Saharan dust events in the European Alps: role in snowmelt and geochemical characterization

Abstract. The input of mineral dust from arid regions impacts snow optical properties. The induced albedo reduction generally alters the melting dynamics of the snowpack, resulting in earlier snowmelt. In this paper, we evaluate the impact of dust depositions on the melting dynamics of snowpack at a high-elevation site (2160 m) in the European Alps (Torgnon, Aosta Valley, Italy) during three hydrological years (2013–2016). These years were characterized by several Saharan dust events that deposited significant amounts of mineral dust in the European Alps. We quantify the shortening of the snow season due to dust deposition by comparing observed snow depths and those simulated with the Crocus model accounting, or not, for the impact of impurities. The model was run and tested using meteorological data from an automated weather station. We propose the use of repeated digital images for tracking dust deposition and resurfacing in the snowpack. The good agreement between model prediction and digital images allowed us to propose the use of an RGB index (i.e. snow darkening index – SDI) for monitoring dust on snow using images from a digital camera. We also present a geochemical characterization of dust reaching the Alpine chain during spring in 2014. Elements found in dust were classified as a function of their origin and compared with Saharan sources. A strong enrichment in Fe was observed in snow containing Saharan dust. In our case study, the comparison between modelling results and observations showed that impurities deposited in snow anticipated the disappearance of snow up to 38 d a out of a total 7 months of typical snow duration. This happened for the season 2015–2016 that was characterized by a strong dust deposition event. During the other seasons considered here (2013–2014 and 2014–2015), the snow melt-out date was 18 and 11 d earlier, respectively. We conclude that the effect of the Saharan dust is expected to reduce snow cover duration through the snow-albedo feedback. This process is known to have a series of further hydrological and phenological feedback effects that should be characterized in future research.

[1]  P. Formenti,et al.  Spectral- and size-resolved mass absorption efficiency of mineral dust aerosols in the shortwave spectrum: a simulation chamber study , 2017 .

[2]  P. Seibert,et al.  A study of an outstanding Saharan dust event at the high-alpine site Jungfraujoch, Switzerland , 1995 .

[3]  T. Painter,et al.  Contemporary geochemical composition and flux of aeolian dust to the San Juan Mountains, Colorado, United States , 2010 .

[4]  M. Rossini,et al.  Using digital repeat photography and eddy covariance data to model grassland phenology and photosynthetic CO2 uptake , 2011 .

[5]  C. Schwierz,et al.  The transport history of two Saharan dust events archived in an Alpine ice core , 2019 .

[6]  Geomorphologic approach for modelling the surface features of arid environments in a model of dust emissions: application to the Sahara desert , 2000 .

[7]  F. Anselmetti,et al.  Mineral dust and elemental black carbon records from an Alpine ice core (Colle Gnifetti glacier) over the last millennium , 2009 .

[8]  E. Brun,et al.  A numerical model to simulate snow-cover stratigraphy for operational avalanche forecasting , 1992, Journal of Glaciology.

[9]  Bernhard Peucker-Ehrenbrink,et al.  Anthropogenic disturbance of element cycles at the Earth's surface. , 2012, Environmental science & technology.

[10]  J. Seinfeld,et al.  Radiative forcing by mineral dust aerosols : sensitivity to key variables , 1998 .

[11]  B. DeAngelo,et al.  Bounding the role of black carbon in the climate system: A scientific assessment , 2013 .

[12]  Paul M. Thompson,et al.  Phenological sensitivity to climate across taxa and trophic levels , 2016, Nature.

[13]  S. Decesari,et al.  Ground level ice nuclei particle measurements including Saharan dust events at a Po Valley rural site (San Pietro Capofiume, Italy) , 2017 .

[14]  C. Riebe,et al.  Global patterns of dust and bedrock nutrient supply to montane ecosystems , 2017, Science Advances.

[15]  H. Ólafsson,et al.  Snow–Dust Storm: Unique case study from Iceland, March 6–7, 2013 , 2015 .

[16]  D. Lawrence,et al.  Observed 20th century desert dust variability: Impact on climate and biogeochemistry , 2010 .

[17]  M. Beniston,et al.  Snow pack in the Swiss Alps under changing climatic conditions: an empirical approach for climate impacts studies , 2003 .

