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Sample records for aeolian dust records

  1. A 37,000-year environmental magnetic record of aeolian dust deposition from Burial Lake, Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Dorfman, J. M.; Stoner, J. S.; Finkenbinder, M. S.; Abbott, M. B.; Xuan, C.; St-Onge, G.

    2015-11-01

    Environmental magnetism and radiocarbon dating of Burial Lake sediments constrain the timing and magnitude of regional aeolian deposition for the Noatak region of western Arctic Alaska for the last ˜37,000 years. Burial Lake (68.43°N, 159.17°W, 21.5 m water depth) is optimally located to monitor regional dust deposition because it is perched above local drainage and isolated from glacial processes. Cores collected in the summer of 2010 were studied through the application of magnetizations and progressive alternating field (AF) demagnetization of u-channel samples, with additional data provided by computed tomography (CT) derived density, hysteresis measurements, isothermal remanent magnetization (IRM) acquisition experiments, organic carbon content, biogenic silica, physical grain size, radiocarbon dating of wood, seeds, and plant macrofossils, point source magnetic susceptibility, and X-ray fluorescence (XRF). With similar magnetic properties to regional Alaskan loess deposits, low coercivity, highly magnetic material deposited during the late-Pleistocene contrasts with a high coercivity, weakly magnetic component found throughout the record, consistent with locally-derived detritus. The relative proportion of low coercivity to high coercivity magnetic material, defined by the S-Ratios, is used to reconstruct the regional input of dust to the basin over time. A four-fold decrease in the low coercivity component through the deglacial transition is interpreted to reflect diminished dust input to the region. Comparisons with potential sources of dust show that the timing of deposition in Burial Lake is largely consistent with general aridity, lack of vegetative cover, and increased windiness, rather than glacial advances or retreats. The influence from subaerial exposure of continental shelves cannot be ruled out as a significant far-field source of dust to interior Alaska during the Last Glacial Maximum (LGM), but is unlikely to have been the sole source, or to

  2. Aeolian dust as a transport hazard

    NASA Astrophysics Data System (ADS)

    Baddock, M. C.; Strong, C. L.; Murray, P. S.; McTainsh, G. H.

    2013-06-01

    The effects of blowing dust on transport operations are often mentioned as one of the significant impacts of aeolian processes on human welfare. However, few studies have been presented to demonstrate this impact. This research examined official air traffic incident reports in Australia for inclusively 1969-2010 to characterise the hazard of blowing dust to aviation in the country, the first such study of its kind. For the 42 year record, 61 incidents were identified (mean 1.4 per annum), with the large majority occurring in the first half of the 1970s. Only 20% of incidents occurred from 1984 onwards. Australian dust activity has not decreased over time, and the reduction in incidents is partly explained by improvements in aviation technology. The centralisation of Air Traffic Control operations to major coastal cities may however have reduced pilot reporting of dust-induced aviation incidents. By type of dust activity, dust storms were associated with nearly half of the reported incidents and dust hazes produced around a quarter. Only 5% of incidents resulted in any physical damage to aircraft and only one case involving personal injury was reported. The majority of the adverse effects on aviation due to dust (nearly 60% of reported incidents) were related to difficulties for navigation and completion of scheduled journey. Since aircraft damage and bodily harm were rare, the impact of dust in Australia is mostly that of inconvenience and associated raised economic costs. From 1990, the temporal pattern of incidents does not show any significant increase despite several intensely dusty years associated with recent droughts. This suggests that Australian aviation safety may be relatively resistant to the adverse effects of atmospheric dust as a hazard.

  3. Characteristics of aeolian dust across northwest Australia

    NASA Astrophysics Data System (ADS)

    Karlson, L. R.; Greene, R. S. B.; Scott, K. M.; Stelcer, E.; O'Loingsigh, T.

    2014-03-01

    South easterly trade winds have long been thought to transport aeolian dust across northwest Australia, but very little is known about the chemical and particle size characteristics of this material. From July 2008 to May 2009, 36 aeolian dust samples were collected monthly at four sites across Australia's northwest. The results of ion beam analysis indicate that the samples consisted of four major elemental groups, one of which appeared to be transported across the sites during months in winter and summer. This group (characterised by higher ratios of Fe, Ti and Mn/Si than the Earth's Crustal Average) also showed a decrease in particle sizes towards the west. This suggests that the dust may have had a central Australian source, while other groups richer in Si appear to have been locally derived. These results support previous models of seasonal dust transport, and may have relevance in regional climate modelling, the transport of nutrients into the Indian Ocean, mineral exploration and studies of respiratory health.

  4. The nature and formation of aeolian mineral dust material

    NASA Astrophysics Data System (ADS)

    Smalley, Ian; O'hara-Dhand, Ken; McLaren, Sue

    2013-04-01

    Aeolian dust affects climate and records past climates. It has become a much studied material but there has been a certain lack of emphasis on the actual nature of the dust, and an even greater neglect of actual production mechanisms for dust particles. Huge amounts of dust may be raised from the Bodele depression and other parts of North Africa, and much of it may be carried across the North Atlantic to aid in soil formation in Brazil. But what does it consist of? We know that much of the Bodele dust is diatoms from old Lake Chad, but what of the lithological inorganic mineral content? A very crude division of aeolian dust into large dust(say around 20-50um) and small dust (2-5um)has been proposed. Much of the study of loess has been confused by the failure to make this distinction, and similar problems may arise in the study of the finer fractions of aeolian dust. Much aeolian material is clay-mineral based- formed from clay mineral aggregates(CMA), from lake bottom sediments. This can form large dust particles, as in parna in Australia, but also contributes largely to small long travel aerosolic dust. Another major contributor is the quartz fragment. The large dust for classic loess deposits is mostly quartz silt- and there is considerable discussion about the controls that affect quartz silt. There are some interesting modalities in the world of quartz particle sedimentology which need to be examined. Quartz sand (say 200-500um) is the key initiating material and the formation processes for quartz sand have a down-the-line effect on the formation of smaller particles. The central observation is the action of two processes- a eutectic-like reaction in the proto-rock granite which defines the essential nature of sand particles, and the high-low displacive crystallographic transformation which introduces tensile stresses into the quartz particle systems. The limited range of eutectic particle size means a limited range of tensile stresses. A neat combination of

  5. The role of aeolian dust in ecosystems

    NASA Astrophysics Data System (ADS)

    McTainsh, Grant; Strong, Craig

    2007-09-01

    The recent upsurge in research attention to aeolian dust has shown that dust transport systems operate on very large spatial and temporal scales, and involve much larger quantities of sediment than was previously realized. An inevitable consequence of this is that researchers from a range of neighbouring disciplines, including ecology, are beginning to realize that this new knowledge has important implications for their study areas. In the present paper, we examine the ecological implications (real and potential) of this expanding knowledge of dust transport systems, with a particular emphasis upon the Australian dust transport system. We track these ecological effects from source to sink. At source, wind erosion-soil-vegetation relationships are often dominated by temporal changes in rainfall. Nine years of measurements in the Channel Country of the Lake Eyre Basin, Australia show that vegetation and soils in dune fields can recover from drought, whereas on inter-fluve grasslands uni-directional and negative successional vegetation changes can result from wind erosion during drought. On floodplains, both wind erosion and vegetation responses are complicated by flood frequency. Up to 1999 flooding of saline claypans did not increase vegetation but did increase wind erosion through the supply of alluvial fines. However, after three floods within as many months vegetation became established and wind erosion rates were dramatically reduced. Wind erosion research attention is now gradually turning from the physical to the organic content of eroded dusts. In Australia organic matter content can reach 65% by mass, but this cannot be explained by removal of soil organic matter alone. Biological soil crusts not only stabilize soils against wind erosion but contribute to some of the organic dusts. The role of dust as a vector for pathogens is an area which deserves greater research attention in the future. Downwind from source, we show that dust contributions to soils are

  6. Size-differentiated chemical characteristics of Asian paleo dust: records from aeolian deposition on Chinese Loess Plateau.

    PubMed

    Wu, Feng; Chow, Judith C; An, Zhisheng; Watson, John G; Cao, Junji

    2011-02-01

    The Chinese Loess Plateau (CLP) receives and potentially contributes to Asian dust storms that affect particulate matter (PM) concentrations, visibility, and climate. Loess on the CLP has experienced little weathering effect and is regarded as an ideal record to represent geochemical characteristics of Asian paleo dust. Samples were taken from 2-, 9-, and 15-m depths (representing deposition periods from approximately 12,000 to approximately 200,000 yr ago) in the Xi Feng loess profile on the CLP. The samples were resuspended and then sampled through total suspended particulates (TSP), PM10, PM2.5, and PM1 (PM with aerodynamic diameters < approximately 30, 10, 2.5, and 1 microm, respectively) inlets onto filters for mass, elemental, ionic, and carbon analyses using a Desert Research Institute resuspension chamber. The elements Si, Ca, Al, Fe, K, Mg, water-soluble Ca (Ca2+), organic carbon, and carbonate carbon are the major constituents (> 1%) in loess among the four PM fractions (i.e., TSP, PM10, PM2.5, and PM1). Much of Ca is water soluble and corresponds with measures of carbonate, indicating that most of the calcium is in the form of calcium carbonate rather than other calcium minerals. Most of the K is insoluble, indicating that loess can be separated from biomass burning contributions when K+ is measured. The loess has elemental abundances similar to those of the upper continental crust (UCC) for Mg, Fe, Ti, Mn, V, Cr, and Ni, but substantially different ratios for other elements such as Ca, Co, Cu, As, and Pb. These suggest that the use of UCC as a reference to represent pure or paleo Asian dust needs to be further evaluated. The aerosol samples from the source regions have similar ratios to loess for crustal elements, but substantially different ratios for species from anthropogenic sources (e.g., K, P, V, Cr, Cu, Zn, Ni, and Pb), indicating that the aerosol samples from the geological-source-dominated environment are not a "pure" soil product as compared

  7. Aeolian dust in Colorado Plateau soils: nutrient inputs and recent change in source.

    PubMed

    Reynolds, R; Belnap, J; Reheis, M; Lamothe, P; Luiszer, F

    2001-06-19

    Aeolian dust (windblown silt and clay) is an important component in arid-land ecosystems because it may contribute to soil formation and furnish essential nutrients. Few geologic surfaces, however, have been characterized with respect to dust-accumulation history and resultant nutrient enrichment. We have developed a combination of methods to identify the presence of aeolian dust in arid regions and to evaluate the roles of this dust in ecosystem processes. Unconsolidated sandy sediment on isolated surfaces in the Canyonlands region of the Colorado Plateau differs greatly in mineralogical and chemical composition from associated bedrock, mainly aeolian sandstone. Detrital magnetite in the surficial deposits produces moderately high values of magnetic susceptibility, but magnetite is absent in nearby bedrock. A component of the surficial deposits must be aeolian to account for the abundance of magnetite, which formed originally in far-distant igneous rocks. Particle-size analysis suggests that the aeolian dust component is typically as much as 20-30%. Dust inputs have enriched the sediments in many elements, including P, Mg, Na, K, and Mo, as well as Ca, at sites where bedrock lacks calcite cement. Soil-surface biologic crusts are effective dust traps that apparently record a change in dust sources over the past several decades. Some of the recently fallen dust may result from human disturbance of land surfaces that are far from the Canyonlands, such as the Mojave Desert. Some land-use practices in the study area have the potential to deplete soil fertility by means of wind-erosion removal of aeolian silt.

  8. Aeolian dust in Colorado Plateau soils: Nutrient inputs and recent change in source

    USGS Publications Warehouse

    Reynolds, R.; Belnap, Jayne; Lamothe, Paul; Luiszer, Fred

    2001-01-01

    Aeolian dust (windblown silt and clay) is an important component in arid-land ecosystems because it may contribute to soil formation and furnish essential nutrients. Few geologic surfaces, however, have been characterized with respect to dust-accumulation history and resultant nutrient enrichment. We have developed a combination of methods to identify the presence of aeolian dust in arid regions and to evaluate the roles of this dust in ecosystem processes. Unconsolidated sandy sediment on isolated surfaces in the Canyonlands region of the Colorado Plateau differs greatly in mineralogical and chemical composition from associated bedrock, mainly aeolian sandstone. Detrital magnetite in the surficial deposits produces moderately high values of magnetic susceptibility, but magnetite is absent in nearby bedrock. A component of the surficial deposits must be aeolian to account for the abundance of magnetite, which formed originally in far-distant igneous rocks. Particle-size analysis suggests that the aeolian dust component is typically as much as 20a??30%. Dust inputs have enriched the sediments in many elements, including P, Mg, Na, K, and Mo, as well as Ca, at sites where bedrock lacks calcite cement. Soil-surface biologic crusts are effective dust traps that apparently record a change in dust sources over the past several decades. Some of the recently fallen dust may result from human disturbance of land surfaces that are far from the Canyonlands, such as the Mojave Desert. Some land-use practices in the study area have the potential to deplete soil fertility by means of wind-erosion removal of aeolian silt.

  9. Optical Properties of Aeolian Dusts Common to West Texas

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Both recent models and historical events such as the Dust Bowl and volcanic eruptions have illustrated aerosols can play a significant role in climate change through direct and indirect optical effects. Soil dust aerosols generated by Aeolian processes represent a significant fraction of the total ...

  10. Mechanics of aeolian processes: Soil erosion and dust production

    NASA Technical Reports Server (NTRS)

    Mehrabadi, M. M.

    1989-01-01

    Aeolian (wind) processes occur as a result of atmosphere/land-surface system interactions. A thorough understanding of these processes and their physical/mechanical characterization on a global scale is essential to monitoring global change and, hence, is imperative to the fundamental goal of the Earth observing system (Eos) program. Soil erosion and dust production by wind are of consequence mainly in arid and semi arid regions which cover 36 percent of the Earth's land surface. Some recent models of dust production due to wind erosion of agricultural soils and the mechanics of wind erosion in deserts are reviewed and the difficulties of modeling the aeolian transport are discussed.

  11. Optical properties of Aeolian dusts common to West Texas

    NASA Astrophysics Data System (ADS)

    Ma, Lulu; Zobeck, Ted M.; Hsieh, Daniel H.; Holder, Dean; Morgan, Cristine L. S.; Thompson, Jonathan E.

    2011-11-01

    Both recent models and historical events such as the Dust Bowl and volcanic eruptions have illustrated aerosols can play a significant role in climate change through direct and indirect optical effects. Soil dust aerosols generated by Aeolian processes represent a significant fraction of the total mass burden of atmospheric particles. Central to a better understanding of the climate effects of dust aerosols is knowledge of their optical properties. This research study utilized a dust generator and several instruments to determine certain optical properties of Aeolian dust mimics created by the Amarillo and Pullman soil types native to the panhandle of Texas, USA. Values for the mass-extinction coefficient ranged between 1.74 and 2.97 m 2 g -1 at 522 nm depending on how mass concentration was determined. Single-scatter albedo (SSA) for both soil types ranged from 0.947 to 0.980 at visible wavelengths with SSA increasing at longer wavelengths. Angstrom absorption exponents were measured as 1.73 for Pullman and 2.17 for Amarillo soil. Observed Angstrom extinction exponents were 0.110 and 0.168 for the Pullman and Amarillo soil types. The optical properties reported may be of use for optical based estimates of soil erosion and aid in understanding how regional soil dusts may alter radiative transport presently and during historical events such as the Dust Bowl era.

  12. An introduction to aeolian dust dynamics recorded in the Stari Slankamen loess sequence (Vojvodina, Serbia) - Implications for past atmospheric circulation patterns of Eurasia

    NASA Astrophysics Data System (ADS)

    Stender, J.; Lukic, T.; Milojkovic, N.; Markovic, S.; Machalett, B.

    2008-12-01

    Loess sequences provide a direct proxy for the sedimentation dynamics of atmospheric dust, giving important information about the origin of the mineral aerosols and past palaeoclimatic conditions at that time of deposition. The conditions that determine the areas of origin, the transport and distribution of the aeolian material, are being accentuated by the dynamic process structures at the interface of the land surface and the atmosphere. Eventually this may allow the reconstruction of past atmospheric circulation patterns through high resolution loess investigations at different loess sites. The Stari Slankamen loess-palaeosol sequence is situated in the eastern part of the Srem Loess Plateau on the right bank of the Danube near by the river mouth of the Tisza into the Danube. Eight loess layers were distinguished, intercalated by nine pedocomplexes. The sequence under study has a total thickness of approximately 45 m. According to previous investigations the Stari Slankamen loess site is considered as one of the most important sections in the Pannonian basin. In this paper we present the first results of highly resolved grain size studies of the loess section Stari Slankamen. During fieldwork samples for grain size were taken at 2 cm intervals from the loess and the palaeosols, respectively. Particle size measurements of all samples were processed on a Beckman Coulter LS 13320 PIDS laser sizer with auto-prep station to provide a dynamic range that spans from 0.04 to 2000 µm and ensure accuracy and reproducibility. The granulometric results show distinct variations within the silt fraction and allow a clear distinction between cold and warm cycles. They show an important coherence between the type of dust sedimentation and the prevailing climate and offer insight into past atmospheric circulations of SE-Europe. Our results fundamentally contribute to a better understanding of interhemispheric teleconnections between Eurasian climate systems.

  13. Sensitivity simulations with direct shortwave radiative forcing by aeolian dust during glacial cycles

    NASA Astrophysics Data System (ADS)

    Bauer, E.; Ganopolski, A.

    2014-07-01

    Possible feedback effects between aeolian dust, climate and ice sheets are studied for the first time with an Earth system model of intermediate complexity over the late Pleistocene period. Correlations between climate and dust deposition records suggest that aeolian dust potentially plays an important role for the evolution of glacial cycles. Here climatic effects from the dust direct radiative forcing (DRF) caused by absorption and scattering of solar radiation are investigated. Key elements controlling the dust DRF are the atmospheric dust distribution and the absorption-scattering efficiency of dust aerosols. Effective physical parameters in the description of these elements are varied within uncertainty ranges known from available data and detailed model studies. Although the parameters can be reasonably constrained, the simulated dust DRF spans a~wide uncertainty range related to the strong nonlinearity of the Earth system. In our simulations, the dust DRF is highly localized. Medium-range parameters result in negative DRF of several watts per square metre in regions close to major dust sources and negligible values elsewhere. In the case of high absorption efficiency, the local dust DRF can reach positive values and the global mean DRF can be insignificantly small. In the case of low absorption efficiency, the dust DRF can produce a significant global cooling in glacial periods, which leads to a doubling of the maximum glacial ice volume relative to the case with small dust DRF. DRF-induced temperature and precipitation changes can either be attenuated or amplified through a feedback loop involving the dust cycle. The sensitivity experiments suggest that depending on dust optical parameters, dust DRF has the potential to either damp or reinforce glacial-interglacial climate changes.

  14. Wind tunnel and field calibration of six aeolian dust samplers

    NASA Astrophysics Data System (ADS)

    Goossens, Dirk; Offer, Zvi Y.

    The efficiency of six aeolian dust samplers was tested via wind tunnel experiments and field measurements. In the wind tunnel, four samplers designed to measure the horizontal dust flux and one sampler designed to measure the vertical dust flux (in the downward direction, i.e., deposition) were calibrated against an isokinetic reference sampler. The horizontal dust flux samplers were: the big spring number eight sampler (BSNE), the modified Wilson and Cooke sampler (MWAC), the suspended sediment trap (SUSTRA), and the wedge dust flux gauge (WDFG). Vertical deposition flux was measured using a marble dust collector (MDCO). A modified Sartorius SM 16711 dust sampler with adjustable flow rate (SARTORIUS) was used as isokinetic reference sampler. In the field experiments, the WDFG was replaced by a Sierra ultra high volume dust sampler (SIERRA). Wind tunnel calibrations were carried out at five wind velocities ranging from 1 to 5 m s -1. Field calibrations were conducted during seven periods of two weeks each. The most efficient samplers are the MWAC and the SIERRA, followed by the BSNE and the SUSTRA. The WDFG is more effective than the BSNE at velocities below 3 m s -1, but its efficiency drops quickly at higher wind speeds. The most recommendable sampler for field measurements is the BSNE, because its efficiency varies only very slightly with wind speed. In the absence of horizontal flux samplers, the MDCO collector can be used as an alternative to assess horizontal dust flux and airborne dust concentration provided the appropriate calibrations are made.

  15. Identifying sources of aeolian mineral dust: Present and past

    USGS Publications Warehouse

    Muhs, Daniel R; Prospero, Joseph M; Baddock, Matthew C; Gill, Thomas E

    2014-01-01

    Aeolian mineral dust is an important component of the Earth’s environmental systems, playing roles in the planetary radiation balance, as a source of fertilizer for biota in both terrestrial and marine realms and as an archive for understanding atmospheric circulation and paleoclimate in the geologic past. Crucial to understanding all of these roles of dust is the identification of dust sources. Here we review the methods used to identify dust sources active at present and in the past. Contemporary dust sources, produced by both glaciogenic and non-glaciogenic processes, can be readily identified by the use of Earth-orbiting satellites. These data show that present dust sources are concentrated in a global dust belt that encompasses large topographic basins in low-latitude arid and semiarid regions. Geomorphic studies indicate that specific point sources for dust in this zone include dry or ephemeral lakes, intermittent stream courses, dune fields, and some bedrock surfaces. Back-trajectory analyses are also used to identify dust sources, through modeling of wind fields and the movement of air parcels over periods of several days. Identification of dust sources from the past requires novel approaches that are part of the geologic toolbox of provenance studies. Identification of most dust sources of the past requires the use of physical, mineralogical, geochemical, and isotopic analyses of dust deposits. Physical properties include systematic spatial changes in dust deposit thickness and particle size away from a source. Mineralogy and geochemistry can pinpoint dust sources by clay mineral ratios and Sc-Th-La abundances, respectively. The most commonly used isotopic methods utilize isotopes of Nd, Sr, and Pb and have been applied extensively in dust archives of deep-sea cores, ice cores, and loess. All these methods have shown that dust sources have changed over time, with far more abundant dust supplies existing during glacial periods. Greater dust supplies in

  16. Granulometric profiling of aeolian dust deposits by automated image analysis

    NASA Astrophysics Data System (ADS)

    Varga, György; Újvári, Gábor; Kovács, János; Jakab, Gergely; Kiss, Klaudia; Szalai, Zoltán

    2016-04-01

    Determination of granulometric parameters is of growing interest in the Earth sciences. Particle size data of sedimentary deposits provide insights into the physicochemical environment of transport, accumulation and post-depositional alterations of sedimentary particles, and are important proxies applied in paleoclimatic reconstructions. It is especially true for aeolian dust deposits with a fairly narrow grain size range as a consequence of the extremely selective nature of wind sediment transport. Therefore, various aspects of aeolian sedimentation (wind strength, distance to source(s), possible secondary source regions and modes of sedimentation and transport) can be reconstructed only from precise grain size data. As terrestrial wind-blown deposits are among the most important archives of past environmental changes, proper explanation of the proxy data is a mandatory issue. Automated imaging provides a unique technique to gather direct information on granulometric characteristics of sedimentary particles. Granulometric data obtained from automatic image analysis of Malvern Morphologi G3-ID is a rarely applied new technique for particle size and shape analyses in sedimentary geology. Size and shape data of several hundred thousand (or even million) individual particles were automatically recorded in this study from 15 loess and paleosoil samples from the captured high-resolution images. Several size (e.g. circle-equivalent diameter, major axis, length, width, area) and shape parameters (e.g. elongation, circularity, convexity) were calculated by the instrument software. At the same time, the mean light intensity after transmission through each particle is automatically collected by the system as a proxy of optical properties of the material. Intensity values are dependent on chemical composition and/or thickness of the particles. The results of the automated imaging were compared to particle size data determined by three different laser diffraction instruments

  17. Aeolian removal of dust from photovoltaic surfaces on Mars

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Perez-Davis, Marla E.; Marabito, Mark

    1990-01-01

    It is well documented that Mars is totally engulfed in huge dust storms nearly each Martian year. Dust elevated in these global dust storms, or in any of the numerous local dust storms could settle on photovoltaic surfaces and seriously hamper photovoltaic power system performance. Using a recently developed technique to uniformly dust simulated photovoltaic surfaces, samples were subjected to Martian-like winds in an attempt to determine whether natural aeolian processes on Mars would sweep off the settled dust. The effects of wind velocity, angle of attack, height off the Martian surface, and surface coating material were investigated. Principles which can help to guide the design of photovoltaic arrays bound for the Martian surface were uncovered. Most importantly, arrays mounted with an angle of attack approaching 45 deg show the most efficient clearing. Although the angular dependence is not sharp, horizontally mounted arrays required significantly higher wind velocities to clear off the dust. From the perspective of dust-clearing it appears that the arrays may be erected quite near the ground, but previous studies have suggested that saltation effects can be expected to cause such arrays to be covered by sand if they are set up less than about a meter from the ground. Providing that the surface chemistry of Martian dusts is comparable to our test dust, the materials used for protective coating may be optimized for other considerations such as transparency, and chemical or abrasion resistance. The static threshold velocity is low enough that there are regions on Mars which experience winds strong enough to clear off a photovoltaic array if it is properly oriented. Turbulence fences proved to be an ineffective strategy to keep dust cleared from the photovoltaic surfaces.

  18. Variation in aeolian environments recorded by the particle size distribution of lacustrine sediments in Ebinur Lake, northwest China.

    PubMed

    Ma, Long; Wu, Jinglu; Abuduwaili, Jilili

    2016-01-01

    Particle size analysis of lacustrine core sediments and atmospheric natural dust were conducted in the drainage area of Ebinur Lake in arid northwest China. Using a combination of (137)Cs and (210)Pb dating, a continuous record of aeolian transportation to the lake sediments and related factors over about the past 150 years was analyzed. Factor analysis revealed the particle-size distributions of riverine and aeolian sediments composed of the terrigenous materials of the lake deposits. Compared with the grain-size distributions of natural dust samples, the results showed that the coarser particle size fraction of lake sediments was mainly derived from the sediments that had experienced aeolian transport to the drainage surface, and the finer sediments came from hydraulic inputs. Then, the method of variations in particle-size standard deviation was used to extract the grain size intervals with the highest variability along a sedimentary sequence. The coarser grain-size populations dominated the variation patterns of the sedimentary sequence. During the last 150 years, strong intensity aeolian transportation occurred during three periods, 1915-1935, 1965-1975 and since the beginning of the 2000s. The climate was dry around 1910s-1930s in this region associated with the appropriate dynamic condition, which provided the enhanced source materials and wind power for the aeolian dust transport. Since 1950s, the climate controlled the foundation of aeolian dust transport, and the aeolian dust transport won't be increased under the humid climate. PMID:27217996

  19. Variation in aeolian environments recorded by the particle size distribution of lacustrine sediments in Ebinur Lake, northwest China.

    PubMed

    Ma, Long; Wu, Jinglu; Abuduwaili, Jilili

    2016-01-01

    Particle size analysis of lacustrine core sediments and atmospheric natural dust were conducted in the drainage area of Ebinur Lake in arid northwest China. Using a combination of (137)Cs and (210)Pb dating, a continuous record of aeolian transportation to the lake sediments and related factors over about the past 150 years was analyzed. Factor analysis revealed the particle-size distributions of riverine and aeolian sediments composed of the terrigenous materials of the lake deposits. Compared with the grain-size distributions of natural dust samples, the results showed that the coarser particle size fraction of lake sediments was mainly derived from the sediments that had experienced aeolian transport to the drainage surface, and the finer sediments came from hydraulic inputs. Then, the method of variations in particle-size standard deviation was used to extract the grain size intervals with the highest variability along a sedimentary sequence. The coarser grain-size populations dominated the variation patterns of the sedimentary sequence. During the last 150 years, strong intensity aeolian transportation occurred during three periods, 1915-1935, 1965-1975 and since the beginning of the 2000s. The climate was dry around 1910s-1930s in this region associated with the appropriate dynamic condition, which provided the enhanced source materials and wind power for the aeolian dust transport. Since 1950s, the climate controlled the foundation of aeolian dust transport, and the aeolian dust transport won't be increased under the humid climate.

  20. Geochemical provenance of soils in Kerman urban areas, Iran: Implications for the influx of aeolian dust

    NASA Astrophysics Data System (ADS)

    Dehbandi, Reza; Aftabi, Alijan

    2016-06-01

    The investigation of the interaction of aeolian dust with residual soils has not been fully explored in the Kerman urban areas, Iran. To assess the geochemical influence of aeolian dust on the residual soils of the Kerman urban areas of Iran, 27 samples were studied petrogeochemically. The arid-semi-arid climate of the area together with the southwest-northeast prevailing wind, have deposited aeolian sands over the residual soils. Residual soils reflect similar mineral compositions to that of the underlying bedrock and include mostly calcite and quartz. However, the minor occurrences of pyroxene, amphibole, olivine, plagioclase and volcanic clasts in urban soils and aeolian dust are attributed to volcanogenic inputs transported by aeolian dust. Urban soils and aeolian dust show different geochemical signatures from the local carbonate rocks. All samples contain trace element concentrations that are higher than the carbonate bedrock. Discrimination diagrams indicate that immobile trace elements have geochemical affinity to the detrital ferromagnesian dust inputs and are different from the local carbonate bedrock. Based on the elemental bivariate and ternary diagrams, the soils and aeolian dust are derived from the interaction of carbonate and volcanic rocks. This highlights that the urban soils in the Kerman urban areas have been formed by interactions of the aeolian dust with the primitive residual soils.

  1. Aeolian Removal of Dust Types from Photovoltaic Surfaces on Mars

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Perez-Davis, Marla E.

    1990-01-01

    Dust elevated in local or global dust storms on the Martian surface could settle on photovoltaic (PV) surfaces and seriously hamper their performance. Using a recently developed technique to apply a uniform dust layer, PV surface materials were subjected to simulated Martian winds in an attempt to determine whether natural aeolian processes on Mars would sweep off the settled dust. Three different types of dust were used. The effects of wind velocity, angle of attack, height above the Martian surface, and surface coating material were investigated. It was found that arrays mounted on an angle of attack approaching 45 deg show the most efficient clearing. Although the angular dependence is not sharp, horizontally mounted arrays required much higher wind velocities to clear off the dust. From this test it appears that the arrays may be erected quite near the ground, but previous studies have suggested that saltation effects can be expected to cause such arrays to be covered by soil if they are set up less than about a meter from the ground. Particle size effect appear to dominate over surface chemistry in these experiments, but additional tests are required to confirm this.

  2. Aeolian Removal of Dust Types from Photovoltaic Surfaces on Mars

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Perez-Davis, Marla E.; Marabito, Mark

    1990-01-01

    Dust elevated in local or global dust storms on the Martian surface could settle on photovoltaic (PV) surfaces and seriously hamper their performance. Using a recently developed technique to apply a uniform dust layer, PV surface materials were subjected to simulated Martian winds in an attempt to determine whether natural Aeolian processes on Mars would sweep off the settled dust. Three different types of dust were used; an optical polishing powder, basaltic "trap rock", and iron (III) oxide crystals. The effects of wind velocity, angle of attack, height above the Martian surface, and surface coating material were investigated. It was found that arrays mounted with an angle of attack approaching 45 degrees show the most efficient clearing. Although the angular dependence is not sharp, horizontally mounted arrays required significantly higher wind velocities to clear off the dust. From this test it appears that the arrays may be erected quite near the ground, but previous studies have suggested that saltation effects can be expected to cause such arrays to be covered by soil if they are set up less than about a meter from the ground. Particle size effects appear to dominate over surface chemistry in these experiments, but additional tests are required to confirm this. Providing that the surface chemistry of Martian dusts is not drastically different from simulated dust and that gravity differences have only minor effects, the materials used for protective coatings for photovoltaic arrays may be optimized for other considerations such as transparency, and chemical or abrasion resistance. The static threshold velocity is low enough that there are regions on Mars which experience winds strong enough to clear off a photovoltaic array if it is properly oriented. Turbulence fences proved to be an ineffective strategy to keep dust cleared from the photovoltaic surfaces.

  3. Dust on Mars: An Aeolian Threat to Human Exploration?

    NASA Technical Reports Server (NTRS)

    Marshall, J.

    1999-01-01

    The NASA HEDS Program is duly concerned for human explorers regarding the potential hazard posed by the ubiquitous dust mantle on Mars. To evaluate properties of dust that could be hazardous to humans, the NMS 2001 Lander payload will include the Mars Environmental Compatibility Assessment (MECA) experiment. This includes optical and atomic-force microscopy to evaluate soil grains for shape and size, wet chemistry to evaluate toxic substances, electrometry to evaluate triboelectric charging, and test-material palets to evaluate electrostatic and magnetic adhesion, and the hardness/abrasiveness of soil grains; these experimental subcomponents are delivered samples by the camera-equipped robotic arm of the lander which will acquire material from depths of 0.5 to 1.0 m in the soil. Data returned by MECA will be of value to both the hEDS and planetary/astrobiology communities. Dust poses a threat to human exploration because the martian system does not hydrologically or chemically remove fine particles that are being continuously generated by thermal, aeolian, and colluvial weathering, and by volcanism and impact over billions of years. The dust is extremely fine-grained, in copious quantities, ubiquitous in distribution, continually mobile, and a source of poorly-grounded static charges -- a suite of characteristics posing a particulate and electrical threat to explorers and their equipment. Dust is mobilized on global and regional scales, but probably also unpredictably and violently at local scales by dust devils. The latter might be expected in great abundance owing to near surface atmospheric instability (dust devils were detected by Pathfinder during its brief lifetime). Preliminary laboratory experiments suggest that space-suit materials subjected to windblown dust may acquire a uniform, highly adhesive dust layer that is also highly cohesive laterally owing to electrostatic forces. This layer will obscure visibility through the helmet visor, penetrate joints

  4. Aeolian transport of biota with dust: A wind tunnel experiment

    NASA Astrophysics Data System (ADS)

    Rivas, J. A., Jr.; Gill, T. E.; Van Pelt, R. S.; Walsh, E.

    2015-12-01

    Ephemeral wetlands are ideal sources for dust emission, as well as repositories for dormant stages of aquatic invertebrates. An important component of invertebrate dispersal and colonization to new areas is the ability to be entrained into the atmosphere. Aquatic invertebrate eggs fall within the size of dust and sand grains (30-600μm), are less dense and aerodynamically shaped. We have shown previously that aquatic invertebrates can be dispersed long distances in dust storms but the extent of transport of taxa based on diapausing egg size/morphology has not been investigated. Here, we control the wind erosion process in a wind tunnel to test entrainment of diapausing stages of brine shrimp, clam shrimp, tadpole shrimp, fairy shrimp, Daphnia, and the rotifers Brachionus plicatilis and B. calyciflorus into the air by saltation. Diapausing eggs were mixed with sterilized wind-erodible soil. The soil/egg mixture was moistened with distilled water and air dried to form a crust. Dust was generated in a wind tunnel by releasing sand grains that act as saltator material similar to wind-entrained natural sands. Maximum wind velocity was 10m/s and entrained particles were sampled through an isokinetic horizontal intake opening. Aeolian sediment was collected from three points in the system; transfer section for coarse sediment, the pan subtending a settling chamber for finer saltation-sized sediment, and two paper filters for suspension-sized sediment. Samples were then passed through 250 and 350 μm sieves to remove abrader sand and rehydrated with various sterile media depending on the type of organism. We retrieved viable brine, fairy, and tadpole shrimp, ostracods, Daphnia, and diapausing eggs of the rotifers after hydration. This experiment demonstrates that resting stages of many invertebrates can be wind-eroded due to size and egg morphology and remain viable under controlled conditions mimicking dust emission.

  5. Aeolian dust dynamics in central Asia during the Pleistocene: Driven by the long-term migration, seasonality, and permanency of the Asiatic polar front

    NASA Astrophysics Data System (ADS)

    Machalett, Björn; Oches, Eric A.; Frechen, Manfred; Zöller, Ludwig; Hambach, Ulrich; Mavlyanova, Nadira G.; Marković, Slobodan B.; Endlicher, Wilfried

    2008-08-01

    Loess-paleosol sequences preserve detailed archives of climate change, reflecting the dynamics of aeolian dust sedimentation and the paleodust content of the atmosphere. The detailed investigation of particle size distributions (PSDs) of windblown sediments is an increasingly used approach to assess the paleorecord of aeolian dust dynamics. The central Asian loess belt offers the potential to reconstruct Pleistocene atmospheric circulation patterns along an adjacent west-east transect within interior Eurasia through granulometric studies. In this study we present the aeolian dust record of the loess sequence at Remisowka (SE Kazakhstan), which reflects a detailed signal of glacial-interglacial climate and atmospheric dynamics in central Asia. On the basis of radiocarbon and amino acid geochronologic data, long-term semicontinuous trends in the aeolian dust record of the Last Glacial Cycle are observed and interpreted to reveal their paleoclimate signal. In consideration of the modern synoptical atmospheric circulation patterns and aeolian dust transport in central Asia, it is likely that the observed trends reflect the long-term migration, seasonal duration, and permanency of the polar front during the late Pleistocene. Previously published models, which focused on the reciprocal glacial-interglacial influence of the zonal Westerlies and the Asiatic high on the aeolian dust transport in central Asia, were overly simplified and should be modified to include the major influence of the Asiatic polar front. As the polar front activity is intimately connected with the development and position of the interhemispherically active, high-level planetary frontal zone (HPFZ), the presented data give insight to long-term aeolian dust dynamics and climate variability of interior Eurasia, which are linked with interhemispheric climates.

  6. Changes in soil aggregation and dust emission potential in response to aeolian processes

    NASA Astrophysics Data System (ADS)

    swet, Nitzan; Katra, Itzhak

    2016-04-01

    Aeolian (wind) dust emission has high environmental and socioeconomic significances due to loss of natural soil and air pollution. Dust emission involves complex interactions between the airflow and the soil surface. The soil aggregates were dust particles are held determine the topsoil erodibility in aeolian erosion. Although the key role of soil aggregation in dust emission mechanisms, information on changes in soil aggregate size distribution (ASD) due to aeolian erosion is lucking. This study is focused on quantitative ASD analyses before and after aeolian processes (saltation). Aeolian experiments and soil analyses were conducted on semiarid loess topsoils with different initial conditions of aggregation. The results show that saltation rates and PM emissions depend on the initial ASD and shear velocity. In all initial soil conditions, the content of aggregates at saltator-sized 63-250 μm was increased by 10-34 % following erosion of macro-aggregates > 500 μm. It revealed that the aggregate-saltator production increases with the shear velocity (up to 0.61 m s-1) for soils with available macro-aggregates. The findings highlight the dynamics in soil aggregation in response to aeolian transport and therefore its significance for determining the mechanisms of dust emission from soil aggregates.

  7. Global connections between aeolian dust, climate and ocean biogeochemistry at the present day and at the last glacial maximum

    NASA Astrophysics Data System (ADS)

    Maher, B. A.; Prospero, J. M.; Mackie, D.; Gaiero, D.; Hesse, P. P.; Balkanski, Y.

    2010-04-01

    Palaeo-dust records in sediments and ice cores show that wind-borne mineral aerosol ('dust') is strongly linked with climate state. During glacial climate stages, for example, the world was much dustier, with dust fluxes two to five times greater than in interglacial stages. However, the influence of dust on climate remains a poorly quantified and actively changing element of the Earth's climate system. Dust can influence climate directly, by the scattering and absorption of solar and terrestrial radiation, and indirectly, by modifying cloud properties. Dust transported to the oceans can also affect climate via ocean fertilization in those regions of the world's oceans where macronutrients like nitrate are abundant but primary production and nitrogen fixation are limited by iron scarcity. Dust containing iron, as fine-grained iron oxides/oxyhydroxides and/or within clay minerals, and other essential micronutrients (e.g. silica) may modulate the uptake of carbon in marine ecosystems and, in turn, the atmospheric concentration of CO 2. Here, in order to critically examine past fluxes and possible climate impacts of dust in general and iron-bearing dust in particular, we consider present-day sources and properties of dust, synthesise available records of dust deposition at the last glacial maximum (LGM); evaluate the evidence for changes in ocean palaeo-productivity associated with, and possibly caused by, changes in aeolian flux to the oceans at the LGM; and consider the radiative forcing effects of increased LGM dust loadings.

  8. Downwind changes in grain size of aeolian dust; examples from marine and terrestrial archives

    NASA Astrophysics Data System (ADS)

    Stuut, Jan-Berend; Prins, Maarten

    2013-04-01

    references Betzer, P.R., Carder, K.L., Duce, R.A., Merrill, J.T., Tindale, N.W., Uematsu, M., Costello, D.K., Young, R.W., Feely, R.A., Breland, J.A., Bernstein, R.E., Greco, A.M., 1988. Long-range transport of giant mineral aerosol particles. Nature 336, 568. Claquin, T., Roelandt, C., Kohfeld, K.E., Harrison, S.P., Tegen, I., C., P.I., Balkanski, Y., Bergametti, G., Hansson, M., Mahowald, N.M., Rodhe, H., Schulz, M., 2003. Radiative forcing of climate by ice-age atmospheric dust. Climate Dynamics 20, 193-202. Holz, C., Stuut, J.-B.W., Henrich, R., 2004. Terrigenous sedimentation processes along the continental margin off NW-Africa: implications from grain-size analyses of surface sediments. Sedimentology 51, 1145-1154. Otto, S., de Reus, M., Trautmann, T., Thomas, A., Wendisch, M., Borrmann, S., 2007. Atmospheric radiative effects of an in situ measured Saharan dust plume and the role of large particles. Atmos. Chem. Phys. 7, 4887-4903. Prins, M.A., Weltje, G.J., 1999. End-member modeling of siliciclastic grain-size distributions: the Late Quaternary record of eolian and fluvial sediment supply to the Arabian Sea and its paleoclimatic significance., in: Harbaugh, J., Watney, L., Rankey, G., Slingerland, R., Goldstein, R., Franseen, E. (Eds.), Numerical experiments in stratigraphy: Recent advances in stratigraphic and sedimentologic computer simulations. SEPM Special Publication 62. Society for Sedimentary Geology, pp. 91-111. Prins, M.A., Vriend, M., 2007, Glacial and interglacial eolian dust dispersal patterns across the Chinese Loess Plateau inferred from decomposed loess grain-size records. Geochemistry, Geophysics, Geosystems (G-cubed), 8, Q07Q05, doi:10.1029/2006GC001563. Prins, M.A., Vriend, M., Nugteren, G., Vandenberghe, J., Lu, H., Zheng, H., Jan Weltje, G., 2007. Late Quaternary aeolian dust input variability on the Chinese Loess Plateau: inferences from unmixing of loess grain-size records. Quaternary Science Reviews 26, 230-242. Prins, M.A., Zheng, H., Beets, K

  9. Compositional trends in aeolian dust along a transect across the southwestern United States

    NASA Astrophysics Data System (ADS)

    Goldstein, Harland L.; Reynolds, Richard L.; Reheis, Marith C.; Yount, James C.; Neff, Jason C.

    2008-06-01

    Aeolian dust strongly influences ecology and landscape geochemistry over large areas that span several desert ecosystems of the southwestern United States. This study evaluates spatial and temporal variations and trends of the physical and chemical properties of dust in the southwestern United States by examining dust deposited in natural depressions on high isolated surfaces along a transect from the Mojave Desert to the central Colorado Plateau. Aeolian dust is recognized in these depressions on the basis of textural, chemical, isotopic, and mineralogical characteristics and comparisons of those characteristics to the underlying bedrock units. Spatial and temporal trends suggest that although local dust sources are important to the accumulated material in these depressions, Mojave Desert dust sources may also contribute. Depth trends in the depressions suggest that Mojave sources may have contributed more dust to the Colorado Plateau recently than in the past. These interpretations point to the important roles of far-traveled aeolian dust for landscape geochemistry and imply future changes to soil geochemistry under changing conditions in far-distant dust source areas.

  10. Compositional trends in aeolian dust along a transect across the southwestern United States

    USGS Publications Warehouse

    Goldstein, H.L.; Reynolds, R.L.; Reheis, M.C.; Yount, J.C.; Neff, J.C.

    2008-01-01

    Aeolian dust strongly influences ecology and landscape geochemistry over large areas that span several desert ecosystems of the southwestern United States. This study evaluates spatial and temporal variations and trends of the physical and chemical properties of dust in the southwestern United States by examining dust deposited in natural depressions on high isolated surfaces along a transect from the Mojave Desert to the central Colorado Plateau. Aeolian dust is recognized in these depressions on the basis of textural, chemical, isotopic, and mineralogical characteristics and comparisons of those characteristics to the underlying bedrock units. Spatial and temporal trends suggest that although local dust sources are important to the accumulated material in these depressions, Mojave Desert dust sources may also contribute. Depth trends in the depressions suggest that Mojave sources may have contributed more dust to the Colorado Plateau recently than in the past. These interpretations point to the important roles of far-traveled aeolian dust for landscape geochemistry and imply future changes to soil geochemistry under changing conditions in far-distant dust source areas. Copyright 2008 by the American Geophysical Union.

  11. Sensitivity simulations with direct radiative forcing by aeolian dust during glacial cycles

    NASA Astrophysics Data System (ADS)

    Bauer, E.; Ganopolski, A.

    2014-01-01

    Possible feedback effects between aeolian dust, climate and ice sheets are studied for the first time with an Earth system model of intermediate complexity over the late Pleistocene period. Correlations between climate variables and dust deposits suggest that aeolian dust potentially plays an important role for the evolution of glacial cycles. Here climatic effects from the dust direct radiative forcing (DRF) caused by absorption and scattering of solar radiation are investigated. Key factors controlling the dust DRF are the atmospheric dust distribution and the absorption-scattering efficiency of dust aerosols. Effective physical parameters in the description of these factors are varied within uncertainty ranges known from available data and detailed model studies. Although the parameters are reasonably constrained by use of these studies, the simulated dust DRF spans a wide uncertainty range related to nonlinear dependencies. In our simulations, the dust DRF is highly localized. Medium-range parameters result in negative DRF of several W m-2 in regions close to major dust sources and negligible values elsewhere. In case of high absorption efficiency, the local dust DRF can reach positive values and the global mean DRF can be insignificantly small. In case of low absorption efficiency, the dust DRF can produce a significant global cooling in glacial periods which leads to a doubling of the maximum glacial ice volume relative to the case with small dust DRF. DRF-induced temperature and precipitation changes can either be attenuated or amplified through a feedback loop involving the dust cycle. The sensitivity experiments suggest that depending on dust optical parameters the DRF has the potential to either damp or reinforce glacial-interglacial climate changes.

  12. Effects of particle optical properties on grain size measurements of aeolian dust deposits

    NASA Astrophysics Data System (ADS)

    Varga, György; Újvári, Gábor; Kovács, János; Szalai, Zoltán

    2015-04-01

    Particle size data are holding crucial information on the sedimentary environment at the time the aeolian dust deposits were accumulated. Various aspects of aeolian sedimentation (wind strength, distance to source(s), possible secondary source regions and modes of sedimentation and transport) can be reconstructed from proper grain size distribution data. Laser diffraction methods provide much more accurate and reliable information on the major granulometric properties of wind-blown sediments compared to the sieve and pipette methods. The Fraunhofer and Mie scattering theories are generally used for laser diffraction grain size measurements. () The two different approaches need different 'background' information on the medium measured. During measurements following the Fraunhofer theory, the basic assumption is that parcticles are relatively large (over 25-30 µm) and opaque. The Mie theory could offer more accurate data on smaller fractions (clay and fine silt), assuming that a proper, a'priori knowledge on refraction and absorption indices exists, which is rarely the case for polymineral samples. This study is aimed at determining the effects of different optical parameters on grain size distributions (e.g. clay-content, median, mode). Multiple samples collected from Hungarian red clay and loess-paleosol records have been analysed using a Malvern Mastersizer 3000 laser diffraction particle sizer (with a Hydro LV unit). Additional grain size measurements have been made on a Fritsch Analysette 22 Microtec and a Horiba Partica La-950 v2 instrument to investigate possible effects of the used laser sources with different wavelengths. XRF and XRD measurements have also been undertaken to gain insight into the geochemical/mineralogical compositions of the samples studied. Major findings include that measurements using the Mie theory provide more accurate data on the grain size distribution of aeolian dust deposits, when we use a proper optical setting. Significant

  13. Aeolian dust deposition rates in Northern French forests and inputs to their biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Lequy, Émeline; Legout, Arnaud; Conil, Sébastien; Turpault, Marie-Pierre

    2013-12-01

    This study describes the Aeolian dust deposition (ADD) in 4 sites of Northern France. Between December 2009 and March 2012, we sampled (i) Aeolian dust every four weeks, and (ii) 6 episodes of forecasted high atmospheric dust load mainly from the Saharan desert, the largest source of Aeolian dust in the world. These samples were treated with oxygen peroxide to remove organic matter so as to only compare the mineral fraction of the samples in the 4 sampling sites and to analyze their mineralogy. The solid samples contained the hardly soluble part of Aeolian dust (H-ADD). Its deposition was of 1.9 ± 0.3 g m-2 year-1 with a seasonal pattern of high deposition from spring to early autumn and a low deposition in winter. H-ADD deposition during the forecasted episodes of high atmospheric load did not systematically exceed the deposition rate during the rest of the sampling period. This indicates that such episodes little contributed to the annual H-ADD rate. The mineralogy revealed a heterogeneous set of minerals dominated by silicates with a common basis of major types (quartz, feldspars, mica, chlorite, kaolinite and interlayered clay minerals in every sample) with randomly trace minerals (Fe-oxides, sulfates, amphibole, talc, gibbsite and carbonates). The chemistry of H-ADD led to a dominant input of Si (up to 4.4 kg ha-1 year-1), while the nutrients inputs of Ca, K, Mg and P from ADD and the atmospheric organics (APD) in openfield were together of 1.5 ± 0.5 kg ha-1 year-1 with a high contribution of soluble minerals and organic matter of ca. 40% for Mg and K, and of ca. 80% for Ca and P. Nutrient inputs from APD are especially an interesting source of P for forests developed on acidic soils.

  14. Aeolian removal of dust from radiator surfaces on Mars

    SciTech Connect

    Gaier, J.R.; Perez-Davis, M.E.; Rutledge, S.K.; Hotes, D.

    1994-09-01

    Simulated radiator surfaces made of arc-textured copper and niobium-one percent-zirconium, and ion beam textured graphite and carbon-carbon composite were fabricated and their integrated spectral emittance characterized from 300 to 3000 K. A thin layer of aluminum oxide, basalt, or iron (III) oxide dust was then deposited on them, and they were subjected to low pressure winds in the Martian Surface Wind Tunnel. It has been found that dust deposited on simulated radiator surfaces may or may not seriously lower their integrated spectral emittance, depending upon the characteristics of the dust. With Al{sub 2}O{sub 3} there is no appreciable degradation of emittance on a dusted sample, with basaltic dust there is a 10-20 percent degradation, and with Fe{sub 2}O{sub 3} a 20-40 percent degradation. It was also found that very high winds on dusted highly textured surfaces can result in their abrasion. Degradation in emittance due to abrasion was found to vary with radiator material. Arc-textured copper and Nb-1%Zr was found to be more susceptible to emittance degradation than graphite or carbon-carbon composite. The most abrasion occurred at low angles, peaking at the 22.5{degrees} test samples.

  15. Aeolian removal of dust from radiator surfaces on Mars

    NASA Technical Reports Server (NTRS)

    Gaier, James R.; Perez-Davis, Marla E.; Rutledge, Sharon K.; Hotes, Deborah

    1990-01-01

    Simulated radiator surfaces made of arc-textured Cu and Nb-1 percent-Zr and ion beam textured graphite and C-C composite were fabricated and their integrated spectral emittance characterized from 300 to 3000 K. A thin layer of aluminum oxide, basalt, or iron (III) oxide dust was then deposited on them, and they were subjected to low pressure winds in the Martian Surface Wind Tunnel. It was found that dust deposited on simulated radiator surfaces may or may not seriously lower their integrated spectral emittance, depending upon the characteristics of the dust. With Al2O3 there is no appreciable degradation of emittance on a dusted sample, with basaltic dust there is a 10 to 20 percent degradation, and with Fe2O3 a 20 to 40 percent degradation. It was also found that very high winds on dusted highly textured surfaces can result in their abrasion. Degradation in emittance due to abrasion was found to vary with radiator material. Arc-textured Cu and Nb-1 percent Zr was found to be more susceptible to emittance degradation than graphite or C-C composite. The most abrasion occurred at low angles, peaking at the 22.5 deg test samples.

  16. Mid to late Holocene aeolian activity revealed by a multiproxy peat record in continental CE Europe (Northern Romania)

    NASA Astrophysics Data System (ADS)

    Panait, Andrei Marian; Feurdean, Angelica; Hutchinson, Simon Mark; Tanţǎu, Ioan

    2016-04-01

    Peat bogs, and especially ombrogenous mire, are increasingly used as continental archives of aeolian dust and sand deposition. Since ombrogenous peat is formed above ground water level all the inputs are atmospheric. Dust is more influenced by regional climatic patterns due to its small size, whereas sand tends to record local patterns in storm frequency and intensity reflecting its larger particle size. However, both size fractions are significantly underused proxies of past climate variability. Here, an ombrogenous peat profile from Tǎul Muced in the Rodnei Mountains (Northern Romanian Carpathians), located in a temperate continental climate, with Atlantic and Baltic influences, provides the very first record of mid to late Holocene aeolian activity from Romania highlighting the interplay between local and regional controls in a continental area of CE Europe. We use a multiproxy approach combining radiocarbon dating, the physical properties of the peat (loss-on-ignition, bulk density), mineral magnetic measurements (ARM, SIRM), geochemical (Ti and Zr) and particle size analysis (via both laser diffraction and the manual counting of sand particles under a steromicroscope) to determine changes in: i) atmospheric dust deposition and ii) wind velocities during the last 7800 years. We found that the aeolian particles are mainly silt (3.9-63 μm) (dust) and sand (63-1200 μm). The mineralogical composition of the aeolian sediment in peat is mainly quartz, more rarely calcite and very rarely other minerals such as feldspar, sulphur, mica (biotite and muscovite), magnetite and other melanocrate minerals. The roundness of the sand particles varies from well-rounded to sub-angular and angular, and suggests that the sand particles have different source areas. Results from this study show that over the last 7600 years the pattern of wind frequency changed several times: there are periods characterised by a low aeolian input around 6950-6550, 5000-3900, 3500-2900, 1650

  17. A study of the management strategies for river aeolian dust inhibition at the estuary of Zhuo-shui River

    NASA Astrophysics Data System (ADS)

    Tsai, S. F.; Lin, C. Y.

    2014-12-01

    With the characteristics of humidity in summer and drought in winter, there existing lots of bare lands due to the decline of water level cause large amounts of aeolian dust and environmental deterioration during the monsoon seasons in central Taiwan. How to adopt effective measures to inhibit the damage of dust is an essential issue. This study selected the serious dust-affected section of Zhuo-shui river (bridge Zi-qiang to Xi-bin) to delineate the areas of potential aeolian dust occurrence, explore the relationship between elevation and water level determined from return period analysis, submit the countermeasures for dust inhibition at the bare lands and/or cultivated areas, and address the responsibilities of related authority offices for dust prevention by means of literature review. The return period of inundation for the areas of potential aeolian dust occurrence is 1.1 years. Engineering of dust prevention with highly unit price are not recommended due to could be destroyed annually. The deposition sites of a river are usually located at the convex bank, which with silt texture and high salinity are not suitable for cultivation, are delineated as the areas of potential aeolian dust occurrence. Besides technology consideration in dust prevention, this study also examined the related articles of river management to integrate a comprehensive vision for better riverside environment and air quality.

  18. Aeolian dust experiment on climate impact: An overview of Japan China joint project ADEC

    NASA Astrophysics Data System (ADS)

    Mikami, M.; Shi, G. Y.; Uno, I.; Yabuki, S.; Iwasaka, Y.; Yasui, M.; Aoki, T.; Tanaka, T. Y.; Kurosaki, Y.; Masuda, K.; Uchiyama, A.; Matsuki, A.; Sakai, T.; Takemi, T.; Nakawo, M.; Seino, N.; Ishizuka, M.; Satake, S.; Fujita, K.; Hara, Y.; Kai, K.; Kanayama, S.; Hayashi, M.; Du, M.; Kanai, Y.; Yamada, Y.; Zhang, X. Y.; Shen, Z.; Zhou, H.; Abe, O.; Nagai, T.; Tsutsumi, Y.; Chiba, M.; Suzuki, J.

    2006-07-01

    The Aeolian Dust Experiment on Climate Impact (ADEC) was initiated in April 2000 as a joint five-year Japan-China project. The goal was to understand the impact of aeolian dust on climate via radiative forcing (RF). Field experiments and numerical simulations were conducted from the source regions in northwestern China to the downwind region in Japan in order to understand wind erosion processes temporal and spatial distribution of dust during their long-range transportation chemical, physical, and optical properties of dust and the direct effect of radiative forcing due to dust. For this, three intensive observation periods (IOP) were conducted from April 2002 to April 2004. The in situ and network observation results are summarized as follows: (1) In situ observations of the wind erosion process revealed that the vertical profile of moving sand has a clear size dependency with height and saltation flux and that threshold wind velocity is dependent on soil moisture. Results also demonstrated that saltation flux is strongly dependent on the parent soil size distribution of the desert surface. (2) Both lidar observations and model simulations revealed a multiple dust layer in East Asia. A numerical simulation of a chemical transport model, CFORS, illustrated the elevated dust layer from the Taklimakan Desert and the lower dust layer from the Gobi Desert. The global-scale dust model, MASINGAR, also simulated the dust layer in the middle to upper free troposphere in East Asia, which originated from North Africa and the Middle East during a dust storm in March 2003. Raman lidar observations at Tsukuba, Japan, found the ice cloud associated with the dust layer at an altitude of 6 to 9 km. Analysis from lidar and the radio-sonde observation suggested that the Asian dust acted as ice nuclei at the ice-saturated region. These results suggest the importance of dust's climate impact via the indirect effect of radiative forcing due to the activation of dust into ice nuclei

  19. Terrestrial sensitivity to abrupt cooling recorded by aeolian activity in northwest Ohio, USA

    USGS Publications Warehouse

    Campbell, M.C.; Fisher, T.G.; Goble, R.J.

