Temperature signal in suspended sediment export from an Alpine catchment

Abstract. Suspended sediment export from large Alpine catchments ( >  1000 km 2) over decadal timescales is sensitive to a number of factors, including long-term variations in climate, the activation–deactivation of different sediment sources (proglacial areas, hillslopes, etc.), transport through the fluvial system, and potential anthropogenic impacts on the sediment flux (e.g. through impoundments and flow regulation). Here, we report on a marked increase in suspended sediment concentrations observed near the outlet of the upper Rhone River Basin in the mid-1980s. This increase coincides with a statistically significant step-like increase in basin-wide mean air temperature. We explore the possible explanations of the suspended sediment rise in terms of changes in water discharge (transport capacity), and the activation of different potential sources of fine sediment (sediment supply) in the catchment by hydroclimatic forcing. Time series of precipitation and temperature-driven snowmelt, snow cover, and ice melt simulated with a spatially distributed degree-day model, together with erosive rainfall on snow-free surfaces, are tested to explore possible reasons for the rise in suspended sediment concentration. We show that the abrupt change in air temperature reduced snow cover and the contribution of snowmelt, and enhanced ice melt. The results of statistical tests show that the onset of increased ice melt was likely to play a dominant role in the suspended sediment concentration rise in the mid-1980s. Temperature-driven enhanced melting of glaciers, which cover about 10 % of the catchment surface, can increase suspended sediment yields through an increased contribution of sediment-rich glacial meltwater, increased sediment availability due to glacier recession, and increased runoff from sediment-rich proglacial areas. The reduced extent and duration of snow cover in the catchment are also potential contributors to the rise in suspended sediment concentration through hillslope erosion by rainfall on snow-free surfaces, and increased meltwater production on snow-free glacier surfaces. Despite the rise in air temperature, changes in mean discharge in the mid-1980s were not statistically significant, and their interpretation is complicated by hydropower reservoir management and the flushing operations at intakes. Overall, the results show that to explain changes in suspended sediment transport from large Alpine catchments it is necessary to include an understanding of the multitude of sediment sources involved together with the hydroclimatic conditioning of their activation (e.g. changes in precipitation, runoff, air temperature). In addition, this study points out that climate signals in suspended sediment dynamics may be visible even in highly regulated and human-impacted systems. This is particularly relevant for quantifying climate change and hydropower impacts on streamflow and sediment budgets in Alpine catchments.

[1]  Luca Mao,et al.  Temporal dynamics of suspended sediment transport in a glacierized Andean basin , 2017 .

[2]  Stuart N. Lane,et al.  Sediment export, transient landscape response and catchment-scale connectivity following rapid climate warming and Alpine glacier recession , 2017 .

[3]  Panos Panagos,et al.  Regionalization of monthly rainfall erosivity patterns in Switzerland , 2016 .

[4]  Stuart N. Lane,et al.  Water yield and sediment export in small, partially glaciated Alpine watersheds in a warming climate , 2016 .

[5]  Panos Panagos,et al.  Seasonal Dynamics of Rainfall Erosivity in Switzerland , 2016 .

[6]  Matthias Huss,et al.  Sensitivity of Very Small Glaciers in the Swiss Alps to Future Climate Change , 2016, Front. Earth Sci..

[7]  Stuart N. Lane,et al.  Ecosystem impacts of Alpine water intakes for hydropower: the challenge of sediment management , 2016 .

[8]  F. Schlunegger,et al.  Lithological control on the landscape form of the upper Rhône Basin, Central Swiss Alps , 2016 .

[9]  T. Turkington,et al.  Landslides and synoptic weather trends in the European Alps , 2016, Climatic Change.

[10]  A. Navas,et al.  Land use sediment production response under different climatic conditions in an alpine–prealpine catchment , 2016 .

[11]  Stuart N. Lane,et al.  Investigating decadal‐scale geomorphic dynamics in an alpine mountain setting , 2015 .

[12]  Matthias Huss,et al.  A new model for global glacier change and sea-level rise , 2015, Front. Earth Sci..

[13]  Peter Molnar,et al.  High-resolution distributed analysis of climate and anthropogenic changes on the hydrology of an Alpine catchment , 2015 .

[14]  Stuart N. Lane,et al.  Erosion by an Alpine glacier , 2015, Science.