[18]  G. Baccolo,et al.  Low-background neutron activation analysis: a powerful tool for atmospheric mineral dust analysis in ice cores , 2015, Journal of Radioanalytical and Nuclear Chemistry.

[19]  M. R. van den Broeke,et al.  Retreating alpine glaciers: increased melt rates due to accumulation of dust (Vadret da Morteratsch, Switzerland) , 2009, Journal of Glaciology.

[20]  K. Sellegri,et al.  The high field strength element budget of atmospheric aerosols (puy de Dôme, France) , 2015 .

[21]  J. Hansen,et al.  Soot climate forcing via snow and ice albedos. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[22]  P. Formenti,et al.  Dust aerosol radiative effects during summer 2012 simulated with a coupled regional aerosol–atmosphere–ocean model over the Mediterranean , 2014 .

[23]  A. Lacis,et al.  The influence on climate forcing of mineral aerosols from disturbed soils , 1996, Nature.

[24]  J. Zeyer,et al.  Bacterial Composition and Survival on Sahara Dust Particles Transported to the European Alps , 2015, Front. Microbiol..

[25]  Paola Formenti,et al.  Iron oxides and light absorption by pure desert dust: An experimental study , 2004 .

[26]  Hamish A. McGowan,et al.  Scavenging of atmospheric trace metal pollutants by mineral dusts: Inter-regional transport of Australian trace metal pollution to New Zealand , 2008 .

[27]  P. Ginoux.  Atmospheric chemistry: Warming or cooling dust? , 2017 .

[28]  F. Prodi,et al.  A case of transport and deposition of Saharan dust over the Italian Peninsula and southern Europe , 1979 .

[29]  M. Shahgedanova,et al.  High-resolution provenance of desert dust deposited on Mt. Elbrus, Caucasus in 2009–2012 using snow pit and firn core records , 2013 .

[30]  Kent Rhodes,et al.  Morphological and Chemical Characteristics of Airborne Tungsten Particles of Fallon, Nevada , 2007, Microscopy and Microanalysis.

[31]  B. Delmonte,et al.  Variability of Anthropogenic and Natural Compounds in High Altitude–high Accumulation Alpine Glaciers , 2006, Hydrobiologia.

[32]  C. Riebe,et al.  Dust outpaces bedrock in nutrient supply to montane forest ecosystems , 2017, Nature Communications.

[33]  E. A. N. Fernandes,et al.  Neutron activation analysis: A primary method of measurement , 2011 .

[34]  T. Painter,et al.  The ecology of dust , 2010 .

[35]  W. Schöner,et al.  Contribution of Saharan Dust to Ion Deposition Loads of High Alpine Snow Packs in Austria (1987–2017) , 2018, Front. Earth Sci..

[36]  J. Gabrieli,et al.  19th century glacier retreat in the Alps preceded the emergence of industrial black carbon deposition on high-alpine glaciers , 2018, The Cryosphere.

[37]  Mark E. Miller,et al.  Composition of dust deposited to snow cover in the Wasatch Range (Utah, USA): Controls on radiative properties of snow cover and comparison to some dust-source sediments , 2014 .

[38]  Thomas H. Painter,et al.  Dust radiative forcing in snow of the Upper Colorado River Basin: 2. Interannual variability in radiative forcing and snowmelt rates , 2012 .

[39]  M. Beniston.  Mountain Climates and Climatic Change: An Overview of Processes Focusing on the European Alps , 2005 .

[40]  P. Rasch,et al.  Carbonaceous aerosols recorded in a southeastern Tibetan glacier: analysis of temporal variations and model estimates of sources and radiative forcing , 2015 .

[41]  M. Migliavacca,et al.  Heat wave hinders green wave: The impact of climate extreme on the phenology of a mountain grassland , 2017 .

[42]  H. Fischer,et al.  Proxies and measurement techniques for mineral dust in Antarctic ice cores. , 2008, Environmental science & technology.

[43]  Pinhas Alpert,et al.  Predominant transport paths of Saharan dust over the Mediterranean Sea to Europe , 2012 .

[44]  M. Schnaiter,et al.  Optical properties and mineralogical composition of different Saharan mineral dust samples: a laboratory study , 2006 .

[45]  John J. Drake.  The Effects of Surface Dust on Snowmelt Rates , 1981 .

[46]  C Christodoulatos,et al.  A review of tungsten: from environmental obscurity to scrutiny. , 2006, Journal of hazardous materials.