    2011-01-01

    Optically stimulated luminescence dated sand dunes and Pleistocene beach ridges in northwest Ohio are used to reconstruct landscape modification more than 5000. yr after deglaciation. Four of the OSL ages (13.3-11.1. ka) cluster around the Younger Dryas cold event, five ages (10.8-8.2. ka) cluster around the Preboreal, one young age (0.9-0.7. ka) records more recent aeolian activity, and one age of 15.1-13.1. ka dates a barrier spit in Lake Warren. In northwest Ohio, both landscape instability recorded by aeolian activity and a vegetation response recorded by pollen are coeval with the Younger Dryas. However, the climate conditions during the Preboreal resulting in aeolian activity are not recorded in the available pollen records. From this, we conclude that aeolian dunes and surfaces susceptible to deflation are sensitive to cooler, drier episodes of climate and can complement pollen data. Younger Dryas and Preboreal aged aeolian activity in northwestern Ohio coincides with aeolian records elsewhere in the Great Lakes region east of the prairie-forest ecotone. ?? 2011 University of Washington.

  20. Aeolian dust emissions in Southern Africa: field measurements of dynamics and drivers

    NASA Astrophysics Data System (ADS)

    Wiggs, Giles; Thomas, David; Washington, Richard; King, James; Eckardt, Frank; Bryant, Robert; Nield, Joanna; Dansie, Andrew; Baddock, Matthew; Haustein, Karsten; Engelstaedter, Sebastian; von Holdt, Johannah; Hipondoka, Martin; Seely, Mary

    2016-04-01

    Airborne dust derived from the world's deserts is a critical component of Earth System behaviour, affecting atmospheric, oceanic, biological, and terrestrial processes as well as human health and activities. However, very few data have been collected on the factors that control dust emission from major source areas, or on the characteristics of the dust that is emitted. Such a paucity of data limits the ability of climate models to properly account for the radiative and dynamical impacts triggered by atmospheric dust. This paper presents field data from the DO4 Models (Dust Observations for Models) project that aims to understand the drivers of variability in dust emission processes from major source areas in southern Africa. Data are presented from three field campaigns undertaken between 2011 and 2015. We analysed remote sensing data to identify the key geomorphological units in southern Africa which are responsible for emission of atmospheric dust. These are the Makgadikgadi pans complex in northern Botswana, the ephemeral river valleys of western Namibia, and Etosha Pan in northern Namibia. Etosha Pan is widely recognised as perhaps the most significant source of atmospheric dust in the southern hemisphere. We deployed an array of field equipment within each source region to measure the variability in and dynamics of aeolian erosivity, as well as dust concentration and flux characteristics. This equipment included up to 11 meteorological stations measuring wind shear stress and other standard climatic parameters, Cimel sun photometers, a LiDAR, sediment transport detectors, high-frequency dust concentration monitors, and dust flux samplers. Further data were gathered at each site on the dynamics of surface characteristics and erodibility parameters that impact upon erosion thresholds. These data were augmented by use of a Pi-Swerl portable wind tunnel. Our data represent the first collected at source for these key dust emission areas and highlight the

  1. The geologic records of dust in the Quaternary

    USGS Publications Warehouse

    Muhs, Daniel R.

    2013-01-01

    Study of geologic records of dust composition, sources and deposition rates is important for understanding the role of dust in the overall planetary radiation balance, fertilization of organisms in the world’s oceans, nutrient additions to the terrestrial biosphere and soils, and for paleoclimatic reconstructions. Both glacial and non-glacial processes produce fine-grained particles that can be transported by the wind. Geologic records of dust flux occur in a number of depositional archives for sediments: (1) loess deposits; (2) lake sediments; (3) soils; (4) deep-ocean basins; and (5) ice sheets and smaller glaciers. These archives have several characteristics that make them highly suitable for understanding the dynamics of dust entrainment, transport, and deposition. First, they are often distributed over wide geographic areas, which permits reconstruction of spatial variation of dust flux. Second, a number of dating methods can be applied to sediment archives, which allows identification of specific periods of greater or lesser dust flux. Third, aeolian sediment particle size and composition can be determined so that dust source areas can be ascertained and dust transport pathways can be reconstructed. Over much of the Earth’s surface, dust deposition rates were greater during the last glacial period than during the present interglacial period. A dustier Earth during glacial periods is likely due to increased source areas, greater aridity, less vegetation, lower soil moisture, possibly stronger winds, a decreased intensity of the hydrologic cycle, and greater production of dust-sized particles from expanded ice sheets and glaciers.

  2. The geologic records of dust in the Quaternary

    NASA Astrophysics Data System (ADS)

    Muhs, Daniel R.

    2013-06-01

    Study of geologic records of dust composition, sources and deposition rates is important for understanding the role of dust in the overall planetary radiation balance, fertilization of organisms in the world's oceans, nutrient additions to the terrestrial biosphere and soils, and for paleoclimatic reconstructions. Both glacial and non-glacial processes produce fine-grained particles that can be transported by the wind. Geologic records of dust flux occur in a number of depositional archives for sediments: (1) loess deposits; (2) lake sediments; (3) soils; (4) deep-ocean basins; and (5) ice sheets and smaller glaciers. These archives have several characteristics that make them highly suitable for understanding the dynamics of dust entrainment, transport, and deposition. First, they are often distributed over wide geographic areas, which permits reconstruction of spatial variation of dust flux. Second, a number of dating methods can be applied to sediment archives, which allows identification of specific periods of greater or lesser dust flux. Third, aeolian sediment particle size and composition can be determined so that dust source areas can be ascertained and dust transport pathways can be reconstructed. Over much of the Earth's surface, dust deposition rates were greater during the last glacial period than during the present interglacial period. A dustier Earth during glacial periods is likely due to increased source areas, greater aridity, less vegetation, lower soil moisture, possibly stronger winds, a decreased intensity of the hydrologic cycle, and greater production of dust-sized particles from expanded ice sheets and glaciers.

  3. Effects of forest litter and aeolian dust deposition on snow surface albedo

    NASA Astrophysics Data System (ADS)

    Perrot, D.; Pugh, E. T.; Molotch, N. P.; Small, E. E.

    2011-12-01

    Litter from bark beetle-infested trees and aeolian dust deposition are current perturbations to the snowpack surface albedo in subalpine forested environments in the Colorado River Basin. We examine the combined effects of dust and litter on snow surface albedo through field and controlled laboratory modification of snow surface dust and litter concentrations. From field experiments, applications of needles resulted in an albedo decrease of 0.0146 per percent increase in litter cover. Dust application resulted in an albedo decrease of 0.0061 per percent increase in litter cover. Needle application to a dusty snow surface resulted in 0.0043 albedo reduction per percent litter cover, and dust application to a snow surface with needles already present resulted in 0.0036 albedo reduction per percent litter cover. We tested the effects of yellow and red lodgepole needles on albedo reduction both in the field and the laboratory, and though yellow needles are slightly smaller, found that there is no significant difference between the slopes of yellow and red needles. However, there is a significant difference between the laboratory and field experiments resulting from different media (snow in the field and a whiteboard in the lab) that litter was applied to. Generally, we also find that it takes 120.7 lodgepole pine needles to affect the same increase in percent litter cover as 1 g/m2 of dust, and that it takes 53.2 needles to affect the same reduction in albedo as 1 g/m2 of dust. This suggests that per unit surface area, needles are more important than dust for albedo reduction. Experiments performed in the field and in the lab demonstrate the stronger albedo reducing effect of needles. However, dust has a greater capacity to cover more snow surface area than needles, increasing its overall importance. Because dust can cover more snow surface area than needles can, we suspect that dust deposition in forested environments will serve to significantly reduce subcanopy

  4. Asian dust transport during the last century recorded in Lake Suigetsu sediments

    NASA Astrophysics Data System (ADS)

    Nagashima, Kana; Suzuki, Yoshiaki; Irino, Tomohisa; Nakagawa, Takeshi; Tada, Ryuji; Hara, Yukari; Yamada, Kazuyoshi; Kurosaki, Yasunori

    2016-03-01

    Asian dust has a significant impact on the natural environment. Its variability on multiple timescales modulates the ocean biogeochemistry and climate. We demonstrate that temporal changes in the deposition flux of Aeolian dust recorded in sediments from Lake Suigetsu, central Japan, during the last century exhibit a continuous decreasing trend and a decadal-scale decrease in 1952-1974. The former decreasing trend can be explained by a decrease in the dust storm frequency at source regions due to the warming of Mongolia in the twentieth century, suggesting future decrease of Asian dust transport with further warming in Mongolia. Decadal-scale decrease of Aeolian dust is explained by weaker westerlies in lower latitudes in central Japan, reflecting a weaker Aleutian Low during the corresponding period. Decadal-scale westerly change probably causes north-south shifts of the dominant dust transport path, which affects subarctic northern Pacific Ocean biogeochemistry by changing the micronutrient iron supply.

  5. 26Al/10Be dating of an aeolian dust mantle soil in western New South Wales, Australia

    NASA Astrophysics Data System (ADS)

    Fisher, Adrian; Fink, David; Chappell, John; Melville, Michael

    2014-08-01

    Aeolian dust mantle soils are an important element of many landscapes in south-eastern Australia, though the age of these aeolian deposits has not been radiometrically determined. At Fowlers Gap in western New South Wales, surface cobbles of silcrete and quartz overlie a stone-free, aeolian dust mantle soil, which has a thickness of about 1.6 m. The clay-rich aeolian dust deposit in turn lies upon a buried silcrete and quartz stone layer. Modelling in-situ cosmogenic 26Al and 10Be concentrations measured in both the surface quartz stones and in the buried quartz layer of rocks, reveals that each has experienced a complex exposure-burial history. Due to the absence of quartz stones or sand at intermediate depths, our cosmogenic 26Al and 10Be modelling was not able to determine a definitive mechanism of stone pavement formation and stone burial. Various scenarios of stone formation, transport, burial and exhumation were tested that constrain the age of the deposit to range from 0.9 ± 0.2 Ma to 1.8 ± 0.2 Ma, based largely on different assumptions taken for the time-dependency of the net sedimentation rate. This corresponds with the initiation of the Simpson Desert dune fields and the deflation of lakes in central Australia, which probably responded to the shift to longer-wavelength, larger-amplitude Quaternary glacial cycles at around 1 Ma. Sensitivity analyses were carried out to identify those parameters which better constrained model outputs. Within model errors, which largely are the result of analytical errors in measured 26Al and 10Be concentrations, all three competing theories of colluvial wash, upward displacement of stones, and cumulic pedogenesis are possible mechanisms for the formation of the surface stone pavement.

  6. Aeolian sedimentary processes at the Bagnold Dunes, Mars: Implications for modern dune dynamics and sedimentary structures in the aeolian stratigraphic record of Mars

    NASA Astrophysics Data System (ADS)

    Ewing, Ryan C.; Bridges, Nathan T.; Sullivan, Rob; Lapotre, Mathieu G. A.; Fischer, Woodward W.; Lamb, Mike P.; Rubin, David M.; Lewis, Kevin W.; Gupta, Sanjeev

    2016-04-01

    Wind-blown sand dunes are ubiquitous on the surface of Mars and are a recognized component of the martian stratigraphic record. Our current knowledge of the aeolian sedimentary processes that determine dune morphology, drive dune dynamics, and create aeolian cross-stratification are based upon orbital studies of ripple and dune morphodynamics, rover observations of stratification on Mars, Earth analogs, and experimental and theoretical studies of sand movement under Martian conditions. In-situ observations of sand dunes (informally called the Bagnold Dunes) by Curiosity Rover in Gale Crater, Mars provide the first opportunity to make observations of dunes from the grain-to-dune scale thereby filling the gap in knowledge between theory and orbital observations and refining our understanding of the martian aeolian stratigraphic record. We use the suite of cameras on Curiosity, including Navigation Camera (Navcam), Mast Camera (Mastcam) and Mars Hand Lens Imager (MAHLI), to make observations of the Bagnold Dunes. Measurements of sedimentary structures are made where stereo images are available. Observations indicate that structures generated by gravity-driven processes on the dune lee slopes, such as grainflow and grainfall, are similar to the suite of aeolian sedimentary structures observed on Earth and should be present and recognizable in Mars' aeolian stratigraphic record. Structures formed by traction-driven processes deviate significantly from those found on Earth. The dune hosts centimeter-scale wind ripples and large, meter-scale ripples, which are not found on Earth. The large ripples migrate across the depositional, lee slopes of the dune, which implies that these structures should be present in Mars' stratigraphic record and may appear similar to compound-dune stratification.The Mars Science Laboratory Curiosity Rover Team is acknowledged for their support of this work.

  7. Aeolian dust deposition during the Eocene-Oligocene in central to eastern Asia

    NASA Astrophysics Data System (ADS)

    Vandenberghe, Jef; Abels, Hemmo; van Cappelle, Marijn

    2015-04-01

    Aeolian dust deposition during the Eocene-Oligocene in central to eastern Asia Jef Vandenberghe1, Hemmo Abels2 and Marijn van Cappelle3 1Dept. of Earth Sciences, Vrije Universiteit, 1081 HV Amsterdam, The Netherlands 2Dept. of Earth Sciences, Universiteit Utrecht, 3584 CD, Utrecht, The Netherlands 3Dept. of Earth Science and Engineering, Imperial College London, London, SW7 2AZ, U.K. The deposition of loess is generally attributed to a monsoonal climate system. Recently it has been shown that such a system existed already at the end of the Eocene on the northeastern Tibetan Plateau (Licht et al., 2014). One of the main arguments to prove the supply of loess by monsoonal winds is the use of grain size properties. The lower part of the Shuiwan section (Eocene) consists of metre-scale alternations of mudstone and gypsum beds; the upper part (Oligocene) is mainly mudstone (Dupont-Nivet et al., 2007; Abels et al., 2010). Sediments are categorized in six grain-size types based on the grain-size distribution and the mode of the silt grain sizes as measured using laser diffraction. Sediments of type 1, the only type with a unimodal grain-size distribution, consist exclusively of clay-sized particles (modal value of 2-2.5 µm). Types 2-6 have a multimodal composition. They contain an additional silt-sized fraction with a modal size of c. 16 µm in type 2; c. 26 µm in type 3 and c. 31 µm in type 4. Type 5 is a mixture of previous types, and type 6 contains in addition a slight amount of sand. Similar bimodal grain-size distributions occur in the Neogene Red Clay and in the Pleistocene loess of the Chinese Loess Plateau. All three silt fractions (with modal sizes 16, 26 and 31 µm) represent typical loess sediments, transported by dust storms in suspension at different altitudes. Their exact grain size depends on wind velocity, source material and transport distance. The 'clay component' may have settled from high suspension clouds in the air down to dry ground or to

  8. Rates and environmental controls of aeolian dust accumulation, Athabasca River Valley, Canadian Rocky Mountains

    NASA Astrophysics Data System (ADS)

    Hugenholtz, Chris H.; Wolfe, Stephen A.

    2010-09-01

    Despite an abundance of sedimentary archives of mineral dust (i.e. loess) accumulations from cold, humid environments, the absence of contemporary process investigations limits paleoenvironmental interpretations in these settings. Dust accumulations measured at Jasper Lake, a seasonally-filled reach of the glacially-fed Athabasca River in the Canadian Rocky Mountains, are some of the highest contemporary rates recorded to date. High deposition rates, including a maximum of 27,632 kg ha -1 month -1, occur during river low-flow periods, but even the lowest deposition rates, occurring during bankfull periods, exceed other contemporary rates of deposition. High rates of dust deposition may be attributed to geomorphic and climatic controls affecting sediment supply, availability and transport, and biologic factors affecting accumulation. Localized confinement of the Jasper River by tributary river alluvial fans has caused channel expansion upstream, and formation of the shallow depositional basin known as Jasper Lake. This localized sedimentary basin, coupled with large seasonal water level fluctuations and suitably high wind speeds, favors seasonal dust production. In addition, a dense source-proximal coniferous forest stand encourages high dust accumulation, via increased aerodynamic roughness and airflow deceleration. The forest stand also appears to act as an efficient dust filter, with the interception and storage of dust by the forest canopy playing a significant role with regards to secondary fallout and sediment accumulation. Overall, these results provide new insights on the environmental controls of dust entrainment and accumulation in cold, humid settings, and help clarify controls on the formation of Holocene river-sourced loess deposits.

  9. Geochemical fingerprint of desert surface sediments and aeolian dust exported from southern South America

    NASA Astrophysics Data System (ADS)

    Gili, S.; Gaiero, D. M.; Jweda, J.; Koestner, E.; Chemale, F.; Kaplan, M. R.; Goldstein, S. L.

    2012-12-01

    the "arid diagonal": a) the Altiplano and Puna have chemical and isotopic compositions inherited from the large volume of Cenozoic ignimbrites and from the Late Paleozoic granitoids (south of 21°S), respectively, b) the potential dust source in central-western Argentina appears to show a separate geochemical fingerprint explained basically by the mixing of metamorphic rocks from Eastern Sierras Pampeanas, Central Argentina and, c) dust from Patagonia with clear chemical/isotopic signatures characteristic of the Quaternary volcanism (Gaiero et al., 2004; 2007). These results are promising, as they would enable the identification of the main dust source regions in provenance studies of different paleoclimatic records (Pampean loess, Antarctic ice cores, Atlantic and Southern oceans, etc).

  10. New mineral dust record from the TALDICE ice core (East Antarctica)

    NASA Astrophysics Data System (ADS)

    Maggi, V.; Delmonte, B.; Albani, S.; Mazzola, C.

    2010-12-01

    Aeolian mineral dust is an active component of the climate system, interacting both directly and indirectly with radiation and biogeochemistry. Its deposition and stratigraphical preservation in appropriate environmental setting leaves deposits that once dated can be used as paleoclimate proxies. In particular dust records from ice cores can provide insights into past variations of environmental conditions at the dust source areas, atmospheric circulation, the hydrological cycle at source and deposition sites and dust deposition mechanisms. Here we present the new dust record from the 1620 m deep TALDICE ice core, drilled at Talos Dome (159°11' E, 72°49' S, 2315 m A.S.L.), on the edge of the East Antarctic plateau, about 290 km from the Southern Ocean and 250 km from the Ross Sea. We analysed variations in dust concentration, depositional flux, size distributions and geochemical fingerprint. The TALDICE dust records confirms the major findings from previous ice core studies in terms of the big glacial/interglacial variations in dust deposition, thanks to the relatively high accumulation rate and good dating. We also show new peculiar aspects emerging for this record, such as the importance of Antarctic sources for dust for this peripheral sites and the relation between variations in dust deposition during the deglaciation and the Holocene to variations in the atmospheric circulation in the Ross Sea.

  11. Atmospheric dust in modern soil on aeolian sandstone, Colorado Plateau (USA): Variation with landscape position and contribution to potential plant nutrients

    USGS Publications Warehouse

    Reynolds, R.; Neff, J.; Reheis, M.; Lamothe, P.

    2006-01-01

    Rock-derived nutrients in soils originate from both local bedrock and atmospheric dust, including dust from far-distant sources. Distinction between fine particles derived from local bedrock and from dust provides better understanding of the landscape-scale distribution and abundance of soil nutrients. Sandy surficial deposits over dominantly sandstone substrates, covering vast upland areas of the central Colorado Plateau, typically contain 5-40% silt plus clay, depending on geomorphic setting and slope (excluding drainages and depressions). Aeolian dust in these deposits is indicated by the presence of titanium-bearing magnetite grains that are absent in the sedimentary rocks of the region. Thus, contents of far-traveled aeolian dust can be estimated from magnetic properties that primarily reflect magnetite content, such as isothermal remanent magnetization (IRM). Isothermal remanent magnetization was measured on bulk sediment samples taken along two transects in surficial sediment down gentle slopes away from sandstone headwalls. One transect was in undisturbed surficial sediment, the other in a setting that was grazed by domestic livestock until 1974. Calculation of far-traveled dust contents of the surficial deposits is based on measurements of the magnetic properties of rock, surficial deposits, and modern dust using a binary mixing model. At the undisturbed site, IRM-based calculations show a systematic down-slope increase in aeolian dust (ranging from 2% to 18% of the surface soil mass), similar to the down-slope increase in total fines (18-39% of surface soil mass). A combination of winnowing by wind during the past and down-slope movement of sediment likely accounts for the modern distribution of aeolian dust and associated nutrients. At the previously grazed site, dust also increases down slope (5-11%) in sediment with corresponding abundances of 13-25% fines. Estimates of the contributions of aeolian dust to the total soil nutrients range widely

  12. Modern and Holocene aeolian dust variability from Talos Dome (Northern Victoria Land) to the interior of the Antarctic ice sheet

    NASA Astrophysics Data System (ADS)

    Delmonte, B.; Baroni, C.; Andersson, P. S.; Narcisi, B.; Salvatore, M. C.; Petit, J. R.; Scarchilli, C.; Frezzotti, M.; Albani, S.; Maggi, V.

    2013-03-01

    High-elevation sites from the inner part of the East Antarctic plateau sample windborne dust representative of large portions of the Southern hemisphere, and are sensitive to long-range atmospheric transport conditions to polar areas. On the periphery of the ice sheet, conversely, the aeolian transport of particles from high-elevation ice-free areas can locally represent a relatively important additional input of dust to the atmosphere, and the interplay of atmospheric dynamics, dust transport and deposition is strictly related to the regional atmospheric circulation behaviour both at present-day and in the past. The understanding of the spatial extent where local sources can influence the mineral dust budget on the ice sheet is fundamental for understanding the atmospheric dust cycle in Antarctica and for the interpretation of the dust history in marginal glaciological settings. In this work we investigate the spatial variability of dust flux and provenance during modern (pre-industrial) and Holocene times along a transect connecting Talos Dome to the internal sites of the Antarctic plateau and we extend the existing documentation of the isotopic (Sr-Nd) fingerprint of dust-sized sediments from Victoria Land source areas. Dust flux, grain size and isotopic composition show a marked variability between Talos Dome, Mid Point, D4 and Dome C/Vostok, suggesting that local sources play an important role on the periphery of the ice sheet. Microscope observations reveal that background mineral aerosol in the TALDICE core is composed by a mixture of dust, volcanic particles and micrometric-sized fragments of diatoms, these latter representing a small but pervasive component of Antarctic sediments. A set of samples from Victoria Land, mostly consisting of regolith and glacial deposits from high-elevation areas, was collected specially for this work and the isotopic composition of the dust-sized fraction of samples was analyzed. Results reveal a close relationship with the

  13. A 1400-year terrigenous dust record on a coral island in South China Sea

    PubMed Central

    Liu, Yi; Sun, Liguang; Zhou, Xin; Luo, Yuhan; Huang, Wen; Yang, Chengyun; Wang, Yuhong; Huang, Tao

    2014-01-01

    We present analyses of a lacustrine sediment core (DY6) on Dongdao Island, which provides high-resolution paleoclimate records for the South China Sea (SCS). Results of element analyses indicate that the concentrations of Ti and Al in DY6 are much higher than the background on the island. Morphological characteristics of acidic insoluble particles are similar to aeolian in East China. Sr and Nd isotope compositions in these particles are consistent with those in Asian aeolian dust. We inferred that dust in DY6 may have been transported by East Asian Winter Monsoon (EAWM) from inland Asia. The continuous dust records for the past 1400 years in North SCS were presented based on the measured Ti flux, which revealed an opposite trend to the variations in the EAWM for the past 50 years. A comparison of wind fields between cold and warm years shows that north surface wind in southeast China was stronger in cold years. However, 850 hPa wind vector along the east coast of China, the key level of wind for long-distance dust transmission, weakened in cold years. We conclude that differences in the EAWM records can be attributed to the 850 hPa wind pattern in different areas. PMID:24845372

  14. A 1400-year terrigenous dust record on a coral island in South China Sea

    NASA Astrophysics Data System (ADS)

    Liu, Yi; Sun, Liguang; Zhou, Xin; Luo, Yuhan; Huang, Wen; Yang, Chengyun; Wang, Yuhong; Huang, Tao

    2014-05-01

    We present analyses of a lacustrine sediment core (DY6) on Dongdao Island, which provides high-resolution paleoclimate records for the South China Sea (SCS). Results of element analyses indicate that the concentrations of Ti and Al in DY6 are much higher than the background on the island. Morphological characteristics of acidic insoluble particles are similar to aeolian in East China. Sr and Nd isotope compositions in these particles are consistent with those in Asian aeolian dust. We inferred that dust in DY6 may have been transported by East Asian Winter Monsoon (EAWM) from inland Asia. The continuous dust records for the past 1400 years in North SCS were presented based on the measured Ti flux, which revealed an opposite trend to the variations in the EAWM for the past 50 years. A comparison of wind fields between cold and warm years shows that north surface wind in southeast China was stronger in cold years. However, 850 hPa wind vector along the east coast of China, the key level of wind for long-distance dust transmission, weakened in cold years. We conclude that differences in the EAWM records can be attributed to the 850 hPa wind pattern in different areas.

  15. A 1400-year terrigenous dust record on a coral island in South China Sea.

    PubMed

    Liu, Yi; Sun, Liguang; Zhou, Xin; Luo, Yuhan; Huang, Wen; Yang, Chengyun; Wang, Yuhong; Huang, Tao

    2014-01-01

    We present analyses of a lacustrine sediment core (DY6) on Dongdao Island, which provides high-resolution paleoclimate records for the South China Sea (SCS). Results of element analyses indicate that the concentrations of Ti and Al in DY6 are much higher than the background on the island. Morphological characteristics of acidic insoluble particles are similar to aeolian in East China. Sr and Nd isotope compositions in these particles are consistent with those in Asian aeolian dust. We inferred that dust in DY6 may have been transported by East Asian Winter Monsoon (EAWM) from inland Asia. The continuous dust records for the past 1400 years in North SCS were presented based on the measured Ti flux, which revealed an opposite trend to the variations in the EAWM for the past 50 years. A comparison of wind fields between cold and warm years shows that north surface wind in southeast China was stronger in cold years. However, 850 hPa wind vector along the east coast of China, the key level of wind for long-distance dust transmission, weakened in cold years. We conclude that differences in the EAWM records can be attributed to the 850 hPa wind pattern in different areas.

  16. Peat bog Records of Atmospheric Dust fluxes - Holocene palaeoenvironmental and paleoclimatic implications for South America

    NASA Astrophysics Data System (ADS)

    De Vleeschouwer, François; Vanneste, Heleen; Bertrand, Sébastien; Coronata, Andrea; Gaiero, Diego; Le Roux, Gael

    2013-04-01

    Little attention has been given to pre-anthropogenic signals recorded in peat bogs, especially in the Southern Hemisphere. Yet they are important to 1/ better understand the different particle sources during the Holocene and 2/ to tackle the linkage between atmospheric dust loads and climate change and 3/ to better understand the impact of dust on Holocene palaeoclimate and palaeoenvironments in a critical area for ocean productivity. In the PARAD project, we will explore the use of a broad range of trace elements and radiogenic isotopes (Pb, Nd, Hf) as dust proxies. Coupling these findings with biological proxies (plant macrofossils, pollen) and detailed age-depth modelling, we expect not only to identify and interpret new links between atmospheric dust chemistry and climate change. In this contribution, we will present the preliminary results on two peat records of natural atmospheric dust using the elemental and isotopic signature in Tierra del Fuego. Preliminary results on two peat sections covering the Holocene (Karukinka Bog, Chile, 8kyrs and Harberton bog, Argentina, 14kyrs) will be discussed. This encompasses density, ash content, elemental and isotopic geochemistry, macrofossil determination and radiocarbon dating. More specifically, Karukinka bog display several mineral peaks, which possible origin (soil particles, volcanism, cosmogenic dusts, marine aerosols…) will be discussed here as well as in Vanneste et al. (this conference, session Aeolian dust: Initiator, Player, and Recorder of Environmental Change).

  17. Using Peatlands as Archives of Dust Deposition: A Preliminary Record from Southern Sweden

    NASA Astrophysics Data System (ADS)

    Kylander, Malin; Potucek, Martina; Bindler, Richard; Wohlfarth, Barbara

    2010-05-01

    means to quantify dust deposition as well as make a first attempt at source tracing of the deposited materials; this is important in terms of reconstructing changes in paleo wind regimes. Past variations in aeolian activity in Scandinavia are relatively unknown. Dune building records from Denmark and elsewhere around Europe show several periods of inland sand invasion and dune building during the Holocene. These are linked to cooler and stormier climates caused by shifts in the North Atlantic Oscillation and/or movement of the polar front. We compare the dust deposition record from Store Mosse with available dune building records and records of storminess from the region in order to make a preliminary assessment of the use of peatlands as paleo records of dust deposition.

  18. Magnetic characteristics of aeolian and fluvial sediments and onset of dust accumulation at Lake Yoa (northern Chad) during the Holocene

    NASA Astrophysics Data System (ADS)

    Just, Janna; Kröpelin, Stefan; Karls, Jens; Rethemeyer, Janet; Melles, Martin

    2014-05-01

    The Holocene is a period of fundamental climatic change in North Africa. Humid conditions during the Holocene Humid Period have favored the formation of big lake systems (e.g. Lake Megachad) and are evident in terrestrial and marine archives. Only very few of these lakes persist until today. One of them is Lake Yoa (19°03'N/20°31'E) in the Ounianga Basin, Chad, which maintains its water level by ground water inflow. Here we present the magnetic characteristics of a continuous 16 m long sediment record (Co1240) from Lake Yoa, retrieved in 2010 within the framework of the Collaborative Research Centre 806 - Our Way to Europe (Deutsche Forschungsgemeinschaft). The sedimentary section covers the past 11,000 years. In an earlier core (Kröpelin et al. 2008), a humid climate during the Mid-Holocene is indicated by fresh-water conditions in the lake. At about 4,000 cal. years BP, a fresh-to-saline transition is reflected in the record. However, a major rise in magnetic susceptibility, interpreted as an increase in the accumulation of wind-blown material, is only visible after 3,000 cal. years BP. Beyond using the concentration of magnetic minerals (susceptibility), environmental magnetic proxies, e.g. magnetic grain size and the composition of the magnetic mineral fabric, are often used as paleoenvironmental indicators. The underlying assumption is that the formation of magnetic minerals during pedogenesis is catalyzed by precipitation and soil-temperature. The application of magnetic proxies as reliable climofunctions has, however, recently been challenged. Possible problems are that soil formation might not reach an equilibrium state if climate perturbations are too short (e.g. hundreds of years) or that other variables such as soil organic carbon and vegetation have varied. In this study, we will focus on the variability of magnetic parameters in Lake Yoa sediments and its implication for the regional environmental development throughout Holocene times. 400 discrete

  19. Patagonian and Antarctic dust as recorded in the sediments of Laguna Potrok Aike (Patagonia, Argentina)

    NASA Astrophysics Data System (ADS)

    Haberzettl, Torsten; Stopp, Annemarie; Lisé-Pronovost, Agathe; Gebhardt, Catalina; Ohlendorf, Christian; Zolitschka, Bernd; von Eynatten, Hilmar; Kleinhanns, Ilka; Pasado Science Team

    2010-05-01

    Although an increasing number of terrestrial paleoclimatic records from southern South America has been published during the last decade, these archives mostly cover the Lateglacial and/or the Holocene. Only little is known about the Patagonian climate before the Last Glacial Maximum. Here, we present a continuous, high-resolution magnetic susceptibility record for the past 48 ka from the maar lake Laguna Potrok Aike (51°58' S, 70°23' W, southern Patagonia, Argentina). Magnetic susceptibility serves as an excellent parameter for the parallelization of sediment cores all over Laguna Potrok Aike including sediment cores taken within the ICDP (International Continental Scientific Drilling Program) project PASADO (Potrok Aike maar lake Sediment Archive Drilling prOject). Additionally, magnetic susceptibility is assumed to be a proxy for dust deposition in this lake. Distinct similarities were found between the independently dated magnetic susceptibility record from Laguna Potrok Aike and the non-sea-salt calcium (nss-Ca) flux from the EPICA Dome C ice core record (75°06'S, 123°24'E) the latter being a proxy for mineral dust deposition in Antarctica [1]. Comparison of the two records and variations in grain size of the Laguna Potrok Aike sediment records indicate a relatively high aeolian activity in southern South America during the glacial period. During the Holocene climatic conditions driving sediment deposition seem to have been more variable and less dominated by wind compared to glacial times. Although the source of the dust found in Antarctic ice cores often has been attributed to Patagonia [2], we present the first evidence for contemporaneity of aeolian deposition in both the target area (Antarctica) and the major source area (Patagonia). Considering the similarities of the two records, magnetic susceptibility might yield the potential for chronological information: transfer of the ice core age model to a lacustrine sediment record. This would be important

  20. The Dynamics and Characteristics of Aeolian Dust in Dryland Central Asia: Possible Impacts on Respiratory Health in the Aral Sea Basin

    NASA Astrophysics Data System (ADS)

    Wiggs, G. F.; O'Hara, S.; Wegerdt, J.; van der Meer, J.; Small, I.; Hubbard, R.

    2003-12-01

    Over the last 40 years over 36,000 km2 of the former Aral Sea bed have been exposed creating a potentially significant aeolian dust source. It is widely believed, but little researched, that increased dust storm activity in the region has had a major impact on human health. In this paper we report the findings of a study into the link between dust exposure and respiratory health amongst children in the Autonomous Republic of Karakalpakstan, located on the southern shore of the Aral Sea. Data were collected over a 12 month period at 16 sites located within a broad transect running north to south through Karakalpakstan. At each site monthly measurements of dust deposition were undertaken linked with daily meteorological data at 6 stations. At 3 sites weekly measurements of PM10 were also carried out. Approximately 100 children (aged 7-10 years) were randomly selected within 5 km of each dust trap site and data were collected on their respiratory health and environmental exposures. Lung function data were also collected using a handheld spirometer. A linear regression model was used to predict lung function for the children incorporating variables for Forced Expiratory Volume in one second (FEV1), age, gender, height and weight and we estimated the impact of dust deposition rates on the odds of having abnormal lung function using logistic regression. The findings indicate that dust deposition rates across the region are high with sites located near the former shore of the sea being the worst affected. For these northerly regions the former Aral Sea bed is the most likely source of dust. The situation for the rest of the country seems to be far more complex. In these regions it appears that local sources (agricultural fields, abandoned irrigation grounds, overgrazed dunes, and unpaved roads) and more distant sources to the south and south-west represent significant sediment providers, particularly in the early summer when agricultural fields are ploughed. We found some

  1. Aeolian sediment and dust fluxes during predominant “background” wind conditions for unburned and burned semiarid grassland: Interplay between particle size and temporal scale

    NASA Astrophysics Data System (ADS)

    Merino-Martín, Luis; Field, Jason P.; Villegas, Juan Camilo; Whicker, Jeffrey J.; Breshears, David D.; Law, Darin J.; Urgeghe, Anna M.

    2014-09-01

    Monitoring of aeolian transport is needed for assessment and management of human health risks as well as for soil resources. Human health risks are assessed based on duration of exposure as well as concentration. Many aeolian studies focus on periods of high wind speed when concentrations are greatest but few studies focus on “background” conditions when concentrations are likely lower but which represent the most prevalent conditions. Such “background” conditions might be especially important at sites with recent disturbance such as fire. Exposure assessments also require improved understanding relating longer-term (days to weeks) measurements of saltation of larger particles to shorter-term (minutes to hours) measurements of smaller inhalable dust particles. To address these issues, we employed three commonly used instruments for measuring dust emissions for unburned and recently-burned sites: Big Springs Number Eight (BSNE) samplers for larger saltating soil particles (>50 μm) with weekly to monthly sampling resolution, DustTraks for suspended particles (diameters <10 μm) with 1-s sampling resolution, and Total Suspended Particulate (TSP) filter samplers for measuring with hourly to daily sampling resolution. Significant differences in concentrations between burned and unburned sites were detectable in either short (1-s maximum) interval DustTrak PM10 measurements, or in longer term (weekly) BSNE horizontal sediment flux measurements, but not in intermediate-term (daily 5-h means) for either DustTrak PM10 or TSP measurements. The results highlight ongoing dust emissions during less windy periods and provide insight into the complex interplay among particle-size dependent measures and typical time scales measured.

  2. Composition of aeolian dust in natural traps on isolated surfaces of the central Mojave Desert - Insights to mixing, sources, and nutrient inputs

    USGS Publications Warehouse

    Reynolds, R.L.; Reheis, M.; Yount, J.; Lamothe, P.

    2006-01-01

    The recognition and characterization of aeolian dust in soil contribute to a better understanding of landscape and ecosystem dynamics of drylands. Results of this study show that recently deposited dust, sampled in isolated, mostly high-ground settings, is chemically and mineralogically similar on varied geologic substrates over a large area (15 000 km2) in the Mojave Desert. The silt-plus-clay fraction (fines) on these isolated surfaces is closely alike in magnetic-mineral composition, in contrast to greatly dissimilar magnetic compositions of rock surfaces of vastly different lithologies, on which the fines have accumulated. The fines, thus, are predominantly deposited dust. The amounts of potential nutrients in the sampled dust are much more uniform than might be provided by direct, local weathering of bedrock or by dust locally derived from nearby weathered products. The compositional similarity of the dust on these surfaces is interpreted to result from mixing of fines in the atmosphere as well as in fluvial, alluvial, and lacustrine depositional settings prior to dust emission.

  3. Contemporary research in aeolian geomorphology

    NASA Astrophysics Data System (ADS)

    Bauer, B. O.

    2009-04-01

    The first International Conference on Aeolian Geomorphology (ICAR) was held in 1986, and every four years since then, aeolian geomorphologists from around the world have assembled to discuss their research and to showcase recent advancements in understanding and modeling of aeolian processes. A content analysis of the "Bibliography of Aeolian Research" [Stout, J.E., Warren, A., Gill, T.E., 2009. Publication trends in aeolian research: An analysis of the Bibliography of Aeolian Research. Geomorphology 105, 6-17 (this volume)] shows that the number of publications on aeolian topics has increased exponentially from the mid-20th Century with approximately 50 publications per year to about 500 publications per year when the first ICAR was held, to almost 1000 publications per year currently. Areas of focus have shifted historically from initial concerns with aeolian erosion and dust events as isolated phenomenon of localized curiosity or only regional importance, to comprehensive physically-based investigations and modeling of the mechanics of aeolian transport. Recently, more applied studies have been motivated by the recognition of the importance of aeolian processes to dust emissions into the atmosphere (with relevance for human health and for meteorological conditions and climate change) and within regional management contexts (especially on coasts where impending sea-level rise is of great concern and in arid and semi-arid environments given the dependence of sediment surface stability and remobilization on meteorological and ecological conditions). Aeolian geomorphology is a rapidly growing sub-discipline of Geomorphology that offers rich opportunities for interdisciplinary collaborations with colleagues from the Atmospheric Sciences, Climatology, Sedimentology, Quaternary Geology, Fluid Mechanics, Physics, Mathematics, Computer Science, Physical Geography, Ecology, and Agricultural Sciences, as well as our counterparts in fluvial, coastal, and arid

  4. Geographic provenance of aeolian dust in East Antarctica during Pleistocene glaciations: preliminary results from Talos Dome and comparison with East Antarctic and new Andean ice core data

    NASA Astrophysics Data System (ADS)

    Delmonte, B.; Andersson, P. S.; Schöberg, H.; Hansson, M.; Petit, J. R.; Delmas, R.; Gaiero, D. M.; Maggi, V.; Frezzotti, M.

    2010-01-01

    The strontium and neodymium isotopic signature of aeolian mineral particles archived in polar ice cores provides constraints on the geographic provenance of dust and paleo-atmospheric circulation patterns. Data from different ice cores drilled in the centre of the East Antarctic plateau such as EPICA-Dome C (EDC, 75°06'S; 123°21'E) and Vostok (78°28'S, 106°48'E) suggested a uniform geographic provenance for dust during Pleistocene glacial ages, likely from southern South America (SSA). In this work the existing dust isotopic data from EDC have been integrated with new data from Marine Isotopic Stage (MIS) 14 (about 536 ka before 1950AD) and in parallel some first results are shown for the new TALDICE ice core which was drilled on the edge of the East Antarctic Plateau (Talos Dome, 72°48'S, 159°06'E) on the opposite side with respect to SSA. Interestingly, the isotopic composition of TALDICE glacial dust is remarkably similar to that obtained from glacial dust from sites located in the East Antarctic interior. Overall, the glacial dust isotopic field obtained from six East Antarctic ice cores matches well South American data obtained from target areas. In this respect, it was recently suggested that dust exported long-range from South America originates from Patagonia and from the Puna-Altiplano plateau. To test this hypothesis, we analysed the isotopic composition of dust from an ice core drilled on the Illimani glacier (Bolivia, 16°37'S, 67°46'W; 6350 m a.s.l.) in order to obtain information on the isotopic composition of regional mineral aerosol uplifted from the Altiplano area and likely transported over a long distance. Altogether, ice core and source data strongly suggest that the westerly circulation pattern allowed efficient transfer of dust from South America to the East Antarctic plateau under cold Quaternary climates. Isotopic data support the hypothesis of a possible mixing of dust from Patagonia and from the Puna-Altiplano plateau. Interestingly

  5. Late Holocene interdecadal climate variability in the Sahel: inferences from a marine dust record offshore Senegal

    NASA Astrophysics Data System (ADS)

    Meyer, I.; Stuut, J.-B.; Mollenhauer, G.; Mulitza, S.; Zabel, M.

    2009-04-01

    Present-day climate in northwestern Africa strongly depends on the avaiability of water. At least since the Pliocene the Saharan Desert and the semiarid Sahel belt (tropical North Afrika) have been frequently affected by sudden shifts to more arid climate. The rate of change from arid to humid conditions is presently under heavy debate (e.g., deMenocal et al., 2001, Kröpelin et al., 2008). A recent example of abrupt droughts occurred in the early 70's and 80's of the last century. In this study we compare different high-resolution marine sediment records of Sahel climate variability from the Senegal mud belt, northwest Africa. Marine sediment cores show the variations of terrigenous input (both aeolian dust and fluvial matter) from the African continent. Due to their different distinctive grain-size distributions, aeolian dust and fluvial mud can be recognised and quantified in marine sediments (e.g., Stuut et al., 2002). Based on these variations in the grain-size distributions of the terrigenous sediment fraction, deconvolved with an end-member modelling algorithm (Weltje, 1997), are used to reconstruct rainfall variability and dust production on land for the last 4,000 years. References P. B. deMenocal, et al. (2001). Late Holocene Cultural Responses to Climate Change During the Holocene. Science 292, 667 S. Kröpelin, et al. (2008) Response to Comment on "Climate-Driven Ecosystem Succession in the Sahara: The Past 6000 Years" Science 322, 1326c G. J. Weltje (1997) End-member modeling of compositional data: Numerical-statistical algorithms for solving the explicit mixing problem. Mathematical Geology 9, 4

  6. Aeolian bedforms, yardangs, and indurated surfaces in the Tharsis Montes as seen by the HiRISE Camera: Evidence for dust aggregates

    USGS Publications Warehouse

    Bridges, N.T.; Banks, M.E.; Beyer, R.A.; Chuang, F.C.; Noe Dobrea, E.Z.; Herkenhoff, K. E.; Keszthelyi, L.P.; Fishbaugh, K.E.; McEwen, A.S.; Michaels, T.I.; Thomson, B.J.; Wray, J.J.

    2010-01-01

    HiRISE images of Mars with ground sampling down to 25 cm/pixel show that the dust-rich mantle covering the surfaces of the Tharsis Montes is organized into ridges whose form and distribution are consistent with formation by aeolian saltation. Other dusty areas near the volcanoes and elsewhere on the planet exhibit a similar morphology. The material composing these "reticulate" bedforms is constrained by their remote sensing properties and the threshold curve combined with the saltation/suspension boundary, both of which vary as a function of elevation (atmospheric pressure), particle size, and particle composition. Considering all of these factors, dust aggregates are the most likely material composing these bedforms. We propose that airfall dust on and near the volcanoes aggregates in situ over time, maybe due to electrostatic charging followed by cementation by salts. The aggregates eventually reach a particle size at which saltation is possible. Aggregates on the flanks are transported downslope by katabatic winds and form linear and "accordion" morphologies. Materials within the calderas and other depressions remain trapped and are subjected to multidirectional winds, forming an interlinked "honeycomb" texture. In many places on and near the volcanoes, light-toned, low thermal inertia yardangs and indurated surfaces are present. These may represent "duststone" formed when aggregates reach a particle size below the threshold curve, such that they become stabilized and subsequently undergo cementation. ?? 2009 Elsevier Inc.

  7. Late Pleistocene aeolian dust provenances and wind direction changes reconstructed by heavy mineral analysis of the sediments of the Dehner dry maar (Eifel Mountains, Germany)

    NASA Astrophysics Data System (ADS)

    Lehmkuhl, Frank; Römer, Wolfgang; Sirocko, Frank

    2016-04-01

    The study presents the results of a heavy mineral analysis from a 38 m long record of aeolian sediments from a core section of the Dehner dry maar (Eifel Mountains, Germany). The record encompasses the period from 30 to about 12.5 ka. Heavy-mineral analysis of the silt fraction has been performed at a sampling interval of 1 m. Statistical analyses enabled the distinction of local and regional source areas of aeolian material and revealed pronounced changes in the amounts of different heavy mineral species and corresponding changes in the grain size index (GSI). The results indicate that during the early stages of MIS 2 (40 to 30m depth) aeolian sediments were supplied mostly from local sources. This period is characterized by a low GSI ratio resulting from a reduced mobility of material due to a vegetation cover. The climax of the LGM is characterized by a higher supply of heavy minerals from regional and more distant sources. Changes in the provenance areas are indicated in inverse relationships between zircon, rutile, tourmaline (ZRT) and carbonate particles. Shifts in the wind direction are documented in pronounced peaks of carbonate particles indicating easterly winds that have crossed the limestone basins in the Eifeler North South Zone. ZRT-group minerals on the other hand suggest a westerly source area and a supply from areas consisting of Paleozoic clastic sedimentary rocks. In the periods following the LGM the analyses indicate an increasing degree of mixing of heavy minerals from various provinces. This suggests the existence of a presumably incomplete, thin cover of deflatable loessic sediments that has been repeatedly reworked on the elevated surfaces of the Eifel.

  8. Palaeoclimatic considerations of talus flatirons and aeolian deposits in Northern Fuerteventura volcanic island (Canary Islands, Spain)

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Elorza, Mateo; Lucha, Pedro; Gracia, F.-Javier; Desir, Gloria; Marín, Cinta; Petit-Maire, Nicole

    2013-09-01

    Fuerteventura volcanic island has been subject to considerable aeolian activity since the Late Pleistocene. The aeolian record includes inactive aeolian deposits with interbedded entisols, whose age by OSL dating ranges between 46 and 26 ky BP. The Corralejo active dune field, where sand sheets, nebkhas, coppice dunes, blowouts, barchans and transverse dunes have been described, constitutes a more recent Aeolian deposit. Here the age is about 14 ky BP. On Fuerteventura Island aeolian dust has been deposited on valleys and slopes. This last type of accumulation has been affected by gully incision, producing talus flatirons. Samples taken on the apex of these palaeo-slopes indicate an OSL age of 30 and 50 ky BP. A palaeoclimatic succession has been interpreted during which a prevailing arid period took place in OIS 4, with the accumulation of aeolian dust. A humid period occurred in OIS 2, during which slopes were dissected and formed talus flatirons. An arid period about 14 ky BP gave rise to the Corralejo dune field, which has continued until present with slight climatic oscillations.

  9. Studies in Martian Aeolian Geology

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald

    2001-01-01

    This report gives the results from the investigation through March 15, 1999 for the first two years of the three year investigation (year 3 runs from March 1, 1999 to February 27, 2000). The investigation included three tasks, all involving windblown dust (particles a few micrometers in diameter) to simulate the aeolian regime on Mars. Experiments were conducted primarily in the Mars Surface Wind Tunnel (MARSWIT) at NASA-Ames Research Center.

  10. A rock-magnetic study of coral skeletons: A record of African dust deposition in the Caribbean

    NASA Astrophysics Data System (ADS)

    Nigro, P. M.; Clement, B. M.; Halley, R.; Helmle, K.; Swart, P.; Dodge, R.

    2008-05-01

    Aeolian African dust from the Saharan-Sahel deserts significantly influences the climate and ecology of the Caribbean region. Large summer dust storms produce mass quantities of air-born, clay-rich material (containing significant iron-oxide components), that are transported over the Atlantic Ocean and deposited in the Caribbean. We present here the results of a rock magnetic study of cores of Scleractinian corals, including a Montastraea annularis collected in Culebra, Puerto Rico on July of 1991, a M. faveolata collected off the coast of St. Vincent (Bequia) on November of 2002, and a Siderastrea radians collected off the coast of Cape Verde on July of 2002. Thin slabs (~5mm) were cut from these cores and x-rayed to reveal annual density banding. Small samples centered over each annual high-density band were cut from the slabs. These samples were then subjected to a series of standard rock magnetic experiments, including Anhysteretic Remanent Magnetization (ARM) acquisition and demagnetization, and Isothermal Remanent Magnetization (IRM) acquisition and demagnetization. Records of both ARMs and IRMs reveal coherent signals that vary with coral age. The IRM acquisition curves demonstrate the presence of two carriers of magnetization in most samples; a low-coercivity component consistent with the presence of magnetite or maghemite and a high-coercivity component consistent with the presence of hematite. Unmixing the IRM acquisition curves differentiates the magnetic components and yields a record of high-coercivity input that we interpret as a record of African dust. Preliminary data from the M. annularis core show a link between high and low variability in the high-coercivity component when compared with the historical record of dust flux to the Caribbean and with the Soudano-Sahel Precipitation Index (SSPI) over a time period of fifty years (1941-1990). High variability is displayed from 1941 through 1950 and 1965 through 1990 whereas low variability is displayed

  11. Aeolian geomorphology from the global perspective

    NASA Technical Reports Server (NTRS)

    Greeley, R.

    1985-01-01

    Any planet or satellite having a dynamic atmosphere and a solid surface has the potential for experiencing aeolian (wind) processes. A survey of the Solar System shows at least four planetary objects which potentially meet these criteria: Earth, Mars, Venus, and possibly Titan, the largest satellite of Saturn. While the basic process is the same among these four objects, the movement of particles by the atmosphere, the aeolian environment is drastically different. It ranges from the hot (730 K), dense atmosphere of Venus to the extremely cold desert (218 K) environment of Mars where the atmospheric surface pressure is only approximately 7.5 mb. In considering aeolian processes in the planetary perspective, all three terrestrial planets share some common areas of attention for research, especially in regard to wind erosion and dust storms. Relevant properties of planetary objects potentially subject to aeolian processes are given in tabular form.

  12. Holocene aeolian sedimentation and episodic mass-wasting events recorded in lacustrine sediments on Langøya in Vesterålen, northern Norway

    NASA Astrophysics Data System (ADS)

    Nielsen, Pål Ringkjøb; Dahl, Svein Olaf; Jansen, Henrik Løseth; Støren, Eivind N.

    2016-09-01

    In this study, the frequency of mass-wasting events and past storminess has been reconstructed throughout the Holocene (11,500 cal yr BP to present) from lacustrine sediments in lake Trehynnvatnet (33 m a.s.l.), which is located in a glacially carved valley at Nykvåg on the outmost coast of western Langøya, Vesterålen, northern Norway. Sediment cores (∼2-5 m long) have been examined by use of high-resolution magnetic susceptibility and XRF-scanning as well as grain size and loss-on-ignition analysis. In total 35 episodic event layers have been identified throughout the Holocene. The majority of these events are characterized as discrete coarse-grained sediment layers followed by normal grading, and are related to past mass-wasting activity within the catchment. Periods with high mass-wasting activity are dated to 11,000-10,500, 5500-4500, 4000-3500, 3000-2500, 2000-1000 and 500-0 cal yr BP. The continuous input of sand grains (>250 μm) has been systematically investigated throughout the sediment cores. The sand grains are related to catchment samples from the sandy beach deposits in Sandvikbukta c. 750 m away in SW direction, and are suggested to indicate (niveo-) aeolian influx to the lake. The content of sand grains varies greatly throughout the record, although there is a clear increase in influx of sand during the last 2800 years. Periods with high aeolian influx are proposed to indicate increased storminess, which occurred between 1600 and 1550 (350-400 CE), 1400-1300 (450-550 CE), 750-550 (1200-1400 CE) and 250-20 cal yr BP (1700-1930 CE), which to some degree coincides with periods of increased storminess and winter precipitation recorded in other studies around the North Eastern Atlantic region.

  13. Persistent Aeolian Activity at Endeavour Crater, Mars

    NASA Astrophysics Data System (ADS)

    Chojnacki, M.; Michaels, T. I.; Fenton, L. K.

    2013-12-01

    Long-term monitoring of sites that are known to have active dunes and ripples is generally limited to 3 Mars-Years (MY). Here, we discuss new results of dune activity and albedo change in Endeavour crater (EC), Meridiani Planum (MP) that record eight MY of aeolian activity. MP dune fields often show large yearly variations in albedo; EC darkened by ~12% in TES albedo between MY 24 and 26 (from 0.14 to 0.12). THEMIS VIS albedo of dunes did not change significantly from MY 26 to 29, but did decrease notably (~15 %) in MY 30. These darkening events are most likely related to aeolian-driven dust cleaning (e.g., removal by saltating sand, dust devils). For example, the Opportunity rover (poised on the western rim of EC) observed evidence for a MY 31 dune field dust-clearing event. HiRISE monitoring of MP has shown it be one of the most active regions outside of north polar latitudes. Paired images of western EC taken 3 MY apart show clear evidence for dune modification that include: ripple migration, change in dune perimeters, exposure of previously buried light-toned rock, and/or burial of rock by sand (Fig. 1a-1b). Dune slip face movement is evident for most dunes, where crests and aprons advanced (2-7 m) in the downwind direction (to the SSE) at rates of 0.7-2.3 m per MY. Small dome dunes in the eastern EC were found to have a large degree of aeolian activity (e.g., deflation and/or translation) by an earlier study that used MGS-MRO images (MY 24-30). New MY 31 images validate earlier observations, showing clear evidence for bedform deflation where dunes often occupy less area (~50%) than in earlier MY 29 images (Fig. 1c-1d). Areal removal rates are on par with earlier estimates. Bedform modification and sand streamer orientation appear to be caused by a NNW wind regime, consistent with earlier observations, mesoscale modeling, and the transport direction of barchans to the west. Dunes in EC are now known to be periodically (consistently?) active from over a decade

  14. Publication trends in aeolian research: An analysis of the Bibliography of Aeolian Research

    NASA Astrophysics Data System (ADS)

    Stout, John E.; Warren, Andrew; Gill, Thomas E.

    2009-04-01

    An analysis of the Bibliography of Aeolian Research has provided information regarding publication trends in aeolian research. Results suggest that there has been a significant increase in the number of publications per year since the first aeolian-research publication appeared in 1646. Rates of publication have increased from only three publications in the 17th Century to nearly three publications per day in the 21st Century. The temporal distribution of publications follows a complex pattern that is influenced by many factors. In the 17th and 18th Centuries, publications appear as isolated clusters indicating limited interest in aeolian research and limited opportunities for individuals to contribute to scientific literature. With time, many new scientific societies are formed and many new scientific journals are established, opening new opportunities for scientists to contribute to scientific discourse. Landmark publications open up new research areas and define new directions for aeolian research. General advances in science and technology provide new techniques for sampling blowing sand and dust. In addition, clear signs exist that publication rates respond to major environmental and climatic events, especially large-scale disasters that focus attention on wind erosion and blowing dust. The Sirocco dust events of 1901-1903, the North American Dust Bowl of the1930s, and the recent sand and dust storm problems in China have all led to significant increases in the number of publications in aeolian research. Rates of publication are negatively influenced by major political and social upheavals, especially global conflicts such as World Wars I and II. Sudden shifts in government structure and support can also influence publication rates. A good example is the increased publication rates in China following the end of the Cultural Revolution, a trend that continues today.