[15]  John Wainwright,et al.  Sediment connectivity: a framework for understanding sediment transfer at multiple scales , 2015 .

[16]  M. Hoelzle,et al.  Surface elevation and mass changes of all Swiss glaciers 1980–2010 , 2014 .

[17]  C. Schär,et al.  Climate change in Switzerland: a review of physical, institutional, and political aspects , 2014 .

[18]  Yongtao Cao,et al.  Sustainable sediment management in reservoirs and regulated rivers: Experiences from five continents , 2014 .

[19]  D. Bourlès,et al.  Mid-Holocene cluster of large-scale landslides revealed in the Southwestern Alps by 36Cl dating. Insight on an Alpine-scale landslide activity , 2014 .

[20]  C. Frei.  Interpolation of temperature in a mountainous region using nonlinear profiles and non‐Euclidean distances , 2014 .

[21]  G. Ravazzani,et al.  Integrating glaciers raster‐based modelling in large catchments hydrological balance: the Rhone case study , 2014 .

[22]  Rolf Weingartner,et al.  Snow variability in the Swiss Alps 1864–2009 , 2013 .

[23]  Lijuan Wen,et al.  Impact of rain snow threshold temperature on snow depth simulation in land surface and regional atmospheric models , 2013, Advances in Atmospheric Sciences.

[24]  Jeffrey R. Moore,et al.  Sediment Transport and Bedrock Erosion by Wet Snow Avalanches in the Guggigraben, Matter Valley, Switzerland , 2013 .

[25]  M. R. van den Broeke,et al.  A Reconciled Estimate of Glacier Contributions to Sea Level Rise: 2003 to 2009 , 2013, Science.

[26]  Lorenzo Marchi,et al.  Geomorphometric assessment of spatial sediment connectivity in small Alpine catchments , 2013 .

[27]  P. V. Beek,et al.  Transient sediment supply in a high‐altitude Alpine environment evidenced through a 10Be budget of the Etages catchment (French Western Alps) , 2013 .

[28]  F. Schlunegger,et al.  River loads and modern denudation of the Alps — A review , 2013 .

[29]  T. Heckmann,et al.  Geomorphic coupling and sediment connectivity in an alpine catchment - exploring sediment cascades using graph theory , 2013 .

[30]  Matthias Huss,et al.  Distributed ice thickness and volume of all glaciers around the globe , 2012 .

[31]  Peter Molnar,et al.  Erosional power in the Swiss Alps: characterization of slope failure in the Illgraben , 2012 .

[32]  H. Fowler,et al.  Using the UKCP09 probabilistic scenarios to model the amplified impact of climate change on drainage basin sediment yield , 2012 .

[33]  Martin Funk,et al.  Runoff evolution in the Swiss Alps: projections for selected high‐alpine catchments based on ENSEMBLES scenarios , 2012 .

[34]  John J. Clague,et al.  Is climate change responsible for changing landslide activity in high mountains? , 2012 .

[35]  G. Jouvet,et al.  Modelling the retreat of Grosser Aletschgletscher, Switzerland, in a changing climate , 2011, Journal of Glaciology.

[36]  Panos Panagos,et al.  Spatial and temporal variability of rainfall erosivity factor for Switzerland , 2011 .

[37]  M. Rebetez,et al.  Seasonal trends and temperature dependence of the snowfall/precipitation‐day ratio in Switzerland , 2011 .

[38]  Andreas Bauder,et al.  Future high-mountain hydrology: a new parameterization of glacier retreat , 2010 .

[39]  J. Hornung,et al.  3-D architecture, depositional patterns and climate triggered sediment fluxes of an alpine alluvial fan (Samedan, Switzerland) , 2010 .

[40]  M. Mancini,et al.  Elevation based correction of snow coverage retrieved from satellite images to improve model calibration , 2009 .

[41]  S. Carey,et al.  Towards an energy‐based runoff generation theory for tundra landscapes , 2008 .

[42]  A. Bauder,et al.  Modelling runoff from highly glacierized alpine drainage basins in a changing climate , 2008 .

[43]  P. V. Beek,et al.  Increase in late Neogene denudation of the European Alps confirmed by analysis of a fission-track thermochronology database , 2008 .

[44]  C. Marty.  Regime shift of snow days in Switzerland , 2008 .