[47]  Philip W. Mote,et al.  The Response of Northern Hemisphere Snow Cover to a Changing Climate , 2008 .

[48]  Laurent Arnaud,et al.  Development and calibration of an automatic spectral albedometer to estimate near-surface snow SSA time series , 2016 .

[49]  R. Gautam,et al.  Satellite observations of desert dust‐induced Himalayan snow darkening , 2013 .

[50]  A. Avila,et al.  The chemical composition of dust transported in red rains—its contribution to the biogeochemical cycle of a holm oak forest in Catalonia (Spain) , 1998 .

[51]  A. Laskin,et al.  Heterogeneous chemistry of individual mineral dust particles from different dust source regions: the importance of particle mineralogy , 2004 .

[52]  J. Peñuelas,et al.  Potassium: a neglected nutrient in global change. , 2015 .

[53]  M. Sillanpää,et al.  Carbonaceous matter deposition in the high glacial regions of the Tibetan Plateau , 2016 .

[54]  M. Andreae,et al.  Soluble iron nutrients in Saharan dust over the central Amazon rainforest , 2017 .

[55]  John Kochendorfer,et al.  Analysis of single-Alter-shielded and unshielded measurements of mixed and solid precipitation from WMO-SPICE , 2017 .

[56]  M. Rossini,et al.  Using digital camera images to analyse snowmelt and phenology of a subalpine grassland , 2014 .

[57]  Harald Flentje,et al.  Identification and monitoring of Saharan dust: An inventory representative for south Germany since 1997 , 2015 .

[58]  M. Migliavacca,et al.  Phenopix: A R package for image-based vegetation phenology , 2016 .

[59]  S. Singh,et al.  Seasonal radiogenic isotopic variability of the African dust outflow to the tropical Atlantic Ocean and across to the Caribbean , 2018 .

[60]  N. Mahowald,et al.  Improved dust representation in the Community Atmosphere Model , 2012 .

[61]  John C. Pearl,et al.  Thermal Emission Spectrometer Observations of Martian Planet-Encircling Dust Storm 2001A , 2001 .

[62]  Greenland glacier calving rates from Extreme Ice Survey (EIS) time lapse photogrammetry , 2010 .

[63]  M. Oliva,et al.  Photosynthesis and oxidative stress in the restinga plant species Eugenia uniflora L. exposed to simulated acid rain and iron ore dust deposition: potential use in environmental risk assessment. , 2009, The Science of the total environment.

[64]  M. Chin,et al.  The fertilizing role of African dust in the Amazon rainforest: A first multiyear assessment based on data from Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations , 2015 .

[65]  M. Loso,et al.  The role of microbes in snowmelt and radiative forcing on an Alaskan icefield , 2017 .

[66]  P. Nabat,et al.  A multilayer physically based snowpack model simulating direct and indirect radiative impacts of light-absorbing impurities in snow , 2017 .

[67]  E. Martin,et al.  The detailed snowpack scheme Crocus and its implementation in SURFEX v 7 . 2 , 2011 .

[68]  Thomas H. Painter,et al.  Imaging spectroscopy of albedo and radiative forcing by light‐absorbing impurities in mountain snow , 2013 .

[69]  N. Middleton,et al.  Saharan dust storms: nature and consequences , 2001 .

[70]  R. Rudnick,et al.  Composition of the Continental Crust , 2014 .

[71]  Micol Rossini,et al.  A novel hyperspectral system for high resolution imaging of ice cores: Application to light-absorbing impurities and ice structure , 2018, Cold Regions Science and Technology.

[72]  Montserrat Filella.  Tantalum in the environment , 2017 .

[73]  D. Wagenbach,et al.  The Mineral Dust Record in a High Altitude Alpine Glacier (Colle Gnifetti, Swiss Alps) , 1989 .

[74]  Rolf Weingartner,et al.  Toward mountains without permanent snow and ice: MOUNTAINS WITHOUT PERMANENT SNOW AND ICE , 2017 .

[75]  C. Alewell,et al.  Calcium Induces Long-Term Legacy Effects in a Subalpine Ecosystem , 2012, PloS one.

[76]  A. Kasper-Giebl,et al.  Evaluation of WRF-Chem Model Forecasts of a Prolonged Saharan Dust Episode over the Eastern Alps , 2019, Aerosol and Air Quality Research.