  15. Towards a phoenix phase in aeolian research: shifting geophysical perspectives from fluvial dominance

    SciTech Connect

    Whicker, Jeffrey J; Field, Jason P; Breshears, David D

    2008-01-01

    Aeolian processes are a fundamental driver of earth surface dynamics, yet the importance of aeolian processes in a broader geosciences context may be overshadowed by an unbalanced emphasis on fluvial processes. Here we wish to highlight that aeolian and fluvial processes need to be considered in concert relative to total erosion and to potential interactions, that relative dominance and sensitivity to disturbance vary with mean annual precipitation, and that there are important scale-dependencies associated with aeolian-fluvial interactions. We build on previous literature to present relevant conceptual syntheses highlighting these issues. We then highlight the relative investments that have been made in aeolian research on dust emission and management relative to that in fluvial research on sediment production. Literature searches highlight that aeolian processes are greatly understudied relative to fluvial processes when considering total erosion in different environmental settings. Notably, within the USA, aeolian research was triggered by the Dust Bowl catastrophe of the 1930s, but the resultant research agencies have shifted to almost completely focusing on fluvial processes, based on number of remaining research stations and on monetary investments in control measures. However, numerous research issues associated with intensification of land use and climate change impacts require a rapid ramping up in aeolian research that improves information about aeolian processes relative to fluvial processes, which could herald a post-Dust Bowl Phoenix phase in which aeolian processes are recognized as broadly critical to geo- and environmental sciences.

  16. Robotic Measurement of Aeolian Processes

    NASA Astrophysics Data System (ADS)

    Roberts, S.; Duperret, J. M.; Jerolmack, D. J.; Lancaster, N.; Nikolich, G.; Shipley, T. F.; Van Pelt, R. S.; Zobeck, T. M.; Koditschek, D. E.

    2015-12-01

    Local and regional measurements of sand transport and dust emission in complex natural settings presently lack spatiotemporal resolution adequate to inform models relevant for land management, climate policy, and the basic science of geomorphology. Deployments of wind, sand and dust sensors sophisticated enough to begin unpacking the complex relations among wind turbulence, surface roughness, sand flux and dust emission remain largely stationary. Aerial observations from satellites, planes and even UAVs help fill in, but none of these modalities offer the hope of "capturing the action" by being at the right place at the right time relative to the highly localized nature of sediment transport during wind storms. We have been developing a legged robot capable of rapidly traversing desert terrain, and are now adapting it to serve as a platform for scientific instrumentation. We aim to field a semi-autonomous, reactive mobile sensory package suited to the needs of aeolian science that can address the limitations of existing alternatives. This presentation reports on early trials in the Jornada LTER and White Sands National Monument aimed at gathering measurements of airflow and rates of sand transport on a dune face, assessing the role of roughness elements such as vegetation in modifying the wind shear stresses incident on the surface, and estimating erosion susceptibility in a natural arid soil. We will solicit ideas from the audience about other potentially interesting and viable measurement targets. Future close collaboration between aeolian, cognitive and robotics scientists such as we hope to promote through this presentation may yield machines with scientifically relevant sensory suites possessing sufficient autonomy to operate in-situ at the most intense episodes of wind and sediment movement under conditions far too uncomfortable and hazardous for human presence.

  17. The north-eastern aeolian 'European Sand Belt' as potential record of environmental changes: A case study from Eastern Latvia and Southern Estonia

    NASA Astrophysics Data System (ADS)

    Kalińska-Nartiša, Edyta; Thiel, Christine; Nartišs, Māris; Buylaert, Jan-Pieter; Murray, Andrew S.

    2016-09-01

    The Latvian and Estonian inland dunes belong to the north-eastern part of the 'European Sand Belt' (ESB). These dunes are widely distributed over broad glaciolacustrine plains and Late Glacial alluvial deltas, considered to be potential sources for the aeolian material. Little is known about these aeolian sediments and their substratum; here we present a detailed sedimentary structural and textural characterisation together with a luminescence-based chronology. Through a comparison between grain-size, rounding of quartz grains and surface characteristics in medium/coarse (0.5-0.8 mm) sand, and the light mineral content, we found an alternation of aeolian and periglacial components. Further, short-lasting aeolian abrasion and/or transportation periods, and a significant contribution of a nearby sediment source are suggested. Luminescence dating points to aeolian sand accumulation and dune formation between ∼16 ka and ∼9 ka. However, we also observed some presumably watertable controlled environmental conditions at ∼13 ka; this corresponds with the occurrence of an ice-dammed/proglacial lake.

  18. Studies in Aeolian geology

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald

    1988-01-01

    The objective of the research was to assess the significance of aeolian (windblown) processes in the evolution of planetary surfaces. The approach was to use wind tunnel simulations, field studies of possible analogs, and analyses of spacecraft data.

  19. Observed particle sizes and fluxes of Aeolian sediment in the near surface layer during sand-dust storms in the Taklamakan Desert

    NASA Astrophysics Data System (ADS)

    Huo, Wen; He, Qing; Yang, Fan; Yang, Xinghua; Yang, Qing; Zhang, Fuyin; Mamtimin, Ali; Liu, Xinchun; Wang, Mingzhong; Zhao, Yong; Zhi, Xiefei

    2016-08-01

    Monitoring, modeling and predicting the formation and movement of dust storms across the global deserts has drawn great attention in recent decades. Nevertheless, the scarcity of real-time observations of the wind-driven emission, transport and deposition of dusts has severely impeded progress in this area. In this study, we report an observational analysis of sand-dust storm samples collected at seven vertical levels from an 80-m-high flux tower located in the hinterland of the great Taklamakan Desert for ten sand-dust storm events that occurred during 2008-2010. We analyzed the vertical distribution of sandstorm particle grain sizes and horizontal sand-dust sediment fluxes from the near surface up to 80 m high in this extremely harsh but highly representative environment. The results showed that the average sandstorm grain size was in the range of 70 to 85 μm. With the natural presence of sand dunes and valleys, the horizontal dust flux appeared to increase with height within the lower surface layer, but was almost invariant above 32 m. The average flux values varied within the range of 8 to 14 kg m-2 and the vertical distribution was dominated by the wind speed in the boundary layer. The dominant dust particle size was PM100 and below, which on average accounted for 60-80 % of the samples collected, with 0.9-2.5 % for PM0-2.5, 3.5-7.0 % for PM0-10, 5.0-14.0 % for PM0-20 and 20.0-40.0 % for PM0-50. The observations suggested that on average the sand-dust vertical flux potential is about 0.29 kg m-2 from the top of the 80 m tower to the upper planetary boundary layer and free atmosphere through the transport of particles smaller than PM20. Some of our results differed from previous measurements from other desert surfaces and laboratory wind-dust experiments, and therefore provide valuable observations to support further improvement of modeling of sandstorms across different natural environmental conditions.

  20. Geochemical investigation of dry- and wet-deposited dust during the same dust-storm event in Harbin, China: Constraint on provenance and implications for formation of aeolian loess

    NASA Astrophysics Data System (ADS)

    Xie, Yuanyun; Chi, Yunping

    2016-04-01

    A strong dust-storm event occurred in Harbin, China on May 11, 2011. The dry- and wet-deposited dust depositions in this dust-storm event, together with the surface sediments from the potential sources, were collected to study grain size distributions, carbonate content and carbon isotopic composition of carbonate, major element, trace element and rare earth elements (REE), and Sr-Nd isotopic compositions. The results indicate as follows. The dry-deposited dusts are characterized by bimodal grain-size distributions with a fine mode at 3.6 μm and a coarse mode at 28 μm whereas the wet-deposited dusts are indicative of unimodal grain-size modes with a fine mode at 6 μm. The dust-storm depositions are influenced to a certain extent by sedimentary sorting and are of a derivation from the recycled sediments. Based on identifying the immobility of element pairs before constraining sources of dust-storm deposits using geochemical elements, in conjunction with REE and especially Sr-Nd isotopic compositions, the primary and strengthening sources for the dust-storm event were detected, respectively. The Hunsandake Sandy Land as the primary source and the Horqin Sandy Land as the strengthening source were together responsible for the derivation of dust depositions during dust-storm event. The Hunsandake Sandy Land, however, contributes less dust to the dust-storm event in Harbin compared to the Horqin Sandy Land, and the Hulun Buir Sandy Land is undoubtedly excluded from being one of the sources for dust-storm depositions in Harbin. There are not notable differences in geochemical (especially Sr-Nd isotopic) compositions between dry- and wet-deposited dusts, indicating that the wet-deposited dust is of identical derivation to the dry-deposited dust. Based on our observations, it is of interest to suggest that fine and coarse particles in the CLP (Chinese Loess Plateau) loess possibly have the same sources.

  1. Comparing the Epica and Vostok dust records during the last 220,000 years: stratigraphical correlation and provenance in glacial periods

    NASA Astrophysics Data System (ADS)

    Delmonte, B.; Basile-Doelsch, I.; Petit, J.-R.; Maggi, V.; Revel-Rolland, M.; Michard, A.; Jagoutz, E.; Grousset, F.

    2004-06-01

    A new aeolian dust record from the first 2200 m of the EPICA-Dome C ice core (75°06'S, 123°21'E) covering about 220,000 years of climatic history is compared to the Vostok (78°28'S, 106°48'E) ice core [Nature 399 (1999) 429]. The two dust profiles are very similar and several common dust events allow to establish stratigraphical links. The late Quaternary period is characterized at both sites, and likely overall East Antarctic plateau, by high dust input during glacial periods. In the EPICA-Dome C ice core, the dust flux rises by a factor of ˜25, ˜20 and ˜12 in glacial stages 2, 4 and 6 with respect to interglacial periods (Holocene and stage 5.5). The magnitude and pattern of changes are comparable in the Vostok ice core. In this study, the geographical origin of ice core dust (ICD) in cold periods has been investigated at both sites through 87Sr/ 86Sr versus 143Nd/ 144Nd isotopic tracers, following the previous studies of Grousset et al. [Earth Planet. Sci. Lett. 111 (1992) 175] and Basile et al. [Earth Planet. Sci. Lett. 146 (1997) 573]. The new data and the existing ones allow to define the isotopic fields for dust at the two Antarctic sites that are almost identical and restricted into the 0.708< 87Sr/ 86Sr<0.711 and -5< ɛNd(0)<+5 ranges. This suggests a common geographical provenance for dust at Vostok and Dome C and for all the glacial periods of the late Pleistocene. To decipher the ICD provenance, more than 50 samples of loess and aeolian deposits, sands and fluvioglacial sediments from the Potential Source Areas (PSAs) of the Southern Hemisphere have been collected. However, the methodology has been refined with respect to former studies. First, the isotopic fractionation that can occur in function of grain size has been taken into account, and the PSA's signature has been defined in the <5 μm size range, within which fine-grained dust reaching Antarctica is found. Moreover, a possible contribution from carbonates on the samples from PSAs has

  2. Holocene dust records from the West African Sahel and their implications for changes in climate and land surface conditions

    NASA Astrophysics Data System (ADS)

    Cockerton, Helen E.; Holmes, Jonathan A.; Street-Perrott, F. Alayne; Ficken, Katherine J.

    2014-07-01

    We reconstructed aeolian dust accumulation during the Holocene from two radiocarbon-dated lake-sediment sequences from the Manga Grasslands in northeastern Nigeria in order to investigate long-term changes in the Harmattan dust system over West Africa and evaluate their possible causes. Flux values were low in the early Holocene, decreasing further to a minimum at around 6.2 kyr B.P. after which time they increased, steadily until around 2 kyr B.P. and then more sharply after this time. The long-term variations in dust flux agree broadly with changes in the exposed area of the Lake Chad Basin to the northeast of the study sites, which vary inversely with the volume of Paleolake Megachad. More proximal sources of dust, including the fine fraction of local dune sand and floodplains of nearby rivers, have also made a contribution to the total dust load during times of enhanced dune and fluvial activity. Sharp rises in dust flux over the past century may be related to human activity. Broad patterns of change in dust flux during the Holocene agree with other reconstructions over the same period. However, we see no evidence for a stepped rise during the middle Holocene, as seen at some sites from the northeastern tropical Atlantic, suggesting that controls on the Harmattan dust system have differed from those affecting dust deposition elsewhere across northern Africa.

  3. MECA Worksop on Dust on Mars 2

    NASA Technical Reports Server (NTRS)

    Lee, Steven (Editor)

    1986-01-01

    Topics addressed include: sedimentary debris; mineralogy; Martian dust cycles; Mariner 9 mission; Viking observations; Mars Observer; atmospheric circulation; aeolian features; aerosols; and landslides.

  4. Mega-ripples in Iran: A new analog for transverse aeolian ridges on Mars

    NASA Astrophysics Data System (ADS)

    Foroutan, M.; Zimbelman, J. R.

    2016-08-01

    A new terrestrial analog site for transverse aeolian ridges (TARs) is described in this study. The Lut desert of Iran hosts large ripple-like aeolian bedforms, with the same horizontal length scales and patterns of TARs on Mars. Different classes of TARs and different types of other aeolian features such as sand dunes, zibars, dust devil tracks and yardangs can be found in this area, which signify an active aeolian region. This area represents a unique site to study the formation and evolution of these enigmatic features, with potential relevance toward a better understanding of TARs on Mars.

  5. Abrupt Climate Events Recorded in Chinese and Central Asian Loess Sequences

    NASA Astrophysics Data System (ADS)

    Machalett, B.; Oches, E. A.; Haam, E. K.; Lai, Z.; Endlicher, W.

    2013-12-01

    Past climate dynamics associated with the Eurasian continent have been extensively studied. However, the impact of intra-hemispheric-scale climate variability on the entire Eurasian landmass, as well as the self-generated effects of the continent on the global climate system, is still a matter of investigation . While western Atlantic polar and tropical air masses penetrate into the continent and are transformed as they cross Eurasia, the interior regions of Eurasia strongly influence Earth's climate system. Significant cooling and heating of Central and High Asia drive interactions between atmospheric and oceanic processes and regulate teleconnection patterns across the Northern Hemisphere. This paper utilizes high resolution particle size data from the Central Asian loess sequence at Remisowka, Kazakhstan, and the long studied, monsoon-influenced Chinese loess sequence at Xifeng, to reconstruct past atmospheric circulation and aeolian dust dynamics within interior Eurasia since the last interglacial period. The observed dynamics in aeolian dust transport closely mirror d18O and fine dust variations measured in Greenland ice cores, suggesting a correlation with short-term climate oscillations (DO events) recorded therein. An Asian origin of fine aeolian dust preserved in Greenland ice cores has been discussed previously, and recent papers reveal a close link between Asian aeolian dust dynamics and DO events recorded in Greenland ice cores. In this context, data presented here represent the first Central and East Asian aeolian dust records in which DO events are recorded, providing a means to test hypothesized links between short-term climate variability recorded in Greenland and associated climate dynamics at Asian dust source areas. Ultimately, the data extend existing hypotheses, suggesting that the Central and High Asian mountains are a crucial element within the sensitive glacier-desert-dust response system in interior Eurasia and may be considered a pacemaker

  6. Abrupt Climate Events Recorded in Chinese and Central Asian Loess Sequences

    NASA Astrophysics Data System (ADS)

    Machalett, Bjoern; Oches, Eric A.; Haam, Eddie; Lai, Zhongping; Endlicher, Wilfried

    2013-04-01

    Past climate dynamics associated with the Eurasian continent have been extensively studied. However, the impact of intra-hemispheric-scale climate variability on the entire Eurasian landmass, as well as the self-generated effects of the continent on the global climate system, is still a matter of investigation . While western Atlantic polar and tropical air masses penetrate into the continent and are transformed as they cross Eurasia, the interior regions of Eurasia strongly influence Earth's climate system. Significant cooling and heating of Central and High Asia drive interactions between atmospheric and oceanic processes and regulate teleconnection patterns across the Northern Hemisphere. This paper utilizes high resolution particle size data from the Central Asian loess sequence at Remisowka, Kazakhstan, and the long studied, monsoon-influenced Chinese loess sequence at Xifeng, to reconstruct past atmospheric circulation and aeolian dust dynamics within interior Eurasia since the last interglacial period. The observed dynamics in aeolian dust transport closely mirror d18O and fine dust variations measured in Greenland ice cores, suggesting a correlation with short-term climate oscillations (DO events) recorded therein. An Asian origin of fine aeolian dust preserved in Greenland ice cores has been discussed previously, and recent papers reveal a close link between Asian aeolian dust dynamics and DO events recorded in Greenland ice cores. In this context, data presented here represent the first Central and East Asian aeolian dust records in which DO events are recorded, providing a means to test hypothesized links between short-term climate variability recorded in Greenland and associated climate dynamics at Asian dust source areas. Ultimately, the data extend existing hypotheses, suggesting that the Central and High Asian mountains are a crucial element within the sensitive glacier-desert-dust response system in interior Eurasia and may be considered a pacemaker

  7. Aeolian processes at the Mars Exploration Rover Meridiani Planum landing site

    USGS Publications Warehouse

    Sullivan, R.; Banfield, D.; Bell, J.F.; Calvin, W.; Fike, D.; Golombek, M.; Greeley, R.; Grotzinger, J.; Herkenhoff, K.; Jerolmack, D.; Malin, M.; Ming, D.; Soderblom, L.A.; Squyres, S. W.; Thompson, S.; Watters, W.A.; Weitz, C.M.; Yen, A.

    2005-01-01

    The martian surface is a natural laboratory for testing our understanding of the physics of aeolian (wind-related) processes in an environment different from that of Earth. Martian surface markings and atmospheric opacity are time-variable, indicating that fine particles at the surface are mobilized regularly by wind. Regolith (unconsolidated surface material) at the Mars Exploration Rover Opportunity's landing site has been affected greatly by wind, which has created and reoriented bedforms, sorted grains, and eroded bedrock. Aeolian features here preserve a unique record of changing wind direction and wind strength. Here we present an in situ examination of a martian bright wind streak, which provides evidence consistent with a previously proposed formational model for such features. We also show that a widely used criterion for distinguishing between aeolian saltation- and suspension-dominated grain behaviour is different on Mars, and that estimated wind friction speeds between 2 and 3 m s-1, most recently from the northwest, are associated with recent global dust storms, providing ground truth for climate model predictions.

  8. Aeolian processes at the Mars Exploration Rover Meridiani Planum landing site.

    PubMed

    Sullivan, R; Banfield, D; Bell, J F; Calvin, W; Fike, D; Golombek, M; Greeley, R; Grotzinger, J; Herkenhoff, K; Jerolmack, D; Malin, M; Ming, D; Soderblom, L A; Squyres, S W; Thompson, S; Watters, W A; Weitz, C M; Yen, A

    2005-07-01

    The martian surface is a natural laboratory for testing our understanding of the physics of aeolian (wind-related) processes in an environment different from that of Earth. Martian surface markings and atmospheric opacity are time-variable, indicating that fine particles at the surface are mobilized regularly by wind. Regolith (unconsolidated surface material) at the Mars Exploration Rover Opportunity's landing site has been affected greatly by wind, which has created and reoriented bedforms, sorted grains, and eroded bedrock. Aeolian features here preserve a unique record of changing wind direction and wind strength. Here we present an in situ examination of a martian bright wind streak, which provides evidence consistent with a previously proposed formational model for such features. We also show that a widely used criterion for distinguishing between aeolian saltation- and suspension-dominated grain behaviour is different on Mars, and that estimated wind friction speeds between 2 and 3 m s(-1), most recently from the northwest, are associated with recent global dust storms, providing ground truth for climate model predictions.

  9. Records of human occupation from Pleistocene river terrace and aeolian sediments in the Arneiro depression (Lower Tejo River, central eastern Portugal)

    NASA Astrophysics Data System (ADS)

    Cunha, Pedro P.; Almeida, Nelson A. C.; Aubry, Thierry; Martins, António A.; Murray, Andrew S.; Buylaert, Jan-Pieter; Sohbati, Reza; Raposo, Luis; Rocha, Leonor

    2012-09-01

    In the uppermost reach of the Lower Tejo River (eastern central Portugal), where the river crosses two quartzite ridges that separate the Ródão (upstream) and Arneiro (downstream) depressions, Palaeolithic artefacts have been recovered from three lower river terrace levels and a cover unit of aeolian sands. This paper presents data on the discovery of archaeological artefacts from the terrace levels and the aeolian sands that can be linked to Middle and Upper Palaeolithic industries from new field sites at Tapada do Montinho and Castelejo. The archaeological data when placed in a geomorphological, sedimentary and chronological framework, contribute new information on the understanding of human occupation in western Iberia during cold-climate episodes of the last 62 to 12 ka; and especially during the cooler and driest conditions that occurred between 32 and 12 ka, when the climate favoured aeolian sediment transport. In the Lower Tejo River, the integration of absolute age datasets with archaeological, geomorphological and sedimentary data indicate that in westernmost Iberia the first appearance of artefacts in river terrace sediments suggests that the earliest marker for human occupation dates from the lower Acheulian (Lower Palaeolithic), probably corresponding to an age of ~ 340 ka. Data also suggest, for the first time, that Acheulian lithic industries were replaced by Middle Palaeolithic ones (namely the Levallois stone knapping technique) by ~ 160 ka (~ MIS6). Middle Palaeolithic industries were later replaced by Upper Palaeolithic industries at 32 ka. The post 32 ka period, dominated by aeolian sediment transport, is related to the onset of cold-dry climate conditions which resulted in low river flow discharges, floodplain exposure and reworking by NW winds. This cold-dry period is coeval with the disappearance of Megafauna and associated Neanderthal communities, and the replacement of the Middle Palaeolithic industries by Upper Palaeolithic ones in this

  10. Threshold wind velocity dynamics as a driver of aeolian sediment mas flux

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Horizontal (saltation) mass flux is a key driver of aeolian dust emission. Estimates of the horizontal mass flux underpin assessments of the global dust budget and influence our understanding of the dust cycle and its interactions. Current equations for predicting horizontal mass flux are based on l...

  11. A 16-year record of eolian dust in Southern Nevada and California, USA: Controls on dust generation and accumulation

    USGS Publications Warehouse

    Reheis, M.C.

    2006-01-01

    An ongoing project monitors modern dust accumulation in the arid southwestern United States to (1) determine the rate and composition of dust inputs to soils and (2) relate dust accumulation to weather patterns to help predict the effects of climate change on dust production and accumulation. The 16-year records of 35 dust-trap sites in the eastern Mojave Desert and southern Great Basin reveal how generation and accumulation of dust, including the silt-clay, carbonate, and soluble-salt fractions, is affected by the amount and seasonal distribution of rainfall and the behavior of different source types (alluvium, dry playas, and wet playas). Accumulation rates (fluxes) of the silt-clay fraction of dust, including carbonates, range from about 2-20 g/m2/yr. Average rates are higher in the southern part of the study area (south of latitude 36.5??N) and annually fluctuate over a larger range than rates in the northern part of the area. Sites throughout the study area show peaks in dust flux in the 1984-1985 sampling period and again in 1997-1999; northern sites also show increased flux in 1987-1988 and southern sites in 1989-1991. These peaks of dust flux correspond with both La Nina (dry) conditions and with strong El Nino (wet) periods. The accumulation rates of different components of mineral dusts fluctuate differently. For example, soluble-salt flux increases in 1987-1988, coincident with a moderate El Nino event, and increases very strongly in 1997-1999, overlapping with a strong El Nino event. Both of these high-rainfall winters were preceded and accompanied by strong summer rains. In contrast, little or no change in soluble-salt flux occurred during other periods of high winter rainfall but little summer rain, e.g. 1992-1995. The differences between northern vs. southern sites and between sites with playa dust sources vs. alluvial dust sources indicate that regional differences in the response of precipitation and vegetation growth to ENSO influence and

  12. The link between marine sediment records and changes in Holocene Saharan landscape: simulating the dust cycle

    NASA Astrophysics Data System (ADS)

    Egerer, Sabine; Claussen, Martin; Reick, Christian; Stanelle, Tanja

    2016-04-01

    Marine sediment records reveal an abrupt and strong increase in dust deposition in the North Atlantic at the end of the African Humid Period about 4.9 to 5.5 ka ago. The change in dust flux has been attributed to varying Saharan land surface cover. Alternatively, the enhanced dust accumulation is linked to enhanced surface winds and a consequent intensification of coastal upwelling. Here we demonstrate for the first time the direct link between dust accumulation in marine cores and changes in Saharan land surface. We simulate the mid-Holocene (6 ka BP) and pre-industrial (1850 AD) dust cycle as a function of Saharan land surface cover and atmosphere-ocean conditions using the coupled atmosphere-aerosol model ECHAM6.1-HAM2.1. Mid-Holocene surface characteristics, including vegetation cover and lake surface area, are derived from proxy data and simulations. In agreement with data from marine sediment cores, our simulations show that mid-Holocene dust deposition fluxes in the North Atlantic were two to three times lower compared with pre-industrial fluxes. We identify Saharan land surface characteristics to be the main control on dust transport from North Africa to the North Atlantic. We conclude that the increase in dust accumulation in marine cores is directly linked to a transition of the Saharan landscape during the Holocene and not due to changes in atmospheric or ocean conditions alone.

  13. Holocene aeolian development in Central Spain; chronology, regional correlations and causal processes

    NASA Astrophysics Data System (ADS)

    García-Hidalgo, José F.; Temiño, Javier; Segura, Manuel

    2007-10-01

    Extensive areas in the southern part of the Duero Tertiary Basin (Central Spain) are covered by aeolian sands. Presently, the aeolian system is relict but in its origin and development it can be described as a "wet aeolian system". Climatic and environmental changes during the Holocene are typified by alternating humid and arid periods. These are recorded in the sedimentary record as either organic-rich sandy palaeosols or clean aeolian sand, respectively. Palaeosol dating (12 radiocarbon dated samples) and stratigraphical and sedimentological analysis of several dunefields in quarries and boreholes allow the distinction of four periods of palaeosol development since the Allerød. Aeolian sediments commonly rest on fluvial deposits, which were themselves the major source area for aeolian sands. These fluvial deposits have an age of about 14,000 cal yr BP. The first phase of aeolian activity postdates these fluvial sediments and has an upper age of about 12,000-11,700 cal yr BP, probably corresponding to the last cold oscillation of the Lateglacial (Younger Dryas). The second phase ranges from about 11,500 to 9500 cal yr BP, during which period the majority of dunes in the Tierra de Pinares area formed. This is also a major phase of aeolian activity in other areas of the Iberian Peninsula. A third and probably discontinuous phase of aeolian activity took place between 6800 and about 3000 cal yr BP. The age for this phase is supported by the presence of Visigothic burial sites covered by aeolian sands. The presence of charred material and degraded slipfaces clearly indicate stabilisation by vegetation and the final degradation of the aeolian system at the end of the fourth aeolian phase (990-540 cal yr BP). Minor aeolian activity has also occurred subsequently in this area, since aeolian sand movement was even reported in the 20th century. The aeolian phases can be tentatively correlated with aeolian phases in Europe. Aeolian activity tends to occur regionally during

  14. Aeolian modification of planetary surfaces

    NASA Technical Reports Server (NTRS)

    Greeley, R.

    1982-01-01

    Any planet or satellite having a dynamic atmosphere and a solid surface is subject to aeolian or wind processes. A survey of the solar system shows that earth, Mars, Venus, and possibly Titan meet these criteria. Attention is given to the relevance of aeolian processes to planetary geology, approaches for investigating aeolian processes, observations on Mars, conditions on Venus, and studies of Titan with the aid of the Voyager spacecraft. It is found that aeolian processes play an important role in the modification of the surfaces of earth and Mars. Indirect evidence suggests that Venus and perhaps Titan also may experience aeolian activity. Study of aeolian activity in a planetary context thus affords the opportunity to examine a fundamental process under a wide range of environmental conditions. Each planet can be viewed as a vast natural laboratory.

  15. Regional distribution of monsoon and desert dust signals recorded in Asian glaciers

    NASA Astrophysics Data System (ADS)

    Wake, Cameron P.; Mayewski, Paul A.; Xie, Zichu; Wang, Ping; Li, Zhongqin

    1993-07-01

    Short-term (6 months to 17 years) glaciochemical records have been collected from glacier basins throughout the mountains of central Asia. The spatial distribution of snow chemistry in central Asia is controlled predominantly by the influx of dust from the arid and semi-arid regions in central Asia. The glaciochemical data suggests that glaciers which are removed from large source areas of mineral aerosol, such as those in the Himalaya, the Karakoram, and the southeastern Tibetan Plateau, are the ones most likely to contain longer-term glaciochemical records which detail annual to decadal variation in the strength of the Asian monsoon and long-range transport of Asian dust.

  16. Comparing dust flux records from the Subarctic North Pacific and Greenland: Implications for atmospheric transport to Greenland and for the application of dust as a chronostratigraphic tool

    NASA Astrophysics Data System (ADS)

    Serno, Sascha; Winckler, Gisela; Anderson, Robert F.; Maier, Edith; Ren, Haojia; Gersonde, Rainer; Haug, Gerald H.

    2015-06-01

    We present a new record of eolian dust flux to the western Subarctic North Pacific (SNP) covering the past 27,000 years based on a core from the Detroit Seamount. Comparing the SNP dust record to the North Greenland Ice Core Project (NGRIP) ice core record shows significant differences in the amplitude of dust changes to the two regions during the last deglaciation, while the timing of abrupt changes is synchronous. If dust deposition in the SNP faithfully records its mobilization in East Asian source regions, then the difference in the relative amplitude must reflect climate-related changes in atmospheric dust transport to Greenland. Based on the synchronicity in the timing of dust changes in the SNP and Greenland, we tie abrupt deglacial transitions in the 230Th-normalized 4He flux record to corresponding transitions in the well-dated NGRIP dust flux record to provide a new chronostratigraphic technique for marine sediments from the SNP. Results from this technique are complemented by radiocarbon dating, which allows us to independently constrain radiocarbon paleoreservoir ages. We find paleoreservoir ages of 745 ± 140 years at 11,653 year B.P., 680 ± 228 years at 14,630 year B.P., and 790 ± 498 years at 23,290 year B.P. Our reconstructed paleoreservoir ages are consistent with modern surface water reservoir ages in the western SNP. Good temporal synchronicity between eolian dust records from the Subantarctic Atlantic and equatorial Pacific and the ice core record from Antarctica supports the reliability of the proposed dust tuning method to be used more widely in other global ocean regions.

  17. Interpretation of palaeomonsoon dynamics on the Eastern Tibetan Plateau from a 10kyr peat record of dust deposition and regional atmospheric model simulations

    NASA Astrophysics Data System (ADS)

    Ferrat, M.; Weiss, D. J.; Dong, S.; Langmann, B.; Spiro, B.; Large, D.

    2010-12-01

    The eastern Qinghai-Tibetan Plateau is a climatically sensitive region, located today under the influence of the East Asian monsoon, the Indian summer monsoon and the westerlies. However, the evolution of atmospheric circulation patterns over this area through time remains poorly constrained due to the lack of information on changes in past wind trajectories and intensities. The study of this variability in climate archives is key to a better understanding of past Asian atmospheric dynamics and the refining of regional climate models. Our aim is to constrain Holocene palaeomonsoon dynamics over the eastern Qinghai-Tibetan Plateau through: 1) The geochemical study of atmospheric mineral dust deposited in a well-dated, continuous peat core; 2) The interpretation of results with respect to atmospheric simulations of dust transport under recent climatic scenarios using the regional climate model REMOTE. Dust mobilized by strong winds from the large deserts and sandy lands of northern China and India is transported over Asia by the different atmospheric currents and the study of mineral dust in our climate archive will allow us to: (a) quantify aeolian deposition, and hence study past wind strength; (b) identify the dominant dust sources (local, regional and long-range) through the application of geochemical provenance tracers, and hence study atmospheric pathways. Holocene dust fluxes in the peat core vary from 2-33 g m-2 y-1. Analysis of the dust record and surface samples from the potential source areas indicates that the europium anomaly, the ratios Y/Tb, Y/ΣREE, Sc/La, La/Th, Th/ ΣREE and Y/Er, as well as Pb isotopes (204Pb, 206Pb, 207Pb and 208Pb) are effective geochemical tracers to distinguish between the different dust sources. Results suggest that the deserts and loess deposits of northern China and the deserts of northwestern China dominated deposition to the core throughout the Holocene and particularly during the last 5kyr. Earlier deposition was also

  18. Peatland records of dust deposition from Middleton Island, Gulf of Alaska

    NASA Astrophysics Data System (ADS)

    Moy, C. M.; Crusius, J.; Schroth, A. W.; Nichols, J. E.; Peteet, D. M.; Kenna, T. C.; Giosan, L.; Eglinton, T. I.; Gassó, S.

    2011-12-01

    Iron is an important micronutrient that limits the growth of phytoplankton in much of the global ocean. In the Gulf of Alaska (GoA), we have a limited knowledge of the processes that transport iron, and in particular, the role eolian dust plays in delivering iron to the ocean surface. In order to better understand both modern and past mechanisms of dust deposition in the GoA, we examine satellite, NCEP reanalysis, and meteorological station data as well as geochemical data from peat cores collected from Middleton Island (59.43°N, 146.34°W). Widespread dust events have been observed in MODIS satellite imagery emanating from exposed floodplains within the Copper River valley and adjacent glaciated river valleys in southcentral Alaska (AK). Dust events are common in the fall when high pressure in the AK interior and low pressure in the central GoA establish a tight pressure gradient that drives anomalously strong northerly winds. Low river levels and limited snow coverage expose fine-grained glacial sediments that are entrained by winds. MODIS imagery indicates dust reaches beyond the continental shelf, and in many instances, dust plumes have been observed passing over Middleton Island (100 km SSW of the Copper River delta). To better constrain dust deposition from southcentral AK on geologic timescales, we collected cores from an extensive peat bog on Middleton Island, located at the edge of the continental shelf. X-ray imagery, bulk density, magnetic susceptibility, loss on ignition, and profiling XRF data indicate significant variations in inorganic or clastic components within the organic peat matrix. Because these cores were collected near the island's topographic high point, we infer that all inorganic constituents are likely delivered as dust, with potential secondary contributions from volcanic ash. We will present a well-dated, high-resolution scanning XRF profile that spans the last 5200 years and records downcore variations in terrigenous material that

  19. A 200,000-year record of late Quaternary Aeolian sedimentation on the Southern High Plains and nearby Pecos River Valley, USA

    NASA Astrophysics Data System (ADS)

    Rich, J.; Stokes, S.

    2011-03-01

    Presently stabilized Southern High Plains (SHP) dune systems have been repeatedly re-activated during the past 200,000 years, providing an archive of environmental and related climatic change for the late Quaternary. Our data set of 38 optically dated samples from four different localities identifies eolian activity from late-middle Pleistocene to the historic period. Oldest eolian sediments are from the Blackwater Draw Formation and indicate accretion during late-middle to late Pleistocene. Younger sediments dating from the later Pleistocene through the Holocene are found in the Muleshoe, Lea-Yoakum, Mescalero, and Monahans dunes that overlie the Blackwater Draw Formation. Muleshoe dunes accreted during the Late Pleistocene between 31 ± 3 and 27 ± 2 ka, while Holocene deposition transpired 7.5 ± 0.4, 4.0 ± 0.7 ka through 3.6 ± 0.4 ka, and between 1.3 ± 0.2 and 1.1 ± 0.1 ka. A period of dune building for Lea-Yoakum dune sediments occurred during the late Pleistocene (48 ± 5 ka), and the later Holocene (3.6 ± 0.4 ka). Mescalero and Monahans dunes were accreting during the later Pleistocene between 29 ± 3 and 22 ± 2 ka followed by a sequence of eolian sand deposited ca. 15 ka. Holocene eolian sedimentation for the Mescalero and Monahans dunes occurred 7.5 ± 0.8, 5.1 ± 0.5, 4.3 ± 0.4, and 2.0 ± 0.3 ka. Historic eolian deposition is identifiable in the dune chronology with multiple optical age estimates overlapping established drought events recorded ca. 1890, 1910, 1920, and during the 1930's when the North American "Dust Bowl" transpired. These Quaternary eolian deposits mantling the Southern High Plains are an important component of the surficial material of the region and provide a rich archive of past climatic change.

  20. The Icelandic volcanic aeolian environment: Processes and impacts - A review

    NASA Astrophysics Data System (ADS)

    Arnalds, Olafur; Dagsson-Waldhauserova, Pavla; Olafsson, Haraldur

    2016-03-01

    Iceland has the largest area of volcaniclastic sandy desert on Earth or 22,000 km2. The sand has been mostly produced by glacio-fluvial processes, leaving behind fine-grained unstable sediments which are later re-distributed by repeated aeolian events. Volcanic eruptions add to this pool of unstable sediments, often from subglacial eruptions. Icelandic desert surfaces are divided into sand fields, sandy lavas and sandy lag gravel, each with separate aeolian surface characteristics such as threshold velocities. Storms are frequent due to Iceland's location on the North Atlantic Storm track. Dry winds occur on the leeward sides of mountains and glaciers, in spite of the high moisture content of the Atlantic cyclones. Surface winds often move hundreds to more than 1000 kg m-1 per annum, and more than 10,000 kg m-1 have been measured in a single storm. Desertification occurs when aeolian processes push sand fronts and have thus destroyed many previously fully vegetated ecosystems since the time of the settlement of Iceland in the late ninth century. There are about 135 dust events per annum, ranging from minor storms to >300,000 t of dust emitted in single storms. Dust production is on the order of 30-40 million tons annually, some traveling over 1000 km and deposited on land and sea. Dust deposited on deserts tends to be re-suspended during subsequent storms. High PM10 concentrations occur during major dust storms. They are more frequent in the wake of volcanic eruptions, such as after the Eyjafjallajökull 2010 eruption. Airborne dust affects human health, with negative effects enhanced by the tubular morphology of the grains, and the basaltic composition with its high metal content. Dust deposition on snow and glaciers intensifies melting. Moreover, the dust production probably also influences atmospheric conditions and parameters that affect climate change.

  1. Aeolian Slipface Processes on Earth and Mars

    NASA Astrophysics Data System (ADS)

    Cornwall, Carin; Jackson, Derek; Bourke, Mary; Cooper, Andrew

    2016-04-01

    The surface of Mars is dominated by aeolian features and many locations show ripple and dune migration over the past decade with some sediment fluxes comparable to terrestrial dunes. One of the leading goals in investigating aeolian processes on Mars is to explore the boundary conditions of sediment transport, accumulation, and dune mor-phology in relation to wind regime as well as to quantify migration rates and sediment flux. We combine terrestrial field observations, 3D computational fluid dynamics (CFD) modeling and remote sensing data to investigate com-plex, small scale wind patterns and grainflow processes on terrestrial and martian dunes. We aim to constrain grain flow magnitudes and frequencies that occur on slipface slopes of dunes in order to improve estimates of martian dune field migration and sediment flux related to wind velocity and flow patterns. A series of ground-based, high resolution laser scans have been collected in the Maspalomas dune field in Gran Canaria, Spain to investigate grainflow frequency, morphology and slipface advancement. Analysis of these laser scans and simultaneous video recordings have revealed a variety of slipface activity. We identify 6 different grain-flow morphologies including, hourglass shape (classic alcove formation with deposit fan below), superficial flow (thin lenses), narrow trough (vertical lines cm in width), sheet, column (vertical alcove walls), and complex (combi-nation of morphologies triggered simultaneously in the same location). Hourglass grainflow morphologies were the most common and occurred regularly. The superficial and narrow trough morphologies were the second most com-mon and frequently occurred in between large grain flows. Sheet grainflows were rare and unpredictable. These flows involved large portions of the slipface (metres across) and mobilized a substantial amount of sediment in one event. We have compared these grainflow morphologies from Maspalomas to those in martian dune fields and

  2. High-resolution mineral dust and sea ice proxy records from the Talos Dome ice core

    NASA Astrophysics Data System (ADS)

    Schüpbach, S.; Federer, U.; Kaufmann, P. R.; Albani, S.; Barbante, C.; Stocker, T. F.; Fischer, H.

    2013-12-01

    In this study we report on new non-sea salt calcium (nssCa2+, mineral dust proxy) and sea salt sodium (ssNa+, sea ice proxy) records along the East Antarctic Talos Dome deep ice core in centennial resolution reaching back 150 thousand years (ka) before present. During glacial conditions nssCa2+ fluxes in Talos Dome are strongly related to temperature as has been observed before in other deep Antarctic ice core records, and has been associated with synchronous changes in the main source region (southern South America) during climate variations in the last glacial. However, during warmer climate conditions Talos Dome mineral dust input is clearly elevated compared to other records mainly due to the contribution of additional local dust sources in the Ross Sea area. Based on a simple transport model, we compare nssCa2+ fluxes of different East Antarctic ice cores. From this multi-site comparison we conclude that changes in transport efficiency or atmospheric lifetime of dust particles do have a minor effect compared to source strength changes on the large-scale concentration changes observed in Antarctic ice cores during climate variations of the past 150 ka. Our transport model applied on ice core data is further validated by climate model data. The availability of multiple East Antarctic nssCa2+ records also allows for a revision of a former estimate on the atmospheric CO2 sensitivity to reduced dust induced iron fertilisation in the Southern Ocean during the transition from the Last Glacial Maximum to the Holocene (T1). While a former estimate based on the EPICA Dome C (EDC) record only suggested 20 ppm, we find that reduced dust induced iron fertilisation in the Southern Ocean may be responsible for up to 40 ppm of the total atmospheric CO2 increase during T1. During the last interglacial, ssNa+ levels of EDC and EPICA Dronning Maud Land (EDML) are only half of the Holocene levels, in line with higher temperatures during that period, indicating much reduced sea

  3. The Dust Storm Index (DSI): A method for monitoring broadscale wind erosion using meteorological records

    NASA Astrophysics Data System (ADS)

    O'Loingsigh, T.; McTainsh, G. H.; Tews, E. K.; Strong, C. L.; Leys, J. F.; Shinkfield, P.; Tapper, N. J.

    2014-03-01

    Wind erosion of soils is a natural process that has shaped the semi-arid and arid landscapes for millennia. This paper describes the Dust Storm Index (DSI); a methodology for monitoring wind erosion using Australian Bureau of Meteorology (ABM) meteorological observational data since the mid-1960s (long-term), at continental scale. While the 46 year length of the DSI record is its greatest strength from a wind erosion monitoring perspective, there are a number of technical challenges to its use because when the World Meteorological Organisation (WMO) recording protocols were established the use of the data for wind erosion monitoring was never intended. Data recording and storage protocols are examined, including the effects of changes to the definition of how observers should interpret and record dust events. A method is described for selecting the 180 long-term ABM stations used in this study and the limitations of variable observation frequencies between stations are in part resolved. The rationale behind the DSI equation is explained and the examples of temporal and spatial data visualisation products presented include; a long term national wind erosion record (1965-2011), continental DSI maps, and maps of the erosion event types that are factored into the DSI equation. The DSI is tested against dust concentration data and found to provide an accurate representation of wind erosion activity. As the ABM observational records used here were collected according to WMO protocols, the DSI methodology could be used in all countries with WMO-compatible meteorological observation and recording systems.

  4. A Lacustrine Record of Postglacial Dust Deposition from the Uinta Mountains, Utah, USA

    NASA Astrophysics Data System (ADS)

    Munroe, Jeffrey

    2015-04-01

    Samplers deployed in 2011 reveal a modern dust flux to the alpine zone (>3000 m asl) of the Uinta Mountains (Utah, USA) of ~4 gm/m2/yr. A notably uniform layer of silt, ~20 cm thick, in soil profiles from throughout the alpine zone, along with the presence in soils and modern dust of minerals not found in the bedrock, indicates that dust deposition has been an important long-term process in this environment. To evaluate how dust flux and properties have changed over the postglacial period a 190 cm-long lacustrine sediment core was analyzed. The core was collected with a percussion corer from a small lake (8 ha) at an elevation of 3043 m asl in 10.6 m of water. Six AMS 14C analyses on conifer needles, wood fragments, and bulk sediment support a depth-age model extending back to 12.7 ka BP. Loose near-surface sediment was not recovered, so the top of the core is truncated at 1.36 ka BP. Geochemical composition was evaluated at 2-cm intervals using ICP-AES after fluxing of ignited samples with LiBO2. The abundance of rare earth elements was determined for a subset of 16 samples using ICP-MS. Mineralogy was investigated at 2-cm intervals using XRD. Grain size distribution, organic matter content, and C:N ratio were determined at 1-cm intervals using laser scattering, loss-on-ignition, and an elemental analyzer, respectively. Results indicate that the flux and properties of dust arriving in the Uinta Mountains have varied over time, with the most significant variations occurring between 6.5 and 4.5 ka BP. During that time ratios of Zr/Al, Ti/Al and (Ca+Mg)/Fe rise to record-high values, and the abundance of Illite+Chlorite increases relative to feldspar. Prominent shifts occur in the abundances of some trace elements, such as Sc, along with changes in median grain size. The ratio La/Lu, as well as the magnitude of the Eu anomaly, also change. Collectively these fluctuations are consistent with a greater flux of dust to the Uinta Mountains, as well as a possible change

  5. Small-Scale Dust Structures in Halley's Coma: Evidence from the Vega-2 Electric Field Records

    NASA Astrophysics Data System (ADS)

    Oberc, P.

    1999-07-01

    Owing to simultaneous dust and plasma wave observations onboard the Vega mission to Comet Halley, previous studies have found that the two double probe antennas, short (of APV-N experiment) and long (APV-V), (i) responded to plasma clouds induced by impacts of relatively large particles, (ii) the target area was comparable to the whole spacecraft projection, and (iii) the mass thresholds depended on the ambient plasma conditions. Subsequently, the response mechanisms have been identified, and it was shown that if impacts became continuous, the sensitivity of the antennas to individual plasma clouds was reduced or even cancelled. In the present paper, about 30 short-time events of continuous impact (CIEs), recognized in the Vega-2 records from the two experiments mostly near the closest approach to (at ∼104 km from) the nucleus, are investigated. The high-resolution APV-N waveforms reveal that the respective dust formations were structured. A few types of structure, all belonging to one family, have been distinguished. The basic structure, as seen along the Vega-2 pass, is a sequence of particle clouds. CIEs have time scales shorter than or comparable to the time resolution of the dust experiments (spatial scale less than 200 km) and do not correlate with the SP-1 observations (m≤10-10 g) nor with the published SP-2 fluxes (m≤5.8×10-8 g). But, these dust data, combined with an integral criterion for continuous impact, provide a constraint which implies that the particles responsible were bigger than 10-9-10-8 g. The data from the DUCMA V-detector confirm positively this inference for about 1/3 (∼10) of CIEs and indicate that particles (much) bigger than 10-7 g were decisive in generating several other events. Using an argument from the dusty gas dynamics, it is shown that the small-scale dust structures were not jets but have originated from the disintegration of particle aggregates. An estimate of the total mass contained within a dust structure leads to

  6. Aeolian sand ripples around plants

    NASA Astrophysics Data System (ADS)

    Zhang, Qian-Hua; Miao, Tian-De

    2003-05-01

    Plants in the desert may locally change the aeolian process, and hence the pattern of sand ripples traveling nearby. The effect of plants on ripples is investigated using a coupled map lattice model with nonuniform coupling coefficients.

  7. Radar-aeolian roughness project

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald; Dobrovolskis, A.; Gaddis, L.; Iversen, J. D.; Lancaster, N.; Leach, Rodman N.; Rasnussen, K.; Saunders, S.; Vanzyl, J.; Wall, S.

    1991-01-01

    The objective is to establish an empirical relationship between measurements of radar, aeolian, and surface roughness on a variety of natural surfaces and to understand the underlying physical causes. This relationship will form the basis for developing a predictive equation to derive aeolian roughness from radar backscatter. Results are given from investigations carried out in 1989 on the principal elements of the project, with separate sections on field studies, radar data analysis, laboratory simulations, and development of theory for planetary applications.

  8. Mars sampling strategy and aeolian processes

    NASA Technical Reports Server (NTRS)

    Greeley, Ronald

    1988-01-01

    It is critical that the geological context of planetary samples (both in situ analyses and return samples) be well known and documented. Apollo experience showed that this goal is often difficult to achieve even for a planet on which surficial processes are relatively restricted. On Mars, the variety of present and past surface processes is much greater than on the Moon and establishing the geological context of samples will be much more difficult. In addition to impact hardening, Mars has been modified by running water, periglacial activity, wind, and other processes, all of which have the potential for profoundly affecting the geological integrity of potential samples. Aeolian, or wind, processes are ubiquitous on Mars. In the absence of liquid water on the surface, aeolian activity dominates the present surface as documented by frequent dust storms (both local and global), landforms such as dunes, and variable features, i.e., albedo patterns which change their size, shape, and position with time in response to the wind.

  9. Dust Aerosol, Clouds, and the Atmospheric Optical Depth Record over 5 Mars Years of the Mars Exploration Rover Mission

    NASA Technical Reports Server (NTRS)

    Lemmon, Mark T.; Wolff, Michael J.; Bell, James F., III; Smith, Michael D.; Cantor, Bruce A.; Smith, Peter H.

    2014-01-01

    Dust aerosol plays a fundamental role in the behavior and evolution of the Martian atmosphere. The first five Mars years of Mars Exploration Rover data provide an unprecedented record of the dust load at two sites. This record is useful for characterization of the atmosphere at the sites and as ground truth for orbital observations. Atmospheric extinction optical depths have been derived from solar images after calibration and correction for time-varying dust that has accumulated on the camera windows. The record includes local, regional, and globally extensive dust storms. Comparison with contemporaneous thermal infrared data suggests significant variation in the size of the dust aerosols, with a 1 micrometer effective radius during northern summer and a 2 micrometer effective radius at the onset of a dust lifting event. The solar longitude (L (sub s)) 20-136 degrees period is also characterized by the presence of cirriform clouds at the Opportunity site, especially near LS = 50 and 115 degrees. In addition to water ice clouds, a water ice haze may also be present, and carbon dioxide clouds may be present early in the season. Variations in dust opacity are important to the energy balance of each site, and work with seasonal variations in insolation to control dust devil frequency at the Spirit site.

  10. Model validation of untethered, ultrasonic neural dust motes for cortical recording.

    PubMed

    Seo, Dongjin; Carmena, Jose M; Rabaey, Jan M; Maharbiz, Michel M; Alon, Elad

    2015-04-15

    A major hurdle in brain-machine interfaces (BMI) is the lack of an implantable neural interface system that remains viable for a substantial fraction of the user's lifetime. Recently, sub-mm implantable, wireless electromagnetic (EM) neural interfaces have been demonstrated in an effort to extend system longevity. However, EM systems do not scale down in size well due to the severe inefficiency of coupling radio-waves at those scales within tissue. This paper explores fundamental system design trade-offs as well as size, power, and bandwidth scaling limits of neural recording systems built from low-power electronics coupled with ultrasonic power delivery and backscatter communication. Such systems will require two fundamental technology innovations: (1) 10-100 μm scale, free-floating, independent sensor nodes, or neural dust, that detect and report local extracellular electrophysiological data via ultrasonic backscattering and (2) a sub-cranial ultrasonic interrogator that establishes power and communication links with the neural dust. We provide experimental verification that the predicted scaling effects follow theory; (127 μm)(3) neural dust motes immersed in water 3 cm from the interrogator couple with 0.002064% power transfer efficiency and 0.04246 ppm backscatter, resulting in a maximum received power of ∼0.5 μW with ∼1 nW of change in backscatter power with neural activity. The high efficiency of ultrasonic transmission can enable the scaling of the sensing nodes down to 10s of micrometer. We conclude with a brief discussion of the application of neural dust for both central and peripheral nervous system recordings, and perspectives on future research directions. PMID:25109901

  11. Model validation of untethered, ultrasonic neural dust motes for cortical recording.

    PubMed

    Seo, Dongjin; Carmena, Jose M; Rabaey, Jan M; Maharbiz, Michel M; Alon, Elad

    2015-04-15

    A major hurdle in brain-machine interfaces (BMI) is the lack of an implantable neural interface system that remains viable for a substantial fraction of the user's lifetime. Recently, sub-mm implantable, wireless electromagnetic (EM) neural interfaces have been demonstrated in an effort to extend system longevity. However, EM systems do not scale down in size well due to the severe inefficiency of coupling radio-waves at those scales within tissue. This paper explores fundamental system design trade-offs as well as size, power, and bandwidth scaling limits of neural recording systems built from low-power electronics coupled with ultrasonic power delivery and backscatter communication. Such systems will require two fundamental technology innovations: (1) 10-100 μm scale, free-floating, independent sensor nodes, or neural dust, that detect and report local extracellular electrophysiological data via ultrasonic backscattering and (2) a sub-cranial ultrasonic interrogator that establishes power and communication links with the neural dust. We provide experimental verification that the predicted scaling effects follow theory; (127 μm)(3) neural dust motes immersed in water 3 cm from the interrogator couple with 0.002064% power transfer efficiency and 0.04246 ppm backscatter, resulting in a maximum received power of ∼0.5 μW with ∼1 nW of change in backscatter power with neural activity. The high efficiency of ultrasonic transmission can enable the scaling of the sensing nodes down to 10s of micrometer. We conclude with a brief discussion of the application of neural dust for both central and peripheral nervous system recordings, and perspectives on future research directions.

  12. The origin of bimodal grain-size distribution for aeolian deposits

    NASA Astrophysics Data System (ADS)

    Lin, Yongchong; Mu, Guijin; Xu, Lishuai; Zhao, Xue

    2016-03-01

    Atmospheric dust deposition is a common phenomenon in arid and semi-arid regions. Bimodal grain size distribution (BGSD) (including the fine component and coarse component) of aeolian deposits has been widely reported. But the origin of this pattern is still debated. Here, we focused on the sedimentary process of modern dust deposition, and analyzed the grain size distribution of modern dust deposition, foliar dust, and aggregation of the aeolian dust collected in Cele Oasis, southern margin of Tarim Basin. The results show that BGSD also appear in a dust deposition. The content of fine components (<20 μm size fraction) change with temporal and spatial variation. Fine component from dust storm is significant less than that from subsequent floating dust. Fine component also varies with altitude. These indicate that modern dust deposition have experienced changing aerodynamic environment and be reworked during transportation and deposition, which is likely the main cause for BGSD. The dusts from different sources once being well-mixed in airflow are hard to form multiple peaks respectively corresponding with different sources. In addition, the dust deposition would appear BGSD whether aggregation or not. Modern dust deposition is the continuation of ancient dust deposition. They both may have the same cause of formation. Therefore, the origin of BGSD should provide a theoretical thinking for reconstructing the palaeo-environmental changes with the indicator of grain size.

  13. Contemporary proglacial aeolian sediment transport in West Greenland

    NASA Astrophysics Data System (ADS)

    Bullard, J. E.; Austin, M. J.

    2007-12-01

    Glacial erosion processes produce significance quantities of fine sediments that are washed out from beneath glaciers by meltwater. When deposited on the glacier floodplain they dessicate and strong ice-driven winds can entrain and transport them across the landscape resulting in the formation of sand dunes and loess, and adding very fine particles (dust) to the atmosphere. Recent studies suggest that locally-generated dust can play an important role in regulating albedo and the melting rate of glaciers. Very few field process studies have examined the relationship between sediment-delivery to the proglacial floodplain by meltwater and the subsequent aeolian erosion and deposition of these fine sediments. This research reports the use of semi-isokinetic directional sediment samplers to make an initial assessment of the rates of transport of dust and sand in Sandflugtdalen, a valley adjacent to the West Greenland ice sheet. Vertical arrays (z(m) = 0.18, 0.43, 0.85, 1.4) of samplers were deployed in a down valley transect over a distance of 4 km. Trapped sediments were retrieved after intervals of 1 week and 9 weeks. The mass of sediment collected in the traps varied from 0.002-3.62 g cm2 wk-1. As expected, near surface traps collected more, and coarser, sediment than those deployed at 1.4 m height but the decrease in mass of sediment with height was highly variable. The array closest to the glacier trapped the greatest quantity of suspended sediment and the density of suspended sediment decreased with distance down valley. The flux of aeolian sediment comprises clays, silts and sand-sized particles. Areas of aeolian entrainment, transport and deposition are closely linked to the development and distribution of sediments on the proglacial floodplain which varies considerably in terms of surface roughness. At the east end of the valley, close to the ice sheet, aeolian sediment flux is controlled by sediment supply and topography rather than wind speed. Further down

  14. The linkage between marine sediment records and changes in Holocene Saharan landscape: simulating the dust cycle

    NASA Astrophysics Data System (ADS)

    Egerer, Sabine; Claussen, Martin; Reick, Christian; Stanelle, Tanja

    2016-04-01

    Marine sediment records reveal an abrupt and strong increase in dust deposition in the North Atlantic at the end of the African Humid Period about 4.9 ka to 5.5 ka ago (deMenocal et al., 2000; McGee et al., 2013). The change in dust flux has been attributed to varying Saharan land surface cover. Alternatively, the enhanced dust accumulation is linked to enhanced surface winds and a consequent intensification of coastal upwelling. We present simulation results from a recent sensitivity study, where we demonstrate for the first time the direct link between dust accumulation in marine cores and changes in Saharan land surface during the Holocene. We have simulated timeslices of he mid-Holocene (6 ka BP) and pre-industrial (1850 AD) dust cycle as a function of Saharan land surface cover and atmosphere-ocean conditions using the coupled atmosphere-aerosol model ECHAM6.1-HAM2.1. We prescribe mid-Holocene vegetation cover based on a vegetation reconstruction from pollen data (Hoelzmann et al., 1998) and mid-Holocene lake surface area is determined using a water routing and storage model (Tegen et al., 2002). In agreement with data from marine sediment cores, our simulations show that mid-Holocene dust deposition fluxes in the North Atlantic were two to three times lower compared with pre-industrial fluxes. We identify Saharan land surface characteristics to be the main control on dust transport from North Africa to the North Atlantic. We conclude that the variation in dust accumulation in marine cores is likely related to a transition of the Saharan landscape during the Holocene and not due to changes in atmospheric or ocean conditions alone. Reference: deMenocal, P., Ortiz, J., Guilderson, T., Adkins, J., Sarnthein, M., Baker, L., and Yarusinsky, M.: Abrupt onset and termination of the African Humid Period:: rapid climate responses to gradual insolation forcing, Quaternary Science Reviews, 19, 347-361, 2000. Hoelzmann, P., Jolly, D., Harrison, S. P., Laarif, F

  15. Spatial and temporal patterns of dust emissions (2004-2012) in semi-arid landscapes, southeastern Utah, USA

    USGS Publications Warehouse

    Flagg, Cody B.; Neff, Jason C.; Reynolds, Richard L.; Belnap, Jayne

    2013-01-01

    Aeolian dust can influence nutrient availability, soil fertility, plant interactions, and water-holding capacity in both source and downwind environments. A network of 85 passive collectors for aeolian sediment spanning numerous plant communities, soil types, and land-use histories covering approximately 4000 square kilometers across southeastern Utah was used to sample horizontal emissions of aeolian sediment. The sample archive dates to 2004 and is currently the largest known record of field-scale dust emissions for the southwestern United States. Sediment flux peaked during the spring months in all plant communities (mean: 38.1 g m−2 d−1), related to higher, sustained wind speeds that begin in the early spring. Dust flux was lowest during the winter period (mean: 5 g m−2 d−1) when surface wind speeds are typically low. Sites dominated by blackbrush and sagebrush shrubs had higher sediment flux (mean: 19.4 g m−2 d−1) compared to grasslands (mean: 11.2 g m−2 d−1), saltbush shrublands (mean: 10.3 g m−2 d−1), and woodlands (mean: 8.1 g m−2 d−1). Contrary to other studies on dust emissions, antecedent precipitation during one, two, and three seasons prior to sample collection did not significantly influence emission rates. Physical site-scale factors controlling dust emissions were complex and varied from one vegetation type to another.