[45]  R. Hock,et al.  Determination of the seasonal mass balance of four Alpine glaciers since 1865 , 2008 .

[46]  M. Rebetez,et al.  Monthly air temperature trends in Switzerland 1901–2000 and 1975–2004 , 2008 .

[47]  Frank Paul,et al.  Glacier fluctuations in the European Alps, 1850–2000: an overview and spatio-temporal analysis of available data , 2008 .

[48]  M. Hoelzle,et al.  Integrated monitoring of mountain glaciers as key indicators of global climate change: the European Alps , 2007, Annals of Glaciology.

[49]  D. Finger,et al.  Effects of Alpine hydropower dams on particle transport and lacustrine sedimentation , 2007, Aquatic Sciences.

[50]  Andreas Kääb,et al.  Recent glacier changes in the Alps observed by satellite: Consequences for future monitoring strategies , 2007 .

[51]  W. Briggs.  Statistical Methods in the Atmospheric Sciences , 2007 .

[52]  Omri Allouche,et al.  Assessing the accuracy of species distribution models: prevalence, kappa and the true skill statistic (TSS) , 2006 .

[53]  C. Appenzeller,et al.  Swiss alpine snow pack variability: Major patterns and links to local climate and large-scale flow , 2006 .

[54]  A. Wüest,et al.  Effects of upstream hydropower operation on riverine particle transport and turbidity in downstream lakes , 2006 .

[55]  Anton Van Rompaey,et al.  Predicting catchment sediment yield in Mediterranean environments: the importance of sediment sources and connectivity in Italian drainage basins , 2006 .

[56]  C. Frei,et al.  Future change of precipitation extremes in Europe: Intercomparison of scenarios from regional climate models , 2006 .

[57]  Santiago Beguería,et al.  Validation and Evaluation of Predictive Models in Hazard Assessment and Risk Management , 2006 .

[58]  Martin Funk,et al.  An enhanced temperature-index glacier melt model including the shortwave radiation balance: development and testing for Haut Glacier d'Arolla, Switzerland , 2005 .

[59]  Reinhard Böhm,et al.  Temperature and precipitation variability in the European Alps since 1500 , 2005 .

[60]  B. Schaefli,et al.  Earth System , 2005 .

[61]  T. Hoey,et al.  Basal sediment evacuation by subglacial meltwater: suspended sediment transport from Haut Glacier d'Arolla, Switzerland , 2005 .

[62]  D. Walling.  Tracing suspended sediment sources in catchments and river systems. , 2005, The Science of the total environment.

[63]  J. Oerlemans.  Extracting a Climate Signal from 169 Glacier Records , 2005, Science.

[64]  J. Syvitski,et al.  Impact of Humans on the Flux of Terrestrial Sediment to the Global Coastal Ocean , 2005, Science.

[65]  Andreas Kääb,et al.  Rapid disintegration of Alpine glaciers observed with satellite data , 2004 .

[66]  C. Appenzeller,et al.  Trends in Swiss Alpine snow days: The role of local‐ and large‐scale climate variability , 2004 .

[67]  Peter Molnar,et al.  LATE CENOZOIC INCREASE IN ACCUMULATION RATES OF TERRESTRIAL SEDIMENT: How Might Climate Change Have Affected Erosion Rates? , 2004 .

[68]  A. Horowitz.  An evaluation of sediment rating curves for estimating suspended sediment concentrations for subsequent flux calculations , 2003 .

[69]  Mario Aristide Lenzi,et al.  Interannual variation of suspended sediment load and sediment yield in an alpine catchment , 2003 .

[70]  Regine Hock,et al.  Temperature index melt modelling in mountain areas , 2003 .

[71]  P. A. James,et al.  Meteorological and land use controls on past and present hydro‐geomorphic processes in the pre‐alpine environment: an integrated lake–catchment study at the Petit Lac d'Annecy, France , 2003 .

[72]  A. Lotter,et al.  Holocene vegetation development in the catchment of Sägistalsee ( 1935 m asl), a small lake in the Swiss Alps , 2003 .

[73]  M. Schneebeli,et al.  Long‐term snow climate trends of the Swiss Alps (1931–99) , 2003 .

[74]  M. Hoelzle,et al.  Secular glacier mass balances derived from cumulative glacier length changes , 2003 .