[77]  R. Miller,et al.  Atmospheric dust modeling from meso to global scales with the online NMMB/BSC-Dust model – Part 1: Model description, annual simulations and evaluation , 2011 .

[78]  F. Cao,et al.  The impact of Saharan dust and black carbon on albedo and long-term mass balance of an Alpine glacier , 2015 .

[79]  N. Mahowald,et al.  Global Iron Connections Between Desert Dust, Ocean Biogeochemistry, and Climate , 2005, Science.

[80]  A. Gaudichet,et al.  Saharan dust deposition over Mont Blanc (French Alps) during the last 30 years , 1991 .

[81]  E. Martin,et al.  The detailed snowpack scheme Crocus and its implementation in SURFEX v7.2 , 2012 .

[82]  Laurent Arnaud,et al.  Influence of grain shape on light penetration in snow , 2013 .

[83]  Eleonora P Zege,et al.  Scattering optics of snow. , 2004, Applied optics.

[84]  U. R S R U T H,et al.  Proxies and Measurement Techniques for Mineral Dust in Antarctic Ice Cores , 2008 .

[85]  C. Telloli,et al.  Saharan dust particles in snow samples of Alps and Apennines during an exceptional event of transboundary air pollution , 2017, Environmental Monitoring and Assessment.

[86]  A. Borio di Tigliole,et al.  Benchmark evaluation of reactor critical parameters and neutron fluxes distributions at zero power for the TRIGA Mark II reactor of the University of Pavia using the Monte Carlo code MCNP , 2010 .

[87]  Thomas H. Painter,et al.  End of the Little Ice Age in the Alps forced by industrial black carbon , 2013, Proceedings of the National Academy of Sciences.

[88]  N. Mahowald,et al.  The size distribution of desert dust aerosols and its impact on the Earth system , 2014 .

[89]  W. McDonough,et al.  Chemical and isotopic systematics of oceanic basalts: implications for mantle composition and processes , 1989, Geological Society, London, Special Publications.

[90]  B. D. Mauro,et al.  Mineral dust impact on snow radiative properties in the European Alps combining ground, UAV, and satellite observations , 2015 .

[91]  H. A. Jones.  EFFECT OF DUST ON THE MELTING OF SNOW , 1913 .

[92]  E. Martin,et al.  An Energy and Mass Model of Snow Cover Suitable for Operational Avalanche Forecasting , 1989, Journal of Glaciology.

[93]  J. Penner,et al.  Enhanced Solar Energy Absorption by Internally-Mixed Black Carbon in Snow Grains , 2012 .

[94]  Gregory S. Okin,et al.  Impact of desert dust on the biogeochemistry of phosphorus in terrestrial ecosystems , 2004 .

[95]  T. Mote,et al.  Polar Jet Associated Circulation Triggered a Saharan Cyclone and Derived the Poleward Transport of the African Dust Generated by the Cyclone , 2018, Journal of Geophysical Research: Atmospheres.

[96]  J. Overpeck,et al.  Increasing Eolian Dust Deposition in the Western United States Linked to Human Activity , 2008 .

[97]  Chris Landry,et al.  Biological consequences of earlier snowmelt from desert dust deposition in alpine landscapes , 2009, Proceedings of the National Academy of Sciences.

[98]  Thomas H. Painter,et al.  Variation in Rising Limb of Colorado River Snowmelt Runoff Hydrograph Controlled by Dust Radiative Forcing in Snow , 2017 .

[99]  Ulrich Bundke,et al.  Chemical composition and complex refractive index of Saharan Mineral Dust at Izaña, Tenerife (Spain) derived by electron microscopy , 2007 .

[100]  Birger Ulf Hansen,et al.  Automatic snow cover monitoring at high temporal and spatial resolution, using images taken by a standard digital camera , 2002 .

[101]  X. Querol,et al.  Geochemical variations in aeolian mineral particles from the Sahara-Sahel Dust Corridor. , 2006, Chemosphere.

[102]  J. Corripio.  Snow surface albedo estimation using terrestrial photography , 2004 .

[103]  C. Schär,et al.  Future snowfall in the Alps: projections based on the EURO-CORDEX regional climate models , 2018 .

[104]  Dongmei Xu,et al.  Ecosystem functions including soil organic carbon, total nitrogen and available potassium are crucial for vegetation recovery , 2018, Scientific Reports.