  16. Synthesis on Quaternary aeolian research in the unglaciated eastern United States

    USGS Publications Warehouse

    Markewich, Helaine Walsh; Litwin, Ronald J.; Wysocki, Douglas A.; Pavich, Milan J.

    2015-01-01

    Late-middle and late Pleistocene, and Holocene, inland aeolian sand and loess blanket >90,000 km2 of the unglaciated eastern United States of America (USA). Deposits are most extensive in the Lower Mississippi Valley (LMV) and Atlantic Coastal Plain (ACP), areas presently lacking significant aeolian activity. They provide evidence of paleoclimate intervals when wind erosion and deposition were dominant land-altering processes. This study synthesizes available data for aeolian sand deposits in the LMV, the Eastern Gulf Coastal Plain (EGCP) and the ACP, and loess deposits in the Middle Atlantic Coastal Plain (MACP). Data indicate: (a) the most recent major aeolian activity occurred in response to and coincident with growth and decay of the Laurentide Ice Sheet (LIS); (b) by ∼40 ka, aeolian processes greatly influenced landscape evolution in all three regions; (c) aeolian activity peaked in OIS2; (d) OIS3 and OIS2 aeolian records are in regional agreement with paleoecological records; and (e) limited aeolian activity occurred in the Holocene (EGCP and ACP). Paleoclimate and atmospheric-circulation models (PCMs/ACMs) for the last glacial maximum (LGM) show westerly winter winds for the unglaciated eastern USA, but do not resolve documented W and SW winds in the SEACP and WNW and N winds in the MACP. The minimum areal extent of aeolian deposits in the EGCP and ACP is ∼10,000 km2. For the LMV, it is >80,000 km2. Based on these estimates, published PCMs/ACMs likely underrepresent the areal extent of LGM aeolian activity, as well as the extent and complexity of climatic changes during this interval.

  17. Gully annealing by aeolian sediment: field and remote-sensing investigation of aeolian-hillslope-fluvial interactions, Colorado River corridor, Arizona, USA

    NASA Astrophysics Data System (ADS)

    Sankey, Joel B.; Draut, Amy E.

    2014-09-01

    Processes contributing to development of ephemeral gully channels are of great importance to landscapes worldwide, and particularly in dryland regions where soil loss and land degradation from gully erosion pose long-term land-management problems. Whereas gully formation has been relatively well studied, much less is known of the processes that anneal gullies and impede their growth. This study of gully annealing by aeolian sediment, spanning 95 km along the Colorado River corridor in Glen, Marble, and Grand Canyon, Arizona, USA, employed field and remote sensing observations, including digital topographic modelling. Results indicate that aeolian sediment activity can be locally effective at counteracting gully erosion. Gullies are less prevalent in areas where surficial sediment undergoes active aeolian transport, and have a greater tendency to terminate in active aeolian sand. Although not common, examples exist in the record of historical imagery of gullies that underwent infilling by aeolian sediment in past decades and evidently were effectively annealed. We thus provide new evidence for a potentially important interaction of aeolian-hillslope-fluvial processes, which could affect dryland regions substantially in ways not widely recognized. Moreover, because the biologic soil crust plays an important role in determining aeolian sand activity, and so in turn the extent of gully development, this study highlights a critical role of geomorphic-ecologic interactions in determining arid-landscape evolution.

  18. Aeolian Sand Transport with Collisional Suspension

    NASA Technical Reports Server (NTRS)

    Jenkins, James T.; Pasini, Jose Miguel; Valance, Alexandre

    2004-01-01

    Aeolian transport is an important mechanism for the transport of sand on Earth and on Mars. Dust and sand storms are common occurrences on Mars and windblown sand is responsible for many of the observed surface features, such as dune fields. A better understanding of Aeolian transport could also lead to improvements in pneumatic conveying of materials to be mined for life support on the surface of the Moon and Mars. The usual view of aeolian sand transport is that for mild winds, saltation is the dominant mechanism, with particles in the bed being dislodged by the impact of other saltating particles, but without in-flight collisions. As the wind becomes stronger, turbulent suspension keeps the particles in the air, allowing much longer trajectories, with the corresponding increase in transport rate. We show here that an important regime exists between these two extremes: for strong winds, but before turbulent suspension becomes dominant, there is a regime in which in-flight collisions dominate over turbulence as a suspension mechanism, yielding transport rates much higher than those for saltation. The theory presented is based on granular kinetic theory, and includes both turbulent suspension and particle-particle collisions. The wind strengths for which the calculated transport rates are relevant are beyond the published strengths of current wind tunnel experiments, so these theoretical results are an invitation to do experiments in the strong-wind regime. In order to make a connection between the regime of saltation and the regime of collisional suspension, it is necessary to better understand the interaction between the bed and the particles that collide with it. This interaction depends on the agitation of the particles of the bed. In mild winds, collisions with the bed are relatively infrequent and the local disturbance associated with a collision can relax before the next nearby collision. However, as the wind speed increases, collision become more frequent

  19. A Threshold Continuum for Aeolian Sand Transport

    NASA Astrophysics Data System (ADS)

    Swann, C.; Ewing, R. C.; Sherman, D. J.

    2015-12-01

    The threshold of motion for aeolian sand transport marks the initial entrainment of sand particles by the force of the wind. This is typically defined and modeled as a singular wind speed for a given grain size and is based on field and laboratory experimental data. However, the definition of threshold varies significantly between these empirical models, largely because the definition is based on visual-observations of initial grain movement. For example, in his seminal experiments, Bagnold defined threshold of motion when he observed that 100% of the bed was in motion. Others have used 50% and lesser values. Differences in threshold models, in turn, result is large errors in predicting the fluxes associated with sand and dust transport. Here we use a wind tunnel and novel sediment trap to capture the fractions of sand in creep, reptation and saltation at Earth and Mars pressures and show that the threshold of motion for aeolian sand transport is best defined as a continuum in which grains progress through stages defined by the proportion of grains in creep and saltation. We propose the use of scale dependent thresholds modeled by distinct probability distribution functions that differentiate the threshold based on micro to macro scale applications. For example, a geologic timescale application corresponds to a threshold when 100% of the bed in motion whereas a sub-second application corresponds to a threshold when a single particle is set in motion. We provide quantitative measurements (number and mode of particle movement) corresponding to visual observations, percent of bed in motion and degrees of transport intermittency for Earth and Mars. Understanding transport as a continuum provides a basis for revaluating sand transport thresholds on Earth, Mars and Titan.

  20. Gully annealing by aeolian sediment: field and remote-sensing investigation of aeolian-hillslope-fluvial interactions, Colorado River corridor, Arizona, USA

    USGS Publications Warehouse

    Sankey, Joel B.; Draut, Amy E.

    2014-01-01

    Processes contributing to development of ephemeral gully channels are of great importance to landscapes worldwide, and particularly in dryland regions where soil loss and land degradation from gully erosion pose long-term land-management problems. Whereas gully formation has been relatively well studied, much less is known of the processes that anneal gullies and impede their growth. This study of gully annealing by aeolian sediment, spanning 95 km along the Colorado River corridor in Glen, Marble, and Grand Canyon, Arizona, USA, employed field and remote sensing observations, including digital topographic modelling. Results indicate that aeolian sediment activity can be locally effective at counteracting gully erosion. Gullies are less prevalent in areas where surficial sediment undergoes active aeolian transport, and have a greater tendency to terminate in active aeolian sand. Although not common, examples exist in the record of historical imagery of gullies that underwent infilling by aeolian sediment in past decades and evidently were effectively annealed. We thus provide new evidence for a potentially important interaction of aeolian–hillslope–fluvial processes, which could affect dryland regions substantially in ways not widely recognized. Moreover, because the biologic soil crust plays an important role in determining aeolian sand activity, and so in turn the extent of gully development, this study highlights a critical role of geomorphic–ecologic interactions in determining arid-landscape evolution.

  1. Publication trends in Aeolian research: An analysis of the biblography of Aeolian research

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An analysis of the Bibliography of Aeolian Research has provided information regarding publication trends in aeolian research. Overall, results suggest that there has been a significant increase in the number of publications per year since the first aeolian-research publication appeared in 1646. P...

  2. Wireless Recording in the Peripheral Nervous System with Ultrasonic Neural Dust.

    PubMed

    Seo, Dongjin; Neely, Ryan M; Shen, Konlin; Singhal, Utkarsh; Alon, Elad; Rabaey, Jan M; Carmena, Jose M; Maharbiz, Michel M

    2016-08-01

    The emerging field of bioelectronic medicine seeks methods for deciphering and modulating electrophysiological activity in the body to attain therapeutic effects at target organs. Current approaches to interfacing with peripheral nerves and muscles rely heavily on wires, creating problems for chronic use, while emerging wireless approaches lack the size scalability necessary to interrogate small-diameter nerves. Furthermore, conventional electrode-based technologies lack the capability to record from nerves with high spatial resolution or to record independently from many discrete sites within a nerve bundle. Here, we demonstrate neural dust, a wireless and scalable ultrasonic backscatter system for powering and communicating with implanted bioelectronics. We show that ultrasound is effective at delivering power to mm-scale devices in tissue; likewise, passive, battery-less communication using backscatter enables high-fidelity transmission of electromyogram (EMG) and electroneurogram (ENG) signals from anesthetized rats. These results highlight the potential for an ultrasound-based neural interface system for advancing future bioelectronics-based therapies. PMID:27497221

  3. Temporal and spatial variations in provenance of Eastern Mediterranean Sea sediments: Implications for Aegean and Aeolian arc volcanism

    NASA Astrophysics Data System (ADS)

    Klaver, Martijn; Djuly, Thomas; de Graaf, Stefan; Sakes, Alex; Wijbrans, Jan; Davies, Gareth; Vroon, Pieter

    2015-03-01

    The Eastern Mediterranean Sea (EMS) is the last remnant of the Tethys Ocean that has been subducted to the north since the Jurassic. Subduction has led to the formation of multiple island arcs in the EMS region where the Aeolian and Aegean arcs are currently active. The EMS is surrounded by continents and receives a large sediment input, part of which is transported down with the subducting slab into the mantle and potentially contributes a major flux to the arc volcanism. An along-arc gradient in the composition of subducting sediment has been evoked to explain the distinct geochemical signature of the easternmost volcanic centre of the Aegean arc, but direct evidence for this proposal is lacking. We present a detailed study of the mineralogical, major-, trace elements and Sr-Nd-Hf-Pb isotope composition of 45 Neogene EMS sediment samples obtained from Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) drill sites and box cores to characterise their geochemical composition, distinguish provenance components and investigate the temporal and spatial variation in provenance to evaluate the potential changing contribution of subducted EMS sediment to Aegean and Aeolian arc volcanism. Based on trace element characteristics of EMS sediments, we can distinguish four provenance components. Nile sediment and Sahara dust are the main components, but contributions from the Tethyan ophiolite belt and arc volcanic rocks in the north are also recognised. Pliocene and Quaternary EMS sediment records a strong geochemical gradient where Nile River sediment entering the EMS in the east is progressively diluted by Sahara Desert dust towards the west. Pre-Messinian samples, however, have a remarkably homogeneous composition with Nile sediment characteristics. We relate this rapid increase in Sahara dust contribution to a late Miocene climate shift leading to decreased Nile runoff and aridification of the Sahara region. EMS sediment has a restricted range in Pb isotopes

  4. Using the significant dust deposition event on the glaciers of Mt. Elbrus, Caucasus Mountains, Russia on 5 May 2009 to develop a method for dating and provenancing of desert dust events recorded in snow pack

    NASA Astrophysics Data System (ADS)

    Shahgedanova, M.; Kutuzov, S.; White, K.; Nosenko, G.

    2012-09-01

    A significant desert dust deposition event occurred on Mt. Elbrus, Caucasus Mountains, Russia on 5 May 2009, where the deposited dust later appeared as a brown layer in the snow pack. An examination of dust transportation history and analysis of chemical and physical properties of the deposited dust were used to develop a new approach for high-resolution provenancing of dust deposition events recorded in snow pack using multiple independent techniques. A combination of SEVIRI red-green-blue composite imagery, MODIS atmospheric optical depth fields derived using the Deep Blue algorithm, air mass trajectories derived with HYSPLIT model and analysis of meteorological data enabled identification of dust source regions with high temporal (hours) and spatial (ca. 100 km) resolution. Dust, deposited on 5 May 2009, originated in the foothills of the Djebel Akhdar in eastern Libya where dust sources were activated by the intrusion of cold air from the Mediterranean Sea and Saharan low pressure system and transported to the Caucasus along the eastern Mediterranean coast, Syria and Turkey. Particles with an average diameter below 8 μm accounted for 90% of the measured particles in the sample with a mean of 3.58 μm, median 2.48 μm and the dominant mode of 0.60 μm. The chemical signature of this long-travelled dust was significantly different from the locally-produced dust and close to that of soils collected in a palaeolake in the source region, in concentrations of hematite and oxides of aluminium, manganese, and magnesium. Potential addition of dust from a secondary source in northern Mesopotamia introduced uncertainty in the provenancing of dust from this event. Nevertheless, the approach adopted here enables other dust horizons in the snowpack to be linked to specific dust transport events recorded in remote sensing and meteorological data archives.

  5. Using the significant dust deposition event on the glaciers of Mt.~Elbrus, Caucasus Mountains, Russia on 5 May 2009 to develop a method for dating and "provenancing" of desert dust events recorded in snow pack

    NASA Astrophysics Data System (ADS)

    Shahgedanova, M.; Kutuzov, S.; White, K. H.; Nosenko, G.

    2013-02-01

    A significant desert dust deposition event occurred on Mt. Elbrus, Caucasus Mountains, Russia on 5 May 2009, where the deposited dust later appeared as a brown layer in the snow pack. An examination of dust transportation history and analysis of chemical and physical properties of the deposited dust were used to develop a new approach for high-resolution "provenancing" of dust deposition events recorded in snow pack using multiple independent techniques. A combination of SEVIRI red-green-blue composite imagery, MODIS atmospheric optical depth fields derived using the Deep Blue algorithm, air mass trajectories derived with HYSPLIT model and analysis of meteorological data enabled identification of dust source regions with high temporal (hours) and spatial (ca. 100 km) resolution. Dust, deposited on 5 May 2009, originated in the foothills of the Djebel Akhdar in eastern Libya where dust sources were activated by the intrusion of cold air from the Mediterranean Sea and Saharan low pressure system and transported to the Caucasus along the eastern Mediterranean coast, Syria and Turkey. Particles with an average diameter below 8 μm accounted for 90% of the measured particles in the sample with a mean of 3.58 μm, median 2.48 μm. The chemical signature of this long-travelled dust was significantly different from the locally-produced dust and close to that of soils collected in a palaeolake in the source region, in concentrations of hematite. Potential addition of dust from a secondary source in northern Mesopotamia introduced uncertainty in the "provenancing" of dust from this event. Nevertheless, the approach adopted here enables other dust horizons in the snowpack to be linked to specific dust transport events recorded in remote sensing and meteorological data archives.

  6. "Dust Devils": Gardening Agents on the Surface of Mars, and Hidden Hazards to Human Exploration?

    NASA Technical Reports Server (NTRS)

    Marshall, J.; Smith, P.; White, B.; Farrell, W.

    1999-01-01

    Dust devils are familiar sites in the and regions of the world: they can produce quite spectacular displays of dust lofting when the vortices scavenge very loose dust from a dry lake bed or from recently disturbed agricultural fields. If one were to arrive at the center of an arid region, take one photograph, or even a series of photographs over a period of several days, then return the images for laboratory analysis, it would be most likely concluded that the region was inactive from an aeolian perspective. No images of general dust movement were obtained, nor were any dust devils "caught on camera" owing to their ephemeral and unpredictable appearance, and the fact that there was deceptively little residue of their actions. If, however, a camera were to take a 360 degree continuous recording over a period of a year, and the film were then to be shown at high speed over a period a several minutes, the impression might be that of a region ravaged by air vorticity and dust movement. Extrapolate this over geological time, and it is possible to visualize dust devils as prime aeolian agents, rather than insignificant vagaries of nature, On Mars, the thin atmosphere permits the surface of the planet to be heated but it does not itself retain heat with the capacity of the earth's atmosphere. This gives rise to greater thermal instability near the surface of Mars as "warm" air pockets diapiritically inject themselves into higher atmospheric layers. Resulting boundary-layer vorticity on Mars might therefore be expected to produce dust devils in abundance, if only seasonally. The spectacular images of dust devils obtained by Pathfinder within its brief functional period on the planet testify to the probability of highly frequent surface vorticity in light of the above reasoning about observational probability. Notably, the Pathfinder devils appeared to be at least a kilometer in height. There are several consequences for the geology of Mars, and for human exploration, if

  7. "Dust Devils": Gardening Agents on the Surface of Mars, and Hidden Hazards to Human Exploration?

    NASA Astrophysics Data System (ADS)

    Marshall, J.; Smith, P.; White, B.; Farrell, W.

    1999-09-01

    Dust devils are familiar sites in the and regions of the world: they can produce quite spectacular displays of dust lofting when the vortices scavenge very loose dust from a dry lake bed or from recently disturbed agricultural fields. If one were to arrive at the center of an arid region, take one photograph, or even a series of photographs over a period of several days, then return the images for laboratory analysis, it would be most likely concluded that the region was inactive from an aeolian perspective. No images of general dust movement were obtained, nor were any dust devils "caught on camera" owing to their ephemeral and unpredictable appearance, and the fact that there was deceptively little residue of their actions. If, however, a camera were to take a 360 degree continuous recording over a period of a year, and the film were then to be shown at high speed over a period a several minutes, the impression might be that of a region ravaged by air vorticity and dust movement. Extrapolate this over geological time, and it is possible to visualize dust devils as prime aeolian agents, rather than insignificant vagaries of nature, On Mars, the thin atmosphere permits the surface of the planet to be heated but it does not itself retain heat with the capacity of the earth's atmosphere. This gives rise to greater thermal instability near the surface of Mars as "warm" air pockets diapiritically inject themselves into higher atmospheric layers. Resulting boundary-layer vorticity on Mars might therefore be expected to produce dust devils in abundance, if only seasonally. The spectacular images of dust devils obtained by Pathfinder within its brief functional period on the planet testify to the probability of highly frequent surface vorticity in light of the above reasoning about observational probability. Notably, the Pathfinder devils appeared to be at least a kilometer in height. There are several consequences for the geology of Mars, and for human exploration, if

  8. Global dispersion of bacterial cells on Asian dust

    PubMed Central

    Yamaguchi, Nobuyasu; Ichijo, Tomoaki; Sakotani, Akiko; Baba, Takashi; Nasu, Masao

    2012-01-01

    The atmospheric dispersion of bacteria over long distances is an important facet of microbial ecology. Certain groups of dispersed bacteria can adapt to their new location and affect established ecosystems. Aeolian dust particles are known to be carriers of microbes but further research is needed to expand our understanding of this field of microbiology. Here we showed the potential of aeolian dust to global migration of bacterial cells. We demonstrated the presence of microbial cells on dust particles directly by bio-imaging. Bacterial abundance on dust particles declined from 105 to less than 103 cells/m3 as the dust event subsided. Taxonomically diverse bacteria were identified by 16S rRNA gene sequencing and some of these bacteria retained growth potential. Our results confirm that bacteria can attach to aeolian dust particles and they have the potential to migrate globally during dust events and thus can contribute to the diversity of downwind ecosystems. PMID:22826803

  9. Dust-climate couplings over the past 800,000 years from the EPICA Dome C ice core.

    PubMed

    Lambert, F; Delmonte, B; Petit, J R; Bigler, M; Kaufmann, P R; Hutterli, M A; Stocker, T F; Ruth, U; Steffensen, J P; Maggi, V

    2008-04-01

    Dust can affect the radiative balance of the atmosphere by absorbing or reflecting incoming solar radiation; it can also be a source of micronutrients, such as iron, to the ocean. It has been suggested that production, transport and deposition of dust is influenced by climatic changes on glacial-interglacial timescales. Here we present a high-resolution record of aeolian dust from the EPICA Dome C ice core in East Antarctica, which provides an undisturbed climate sequence over the past eight climatic cycles. We find that there is a significant correlation between dust flux and temperature records during glacial periods that is absent during interglacial periods. Our data suggest that dust flux is increasingly correlated with Antarctic temperature as the climate becomes colder. We interpret this as progressive coupling of the climates of Antarctic and lower latitudes. Limited changes in glacial-interglacial atmospheric transport time suggest that the sources and lifetime of dust are the main factors controlling the high glacial dust input. We propose that the observed approximately 25-fold increase in glacial dust flux over all eight glacial periods can be attributed to a strengthening of South American dust sources, together with a longer lifetime for atmospheric dust particles in the upper troposphere resulting from a reduced hydrological cycle during the ice ages. PMID:18385736

  10. Dust-climate couplings over the past 800,000 years from the EPICA Dome C ice core.

    PubMed

    Lambert, F; Delmonte, B; Petit, J R; Bigler, M; Kaufmann, P R; Hutterli, M A; Stocker, T F; Ruth, U; Steffensen, J P; Maggi, V

    2008-04-01

    Dust can affect the radiative balance of the atmosphere by absorbing or reflecting incoming solar radiation; it can also be a source of micronutrients, such as iron, to the ocean. It has been suggested that production, transport and deposition of dust is influenced by climatic changes on glacial-interglacial timescales. Here we present a high-resolution record of aeolian dust from the EPICA Dome C ice core in East Antarctica, which provides an undisturbed climate sequence over the past eight climatic cycles. We find that there is a significant correlation between dust flux and temperature records during glacial periods that is absent during interglacial periods. Our data suggest that dust flux is increasingly correlated with Antarctic temperature as the climate becomes colder. We interpret this as progressive coupling of the climates of Antarctic and lower latitudes. Limited changes in glacial-interglacial atmospheric transport time suggest that the sources and lifetime of dust are the main factors controlling the high glacial dust input. We propose that the observed approximately 25-fold increase in glacial dust flux over all eight glacial periods can be attributed to a strengthening of South American dust sources, together with a longer lifetime for atmospheric dust particles in the upper troposphere resulting from a reduced hydrological cycle during the ice ages.

  11. Surprises from the field: Novel aspects of aeolian saltation observed under natural turbulence

    NASA Astrophysics Data System (ADS)

    Martin, R. L.; Kok, J. F.; Chamecki, M.

    2015-12-01

    The mass flux of aeolian (wind-blown) sediment transport - critical for understanding earth and planetary geomorphology, dust generation, and soil stability - is difficult to predict. Recent work suggests that competing models for saltation (the characteristic hopping of aeolian sediment) fail because they do not adequately account for wind turbulence. To address this issue, we performed field deployments measuring high-frequency co-variations of aeolian saltation and near-surface winds at multiple sites under a range of conditions. Our observations yield several novel findings not currently captured by saltation models: (1) Saltation flux displays no significant lag relative to horizontal wind velocity; (2) Characteristic height of the saltation layer remains constant with changes in shear velocity; and (3) During saltation, the vertical profile of mean horizontal wind velocity is steeper than expected from the Reynolds stress. We examine how the interactions between saltation and turbulence in field settings could explain some of these surprising observations.

  12. Abrupt Late Holocene Shift in Atmospheric Circulation Recorded by Mineral Dust in the Siple Dome Ice Core, Antarctica

    NASA Astrophysics Data System (ADS)

    Koffman, B. G.; Goldstein, S. L.; Kaplan, M. R.; Winckler, G.; Bory, A. J. M.; Biscaye, P.

    2015-12-01

    Atmospheric dust directly influences Earth's climate by altering the radiative balance and by depositing micronutrients in the surface ocean, affecting global biogeochemical cycling. In addition, mineral dust particles provide observational evidence constraining past atmospheric circulation patterns. Because dust can originate from both local and distant terrestrial sources, knowledge of dust provenance can substantially inform our understanding of past climate history, atmospheric transport pathways, and differences in aerosol characteristics between glacial and interglacial climate states. Dust provenance information from Antarctic ice cores has until now been limited to sites in East Antarctica. Here we present some of the first provenance data from West Antarctica. We use Sr-Nd isotopes to characterize dust extracted from late Holocene ice (~1000-1800 C.E.) from the Siple Dome ice core. The data form a tight array in Sr-Nd isotope space, with 87Sr/86Sr ranging between ~0.7087 and 0.7102, and ɛNd ranging between ~ -7 and -16. This combination is unique for Antarctica, with low Nd and low Sr isotope ratios compared to high-elevation East Antarctic sites, requiring a dust source from ancient (Archean to early Proterozoic) and unweathered continental crust, which mixes with young volcanic material. Both components are likely sourced from Antarctica. We also observe significant, systematic variability in Sr and Nd isotopic signatures through time, reflecting changes in the mixing ratio of these sources, and hypothesize that these changes are driven by shifts in circulation patterns. A large change occurs over about 10 years at ca. 1125 C.E. (ΔɛNd = +3 and Δ87Sr/86Sr = -0.0014). This shift coincides with changes in climate proxies in Southern Hemisphere paleoclimate records reflecting variability in the Westerlies. We therefore interpret the shift in dust provenance at Siple Dome to be related to larger-scale circulation changes. In general, the observed shifts

  13. Potentials and problems of building detailed dust records using peat archives: An example from Store Mosse (the "Great Bog"), Sweden

    NASA Astrophysics Data System (ADS)

    Kylander, Malin E.; Martínez-Cortizas, Antonio; Bindler, Richard; Greenwood, Sarah L.; Mörth, Carl-Magnus; Rauch, Sebastien

    2016-10-01

    Mineral dust deposition is a process often overlooked in northern mid-latitudes, despite its potential effects on ecosystems. These areas are often peat-rich, providing ample material for the reconstruction of past changes in atmospheric deposition. The highly organic (up to 99% in some cases) matrix of atmospherically fed mires, however, makes studying the actual dust particles (grain size, mineralogy) challenging. Here we explore some of the potentials and problems of using geochemical data from conservative, lithogenic elements (Al, Ga, Rb, Sc, Y, Zr, Th, Ti and REE) to build detailed dust records by using an example from the 8900-yr peat sequence from Store Mosse (the "Great Bog"), which is the largest mire complex in the boreo-nemoral region of southern Sweden. The four dust events recorded at this site were elementally distinct, suggesting different dominant mineral hosts. The oldest and longest event (6385-5300 cal yr BP) sees a clear signal of clay input but with increasing contributions of mica, feldspar and middle-REE-rich phosphate minerals over time. These clays are likely transported from a long-distance source (<100 km). While dust deposition was reduced during the second event (5300-4370 cal yr BP), this is the most distinct in terms of its source character with [Eu/Eu∗]UCC revealing the input of plagioclase feldspar from a local source, possibly active during this stormier period. The third (2380-2200 cal yr BP) and fourth (1275-1080 cal yr BP) events are much shorter in duration and the presence of clays and heavy minerals is inferred. Elemental mass accumulation rates reflect these changes in mineralogy where the relative importance of the four dust events varies by element. The broad changes in major mineral hosts, grain size, source location and approximated net dust deposition rates observed in the earlier dust events of longer duration agree well with paleoclimatic changes observed in northern Europe. The two most recent dust events are much

  14. Cross-Spectral Comparison of Dust and Cosmogenic Nuclide Records from Greenland Ice Cores Demonstrate Synchronicity at Millennial Timescales

    NASA Astrophysics Data System (ADS)

    Balbas, A.; Cuzzone, J. K.; Mix, A. C.; Clark, P. U.

    2013-12-01

    Greenland ice core records of dust and cosmogenic nuclides, converted to flux, share a striking resemblance on millennial timescales. However, to date, the significance of the relationship between these two parameters has received little attention. Here, we compare records of 10Be, 36Cl, and dust spanning ~18ky to ~33ky from the GRIP and GISP2 ice cores using cross-spectral analysis. Our findings demonstrate a statistically robust relationship between the cosmogenic nuclide flux and the dust flux, revealing a common mode of in-phase variability with a period of ~1600 years and coincident with the Northern Hemisphere Dansgaard-Oeschger events. Millennial-scale variability in cosmogenic nuclides from Greenland ice cores is commonly attributed to solar variability while variations in Greenland dust concentrations are associated with changes in atmospheric circulation, but why these two processes would co-vary remains unclear. We suggest that circulation could also act as a previously unrecognized control on cosmogenic nuclide fluxes, whereby variable mixing between the troposphere and stratosphere could explain the portion of the observed millennial-scale variability which cannot be explained by solar variability alone. Our proposed mechanism invokes changes in atmospheric mixing due to upper level (troposphere-stratosphere boundary) wind shear, which climate models predict may change during climate changes as a result of baroclinic variability. GCM simulations suggest that changes in baroclinicity between the LGM and present day lead to changes in the upper level jet velocities (500mb), which in turn, affect the vertical wind shear at upper levels (200-300mb). Because dust deposition scales closely with changes in wind velocity and chemical constituent exchange from the stratosphere to the troposphere is largely a function of jet proximal clear air turbulence provoked by instabilities in vertical shear, the Greenland dust and cosmogenic records may be particularly

  15. The birth and death of transverse aeolian ridges on Mars

    USGS Publications Warehouse

    Geissler, Paul E.

    2014-01-01

    Transverse aeolian ridges (TARs) are small bright windblown deposits found throughout the Martian tropics that stand a few meters tall and are spaced a few tens of meters apart. The origin of these features remains mysterious more than 20 years after their discovery on Mars. This paper presents a new hypothesis, that some of the TARs could be indurated dust deposits emplaced millions of years ago during periods of higher axial obliquity. It suggests that these TARs are primary depositional bed forms that accumulated in place from dust carried by the winds in suspension, perhaps in a manner comparable to antidunes on Earth, and were subsequently indurated and eroded to their current states by eons of sandblasting. It points out examples of modern dust drifts and dune-like features that appear to have been recently formed by dust accumulating directly onto the surface from atmospheric suspension. It shows how these pristine dust deposits could evolve to explain the range of morphologies of the TARs. Finally, it explains how the known properties of many TARs are consistent with this hypothesis, including their composition, thermal behavior, and distribution.

  16. Aeolian Processes at the Mars Exploration Rover Opportunity Landing Site

    NASA Technical Reports Server (NTRS)

    Sullivan, R.; Bell, J. F., III; Calvin, W.; Fike, D.; Golombek, M.; Greeley, R.; Grotzinger, J.; Herkenhoff, K.; Jerolmack, D.; Malin, M.

    2005-01-01

    The traverse of the Mars Exploration Rover Opportunity across its Meridiani Planum landing site has shown that wind has affected regolith by creating drifts, dunes, and ubiquitous ripples, by sorting grains during aeolian transport, by forming bright wind streaks downwind from craters seen from orbit, and by eroding rock with abrading, wind-blown material. Pre-landing orbiter observations showed bright and dark streaks tapering away from craters on the Meridiani plains. Further analysis of orbiter images shows that major dust storms can cause bright streak orientations in the area to alternate between NW and SE, implying bright wind streak materials encountered by Opportunity are transient, potentially mobilized deposits. Opportunity performed the first in situ investigation of a martian wind streak, focusing on a bright patch of material just outside the rim of Eagle crater. Data from Pancam, the Miniature Thermal Emission Spectrometer (Mini-TES), the Alpha-Particle X-Ray Spectrometer (APXS), and the Mossbauer spectrometer either are consistent with or permit an air fall dust interpretation. We conclude that air fall dust, deposited in the partial wind shadow of Eagle crater, is responsible for the bright streak seen from orbit, consistent with models involving patchy, discontinuous deposits of air fall dust distributed behind obstacles during periods of atmospheric thermal stability during major dust storms.

  17. Aeolian deposition and its effect on soil and vegetation changes on stabilised desert dunes in northern China

    NASA Astrophysics Data System (ADS)

    Fearnehough, W.; Fullen, M. A.; Mitchell, D. J.; Trueman, I. C.; Zhang, J.

    1998-06-01

    Spatial and temporal patterns of aeolian deposition at Shapotou, northern China, were studied on a chronosequence (0, 12, 29 and 37 years) of stabilised desert dunes. Aeolian deposition markedly influenced soil and vegetation changes on the dunes. The spatial pattern of aeolian deposition was studied using dust traps and measurements of the depth of aeolian accumulation. Mean deposition from August 1993 to July 1994 was 372 g/m 2, and showed a complex spatial pattern, determined by prevailing wind direction, topography and shrub distribution. Contrasts between the topographic pattern of aeolian deposition (trap data) and accumulation (thickness of aeolian deposits) indicate that the measured pattern of aeolian deposition alone is insufficient to explain the pattern of accumulation. An accretionary surface soil or `grey sand' (containing much aeolian-derived particles) is developing on the stabilised dunes at a mean rate of 1.6 mm/year. Rapid accumulation of aeolian particles significantly changed the surface environment. Increased moisture retention by the finer `grey sand' resulted in decreased moisture penetration and subsequent desiccation of the deeper dune sands. This has led to vegetation changes, with the deep-rooted, planted xerophytic shrubs declining from 12 to only 3% cover after 37 years of stabilisation. The shrubs were replaced by a widespread microphytic crust and later by shallow-rooted annual species, which increased from 0 to approximately 12% cover over the same period. The implications of projected increases in the dustiness of arid regions on the stability of desert dunes and vegetated desert margins are discussed. Stabilised dunes may become increasingly vulnerable to deflation with the progressive decline in shrub cover.

  18. The characterization and role of aeolian deposition on water quality, McMurdo Dry Valleys, Antarctica

    NASA Astrophysics Data System (ADS)

    Deuerling, K. M.; Lyons, W. B.; Welch, S. A.; Welch, K. A.

    2014-06-01

    The connection of ecosystems by wind-driven transport of material has become a topic of increasing interest and importance. Less than 1% of dust transported worldwide is exported to the Southern Ocean and Antarctic cryosphere; however, aeolian transport on the Antarctic continent is predominantly locally derived from the abrasion of bedrock. The deposition of the aeolian material is integral to nutrient and solute dispersal in the Antarctic ecosystem. This is particularly true in the ice-free areas of Antarctica, such as the McMurdo Dry Valleys (MDV), where aeolian material deposited in the aquatic system is solubilized during the melt season. The material is predominantly locally-derived from the abrasion of bedrock. In this study, a two-step leaching experiment simulates the melt season and we quantify the flux of solutes and nutrients to the aquatic ecosystem. Soluble salts were removed from the aeolian material first during cold water leaching followed by an increase in carbonate and silicate dissolution during freeze-thaw. Major ion fluxes on glaciers and lakes are at least two orders of magnitude greater than nutrient fluxes. However, the fluxes derived from these experiments are less than the estimated flux from streams to lakes and probably represent minima. Aeolian redistribution of local soils is important because they are the only source of new solutes and nutrients to the aquatic ecosystem of the MDV.

  19. Mineralogical controls on dust emissions in the Bodele Depression, Chad

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surface mineralogy is critical in the understanding of aeolian processes, however its role in dust production is currently underestimated. Recent research indicates that discrepancies between predicted and observed dust loads by dust models may be attributed to inadequacies within their associated d...

  20. Hydrological indications of aeolian salts in mid-latitude deserts of northwestern China

    NASA Astrophysics Data System (ADS)

    Zhu, Bing-Qi

    2016-06-01

    Large sandy deserts in middle latitude of northwestern China were studied on salt variations in modern and ancient aeolian sediments, aiming to explore their hydrological indications at the present and past. Globally, sulphate is rich in arid to semi-arid deserts, including the aeolian loess sediments in China and soils in low-latitude deserts, but is less common in the aeolian sediments from the mid-latitude deserts in this study. The compositional differences between aeolian salts and local natural waters is evident, indicating the chemistry of aeolian salts and the associated parent brines may be significantly different than that predicted for hydrologically closed systems. The formation of aeolian salts in the studied deserts is strongly controlled by earth surface processes in a large scale but not in a local scale. Vertical changes in facies and salinities are abrupt in the studied palaeo-aeolian sediment samples, which were interbedded by lacustrine/fluvial sediments with OSL and 14C ages ranging between 40 and 2 ka BP, reflecting rapid high-amplitude changes in hydrological settings during late Pleistocene to later Holocene in these ancient playa systems. A great difference in salt composition between aeolian and lacustrine sediments suggests that the inorganic salt is a latent geoproxy in revealing local hydrological variations and climate change in the desert areas. But the environmental indications could be amphibolous for the sedimentary sequences with dual/multiple depositional end-members; under this situation an increase in sequence salinity does not always represent an enhanced environmental aridity. Ancient playas are arid or humid at the same time based on several sporadic records is not a valid approach to correlation of salt deposits in adjacent saline playa basin in the studied areas. Effects of earth surface processes including erosion, deposition and other processes on sediment properties will bias the hydrological implications of sediment

  1. Mars Aeolian Features and Processes Observed Concurrently From Orbit and the Ground

    NASA Astrophysics Data System (ADS)

    Greeley, R.; Arvidson, R.; Cabrol, N.; Christensen, P.; de Souza, P.; Geissler, P.; Goetz, W.; Landis, G.; Lemmon, M.; Malin, M.; McEwen, A.; Neukum, G.; Pendleton Hoffer, M.; Squyres, S.; Sullivan, R.; Waller, D.; Williams, D.

    2008-12-01

    , revealed by Spirit to be composed of grains larger than a few hundred microns in diameter. Imaging of Spirit's deck after periods of aeolian activity showed the presence of similar grains, as well as the bounce marks of their passage in the deposited dust suggesting emplacement by saltation; showing that at least some sands currently are active. This interpretation was verified by a sequence of images from Spirit which showed active movement of small ripples across the surface. Despite these results, questions remain regarding current versus relict aeolian features, and the specific pathways of aeolian transport in complex terrains, such as the Columbia Hills in Gusev crater. These questions are being addressed through current research and the acquisition of new data from both the ground and orbit.

  2. Aeolian sand preserved in Silver Lake: a new signal of Holocene high stands of Lake Michigan

    USGS Publications Warehouse

    Fisher, Timothy G.; Loope, Walter L.

    2005-01-01

    Aeolian sand within lake sediment from Silver Lake, Michigan can be used as a proxy for the timing of high lake levels of Lake Michigan.We demonstrate that the sand record from Silver Lake plotted as percent weight is in-phase with the elevation curve of Lake Michigan since the mid-Holocene Nipissing Phase. Because fluctuations in Lake Michigan's lake level are recorded in beach ridges, and are a response to climate change, the aeolian sand record within Silver Lake is also a proxy for climate change. It appears that increases in dune activity and lake sand are controlled by similar climatic shifts that drive fluctuations in lake level of Lake Michigan. High lake levels destabilize coastal bluffs that drive dune sand instability, and along with greater wintertime storminess, increase niveo-aeolian transport of sand across lake ice. The sand is introduced into the lake each spring as the ice cover melts.

  3. Laboratory studies of aeolian sediment transport processes on planetary surfaces

    NASA Astrophysics Data System (ADS)

    Rasmussen, Keld R.; Valance, Alexandre; Merrison, Jonathan

    2015-09-01

    We review selected experimental saltation studies performed in laboratory wind tunnels and collision experiments performed in (splash-) laboratory facilities that allow detailed observations between impinging particles on a stationary bed. We also discuss progress in understanding aeolian transport in nonterrestrial environments. Saltation studies in terrestrial wind tunnels can be divided into two groups. The first group comprises studies using a short test bed, typically 1-4 m long, and focuses on the transitional behavior near the upwind roughness discontinuity where saltation starts. The other group focuses on studies using long test beds - typically 6 m or more - where the saturated saltation takes place under equilibrium conditions between wind flow and the underlying rough bed. Splash studies using upscaled model experiments allow collision simulations with large spherical particles to be recorded with a high speed video camera. The findings indicate that the number of ejected particles per impact scales linearly with the impact velocity of the saltating particles. Studies of saturated saltation in several facilities using predominantly Particle Tracking Velocimetry or Laser Doppler Velocimetry indicate that the velocity of the (few) particles having high trajectories increases with increasing friction velocity. However, the speed of the majority of particles that do not reach much higher than Bagnold's focal point is virtually independent of Shields parameter - at least for low or intermediate u*-values. In this case mass flux depends on friction velocity squared and not cubed as originally suggested by Bagnold. Over short beds particle velocity shows stronger dependence on friction velocity and profiles of particle velocity deviate from those obtained over long beds. Measurements using horizontally segmented traps give average saltation jump-lengths near 60-70 mm and appear to be only weakly dependent on friction velocity, which is in agreement with some

  4. High-Resolution Dust record of last glacial period (MIS 4 to MIS 2) from Talos Dome Ice Core

    NASA Astrophysics Data System (ADS)

    Mazzola, Claudia; Maggi, Valter; Delmonte, Barbara; Marino, Federica; Albani, Samuel

    2010-05-01

    Mineral dust trapped in Antarctic ice cores plays an important role in the study of past climate and atmospheric circulation variability in the Southern Hemisphere. In this work we investigate the Talos Dome (Northern Victoria Land, East Antarctica) ice core dust concentration record through a Laser Sensor (LS) technique. Analyses were performed in continuous as a part of the Continuous Flow Analysis (CFA) system, and discontinuously with Beckman Coulter©Counter for comparison and LS calibration. The LS device provided two basic outputs: (1) "bag" (1 m long sections) mean values and (2) high resolution (1 cm resolution) data. Both signals were processed in the contest of this work and two dust records, respectively at low and high resolution, were produced. Here we report the bag mean dust record from the end of the last deglaciation (about 12,000 years B.P.) to Marine Isotopic Stage 4 (MIS 4, 70,000 years BP). The comparison of the TALDICE LS and EPICA-Dome C dust record provides interesting information about climatic conditions of South Pacific-Ross Sea sector of Antarctica, and atmospheric circulation patterns during last glacial period, with a good agreement between MIS 3 and Last Glacial Maximum (LGM), where several millennial and plurimillennial scale climatic oscillation are observed. For these reasons it is possible suppose that dust transport mechanisms towards TD and DC were the same during the last glacial period. However, MIS 4 in TD ice core was lower, both in concentration and flux, compared to EDC. Likely, during LGM, very cool air masses extended above the Antarctic plateau, even in TD area, have created a subsidence condition which haven't allowed the cyclonic perturbation to penetrate the interior of Antarctica continent. In fact, the Polar Front has moved towards lower latitude in that period, maintaining far away the disturbances. These preliminary observations suggest that the coupling between inner sites such as EDC and the Talos Dome

  5. Semiarid landscapes response to Aeolian processes during Holocene in Baikal Region

    NASA Astrophysics Data System (ADS)

    Dan'ko, Lidia; Opekunova, Marina

    2010-05-01

    Arid and semiarid landscapes play a significant role in global climate, biogeochemical, and hydrological processes. Regional analysis of the past aeolian processes is essential for improve our understanding of how various landscape and ecosystems responded to climate change in the past. Our investigation presents details on sand dunes and on loess-like sediments. The study areas are situated in the northern part of Baikal Region (Eastern Siberia). In its depressions, the so-called Barguzinskaya and Tunkinskaya Valley surrounded mountain ranges local dunefieds and loess-like sediments have developed. Present climate in the study areas is continental, characterized by low precipitation(mean annual 250-450 mm) and wide annual range of temperature. Field investigations indicate that the Holocene deposits of the Barguzinskaya and Tunkinskaya Valley are sealed the pedo-sedimentary interface. The analytical results suggest that one's represents a changeover from intensified soil formation to accelerated aeolian dust accumulation. The original content of calcium carbonate and gypsum at the base of some sections of loess-like sediments indicates the aeolian origin of these sediments. In whole, the soil horizons are a proof for humid phases. The change was forced by climatic aridity. Absolute dating of the organogenic components of soils (14C) indicate the age positions of the arid and humid climate phases. Our results indicate not only 1-4 long-time episodes of aeolian dust accumulation during the Holocene, but shot-time aeolian accumulation episodes, that were specific for Late Holocene. For example, in the Tunkinskaya Valley the Late Holocene soil formation replaced by aeolian deposit at 1700 - 1900, 800 and 200-250 years ago, in the Barguzinskaya Valley - about 3100 - 2900, 2300 and 600 years ago. It can be concluded that a periodical formation of the aeolian deposits in the semiarid landscapes during Holocene can be postulated. Aeolian and loess-like sediments of the

  6. Comminution of Aeolian Materials on Mars

    NASA Technical Reports Server (NTRS)

    Marshall, John R.

    1998-01-01

    The research task had a two-year performance period for the investigation of aeolian processes on Mars. Specifically, we were investigating the comminution of sand grains as individual particles, and as bulk populations. Laboratory experiment were completed for the individual particles, and results led to new theory for aeolian transport that is broadly applicable to all planetary surfaces. The theory was presented at the LPSC and the GSA in 1998 and 1997 respectively. Essentially, the new theory postulates that aeolian transport is dependent upon two motion thresholds- an aerodynamic threshold and a bed-dilatancy threshold.

  7. Bursts in discontinuous Aeolian saltation

    PubMed Central

    Carneiro, M. V.; Rasmussen, K. R.; Herrmann, H. J.

    2015-01-01

    Close to the onset of Aeolian particle transport through saltation we find in wind tunnel experiments a regime of discontinuous flux characterized by bursts of activity. Scaling laws are observed in the time delay between each burst and in the measurements of the wind fluctuations at the fluid threshold Shields number θc. The time delay between each burst decreases on average with the increase of the Shields number until sand flux becomes continuous. A numerical model for saltation including the wind-entrainment from the turbulent fluctuations can reproduce these observations and gives insight about their origin. We present here also for the first time measurements showing that with feeding it becomes possible to sustain discontinuous flux even below the fluid threshold. PMID:26073305

  8. Flood Induced Increases in Aeolian Transport Along the Missouri River

    NASA Astrophysics Data System (ADS)

    Benthem, A. J.; Strong, L.; Schenk, E.; Skalak, K.; Hupp, C. R.; Galloway, J.

    2014-12-01

    In 2011, heavy winter snow melt combined with extensive spring rains caused the Missouri River to experience the most extensive flooding since the river was dammed in the 1950s. Large sections of the river banks, islands, and floodplains experienced weeks of prolonged inundation, resulting in extensive sand deposition as up to1 km inland from the established channel. Though locally variable, deposits of up to 3m of loose sand were deposited on the floodplain and extensive areas of shrub, grasslands, and agricultural fields were completely buried or had vegetation washed away in the inundation zone. The flooding also created a number of new unvegetated islands which provide important habitat for endangered species including the Piping Plover (Charadrius melodus). These newly created sand surfaces are unconsolidated and have very little vegetation to prevent aeolian transport. Strong sustained regional winds of up to 20m/s (45mph) cause substantial sediment fluxes which modify landscape topography, shift river morphology, and increase regional dust levels. Our study monitors and quantifies the increase in aeolian transport that occurred following flooding along the Garrison Reach, a 110 km section of free flowing Missouri River in North Dakota. In 2012 and 2013 we measured sand transport and accumulation rates using Leatherman style sand traps and erosion pins to at 9 sites of varying vegetation densities. We apply these flux rates to a high resolution remote sensing vegetation map to estimate the total flux of sand for this segment of the river. We also quantify total available new sand for transport using repeat Light Detection and Ranging (LiDAR) coverage from before and after the flood and examine the relationship between sand deposition and the rate of reestablishment of vegetation. All of these results are used to estimate the scale of flood induced aeolian processes and predict where they may continue to influence the landscape.

  9. Cold surges and dust events: Establishing the link between the East Asian Winter Monsoon and the Chinese loess record

    NASA Astrophysics Data System (ADS)

    Wyrwoll, Karl-Heinz; Wei, Junhong; Lin, Zhaohui; Shao, Yaping; He, Feng

    2016-10-01

    The Chinese loess/palaeosol succession is one of the most comprehensive and intensively studied archives of Neogene and Quaternary global palaeoclimate events. Its stratigraphic details are widely recognised to indicate close links to the history and function of the East Asian Winter Monsoon (EAWM) - one of the most active components of the Earth's climate system. But the formal meteorological links between the EAWM and dust emission, both in the present day and in the past, have not been established and with it, the veracity of the loess record as an indicator of the EAWM questioned. Here we show that present day major dust events over northern China, while largely occurring during spring, are nevertheless 'conditioned' by the strength of the preceding EAWM. We also demonstrate, for the first time, a close link between the occurrence of dust events and the strength of the EAWM. From these findings, linked to global-scale climate model simulations, we conclude that the Chinese loess succession provides a convincing proxy record of the strength of the East Asian Winter Monsoon.

  10. Evaluation of a new model of aeolian transport in the presence of vegetation

    USGS Publications Warehouse

    Li, Junran; Okin, Gregory S.; Herrick, Jeffrey E.; Belnap, Jayne; Miller, Mark E.; Vest, Kimberly; Draut, Amy E.

    2013-01-01

    Aeolian transport is an important characteristic of many arid and semiarid regions worldwide that affects dust emission and ecosystem processes. The purpose of this paper is to evaluate a recent model of aeolian transport in the presence of vegetation. This approach differs from previous models by accounting for how vegetation affects the distribution of shear velocity on the surface rather than merely calculating the average effect of vegetation on surface shear velocity or simply using empirical relationships. Vegetation, soil, and meteorological data at 65 field sites with measurements of horizontal aeolian flux were collected from the Western United States. Measured fluxes were tested against modeled values to evaluate model performance, to obtain a set of optimum model parameters, and to estimate the uncertainty in these parameters. The same field data were used to model horizontal aeolian flux using three other schemes. Our results show that the model can predict horizontal aeolian flux with an approximate relative error of 2.1 and that further empirical corrections can reduce the approximate relative error to 1.0. The level of error is within what would be expected given uncertainties in threshold shear velocity and wind speed at our sites. The model outperforms the alternative schemes both in terms of approximate relative error and the number of sites at which threshold shear velocity was exceeded. These results lend support to an understanding of the physics of aeolian transport in which (1) vegetation's impact on transport is dependent upon the distribution of vegetation rather than merely its average lateral cover and (2) vegetation impacts surface shear stress locally by depressing it in the immediate lee of plants rather than by changing the bulk surface's threshold shear velocity. Our results also suggest that threshold shear velocity is exceeded more than might be estimated by single measurements of threshold shear stress and roughness length

  11. Evaluation of a new model of aeolian transport in the presence of vegetation

    NASA Astrophysics Data System (ADS)

    Li, Junran; Okin, Gregory S.; Herrick, Jeffrey E.; Belnap, Jayne; Miller, Mark E.; Vest, Kimberly; Draut, Amy E.

    2013-03-01

    Aeolian transport is an important characteristic of many arid and semiarid regions worldwide that affects dust emission and ecosystem processes. The purpose of this paper is to evaluate a recent model of aeolian transport in the presence of vegetation. This approach differs from previous models by accounting for how vegetation affects the distribution of shear velocity on the surface rather than merely calculating the average effect of vegetation on surface shear velocity or simply using empirical relationships. Vegetation, soil, and meteorological data at 65 field sites with measurements of horizontal aeolian flux were collected from the Western United States. Measured fluxes were tested against modeled values to evaluate model performance, to obtain a set of optimum model parameters, and to estimate the uncertainty in these parameters. The same field data were used to model horizontal aeolian flux using three other schemes. Our results show that the model can predict horizontal aeolian flux with an approximate relative error of 2.1 and that further empirical corrections can reduce the approximate relative error to 1.0. The level of error is within what would be expected given uncertainties in threshold shear velocity and wind speed at our sites. The model outperforms the alternative schemes both in terms of approximate relative error and the number of sites at which threshold shear velocity was exceeded. These results lend support to an understanding of the physics of aeolian transport in which (1) vegetation's impact on transport is dependent upon the distribution of vegetation rather than merely its average lateral cover and (2) vegetation impacts surface shear stress locally by depressing it in the immediate lee of plants rather than by changing the bulk surface's threshold shear velocity. Our results also suggest that threshold shear velocity is exceeded more than might be estimated by single measurements of threshold shear stress and roughness length

  12. Reduction in soil aggregation in response to dust emission processes

    NASA Astrophysics Data System (ADS)

    Swet, Nitzan; Katra, Itzhak

    2016-09-01

    Dust emission by aeolian (wind) soil erosion depends on the topsoil properties of the source area, especially on the nature of the aggregates where most dust particles are held. Although the key role of soil aggregates in dust emission, the response of soil aggregation to aeolian processes and its implications for dust emission remain unknown. This study focuses on aggregate size distribution (ASD) analyses before and after in-situ aeolian experiments in semiarid loess soils that are associated with dust emission. Wind tunnel simulations show that particulate matter (PM) emission and saltation rates depend on the initial ASD and shear velocity. Under all initial ASD conditions, the content of saltator-sized aggregates (63-250 μm) increased by 10-34% due to erosion of macro-aggregates (> 500 μm), resulting in a higher size ratio (SR) between the saltators and macro-aggregates following the aeolian erosion. The results revealed that the saltator production increases significantly for soils that are subjected to short-term (anthropogenic) disturbance of the topsoil. The findings highlight a decrease in soil aggregation for all initial ASD's in response to aeolian erosion, and consequently its influence on the dust emission potential. Changes in ASD should be considered as a key parameter in dust emission models of complex surfaces.

  13. The historical record of air pollution as defined by attic dust

    NASA Astrophysics Data System (ADS)

    Ilacqua, Vito; Freeman, Natalie C. J.; Fagliano, Jerald; Lioy, Paul J.

    The use of undisturbed attic dust as a tool for reconstructing historical air pollution was evaluated in this study. Dust collected from the attic of 201 houses in New Jersey, built between 1879 and 1995, was analyzed for lead with ICP-MS to validate the use of this method. The results were matched to an estimated pattern of the lead concentrations in attic dust, that was based upon historical data on lead gasoline consumption and emissions into the ambient air. In spite of the numerous uncertainties implied in such a comparison, the pattern of lead concentrations found in the attic dust approximated, within intervals of about 10 years, the time course of the lead emissions into the air. 137Cs concentrations were measured in the attic dust samples using gamma spectrometry to investigate the possibility of a local source contaminating the ambient air in Dover Township, NJ. No statistical differences in 137Cesium concentrations were found between the attics in Dover Township and other locations in NJ. The 137Cs concentrations measured in all locations were found to increase with the age of the house. The observed dependence of 137Cs concentrations on the age of the house could be explained primarily by the patterns of radionuclide fallout that has occurred over time because of above ground nuclear weapons testing during the 1950s and 1960s.

  14. Aeolian cliff-top deposits and buried soils in the White River Badlands, South Dakota, USA

    USGS Publications Warehouse

    Rawling, J. E.; Fredlund, G.G.; Mahan, S.

    2003-01-01

    Aeolian deposits in the North American Great Plains are important sources of Holocene palaeo-environmental records. Although there are extensive studies on loess and dune records in the region, little is known about records in aeolian cliff-top deposits. These are common on table (mesa) edges in the White River Badlands. These sediments typically have loam and sandy-loam textures with dominantly very fine sand, 0.5-1% organic carbon and 0.5-5% CaCO3. Some of these aeolian deposits are atypically coarse and contain granules and fine pebbles. Buried soils within these deposits are weakly developed with A-C and A-AC-C profiles. Beneath these are buried soils with varying degrees of pedogenic development formed in fluvial, aeolian or colluvial deposits. Thickness and number of buried soils vary. However, late-Holocene soils from several localities have ages of approximately 1300, 2500 and 3700 14C yrs BP. The 1300 14C yr BP soil is cumulic, with a thicker and lighter A horizon. Soils beneath the cliff-top deposits are early-Holocene (typically 7900 but as old as 10000 14C yrs BP) at higher elevation (???950 m) tables, and late-Holocene (2900 14C yrs BP) at lower (???830 m) tables. These age estimates are based on total organic matter 14C ages from the top 5 cm of buried soils, and agreement is good between an infrared stimulated luminescence age and bracketing 14C ages. Our studies show that cliff-top aeolian deposits have a history similar to that of other aeolian deposits on the Great Plains, and they are another source of palaeoenvironmental data.