[75]  W. Haeberli,et al.  Alpine Glacier Mass Changes During the Past Two Millennia , 2003 .

[76]  P. Jones,et al.  Hemispheric and Large-Scale Surface Air Temperature Variations: An Extensive Revision and an Update to 2001. , 2003 .

[77]  C. Ballantyne.  A general model of paraglacial landscape response , 2002 .

[78]  F. Schlunegger,et al.  Crustal uplift in the Alps: why the drainage pattern matters , 2001 .

[79]  Peizhen Zhang,et al.  Increased sedimentation rates and grain sizes 2–4 Myr ago due to the influence of climate change on erosion rates , 2001, Nature.

[80]  N. Asselman.  Fitting and interpretation of sediment rating curves , 2000 .

[81]  L. Marchi,et al.  Suspended sediment load during floods in a small stream of the Dolomites (northeastern Italy) , 2000 .

[82]  Janusz Dominik,et al.  Evolution of the Upper Rhone River discharge and suspended sediment load during the last 80 years and some implications for Lake Geneva , 2000, Aquatic Sciences.

[83]  Nicholas E. Graham,et al.  Conditional Probabilities, Relative Operating Characteristics, and Relative Operating Levels , 1999 .

[84]  Martin Beniston,et al.  VARIATIONS OF SNOW DEPTH AND DURATION IN THE SWISS ALPS OVER THE LAST 50 YEARS: LINKS TO CHANGES IN LARGE-SCALE CLIMATIC FORCINGS , 1997 .

[85]  M. Rebetez,et al.  Regional behavior of minimum temperatures in Switzerland for the period 1979–1993 , 1996 .

[86]  B. Hallet,et al.  Rates of erosion and sediment evacuation by glaciers: A review of field data and their implications , 1996 .

[87]  Martin Beniston,et al.  An analysis of regional climate change in Switzerland , 1994 .

[88]  J. Loizeau,et al.  Particle size characteristics of suspended and bed sediments in the Rhône river , 1992 .

[89]  Peter Molnar,et al.  Surface uplift, uplift of rocks, and exhumation of rocks , 1990 .

[90]  E. Aas,et al.  Colors of glacier water , 1988 .

[91]  D. Walling.  Assessing the accuracy of suspended sediment rating curves for a small basin , 1977 .

[92]  A. H. Auer.  The Rain versus Snow Threshold Temperatures , 1974 .

[93]  J. Nash,et al.  River flow forecasting through conceptual models part I — A discussion of principles☆ , 1970 .

[94]  W. H. Wischmeier,et al.  A Rainfall Erosion Index for a Universal Soil-Loss Equation , 1959 .

[95]  F. B. Campbell,et al.  A rating‐curve method for determining silt‐discharge of streams , 1940 .

[96]  H. Löwe,et al.  Simulations of future snow cover and discharge in Alpine headwater catchments , 2009 .

[97]  N. Lamouroux,et al.  Chapter 7 – The Rhône River Basin , 2009 .

[98]  A. Kääb,et al.  ON THE IMPACT OF GLACIER ALBEDO UNDER CONDITIONS OF EXTREME GLACIER MELT: THE SUMMER OF 2003 IN THE ALPS , 2005 .

[99]  W. Collins,et al.  Description of the NCAR Community Atmosphere Model (CAM 3.0) , 2004 .

[100]  J. Oerlemans,et al.  Relating glacier mass balance to meteorological data by using a seasonal sensitivity characteristic , 2000, Journal of Glaciology.

[101]  J. Loizeau,et al.  Sediment Core Correlation and Mapping of Sediment Accumulation Rates in Lake Geneva (Switzerland, France) Using Volume Magnetic Susceptibility , 1997 .

[102]  G. R. Foster,et al.  storm Erosivity Using Idealized Intensity Distributions , 1987 .

[103]  G. H. Leavesley,et al.  Precipitation-runoff modeling system; user's manual , 1983 .

[104]  G. Boulton.  Processes and Patterns of Glacial Erosion , 1982 .

[105]  A. N. PETTrrr.  A Non-parametric Approach to the Change-point Problem , 1979 .

[106]  W. H. Wischmeier,et al.  Predicting rainfall erosion losses : a guide to conservation planning , 1978 .