[105]  Nicolas Eckert,et al.  Multi-component ensembles of future meteorological and natural snow conditions for 1500 m altitude in the Chartreuse mountain range, Northern French Alps , 2018 .

[106]  A. Stohl,et al.  Impact of dust deposition on the albedo of Vatnajökull ice cap, Iceland , 2016 .

[107]  David A. Robinson,et al.  Northern Hemisphere spring snow cover variability and change over 1922–2010 including an assessment of uncertainty , 2010 .

[108]  Jeremy M. Cohen,et al.  A global synthesis of animal phenological responses to climate change , 2018, Nature Climate Change.

[109]  Peter E. Thornton,et al.  Carbon-nitrogen interactions regulate climate-carbon cycle feedbacks: results from an atmosphere-ocean general circulation model , 2009 .

[110]  T. Painter,et al.  Impact of disturbed desert soils on duration of mountain snow cover , 2007 .

[111]  P. Nabat,et al.  In situ continuous visible and near-infrared spectroscopy of an alpine snowpack , 2016 .

[112]  Günter Blöschl,et al.  Potential of time‐lapse photography of snow for hydrological purposes at the small catchment scale , 2012 .

[113]  B. D. Mauro,et al.  Impact of impurities and cryoconite on the optical properties of the Morteratsch Glacier (Swiss Alps) , 2017 .

[114]  T. Painter,et al.  Radiative forcing by light absorbing impurities in snow from MODIS surface reflectance data , 2012 .

[115]  Andrew A. Lacis,et al.  Modeling of particle size distribution and its influence on the radiative properties of mineral dust aerosol , 1996 .

[116]  Tommaso Julitta,et al.  Phenology and carbon dioxide source/sink strength of a subalpine grassland in response to an exceptionally short snow season , 2013 .

[117]  J. Clague,et al.  Toward mountains without permanent snow and ice , 2017 .

[118]  S. Warren,et al.  A Model for the Spectral Albedo of Snow. II: Snow Containing Atmospheric Aerosols , 1980 .

[119]  P. Formenti,et al.  Dominance of goethite over hematite in iron oxides of mineral dust from Western Africa: Quantitative partitioning by X‐ray absorption spectroscopy , 2014 .

[120]  D. Hollinger,et al.  Use of digital webcam images to track spring green-up in a deciduous broadleaf forest , 2007, Oecologia.

[121]  J. Randerson,et al.  Carbon-nitrogen interactions regulate climate-carbon cycle feedbacks: results from an atmosphere-ocean general circulation model , 2009 .

[122]  N. Mahowald,et al.  Shape and size constraints on dust optical properties from the Dome C ice core, Antarctica , 2016, Scientific Reports.

[123]  Martin Ebert,et al.  Recent progress in understanding physical and chemical properties of African and Asian mineral dust , 2011 .

[124]  Thomas H. Painter,et al.  Dust radiative forcing in snow of the Upper Colorado River Basin: 1. A 6 year record of energy balance, radiation, and dust concentrations , 2012 .

[125]  Y. Arnaud,et al.  Monitoring spatial and temporal variations of surface albedo on Saint Sorlin Glacier (French Alps) using terrestrial photography , 2011 .

[126]  T. Painter,et al.  Radiative forcing by light-absorbing particles in snow , 2018, Nature Climate Change.

[127]  G. Baccolo,et al.  A new method based on low background instrumental neutron activation analysis for major, trace and ultra-trace element determination in atmospheric mineral dust from polar ice cores. , 2016, Analytica chimica acta.

[128]  C. Donati,et al.  Legal immigrants: invasion of alien microbial communities during winter occurring desert dust storms , 2017, Microbiome.

[129]  Michael Lehning,et al.  The European mountain cryosphere: a review of its current state, trends, and future challenges , 2018 .

[130]  C. Hueglin,et al.  Saharan dust events at the Jungfraujoch: detection by wavelength dependence of the single scattering albedo and first climatology analysis , 2004 .

[131]  Modelling hydrologic impacts of light absorbing aerosol deposition on snow at the catchment scale , 2016 .

[132]  John F. Burkhart,et al.  Modelling hydrologic impacts of light absorbing aerosol deposition on snow at the catchment scale , 2016 .

[133]  J. Peñuelas,et al.  Increasing frequency of Saharan rains over northeastern Spain and its ecological consequences , 1999 .