  15. Dust storms on Mars: Considerations and simulations

    NASA Technical Reports Server (NTRS)

    Greeley, R.; White, B. R.; Pollack, J. B.; Iverson, J. D.; Leach, R. N.

    1977-01-01

    Aeolian processes are important in modifying the surface of Mars at present, and appear to have been significant in the geological past. Aeolian activity includes local and global dust storms, the formation of erosional features such as yardangs and depositional features such as sand dunes, and the erosion of rock and soil. As a means of understanding aeolian processes on Mars, an investigation is in progress that includes laboratory simulations, field studies of earth analogs, and interpretation of spacecraft data. This report describes the Martian Surface Wind Tunnel, an experimental facility established at NASA-Ames Research Center, and presents some results of the general investigation. Experiments dealing with wind speeds and other conditions required for the initiation of particle movement on Mars are described and considerations are given to the resulting effectiveness of aeolian erosion.

  16. The bioavailable iron in NEEM ice core related to Asian dust records over the past 110 kyr

    NASA Astrophysics Data System (ADS)

    Xiao, Cunde

    2016-04-01

    The mineral dust can indirectly affect climate by supplying iron and other essential bioavailable elements into ocean. In this study, we present dissolved iron (DFe) and total dissolved iron (TDFe) concentrations in NEEM ice core over the past 110 kyr B.P. The concentrations of bioavailable reactive element Fe have good positive correlation with the concentrations of dust and Ca2+ in NEEM ice core, while show significantly negative relationship with δ18O and CO2 concentration. The ratios of DFe/TDFe are higher in warm periods (Holocene and last interglacial) than in cold period (LGM), indicating the iron-biological pump effect is more significant in warm periods than that in cold periods, this result may provide a new insight for reevaluating the iron hypothesis over glacial/interglacial periods. Our study also shows that the iron flux changes between NEEM ice core and Asian loess records are good consistent with the northern Hemisphere summer insolation. These results emphasize that the variability of Fe flux is most likely driven by solar radiation and dust in northern hemisphere.

  17. Persistent aeolian activity at Endeavour crater, Meridiani Planum, Mars; new observations from orbit and the surface

    NASA Astrophysics Data System (ADS)

    Chojnacki, Matthew; Johnson, Jeffrey R.; Moersch, Jeffrey E.; Fenton, Lori K.; Michaels, Timothy I.; Bell, James F., III

    2015-05-01

    Aeolian-driven bedform activity is now known to occur in many regions of Mars, based on surface and orbital observation of contemporary martian ripple and dune mobility events. Many of these sites have only been monitored with sufficient resolution data for the last few Mars years, when the High Resolution Imaging Science Experiment (HiRISE) began acquiring images of Mars. One exception is the well-monitored Endeavour crater in Meridiani Planum, which was one of the first known sites of unambiguous dune activity (migration and deflation). However, those early detections used lower resolution images over longer temporal baselines (versus the HIRISE data now available), leaving some measurements poorly constrained. New orbital and surface observations of Endeavour show multiple spatial (cm, m, km) and temporal (seasons, Mars year) scales of aeolian-driven surface change, which confirms earlier reports. Dome dunes in the eastern portion of the crater persistently deflate, disseminating dark sand across lighter-toned regolith and/or eroded bright dust, and likely contribute to the crater interior's episodic decreases in orbital albedo measurements. Other dome dunes are detected with the highest migration rates (4-12 m per Mars year) and volumetric sand fluxes reported yet for Mars. Estimated dune construction times or "turnover times" here and elsewhere on Mars are significantly shorter than martian obliquity cycles, implying that it is not necessary to invoke paleoclimate wind regimes to explain current dune morphologies. Located on the crater rim, the Opportunity rover detected evidence for near- and far-field aeolian-driven activity, with observations of spherules/sand movement in the rover workspace, bedform albedo alteration, and dust-lifting events. Observations of intracrater dunes show periodic shifting dark streaks that significantly constrain local wind regimes (directionality and seasonality). Constraints on wind directions from surface and orbital images

  18. Historic records of organic compounds from a high Alpine glacier: influences of biomass burning, anthropogenic emissions, and dust transport

    NASA Astrophysics Data System (ADS)

    Müller-Tautges, C.; Eichler, A.; Schwikowski, M.; Pezzatti, G. B.; Conedera, M.; Hoffmann, T.

    2016-01-01

    Historic records of α-dicarbonyls (glyoxal, methylglyoxal), carboxylic acids (C6-C12 dicarboxylic acids, pinic acid, p-hydroxybenzoic acid, phthalic acid, 4-methylphthalic acid), and ions (oxalate, formate, calcium) were determined with annual resolution in an ice core from Grenzgletscher in the southern Swiss Alps, covering the time period from 1942 to 1993. Chemical analysis of the organic compounds was conducted using ultra-high-performance liquid chromatography (UHPLC) coupled to electrospray ionization high-resolution mass spectrometry (ESI-HRMS) for dicarbonyls and long-chain carboxylic acids and ion chromatography for short-chain carboxylates. Long-term records of the carboxylic acids and dicarbonyls, as well as their source apportionment, are reported for western Europe. This is the first study comprising long-term trends of dicarbonyls and long-chain dicarboxylic acids (C6-C12) in Alpine precipitation. Source assignment of the organic species present in the ice core was performed using principal component analysis. Our results suggest biomass burning, anthropogenic emissions, and transport of mineral dust to be the main parameters influencing the concentration of organic compounds. Ice core records of several highly correlated compounds (e.g., p-hydroxybenzoic acid, pinic acid, pimelic, and suberic acids) can be related to the forest fire history in southern Switzerland. P-hydroxybenzoic acid was found to be the best organic fire tracer in the study area, revealing the highest correlation with the burned area from fires. Historical records of methylglyoxal, phthalic acid, and dicarboxylic acids adipic acid, sebacic acid, and dodecanedioic acid are comparable with that of anthropogenic emissions of volatile organic compounds (VOCs). The small organic acids, oxalic acid and formic acid, are both highly correlated with calcium, suggesting their records to be affected by changing mineral dust transport to the drilling site.

  19. Triton's streaks as windblown dust

    NASA Technical Reports Server (NTRS)

    Sagan, Carl; Chyba, Christopher

    1990-01-01

    Explanations for the surface streaks observed by Voyager 2 on Triton's southern hemisphere are discussed. It is shown that, despite Triton's tenuous atmosphere, low-cohesion dust trains with diameters of about 5 micron or less may be carried into suspension by aeolian surface shear stress, given expected geostrophic wind speeds of about 10 m/s. For geyser-like erupting dust plumes, it is shown that dust-settling time scales and expected wind velocities can produce streaks with length scales in good agreement with those of the streaks. Thus, both geyserlike eruptions or direct lifting by surface winds appear to be viable mechanisms for the origin of the streaks.

  20. The Origin of Transverse Aeolian Ridges on Mars

    NASA Astrophysics Data System (ADS)

    Geissler, P.

    2015-12-01

    Transverse aeolian ridges, or TARs, are found throughout the tropics of Mars and typically appear as rows of bright ripples that are several meters tall and spaced semi-regularly several tens of meters apart. The origin of these features remained mysterious for decades after their discovery in Viking and Mars Global Surveyor images. A new hypothesis (Geissler, 2014, 10.1002-2014JE004633) suggests that TARs might be deposits left behind by dusty turbidity currents in the Martian atmosphere. The hypothesis assumes that the micron-sized dust particles are transported in suspension in turbulent flows, driven both by the winds and by gravity. The dust is concentrated near the surface, much like turbidity currents on Earth. Because of the difference in density, however, the dust clouds behave as a fluid distinct from the clear sky above. In particular, waves can appear at the surface of the dense "fluid" when the flows encounter topographic obstacles along their paths. Such gravity waves travel at speeds that are determined by gravity and the thickness of the flow, much like waves in shallow water on Earth. When the wave propagation speed matches the speed of the flow, stationary waves are produced that persist in fixed locations. The bedforms deposited by such stationary waves are called "antidunes" (Gilbert, 1914, USGS Prof. Paper 86) because, unlike dunes, they can migrate upstream in a supercritical flow. Antidunes are commonly seen in shallow, high energy fluvial deposits on Earth. They are usually destroyed as quickly as they form, and are rarely preserved. The Martian TARs survive because the dust is sticky; TARs are deposited by currents that are much slower than the wind speeds needed to lift the dust again. Subaerial antidunes are much rarer on Earth and less well studied, and so the giant subaerial stationary antidunes of Mars, if that is what the TARs turn out to be, may teach us much about a geological process that is poorly known on our planet.

  1. A theoretical note on aerodynamic lifting in dust devils

    NASA Astrophysics Data System (ADS)

    Wang, Zhen-Ting

    2016-02-01

    The stress distribution of a known rotating flow near the ground in fluid mechanics indicates that the horizontal aerodynamic entrainment of particles within dust devils is attributed to friction force rather than pressure force. The expression of dust emission rate on Earth was theoretically discussed based on simulated flow field and our current understanding of the physics of aeolian dust. It seems that transition flow is vital to dust devils on Mars.

  2. Variation and Distribution of Sediments in a Mixed Glacifluvial-Aeolian System in West Greenland

    NASA Astrophysics Data System (ADS)

    Austin, M. J.; Bullard, J. E.

    2007-12-01

    There is a clear association between the distribution of wind-blown sediments and the former extent of ice sheets and glaciers. Glacial erosion processes produce significant quantities of fine sediments that are washed out from beneath glaciers by meltwater. Once deposited and desiccated, aeolian processes may transport them across the landscape resulting in the formation of sand dunes and loess, and adding dust to the atmosphere. This research reports the use of digital imaging and laser sizing to obtain the grain size distribution and textural attributes of sand and dust in Sandflugtdalen, a valley adjacent to the West Greenland ice sheet. An initial assessment of the rates of sand and dust transport, made using semi-isokinetic directional sediment samplers, indicate that the flux of aeolian sediment comprises clays, silts and sand-sized particles. Digital imaging of the surficial sediment deposits provides a rapid means of sampling the large, spatially and temporally variable, proglacial valley. Sediments were initially photographed during June 2007 and then resampled after a 9-week interval. The grain size distribution and surface texture were computed using a calibrated autocorrelation method. It is estimated that individual particles may be resolved down to a size of 0.045 mm. The regions of aeolian entrainment, transport and deposition are directly linked to the development and distribution of sediments on the proglacial floodplain, which varies considerably in terms of surface roughness. On the floodplain close to the ice sheet, aeolian flux is controlled by sediment supply and lag formation and the total surface roughness is determined by the combination of grain-scale roughness and topography. Further down valley, recycling of sediments by aeolian and fluvial activity is significant and wind speed becomes an important controlling factor. Within the dunefields, surface roughness is principally determined by topography and vegetation. Close to the ice sheet

  3. A conceptual framework for dryland aeolian sediment transport along the grassland-forest continuum: Effects of woody plant canopy cover and disturbance

    USGS Publications Warehouse

    Breshears, D.D.; Whicker, J.J.; Zou, C.B.; Field, J.P.; Allen, C.D.

    2009-01-01

    range of rates in grasslands and associated systems with no woody plants (e.g., agricultural fields), an intermediate range in shrublands, and a relatively small range in woodlands and forests. These trends are consistent with previous observations relating large rates of wind erosion to intermediate values for spatial density of roughness elements. The framework for aeolian sediment transport, which is also relevant to dust fluxes, wind erosion, and related aeolian processes, is applicable to a diverse suite of environmental challenges, including land degradation and desertification, dust storms, contaminant transport, and alterations of the hydrological cycle. ?? 2008 Elsevier B.V.

  4. The physics of wind-blown sand and dust.

    PubMed

    Kok, Jasper F; Parteli, Eric J R; Michaels, Timothy I; Karam, Diana Bou

    2012-10-01

    The transport of sand and dust by wind is a potent erosional force, creates sand dunes and ripples, and loads the atmosphere with suspended dust aerosols. This paper presents an extensive review of the physics of wind-blown sand and dust on Earth and Mars. Specifically, we review the physics of aeolian saltation, the formation and development of sand dunes and ripples, the physics of dust aerosol emission, the weather phenomena that trigger dust storms, and the lifting of dust by dust devils and other small-scale vortices. We also discuss the physics of wind-blown sand and dune formation on Venus and Titan.

  5. Accretion of Interplanetary Dust: A New Record from He-3 In Polar Ice Cores

    NASA Technical Reports Server (NTRS)

    Brook, Edward

    2002-01-01

    This grant funded measurements of extraterrestrial He-3 in particles extracted from polar ice samples. The overall objective was to develop measurements of He-3 as tracers of the flux of interplanetary dust particles (IDP's) to the earth. To our knowledge these are the first such measurements, apart from our earlier work. The project also funded an EPO activity - a climate and global change workshop for high school science teachers.

  6. Mars Environmental Chamber for Dynamic Dust Deposition and Statics Analysis

    NASA Technical Reports Server (NTRS)

    Moeller, L. E.; Tuller, M.; Islam, M. R.; Baker, L.; Kuhlman, K.

    2004-01-01

    Recent observations of the 2001 dust storms encircling Mars confirm predictions of environmental challenges for exploration. Martian dust has been found to completely mantle the Martian surface over thousands of square kilometers and the opacity of airborne dust has been shown to be capable of modifying atmospheric temperature, radiative transfer and albedo. Planetary dust cycling dynamics are suggested to be a key factor in the evolution of the Martian surface. Long-term robotic and manned exploration of Mars will be confronted by dust deposition in periods of atmospheric calm and violent wind storms. Aeolian dust deposition recorded during the Mars Pathfinder mission was estimated to fall at rates of 20-45 microns per Earth year. Although many tools of exploration will be challenged by coating, adhesion, abrasion and possible chemical reaction of deposited, wind blown and actively disturbed Martian dust, solar cells are thought to be of primary concern. Recent modeling work of power output by gallium arsenide/germanium solar cells was validated by the Pathfinder Lander data and showed power output decreases of 0.1 to 0.5% per Martian day. A major determinant for the optimal positioning angle of solar panels employed in future missions is the angle of repose of the settling dust particles that is dependent on a variety of physical and chemical properties of the particles, the panel surface, and the environmental conditions on the Mars surface. While the effects of many of these factors are well understood qualitatively, quantitative analyses, especially under physical and chemical conditions prevailing on the Mars surface are lacking.

  7. Aeolian sands and buried soils in the Mecklenburg Lake District, NE Germany: Holocene land-use history and pedo-geomorphic response

    NASA Astrophysics Data System (ADS)

    Küster, Mathias; Fülling, Alexander; Kaiser, Knut; Ulrich, Jens

    2014-04-01

    The present study is a pedo-geomorphic approach to reconstructing Holocene aeolian sand dynamics in the Mecklenburg Lake District (NE Germany). Stratigraphical, sedimentological and soil research supplemented by morphogenetic interpretations of the genesis of dunes and aeolian sands are discussed. A complex Late Holocene aeolian stratigraphy within a drift sand area was developed at the shore of Lake Müritz. The results were confirmed using palynological records, archaeological data and regional history. Accelerated aeolian activity was triggered by the intensification of settlement and land-use activities during the 13th and in the 15th to 16th century AD. After a period of stability beginning with population decline during the ‘Thirty Years War' and continuing through the 18th century, a final aeolian phase due to the establishment of glassworks was identified during the 19th century AD. We assume a direct link between Holocene aeolian dynamics and human activities. Prehistoric Holocene drift sands on terrestrial sites have not been documented in the Mecklenburg Lake District so far. This might be explained either by erosion and incorporation of older aeolian sediments during younger aeolian phases and/or a lower regional land-use intensity in older periods of the Holocene. The investigated drift sands are stratigraphically and sedimentologically characterised by a high degree of heterogeneity, reflecting the spatial and temporal variability of Holocene human impact.

  8. Biophysical drivers of erosion and aeolian transport in semiarid grasslands: Consequences of prescribed fire, livestock grazing and climate variability (Invited)

    NASA Astrophysics Data System (ADS)

    Field, J. P.; Breshears, D. D.; Whicker, J. J.

    2010-12-01

    Aeolian sediment transport operates over a range of spatial and temporal scales and can have important implications for atmospheric, hydrologic, and biogeochemical processes, especially in arid and semiarid ecosystems where ground cover is inherently sparse. A key consequence of sparser vegetation cover and drier soils is the potential for increased erosion and aeolian transport. Further, many arid and semiarid ecosystems are undergoing accelerated land degradation due to increased climate variability, as well as increased land-use activities such as prescribed fire and livestock grazing, both of which can have substantial effects on erosional losses through aeolian and fluvial processes. Despite the fundamental importance of both aeolian and fluvial processes within these systems, relatively few measurements of aeolian sediment transport have been made that span multiple wind events following land-use activities or wet/dry climate extremes. Here we report co-located estimates of aeolian and fluvial sediment transport in a semiarid grassland under different land-use practices (grazed, burned, and burned+grazed) for a three-year study period, which included a year with wet-dry extremes—providing an opportunistic analog to projected global-change-type climate. We also report estimates of aeolian sediment transport into and out of bare-, herbaceous-, and shrub-dominated patch types for both simulated and natural dust events, as well as in response to simulated disturbance. Our results indicate that disturbance can have a large effect on erosion and aeolian transport at the plot scale and vegetation-patch scale and that the type and intensity of disturbance plays an important role in determining the magnitude and the severity of the response. Notably, results indicate that wet/dry climate extremes can substantially increase the wind-to-water sediment transport ratio, whereas burning disproportionally increases fluvial sediment transport relative to aeolian sediment

  9. "Dust Devils": Gardening Agents on the Surface of Mars, and Hidden Hazards to Human Exploration?

    NASA Technical Reports Server (NTRS)

    Marshall, J.; Smith, P.; White, B.; Farrell, W.

    1999-01-01

    Dust devils are familiar sites in the and regions of the world: they can produce quite spectacular displays of dust lofting when the vortices scavenge very loose dust from a dry lake bed or from recently disturbed agricultural fields. If one were to arrive at the center of an arid region, take one photograph, or even a series of photographs over a period of several days, then return the images for laboratory analysis, it would be most likely concluded that the region was inactive from an aeolian perspective. No images of general dust movement were obtained, nor were any dust devils "caught on camera" owing to their ephemeral and unpredictable appearance, and the fact that there was deceptively little residue of their actions. If, however, a camera were to take a 360 degree continuous recording over a period of a year, and the film were then to be shown at high speed over a period a several minutes, the impression might be that of a region ravaged by air vorticity and dust movement. Extrapolate this over geological time, and it is possible to visualize dust devils as prime aeolian agents, rather than insignificant vagaries of nature, On Mars, the thin atmosphere permits the surface of the planet to be heated but it does not itself retain heat with the capacity of the earth's atmosphere. This gives rise to greater thermal instability near the surface of Mars as "warm" air pockets diapiritically inject themselves into higher atmospheric layers. Resulting boundary-layer vorticity on Mars might therefore be expected to produce dust devils in abundance, if only seasonally. The spectacular images of dust devils obtained by Pathfinder within its brief functional period on the planet testify to the probability of highly frequent surface vorticity in light of the above reasoning about observational probability. Notably, the Pathfinder devils appeared to be at least a kilometer in height. There are several consequences for the geology of Mars, and for human exploration, if

  10. The developmental trend and influencing factors of aeolian desertification in the Zoige Basin, eastern Qinghai-Tibet Plateau

    NASA Astrophysics Data System (ADS)

    Hu, Guangyin; Dong, Zhibao; Lu, Junfeng; Yan, Changzhen

    2015-12-01

    The Zoige Basin is located in the northeastern region of the Qinghai-Tibet Plateau and covers an area of 19,400 km2. At a mean altitude of 3500 m, the basin is highly sensitive to global environmental change and human disturbance due to its high elevation and fragile cold environment. The process of aeolian desertification in the basin can be clearly recognized in Landsat images that show the development of sand sheets and dunes over time. To monitor the spatial and temporal changes of aeolian desertification in the Zoige Basin, we analyzed Landsat images recorded in 1975, 1990, 2000, 2005, and 2010. Results showed that aeolian desertification increased rapidly from 1975 to 1990, was stable from 1990 to 2000, decreased slightly from 2000 to 2005, and decreased sharply from 2005 to 2010. Increasing temperature, overgrazing, rodent damage, and drainage of wetlands were considered the key driving factors of the expansion of aeolian desertification. A number of political measures were initiated in the 1990s to slow desertification, but the countermeasures of grazing prohibition, enclosures, and paving straw checkerboard barriers were not implemented until around 2005. These measures resulted in a dramatic recovery of aeolian desertified land between 2005 and 2010. Based on the cause analysis, anthropogenic factors were identified as the dominant driving force for both development and recovery of aeolian desertified land.

  11. Abstracts for the Planetary Geology Field Conference on Aeolian Processes

    NASA Technical Reports Server (NTRS)

    Greeley, R. (Editor); Black, D. (Editor)

    1978-01-01

    The Planetary Geology Field Conference on Aeolian Processes was organized at the request of the Planetary Geology Program office of the National Aeronautics and Space Administration to bring together geologists working on aeolian problems on earth and planetologists concerned with similar problems on the planets. Abstracts of papers presented at the conference are arranged herein by alphabetical order of the senior author. Papers fall into three broad categories: (1) Viking Orbiter and Viking Lander results on aeolian processes and/or landforms on Mars, (2) laboratory results on studies of aeolian processes, and (3) photogeology and field studies of aeolian processes on Earth.

  12. Quantification of Iron Oxides and Hydroxides in Desert Aeolian Particles

    NASA Astrophysics Data System (ADS)

    Lafon, S.; Rajot, J.; Alfaro, S.; Gaudichet, A.

    2002-12-01

    Long range transport of desert dust over oceans constitute a source of iron for the surface water. Assessing the iron cycle and its biogeochemical implications in oceanic areas requires determination and quantification of the iron status in aeolian particles. Indeed, in such aerosols, the iron is either trapped in the silicate structure or present under the form of oxides and hydroxides (free iron). We propose a method to apportion iron between free and entrapped forms in mineral aerosols. It consists in the adaptation of a well known method used for soil characterization to the treatment of aerosol samples, which represent less than 1 mg of material collected by air filtration on polycarbonate filters. The iron oxides and hydroxides are extracted selectively using the combined action of reductive and complexant agents in a buffered solution. The iron content is measured before and after this chemical extraction using X ray fluorescence spectrometry. We attempt to give some values for three main desert source areas using aerosol samples collected near Niamey (Niger) either during Harmattan events or during local erosion events, and samples collected downwind of the Gobi desert in China. Results emphasize firstly that iron trapped in the structure of silicate minerals represents an important part of total iron content. This suggests that, regarding dissolution processes in sea water, total elemental iron content of aeolian dust can not be used directly to calculate the flux of iron available. Secondly, our results show that the free iron content vary according to the origin of dusts. Niger samples have contents in free iron of 4.4 % (SD = 0.8) for local erosion and 2.8 % (SD = 1.0) for Harmattan. Chinese samples contain 3.7 % (SD = 0.5) of free iron. These differences could be linked to the parent soil mineralogical composition that varies with geographical location, but for some of our samples it also could be linked to a size fractionation process occurring first

  13. Roughness configuration matters for aeolian sediment flux

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The parameterisation of surface roughness effects on aeolian sediment transport is a key source of uncertainty in wind erosion models. Roughness effects are typically represented by bulk drag-partitioning schemes that scale the threshold friction velocity (u*t) for soil entrainment by the ratio of s...

  14. Fluid-induced organic synthesis in the solar nebula recorded in extraterrestrial dust from meteorites.

    PubMed

    Vollmer, Christian; Kepaptsoglou, Demie; Leitner, Jan; Busemann, Henner; Spring, Nicole H; Ramasse, Quentin M; Hoppe, Peter; Nittler, Larry R

    2014-10-28

    Isotopically anomalous carbonaceous grains in extraterrestrial samples represent the most pristine organics that were delivered to the early Earth. Here we report on gentle aberration-corrected scanning transmission electron microscopy investigations of eight (15)N-rich or D-rich organic grains within two carbonaceous Renazzo-type (CR) chondrites and two interplanetary dust particles (IDPs) originating from comets. Organic matter in the IDP samples is less aromatic than that in the CR chondrites, and its functional group chemistry is mainly characterized by C-O bonding and aliphatic C. Organic grains in CR chondrites are associated with carbonates and elemental Ca, which originate either from aqueous fluids or possibly an indigenous organic source. One distinct grain from the CR chondrite NWA 852 exhibits a rim structure only visible in chemical maps. The outer part is nanoglobular in shape, highly aromatic, and enriched in anomalous nitrogen. Functional group chemistry of the inner part is similar to spectra from IDP organic grains and less aromatic with nitrogen below the detection limit. The boundary between these two areas is very sharp. The direct association of both IDP-like organic matter with dominant C-O bonding environments and nanoglobular organics with dominant aromatic and C-N functionality within one unique grain provides for the first time to our knowledge strong evidence for organic synthesis in the early solar system activated by an anomalous nitrogen-containing parent body fluid.

  15. Fluid-induced organic synthesis in the solar nebula recorded in extraterrestrial dust from meteorites

    PubMed Central

    Vollmer, Christian; Kepaptsoglou, Demie; Leitner, Jan; Busemann, Henner; Spring, Nicole H.; Ramasse, Quentin M.; Hoppe, Peter; Nittler, Larry R.

    2014-01-01

    Isotopically anomalous carbonaceous grains in extraterrestrial samples represent the most pristine organics that were delivered to the early Earth. Here we report on gentle aberration-corrected scanning transmission electron microscopy investigations of eight 15N-rich or D-rich organic grains within two carbonaceous Renazzo-type (CR) chondrites and two interplanetary dust particles (IDPs) originating from comets. Organic matter in the IDP samples is less aromatic than that in the CR chondrites, and its functional group chemistry is mainly characterized by C–O bonding and aliphatic C. Organic grains in CR chondrites are associated with carbonates and elemental Ca, which originate either from aqueous fluids or possibly an indigenous organic source. One distinct grain from the CR chondrite NWA 852 exhibits a rim structure only visible in chemical maps. The outer part is nanoglobular in shape, highly aromatic, and enriched in anomalous nitrogen. Functional group chemistry of the inner part is similar to spectra from IDP organic grains and less aromatic with nitrogen below the detection limit. The boundary between these two areas is very sharp. The direct association of both IDP-like organic matter with dominant C–O bonding environments and nanoglobular organics with dominant aromatic and C–N functionality within one unique grain provides for the first time to our knowledge strong evidence for organic synthesis in the early solar system activated by an anomalous nitrogen-containing parent body fluid. PMID:25288736

  16. Fluid-induced organic synthesis in the solar nebula recorded in extraterrestrial dust from meteorites.

    PubMed

    Vollmer, Christian; Kepaptsoglou, Demie; Leitner, Jan; Busemann, Henner; Spring, Nicole H; Ramasse, Quentin M; Hoppe, Peter; Nittler, Larry R

    2014-10-28

    Isotopically anomalous carbonaceous grains in extraterrestrial samples represent the most pristine organics that were delivered to the early Earth. Here we report on gentle aberration-corrected scanning transmission electron microscopy investigations of eight (15)N-rich or D-rich organic grains within two carbonaceous Renazzo-type (CR) chondrites and two interplanetary dust particles (IDPs) originating from comets. Organic matter in the IDP samples is less aromatic than that in the CR chondrites, and its functional group chemistry is mainly characterized by C-O bonding and aliphatic C. Organic grains in CR chondrites are associated with carbonates and elemental Ca, which originate either from aqueous fluids or possibly an indigenous organic source. One distinct grain from the CR chondrite NWA 852 exhibits a rim structure only visible in chemical maps. The outer part is nanoglobular in shape, highly aromatic, and enriched in anomalous nitrogen. Functional group chemistry of the inner part is similar to spectra from IDP organic grains and less aromatic with nitrogen below the detection limit. The boundary between these two areas is very sharp. The direct association of both IDP-like organic matter with dominant C-O bonding environments and nanoglobular organics with dominant aromatic and C-N functionality within one unique grain provides for the first time to our knowledge strong evidence for organic synthesis in the early solar system activated by an anomalous nitrogen-containing parent body fluid. PMID:25288736

  17. Aeolian activity in northern Amazonia: optical dating of Late Pleistocene and Holocene palaeodunes

    NASA Astrophysics Data System (ADS)

    Teeuw, Richard M.; Rhodes, Edward J.

    2004-01-01

    Palaeodunes were examined on the eastern margin of the Rio Branco-Rupununi savanna, northeast Amazonia. Optical dating suggests that the onset of aeolian activity was between 17 000 and 15 000 yr ago, just after the Last Glacial Maximum. Both the palaeodune axes and modern dominant wind directions have northeast to east-northeast directions, implying no significant shift in atmospheric circulation patterns over northeast Amazonia during the Late Pleistocene to Holocene. Major regional climate change events, such as the Younger Dryas, do not appear to have had any effect on the rates of aeolian deposition at the study site. Aeolian activity appears to have continued to the present day, showing a remarkably constant deposition rate of around 0.13 m kyr-1 initially, increasing smoothly to the present. Until more palaeodunes in northern Amazonia are dated, it is impossible to determine if this record of gradual aeolian deposition is a reliable regional palaeoclimate indicator, rather than being the result of local bioclimatic and geomorphological effects. Copyright

  18. The most unusual dust event cases from Iceland

    NASA Astrophysics Data System (ADS)

    Dagsson Waldhauserova, Pavla; Arnalds, Olafur; Olafsson, Haraldur; Meinander, Outi; Gritsevich, Maria

    2016-04-01

    Iceland has the largest area of volcaniclastic sandy desert on Earth where dust is originating from volcanic, but also glaciogenic sediments. Total Icelandic desert areas cover over 44,000 km2 suggesting Iceland being the largest Arctic as well as European desert. Satelite MODIS pictures have revealed dust plumes traveling over 1000 km at times. The mean frequency of days with dust suspension was to 135 dust days annually in 1949-2011. The annual dust deposition was calculated as 31 - 40.1 million tons yr-1 affecting the area of > 500,000 km2, which places Iceland among the most active dust sources on Earth. Volcanic dust is distributed over local glaciers (about 4.5 million t annually) and surrounding oceans (6 - 14 million t annually). Mean dust emissions were calculated for minor, medium and major dust events as 0.1, 0.3 and 1 million tons per event, respectively. Three unusual dust events were observed and measured: The first, an extreme wind erosion event of the fresh Eyjafjallajokull 2010 volcanic ash, the second, a Snow-Dust Storm in 2013, and the third, a suspended dust during moist and low wind conditions. Frequent volcanic eruptions in Iceland (new eruption each 3-4 years on average) represent important inputs to dust variability. Freshly deposited ash prolongs impacts of volcanic eruptions as we observed after the 2010 Eyjafjallajokull eruption. In September 2010, an extreme storm was recorded with the maximum wind speed of 38.7 ms-1. The maximum saltation was 6825 pulses per minute while the aeolian transport over one m wide transect and 150 cm height reached 11,800 kg m-1. The largest previously measured amount in Iceland in one storm was about 4,200 kg m-1. This storm is among the most extreme wind erosion events recorded on Earth. Dust events in South Iceland often take place in winter or at sub-zero temperatures. The Snow-Dust Storm occurred in March 6-7th 2013 when snow was nearly black with several mm thick dark layer of dust deposited on snow

  19. Dust flux in peripheral East Antarctica: preliminary results from GV7 ice core and extension of the TALDICE dust record to the sub-micron range

    NASA Astrophysics Data System (ADS)

    Delmonte, Barbara; Giovanni, Baccolo; Fausto, Marasci; Iizuka, Yoshinori; Valter, Maggi

    2015-04-01

    Improved understanding of climate variability over the last two millennia - that is a critical time period for investigating natural and anthropogenic climate change - is one of the key priorities of the International Partnership in Ice Core Sciences (IPICS). The Italian contribution to this concerted international effort is represented by the project IPICS-2kyr-Italy supported by PNRA. In this context, a novel intermediate core (about 250 m deep) was drilled during the 2013/14 field season at the peripheral site of GV7 in East Antarctica (70°41'S, 158°52'E; elevation 1950 m), where snow accumulation is very high (about 3 times Talos Dome, 10 times EPICA Dome C). After the ice core processing campaign at EuroCold (UNIMIB) carried out in synergy between Italy and Korea teams, measurements of dust concentration and size distribution are now in progress. A novel Coulter Counter apparatus has been set up in order to extend dust size spectra down to 600 nm. Samples are analyzed immediately after melting and also 24h later under identical conditions, for a quantitative assessment of the contribution of water-soluble microparticles (salts). Seasonal variability and trends of insoluble dust, metastable salts and size distribution of these compounds is under study. The possibility to extended the size range of dust measurements has allowed refining estimates of dust flux at Talos Dome and an adjustment of published data.

  20. Aeolian Grain Evolution on Mars: Implications for Regolith Origins

    NASA Astrophysics Data System (ADS)

    Sullivan, R. J.; Cabrol, N. A.; Golombek, M.; Herkenhoff, K. E.; Landis, G.; Mer Athena Science Team

    2010-12-01

    Early wind tunnel experiments and the Viking Lander experience led to concepts of grain evolution and regolith development on Mars. Wind tunnel experiments showed that 100-150 μm grains are easiest to entrain on Mars, but at 10 times higher wind speeds than on Earth. Even if trajectory speeds of martian saltating grains achieve smaller fractions of entraining wind speeds than on Earth, kinetic energies of these grains would be much higher, with greater potential for damage to the grains during return collisions with the particle bed. On this basis Sagan et al. [1977] JGR 82, 28, 4430 proposed that aeolian grain evolution on Mars followed a “kamikaze” pattern in which an initially coarse grain, entrained only relatively rarely by the strongest winds, would be abraded by high kinetic energy impacts and migrate through successively smaller size-frequencies at an ever-increasing rate (as entrainment became easier and thus more likely) until the grain was essentially turned to dust. On this basis it was proposed that sand-sized grains might be relatively short-lived and perhaps rare on Mars. MER observations motivate adjustments to these concepts, with implications for origins of martian regolith reworked by wind. Along both MER traverses, on opposite sides of the planet, regolith is volumetrically dominated by very fine sand mixed with unresolved finer grains. Sorting probably is poor, based on weakly cohesive remolding by rover wheel cleats. The size-frequency of this material, even if not precisely known, is consistent with grains that have evolved by attrition to sizes smaller than the most easily-moved 100-150 μm interval, to where entrainment becomes more difficult due to the increasing relative importance of inter-particle surface forces. At these smaller sizes also, kinetic energies have been reduced proportionally by the cube of the particle radius, so grain-to-grain attrition is less effective for further evolution to even smaller grain sizes

  1. The composition of Martian aeolian sands: Thermal emissivity from Viking IRTM observations

    NASA Technical Reports Server (NTRS)

    Edgett, Kenneth S.; Christensen, Philip R.

    1992-01-01

    Aeolian sands provide excellent surfaces for the remote determination of the mineralogic composition of Martian materials, because such deposits consist of relatively well-sorted, uniform particle sizes and might consist of chemically unaltered, primary mineral grains derived from bedrock. Dark features on the floors of Martian craters are controlled by aeolian processes and many consist largely of unconsolidated, windblown sand. Measurement of the thermal emissivity of geologic materials provides a way to identify mid-infrared absorption bands, the strength and positions of which vary with mineral structure and composition. The Viking Infrared Thermal Mapper (IRTM) had four surface-sensing mid-IR bands, three of which, the 7, 9, and 11 micron channels, correspond to absorption features characteristic of carbonates, sialic, and mafic minerals, respectively. In this study, the highest quality IRTM data were constrained so as to avoid the effects of atmospheric dust, clouds, surface frosts, and particle size variations (the latter using data obtained between 7 and 9 H, and they were selected for dark intracrater features such that only data taken directly from the dark feature were used, so as to avoid thermal contributions from adjacent but unrelated materials. Three-point emissivity spectra of Martian dart intracrater features were compared with laboratory emission spectra of minerals and terrestrial aeolian sands convolved using the IRTM response function to the four IRTM spectral channels.

  2. Dune-like dynamic of Martian Aeolian large ripples

    NASA Astrophysics Data System (ADS)

    Silvestro, S.; Vaz, D. A.; Yizhaq, H.; Esposito, F.

    2016-08-01

    Martian dunes are sculpted by meter-scale bed forms, which have been interpreted as wind ripples based on orbital data. Because aeolian ripples tend to orient and migrate transversely to the last sand-moving wind, they have been widely used as wind vanes on Earth and Mars. In this report we show that Martian large ripples are dynamically different from Earth's ripples. By remotely monitoring their evolution within the Mars Science Laboratory landing site, we show that these bed forms evolve longitudinally with minimal lateral migration in a time-span of ~ six terrestrial years. Our observations suggest that the large Martian ripples can record more than one wind direction and that in certain cases they are more similar to linear dunes from a dynamic point of view. Consequently, the assumption of the transverse nature of the large Martian ripples must be used with caution when using these features to derive wind directions.

  3. Periodic Trajectories in Aeolian Sand Transport

    NASA Astrophysics Data System (ADS)

    Valance, A.; Jenkins, J. T.

    2014-12-01

    Saltation is the primary mode of aeolian sand transport and refers to the hoping motion of grains over the bed [1]. We develop a simple model for steady, uniform transport in aeolian saltation over a horizontal bed that is based on the computation of periodic particle trajectories in a turbulent shearing flow [2]. The wind and the particles interact through drag, and the particles collide with the bed. We consider collisions with a rigid, bumpy bed, from which the particles rebound, and an erodible particle bed, for which a collision involves both rebound and particle ejection. The difference in the nature of the collisions results in qualitative differences in the nature of the solutions for the periodic trajectories and, in particular, to differences in the dependence of the particle flow rate on the strength of the turbulent shearing. We also discuss the pertinence of this model to describe bedload transport in water. References:[1] R. A. Bagnold, « The physics of blown sand and desert dunes » , Methuen, New York (1941).[2] J.T Jenkins and A. Valance. Periodic trajectories in Aeolian saltation transport. Physics of Fluids, 2014, 26, pp. 073301

  4. Aeolian processes in Proctor Crater on Mars: Sedimentary history as analyzed from multiple data sets

    USGS Publications Warehouse

    Fenton, L.K.; Bandfield, J.L.; Ward, A.W.

    2003-01-01

    Proctor Crater is a 150 km diameter crater in Noachis Terra, within the southern highlands of Mars. The analysis leading to the sedimentary history incorporates several data sets including imagery, elevation, composition, and thermal inertia, mostly from the Mars Global Surveyor mission. The resulting stratigraphy reveals that the sedimentary history of Proctor Crater has involved a complex interaction of accumulating and eroding sedimentation. Aeolian features spanning much of the history of the crater interior dominate its surface, including large erosional pits, stratified beds of aeolian sediment, sand dunes, erosional and depositional streaks, dust devil tracks, and small bright bed forms that are probably granule ripples. Long ago, up to 450 m of layered sediment filled the crater basin, now exposed in eroded pits on the crater floor. These sediments are probably part of an ancient deposit of aeolian volcaniclastic material. Since then, some quantity of this material has been eroded from the top layers of the strata. Small, bright dune forms lie stratigraphically beneath the large dark dune field. Relative to the large dark dunes, the bright bed forms are immobile, although in places, their orientations are clearly influenced by the presence of the larger dunes. Their prevalence in the crater and their lack of compositional and thermal distinctiveness relative to the crater floor suggests that these features were produced locally from the eroding basin fill. Dust devil tracks form during the spring and summer, following a west-southwesterly wind. Early in the spring the dust devils are largely restricted to dark patches of sand. As the summer approaches, dust devil tracks become more plentiful and spread to the rest of the crater floor, indicating that the entire region acquires an annual deposit of dust that is revealed by seasonal dust devils. The dark dunes contain few dust devil tracks, suggesting that accumulated dust is swept away directly by saltation

  5. Aeolian processes in Proctor Crater on Mars: Sedimentary history as analyzed from multiple data sets

    NASA Astrophysics Data System (ADS)

    Fenton, Lori K.; Bandfield, Joshua L.; Ward, A. Wesley

    2003-12-01

    Proctor Crater is a 150 km diameter crater in Noachis Terra, within the southern highlands of Mars. The analysis leading to the sedimentary history incorporates several data sets including imagery, elevation, composition, and thermal inertia, mostly from the Mars Global Surveyor mission. The resulting stratigraphy reveals that the sedimentary history of Proctor Crater has involved a complex interaction of accumulating and eroding sedimentation. Aeolian features spanning much of the history of the crater interior dominate its surface, including large erosional pits, stratified beds of aeolian sediment, sand dunes, erosional and depositional streaks, dust devil tracks, and small bright bed forms that are probably granule ripples. Long ago, up to 450 m of layered sediment filled the crater basin, now exposed in eroded pits on the crater floor. These sediments are probably part of an ancient deposit of aeolian volcaniclastic material. Since then, some quantity of this material has been eroded from the top layers of the strata. Small, bright dune forms lie stratigraphically beneath the large dark dune field. Relative to the large dark dunes, the bright bed forms are immobile, although in places, their orientations are clearly influenced by the presence of the larger dunes. Their prevalence in the crater and their lack of compositional and thermal distinctiveness relative to the crater floor suggests that these features were produced locally from the eroding basin fill. Dust devil tracks form during the spring and summer, following a west-southwesterly wind. Early in the spring the dust devils are largely restricted to dark patches of sand. As the summer approaches, dust devil tracks become more plentiful and spread to the rest of the crater floor, indicating that the entire region acquires an annual deposit of dust that is revealed by seasonal dust devils. The dark dunes contain few dust devil tracks, suggesting that accumulated dust is swept away directly by saltation

  6. Introducing a New International Society of Aeolian Research

    NASA Astrophysics Data System (ADS)

    Zobeck, T. M.; Lee, J.; Lancaster, N.; Bullard, J. E.

    2008-12-01

    Aeolian research is a long-standing and rapidly growing area of geological study where scientists of many disciplines meet to investigate the effects of wind on the surface of the Earth and other planetary bodies such as Mars and Titan. Fields of study in aeolian research cover a broad spectrum ranging from developing a basic scientific understanding of the fundamental physical processes of grain motion to the effects of soil erosion on landscape health and environmental sustainability. Aeolian research also includes studies of the effects of aeolian particles on global climate, air quality, and human health, coastal sand transport processes, land degradation, dune migration, the formation of sand seas, and much more. A growing number of international conferences have been organized to focus specifically on aeolian phenomena and a vast number of scholarly publications have been produced to support the science. One popular bibliography includes over 30,000 citations and hundreds of peer-reviewed papers are published each year. Until very recently, no scientific society specifically dealing with aeolian research has been available. The new International Society of Aeolian Research (ISAR) that has been organized to bring together aeolian scientists from around the world. The new society was created to promote contacts among researchers in aeolian processes and related subjects for discussion and comparison of research, to initiate conferences (such as the International Conference on Aeolian Research), to organize excursions, and support the publication of a peer-reviewed scientific journal. The International Society of Aeolian Research sponsors the new Elsevier journal Aeolian Research in support of these activities. This paper will provide further details about the new society and the journal. Please see www.aeolianresearch.org for details.

  7. 130 kyr of Dust Fluxes in the Equatorial Pacific: Implications for ITCZ movement and intensity

    NASA Astrophysics Data System (ADS)

    Jacobel, A. W.; Costa, K.; McManus, J. F.; Winckler, G.; Anderson, R. F.

    2015-12-01

    The position of the Intertropical Convergence Zone (ITCZ) has been hypothesized to play a role in linking the climate of the poles to the tropics and in predicating important changes in ocean overturning, particularly on deglacial timescales. One method of tracking the paleo-position of the ITCZ is through the quantification of 230Thxs,0-normalized 232Th concentrations in marine sediments which act as proxy for aeolian dust flux. Because the ITCZ is an efficient scavenger of atmospheric particulates, changes in the latitude of maximum dust flux can yield insight into variations in ITCZ position. This technique has been successfully utilized to reconstruct the movement of the ITCZ during the last deglaciation in the eastern equatorial Pacific (McGee et al., 2007). In this study we apply a similar approach to produce a high-resolution reconstruction of ITCZ movement in the central equatorial Pacific over the last 130 kyr, including the last glacial inception, Marine Isotope Stage 4, the Last Glacial Maximum and Termination I (TI). We present records of 232Th/230Thxs,0 as a proxy for continentally sourced dust at sub-millennial resolution along a latitudinal transect of three sites beneath the shifting ITCZ. We pair our new data with existing dust flux data from Antarctica, Greenland and the North Pacific to differentiate between changes in the ITCZ and variability in atmospheric dust abundance. Our data reconstruct a spatially different pattern of ITCZ movement during the last two deglaciations, which allows us to locate our records in the context of recent studies challenging our mechanistic understanding of deglacial terminations. Additionally, our data show evidence of precessional forcing in reconstructed dust fluxes, and we evaluate changes in ITCZ precipitation intensity (scavenging efficiency) and enhanced aeolian transport in tropical dust source regions as the driver of this variability.D. McGee, F. Marcantonio, and J. Lynch-Stieglitz, "Deglacial Changes in

  8. Aeolian transport pathways along the transition from Tibetan highlands towards northwestern Chinese deserts

    NASA Astrophysics Data System (ADS)

    Nottebaum, Veit; Lehmkuhl, Frank; Stauch, Georg

    2014-05-01

    The identification and semi-quantification of aeolian transport pathways enhances the understanding of aeolian sediment archive formation and thus supports reliability and explanatory power concerning palaeoenvironmental reconstructions. Grain size analysis of 279 surface sediment samples from the transition of Tibetan highlands (Qilian Shan) towards northwestern Chinese deserts allows the differentiation of contributing pathways among three types of aeolian sediments: silty loess, sandy loess, and aeolian sands. The study area exhibits a high diversity of geomorphological surfaces due to varieties in relief, elevation and climatic conditions. Therefore, it provides the opportunity to investigate the characteristics of sediments in different geomorphological settings. Using the peaks of grain size frequency's standard deviation of primary loess allows identification of the most sensitive fractions to varying accumulation conditions. mU/fS-ratio (7 - 13 μm / 58 - 84 μm) of primary silty loess relates the far-travelled dust proportion to the locally transported fine sand component. In vicinity to fluvial channels in the foreland mU/fS-values are significantly decreased, whereas mU/fS-values increase with altitude (r2 = 0.74). This indicates higher contribution of long distance transport compared to lower regions. A prominent increase of mU/fS-values above 3000 m asl likely indicates an increasing contribution of fine and medium silt particles transported by Westerlies in higher altitudes. In contrast, lower areas seem to be more strongly influenced by low altitude monsoon currents (NW-Winter- / SE-summer monsoon). The difference in grain size properties is additionally enhanced by the contrasting geomorphologic settings along the mountain declivity: Plain foreland alluvial fans support fine sand supply and availability whereas steep high mountain topography provides only limited potential for fine sand deflation. Similarly, the relatively low relief in intramontane

  9. Astronomic timescale for the Pliocene Atlantic δ18O and dust flux records of Ocean Drilling Program Site 659

    NASA Astrophysics Data System (ADS)

    Tiedemann, Ralf; Sarnthein, Michael; Shackleton, Nicholas J.

    1994-08-01

    High-resolution benthic oxygen isotope and dust flux records from Ocean Drilling Program site 659 have been analyzed to extend the astronomically calibrated isotope timescale for the Atlantic from 2.85 Ma back to 5 Ma. Spectral analysis of the δ18O record indicates that the 41-kyr period of Earth's orbital obliquity dominates the Pliocene record. This is shown to be true regardless of fundamental changes in the Earth's climate during the Pliocene. However, the cycles of Sahelian aridity fluctuations indicate a shift in spectral character near 3 Ma. From the early Pliocene to 3 Ma, the periodicities were dominantly precessional (19 and 23 kyr) and remained strong until 1.5 Ma. Subsequent to 3 Ma, the variance at the obliquity period (41 kyr) increased. The timescale tuned to precession suggests that the Pliocene was longer than previously estimated by more than 0.5 m.y. The tuned ages for the magnetic boundaries Gauss/Gilbert and Top Cochiti are about 6-8% older than the ages of the conventional timescale. A major phase of Pliocene northern hemisphere ice growth occurred between 3.15 Ma and 2.5 Ma. This was marked by a gradual increase in glacial Atlantic δ18O values of 1‰ and an increase in amplitude variations by up to 1.5‰, much larger than in the Pacific deepwater record (site 846). The first maxima occured in cold stages G6-96 between 2.7 Ma and 2.45 Ma. Prior to 3 Ma, the isotope record is characterized by predominantly low amplitude fluctuations (< 0.7‰.). When obliquity forcing was at its minimum between 4.15 and 3.6 Ma and during the Kaena interval, δ18O amplitude fluctuations were minimal. From 4.9 to 4.3 Ma, the δ18O values decreased by about 0.5‰, reaching a long-term minimum at 4.15 Ma, suggesting higher deepwater temperatures or a deglaciation. Deepwater cooling and/or an increase in ice volume is indicated by a series of short-term δ18O fluctuations between 3.8 and 3.6 Ma.

  10. The ecology of dust: local- to global-scale perspectives

    SciTech Connect

    Whicker, Jeffrey J; Field, Jason P; Belnap, Jayne; Breshears, David D; Neff, Jason; Okin, Gregory S; Painter, Thomas H; Ravi, Sujith; Reheis, Marith C; Reynolds, Richard L

    2009-01-01

    Emission and redistribution of dust due to wind erosion in drylands drives major biogeochemical dynamics and provides important aeolian environmental connectivity at scales from individual plants up to the global scale. Yet, perhaps because most relevant research on aeolian processes has been presented in a geosciences rather than ecological context, most ecological studies do not explicitly consider dust-driven processes. To bridge this disciplinary gap, we provide a general overview of the ecological importance of dust, examine complex interactions between wind erosion and ecosystem dynamics from the plant-interspace scale to regional and global scales, and highlight specific examples of how disturbance affects these interactions and their consequences. Changes in climate and intensification of land use will both likely lead to increased dust production. To address these challenges, environmental scientists, land managers and policy makers need to more explicitly consider dust in resource management decisions.

  11. Multi-decadal periods of enhanced aeolian activity on the north-eastern Tibet Plateau during the last 2ka

    NASA Astrophysics Data System (ADS)

    Stauch, Georg

    2016-10-01

    The north-eastern Tibetan Plateau is regarded as key area for the understanding of the Holocene paleoclimate in central Asia. During the last decade a special emphasis has been placed on multi-decadal to millennial scale climate fluctuations, especially in the context of the recent climate change. However, most reconstructions are based on lake sediments, tree rings and speleothems whereas only little information from terrestrial archives is included. This study presents multi-decadal scale climate fluctuations based on optical stimulated luminescence (OSL) ages from aeolian sediments from three catchment areas. Six phases of enhanced aeolian accumulation during the last 2000 years, each lasting around 80-200 years were identified. The first three phases (1630-1725 CE, 1450-1530 CE and 1250-1350 CE) occurred during the Little Ice Age; the other three (750-950 CE, 390-540 CE, 50-225 CE) during the so-called dark ages cooling. Aeolian processes were strongly reduced during the medieval climate anomaly. A comparison with other proxy records indicates that the formation of aeolian archives on the north-eastern Tibetan Plateau during the late Holocene is facilitated by cool and dry climate conditions during times of weaker Asian Summer Monsoon and probably enhanced westerlies. The results show that short term climate fluctuations can be reconstructed from non-continuous and heterogeneous terrestrial archives in a semi-arid environment, provided a sufficient number of OSL ages from aeolian sediments is available.

  12. Seismicity pattern changes before the M = 4.8 Aeolian Archipelago (Italy) earthquake of August 16, 2010.

    PubMed

    Gambino, Salvatore; Laudani, Antonino; Mangiagli, Salvatore

    2014-01-01

    We investigated the seismicity patterns associated with an M = 4.8 earthquake recorded in the Aeolian Archipelago on 16, August, 2010, by means of the region-time-length (RTL) algorithm. This earthquake triggered landslides at Lipari; a rock fall on the flanks of the Vulcano, Lipari, and Salina islands, and some damages to the village of Lipari. The RTL algorithm is widely used for investigating precursory seismicity changes before large and moderate earthquakes. We examined both the spatial and temporal characteristics of seismicity changes in the Aeolian Archipelago region before the M = 4.8 earthquake. The results obtained reveal 6-7 months of seismic quiescence which started about 15 months before the earthquake. The spatial distribution shows an extensive area characterized by seismic quiescence that suggests a relationship between quiescence and the Aeolian Archipelago regional tectonics. PMID:24511288

  13. Seismicity Pattern Changes before the M = 4.8 Aeolian Archipelago (Italy) Earthquake of August 16, 2010

    PubMed Central

    2014-01-01

    We investigated the seismicity patterns associated with an M = 4.8 earthquake recorded in the Aeolian Archipelago on 16, August, 2010, by means of the region-time-length (RTL) algorithm. This earthquake triggered landslides at Lipari; a rock fall on the flanks of the Vulcano, Lipari, and Salina islands, and some damages to the village of Lipari. The RTL algorithm is widely used for investigating precursory seismicity changes before large and moderate earthquakes. We examined both the spatial and temporal characteristics of seismicity changes in the Aeolian Archipelago region before the M = 4.8 earthquake. The results obtained reveal 6-7 months of seismic quiescence which started about 15 months before the earthquake. The spatial distribution shows an extensive area characterized by seismic quiescence that suggests a relationship between quiescence and the Aeolian Archipelago regional tectonics. PMID:24511288

  14. Sources and transport of dust to East Antarctica: new insights from high-resolution terrestrial and marine aerosol records from the Talos Dome ice core

    NASA Astrophysics Data System (ADS)

    Schüpbach, S.; Federer, U.; Albani, S.; Barbante, C.; Stocker, T. F.; Fischer, H.

    2013-06-01

    In this study we report on new non-sea salt calcium (nssCa2+, mineral dust proxy) and sea salt sodium (ssNa+, sea ice proxy) records along the East Antarctic Talos Dome deep ice core in centennial resolution reaching back 150 thousand years before present. During glacial conditions nssCa2+ fluxes in Talos Dome are strongly related to temperature as has been observed before in other deep Antarctic ice core records, and has been associated with synchronous changes in the main source region (southern South America) during climate variations in the last glacial. However, during warmer climate conditions Talos Dome mineral dust input is clearly elevated compared to other records mainly due to the contribution of additional local dust sources in the Ross Sea area. Based on a simple transport model we compare nssCa2+ fluxes of different East Antarctic ice cores. From this multi-site comparison we conclude that changes in transport efficiency or atmospheric lifetime of dust particles do have a minor effect compared to source strength changes on the large scale concentration changes observed in Antarctic ice cores during climate variations of the past 150 thousand years. Our transport model applied on ice core data only so far is further validated by climate model data. The availability of multiple East Antarctic nssCa2+ records allows for a revision of a former estimate on the atmospheric CO2 sensitivity to reduced dust induced iron fertilisation in the Southern Ocean (SO) during the transition from the Last Glacial Maximum to the Holocene (T1). While the former estimate based on the EDC record only suggested 20 ppm, we find reduced dust induced iron fertilisation in the SO to be responsible for up to 40 ppm of the total atmospheric CO2 increase during T1. During the last interglacial, ssNa+ levels of EDC and EDML are only half of the Holocene levels, in line with higher temperatures during that period, indicating much reduced sea ice extent in the Atlantic as well as the

  15. Current kinematics of the Aeolian Islands

    NASA Astrophysics Data System (ADS)

    Anzidei, Marco; Bonforte, Alessandro; Bruno, Valentina; Esposito, Alessandra; Mattia, Mario; Pietrantonio, Grazia; Pisani, Anna Rita; Puglisi, Giuseppe; Sepe, Vincenzo

    2014-05-01

    The active volcanic arc of the Aeolian islands is located between the Southern Tyrrhenian Sea back arc basin (Marsili basin) and the Calabrian Arc, an orogenic belt affected by a Late Quaternary extensional tectonics and uplift. This region is undergoing to shallow and deep seismicity up to 550 km and active volcanism due to the subduction extensional strain and heat flow related to the slab detachment beneath the Calabrian Arc. In this geodynamic framework, the current crustal deformations detected at the ground surface by continuous and episodic GPS data collected in the archipelago and its surroundings in the time span 1996-2012, reflect both the behavior of the single volcanic islands and the regional tectonics of this complex region. Particularly, we focus on the current vertical component of land motion that indicate a diffuse subsidence that is in contrast with uplifting Quaternary geological data. GPS data show that subsiding is increasing toward north between Vulcano and Lipari Islands, but with episodic uplift at Panarea. Particularly, Lipari is rapidly subsiding at mean velocities exceeding 10 mm/yr, which the highest value among the Aeolian island. Instrumental data are in agreement with independent observations that for Lipari Marina Corta indicate a continuous subsidence with rates at at about 8 mm/yr since the last 2200 years B.P., while in Basiluzzo at about 2 mm/yr. Here we show and discuss the current geodetic strain and velocity field for the time span 1996-2012 for the Aeolian archipelago, as well as the GPS data archive. Finally, for Lipari island, the continuous land subsidence will cause a wide submersion of coastal installations by the year 2100 and represent a significant hazard within an urbanized coastal area.

  16. Introducing a New International Society of Aeolian Research

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aeolian research is long-standing and rapidly growing area of study where scientists of many disciplines meet to investigate the effects of wind on the surface of the Earth and other planetary bodies, such as Mars and Titan. Fields of study in aeolian research cover a broad spectrum ranging from dev...

