    Mason, Joseph A.
    Stevens, Thomas
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Zhou, Yali
    Yi, Shuangwen
    Miao, Xiaodong
    Response of surface processes to climatic change in the dunefields and Loess Plateau of North China during the late Quaternary2011In: Earth Surface Processes and Landforms, ISSN 0197-9337, E-ISSN 1096-9837, Vol. 36, no 12, p. 1590-1603Article in journal (Refereed)
  • 4.
    Petterson, Gunilla
    et al.
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Renberg, Ingemar
    Umeå universitet, Institutionen för ekologi, miljö och geovetenskap.
    Sjöstedt-de Luna, Sara
    Umeå universitet, Institutionen för matematik och matematisk statistik.
    Arnqvist, Per
    Umeå universitet, Institutionen för matematik och matematisk statistik.
    Anderson, N. John
    Loughborough University.
    Climatic influence on the inter-annual variability of late-Holocene minerogenic sediment supply in a boreal forest catchment2010In: Earth Surface Processes and Landforms, ISSN 0197-9337, E-ISSN 1096-9837, Vol. 35, no 4, p. 390-398Article in journal (Refereed)
    Abstract [en]

    Processes controlling sediment yield vary over a range of timescales, although most process-based observations are extremely short. Lake sediments, however, can be used to extend the observational timescale and are particularly useful when annually laminated (varved) sediment is present. The sediment record at Kassjön (N. Sweden) consists of ∼6400 varves, each 0·5–1 mm thick. Image analysis was used to determine grey-scale variation and varve thickness from which annual minerogenic accumulation rate (MinAR) (mg cm−2 year−1) was inferred for the period 4486 BC – AD 1900. MinAR varies on annual to centennial scales and mainly reflects channel bank erosion by the inflow streams. The mineral input reflects the intensity of the spring run-off, which is dependent on the amount of snow accumulated during the winter, and hence MinAR is a long-term record of variability in past winter climate; other factors will be a variable response to catchment uplift, vegetation succession and pedogenesis. A major shift from low to high MinAR occurred ∼250 BC, and peaks occurred around AD 250, 600, 1000, 1350 and 1650. Wavelet power spectrum analysis (confirmed by Fourier analyses) indicated significantly different periodicities throughout the period 4000 BC – AD 1700, including 275 years for the period 4000 BC – 2900 BC, 567 years for the period 2901 BC – 1201 BC, and 350 and 725 years for the period 1200 BC – AD 1700. The long-term, centennial scale variability (∼350 years) may reflect solar forcing (cf the 385-year peak in tree-ring calibrated 14C activity) but interestingly, there is no obvious link to high frequency forcing, such as the North Atlantic Oscillation. The high resolution component of the record highlights the relevance of varved lake sediment records for understanding erosion dynamics in undisturbed forested catchments and their link to long-term climate dynamics and future climate change. 

  • 5.
    Ridefelt, Hanna
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences.
    Boelhouwers, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences. Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Social and Economic Geography.
    Eiken, Trond
    Department of Geosciences, University of Oslo.
    Measurement of solifluction rates using multi-temporal aerial photography2009In: Earth Surface Processes and Landforms, ISSN 0197-9337, E-ISSN 1096-9837, Vol. 34, no 5, p. 725-737Article in journal (Refereed)
    Abstract [en]

    A new method is presented to assess decadal solifluction lobe movement and volumetric changes at the catchmentscale. The method is based on photogrammetrical analysis of orthorectified repeat aerial photography in a geographic informationsystem (GIS). High resolution aerial photographs from two valleys in northern Sweden, Kärkevagge and Låktatjåkka valleys,are used to quantify changes of the lobe fronts, as an indication of solifluction rates over a period of 41 years. Two methods areexplored, the flow direction method and the front line method, in order to quantify the movement rates. Results show thatthe maximum combined root mean square error (RMSE) and resolution error amount to c. 1·7 m; no clear preference of onemeasurement method over the other was found. Application potential of the method is promising but reliability depends on themovement rates of the landforms and sufficient time span between the images. In the pilot study the measured yearly movementover the period 1959–2000 ranges from not-detectable to 63 mm/yr. Not-detectable means that movement cannot be detectedwithin the resolution used in the study. Lobe advance rates are similar to measured surface movement rates and volumetricsediment flux by solifluction is found to be considerably lower than a previous estimate by Rapp (1960). Implications for lobeadvance models are discussed. Photogrammetrical analysis is recommended as an important tool for detecting decadalsolifluction movement at the catchment scale.

  • 6.
    Ridefelt, Hanna
    et al.
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Social and Economic Geography.
    Boelhouwers, Jan
    Uppsala University, Disciplinary Domain of Humanities and Social Sciences, Faculty of Social Sciences, Department of Social and Economic Geography.
    Etzelmüller, Bernd
    University of Oslo, Norway.
    Local variations of solifluction activity and environment in the Abisko Mountains, northern Sweden2011In: Earth Surface Processes and Landforms, ISSN 0197-9337, E-ISSN 1096-9837, Vol. 36, no 15, p. 2042-2053Article in journal (Refereed)
    Abstract [en]

    Seven sites within the mountain region of Abisko, northern Sweden, were selected for measurement of solifluction movement rates and correlation with the local environmental factors. Grids with sizes from 20 m x 30 m to 50 m x 100 m included both solifluction landforms and adjacent ground. Positions of movement markers and the terrain were recorded and the grid areas were digitally reconstructed. This allowed topography, vegetation and soil texture (fraction of fine material) surfaces to be interpolated and used together with data on soil moisture in statistical analyses. Significant correlations differ from site to site indicating that environmental factors have varying importance and inter-relations depending on the local setting. Geomorphic work was also assessed within the grids. The results indicate measurable geomorphic work where no landforms are present. These areas may make larger contributions to sediment displacement than where solifluction landforms exist. Solifluction is an important denudational agent in the region and has its greatest impact on landscape development in the western part of the region.

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