  17. Wind erosion and aeolian desertification in Northern China

    NASA Astrophysics Data System (ADS)

    Tao, Wang

    2013-04-01

    Aeolian desertification is land degradation characterized by wind erosion in arid, semiarid and sub-humid regions mainly resulted from the excessive human activities on natural resources in Northern China. With along the development of economy and society, aeolian desertification/land degradation exerted increasingly profound influences on natural environment and social development. The aeolian desertification mostly occurs in the interlacing agro-pastoral region, grassland, semiarid rainfed cropland and oasis irrigated cropland regions in Northern China and the whole situation of aeolian desertification comes to depravation as well as only part of the desertified land had been controlled. China, as one of the countries facing with severe desertification problems, has made some progresses in understanding and combating the process of aeolian desertification through many years of hard work. Based on existing experiences and research achievements, this paper briefly discusses the causes, developmental processes, assessment and control mechanism of aeolian desertification in Northern China so as to provide some basic experiences for the further study and combating the aeolian desertification. Keywords: aeolian desertification, cause and process, assessment, desertified land control

  18. Aeolian sediment transport in vegetation canopies

    NASA Astrophysics Data System (ADS)

    Gromke, C.; Walter, B.; Burri, K.; Graf, F.; Lehning, M.

    2011-12-01

    Wind erosion experiments in grass canopies performed in the atmospheric boundary layer wind tunnel of the WSL Institute for Snow and Avalanche Research SLF in Davos / Switzerland are presented. The experiments were made using an 8 m long vegetation on sand (grain size 0.4 - 0.8 mm) fetch such that a naturally turbulent boundary layer could develop. The vegetation canopy consisted of regularly arrayed artificial grass tussocks which adequately mimic the aerodynamic and structural characteristics of vegetation with regard to flexibility and porosity. Three canopy densities and an unplanted, bare sand surface for reference were investigated. High speed imaging techniques were employed to study aeolian sediment transport over the final meter of the wind tunnel fetch. Moving particle trajectories were analysed by means of Particle Tracking Velocimetry (PTV). Sediment mass flux and concentration profiles were analysed using Shadow Imaging. The results of the particle trajectory analysis are presented in a statistical framework in terms of ejection and impact angle, trajectory length and curvature and particle velocity. Differences between aeolian sediment transport in / over vegetation canopies and the reference bare sand surface are pointed out. The previous observations of Burri et al. (2011), which revealed characteristic differences in the sediment mass flux profiles above a bare and vegetated surface, are now quantitatively explained by the trajectory analysis. Whereas the mass flux profile was steadily decreasing with height above ground for the bare surface, a peak at about twice the canopy height was found for the vegetated surface. The particle trajectory analysis plays a key role in distinguishing the diverse mechanisms leading to this elevated peak. The sediment mass flux and concentration profiles are additionally evaluated with respect to the height-dependency of particle size distributions. The trajectory analysis results are considered to have a high

  19. Deciphering human-climate interactions in an ombrotrophic peat record: REE, Nd and Pb isotope signatures of dust supplies over the last 2500 years (Misten bog, Belgium)

    NASA Astrophysics Data System (ADS)

    Fagel, N.; Allan, M.; Le Roux, G.; Mattielli, N.; Piotrowska, N.; Sikorski, J.

    2014-06-01

    A high-resolution peat record from Eastern Belgium reveals the chronology of dust deposition for the last 2500 years. REE and lithogenic elements in addition to Nd and Pb isotopes were measured in a 173 cm age-dated peat profile and provide a continuous chronology of dust source and intensity. Calculated dust flux show pronounced increases c. 300 BC, 600 AD, 1000 AD, 1200 AD and from 1700 AD, corresponding to local and regional human activities combined with climate change. The Industrial Revolution samples (1700-1950 AD) are characterised by a significant enrichment in Sc-normalised REE abundance (sum REE/Sc > 25) due to intensive coal combustion. For the pre-Industrial Revolution samples, the Sc-normalised REE abundance (10 < Sum REE/Sc < 25) and the εNd variability (-13 to -9) are interpreted by a mixing between dust particles from local soils and long-range transport of desert particles. Three periods characterised by dominant-distal sources (c. 320 AD, 1000 AD and 1700 AD) are consistent with local wetter-than-average intervals as indicated by a lower degree of peat humification. Local erosion prevails during the drier (higher humification) intervals (100 AD, 600 AD). On a global scale, more distal supplies are driven during colder periods, in particular during the Oort and Maunder minima, suggesting a potential link between dust deposition and global climate. Combining REE abundance, fractionation between Light REE and Heavy REE and Nd isotope data in ombrotrophic peat allows one to distinguish between dust flux changes related to human and climate forcings.

  20. The sensitivity of the southwest monsoon phytoplankton bloom to variations in aeolian iron deposition over the Arabian Sea

    NASA Astrophysics Data System (ADS)

    Wiggert, Jerry D.; Murtugudde, Raghu G.

    2007-05-01

    A coupled, 3-D biophysical ocean general circulation model is used to investigate how aeolian iron deposition affects the Arabian Sea ecosystem. Two separate aeolian iron deposition fields, derived from the GISS and GOCART atmospheric transport models, have been applied as surface boundary conditions. The model results exhibit widespread biogeochemical sensitivity to the choice of deposition field. With GOCART deposition, SW Monsoon phytoplankton blooms in the western and central Arabian Sea are enhanced and exhibit greater realism. The central Arabian Sea bloom is supported by supplemental input of horizontally advected iron from a pool that undergoes a yearlong progression that begins in the Gulf of Oman, where the difference in aeolian iron enrichment between the two deposition fields is most prevalent. The GOCART-enhanced blooms result in a more pronounced shift toward netplankton, an increase in euphotic zone export flux of up to a 20% during the SW Monsoon and an additional annual biogenic export of 3.5 TgC. The potential ramifications of regional N-cycle alteration through stimulation of N2-fixation that is promoted by significant aeolian mineral flux needs to be explored. The canonical thinking that the northern Arabian Sea is invariably iron replete is now being challenged by both our model results and recent observational studies. As well, our results indicate that Arabian Sea iron concentrations are strongly modulated by the specific nature of aeolian mineral deposition. Thus climate or land use influences on dust mobilization could exercise leading-order controls on regional biogeochemical variability, metabolic status and air-sea exchanges of CO2.

  1. High-resolution provenance of desert dust deposited on Mt. Elbrus, Caucasus in 2009-2012 using snow pit and firn core records

    NASA Astrophysics Data System (ADS)

    Kutuzov, S.; Shahgedanova, M.; Mikhalenko, V.; Ginot, P.; Lavrentiev, I.; Kemp, S.

    2013-09-01

    The first record of dust deposition events on Mt. Elbrus, Caucasus Mountains derived from a snow pit and a shallow firn core is presented for the 2009-2012 period. A combination of isotopic analysis, SEVIRI red-green-blue composite imagery, MODIS atmospheric optical depth fields derived using the Deep Blue algorithm, air mass trajectories derived using the HYSPLIT model and analyses of meteorological data enabled identification of dust source regions with high temporal (hours) and spatial (ca. 20-100 km) resolution. Seventeen dust deposition events were detected; fourteen occurred in March-June, one in February and two in October. Four events originated in the Sahara, predominantly in northeastern Libya and eastern Algeria. Thirteen events originated in the Middle East, in the Syrian Desert and northern Mesopotamia, from a mixture of natural and anthropogenic sources. Dust transportation from Sahara was associated with vigorous Saharan depressions, strong surface winds in the source region and mid-tropospheric southwesterly flow with daily winds speeds of 20-30 m s-1 at 700 hPa level. Although these events were less frequent than those originating in the Middle East, they resulted in higher dust concentrations in snow. Dust transportation from the Middle East was associated with weaker depressions forming over the source region, high pressure centred over or extending towards the Caspian Sea and a weaker southerly or southeasterly flow towards the Caucasus Mountains with daily wind speeds of 12-18 m s-1 at 700 hPa level. Higher concentrations of nitrates and ammonium characterised dust from the Middle East deposited on Mt. Elbrus in 2009 indicating contribution of anthropogenic sources. The modal values of particle size distributions ranged between 1.98 μm and 4.16 μm. Most samples were characterised by modal values of 2.0-2.8 μm with an average of 2.6 μm and there was no significant difference between dust from the Sahara and the Middle East.

  2. A Fractal Model for the Capacitance of Lunar Dust and Lunar Dust Aggregates

    NASA Technical Reports Server (NTRS)

    Collier, Michael R.; Stubbs, Timothy J.; Keller, John W.; Farrell, William M.; Marshall, John; Richard, Denis Thomas

    2011-01-01

    Lunar dust grains and dust aggregates exhibit clumping, with an uneven mass distribution, as well as features that span many spatial scales. It has been observed that these aggregates display an almost fractal repetition of geometry with scale. Furthermore, lunar dust grains typically have sharp protrusions and jagged features that result from the lack of aeolian weathering (as opposed to space weathering) on the Moon. A perfectly spherical geometry, frequently used as a model for lunar dust grains, has none of these characteristics (although a sphere may be a reasonable proxy for the very smallest grains and some glasses). We present a fractal model for a lunar dust grain or aggregate of grains that reproduces (1) the irregular clumpy nature of lunar dust, (2) the presence of sharp points, and (3) dust features that span multiple scale lengths. We calculate the capacitance of the fractal lunar dust analytically assuming fixed dust mass (i.e. volume) for an arbitrary number of fractal levels and compare the capacitance to that of a non-fractal object with the same volume, surface area, and characteristic width. The fractal capacitance is larger than that of the equivalent non-fractal object suggesting that for a given potential, electrostatic forces on lunar dust grains and aggregates are greater than one might infer from assuming dust grains are sphericaL Consequently, electrostatic transport of lunar dust grains, for example lofting, appears more plausible than might be inferred by calculations based on less realistic assumptions about dust shape and associated capacitance.

  3. Proxies and measurement techniques for mineral dust in Antarctic ice cores.

    PubMed

    Ruth, Urs; Barbante, Carlo; Bigler, Matthias; Delmonte, Barbara; Fischer, Hubertus; Gabrielli, Paolo; Gaspari, Vania; Kaufmann, Patrik; Lambert, Fabrice; Maggi, Valter; Marino, Federica; Petit, Jean-Robert; Udisti, Roberto; Wagenbach, Dietmar; Wegner, Anna; Wolff, Eric W

    2008-08-01

    To improve quantitative interpretation of ice core aeolian dust records, a systematic methodological comparison was made. This involved methods for water-insoluble particle counting (Coulter counter and laser-sensing particle detector), soluble ion analysis (ion chromatography and continuous flow analysis), elemental analysis (inductively coupled plasma mass spectroscopy at pH 1 and after full acid digestion), and water-insoluble elemental analysis (proton induced X-ray emission). Antarctic ice core samples covering the last deglaciation from the EPICA Dome C (EDC) and the EPICA Dronning Maud Land (EDML) cores were used. All methods correlate very well among each other, but the ratios of glacial age to Holocene concentrations, which are typically a factor approximately 100, differ between the methods by up to a factor of 2 with insoluble particles showing the largest variability. The recovery of ICP-MS measurements depends on the digestion method and is differentfor different elements and during different climatic periods. EDC and EDML samples have similar dust composition, which suggests a common dust source or a common mixture of sources for the two sites. The analyzed samples further reveal a change of dust composition during the last deglaciation.

  4. Earth and planetary aeolian streaks: A review

    NASA Astrophysics Data System (ADS)

    Cohen-Zada, Aviv Lee; Blumberg, Dan Gabriel; Maman, Shimrit

    2016-03-01

    Wind streaks are abundant aeolian features that have been observed on planetary surfaces by remote sensing means. They have been widely studied, particularly on Mars and Venus and to a much lesser extent on Earth. In imagery, these streaks appear as elongated features that are easily distinguishable from their surroundings. Geomorphologically, these streaks have, thus far, been interpreted as the presence or absence of small loose particles on the surface, deposited or eroded, respectively, by wind. However, the use of different (optical and radar) remote-sensing tools to study wind streaks has led to uncertain interpretations of these features and has hindered their geomorphological definition. Since wind streaks indicate the prevailing wind direction at the time of their formation, they may be used to map near-surface winds and to estimate atmospheric circulation patterns. The aim of this article is to review the main studies focusing on wind streaks and to present the most up-to-date knowledge on this topic. Moreover, a new perspective for wind streak research is suggested: As 'wind streak' is a collective term for a variety of aeolian features that when viewed from above appear as distinctive albedo surface patterns, we suggest that the term should not be used to refer to a geomorphological feature. Since the definition of wind streaks is constrained to remote sensing rather than to geomorphology and is affected by the inherent biases of remote sensing methods, we suggest that 'wind streaks' should be used as a collective term for aeolian surfaces that are discernable from above as bright and dark patterns due to alterations in the characteristics of the surface or to the presence of bedforms. To better understand the mechanisms, time-frames, climate compatibility of wind streaks and the influences of remote sensing on their appearance, we have compiled a new database containing more than 2,900 Earth wind streaks. A comprehensive study of these Earth wind

  5. Geometric aeolian dune crest migration model

    NASA Astrophysics Data System (ADS)

    Swanson, T.; Mohrig, D. C.; Kocurek, G.; Pedersen, A.

    2012-12-01

    We present a geometric aeolian dune crest model that provides a predictive linkage between local lee face sediment deposition and wholesale landform change. The model is driven using an initial condition of 3D dune crest data obtained from a time series of airborne LIDAR surveys of White Sands, NM, and wind observations from nearby Holloman AFB. Transient dune migration is modeled by volume filling of a simple theoretical dune geometry with sediment flux derived using shear velocity dependent transport (Bagnold, 1941) modified by a new incidence angle dependent lee face sediment deposition function styled after Rubin and Hunter (1985). Model calibration is achieved using an azimuthal wind direction correction and threshold values for shear velocity dependent sediment transport. Agreement between observations and model results are presented using a l2 norm representing a global error estimate.

  6. Abrasion by aeolian particles: Earth and Mars

    NASA Technical Reports Server (NTRS)

    Greeley, R.; Marshall, J. R.; White, B. R.; Pollack, J. B.; Marshall, J.; Krinsley, D.

    1984-01-01

    Estimation of the rate of aeolian abrasion of rocks on Mars requires knowledge of: (1) particle flux, (2) susceptibilities to abrasion of various rocks, and (3) wind frequencies on Mars. Fluxes and susceptibilities for a wide range of conditions were obtained in the laboratory and combined with wind data from the Viking meteorology experiment. Assuming an abundant supply of sand-sized particles, estimated rates range up to 2.1 x 10 to the minus 2 power cm of abrasion per year in the vicinity of Viking Lander 1. This rate is orders of magnitude too great to be in agreement with the inferred age of the surface based on models of impact crater flux. The discrepancy in the estimated rate of abrasion and the presumed old age of the surface cannot be explained easily by changes in climate or exhumation of ancient surfaces. The primary reason is thought to be related to the agents of abrasion. At least some sand-sized (approx. 100 micrometers) grains appear to be present, as inferred from both lander and orbiter observations. High rates of abrasion occur for all experimental cases involving sands of quartz, basalt, or ash. However, previous studies have shown that sand is quickly comminuted to silt- and clay-sized grains in the martian aeolian regime. Experiments also show that these fine grains are electrostatically charged and bond together as sand-sized aggregates. Laboratory simulations of wind abrasion involving aggregates show that at impact velocities capable of destroying sand, aggregates from a protective veneer on the target surface and can give rise to extremely low abrasion rates.

  7. High Latitude Dust in the Earth System

    NASA Technical Reports Server (NTRS)

    Bullard, Joanna E.; Baddock, Matthew; Bradwell, Tom; Crusius, John; Darlington, Eleanor; Gaiero, Diego; Gasso, Santiago; Gisladottir, Gudrun; Hodgkins, Richard; McCulloch, Robert; McKenna-Neuman, Cheryl; Mockford, Tom; Stewart, Helena; Thorsteinsson, Throstur

    2016-01-01

    Natural dust is often associated with hot, subtropical deserts, but significant dust events have been reported from cold, high latitudes. This review synthesizes current understanding of high-latitude (> or = 50degN and > or = 40degS) dust source geography and dynamics and provides a prospectus for future research on the topic. Although the fundamental processes controlling aeolian dust emissions in high latitudes are essentially the same as in temperate regions, there are additional processes specific to or enhanced in cold regions. These include low temperatures, humidity, strong winds, permafrost and niveo-aeolian processes all of which can affect the efficiency of dust emission and distribution of sediments. Dust deposition at high latitudes can provide nutrients to the marine system, specifically by contributing iron to high-nutrient, low-chlorophyll oceans; it also affects ice albedo and melt rates. There have been no attempts to quantify systematically the expanse, characteristics, or dynamics of high-latitude dust sources. To address this, we identify and compare the main sources and drivers of dust emissions in the Northern (Alaska, Canada, Greenland, and Iceland) and Southern (Antarctica, New Zealand, and Patagonia) Hemispheres. The scarcity of year-round observations and limitations of satellite remote sensing data at high latitudes are discussed. It is estimated that under contemporary conditions high-latitude sources cover >500,000 sq km and contribute at least 80-100 Tg/yr1 of dust to the Earth system (approx. 5% of the global dust budget); both are projected to increase under future climate change scenarios.

  8. Peat bog records of dust deposition over the last 2000 years in the Dolomites (NE Italian Alps)

    NASA Astrophysics Data System (ADS)

    Poto, Luisa; Segnana, Michela; Gabrieli, Jacopo; Zaccone, Claudio; Barbante, Carlo

    2016-04-01

    The reconstruction of dust composition and fluxes is crucial to help to understand climate variability and climate changes. Dust fluctuations, linked to changes in dry and wet depositions, can indicate more humid or arid conditions, changes in temperature, vegetation cover and wind regimes. Peatlands are unique terrestrial archives that can capture changes in atmospheric deposition over time. Among them, ombrotrophic environments are hydrologically isolated from the surrounding landscapes receiving all the nutrients from precipitation and wind, with no influence from streams and groundwater. In recent decades biological and chemical proxies from peat bogs were extensively used to trace past climate changes, and rare earth elements (REE) in particular have been developed as inorganic geochemical proxies of mineral dust input in the atmosphere that plays an important role in the marine and terrestrial biogeochemical cycle as source for both major and trace elements. Dust deposition in the Italian Alps during the last 2000 years is estimated from the geochemical signature of two ombrotrophic peatlands. The first bog is located in Danta di Cadore (Belluno province, 1400 m a.s.l.), the second one in Coltrondo (Belluno province, 1800 m a.s.l.): they both allow us to have new insights into climate variability in the Eastern sector of the Italian Alps. The REE and the lithogenic elements concentration, as well as the lead isotopic composition were determined by CRC-ICP-QMS along the first meter of each core. For both the archives chronology is based upon independent 14C and 210Pb measurements. Changes in REE concentration through the bogs were related with those of lithogenic elements in order to test the immobility of the REE. Moreover peat humification degree was used to evaluate the hydroclimatic conditions of the bogs and Pb isotopic signature were used to trace dust deposited at Danta di Cadore and Coltrondo bogs and to discriminate natural from anthropogenic source

  9. A review of the chronologies and geomorphology of the aeolian landforms in the northwestern Negev dunefield (Israel)

    NASA Astrophysics Data System (ADS)

    Roskin, Joel

    2015-04-01

    The northwestern (NW) Negev Desert dunefield covering an area of only 1,300 km2, comprises the eastern end of the northern Sinai Peninsula - NW Negev erg and is probably the most densely dated dune body in the INQUA Dunes Atlas chronologic database. Over 230 luminescence ages (TL, IRSL, and mainly OSL) and radiocarbon dates have been retrieved over the past course of 20 years from calcic and sandy palaeosols serving as dune substrates, sand sheets, vegetated linear dunes (VLDs), fluvial deposits, and archaeological sites. Despite being from different deposit types and aeolian morphologies, and based on different methodologies, the chronologies usually show good compatibility. By reviewing and reassessing the significance of the Eastern Mediterranean INQUA Dunes Atlas chronologies, along with detailed stratigraphic, structural and geomorphologic data and understandings, the major, and possibly extreme, episodes of aeolian activity and stability are outlined. Repetitive chronostratigraphic sequences in VLDs indicate that this dune type, at least in the Negev, comprises a reliable recorder of main dune mobilization periods. This presentation demonstrates that certain combinations of research finds, using different OSL dating strategies and other regional and local late Quaternary records and in particular aeolian ones, are required assets for providing for acceptable local and regional palaeoclimatic interpretations. The distribution of the VLD chronologies points to rapid mobilization during the Heinrich 1 and Younger Dryas, characterized by powerful winds, though VLDs also form in late Holocene palaeoenvironments. Time slices illustrate the different sensitivities of the studied aeolian landforms to the source, availability, and supply of sediment; long- and short-term climate change, local human-induced environmental changes and also their joint effects, that enable evaluation of aeolian responses to future environmental and climate changes.

  10. Multi-Technique Study of a Martian Aeolian Sand Analog

    NASA Technical Reports Server (NTRS)

    Kuhlman, K.; Marshall, J.; Evans, N. D.; Luttge, A.

    2001-01-01

    Potential scientific returns from technological advances in various forms of microscopy and benchmarking of currently available in-situ measurements using an aeolian red dune sand from the central Australian desert. Additional information is contained in the original extended abstract.

  11. Multi-Technique Study of a Martian Aeolian Sand Analog

    NASA Astrophysics Data System (ADS)

    Kuhlman, K. R.; Marshall, J.; Evans, N. D.; Luttge, A.

    2001-03-01

    Potential scientific returns from technological advances in various forms of microscopy and benchmarking of currently available in-situ measurements using an aeolian red dune sand from the central Australian desert.

  12. A note on the stochastic nature of particle cohesive force and implications to threshold friction velocity for aerodynamic dust entrainment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is considerable interest to determine the threshold for aeolian dust emission on Earth and Mars. Existing schemes for threshold friction velocity are all deterministic in nature, but observations show that in the dust particle size range the threshold friction velocity scatters strongly due t...

  13. Recent seasonal variations in arid landscape cover and aeolian sand mobility, Navajo Nation, southwestern U.S.

    USGS Publications Warehouse

    Draut, Amy E.; Redsteer, Margaret Hiza; Amoroso, Lee; Giosan, Liviu; Fuller, Dorian Q.; Nicoll, Kathleen; Flad, Rowan K.; Clift, Peter D.

    2013-01-01

    The socioeconomic impacts of climate change pose problems not only in devel- oping countries but also to residents of arid lands in the United States among marginalized societies with limited economic means. In the Navajo Nation, warming temperatures and recent drought have increased aeolian sediment mobility such that large, migrating sand dunes affect grazing lands, housing, and road access. Dust derived from this region also affects albedo and longevity of the Rocky Mountains snowpack, located downwind. We present initial results from a study that monitors sand transport and vegetation within a 0.2 km2 site in the Navajo lands, measuring the effects of drought on landscape stability since 2009. Sand mobility decreased substantially as 1 year with near-normal monsoon rainfall (2010) somewhat abated a decade-long drought, temporarily doubling vegetation cover. Vegetation that grew during 2010, with adequate rain, died off rapidly during dry conditions in 2011. Short-term increases in rainfall that promote annual, but not perennial, plant growth will not improve landscape stability in the long term. Climate projections suggest that a warmer, drier climate and potentially enhanced sediment supply from ephem- eral washes will further increase aeolian sand transport and dune activity, worsening the present challenges to people living in this region. Connections among climate, vegetation, and aeolian sediment erodibility in this region are highly relevant to other areas of the world with similar environmental problems.

  14. Change in dust and fluvial deposition variability in the Peruvian central continental coast during the last millennium: Response of the ocean atmospheric systems.

    NASA Astrophysics Data System (ADS)

    Sifeddine, A.; Briceño, F. J., Sr.; Caquineau, S.; Velazco, F.; Salvatecci, R.; Ortlieb, L.; Gutierrez, D.; Cardich, J.; Almeida, C.

    2014-12-01

    The particles from aeolian or fluvial origin are a useful proxy for the reconstruction of atmospheric condition patterns in the past. Changes in continental aridity and the atmospheric condition determine the composition and amount of lithogenic material and the way of transport from the continent. Here we present a record of laminated sediments (core B040506) retrieved in the continental shelf off Peru. Wind long-term suspension (regional) and local aeolian transport during the last millennium (transition from Medieval Climate Anomaly (MCA) to Little Ice Age (LIA) and the current warm period (CWP)) at centennial to decadal resolution are characterized. The particle provenance and grain size components are discussed using a mathematical model of fractionation. This model assumes that lithological composition of the sediment is an assemblage of several log-normally distributed particle populations. In this way, an interactive least square fitting routine is used to fit the particle grain size collected with the mathematical expression. This allows inferring the spatial and temporal variation of particle populations and thus the transport mechanisms involved. Our results showed a decrease in aeolian transport from the MCA - LIA transition and during the LIA with except of the local aeolian transport that shows peaks during the LIA. This decrease during LIA is accompanied by an enhanced fluvial transport. During the CWP the aeolian transport (Paracas dust storm and wind long-term suspension) display a high variability and tendency to increase in detriment of runoff. Comparison with other South American records indicates that those changes are linked to change in the shift of the ITCZ and Pacific high at the centennial time resolution. Finally the great increase of the fluvial transport within the transition of the LIA to the CWP is synchronous to severe drought period recorded in the Indo-Pacific region indicating higher frequency of El Niño events. Hence these

  15. Dust Accumulation and Cleaning of the MER Opportunity Solar Array

    NASA Astrophysics Data System (ADS)

    Herman, J.

    2015-12-01

    The solar array of the NASA Mars Exploration Rover (MER) Opportunity was expected to accumulate a sufficient quantity of dust after ninety Martian days (sols) such that it could no longer provide enough energy to guarantee continued surface operations. Instead, due in part to low dust accumulation rates and numerous dust cleaning events, Opportunity continues to operate on the Martian surface for over 4000 sols (over six Mars years). During this time period, the rover experienced six Martian winters and several dust storms. Because the sources of solar energy loss are known, the solar array energy output offers a method to scientifically estimate the loading and aeolian removal of dust from the solar array each sol. We will discuss the accumulation of dust on the solar panels as a proxy for dust movement at Meridiani Planum over the course of the entire mission to date.

  16. Dust Accumulation and Cleaning of the MER Spirit Solar Array

    NASA Astrophysics Data System (ADS)

    Herman, J. A.; Lemmon, M. T.; Johnson, J. R.; Cantor, B. A.; Stella, P. M.; Chin, K. B.; Wood, E. G.

    2012-12-01

    The solar array of the NASA Mars Exploration Rover (MER) Spirit was expected to accumulate so much dust after ninety Martian days (sols) that it could no longer provide enough energy to guarantee continued surface operations. Instead, due in part to low dust accumulation rates and numerous dust cleaning events, Spirit carried out surface operations for over 2200 sols (over three Mars years). During this time period, the rover experienced four Martian winters and several dust storms. Because the sources of solar energy loss are known, the solar array energy output offers a tool to quantitatively estimate the loading and aeolian removal of dust from the solar array each sol. We will discuss the accumulation of dust on the solar panels as a proxy for dust movement at Gusev Crater over the course of the entire mission.

  17. Dust Accumulation and Cleaning of the MER Solar Arrays

    NASA Astrophysics Data System (ADS)

    Herman, J. A.; Lemmon, M. T.; Stella, P.; Chin, K. B.; Wood, E. G.

    2010-12-01

    The solar arrays of the two NASA Mars Exploration Rovers (MER), Spirit and Opportunity, were expected to accumulate so much dust after 90 Martian days (sols) that they could no longer provide enough energy to guarantee continued surface operations. Instead, due in part to low dust accumulation rates and numerous dust cleaning events, they have carried out surface operations for over 2200 sols each. During this time period, the rovers experienced four Martian winters and several dust storms. Because the sources of solar energy loss are known, the solar array energy output offers a tool to scientifically estimate the loading and aeolian removal of dust from the solar arrays each sol. We will discuss the accumulation of dust on the solar panels as a proxy for dust movement on the Martian surface over the last 6 years.

  18. Late Quaternary aeolian sand deposition sustained by fluvial reworking and sediment supply in the Hexi Corridor - An example from northern Chinese drylands

    NASA Astrophysics Data System (ADS)

    Nottebaum, Veit; Lehmkuhl, Frank; Stauch, Georg; Lu, Huayu; Yi, Shuangwen

    2015-12-01

    Aeolian deposits are frequently used for palaeoenvironmental change studies. Their formation depends on an array of requirements: the supply of material suitable for aeolian transport and favorable conditions of sediment availability and wind strength. In order to infer palaeoenvironmental information from aeolian sand deposits these factors need to be carefully evaluated. We present a study from northern Chinese Hexi Corridor, based on 11 optically stimulated luminescence (OSL) dated sediment sections. These represent interchanging aeolian and alluvial deposits under gravel surfaces and aeolian sand in dune fields interrupted by interdunal flood deposits. Investigations in two subareas reveal contrasting geomorphologic and sedimentary histories: (1) sediment deposition during the Pleistocene-Holocene transition (~ 12 ka) followed by deflation during the Holocene and (2) frequent sediment recycling revealed by a wide spectrum of ages throughout the Holocene. The late glacial sediment pulse recorded in the western Hexi Corridor is attributed to high sediment supply, generated by efficient (peri-)glacial sediment production during glacial times in the adjacent Qilian Shan (< 5700 m asl) and a moisture increase inducing the reworking of those (glacio-)fluvial deposits during the Pleistocene-Holocene transition. The absence of a powerful reworking agent preserved these late glacial deposits in the western Hexi Corridor in contrast to moister eastern parts where Holocene sediment reworking prevailed. Geomorphological and hydrological preconditions of the subareas are discussed and reveal the controlling influence of fluvial processes on sand supply for the aeolian system. While a perennial drainage is missing in the drier western part, the Hei River drainage is fed by higher monsoonal precipitation in the central Hexi Corridor. It maintains a sediment recycling system and has ensured a sufficient sediment supply throughout the Holocene. The study promotes closer

  19. An analytical framework for aeolian saltation

    NASA Astrophysics Data System (ADS)

    Reitz, M. D.; Jerolmack, D. J.

    2011-12-01

    The process of aeolian saltation has been a focus of extensive research, but analytical solutions for the balance between the flux of grains and the adjustment of the wind velocity profile have yet to be described. Because several of the functional relationships between variables could not be known a priori, as for example the splash functions of the impact-induced ejection of grains from the bed, the process has been studied primarily through experiments and numerical modeling. Grain-scale experiments have now however yielded robust empirical relationships for functions such as splash function distributions, and we can use these relationships to make the aeolian saltation process analytically tractable. We construct an analytical framework for steady state saltation in terms of a threshold height, above which the wind velocity is strong enough to carry a grain from reptation to saltation. This threshold height is raised as the wind profile magnitude is lowered by the increasing number of saltating grains being accelerated by the wind, until the number of grains being demoted below this threshold equals the number being promoted. Grain demotion results from the loss of energy to collisions with the bed, while grain promotion results from the distribution of splash-ejected grains that exceed the threshold height. The balance of these populations at steady state determines both the total number of grains in saltation and the saturated wind velocity profile, while the approach to this balance describes the transient evolution to this state. We also formulate the critical impact Shields stress, defined as the stress below which transport ceases (as opposed to the higher critical fluid Shields stress at which transport is initiated). The difference between the critical fluid and impact Shields stresses also implies the existence of a minimum population of saltating grains. Finally, we extend our developed framework to comment on related open questions. We test the

  20. Sonic anemometers in aeolian sediment transport research

    NASA Astrophysics Data System (ADS)

    van Boxel, J. H.; Sterk, G.; Arens, S. M.

    2004-04-01

    Fast-response wind and turbulence instruments, including sonic anemometers, are used more and more in aeolian sediment transport research. These instruments give information on mean wind, but also on fluctuations and turbulent statistics, such as the uw covariance, which is a direct measure of Reynolds' stress (RS) and friction velocity. This paper discusses the interpretation of sonic anemometer data, the transformations needed to get proper results and turbulence spectra, and how they are influenced by instrument size, sampling frequency, and measurement height. Turbulence spectra characterize how much the different frequencies in the turbulent signals contribute to the variance of wind speed, or to the covariance of horizontal and vertical wind speed. They are important in determining the measurement strategy when working with fast-response instruments, such as sonic anemometers, and are useful for interpreting the measurement results. Choices on the type of sonic anemometer, observation height, sampling period, sampling frequency, and filtering can be made on the basis of expected high and low-frequency losses in turbulent signals, which are affected by those variables, as well as wind speed and atmospheric stability. Friction velocity and RS, important variables in aeolian sediment transport research, are very sensitive to tilt or slope errors. During a field experiment, the slope sensitivity of the RS was established as 9% per degree of slope, which is 1.5 times the value reported in literature on the basis of theoretical considerations. An important reason for the difference probably is the large influence of streamline curvature on turbulence statistics and thereby on the slope sensitivity of the RS. An error of 9% per degree of slope in the RS will translate into an error of approximately 4% per degree of slope in the calculated friction velocity. Space-time correlation of the horizontal wind speed is much larger than that of the vertical wind speed and

  1. Employing lidar to detail vegetation canopy architecture for prediction of aeolian transport

    USGS Publications Warehouse

    Sankey, Joel B.; Law, Darin J.; Breshears, David D.; Munson, Seth M.; Webb, Robert H.

    2013-01-01

    The diverse and fundamental effects that aeolian processes have on the biosphere and geosphere are commonly generated by horizontal sediment transport at the land surface. However, predicting horizontal sediment transport depends on vegetation architecture, which is difficult to quantify in a rapid but accurate manner. We demonstrate an approach to measure vegetation canopy architecture at high resolution using lidar along a gradient of dryland sites ranging from 2% to 73% woody plant canopy cover. Lidar-derived canopy height, distance (gaps) between vegetation elements (e.g., trunks, limbs, leaves), and the distribution of gaps scaled by vegetation height were correlated with canopy cover and highlight potentially improved horizontal dust flux estimation than with cover alone. Employing lidar to estimate detailed vegetation canopy architecture offers promise for improved predictions of horizontal sediment transport across heterogeneous plant assemblages.

  2. Minimal model for aeolian sand dunes.

    PubMed

    Kroy, Klaus; Sauermann, Gerd; Herrmann, Hans J

    2002-09-01

    We present a minimal model for the formation and migration of aeolian sand dunes in unidirectional winds. It combines a perturbative description of the turbulent wind velocity field above the dune with a continuum saltation model that allows for saturation transients in the sand flux. The latter are shown to provide a characteristic length scale, called saturation length, which is distinct from the saltation length of the grains. The model admits two different classes of solutions for the steady-state profile along the wind direction: smooth heaps and dunes with slip face. We clarify the origin of the characteristic properties of these solutions and analyze their scaling behavior. We also investigate in some detail the dynamic evolution of heaps and dunes, including the steady-state migration velocity and transient shape relaxation. Although the minimal model employs nonlocal expressions for the wind shear stress as well as for the sand flux, it is simple enough to serve as a very efficient tool for analytical and numerical investigations and opens up the way to simulations of large scale desert topographies. PMID:12366107

  3. Modeling aeolian erosion in presence of vegetation

    NASA Astrophysics Data System (ADS)

    Dupont, S.; Bergametti, G.; Simoëns, S.

    2014-02-01

    Semiarid landscapes are characterized by vegetated surfaces. Understanding the impact of vegetation on aeolian soil erosion is important for reducing soil erosion or limiting crop damage through abrasion or burial. In the present study, a saltation model fully coupled with a large-eddy simulation airflow model is extended to vegetated landscapes. From this model, the sensitivity of sand erosion to different arrangements and type of plants (shrub versus tree) representative of semiarid landscapes is investigated and the wind erosion reduction induced by plants is quantified. We show that saltation processes over vegetated surfaces have a limited impact on the mean wind statistics, the momentum extracted from the flow by saltating particles being negligible compared to that extracted by plants. Simulated sand erosion patterns resulting from plant distribution, i.e., accumulation and erosion areas, appear qualitatively consistent with previous observations. It is shown that sand erosion reduction depends not only on vegetation cover but also on plant morphology and plant distribution relative to the mean wind direction. A simple shear stress partitioning approach applied in shrub cases gives similar trends of sand erosion reduction as the present model following wind direction and vegetation cover. However, the magnitude of the reduction appears significantly different from one approach to another. Although shrubs trap saltating particles, trees appear more efficient than shrubs to reduce sand erosion. This is explained by the large-scale sheltering effect of trees compared to the local shrub one.

  4. Aeolian dunes as ground truth for atmospheric modeling on Mars

    USGS Publications Warehouse

    Hayward, R.K.; Titus, T.N.; Michaels, T.I.; Fenton, L.K.; Colaprete, A.; Christensen, P.R.

    2009-01-01

    Martian aeolian dunes preserve a record of atmosphere/surface interaction on a variety of scales, serving as ground truth for both Global Climate Models (GCMs) and mesoscale climate models, such as the Mars Regional Atmospheric Modeling System (MRAMS). We hypothesize that the location of dune fields, expressed globally by geographic distribution and locally by dune centroid azimuth (DCA), may record the long-term integration of atmospheric activity across a broad area, preserving GCM-scale atmospheric trends. In contrast, individual dune morphology, as expressed in slipface orientation (SF), may be more sensitive to localized variations in circulation, preserving topographically controlled mesoscale trends. We test this hypothesis by comparing the geographic distribution, DCA, and SF of dunes with output from the Ames Mars GCM and, at a local study site, with output from MRAMS. When compared to the GCM: 1) dunes generally lie adjacent to areas with strongest winds, 2) DCA agrees fairly well with GCM modeled wind directions in smooth-floored craters, and 3) SF does not agree well with GCM modeled wind directions. When compared to MRAMS modeled winds at our study site: 1) DCA generally coincides with the part of the crater where modeled mean winds are weak, and 2) SFs are consistent with some weak, topographically influenced modeled winds. We conclude that: 1) geographic distribution may be valuable as ground truth for GCMs, 2) DCA may be useful as ground truth for both GCM and mesoscale models, and 3) SF may be useful as ground truth for mesoscale models. Copyright 2009 by the American Geophysical Union.

  5. Potential source regions of dust accumulated in northern Africa

    NASA Astrophysics Data System (ADS)

    Wasowska, S.; Woronko, B.

    2012-04-01

    Sahara is the largest source of the dust in the world. The material sampled from dust storms in Tunisia (Nefta Oasis, El Kantoui Harbor), north Egypt (Alexandria) and Morocco (Mhamid Oasis) (March 2001, March and April 2009) was taken to identify the potential sources of dust accumulation and transport paths in North Africa. The samples were analyzed on grain size, micromorphology of silt grain surfaces in Scanning Electron Microscope (SEM), elemental composition of grains and their surface crusts, loss on ignition, mineralogical composition of samples and carbonate content. Additionally the meteorological situation was analyzed during the dust storm occurrences and preceding periods. The results of grain size analyses show that all studied sediments belong to the small dust type, and dust accumulated in Mhamid is the clay mineral agglomerated (CMA) dust. The source of the CMA are the old dry lake beds. Dust particles are mobilized as aggregates of clay minerals, what is controlled by structure (particle packing) of the original lake sediment, and accumulation is dry and wet as well. The results of the analysis of the quartz grain surface micromorphology, the elemental composition and loss on ignition indicate that dust accumulated in Morocco originated from a relatively homogenous sediment source and, on the other hand, dust found in Alexandria comes from a diversified source. Dust sampled in Tunisia is characterized by the highest content of carbonates and organic matter which suggests the intensive dispelling acting on the weathered material from carbonate rocks and local Mediterranean soil covers rich in CaCO3. The analyses of meteorological conditions during the dust storms and the analyses of the textural characteristics of deposits show that it is highly probable that analysed aeolian dust was transported both for shorter and longer distances. Hypothetic source areas of dust accumulated in Mhamid could be the old ergs, some located 300-500 km away like

  6. Potential dust emissions from the southern Kalahari's dunelands

    NASA Astrophysics Data System (ADS)

    Bhattachan, Abinash; D'Odorico, Paolo; Okin, Gregory S.; Dintwe, Kebonyethata

    2013-03-01

    The Southern Hemisphere shows relatively low levels of atmospheric dust concentrations. Dust concentrations could, however, increase as a result of losses of vegetation cover in the southern Kalahari. There is some evidence of an ongoing remobilization of stabilized dunefields in the southern Kalahari where dune crests with sparse vegetation cover are reactivated during dry and windy periods, a phenomenon that is predicted to intensify with increased land degradation, overgrazing, and droughts. Despite the potentially important climatic and biogeochemical implications of dust emissions from the Kalahari, it is still unclear whether the predicted remobilization of the Kalahari dunes could be associated with increased dust emissions from this region. The dependence of sediment fluxes and dust emissions on vegetation cover in the Kalahari dunelands remains poorly understood, which prevents a quantitative assessment of possible changes in aeolian activity in this region under different land use and land cover scenarios. In this study, we report the results of an aeolian sediment sampling campaign over a variety of land covers in the southern Kalahari. We use these results to quantify the potential rate of dust emissions and its dependence on vegetation cover and to make an estimate of dust fluxes from a portion of the southern Kalahari. The results show that the loss of vegetation could lead to substantial increases in dust emission and nutrient loss.

  7. Luminescence dating of Holocene aeolian sand movement, Thy, Denmark

    NASA Astrophysics Data System (ADS)

    Murray, A. S.; Clemmensen, L. B.

    2001-12-01

    We report on the application of optically stimulated luminescence dating to an investigation of the frequency of periods of aeolian sand movement and dune formation. On the coast of Thy, Holocene aeolian sediments, interleaved with peaty palaeosols, form some of the most complete successions known in western Denmark. Samples were taken from a coastal exposure, and an inland archaeological site. Dosimetry was based on laboratory gamma spectrometry, and quartz luminescence measurements used the single-aliquot regenerative-dose protocol, and 470±30 nm stimulation. The sand samples cover an age ranging from about 100 years to 4500 years; the youngest dates give us confidence that the material was well bleached at deposition. Good agreement was obtained with the radiocarbon palaeosol ages. We identify three main periods of aeolian sand movement, starting at about 4200, 2700 and 900 years ago; at least during the latter two periods significant aeolian sand movement occurred. All three phases of aeolian activity were separated by long periods of stability and soil formation. A more recent episode of dune formation, restricted to the coast and beginning less than 200 years ago, may have been triggered by modern coastal erosion.

  8. Mass-height profile and total mass transport of wind eroded aeolian sediments from rangelands of the Indian Thar Desert

    NASA Astrophysics Data System (ADS)

    Mertia, R. S.; Santra, Priyabrata; Kandpal, B. K.; Prasad, R.

    2010-11-01

    Wind erosion is an active land degradation process in the Indian Thar Desert and severe dust storm events during hot summer months in the region are very common. Assessment of soil loss due to dust storm events from major land use systems of the Indian Thar Desert is highly essential for proper environmental planning. Characterization of the mass-height profile of wind eroded aeolian sediment is an important step to compute soil loss/mass transport but was not previously studied in the region. In the present study, aeolian mass fluxes (kg m -2) at different heights from soil surface were measured at two major rangelands in the Indian Thar Desert: Overgrazing rangeland at Jaisalmer (26°55'N and 70°57'E), and controlled grazing rangeland at Chandan (27°01'N and 71°01'E). Evaluation of several mass-height profile models revealed that a power decay function [ q( z) = az-b, where q( z) is the measured mass flux at an height of z (m) from soil surface; a and b are parameters of the equation] was best to characterize the mass-height relationship of aeolian sediments from the Indian Thar Desert. The average mass transport rate (kg m -1 day -1) or the total soil loss during hot summer months was significantly higher at the overgrazed rangeland site than at the controlled grazing rangeland site. Therefore, protection of existing rangelands, which comprise about 80% geographical area of the Indian Thar Desert may check the land degradation process due to wind erosion.

  9. Three climatic cycles recorded in a loess-palaeosol sequence at Semlac (Romania) - implications for dust accumulation in the Carpathian Basin and the northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Zeeden, Christian; Hambach, Ulrich; Kels, Holger; Schulte, Philipp; Eckmeier, Eileen; Marković, Slobodan; Klasen, Nicole; Lehmkuhl, Frank

    2016-04-01

    Recent investigations of the Semlac loess section in the Southeastern Carpathian Basin, which is situated at the Mureş River in its lower reaches (Banat region, western Romanian), are presented. Dating back to marine isotope stage (MIS) 10, the more than 10 m thick loess sequence includes four fossil sol-complexes developed in homogenous relatively fine silty loess. Because good preservation and sedimentation of fine silt Semlac is regarded as a key section for the Carpathian Basin, which offers possibilities to a) improve the understanding of the type and composition of the lowland loess sequences in the Carpathian Basin also beyond the last interglacial palaeosol complex, b) to reconstruct the temporal evolution of the local loess-palaeosol successions and c) to compare the loess of the region to loess-sequences in adjacent and dust proxy data in the northern hemisphere. A strikingly sinusoidal course of physical property data with depth/time point to relatively homogenous, quasi-continuous background sedimentation of dust, interpreted as long-range transport (LRT). An integrated age model based on correlation to reference records and luminescence dating is compiled. Applying this age model we compare climate proxy data from Semlac to both global data and to data from the very southeast of the Carpathian Basin (Vojvodina, Serbia). The obtained results provide new insight into the dust accumulation regime in the Carpathian Basin and offer new palaeoenvironmental information for the region and are an important step towards establishing a catena from the thin loess-like sediments of the Banat foothills in the East towards the thicker and seemingly more complete loess sections of the southeastern and central Carpathian Basin. Disentangling grain size data from soil formation proxies gives quantitative estimates for the contribution of original sediment and weathering (through soil formation) to the present clay fraction. Patterns of clay from direct sedimentation

  10. Linking the10Be continental record of Lake Baikal to marine and ice archives of the last 50 ka: Implication for the global dust-aerosol input

    USGS Publications Warehouse

    Aldahan, A.; Possnert, G.; Peck, J.; King, J.; Colman, S.

    1999-01-01

    We present here a 10Be profile from the continental sediments of Lake Baikal (the world's largest fresh water lake), which, for the first time, shows the ??? 40 ka 10Be enhancement and a pattern that strongly matches those from the marine and ice records for the last 50 ka. This finding provides a new horizon for global and regional correlation of continental archives. Additionally, our VADM-predicted 10Be production confirms and further strengthens a common global cause (geomagnetic field intensity) for the change in atmospheric 10Be over the last 50 ka. We also show that most of the 10Be inventory to the lake has been provided by riverine input, but with a significant addition from direct precipitation and dust-aerosol fallout. We estimate a higher dust-aerosol contribution of 10Be during the Holocene and interstadial stage 3 (22-50 ka) as compared with the glacial period (12-22 ka). Copyright 1999 by the American Geophysical Union.

  11. Sedimentology of coastal chevron deposits - tsunamigenic versus aeolian origin

    NASA Astrophysics Data System (ADS)

    Garcia Garcia, A.; Spiske, M.; Tsukamoto, S.; Schmidt, V.

    2012-12-01

    The genesis of v-shaped coastal chevrons is currently controversially discussed. So far, chevrons are only described regarding their morphology, but not in terms of their origin. Two possible origins of chevrons are proposed: both aeolian transport and tsunami inundation are discussed as depositing processes. We present initial results of a detailed sedimentological survey of Holocene coastal chevrons from the American and Australian west coasts. The chevrons were measured and levelled using a differential GPS system. Large scale internal structures were recorded by ground penetrating radar imaging. Trenches were dug for sampling and analyzing small scale internal structures. The sediment samples were used for the analysis of grain-size distributions, mineral composition and content of marine microorganisms. Additional samples were taken for optically stimulated luminescence (OSL) and radiocarbon dating. Furthermore, we took reference samples from beaches, cliffs and rivers, which could act as potential sediment sources for the surveyed chevrons. Tsunami deposits are commonly polymodal, exhibit a grain-size decrease and tend to show better sorting in landward direction. Such trends are not present in the surveyed chevrons. Most samples are well to moderately well sorted and unimodal. The OSL ages decrease in transport direction and indicate a long term generation process, such as dune migration, rather than a short term event like a tsunami. This fact is additionally underlined by land snails found in different stratigraphic levels within the Australian chevrons. Furthermore, the occurrence of intercalated soil horizons implies a change of stable and active migration phases. The initial results of this study point out to an aoelian origin of coastal chevrons and do not support the previously supposed thesis of a tsunamigenic origin.

  12. Holocene environment changes around the Sara Us River, northern China, revealed by optical dating of lacustrine-aeolian sediments

    NASA Astrophysics Data System (ADS)

    Zhao, Hui; Sheng, Yongwei; Li, Bo; Fan, Yuxin

    2016-04-01

    The Sara Us River is located along the boundary of the Mu Us Desert and the Chinese Loess Plateau in northern China. The river has cut down through Quaternary sediments creating 70-80 m deep valleys with thick lacustrine/aeolian sequences exposed. We applied optical stimulated luminescence on sediments from a Holocene section of aeolian sand/lacustrine deposits in the top of the river valley. The dating results show that a humid period existed from 7.1 to 2.0 ka ago as evidenced by two layers of peat and lacustrine sediments. However, compared to other published Holocene sections in the Sara Us River valleys close to the section under studying, the local environment experienced very complicated changes during the Holocene. All of the sections recorded a period with drought and/or cold before the Holocene at around 13 ka, and an episode of aridity after about 2 ka ago as evidenced by the layers of aeolian sand. However, the ages of the lacustrine and peat layers in these sections are substantially different. Geomorphological analysis by digital elevation models does not support the existence of a mega lake covering the study area at 2 ka. The intricate environmental changes may have been caused by the meandering of the Sara Us River. Environmental changes also strongly affected human migration in this area, which is documented by Chinese historical records.

  13. Investigation of bacterial effects of Asian dust events through comparison with seasonal variability in outdoor airborne bacterial community

    PubMed Central

    Park, Jonguk; Ichijo, Tomoaki; Nasu, Masao; Yamaguchi, Nobuyasu

    2016-01-01

    Atmospheric bacterial dispersion with aeolian dust has been reported to have a potential impact on public health and ecosystems. Asian dust is a major aeolian event that results in an estimated 4 million tons of Asian dust particles falling in Japan annually, 3,000–5,000 km away from their source regions. However, most studies have only investigated the effects of Asian dust during dust seasons. Therefore, in this study, outdoor bacterial abundance and community composition were determined by 16S rRNA quantitative PCR and amplicon sequencing, respectively, and compared on Asian and non-Asian dust days (2013–2015; 44 samples over four seasons). Seasonal variations in bacterial abundance of non-Asian dust days were not observed. Bacterial abundance of individual samples collected on non-Asian dust days changed dynamically relative to Asian dust days, with bacterial abundance occasionally reaching those of Asian dust days. The bacterial community composition on non-Asian dust days was rather stable seasonally, and did not differ from that on Asian dust days. These results indicate that bacteria in Asian dust does not immediately influence indigenous bacterial communities at the phylum/class level in distant downwind areas; accordingly, further studies of bacterial communities in downwind areas closer to the dust source are warranted. PMID:27761018

  14. Self-Organised Criticality at the Onset of Aeolian Sediment Transport.

    NASA Astrophysics Data System (ADS)

    McMenamin, R.; Cassidy, R.; McCloskey, J.

    2002-12-01

    Despite decades of rigorous investigation, reliable prediction of aeolian sediment transport rates remains impossible. Transport rate formulae are based on the governing principle of steady state equilibrium such that wind velocity produces a linear response in sediment flux. Field experiments, however, demonstrate a highly non-linear response and considerable deviation exists between observed and predicted transport rates. The limited predictive ability of the transport rate equations is largely attributed to crude measurement techniques that characterise wind velocity and sediment flux as time averaged values on the order of minutes, effectively concealing a time scale on the order of seconds in which the equilibrium condition is established. All attempts to resolve a characteristic time scale persistently reveal complexity. From the study of multi-component systems, it is now becoming apparent that such non-linearity is a pervasive attribute of system dynamics. Wind tunnel experiments were conducted to examine the nature of steady state sand transport under uniform forcing. Images of grains traversing an illuminated plane in the tunnel were acquired by video camera at a rate of 10 frames per second. A suite of image analysis techniques were then applied to quantify the volume of sand recorded in sequences of thousands of images and a transport time series generated. Wind velocity measurements were also acquired simultaneously with transport measurements. In contradiction to the steady state hypothesis, sand transport events obeyed a clear power-law scaling (number - size) over about 2.5 orders of magnitude, consistent with the dynamics of self-organised critical systems and suggesting that the dynamics of aeolian sediment transport are similar to those of avalanches observed in a sand pile. Such systems are inherently unpredictable - a fact which may contribute to our understanding of the intractability of the aeolian transport problem.

  15. Measurements of wind, aeolian sand transport, and precipitation in the Colorado River corridor, Grand Canyon, Arizona; January 2005 to January 2006

    USGS Publications Warehouse

    Draut, Amy E.; Rubin, David M.

    2006-01-01

    This report presents measurements of aeolian sediment-transport rates, wind speed and direction, and precipitation records from six locations that contain aeolian deposits in the Colorado River corridor through Grand Canyon, Grand Canyon National Park, Arizona. Aeolian deposits, many of which contain and preserve archaeological material, are an important part of the Grand Canyon ecosystem. This report contains data collected between January 2005 and January 2006, and is the second in a series; the first contained data that were collected between November 2003 and December 2004 (Draut and Rubin, 2005; http://pubs.usgs.gov/of/2005/1309/). Analysis of data collected in 2005 shows great spatial and seasonal variation in wind and precipitation patterns. Total annual rainfall can vary by more than a factor of two over distances ~ 10 km. Western Grand Canyon received substantially more precipitation than the eastern canyon during the abnormally wet winter of 2005. Great spatial variability in precipitation indicates that future sedimentary and geomorphic studies would benefit substantially from continued or expanded data collection at multiple locations along the river corridor, because rainfall records collected by NPS at Phantom Ranch (near river-mile 88) cannot be assumed to apply to other areas of the canyon. Wind velocities and sand transport in 2005 were greatest during May and June, with maximum winds locally as high as ~25 m s-1, and transport rates locally >100 g cm-1 d-1. This represents a later peak in seasonal aeolian sand transport compared to the previous year, in which transport rates were greatest in April and May 2004. Dominant wind direction varies with location, but during the spring windy season the greatest transport potential was directed upstream in Marble Canyon (eastern Grand Canyon). At all locations, rates of sand transport during the spring windy season were 5–15 times higher than at other times of year. This information has been used to

  16. Late Pleistocene and Holocene aeolian sedimentation in Gonghe Basin, northeastern Qinghai-Tibetan Plateau: Variability, processes, and climatic implications

    NASA Astrophysics Data System (ADS)

    Qiang, Mingrui; Jin, Yanxiang; Liu, Xingxing; Song, Lei; Li, Hao; Li, Fengshan; Chen, Fahu

    2016-01-01

    evapotranspiration at a local scale, played an important role in sand mobility and deposition. The effect of vegetation on sand mobility is also suggested by independent evidence of aeolian activity from Genggahai Lake in the Gonghe Basin. Here, the deposition of aeolian sand in the basin during the early- to mid-Holocene indicates a low level of effective moisture caused by high evaporation induced by higher summer insolation, despite the coeval increased regional precipitation recorded by lacustrine sediments. In contrast, late Holocene palaeosols represent a high level of effective moisture, and their formation did not necessarily require increased regional precipitation. Overall, our results suggest that the relationship between aeolian activity and regional climate change is complex, and that sand accumulations do not represent the consistent action of surface processes that are related to climatic changes.

  17. Dust climatology of the western United States

    SciTech Connect

    Changery, M.J.

    1983-04-01

    Beginning and ending times of dust-caused visibility values were extracted from original records for approximately 180 stations in the western US for the general period of record 1948 to 1977. Maps are presented depicting the annual total number of hours with visibility below specified values, annual number of dust episodes, dust episode durations, season of occurrence, and probability of thunderstorm-inducement.

  18. Lunar and Planetary Science XXXV: Martian Aeolian and Mass Wasting Processes: Blowing and Flowing

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The session Martian Aeolian and Mass Wasting Processes: BLowing and Flowing included the following topics: 1) Three Decades of Martian Surface Changes; 2) Thermophysical Properties of Isidis Basin, Mars; 3) Intracrater Material in Eastern Arabia Terra: THEMIS, MOC, and MOLA Analysis of Wind-blown Deposits and Possible High-Inertia Source Material; 4) Thermal Properties of Sand from TES and THEMIS: Do Martian Dunes Make a Good Control for Thermal Inertia Calculations? 5) A Comparative Analysis of Barchan Dunes in the Intra-Crater Dune Fields and the North Polar Sand Sea; 6) Diluvial Dunes in Athabasca Valles, Mars: Morphology, Modeling and Implications; 7) Surface Profiling of Natural Dust Devils; 8) Martian Dust Devil Tracks: Inferred Directions of Movement; 9) Numerical Simulations of Anastomosing Slope Streaks on Mars; 10) Young Fans in an Equatorial Crater in Xanthe Terra, Mars; 11) Large Well-exposed Alluvual Fans in Deep Late-Noachian Craters; 12) New Evidence for the Formation of Large Landslides on Mars; and 13) What Can We Learn from the Ages of Valles Marineris Landslides on Martian Impact History?

  19. Spatial and Temporal Variability of Fugitive Dust Flux from Colorado Plateau Landscapes

    NASA Astrophysics Data System (ADS)

    Flagg, C.; Neff, J.; Reynolds, R. L.; Belnap, J.

    2011-12-01

    C. Flagg, J.C. Neff, R.L. Reynolds, J. Belnap Aeolian dust can influence nutrient availability, soil fertility, plant interactions, and water-holding capacity. Vegetation, ground cover, land-use, and climate patterns affect dust flux in different ways. Measuring dust emission and deposition can reveal spatial and temporal patterns of dust flux, informing geologic, atmospheric, and ecological models, as well as elucidating important controls over dust emission. Previous studies have documented the effects of these characteristics on dust flux in several arid and semi-arid areas, but, to date, few have focused on Colorado Plateau landscapes. We have developed a network of 108 horizontal dust collectors spanning numerous types of ecosystems, soil types, land-use histories, and geologic bedrock and settings covering about 4400 square km across southeastern Utah. The sample archive dates to early 2008 and is currently the largest known record of fugitive dust emission for the southwestern United States. Every 3-4 months, samples were collected from the sediment traps at heights of 15 cm to one meter. Line transects were established at each collection site to measure vegetation cover, collect soil samples, and estimate surface-soil stability. Dust-flux patterns were calculated on total sediment collected over the sampling period, normalized to the size of the sediment trap and number of days in a sampling period (reported as grams m-2 day-1). Dust flux peaked during the spring months in all plant-community types, likely due to higher surface wind speeds typical of this season. Pinyon-Juniper woodland, perennial grassland, Artemisia tridentata shrubland, Coleogyne ramosissima shrubland, and Atriplex spp. shrubland averaged 6, 6.4, 11.1, 101.4, 138.1 g m-2 d-1 respectively during the spring. Dust flux was lowest during the winter period when surface wind speeds are commonly low, and snow periodically covers the soil. Pinyon-Juniper woodland, perennial grassland, Artemisia

  20. Loess records

    USGS Publications Warehouse

    Muhs, Daniel R.; Cattle, Stephen R.; Crouvi, Onn; Rousseau, Denis-Didier; Sun, Jiimin; Zárate, Marcelo A.

    2014-01-01

    Loess is aeolian sediment, dominated by silt-sized particles, that is identifiable in the field as a distinct sedimentary body. It covers a significant portion of the land surface of the Earth and as such constitutes one of the most important archives of long-term dust deposition. Large tracts of loess cover Europe, Asia, South America, and North America, and smaller loess bodies are found covering parts of Africa, the Middle East, New Zealand, and Australia. Loess thickness, particle size, and carbonate content decrease downwind from sources, trends that are powerful tools for reconstructing paleowinds. Many loess sections consist of relatively thick deposits of mostly unaltered sediment with intercalated paleosols. Paleosols represent periods of landscape stability when loess deposition ceased or at least slowed significantly. Studies from several continents show that loess in most regions was deposited during glacial periods and paleosols formed during interglacial and interstadial periods.

  1. Impact of Lunar Dust on the Exploration Initiative

    NASA Technical Reports Server (NTRS)

    Stubbs, T. J.; Vondrak, R. R.; Farrell, W. M.

    2005-01-01

    From the Apollo era it is known that dust on the Moon can cause serious problems for exploration activities. Such problems include adhering to clothing and equipment, reducing external visibility on landings, and causing difficulty to breathing and vision within the spacecraft. An important step in dealing with dust-related problems is to understand how dust grains behave in the lunar environment. All astronauts who walked on the Moon reported difficulties with lunar dust. Eugene Cernan, commander of Apollo 17, stated that one of the most aggravating, restricting facets of lunar surface exploration is the dust and its adherence to everything no matter what kind of material, whether it be skin, suit material, metal, no matter what it be and it's restrictive friction-like action to everything it gets on. Dust has also been highlighted as a priority by the Mars Exploration Program Assessment Group (MEPAG): 1A. Characterize both aeolian dust and particulates that would be kicked up from the martian regolith by surface operations of a human mission with fidelity sufficient to establish credible engineering simulation labs and/or software codes on Earth. We shall briefly describe the properties of lunar dust and its impact on the Apollo astronauts, and then summarize three main problems areas for understanding its behavior: Dust Adhesion and Abrasion, Surface Electric Fields and Dust Transport. These issues are all inter-related and must be well understood in order to minimize the impact of dust on lunar surface exploration.

  2. Dust Detector

    NASA Technical Reports Server (NTRS)

    Kelley, M. C.

    2001-01-01

    We discuss a recent sounding rocket experiment which found charged dust in the Earth's tropical mesosphere. The dust detector was designed to measure small (5000 - 10000 amu.) charged dust particles, most likely of meteoric origin. A 5 km thick layer of positively charged dust was found at an altitude of 90 km, in the vicinity of an observed sporadic sodium layer and sporadic E layer. The observed dust was positively charged in the bulk of the dust layer, but was negatively charged near the bottom.

  3. Influence on the atmospheric general circulation caused by the direct effect which dust exerts on radiation process

    NASA Astrophysics Data System (ADS)

    Chiba, M.

    2004-12-01

    The total amount of the soil particle (Aeolian-dust) danced by the wind from the dryness area is called annual 1000-3000Tg on the whole earth. The thing from Sahara Desert in North Africa occupies more than the half of these. The small particle of particle diameter piles up into the atmosphere among the danced soil particles for a long period of time (being weight quantity around about 1%). The particle which piles up into the atmosphere has the work which is scattered about or absorbs solar radiation. On the other hand, aeolian dust has the work which performs absorption and discharge as black-body to infrared radiation, and serves as a substance which has greenhouse effect to an earth air system. We developed an general circulation model (MASINGAR) incorporating each model about the radiation process in consideration of the influence on the solar radiation by generating of aeolian dust, transportation, each self-possessed process, and dust, and infrared radiation. The numerical experiment about influence done to the atmospheric general circulation of aeolian dust using this was conducted.

  4. High-latitude dust in the Earth system

    NASA Astrophysics Data System (ADS)

    Bullard, Joanna E.; Baddock, Matthew; Bradwell, Tom; Crusius, John; Darlington, Eleanor; Gaiero, Diego; Gassó, Santiago; Gisladottir, Gudrun; Hodgkins, Richard; McCulloch, Robert; McKenna-Neuman, Cheryl; Mockford, Tom; Stewart, Helena; Thorsteinsson, Throstur

    2016-06-01

    Natural dust is often associated with hot, subtropical deserts, but significant dust events have been reported from cold, high latitudes. This review synthesizes current understanding of high-latitude (≥50°N and ≥40°S) dust source geography and dynamics and provides a prospectus for future research on the topic. Although the fundamental processes controlling aeolian dust emissions in high latitudes are essentially the same as in temperate regions, there are additional processes specific to or enhanced in cold regions. These include low temperatures, humidity, strong winds, permafrost and niveo-aeolian processes all of which can affect the efficiency of dust emission and distribution of sediments. Dust deposition at high latitudes can provide nutrients to the marine system, specifically by contributing iron to high-nutrient, low-chlorophyll oceans; it also affects ice albedo and melt rates. There have been no attempts to quantify systematically the expanse, characteristics, or dynamics of high-latitude dust sources. To address this, we identify and compare the main sources and drivers of dust emissions in the Northern (Alaska, Canada, Greenland, and Iceland) and Southern (Antarctica, New Zealand, and Patagonia) Hemispheres. The scarcity of year-round observations and limitations of satellite remote sensing data at high latitudes are discussed. It is estimated that under contemporary conditions high-latitude sources cover >500,000 km2 and contribute at least 80-100 Tg yr-1 of dust to the Earth system (~5% of the global dust budget); both are projected to increase under future climate change scenarios.

  5. Rare earth element and Nd isotope geochemistry of an ombrotrophic peat bog at Karukinka (Chile, 53.9° S): a palaeo-record of Holocene dust deposition in Tierra del Fuego.

    NASA Astrophysics Data System (ADS)

    Vanneste, Heleen; De Vleeschouwer, François; Vanderstraeten, Aubry; Mattielli, Nadine; Triquet, Delphine; Piotrowska, Natalia; Le Roux, Gael

    2013-04-01

    The value of ombrotrophic peat bogs as past atmospheric dust records, has been increasingly recognized over the past 10 years. Their high accumulation rates provide high resolution archives of natural atmospheric dust deposition since the Late Glacial, often missing in marine, lake and ice core records. Consequently, peat deposits can be used as a proxy for atmospheric circulation patterns and thus palaeoclimate. In the Southern Hemisphere, the climate is considered to be driven by the Southern Westerly Wind belt (SSW), as it significantly affects the Antarctic Circumpolar Current and hence atmospheric CO2 levels. Palaeo SSW belt migrations have been observed in palaeoclimate records but, reconstructions of SSW shifts and associated climatic changes are incoherent, in particular for the Holocene. As peatlands thrive in southwest Tierra del Fuego due to its high annual precipitation, a remote ombrotrophic peat bog at Karukinka (southwest on the Isla Grande de Tierra del Fuego) was sampled, to investigate the Holocene palaeoclimate in southern South America based on dust deposition records. A 4,5 m long Russian D-core was recovered and subsequently subsampled for elemental and isotope geochemistry in addition to density and radiocarbon dating measurements. Initial results show a number of layers enriched in scandium, indicating the presence of lithogenic material, i.e. dust. Rare earth element patterns indicate at least 2 different sources. The most significant dust peak occurs at the base of the core at ~7300 Cal years B.P and has a neodymium isotopic composition of 2.2, suggesting a volcanic origin.

  6. Cosmic iron, a new factor in podsolization in aeolian sandy deposits in NW-Europe (part 1, senior)

    NASA Astrophysics Data System (ADS)

    van Mourik, Jan; de Vet, Sebastiaan

    2013-04-01

    In Netherlands is podzolization is the dominant soil forming process in medium fine sand deposits as Late-glacial coversand and Holocene driftsand. The natural soil evolution in such deposits tended to cambic podzols in xeromorphic and gleyic podzols in hydromorphic field conditions. Historical land use accelerated the soil acidification and transferred the majority of the cambic podzols in carbic podzols. The natural free iron content of coversand and driftsand deposits is very low (< 0,05 %). Before deposition the sand grains survived a long history of weathering, fluvial, glacial and finally aeolian transport. Consequently, the mineral composition is dominated by Quartz and the fraction of hydrolysable minerals is very low. However, the presence of iron is very clear in the spodic B horizons of cambic and carbic podzols. Sometimes carbic podzols and acid gleyic podzols show placic properties, due to the formation of iron crusts. If a soil profile is affected by iron rich groundwater, originating from fluvial, glacial or periglacial sediments which a higher free iron content, (the situation in brook valleys and some depressions) the concentrations of iron are probably sufficient to explain the presence of iron cutans in the Bs horizon and iron-rich gleyic mottles in the Cg horizon of a podzolic soil. However, if a soil profile is not affected by iron-rich groundwater (the situation in coversand ridges) the iron concentrations of the sand deposits are insufficient to explain the iron cutans in the Bs horizon. After abolition of the plaggic agriculture around 1900 AD, extensive parts of the Calluna heath have been reforested with Scotch pine. The mormoder humus forms, developed under these Pine plantations, are excellent soil records of the last century. Soil micromorphological analyses of thin sections of mormoder profiles indicate the presence of olivinic and other heavy mineral and opaque particles that have not received much attention in studies. Their presence

  7. Holocene aeolian sediments on the NE Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Stauch, G.; Lehmkuhl, F.; Hilgers, A.; Zhao, H.

    2012-04-01

    The semiarid climate of the northeastern Tibetan Plateau supports the formation of different types of aeolian sediments and landforms during the Holocene. Aeolians silts and sands in the catchment of the Donggi Cona in an elevation above 4000m to 4800 m asl reflect variable climate conditions during that time as well as different sediment sources. Based on 51 OSL datings and catchment wide geomorphological mapping a complex pattern of long and short distance sediment transport has been reconstructed. Only few aeolian archives are preserved from the late Pleistocene in this mountain environment indicating cold and dry climate conditions which prevented a continuous accumulation. During the early Holocene a phase of increased aeolian sedimentation of sand at the slopes of the mountains has been reconstructed. The sand originated from a large alluvial fan which was highly active during the Pleistocene. In addition, a thin loess cover is preserved at a few sites in the neighboring mountains ranges. The sedimentation of the loess started around 2000 years later than the sedimentation of the sand at the foot slope. Both archives are related to an increase in precipitation at the northern margin of the Tibetan Plateau which was related to a strengthening of the Asian Monsoon during that time. The wetter climate conditions favored the development of a vegetation cover which leads to the trapping and fixation of the aeolian sediments. However, with a further strengthening of the Monsoon systems these archives subsequently eroded due to higher run off and accumulated as colluvial and fluvial deposits in the basins. These phase lasted until 6 ka. A second aeolian period started at around 3 ka with the formation new dunes in the basins. This period can be associated with dry and cold climate of the late Holocene supporting the reactivation of the sand in the area. This might be further enhanced by an increased human impact by grazing during the late Holocene and resulting

  8. Aeolian Coastal Landscapes in changes (a study from Tahkuna, Estonia)

    NASA Astrophysics Data System (ADS)

    Anderson, A.

    2012-04-01

    The openness of the coast to the winds and storm waves has an important part in changing aeolian coastal landscapes as well as anthropogenic factor. The aeolian coastal landscapes are probably the most dynamic areas. Occurrence of aeolian coastal landscapes in Estonia is limited. They consist of sandy beaches, sandy beach ridges and dunes. The coastal ecosystems are strongly affected by their topography, based on the character of deposits and moisture conditions. The majority of their ecosystems are quite close to the specific natural habitat. These ecosystems are represented in the list of the European Union Habitats (Natura 2000). In recent decades human influence has changed the landscape over time in different activities (recreation, trampling, off-road driving) and their intensities, which has led to destruction or degradation of various habitats. Previously coastal landscapes were used for forestry and pasture. Nowadays one of the most serious threats to open landscape is afforestation. This study examines the relationships between landscape components during last decades. Trying to find out how much aeolian coastal landscapes are influenced by natural processes or human activities. The results are based on cartographic analysis, fieldwork data. The method of landscape complex profile was used. The profiles show a cross-sections of landforms and interrelationships between landscape components, most frequently describing the relations between soils and vegetation. In each sample point the mechanical composition of sediments, vegetation cover and soil is determined. Results show that changes in landscapes are induced by their own development as well as changes in environmental factors and human activities. Larger changes are due to increase of coastal processes activity. These processes can be observed in sandy beaches, which are easily transformed by waves. Higher sea levels during storm surges are reaching older beach formation, causing erosion and creating

  9. Mineral dust deposition in Western Mediterranean basin

    NASA Astrophysics Data System (ADS)

    Vincent, Julie; Laurent, Benoit; Bergmatti, Gilles; Losno, Rémi; Bon Nguyen, Elisabeth; Chevaillier, Servanne; Roulet, Pierre; Sauvage, Stéphane; Coddeville, Patrice; Ouboulmane, Noura; Siour, Guillaume; Tovar Sanchez, Antonio; Massanet, Ana; Morales Baquero, Rafael; Di Sarra, Giogio; Sferlazzo, Damiano; Dulac, François; Fornier, Michel; Coursier, Cyril

    2014-05-01

    North African deserts are the world's largest sources of atmospheric mineral dust produced by aeolian erosion. Saharan dust is frequently transported toward Europe over the Mediterranean basin. When deposited in oceanic areas, mineral dust can constitute a key input of nutrients bioavailable for the oceanic biosphere. For instance, Saharan dust deposited in the in the Mediterranean Sea can be a significant source of nutrient like Fe, P and N during summer and autumn. Our objective is to study the deposition Saharan mineral dust in the western Mediterranean basin and to improve how deposition processes are parameterized in 3D regional models. To quantify the deposition flux of Saharan dust in the western Mediterranean region a specific collector (CARAGA) to sample automatically the insoluble atmospheric particle deposition was developed (LISA-ICARE) and a network of CARAGA collectors have been set up. Since 2011, eight CARAGA are then deployed in Frioul, Casset, Montandon and Ersa in France, Mallorca and Granada in Spain, Lampedusa in Italia, and Medenine in Tunisia, along a South-North gradient of almost 2000km from the North African coast to the South of Europe. We observe 10 well identified dust Saharan deposition events at Lampedusa and 6 at Mallorca for a 1-yr sampling period. These dust events are sporadic and the South-North gradient of deposition intensity and frequency is observed (the highest dust mass sampled at the stations are : 2,66 g.m-2 at Lampedusa ; 0,54 g.m-2 at Majorque ; 0,33 g.m-2 at Frioul ; 0,16 g.m-2 at Casset). The ability of the CHIMERE model to reproduce the deposition measurements is tested. The mineral dust plumes simulated over the western Mediterranean basin are also compared to satellite observations (OMI, MODIS) and in-situ measurements performed during the ChArMEx campaign and in the AERONET stations.

  10. Dust Storm

    Atmospheric Science Data Center

    2013-04-16

    article title:  Massive Dust Storm over Australia     View ... at JPL September 22, 2009 - Massive dust storm over Australia. project:  MISR category:  ... Sep 22, 2009 Images:  Dust Storm location:  Australia and New Zealand ...

  11. Analysis of topsoil aggregation with linkage to dust emission potential

    NASA Astrophysics Data System (ADS)

    Swet, Nitzan; Katra, Itzhak

    2015-04-01

    Dust emission by soil erosion has environmental and socioeconomic significances due to loss of a natural resource and air pollution. Topsoil resistance to erosion depends on its physicochemical properties, especially on the soil aggregation. Aggregate size distribution of soil samples is commonly used for the assessment of soil stability and fertility. It is suggested that aggregates larger than 840 µm in their effective diameter are stable to aeolian (wind) soil erosion. However the physicochemical properties of aggregates should be considered in determining the dust emission potential from soils. This study focuses on quantitative analyses of physical and chemical properties of aggregates in order to develop a soil stability index for dust emission. The study integrates laboratory analyses of soil samples and aeolian experiments of dust emission. Soil samples were taken from different land uses in a semi-arid loess soil that is subjected to aeolian erosion and dust emission. Laboratory tests include particle size distribution (PSD), soil organic carbon (SOC), inorganic carbon (CaCO3), water content (WC), and elemental composition by XRF technique. The size analysis shows significant differences in aggregation between natural-soil plots (N) and grazing-soil plots (G). The MWD index was higher in N (1204 µm) than that of G (400 µm). Basic aeolain experiments with a boundary layer wind tunnel showed dust emission of particulate matter (PM10) from both soils, although the concentrations were significantly lower in N plots. Aggregates at specific size fractions are characterized by different content of cementing agents. The content of fine particles (< 20 µm) and SOM were higher in macro-aggregates (500-2000 µm), while the CaCO3 content was higher in aggregate fraction of 63-250 µm. WC values were highest in micro-aggregates (< 63 µm). However the lowest content of these cementing agents were mostly found in the aggregate size fraction of 1000 µm. Differences

  12. Should precipitation influence dust emission in global dust models?

    NASA Astrophysics Data System (ADS)

    Okin, Gregory

    2016-04-01

    Soil moisture modulates the threshold shear stress required to initiate aeolian transport and dust emission. Most of the theoretical and laboratory work that has confirmed the impact of soil moisture has appropriately acknowledged that it is the soil moisture of a surface layer a few grain diameters thick that truly controls threshold shear velocity. Global and regional models of dust emission include the effect of soil moisture on transport threshold, but most ignore the fact that only the moisture of the very topmost "active layer" matters. The soil moisture in the active layer can differ greatly from that integrated through the top 2, 5, 10, or 100 cm (surface layers used by various global models) because the top 2 mm of heavy texture soils dries within ~1/2 day while sandy soils dry within less than 2 hours. Thus, in drylands where dust emission occurs, it is likely that this top layer is drier than the underlying soil in the days and weeks after rain. This paper explores, globally, the time between rain events in relation to the time for the active layer to dry and the timing of high wind events. This analysis is carried out using the same coarse reanalyses used in global dust models and is intended to inform the soil moisture controls in these models. The results of this analysis indicate that the timing between events is, in almost all dust-producing areas, significantly longer than the drying time of the active layer, even when considering soil texture differences. Further, the analysis shows that the probability of a high wind event during the period after a rain where the surface is wet is small. Therefore, in coarse global models, there is little reason to include rain-derived soil moisture in the modeling scheme.

  13. A note on the stochastic nature of particle cohesive force and implications to threshold friction velocity for aerodynamic dust entrainment

    NASA Astrophysics Data System (ADS)

    Shao, Yaping; Klose, Martina

    2016-09-01

    There is considerable interest to determine the threshold for aeolian dust emission on Earth and Mars. Existing schemes for threshold friction velocity are all deterministic in nature, but observations show that in the dust particle size range the threshold friction velocity scatters strongly due to stochastic inter-particle cohesion. In the real world, there always exists a certain amount of free dust which can be easily lifted from the surface by weak winds or even turbulence, as exemplified by dust devils. It has been proposed in the dust-devil research community, that the pressure drop at dust-devil center may be a major mechanism for dust-devil dust emission, known as the Δp effect. It is questioned here whether the Δp effect is substantial or whether the elevated dust concentration in dust devils is due to free dust emission. A simple analysis indicates that the Δp effect appears to be small and the dust in dust devils is probably due to free dust emission and dust convergence. To estimate free dust emission, it is useful to define a lower limit of dust-particle threshold friction velocity. A simple expression for this velocity is proposed by making assumptions to the median and variance of inter-particle cohesive force. The simple expression is fitted to the data of the Arizona State University Vortex Generator. While considerable uncertainty remains in the scheme, this note highlights the need for additional research on the stochastic nature of dust emission.

  14. The National Wind Erosion Research Network: Building a standardized long-term data resource for aeolian research, modeling and land management

    NASA Astrophysics Data System (ADS)

    Webb, Nicholas P.; Herrick, Jeffrey E.; Van Zee, Justin W.; Courtright, Ericha M.; Hugenholtz, Christopher H.; Zobeck, Ted M.; Okin, Gregory S.; Barchyn, Thomas E.; Billings, Benjamin J.; Boyd, Robert; Clingan, Scott D.; Cooper, Brad F.; Duniway, Michael C.; Derner, Justin D.; Fox, Fred A.; Havstad, Kris M.; Heilman, Philip; LaPlante, Valerie; Ludwig, Noel A.; Metz, Loretta J.; Nearing, Mark A.; Norfleet, M. Lee; Pierson, Frederick B.; Sanderson, Matt A.; Sharratt, Brenton S.; Steiner, Jean L.; Tatarko, John; Tedela, Negussie H.; Toledo, David; Unnasch, Robert S.; Van Pelt, R. Scott; Wagner, Larry

    2016-09-01

    The National Wind Erosion Research Network was established in 2014 as a collaborative effort led by the United States Department of Agriculture's Agricultural Research Service and Natural Resources Conservation Service, and the United States Department of the Interior's Bureau of Land Management, to address the need for a long-term research program to meet critical challenges in wind erosion research and management in the United States. The Network has three aims: (1) provide data to support understanding of basic aeolian processes across land use types, land cover types, and management practices, (2) support development and application of models to assess wind erosion and dust emission and their impacts on human and environmental systems, and (3) encourage collaboration among the aeolian research community and resource managers for the transfer of wind erosion technologies. The Network currently consists of thirteen intensively instrumented sites providing measurements of aeolian sediment transport rates, meteorological conditions, and soil and vegetation properties that influence wind erosion. Network sites are located across rangelands, croplands, and deserts of the western US.

  15. Building of tropical beach ridges, northeastern Queensland, Australia: Cyclone inundation and aeolian decoration

    NASA Astrophysics Data System (ADS)

    Tamura, Toru; Nicholas, William; Brooke, Brendan; Oliver, Thomas

    2016-04-01

    Processes associated with tropical cyclones are thought responsible for building coarse sand beach ridges along the northeastern Queensland coast, Australia. While these ridges are expected to be geological records of the past cyclone, they question the general consensus of the aeolian genesis of sandy beach ridges. To explore the ridge-forming process, we carried out the GPR survey, auger drilling, pit excavation, grain-size analysis, and OSL dating for coarse sand beach ridges at the Cowley Beach, northeastern Queensland. The Cowley Beach is a mesotidal beach characterized by a low-tide terrace and steep beach face. Ten beach ridges are recognized along the survey transect that extends 700 m inland from the shore. 37 OSL ages are younger seawards, indicating the seaward accretion of the ridge sequence over the last 2700 years. The highest ridge is +5.1 m high above AHD (Australian Height Datum). Two GPR units are bounded by a groundwater surface at c. +1.5 m AHD. The upper unit is characterized by horizontal to hummocky reflectors punctuated by seaward dipping truncation surfaces. These reflectors in places form dome-like structure that appears to be the nucleus of a beach ridge. The shape and level (+2.5 m AHD) of the dome are similar to those of the present swash berm. The lower unit shows a sequence of reflectors that dip at an angle of present beach face. The sequence is dissected by truncation surfaces, some of which are continuous to those in the upper unit. Coarse sand mainly forms beach ridge deposits below +4.0 m AHD, while a few higher ridges have an upward fining layer composed of medium sand above +4.0 m, which is finer than aeolian ripples found on the backshore during the survey. In addition, pumice gravel horizons underlie the examined ridge crests. The sequence of seaward dipping reflectors indicates that the Cowley Beach, like other many sandy beaches, has prograded during onshore sand accretion by fairweather waves and has been eroded by storms

  16. Calibration of the MDCO dust collector and of four versions of the inverted frisbee dust deposition sampler

    NASA Astrophysics Data System (ADS)

    Sow, Mamadou; Goossens, Dirk; Rajot, Jean Louis

    2006-12-01

    Wind tunnel experiments were conducted to determine the efficiency of sediment samplers designed to measure the deposition of aeolian dust. Efficiency was ascertained relative to a water surface, which was considered the best alternative for simulating a perfectly absorbent surface. Two types of samplers were studied: the Marble Dust Collector (MDCO) and the inverted frisbee sampler. Four versions of the latter catcher were tested: an empty frisbee, an empty frisbee surrounded by an aerodynamic flow deflector ring, a frisbee filled with glass marbles, and a frisbee filled with glass marbles and surrounded by a flow deflector ring. Efficiency was ascertained for five wind velocities (range: 1-5 m s - 1 ) and eight grain size classes (range: 10-89 μm). The efficiency of dust deposition catchers diminishes rapidly as the wind speed increases. It also diminishes as the particles caught become coarser. Adding a flow deflector ring to a catcher substantially improves the catcher's efficiency, by up to 100% in some cases. The addition of glass marbles to a catcher, on the other hand, does not seem to increase the efficiency, at least not at wind velocities inferior to the deflation threshold. For higher velocities the marbles protect the settled particles from resuspension, keeping them in the catcher. The following five parameters determine the accumulation of aeolian dust in a catcher: the horizontal dust flux, the weight of the particles, atmospheric turbulence, resuspension, and the dust shadow effect created by the catcher. The final accumulation flux depends on the combination of these parameters. The catchers tested in this study belong to the best catchers currently in use in earth science and have been the subject of various aerodynamic studies to improve their efficiency. Nevertheless the catching efficiency remains low, in the order of 20-40% for wind speeds above 2 m s - 1 . Other catchers suffer from the same low efficiencies. There is, thus, evidence to

  17. Soil Response to Aeolian Disturbance in West Greenland

    NASA Astrophysics Data System (ADS)

    Heindel, R. C.; Culler, L. E.; Chipman, J. W.; Virginia, R. A.

    2015-12-01

    Arctic soils are a critical ecological resource, yet are increasingly vulnerable to global change. In the Kangerlussuaq region of West Greenland, aeolian disturbance is the greatest threat to soil stability, with strong katabatic winds eroding vegetation and soil down to the underlying glacial till or bedrock. Little is known about what controls the distribution and rate of the aeolian erosion, which initially results in a state change from tundra to a deflated and nearly unvegetated ground. It is unclear if vegetation can eventually reestablish after erosion occurs, potentially aided by the biological soil crust (BSC) that develops within the eroded areas, or if this soil loss is an irreversible change in vegetation and soil carbon (C) and nitrogen (N) cycling. Our analysis of high-resolution satellite imagery shows that across the entire study region, deflated ground covers 22% of the terrestrial landscape. Aeolian erosion occurs more frequently closer to the Greenland Ice Sheet and on S-facing slopes. Using lichenometry, we estimate that erosional fronts move across the landscape at rates of 2.5 cm yr-1, leaving unproductive ground in their wake. The onset of widespread aeolian erosion occurred roughly 700-1000 years ago, pointing toward regional cooling and aridity as the drivers behind erosion. Finally, we consider whether the BSCs can improve soil quality enough to allow for full vegetation regrowth. Preliminary results show that while the BSCs fix atmospheric N and increase C storage, the rate of soil quality recovery is extremely slow. Understanding the thresholds between vegetated tundra and eroded ground is critical for predicting how the Kangerlussuaq landscape will respond to anticipated changes in climate and ice sheet dynamics.

  18. Model for surface packing and aeolian transport on sand ripples

    NASA Astrophysics Data System (ADS)

    Louge, M. Y.; Valance, A.; el-Moctar, A. Ould; Ahmedou, D. Ould; Dupont, P.

    2009-06-01

    Measurements indicate that the solid volume fraction on a sand ripple varies from random jammed packing at troughs to the minimum stable packing at crests. By relating variations of the solid volume fraction to those of the surface turbulent shear stress, a collisional model of reptation suggests a qualitative origin for these observations. Although the model overestimates the critical shear velocity at which reptation arises, it predicts the rate of aeolian transport on Earth and Mars.

  19. The potential scale of aeolian structures on Venus

    NASA Technical Reports Server (NTRS)

    Marshall, J. R.; Greeley, Ronald

    1991-01-01

    Simulations of the Venusian aeolian environment with the Venus Wind Tunnel have shown that microdunes are formed during the entrainment of sand-sized material. These structures are several tens of centimeters long (2-3 cm high) and combine the morphological and behavioral characteristics of both full-scale terrestrial dunes and current ripples formed in subaqueous environments. Their similarity to both reflects the fact that the Venusian atmosphere has a density intermediate between air and water. Although the development of microdunes in the wind tunnel experiments was limited by tunnel dimensions, it is possible to make some predictions about their potential size on Venus, and the potential size of related aeolian structures. Microdunes are fluid-filled structures (as are dunes and current ripples) and as such have no theoretical upper limit to their size from a fluid dynamics viewpoint. Limitations to size observed in subaqueous structures are set by, for example, water depth; limitations to the size of dunes are set by, for example, sand supply. It is therefore reasonable to suppose that the microdunes on Venus could evolve into much larger features than those observed in experiments. In addition, the researchers note that current ripples (which are closely related to microdunes) are often found in association with giant ripples that have dimensions similar to aeolian dunes. Thus, it may be reasonable to assume that analogous large scale structures occur on Venus. Both (terrestrial) aeolian and subaqueous environments generate structures in excess of one hundred meters in wavelength. Such dimensions may therefore be applicable to Venusian bedforms. Analysis of Magellan data may resolve the issue.

  20. Quantifying the provenance of aeolian sediments using multiple composite fingerprints

    NASA Astrophysics Data System (ADS)

    Liu, Benli; Niu, Qinghe; Qu, Jianjun; Zu, Ruiping

    2016-09-01

    We introduce a new fingerprinting method that uses multiple composite fingerprints for studies of aeolian sediment provenance. We used this method to quantify the provenance of sediments on both sides of the Qinghai-Tibetan Railway (QTR) in the Cuona Lake section of the Tibetan Plateau (TP), in an environment characterized by aeolian and fluvial interactions. The method involves repeatedly solving a linear mixing model based on mass conservation; the model is not limited to spatial scale or transport types and uses all the tracer groups that passed the range check, Kruskal-Wallis H-test, and a strict analytical solution screening. The proportional estimates that result from using different composite fingerprints are highly variable; however, the average of these fingerprints has a greater accuracy and certainty than any single fingerprint. The results show that sand from the lake beach, hilly surface, and gullies contribute, respectively, 48%, 31% and 21% to the western railway sediments and 43%, 33% and 24% to the eastern railway sediments. The difference between contributions from various sources on either side of the railway, which may increase in the future, was clearly related to variations in local transport characteristics, a conclusion that is supported by grain size analysis. The construction of the QTR changed the local cycling of materials, and the difference in provenance between the sediments that are separated by the railway reflects the changed sedimentary conditions on either side of the railway. The effectiveness of this method suggests that it will be useful in other studies of aeolian sediments.

  1. Characterizing the instability of aeolian environments using analytical reasoning

    NASA Astrophysics Data System (ADS)

    Houser, C.; Bishop, M. P.; Dobreva, I. D.; Barrineau, C. P.; Weymer, B. A.

    2013-12-01

    Characterization of aeolian systems is complicated by rapidly changing surface-process regimes, spatio-temporal scale dependencies, and subjective interpretation of imagery and spatial data. Stability and instability of the South Texas sand sheet is addressed using an artificial intelligence approach that integrates spatial information and analytical reasoning. Specifically, the purpose of this study is to determine if landscape evolutionary sequences could be mapped and characterized based on simple conceptual relationships amongst biophysical variables including topography, vegetation, surface moisture, wind speed, and surface erosion and deposition. A digital elevation model was derived from airborne LiDAR data and combined with moisture and vegetation indices computed using Spectral feature extraction from Landsat Thematic Mapper data. Our analysis reveals unique scale dependent spatial patterns and the use of fuzzy cognitive maps provides an analytical reasoning approach to address the complexity of aeolian environments in response to changes in climate forcing. The application to other Holocene aeolian deposits and the potential for this approach to model landscape evolution are also discussed.

  2. Substantial dust loss of bioavailable phosphorus from agricultural soils

    PubMed Central

    Katra, Itzhak; Gross, Avner; Swet, Nitzan; Tanner, Smadar; Krasnov, Helena; Angert, Alon

    2016-01-01

    Phosphorus (P) is an essential element in terrestrial ecosystems. Knowledge on the role of dust in the biogeochemical cycling of phosphorus is very limited with no quantitative information on aeolian (by wind) P fluxes from soils. The aim of this study is to focus on P cycling via dust emissions under common land-use practices in an arid environment by integration of sample analyses and aeolian experiments. The experiments indicate significant P fluxes by PM10 dust due to agricultural land use. Even in a single wind-dust event at moderate velocity (7.0 m s−1), P flux in conventional agricultural fields can reach 1.83 kg km−2, that accumulates to a considerable amount per year at a regional scale. The results highlight a negative yearly balance in P content (up to hundreds kg km−2) in all agricultural soils, and thus more P nutrition is required to maintain efficient yield production. In grazing areas where no P nutrition is applied, the soil degradation process can lead to desertification. Emission of P from soil dust sources has significant implications for soil nutrient resources and management strategies in agricultural regions as well as for loading to the atmosphere and global biogeochemical cycles. PMID:27095629

  3. Substantial dust loss of bioavailable phosphorus from agricultural soils

    NASA Astrophysics Data System (ADS)

    Katra, Itzhak; Gross, Avner; Swet, Nitzan; Tanner, Smadar; Krasnov, Helena; Angert, Alon

    2016-04-01

    Phosphorus (P) is an essential element in terrestrial ecosystems. Knowledge on the role of dust in the biogeochemical cycling of phosphorus is very limited with no quantitative information on aeolian (by wind) P fluxes from soils. The aim of this study is to focus on P cycling via dust emissions under common land-use practices in an arid environment by integration of sample analyses and aeolian experiments. The experiments indicate significant P fluxes by PM10 dust due to agricultural land use. Even in a single wind-dust event at moderate velocity (7.0 m s‑1), P flux in conventional agricultural fields can reach 1.83 kg km‑2, that accumulates to a considerable amount per year at a regional scale. The results highlight a negative yearly balance in P content (up to hundreds kg km‑2) in all agricultural soils, and thus more P nutrition is required to maintain efficient yield production. In grazing areas where no P nutrition is applied, the soil degradation process can lead to desertification. Emission of P from soil dust sources has significant implications for soil nutrient resources and management strategies in agricultural regions as well as for loading to the atmosphere and global biogeochemical cycles.

  4. Optically stimulated luminescence dating of aeolian sand in the otindag dune field and holocene climate change

    USGS Publications Warehouse

    Zhou, Y.L.; Lu, H.Y.; Mason, J.; Miao, X.D.; Swinehart, J.; Goble, R.

    2008-01-01

    The dune system in Otindag sand field of northern China is sensitive to climate change, where effective moisture and related vegetation cover play a controlling role for dune activity and stability. Therefore, aeolian deposits may be an archive of past environmental changes, possibly at the millennial scale, but previous studies on this topic have rarely been reported. In this study, thirty-five optically stimulated luminescence (OSL) ages of ten representative sand-paleosol profiles in Otindag sand field are obtained, and these ages provide a relatively complete and well-dated chronology for wet and dry variations in Holocene. The results indicate that widespread dune mobilization occurred from 9.9 to 8.2 ka, suggesting a dry early Holocene climate. The dunes were mainly stabilized between 8.0 and 2.7 ka, implying a relatively wet climate, although there were short-term penetrations of dune activity during this wet period. After ???2.3 ka, the region became dry again, as inferred from widespread dune activity. The "8.2 ka" cold event and the Little Ice Age climatic deterioration are detected on the basis of the dune records and OSL ages. During the Medieval Warm Period and the Sui-Tang Warm Period (570-770 AD), climate in Otindag sand field was relatively humid and the vegetation was denser, and the sand dunes were stabilized again. These aeolian records may indicate climate changes at millennial time scale during Holocene, and these climatic changes may be the teleconnection to the climate changes elsewhere in the world. ?? Science in China Press and Springer-Verlag GmbH 2008.

  5. Aeolian Induced Erosion and Particle Entrainment

    NASA Technical Reports Server (NTRS)

    Saint, Brandon

    2007-01-01

    The Granular Physics Department at The Kennedy Space Center is addressing the problem of erosion on the lunar surface. The early stages of research required an instrument that would produce erosion at a specific rate with a specific sample variation. This paper focuses on the development and experimental procedures to measure and record erosion rates. This was done with the construction of an open air wind tunnel, and examining the relationship between airflow and particle motion.

  6. Coeval dust accumulation minima in Greenland and East Central Europe over 31-23 ka

    NASA Astrophysics Data System (ADS)

    Újvári, Gábor; Stevens, Thomas; Varga, György; Kovács, János; Molnár, Mihály

    2016-04-01

    , together with the bulk loess median grain size (D50bulk) that is considered an integrated proxy of wind strength, dust source distance, aridity and vegetation cover. While an increase of dust flux and D50bulk with time is apparent, such a trend cannot be seen in the quartz grain size measures (D50quartz). This observation may imply that wind speeds were relatively constant in the studied time interval, while the turbulence of the flow may have been extremely varying (i.e. strong/rapid changes in the frequency/magnitude of dust storm events). A striking feature of the MAR record is that accumulation minima in the Dunaszekcsö record are synchronous with the Greenland Interstadials (GI-5.1 to GI-3). Subsequent Ca2+ minima in the NGRIP record at 26.22 and 25.02 ka (b2k) are also coeval with the MAR minima in the studied loess sequence. At the same time, these patterns are barely visible in the bulk and quartz grain size records. We speculate that the synchronous changes in the NGRIP Ca2+ and the Dunaszekcsö MAR records are results of millennial scale variations in the activity of Northern Hemisphere dust emitting regions shown in two archives from different environments. The very similar timing of MAR minima (and also some of the maxima) suggest a rapid aeolian system response in East Central Europe to abrupt climatic changes in the North Atlantic. Although such a synchronicity does not prove a Central European dust source to Greenland, it is consistent with this possibility. This study was supported by the OTKA PD-108639 grant and the Bolyai János Research Fellowship (both to GÚ). [1] Dansgaard, W., et al. (1993). Evidence for general instability of past climate from a 250-kyr ice-core record. Nature 364, 218-220. [2] Johnsen, S.J., et al. (1992). Irregular glacial interstadials recorded in a new Greenland ice core. Nature 359, 311-313. [3] Rasmussen, S.O., et al. (2014). A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three

  7. Coeval dust accumulation minima in Greenland and East Central Europe over 31-23 ka

    NASA Astrophysics Data System (ADS)

    Újvári, Gábor; Stevens, Thomas; Varga, György; Kovács, János; Molnár, Mihály

    2016-04-01

    with the bulk loess median grain size (D50bulk) that is considered an integrated proxy of wind strength, dust source distance, aridity and vegetation cover. While an increase of dust flux and D50bulk with time is apparent, such a trend cannot be seen in the quartz grain size measures (D50quartz). This observation may imply that wind speeds were relatively constant in the studied time interval, while the turbulence of the flow may have been extremely varying (i.e. strong/rapid changes in the frequency/magnitude of dust storm events). A striking feature of the MAR record is that accumulation minima in the Dunaszekcsö record are synchronous with the Greenland Interstadials (GI-5.1 to GI-3). Subsequent Ca2+ minima in the NGRIP record at 26.22 and 25.02 ka (b2k) are also coeval with the MAR minima in the studied loess sequence. At the same time, these patterns are barely visible in the bulk and quartz grain size records. We speculate that the synchronous changes in the NGRIP Ca2+ and the Dunaszekcsö MAR records are results of millennial scale variations in the activity of Northern Hemisphere dust emitting regions shown in two archives from different environments. The very similar timing of MAR minima (and also some of the maxima) suggest a rapid aeolian system response in East Central Europe to abrupt climatic changes in the North Atlantic. Although such a synchronicity does not prove a Central European dust source to Greenland, it is consistent with this possibility. This study was supported by the OTKA PD-108639 grant and the Bolyai János Research Fellowship (both to GÚ). [1] Dansgaard, W., et al. (1993). Evidence for general instability of past climate from a 250-kyr ice-core record. Nature 364, 218-220. [2] Johnsen, S.J., et al. (1992). Irregular glacial interstadials recorded in a new Greenland ice core. Nature 359, 311-313. [3] Rasmussen, S.O., et al. (2014). A stratigraphic framework for abrupt climatic changes during the Last Glacial period based on three

  8. The National Wind Erosion Research Network: Building a standardized long-term data resource for aeolian research, modeling and land management

    USGS Publications Warehouse

    Webb, Nicholas P.; Herrick, Jeffrey E.; Van Zee, Justin W; Courtright, Ericha M; Hugenholtz, Ted M; Zobeck, Ted M; Okin, Gregory S.; Barchyn, Thomas E; Billings, Benjamin J; Boyd, Robert A.; Clingan, Scott D; Cooper, Brad F; Duniway, Michael C.; Derner, Justin D; Fox, Fred A; Havstad, Kris M.; Heilman, Philip; LaPlante, Valerie; Ludwig, Noel A; Metz, Loretta J; Nearing, Mark A; Norfleet, M Lee; Pierson, Frederick B; Sanderson, Matt A; Sharrat, Brenton S; Steiner, Jean L; Tatarko, John; Tedela, Negussie H; Todelo, David; Unnasch, Robert S; Van Pelt, R Scott; Wagner, Larry

    2016-01-01

    The National Wind Erosion Research Network was established in 2014 as a collaborative effort led by the United States Department of Agriculture’s Agricultural Research Service and Natural Resources Conservation Service, and the United States Department of the Interior’s Bureau of Land Management, to address the need for a long-term research program to meet critical challenges in wind erosion research and management in the United States. The Network has three aims: (1) provide data to support understanding of basic aeolian processes across land use types, land cover types, and management practices, (2) support development and application of models to assess wind erosion and dust emission and their impacts on human and environmental systems, and (3) encourage collaboration among the aeolian research community and resource managers for the transfer of wind erosion technologies. The Network currently consists of thirteen intensively instrumented sites providing measurements of aeolian sediment transport rates, meteorological conditions, and soil and vegetation properties that influence wind erosion. Network sites are located across rangelands, croplands, and deserts of the western US. In support of Network activities, http://winderosionnetwork.org was developed as a portal for information about the Network, providing site descriptions, measurement protocols, and data visualization tools to facilitate collaboration with scientists and managers interested in the Network and accessing Network products. The Network provides a mechanism for engaging national and international partners in a wind erosion research program that addresses the need for improved understanding and prediction of aeolian processes across complex and diverse land use types and management practices.

  9. Effects of river regulation on aeolian landscapes, Colorado River, southwestern USA

    USGS Publications Warehouse

    Draut, Amy E.

    2012-01-01

    Connectivity between fluvial and aeolian sedimentary systems plays an important role in the physical and biological environment of dryland regions. This study examines the coupling between fluvial sand deposits and aeolian dune fields in bedrock canyons of the arid to semiarid Colorado River corridor, southwestern USA. By quantifying significant differences between aeolian landscapes with and without modern fluvial sediment sources, this work demonstrates for the first time that the flow- and sediment-limiting effects of dam operations affect sedimentary processes and ecosystems in aeolian landscapes above the fluvial high water line. Dune fields decoupled from fluvial sand supply have more ground cover (biologic crust and vegetation) and less aeolian sand transport than do dune fields that remain coupled to modern fluvial sand supply. The proportion of active aeolian sand area also is substantially lower in a heavily regulated river reach (Marble–Grand Canyon, Arizona) than in a much less regulated reach with otherwise similar environmental conditions (Cataract Canyon, Utah). The interconnections shown here among river flow and sediment, aeolian sand transport, and biologic communities in aeolian dunes demonstrate a newly recognized means by which anthropogenic influence alters dryland environments. Because fluvial–aeolian coupling is common globally, it is likely that similar sediment-transport connectivity and interaction with upland ecosystems are important in other dryland regions to a greater degree than has been recognized previously.

  10. Effects of river regulation on aeolian landscapes, Colorado River, southwestern USA

    NASA Astrophysics Data System (ADS)

    Draut, Amy E.

    2012-06-01

    Connectivity between fluvial and aeolian sedimentary systems plays an important role in the physical and biological environment of dryland regions. This study examines the coupling between fluvial sand deposits and aeolian dune fields in bedrock canyons of the arid to semiarid Colorado River corridor, southwestern USA. By quantifying significant differences between aeolian landscapes with and without modern fluvial sediment sources, this work demonstrates for the first time that the flow- and sediment-limiting effects of dam operations affect sedimentary processes and ecosystems in aeolian landscapes above the fluvial high water line. Dune fields decoupled from fluvial sand supply have more ground cover (biologic crust and vegetation) and less aeolian sand transport than do dune fields that remain coupled to modern fluvial sand supply. The proportion of active aeolian sand area also is substantially lower in a heavily regulated river reach (Marble-Grand Canyon, Arizona) than in a much less regulated reach with otherwise similar environmental conditions (Cataract Canyon, Utah). The interconnections shown here among river flow and sediment, aeolian sand transport, and biologic communities in aeolian dunes demonstrate a newly recognized means by which anthropogenic influence alters dryland environments. Because fluvial-aeolian coupling is common globally, it is likely that similar sediment-transport connectivity and interaction with upland ecosystems are important in other dryland regions to a greater degree than has been recognized previously.

  11. Preservation of hanging aeolian deposits in insular karst depressions: Sediment sources and implications for the Pleistocene palaeogeography of the SE Adriatic archipelago

    NASA Astrophysics Data System (ADS)

    Babić, Ljubomir; Zupanič, Jožica; Vidović, Jelena; Razum, Ivan; Lužar-Oberiter, Borna; Crnjaković, Marta

    2013-12-01

    This study examines how and why the accumulation and preservation of aeolian sands are influenced by the character of karstic basement landforms. The studied examples are Late Pleistocene aeolian sands and underlying karstified carbonates of Southeastern Adriatic islands. To address this issue the spacial relationship between karstified bedrock and aeolian cover, aeolian and associated fluvial facies, as well as the petrography of sands, including heavy minerals and bioclasts (especially foraminifera) have been studied. Specific landforms of the carbonate basement originated as a consequence of deformation, karstification and locally with additional influence of fluvial processes. They are located at different elevations above today’s sea-level, as well as above ancient sand pathways towards the islands, which are now below sea-level. The karst depressions critically influenced the accumulation and preservation of aeolian sands. The depressions represented traps for accumulation and shelters for preservation of these sands. The closed type karst depressions include large examples which contain successions displaying the most complete stratigraphic record, located in the approximate centre of the depression. The open type karst depression is characterised by a partial removal of sands which were exported down-valley. The complex arrangement of the islands and closely located mainland coasts governed the location of primary sand transport paths. They included both aeolian and marine transport depending on the extent of exposed land versus submerged areas related to sea-level fluctuation. Marine settings along the sand pathways included shallow, sandy sea bottoms partly covered by sea-grass, as well as sand beaches and restricted environments. From low inter-island areas which hosted the primary sand pathways, the sands were uplifted and deposited over the islands by wind action thus producing hanging aeolian accumulations. The most influential Pleistocene winds

  12. Monte Carlo path sampling approach to modeling aeolian sediment transport

    NASA Astrophysics Data System (ADS)

    Hardin, E. J.; Mitasova, H.; Mitas, L.

    2011-12-01

    Coastal communities and vital infrastructure are subject to coastal hazards including storm surge and hurricanes. Coastal dunes offer protection by acting as natural barriers from waves and storm surge. During storms, these landforms and their protective function can erode; however, they can also erode even in the absence of storms due to daily wind and waves. Costly and often controversial beach nourishment and coastal construction projects are common erosion mitigation practices. With a more complete understanding of coastal morphology, the efficacy and consequences of anthropogenic activities could be better predicted. Currently, the research on coastal landscape evolution is focused on waves and storm surge, while only limited effort is devoted to understanding aeolian forces. Aeolian transport occurs when the wind supplies a shear stress that exceeds a critical value, consequently ejecting sand grains into the air. If the grains are too heavy to be suspended, they fall back to the grain bed where the collision ejects more grains. This is called saltation and is the salient process by which sand mass is transported. The shear stress required to dislodge grains is related to turbulent air speed. Subsequently, as sand mass is injected into the air, the wind loses speed along with its ability to eject more grains. In this way, the flux of saltating grains is itself influenced by the flux of saltating grains and aeolian transport becomes nonlinear. Aeolian sediment transport is difficult to study experimentally for reasons arising from the orders of magnitude difference between grain size and dune size. It is difficult to study theoretically because aeolian transport is highly nonlinear especially over complex landscapes. Current computational approaches have limitations as well; single grain models are mathematically simple but are computationally intractable even with modern computing power whereas cellular automota-based approaches are computationally efficient

  13. Abrupt climate variability since the last deglaciation based on a high-resolution, multi-proxy peat record from NW Iran: The hand that rocked the Cradle of Civilization?

    NASA Astrophysics Data System (ADS)

    Sharifi, Arash; Pourmand, Ali; Canuel, Elizabeth A.; Ferer-Tyler, Erin; Peterson, Larry C.; Aichner, Bernhard; Feakins, Sarah J.; Daryaee, Touraj; Djamali, Morteza; Beni, Abdolmajid Naderi; Lahijani, Hamid A. K.; Swart, Peter K.

    2015-09-01

    We present a high-resolution (sub-decadal to centennial), multi-proxy reconstruction of aeolian input and changes in palaeohydrological conditions based on a 13000 Yr record from Neor Lake's peripheral peat in NW Iran. Variations in relative abundances of refractory (Al, Zr, Ti, and Si), redox sensitive (Fe) and mobile (K and Rb) elements, total organic carbon (TOC), δ13CTOC, compound-specific leaf wax hydrogen isotopes (δD), carbon accumulation rates and dust fluxes presented here fill a large gap in the existing terrestrial paleoclimate records from the interior of West Asia. Our results suggest that a transition occurred from dry and dusty conditions during the Younger Dryas (YD) to a relatively wetter period with higher carbon accumulation rates and low aeolian input during the early Holocene (9000-6000 Yr BP). This period was followed by relatively drier and dustier conditions during middle to late Holocene, which is consistent with orbital changes in insolation that affected much of the northern hemisphere. Numerous episodes of high aeolian input spanning a few decades to millennia are prevalent during the middle to late Holocene. Wavelet analysis of variations in Ti abundances as a proxy for aeolian input revealed notable periodicities at 230, 320, and 470 years with significant periodicities centered around 820, 1550, and 3110 years over the last 13000 years. Comparison with palaeoclimate archives from West Asia, the North Atlantic and African lakes point to a teleconnection between North Atlantic climate and the interior of West Asia during the last glacial termination and the Holocene epoch. We further assess the potential role of abrupt climate change on early human societies by comparing our record of palaeoclimate variability with historical, geological and archaeological archives from this region. The terrestrial record from this study confirms previous evidence from marine sediments of the Arabian Sea that suggested climate change influenced the

  14. Late Quaternary environmental changes in the Taklamakan Desert, western China, inferred from OSL-dated lacustrine and aeolian deposits

    NASA Astrophysics Data System (ADS)

    Yang, Xiaoping; Preusser, Frank; Radtke, Ulrich

    2006-05-01

    Sediment records from the Tarim Basin of western China are of great importance for understanding Late Quaternary climatic variability in Central Asia. A chronology of aeolian and lacustrine deposits from the centre and southern margin of the Taklamakan Desert, central Tarim Basin, has been established using optical dating methods. Distinct variations in humidity during the last 40,000 a in this extremely arid inland basin have been identified. Lacustrine sediments were deposited in the centre of the Taklamakan during two periods of wetter than present day conditions at around 2000 and 30,000 a ago. Another humid period is recorded between 40,000 and 30,000 a ago. Aeolian processes, the development of large migrating dune fields dominated during periods of more arid conditions. Sand wedges at the southern margin of the Taklamakan are dated at ca 40,000 a and ca 18,000 a, and imply a significant temperature decrease in that area. Sedimentological evidence for a late Holocene humid period are consistent with records in ancient Chinese literature. Wetter environmental conditions in the past within the Taklamakan, as indicated by the presence of lacustrine deposits, are also supported by data from adjacent regions. It is assumed that changes of global westerlies and of the mobile polar high triggered the fluctuations of precipitation in the study area. However, variations in temperature in the Taklamakan Desert are presumed to be mainly controlled by the intensity of the winter monsoon.

  15. Use of Rare Earth Elements in investigations of aeolian processes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The representation of the dust cycle in atmospheric circulation models hinges on an accurate parameterization of the vertical dust flux at emission. However, existing parameterizations of the vertical dust flux vary substantially in their scaling with wind friction velocity, require input parameters...

  16. Long-term variability of dust-storms in Iceland

    NASA Astrophysics Data System (ADS)

    Dagsson-Waldhauserová, Pavla; Ólafsson, Haraldur; Arnalds, Ólafur

    2013-04-01

    Iceland is a volcanic island in the North Atlantic Ocean with maritime climate. In spite of moist climate, large areas are with limited vegetation cover where >40% of Iceland is classified with considerable to very severe erosion and 21% of Iceland are volcanic sandy deserts. Natural emissions from these sources influenced by strong winds affect not only regional air quality in Iceland ("Reykjavik haze") but dust particles are transported over the Atlantic ocean and Arctic Ocean > 1000 km at times. The study places Icelandic dust production area into international perspective, present long term frequency of dust storm events in NE Iceland, and estimate dust aerosol concentrations during reported dust events. Meteorological observations with dust presence codes and related visibility were used to identify the frequency and the long-term changes in dust production in NE Iceland. There were annually 16.4 days on average with reported dust observations on weather stations within the NE erosion area, indicating extreme dust plume activity and erosion within the NE deserts, even though the area is covered with snow during the major part of winter. During the 2000s the highest occurrence of dust events in six decades was reported. We have measured saltation and aeolian transport during dust/volcanic ash storms in Iceland which give some of the most intense wind erosion events ever measured. Icelandic dust affects the ecosystems over much of Iceland and causes regional haze. It is likely to affect the ecosystems of the oceans around Iceland, and it brings dust that lowers the albedo of the Icelandic glaciers, increasing melt-off due to global warming. The study indicates that Icelandic dust is not only a substantial source for regional air pollution, but may be considered to contribute to the Arctic haze phenomena and Arctic air pollution.

  17. Protoplanetary Dust

    NASA Astrophysics Data System (ADS)

    Apai, Dániel; Lauretta, Dante S.

    2010-01-01

    Preface; 1. Planet formation and protoplanetary dust Daniel Apai and Dante Lauretta; 2. The origins of protoplanetary dust and the formation of accretion disks Hans-Peter Gail and Peter Hope; 3. Evolution of protoplanetary disk structures Fred Ciesla and Cornelius P. Dullemond; 4. Chemical and isotopic evolution of the solar nebula and protoplanetary disks Dmitry Semenov, Subrata Chakraborty and Mark Thiemens; 5. Laboratory studies of simple dust analogs in astrophysical environments John R. Brucato and Joseph A. Nuth III; 6. Dust composition in protoplanetaty dust Michiel Min and George Flynn; 7. Dust particle size evolution Klaus M. Pontoppidan and Adrian J. Brearly; 8. Thermal processing in protoplanetary nebulae Daniel Apai, Harold C. Connolly Jr. and Dante S. Lauretta; 9. The clearing of protoplanetary disks and of the protosolar nebula Ilaira Pascucci and Shogo Tachibana; 10. Accretion of planetesimals and the formation of rocky planets John E. Chambers, David O'Brien and Andrew M. Davis; Appendixes; Glossary; Index.

  18. Protoplanetary Dust

    NASA Astrophysics Data System (ADS)

    Apai, D.´niel; Lauretta, Dante S.

    2014-02-01

    Preface; 1. Planet formation and protoplanetary dust Daniel Apai and Dante Lauretta; 2. The origins of protoplanetary dust and the formation of accretion disks Hans-Peter Gail and Peter Hope; 3. Evolution of protoplanetary disk structures Fred Ciesla and Cornelius P. Dullemond; 4. Chemical and isotopic evolution of the solar nebula and protoplanetary disks Dmitry Semenov, Subrata Chakraborty and Mark Thiemens; 5. Laboratory studies of simple dust analogs in astrophysical environments John R. Brucato and Joseph A. Nuth III; 6. Dust composition in protoplanetaty dust Michiel Min and George Flynn; 7. Dust particle size evolution Klaus M. Pontoppidan and Adrian J. Brearly; 8. Thermal processing in protoplanetary nebulae Daniel Apai, Harold C. Connolly Jr. and Dante S. Lauretta; 9. The clearing of protoplanetary disks and of the protosolar nebula Ilaira Pascucci and Shogo Tachibana; 10. Accretion of planetesimals and the formation of rocky planets John E. Chambers, David O'Brien and Andrew M. Davis; Appendixes; Glossary; Index.

  19. Intergalactic Dust

    NASA Astrophysics Data System (ADS)

    Li, A.

    2002-12-01

    We study the composition and sizes of intergalactic dust based on the expulsion of interstellar dust from the galactic disk. Interstellar grains in the Galactic disk are modelled as a mixture of amorphous silicate dust and carbonaceous dust consisting of polycyclic aromatic hydrocarbon (PAH) molecules and larger graphitic grains (Li & Draine 2001) with size distributions like those of the Milky Way dust (Weingartner & Draine 2001). We model their dynamic evolution in terms of the collective effects caused by (1) radiative acceleration, (2) gravitational attraction, (3) gas drag, (4) thermal sputtering, and (5) Lorenz force from the galactic magnetic field (Ferrara et al. 1991). Radiation pressure from the stellar disk exerts an upward force on dust grains and may ultimately expel them out of the entire galaxy. Gravitational force from the stellar, dust and gas disk as well as the dark matter halo exerts a downward force. Thermal sputtering erodes all grains to some degree but more efficiently destroys small grains. This, together with the fact that (1) very small grains (with small radiation pressure efficiencies) are not well coupled to starlight; (2) for large grains the radiative force to the gravitational force is approximately inversely proportional to grain size, acts as a size ``filter'' for dust leaking into the intergalactic space. Since the radiation pressure efficiency and the grain destruction rate are sensitive to dust composition, the relative importance of carbon dust compared to silicate dust expelled into the intergalactic space differs from that in the galactic plane. We derive the size distributions of both silicate and carbonaceous dust finally getting into the intergalactic space and obtain an intergalactic extinction curve. The predicted intergalactic infrared emission spectrum is calculated. References: Ferrara, A., Ferrini, F., Franco, J., & Barsella, B. 1991, ApJ, 381, 137 Li, A., & Draine, B.T. 2001, ApJ, 554, 778 Weingartner, J

  20. Mineral dust transport in the Arctic modelled with FLEXPART

    NASA Astrophysics Data System (ADS)

    Groot Zwaaftink, Christine; Grythe, Henrik; Stohl, Andreas

    2016-04-01

    Aeolian transport of mineral dust is suggested to play an important role in many processes. For instance, mineral aerosols affect the radiation balance of the atmosphere, and mineral deposits influence ice sheet mass balances and terrestrial and ocean ecosystems. While many efforts have been done to model global dust transport, relatively little attention has been given to mineral dust in the Arctic. Even though this region is more remote from the world's major dust sources and dust concentrations may be lower than elsewhere, effects of mineral dust on for instance the radiation balance can be highly relevant. Furthermore, there are substantial local sources of dust in or close to the Arctic (e.g., in Iceland), whose impact on Arctic dust concentrations has not been studied in detail. We therefore aim to estimate contributions of different source regions to mineral dust in the Arctic. We have developed a dust mobilization routine in combination with the Lagrangian dispersion model FLEXPART to make such estimates. The lack of details on soil properties in many areas requires a simple routine for global simulations. However, we have paid special attention to the dust sources on Iceland. The mobilization routine does account for topography, snow cover and soil moisture effects, in addition to meteorological parameters. FLEXPART, driven with operational meteorological data from European Centre for Medium-Range Weather Forecasts, was used to do a three-year global dust simulation for the years 2010 to 2012. We assess the model performance in terms of surface concentration and deposition at several locations spread over the globe. We will discuss how deposition and dust load patterns in the Arctic change throughout seasons based on the source of the dust. Important source regions for mineral dust found in the Arctic are not only the major desert areas, such as the Sahara, but also local bare-soil regions. From our model results, it appears that total dust load in the

  1. Large Aperture Electrostatic Dust Detector

    SciTech Connect

    C.H. Skinner, R. Hensley, and A.L Roquemore

    2007-10-09

    Diagnosis and management of dust inventories generated in next-step magnetic fusion devices is necessary for their safe operation. A novel electrostatic dust detector, based on a fine grid of interlocking circuit traces biased to 30 or 50 ν has been developed for the detection of dust particles on remote surfaces in air and vacuum environments. Impinging dust particles create a temporary short circuit and the resulting current pulse is recorded by counting electronics. Up to 90% of the particles are ejected from the grid or vaporized suggesting the device may be useful for controlling dust inventories. We report measurements of the sensitivity of a large area (5x5 cm) detector to microgram quantities of dust particles and review its applications to contemporary tokamaks and ITER.

  2. Stratigraphic Architecture of Aeolian Dune Interactions

    NASA Astrophysics Data System (ADS)

    Brothers, S. C.; Kocurek, G.

    2015-12-01

    Dune interactions, which consist of collisions and detachments, are a known driver of changing dune morphology and provide the dynamics for field-scale patterning. Although interactions are ubiquitous in modern dune fields, the stratigraphic record of interactions has not been explored. This raises the possibility that an entire class of signature architectures of bounding surfaces and cross-strata has gone misidentified or unrecognized. A unique data set for the crescentic dunes of the White Sands Dune Field, New Mexico, allows for the coupling of dune interactions with their resultant stratigraphic architecture. Dune interactions are documented by a decadal time-series of aerial photos and LiDAR-derived digital elevation models. Plan-view cross-strata in interdune areas provide a record tying past dune positions and morphologies to the current dunes. Three-dimensional stratigraphic architecture is revealed by imaging of dune interiors with ground-penetrating radar. The architecture of a dune defect merging with a target dune downwind consists of lateral truncation of the target dune set by an interaction bounding surface. Defect cross-strata tangentially approach and downlap onto the surface. Downwind, the interaction surface curves, and defect and adjacent target dune sets merge into a continuous set. Predictable angular relationships reflect field-scale patterns of dune migration direction and approach angle of migrating defects. The discovery of interaction architectures emphasizes that although dunes appear as continuous forms on the surface, they consist of discrete segments, each with a distinct morphodynamic history. Bedform interactions result in the morphologic recombination of dune bodies, which is manifested stratigraphically within the sets of cross-strata.

  3. Evaluation of aeolian emissions from gold mine tailings on the Witwatersrand

    NASA Astrophysics Data System (ADS)

    Ojelede, M. E.; Annegarn, H. J.; Kneen, M. A.

    2012-01-01

    The Witwatersrand is known for the high frequency of aeolian dust storm episodes arising from gold mine tailings storage facilities (TSFs). Source and ambient atmosphere are poorly characterized from the point of view of particle size distribution and human health risk assessment. For years, routine monitoring was limited to sampling of dust fallout ⩾30 μm. Sampling and analyses of source and receptor material was conducted. Thirty-two bulk soils were collected from TSF along the east-west mining corridor, and size distribution analysis was performed in the range 0.05-900 μm using a Malvern® MS-14 Particle Size Analyser. Ambient aerosols in the range 0.25-32 μm were monitored at two separate locations using a Grimm® aerosol monitor, in the vicinity of three large currently active and a dormant TSF. Statistical analyses indicate that TSFs are rich in fine erodible materials, particularly active TSFs. Concentration of ⩽PM5 and ⩽PM10 components in source material was: recent slimes (14-24 vol.%; 22-38 vol.%), older slimes (6-17 vol.%; 11-26 vol.%) and sand (1-8 vol.%; 2-12 vol.%). Concentrations of airborne aerosols were below the South African Department of Environmental Affairs 24-h limit value of 120 μg m -3. With wind speeds exceeding 7 ms -1, ambient concentration reached 2160 μg m -3. This maximum is several times higher than the limit value. Erosion of tailings storage facilities is a strong driver influencing ambient particulate matter loading with adverse health implications for nearby residents.

  4. Aeolian Processes and Landforms in River Valleys of Central Russian Plain in MIS 2

    NASA Astrophysics Data System (ADS)

    Matlakhova, Ekaterina

    2015-04-01

    Late Pleistocene terraces in river valleys of Central Russian Plain were subject to aeolian reworking after the alluvial sedimentation had finished. Severe natural conditions of LGM (cold and dry climate, scarce vegetation) contributed activation of aeolian processes. Ground water lowering because of deep pre-LGM incision of rivers made deep aeolian reworking possible at low hypsometric levels of valley bottom. We studied lithological structure of terraces in river valleys of Central Russian Plain. The key sites were located in Seim (the middle Dnieper catchment) and Khoper (the middle Don catchment) river valleys. Field data was combined with quartz grains morphoscopy technique (study of texture of sediment particles using scanning electron microscope). Wide participation of aeolian sediments in terrace deposits was detected. During this study a new technique of the distinguishing of short-term aeolian reworking of alluvial deposits using quartz grains morphoscopy technique was developed. The main problem of interpretation the results of quartz grains morphoscopy is that aeolian signals are sometimes not clear due to short duration of wind action over alluvial sands. However, detailed studies of the quartz grains surfaces under scanning electron microscope helped to solve this problem. We used scanning electron microscope JEOL JSM-661 LV and worked with magnification from ×160 to ×400 for whole grains and up to ×1800 for some parts of grains. Deep aeolian reworking of Late Pleistocene terrace alluvium in river valleys of Central Russian Plain during LGM led to the formation of aeolian covers on the terrace surfaces. Also there are many relict dunes on Late Pleistocene river terrace surfaces. Sometimes the development of aeolian processes could led to more significant changes in the shape of the valley and formation of aeolian aprons. The thickness of aeolian covers can reach 3-5 m or more. Due to this reason morphology and topography of river terraces could

  5. Desert dust deposition on Mt. Elbrus, Caucasus Mountains, Russia in 2009-2012 as recorded in snow and shallow ice core: high-resolution "provenancing", transport patterns, physical properties and soluble ionic composition

    NASA Astrophysics Data System (ADS)

    Kutuzov, S.; Shahgedanova, M.; Mikhalenko, V.; Lavrentiev, I.; Kemp, S.

    2013-04-01

    A record of dust deposition events between 2009 and 2012 on Mt. Elbrus, Caucasus Mountains derived from a snow pit and a shallow ice core is presented for the first time for this region. A combination of isotopic analysis, SEVIRI red-green-blue composite imagery, MODIS atmospheric optical depth fields derived using the Deep Blue algorithm, air mass trajectories derived using the HYSPLIT model and analysis of meteorological data enabled identification of dust source regions with high temporal (hours) and spatial (cf. 20-100 km) resolution. Seventeen dust deposition events were detected; fourteen occurred in March-June, one in February and two in October. Four events originated in the Sahara, predominantly in north-eastern Libya and eastern Algeria. Thirteen events originated in the Middle East, in the Syrian Desert and northern Mesopotamia, from a mixture of natural and anthropogenic sources. Dust transportation from Sahara was associated with vigorous Saharan depressions, strong surface winds in the source region and mid-tropospheric south-westerly flow with daily winds speeds of 20-30 m s-1 at 700 hPa level and, although these events were less frequent, they resulted in higher dust concentrations in snow. Dust transportation from the Middle East was associated with weaker depressions forming over the source region, high pressure centered over or extending towards the Caspian Sea and a weaker southerly or south-easterly flow towards the Caucasus Mountains with daily wind speeds of 12-18 m s-1 at 700 hPa level. Higher concentrations of nitrates and ammonium characterise dust from the Middle East deposited on Mt. Elbrus in 2009 indicating contribution of anthropogenic sources. The modal values of particle size distributions ranged between 1.98 μm and 4.16 μm. Most samples were characterised by modal values of 2.0-2.8 μm with an average of 2.6 μm and there was no significant difference between dust from the Sahara and the Middle East.

  6. Ulysses dust measurements near Jupiter.

    PubMed

    Grün, E; Zook, H A; Baguhl, M; Fechtig, H; Hanner, M S; Kissel, J; Lindblad, B A; Linkert, D; Linkert, G; Mann, I B

    1992-09-11

    Submicrometer- to micrometer-sized particles were recorded by the Ulysses dust detector within 40 days of the Jupiter flyby. Nine impacts were recorded within 50 Jupiter radii with most of them recorded after closest approach. Three of these impacts are consistent with particles on prograde orbits around Jupiter and the rest are believed to have resulted from gravitationally focused interplanetary dust. From the ratio of the impact rate before the Jupiter flyby to the impact rate after the Jupiter flyby it is concluded that interplanetary dust particles at the distance of Jupiter move on mostly retrograde orbits. On 10 March 1992, Ulysses passed through an intense dust stream. The dust detector recorded 126 impacts within 26 hours. The stream particles were moving on highly inclined and apparently hyperbolic orbits with perihelion distances of >5 astronomical units. Interplanetary dust is lost rather quickly from the solar system through collisions and other mechanisms and must be almost continuously replenished to maintain observed abundances. Dust flux measurements, therefore, give evidence of the recent rates of production from sources such as comets, asteroids, and moons, as well as the possible presence of interstellar grains.

  7. Physical and Chemical Characteristics of Desert Dust Deposited on Mt. Elbrus, Caucasus as Documented in Snow Pit and Shallow Core Records

    NASA Astrophysics Data System (ADS)

    Kutuzov, S.; Shahgedanova, M.; Mikhalenko, V.; Ginot, P.; Lavrentiev, I.; Popov, G.

    2013-12-01

    We present a study of dust deposition events and its physical and chemical characteristics in Caucasus Mountains as documented by snow and firn pack at Mt Elbrus. Dust samples were collected from the shallow ice cores and snow pits in 2009-2013 at the western Elbrus plateau (5150 m a.s.l.). Particle size distribution and chemical analysis (major ions, trace elements) were completed for each sample using Coulter Counter Multisizer III, scanning electron microscopy (SEM), IC and ICPMS analysis. It was shown that desert dust deposition occurred in Caucasus 4-8 times a year and originates from the Northern Sahara and the deserts of the Middle East. Analysis of volumetric particle size distributions showed that the modal values ranged between 2 μm and 4 μm although most samples were characterised by modal values of 2.0-2.8 μm with an average of 2.6 μm. These values are lower than those obtained from the ice cores in central and southern Asia following the deposition of long-travelled dust and are closer to those reported for the European Alps and the polar ice cores. All samples containing dust have a single mode which is usually interpreted as a single source region. They do not reveal any significant differences between the Saharan and the Middle Eastern sources. The annual average dust mass concentrations were 10-15 mg kg-1 which is higher than the average concentrations reported for other mountain regions and this was strongly affected by dust deposition events. The deposition of dust resulted in elevated concentrations of most ions, especially Ca2+, Mg2+, K+, and sulphates. Dust originated from multiple sources in the Middle East including Mesopotamia or passing over the Middle East was characterised by the elevated concentrations of nitrates and ammonia which is related to a high atmospheric loads of ammonium emitted by agricultural sources and high concentrations of ammonium in dust originating from this region. By contrast, samples of the Saharan dust showed

  8. Geochemical characteristics of insoluble dust as a tracer in an ice core from Miaoergou Glacier, east Tien Shan

    NASA Astrophysics Data System (ADS)

    Du, Zhiheng; Xiao, Cunde; Liu, Yaping; Wu, Guoju

    2015-04-01

    An ice core was extracted from Miaoergou Glacier, east Tien Shan, China. Concentrations of the rare earth elements (REEs) and Sr-Nd isotopic ratios were measured in insoluble dust sampled from the core. The ratios of REEs in insoluble dust were found to have characteristics typical of aeolian deposition, similar to those of sand and loess from Taklamakan. This suggests that the Taklamakan Desert might be an important source of dust reaching the Miaoergou Glacier. Sr (87Sr/86Sr average 0.718014 and range 0.717025 to 0.718958) and Nd (εNd(0) average - 9.1 and range - 9.5 to - 8.5) isotopic compositions in insoluble dust are similar to those of desert sand from Taklamakan and Gobi, suggesting that the Gobi Desert may be another major aeolian source for Miaoergou Glacier. Our results can be compared with Sr-Nd isotopic ratios from Greenland snow and ice, further demonstrating how the dust from Asian deserts contributes a high proportion of aeolian dust in the Greenland region.

  9. An integrated coastal model for aeolian and hydrodynamic sediment transport

    NASA Astrophysics Data System (ADS)

    Baart, F.; den Bieman, J.; van Koningsveld, M.; Luijendijk, A. P.; Parteli, E. J. R.; Plant, N. G.; Roelvink, J. A.; Storms, J. E. A.; de Vries, S.; van Thiel de Vries, J. S. M.; Ye, Q.

    2012-04-01

    Dunes are formed by aeolian and hydrodynamic processes. Over the last decades numerical models were developed that capture our knowledge of the hydrodynamic transport of sediment near the coast. At the same time others have worked on creating numerical models for aeolian-based transport. Here we show a coastal model that integrates three existing numerical models into one online-coupled system. The XBeach model simulates storm-induced erosion (Roelvink et al., 2009). The Delft3D model (Lesser et al., 2004) is used for long term morphology and the Dune model (Durán et al., 2010) is used to simulate the aeolian transport. These three models were adapted to be able to exchange bed updates in real time. The updated models were integrated using the ESMF framework (Hill et al., 2004), a system for composing coupled modeling systems. The goal of this integrated model is to capture the relevant coastal processes at different time and spatial scales. Aeolian transport can be relevant during storms when the strong winds are generating new dunes, but also under relative mild conditions when the dunes are strengthened by transporting sand from the intertidal area to the dunes. Hydrodynamic transport is also relevant during storms, when high water in combination with waves can cause dunes to avalanche and erode. While under normal conditions the hydrodynamic transport can result in an onshore transport of sediment up to the intertidal area. The exchange of sediment in the intertidal area is a dynamic interaction between the hydrodynamic transport and the aeolian transport. This dynamic interaction is particularly important for simulating dune evolution at timescales longer than individual storm events. The main contribution of the integrated model is that it simulates the dynamic exchange of sediment between aeolian and hydrodynamic models in the intertidal area. By integrating the numerical models, we hope to develop a model that has a broader scope and applicability than

  10. A comprehensive method for aeolian particle granulometry and micromorphology analyses.

    PubMed

    Zaady, E; Dody, A; Weiner, D; Barkai, D; Offer, Z Y

    2009-08-01

    The aim of this study was to use a new approach to investigate aeolian particle granulometry and micromorphology. Taking total aeolian deposition into account, we used parameters such as, particle area, perimeter, shape analysis for particle roughness (area/perimeter) and elongation (long/short axis). These parameters were analyzed on temporal and spatial scales at four study sites in the eastern Negev Desert, Israel. The total collection of particles was sorted into three size groups based on particle area to facilitate comparison. The classic definition of particle size (equating particle length with particle diameter) produced relatively small variations among the three size classes (25-38.6%). Our proposed comprehensive method demonstrated significant variation among the three size classes (13.9-60.8%), e.g. the classic method placed 36.4% of the particles in size class two while the new method placed 60.8% of the particles in this size class; the differences were even more significant regarding size class 3 (38.6% vs. 13.9%, respectively). The classic method did not facilitate investigation of particle roughness and elongation. With this new approach, it was possible to clearly define the particles by size class, based on these characteristics. With roughness, the variation among size classes 2 and 3 was about 27%. With elongation, the variation among size classes two and three was about 21%. Applying similar investigation method to study the aeolian particle granulometry and micromorphology can better facilitate more detailed calculation of particle size distribution, roughness and elongation. PMID:18618283

  11. The origin of transverse instability of aeolian megaripples

    NASA Astrophysics Data System (ADS)

    Yizhaq, Hezi; Katra, Itzhak; Schmerler, Erez; Silvestro, Simone

    2016-04-01

    Two different kinds of sand ripples, normal ripples and megaripples which differ in their sizes, grain-size compositions and morphology are observed in nature. While normal ripples form almost straight lines, megaripples have greater sinuosity due to their transverse instability, a property that causes small undulations to grow in time. The physical origin of this pronounced transverse instability has remained elusive. We studied ripple development in a series of wind tunnel experiments with different mixtures of sand. For unimodal fine sand, initial differences in height diminished in time leading to straight ripples. In contrast, for bimodal sand initial perturbations in height remained and even grew in time resulting in more wavy patterns. The results indicate that the differences in sinuosity between normal and megaripples are due to grain size segregation at three dimensions with a positive feedback between coarse grains and ripples height. The accumulations of coarse particles at the crest allow further growth of the ripples at these locations thus decreasing their migration rate. This in turn allows further accumulation of coarse grains. This mechanism leads to variations of the thickness of the armoring layer along the ripple crest which correlates with crest height. Field measurements of grain size distribution and sinuosity index along megaripple crests support the findings. In addition, the sinuosity of megaripples and TARs (Transverse Aeolian Ridges) on Mars at several locations was calculated from images taken from High Resolution Imaging Science Experiment (HiRISE). These images provide the capability of obtaining orbital images of Mars with a resolution down to 25 cm/pixel. The preliminary results show that due to their bimodal grain-size distribution megaripples are more undulated than TARs. This new look at aeolian bedforms on Mars can help in a better classification of them and improve the understanding of the aeolian processes involved in their

  12. China Dust

    Atmospheric Science Data Center

    2013-04-16

    ... SpectroRadiometer (MISR) nadir-camera images of eastern China compare a somewhat hazy summer view from July 9, 2000 (left) with a ... arid and sparsely vegetated surfaces of Mongolia and western China pick up large quantities of yellow dust. Airborne dust clouds from the ...

  13. Dust Storm

    Atmospheric Science Data Center

    2013-04-16

    ... April 11, 2004 (top panels) contrast strongly with the dust storm that swept across Iraq and Saudi Arabia on May 13, 2004 (bottom panels). ... Apr 11 and May 13, 2004 Images:  Dust Storm location:  Middle East thumbnail:  ...

  14. Atmospheric significance of aeolian salts in the sandy deserts of northwestern China

    NASA Astrophysics Data System (ADS)

    Zhu, B.-Q.

    2016-02-01

    Large sandy deserts in the middle latitudes of northwestern China were investigated for soluble salt variations in modern and ancient aeolian sediments, aiming to explore the environmental significance of "aeolian salts". Results revealed that aeolian salt variations have a clear relationship with the changing meridional and zonal gradients of the desert locations and the aeolian differentiation effect, but are weakly linked to local geological conditions. Atmospheric depositions of water-soluble chemical species are an important process/source contributing to aeolian salt. Sequential variations of soluble salts in sedimentary profiles interbedded with aeolian and non-aeolian deposits and their palaeoenvironmental implications in the hinterland areas of these deserts were further evaluated, based on the constraints of OSL dating and radiocarbon dating data. The results indicate that inorganic salts may be a latent geoproxy in revealing regional palaeoclimatic changes in desert areas for sediments deposited under a single depositional environment, but the interpretation should be more cautious for sediments deposited under diverse depositional conditions. This study presents evidence of the atmospheric origin of aeolian salt in sandy deserts, with limited climatic significance in palaeoenvironmental reconstruction.

  15. Distribution of Atmospheric Mineral Dust across Dryland Ecosystems (Invited)

    NASA Astrophysics Data System (ADS)

    Reynolds, R. L.; Goldstein, H.; Miller, M. E.; Neff, J. C.; Fernandez, D.; Reheis, M. C.

    2010-12-01

    Deposited atmospheric dust in surface sediments of dry landscapes can be identified using geochemical, isotopic, mineralogical, and textural methods that provide compositional contrasts between surficial sediment and local bedrock. In some settings, detrital minerals that are present in surficial sediment but absent in nearby bedrock can be used as proxies for concentration of far-traveled dust. For example, silt-sized, titanium-bearing magnetite is found in silty sediment on high, isolated landforms underlain by Mesozoic and Paleozoic sandstone, which lack such magnetite, from the Mojave Desert eastward across the Colorado Plateau. Magnetite amounts within the top 10 cm of these sediments correlate (r2= 0.54) with amounts of potential plant nutrients, revealing the importance of mineral dust to fertility across ecosystems. Systematic eastward declines in magnetite (determined using magnetic susceptibility or isothermal remanent magnetization, IRM) and Ti indicate dominant dust sources from igneous terrain in the west. Variations in lead isotopes imply that most anthropogenic dust contributions are sourced from the west, consistent with the regional distribution of urban sources. Similar relations are found across gently sloping, dominantly sandy grassland surfaces that have undergone sediment sorting by aeolian and slope-wash processes. In undisturbed settings, fertility indicators and dust amounts (derived from IRM) correlate tightly (r2 as high as 0.96 between IRM and plant nutrients), and the dust amounts are significantly greater than for settings currently grazed by domestic livestock and even those at which grazing ceased 35 years ago. These results, complemented by other field and compositional studies, reveal that disturbance of dry, upland landscapes commonly promotes wind erosion, which then depletes surfaces of originally deposited dust, including aeolian magnetite. Declines in soil fertility, soil fines, and water-holding capacity in these settings can

  16. Mars Atmospheric Chemistry in Electrified Dust Devils and Storms

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.; Delory, G. T.; Atreya, S. K.; Wong, A.-S.; Renno, N. O.; Sentmann, D. D.; Marshall, J. G.; Cummer, S. A.; Rafkin, S.; Catling, D.

    2005-01-01

    Laboratory studies, simulations and desert field tests all indicate that aeolian mixing dust can generate electricity via contact electrification or "triboelectricity". In convective structures like dust devils or storms, grain stratification (or charge separation) occurs giving rise to an overall electric dipole moment to the aeolian feature, similar in nature to the dipolar electric field generated in terrestrial thunderstorms. Previous simulation studies [1] indicate that this storm electric field on Mars can approach atmospheric breakdown field strength of 20 kV/m. In terrestrial dust devils, coherent dipolar electric fields exceeding 20 kV/m have been measured directly via electric field instrumentation. Given the expected electrostatic fields in Martian dust devils and storms, electrons in the low pressure CO2 gas can be energized via the electric field to values exceeding the electron dissociative attachment energy of both CO2 and H2O, resulting in the formation of new chemical products CO and O- and OH and H- within the storm. Using a collisional plasma physics model we present a calculation of the CO/O- and OH/H- reaction and production rates. We demonstrate that these rates vary geometrically with ambient electric field, with substantial production of dissociative products when fields approach breakdown levels of 20-30 kV/m.

  17. Bathymetry,submarine geomorphology and tectonics of the Aeolian Islands

    NASA Astrophysics Data System (ADS)

    Favalli, M.; Karatson, D.; Mazzuoli, R.; Pareschi, M. T.; Ventura, G.

    2003-04-01

    On the basis of a new DEM of the submarine portions of the Aeolian Island Arc, Southern Italy, we discuss the offshore geomorphology, morphometry and tectonics of the seven major volcanic edifices and their surroundings. Bathymetric data have been compiled from various sources. Geomorphological maps reveal important details of the submerged volcanic structures as well as tectonic lineaments that are related to the most evident on land pattern. Geomorphological and morphomnetrical data have allowed us to get an insight into the evolution of the submarine volcanoes and the relationship between tectonics and volcanism in the archipelago.

  18. A seven year record of Saharan dust outbreaks over the Central Mediterranean Sea:chemical characterization, size distribution and optical properties

    NASA Astrophysics Data System (ADS)

    Becagli, Silvia; Marconi, Miriam; Sferlazzo, Damiano; Bommarito, Carlo; Calzolai, Giulia; Chiari, Massimo; di Sarra, Alcide; Gomez-Amo, Jose Louis; Lucarelli, Franco; Meloni, Daniela; Pace, Giandomenico; Traversi, Rita; Severi, Mirko; Udisti, Roberto

    2013-04-01

    Saharan dust largely affects air pollution and climate. This study aims at determining the mineral contribution to PM10 in the Central Mediterranean Sea based on 7 years of PM10 chemical composition measurements at the island of Lampedusa (35.5°N, 12.6° E). Total content and soluble fractions of selected elements and metals are used to characterize the dust events. The soluble + insoluble contribution is determined by PIXE, (Particles Induced X-ray Emission), while the composition of the soluble fraction by ICP-AES, (Inductively coupled plasma - atomic emission spectroscopy) after extraction with HNO3 at pH1.5. The solubility of each element and its size distribution are analyzed with the aim of obtaining information on their sources, mixing processes, and availability for the environment. The Saharan dust contribution to the total PM was estimated by considering Al, Si, Ca, non-sea-salt Na, K and Fe oxides. During strong Saharan dust events PM10 is often higher than 50μg m-3, and the dust contribution is about 50%. The crustal aerosol amount and contribution to PM10 shows a very small seasonal dependence; conversely, the dust optical depth displays an evident annual cycle, with a strong summer maximum (monthly average aerosol optical depth at 500 nm as large as 0.28 in June-August). We found that only 49% of the events identified from optical properties over the air column display a high dust content at the ground level, demonstrating that Saharan dust transport frequently occurs above the marine boundary layer, with negligible or small impact on the surface aerosol properties. The average size distribution obtained by Optical Particle Counter during the days with high mineral content comprises three modes, whose median radii are at about 0.29 um, 2.2 um, and 7.2 um, respectively. Solubility of each elements present a large variability in the condition of extraction, but usually in Saharan dust events the solubility is lower than in non-Saharan dust events

  19. Responses of aeolian desertification to a range of climate scenarios in China

    NASA Astrophysics Data System (ADS)

    Wang, Xunming; Hua, Ting; Ma, Wenyong

    2016-06-01

    Aeolian desertification plays an important role in earth-system processes and ecosystems, and has the potential to greatly impact global food production. The occurrence of aeolian desertification has traditionally been attributed to increases in wind speed and temperature and decreases in rainfall. In this study, by integrating the aeolian desertification monitoring data and climate and vegetation indices, we found that although aeolian desertification is influenced by complex climate patterns and human activities, increases in rainfall and temperature and decreases in wind speed may not be the key factors of aeolian desertification controls in some regions of China. Our results show that, even when modern technical approaches are used, different approaches to desertification need to be applied to account for regional differences. These results have important implications for future policy decisions on how best to combat desertification.

  20. Biodiversity impact of the aeolian periglacial geomorphologic evolution of the Fontainebleau Massif (France)

    NASA Astrophysics Data System (ADS)

    Thiry, M.; Liron, M. N.

    2009-04-01

    Landscape features The geomorphology of the Fontainebleau Massif is noteworthy for its spectacular narrow ridges, up to 10 km long and 0.5 km wide, armored by tightly cemented sandstone lenses and which overhang sandy depressions of about 50m. Denudation of the sandstone pans lead to a highly contrasted landscape, with sandstone ridges ("platières") towering sandy depressions ("vallées") and limestone plateaus ("monts"). This forms the geological frame of the spectacular sceneries of the Fontainebleau Massif (Thiry & Liron, 2007). Nevertheless, there is little know about the erosive processes that have built-up these landscapes. Periglacial processes, and among them aeolian ones, appear significant in the development of the Fontainebleau Massif physiography. The periglacial aeolian geomorphology Dunes and dune fields are known since long and cover about 15% to 25% of the Fontainebleau Massif. The aeolian dunes developed as well on the higher parts of the landscape, as well as in the lower parts of the landscape. The dunes are especially well developed in the whole eastern part of the massif, whereas the western part of the massif is almost devoid of dunes. Nevertheless, detailed mapping shows that dunes can locally be found in the western district, they are of limited extension, restricted to the east facing backslope of outliers. Loamy-sand covers the limestone plateaus of the "monts". The loam cover is of variable thickness: schematically thicker in the central part of the plateaus, where it my reach 3 m; elsewhere it may thin down to 0,20-0,30 m, especially at the plateau edges. Blowout hollows are "negative" morphologies from where the sand has been withdrawed. Often these blowouts are decametric sized and well-delimited structures. Others, more complex structures, are made up of several elongated hectometric hollows relaying each other from and which outline deflation corridor more than 1 km long. A characteristic feature of these blowout hollows is the

  1. Factors controlling magnetism of reddish brown soil profiles from calcarenites in Southern Spain: Dust input or in-situ pedogenesis?

    NASA Astrophysics Data System (ADS)

    Liu, Qingsong; Zhang, Chunxia; Torrent, José; Barrón, Vidal; Hu, Pengxiang; Jiang, Zhaoxia; Duan, Zongqi

    2016-05-01

    Under aerobic conditions, the A and B horizons of soils are magnetically enhanced due to neoformation of ferrimagnets through pedogenesis. This study systematically investigated soils developed on calcarenites of Neogene age in southern Spain to determine the dominant factors controlling the soil magnetism. Geochemical and clay mineral analyses indicate that aeolian dust significantly contribute to the A and B horizon material of the Spanish soil. Nevertheless, the magnetic enhancement of soils can be simply attributed to the pedogenically produced ferrimagnets in-situ. Therefore, the magnetism of Spanish soils is still linked to paleoclimatic variations regardless of the complexities of aeolian inputs from the Northwestern Africa.

  2. Transport of Alaskan Dust into the Gulf of Alaska and Comparison with Similar High-Latitude Dust Environments

    NASA Technical Reports Server (NTRS)

    Crusium, John; Levy, Rob; Wang, Jun; Campbell, Rob; Schroth, Andrew W.

    2012-01-01

    Transport of Alaskan dust into the Gulf of Alaska and comparison with similar high-latitude dust environments. An airborne flux of the micronutrient iron, derived from dust originating from coastal regions may be an important contributor of iron to the Gulf of Alaska's (GoA) oligotrophic waters. Dust blowing off glacier termini and dry riverbeds is a recurring phenomenon in Alaska, usually occurring in the autumn. Since previous studies assumed that dust originating in the deserts of Asia was the largest source of . airborne iron to the GoA, the budget of aeolian deposition of iron needs to be reassessed. Since late 20 I 0, our group has been monitoring dust activity using satellites over the Copper River Delta (CRD) where the most vigorous dust plumes have been observed. Since 2011, sample aerosol concentration and their composition are being collected at Middleton Island (100km off shore of CRD). This presentation will show a summary of the ongoing dust observations and compare with other similar environments (Patagonia, Iceland) by showing case studies. Common features will be highlighted

  3. Sahara Dust

    Atmospheric Science Data Center

    2013-04-15

    article title:  Casting Light and Shadows on a Saharan Dust Storm   ... CA, for NASA's Science Mission Directorate, Washington, D.C. The Terra spacecraft is managed by NASA's Goddard Space Flight Center, ...

  4. Geochemical and magnetic characteristics of aeolian transported materials under different near-surface wind fields: An experimental study

    NASA Astrophysics Data System (ADS)

    Wang, Xunming; Lang, Lili; Hua, Ting; Zhang, Caixia; Xia, Dunsheng

    2015-06-01

    By combining field investigations, field sampling, wind-tunnel experiments, and laboratory measurements, the relationships between near-surface winds and the geochemical and magnetic characteristics of wind-transported materials were statistically analyzed. Our study was conducted using bulk surface samples from a major potential dust source area in Central Asia (the Ala Shan Plateau). Under near-surface wind velocities ranging from 8 to 22 m/s, the coefficients of variation ranged between 1.6% and 14.9% for χlf, 1.4% and 11.0% for χARM, and 0.7% and 12.3% for SIRM of the transported materials. For the 26 elements and oxides investigated, the coefficients of variation of Ti, Cr, As, Zr, Ce, Pb, and Cu in the samples were greater than 10%. No consistent patterns were found between magnetic characteristics and elemental and iron oxide concentrations as a function of variations in near-surface wind velocities. In potential dust source areas under near-surface wind velocities, there are variations in the relationships between magnetic and geochemical characteristics in the fine fractions of transported materials with different particle sizes. Given the wide variation in magnetic and geochemical characteristics of aeolian-transported materials under different near-surface winds, their use as proxies for past climate reconstruction must be carefully appraised.

  5. Element geochemical analysis of the contribution of aeolian sand to suspended sediment in desert stream flash floods.

    PubMed

    Jia, Xiaopeng; Wang, Haibing

    2014-01-01

    The interaction of wind and water in semiarid and arid areas usually leads to low-frequency flash flood events in desert rivers, which have adverse effects on river systems and ecology. In arid zones, many aeolian dune-fields terminate in stream channels and deliver aeolian sand to the channels. Although aeolian processes are common to many desert rivers, whether the aeolian processes contribute to fluvial sediment loss is still unknown. Here, we identified the aeolian-fluvial cycling process responsible for the high rate of suspended sediment transport in the Sudalaer desert stream in the Ordos plateau of China. On the basis of element geochemistry data analysis, we found that aeolian sand was similar to suspended sediment in element composition, which suggests that aeolian sand contributes to suspended sediment in flash floods. Scatter plots of some elements further confirm that aeolian sand is the major source of the suspended sediment. Factor analysis and the relation between some elements and suspended sediment concentration prove that the greater the aeolian process, the higher the suspended sediment concentration and the greater the contribution of aeolian sand to suspended sediment yield. We conclude that aeolian sand is the greatest contributor to flash floods in the Sudalaer desert stream.

  6. Element Geochemical Analysis of the Contribution of Aeolian Sand to Suspended Sediment in Desert Stream Flash Floods

    PubMed Central

    Wang, Haibing

    2014-01-01

    The interaction of wind and water in semiarid and arid areas usually leads to low-frequency flash flood events in desert rivers, which have adverse effects on river systems and ecology. In arid zones, many aeolian dune-fields terminate in stream channels and deliver aeolian sand to the channels. Although aeolian processes are common to many desert rivers, whether the aeolian processes contribute to fluvial sediment loss is still unknown. Here, we identified the aeolian-fluvial cycling process responsible for the high rate of suspended sediment transport in the Sudalaer desert stream in the Ordos plateau of China. On the basis of element geochemistry data analysis, we found that aeolian sand was similar to suspended sediment in element composition, which suggests that aeolian sand contributes to suspended sediment in flash floods. Scatter plots of some elements further confirm that aeolian sand is the major source of the suspended sediment. Factor analysis and the relation between some elements and suspended sediment concentration prove that the greater the aeolian process, the higher the suspended sediment concentration and the greater the contribution of aeolian sand to suspended sediment yield. We conclude that aeolian sand is the greatest contributor to flash floods in the Sudalaer desert stream. PMID:25089295

  7. Microphytobenthic community composition and primary production at gas and thermal vents in the Aeolian Islands (Tyrrhenian Sea, Italy).

    PubMed

    Rogelja, Manja; Cibic, Tamara; Pennesi, Chiara; De Vittor, Cinzia

    2016-07-01

    Sediment samplings were performed to investigate the microphytobenthic community and photosynthetic activity adaptations to gas emissions and higher temperature in the Aeolian Islands during a three-year period (2012-2014). Higher microphytobenthic densities were recorded at the vent stations and values were even more pronounced in relation with high temperature. The gross primary production estimates strongly depended on microphytobenthic abundance values reaching up to 45.79 ± 6.14 mgC m(-2) h(-1). High abundances were coupled with low community richness and diversity. Motile diatom living forms were predominant at all stations and the greatest differences among vent and reference stations were detected on the account of the tychopelagic forms. Morphological deformities and heavily silicified diatom frustules were also observed. A significant influence of the gas emission and high temperature on the phototrophic community was highlighted suggesting the Aeolian Islands as a good natural laboratory for studies on high CO2 and global warming effects.

  8. Microphytobenthic community composition and primary production at gas and thermal vents in the Aeolian Islands (Tyrrhenian Sea, Italy).

    PubMed

    Rogelja, Manja; Cibic, Tamara; Pennesi, Chiara; De Vittor, Cinzia

    2016-07-01

    Sediment samplings were performed to investigate the microphytobenthic community and photosynthetic activity adaptations to gas emissions and higher temperature in the Aeolian Islands during a three-year period (2012-2014). Higher microphytobenthic densities were recorded at the vent stations and values were even more pronounced in relation with high temperature. The gross primary production estimates strongly depended on microphytobenthic abundance values reaching up to 45.79 ± 6.14 mgC m(-2) h(-1). High abundances were coupled with low community richness and diversity. Motile diatom living forms were predominant at all stations and the greatest differences among vent and reference stations were detected on the account of the tychopelagic forms. Morphological deformities and heavily silicified diatom frustules were also observed. A significant influence of the gas emission and high temperature on the phototrophic community was highlighted suggesting the Aeolian Islands as a good natural laboratory for studies on high CO2 and global warming effects. PMID:27155353

  9. Theoretical analysis of particle number density in steady aeolian saltation

    NASA Astrophysics Data System (ADS)

    Kang, Liqiang; Zou, Xueyong

    2014-01-01

    Particle number density or particle concentration in aeolian saltation is one important input parameter to calculate the sand flux, kinetic energy and mid-air collision probability in the aeolian saltation and particle concentration is also related to the wind erosion capacity, hence, in the present paper, the vertical distribution of particle number density in steady aeolian saltation is analyzed based on two different types of probability density functions of vertical lift-off velocity of saltating particles: one is the PDF (probability density function) of vertical velocity of lift-off particles in the three-dimensional space defined as a type-A PDF which considers the number of particles in various velocity bins per unit volume; and the other is the PDF of vertical velocity of lift-off particles ejected from the sand bed surface in a period of time as a type-B PDF which considers the number flux of particles in various velocity bins per unit surface area. These two types of PDFs are from two different perspectives (i.e., volume- and surface-based perspectives, respectively), and can be deduced from each other. The half-normal and exponential distributions are recommended for the type-A PDF, and the corresponding type-B PDF is expressed by Rayleigh and Gamma(2) distributions. The PDF distribution pattern of vertical velocity of lift-off particles has an important influence on the vertical profile of particle number density. If the type-A PDF of vertical velocity of ejected particles is a half-normal distribution, the particle number density decays exponentially with height. If the type-A PDF is an exponential distribution, the particle number density also decreases with height. If the type-A PDF is Gamma(3) and Rayleigh distributions, the particle number density first increases, then decreases with height. The type-A and type-B height parameters, which are calculated according to the mean vertical lift-off velocity from the type-A and type-B PDFs, respectively

  10. Aeolian Abrasion at the Curiosity Landing Site: Clues to the Role of Wind in Landscape Modification

    NASA Astrophysics Data System (ADS)

    Bridges, N. T.; Le Mouélic, S.; Hallet, B.; Newman, C. E.; Rice, M. S.; Blaney, D. L.; Calef, F. J.; Herkenhoff, K. E.; Langevin, Y.; Lewis, K. W.; Maurice, S.; Pinet, P. C.; Wiens, R. C.; de Pablo, M.; Renno, N. O.

    2013-12-01

    The broad scale geomorphology of Gale Crater reflects diverse aeolian processes, from airfall settling that likely deposited much of the upper and some of the lower units of Mt. Sharp, to evidence of extensive wind exhumation and removal of material exterior to the mound, to active dunes on the crater floor. The integrated effect of aeolian sand transport can also be examined on a much smaller scale by the study of ventifacts, rocks that have been abraded by windborne particles. A diversity of ventifacts are found along Curiosity's traverse through the upper 'hummocky' (HY) geomorphic unit and the lower Yellowknife Bay (YKB) sedimentary rocks. The textures are analogous to abrasion features found on Earth and include cm-scale facets, keels, elongated pits, grooves, flutes, and basal sills. High-resolution images from ChemCam's Remote Micro-Imager also show mm-scale lineations. Evidence of differential erosion is common, with HY conglomerates (e.g., Hottah, Link) and the YKB Sheepbed mudstone unit containing distinct wind tails in the lee of resistant pebbles, and bedding features within Rocknest 3, the YKB Shaler sandstone unit, and other layered rocks displaying prominent ridge-groove topography. ChemCam LIBS depth profile data so far show no strong evidence for chemical differences in the elemental composition between abraded and non-abraded surfaces (as determined from qualitative assessment), as might be expected if there were rock coatings or weathering rinds undergoing active abrasion. Preliminary measurements of ventifact texture and wind tail orientations indicate sandblasting in HY and YKB from predominantly southwesterly and northerly directions, respectively. Based on meso-scale models of current winds and REMS results, SW flow is uncommon whereas N winds are frequent. Compositional and textural information from the suite of MSL instruments indicate that HY rocks are dominated by various types of basalt (either as whole rocks or the resistant clasts in

  11. Design and initial testing of a piezoelectric sensor to quantify aeolian sand transport

    NASA Astrophysics Data System (ADS)

    Raygosa-Barahona, Ruben; Ruiz-Martinez, Gabriel; Mariño-Tapia, Ismael; Heyser-Ojeda, Emilio

    2016-09-01

    This paper describes a sensor for measuring the mass flux of aeolian sand transport based on a low-cost piezo-electric transducer. The device is able to measure time series of aeolian sand transport. Maximum fluxes of 27 mg per second can be achieved. The design includes a sand trap, an electronic amplifier circuit and an embedded system for data collection. A field test was performed, where the basis for signal interpretation and the corresponding measurements of aeolian sand transport are presented. The sensor successfully measures fluxes driven by sea breezes of 10 ms-1, showing the importance of this process for dune-building in the region.

  12. Oxidant enhancement in martian dust devils and storms: storm electric fields and electron dissociative attachment.

    PubMed

    Delory, Gregory T; Farrell, William M; Atreya, Sushil K; Renno, Nilton O; Wong, Ah-San; Cummer, Steven A; Sentman, Davis D; Marshall, John R; Rafkin, Scot C R; Catling, David C

    2006-06-01

    Laboratory studies, numerical simulations, and desert field tests indicate that aeolian dust transport can generate atmospheric electricity via contact electrification or "triboelectricity." In convective structures such as dust devils and dust storms, grain stratification leads to macroscopic charge separations and gives rise to an overall electric dipole moment in the aeolian feature, similar in nature to the dipolar electric field generated in terrestrial thunderstorms. Previous numerical simulations indicate that these storm electric fields on Mars can approach the ambient breakdown field strength of approximately 25 kV/m. In terrestrial dust phenomena, potentials ranging from approximately 20 to 160 kV/m have been directly measured. The large electrostatic fields predicted in martian dust devils and storms can energize electrons in the low pressure martian atmosphere to values exceeding the electron dissociative attachment energy of both CO2 and H2O, which results in the formation of the new chemical products CO/O- and OH/H-, respectively. Using a collisional plasma physics model, we present calculations of the CO/O- and OH/H- reaction and production rates. We demonstrate that these rates vary geometrically with the ambient electric field, with substantial production of dissociative products when fields approach the breakdown value of approximately 25 kV/m. The dissociation of H2O into OH/H- provides a key ingredient for the generation of oxidants; thus electrically charged dust may significantly impact the habitability of Mars. PMID:16805701

  13. Aeolian features and processes at the Mars Pathfinder landing site

    USGS Publications Warehouse

    Greeley, Ronald; Kraft, Michael; Sullivan, Robert; Wilson, Gregory; Bridges, Nathan; Herkenhoff, Ken; Kuzmin, Ruslan O.; Malin, Michael; Ward, Wes

    1999-01-01

    The Mars Pathfinder landing site contains abundant features attributed to aeolian, or wind, processes. These include wind tails, drift deposits, duneforms of various types, ripplelike features, and ventifacts (the first clearly seen on Mars). Many of these features are consistant with formation involving sand-size particles. Although some features, such as dunes, could develop from saltating sand-size aggregates of finer grains, the discovery of ventifact flutes cut in rocks strongly suggests that at least some of the grains are crystalline, rather than aggregates. Excluding the ventifacts, the orientations of the wind-related features correlate well with the orientations of bright wind steaks seen on Viking Orbiter images in the general area. They also correlate with wind direction predictions from the NASA-Ames General Circulation Model (GCM) which show that the strongest winds in the area occur in the northern hemisphere winter and are directed toward 209°. Copyright 1999 by the American Geophysical Union.

  14. Armoring and vertical sorting in aeolian dune fields

    NASA Astrophysics Data System (ADS)

    Gao, Xin; Narteau, Clément; Rozier, Olivier

    2016-04-01

    Unlike ripples, there are only few numerical studies on grain-size segregation at the scale of dunes in aeolian environments. Here we use a cellular automaton model to analyze vertical sorting in granular mixtures under steady unidirectional flow conditions. We investigate the feedbacks between dune growth and the segregation mechanisms by varying the size of coarse grains and their proportion within the bed. We systematically observe the development of a horizontal layer of coarse grains at the top of which sorted bed forms may grow by amalgamation. The formation of such an armor layer controls the overall sediment transport and availability. The emergence of dunes and the transition from barchan to transverse dune fields depend only on the grain size distribution of the initial sediment layer. As confirmed by observation, this result indicates that armor layers should be present in most arid deserts, where they are likely to control dune morphodynamics.

  15. Mean flow and Reynolds stress structure over aeolian ripples

    NASA Astrophysics Data System (ADS)

    Li, Bailiang; McKenna Neuman, Cheryl; Bédard, Otto; O'Brien, Patrick

    2015-04-01

    Mean flow and turbulence structure on transverse ripples have been well documented in hydrodynamic literature. However, very few studies have described the flow characteristics over aeolian ripples. This study adopted laser Doppler anemometry (LDA) to measure the wind field above granular ripples with different bimodal particle size distributions in a wind tunnel. Multiple runs were conducted to examine the vertical profiles of time-averaged horizontal and vertical velocities and Reynolds stress above four different locations: crest, lee slope, trough, and stoss slope. The rippled sand bed has a fine beige fraction with grain size smaller than 0.542 mm concentrated in the troughs and a coarse fraction dyed in red with grain size greater than 0.542 mm concentrated in the crests. The magnitude of the ripples at equilibrium is controlled by both wind velocity and the ratio of beige sand to red sand. Freestream velocity has a range between 8-11 m/s (above the saltation threshold of beige sand and below the threshold of red sand) and the percentage coarse by mass varies from 5.2% to 27.5% with median grain size from 0.289 mm to 0.399 mm. Experimental results indicate that the ripples have the wave length ranged between 20 mm and 140 mm with a characteristic ripple index (wave length/wave height) of 15. Flow streamlines are generally parallel to the bed surface, which is inconsistent with previous hydrodynamic observations that a return flow is usually found at the lee side of the ripples. Reynolds stress has demonstrated a strong spatial differentiation near the sand surface: greatest at crests and smallest at the troughs, however, this difference diminishes with elevation. This is an exploratory study on the turbulence characteristics of air flow above aeolian ripples, and we believe the finding of this research will enhance the understanding the interaction mechanisms between the air and bed morphology.

  16. Downslope coarsening in aeolian grainflows of the Navajo Sandstone

    NASA Astrophysics Data System (ADS)

    Loope, David B.; Elder, James F.; Sweeney, Mark R.

    2012-07-01

    Downslope coarsening in grainflows has been observed on present-day dunes and generated in labs, but few previous studies have examined vertical sorting in ancient aeolian grainflows. We studied the grainflow strata of the Jurassic Navajo Sandstone in the southern Utah portion of its outcrop belt from Zion National Park (west) to Coyote Buttes and The Dive (east). At each study site, thick sets of grainflow-dominated cross-strata that were deposited by large transverse dunes comprise the bulk of the Navajo Sandstone. We studied three stratigraphic columns, one per site, composed almost exclusively of aeolian cross-strata. For each column, samples were obtained from one grainflow stratum in each consecutive set of the column, for a total of 139 samples from thirty-two sets of cross-strata. To investigate grading perpendicular to bedding within individual grainflows, we collected fourteen samples from four superimposed grainflow strata at The Dive. Samples were analyzed with a Malvern Mastersizer 2000 laser diffraction particle analyser. The median grain size of grainflow samples ranges from fine sand (164 μm) to coarse sand (617 μm). Using Folk and Ward criteria, samples are well-sorted to moderately-well-sorted. All but one of the twenty-eight sets showed at least slight downslope coarsening, but in general, downslope coarsening was not as well-developed or as consistent as that reported in laboratory subaqueous grainflows. Because coarse sand should be quickly sequestered within preserved cross-strata when bedforms climb, grain-size studies may help to test hypotheses for the stacking of sets of cross-strata.

  17. Saharan dust deposition in the Carpathian Basin and its possible effects on interglacial soil formation

    NASA Astrophysics Data System (ADS)

    Varga, György; Cserháti, Csaba; Kovács, János; Szalai, Zoltán

    2016-09-01

    Several hundred tons of windblown dust material are lifted into the atmosphere and are transported every year from Saharan dust source areas towards Europe having an important climatic and other environmental effect also on distant areas. According to the systematic observations of modern Saharan dust events, it can be stated that dust deflated from North African source areas is a significant constituent of the atmosphere of the Carpathian Basin and Saharan dust deposition events are identifiable several times in a year. Dust episodes are connected to distinct meteorological situations, which are also the determining factors of the different kinds of depositional mechanisms. By using the adjusted values of dust deposition simulations of numerical models, the annual Saharan dust flux can be set into the range of 3.2-5.4 g/m2/y. Based on the results of past mass accumulation rates calculated from stratigraphic and sedimentary data of loess-paleosol sequences, the relative contribution of Saharan dust to interglacial paleosol material was quantified. According to these calculations, North African exotic dust material can represent 20-30% of clay and fine silt-sized soil components of interglacial paleosols in the Carpathian Basin. The syngenetic contribution of external aeolian dust material is capable to modify physicochemical properties of soils and hereby the paleoclimatic interpretation of these pedogene stratigraphic units.

  18. Derivation of an observation-based map of North African dust emission

    SciTech Connect

    Evan, Amato T.; Fiedler, Stephanie; Zhao, Chun; Menut, Laurent; Schepanski, Kerstin; Flamant, C.; Doherty, Owen

    2015-03-01

    Changes in the emission, transport and deposition of aeolian dust have profound effects on regional climate, so that characterizing the lifecycle of dust in observations and improving the representation of dust in global climate models is necessary. A fundamental aspect of characterizing the dust cycle is quantifying surface dust fluxes, yet no spatially explicit estimates of this flux exist for the World’s major source regions. Here we present a novel technique for creating a map of the annual mean emitted dust flux for North Africa based on retrievals of dust storm frequency from the Meteosat Second Generation Spinning Enhanced Visible and InfraRed Imager (SEVIRI) and the relationship between dust storm frequency and emitted mass flux derived from the output of five models that simulate dust. Our results suggest that 64 (±16)% of all dust emitted from North Africa is from the Bodélé depression, and that 13 (±3)% of the North African dust flux is from a depression lying in the lee of the Aïr and Hoggar Mountains, making this area the second most important region of emission within North Africa.

  19. Changes in the Airborne Bacterial Community in Outdoor Environments following Asian Dust Events

    PubMed Central

    Yamaguchi, Nobuyasu; Park, Jonguk; Kodama, Makiko; Ichijo, Tomoaki; Baba, Takashi; Nasu, Masao

    2014-01-01

    Bacterial abundance and community compositions have been examined in aeolian dust in order to clarify their possible impacts on public health and ecosystems. The influence of transcontinentally transported bacterial cells on microbial communities in the outdoor environments of downwind areas should be determined because the rapid influx of a large amount of bacterial cells can disturb indigenous microbial ecosystems. In the present study, we analyzed bacteria in air samples (approximately 100 m3 d−1) that were collected on both Asian dust days and non-Asian dust days over 2 years (between November 2010 and July 2012). Changes in bacterial abundance and community composition were investigated based on their 16S rRNA gene amount and sequence diversity. Seasonal monitoring revealed that airborne bacterial abundance was more than 10-fold higher on severe dust days, while moderate dust events did not affect airborne bacterial abundance. A comparison of bacterial community compositions revealed that bacteria in Asian dust did not immediately disturb the airborne microbial community in areas 3,000–5,000 km downwind of dust source regions, even when a large amount of bacterial cells were transported by the atmospheric event. However, microbes in aeolian dust may have a greater impact on indigenous microbial communities in downwind areas near the dust source. Continuous temporal and spatial analyses from dust source regions to downwind regions (e.g., from the Gobi desert to China, Korea, Japan, and North America) will assist in estimating the impact of atmospherically transported bacteria on indigenous microbial ecosystems in downwind areas. PMID:24553107

  20. Preface to the Eighth International Conference on Aeolian Research - ICAR 8

    NASA Astrophysics Data System (ADS)

    Dong, Zhibao; Huang, Ning

    2015-12-01

    The papers in this special issue of Aeolian Research arise from the Eighth International Conference on Aeolian Research (ICAR8), held on July 21-25, 2014 at Lanzhou University, China. The conference was sponsored by the International Society for Aeolian Research, convened by Zhibao Dong and Ning Huang, and supported by several institutions from China. The conference was well attended by 284 participants from 20 nations. 138 oral presentations, 142 posters and 296 abstracts were organized into six sessions. The 13 papers that appear in this special issue are drawn from the post-conference submissions, which were successfully reviewed by peers, revised and accepted. Those papers that have not completed review will become regular submissions to Aeolian Research and published (if accepted) when they pass review process.

  1. Long-Term Observations of Dust Storms in Sandy Desert Environments

    NASA Astrophysics Data System (ADS)

    Yun, Hye-Won; Kim, Jung-Rack; Choi, Yun-Soo

    2015-04-01

    Mineral dust occupies the largest portion of atmospheric aerosol. Considering the numerous risks that dust poses for socioeconomic and anthropogenic activities, it is crucial to understand sandy desert environments, which frequently generate dust storms and act as a primary source of atmospheric aerosol. To identify mineral aerosol mechanisms, it is essential to monitor desert environmental factors involving dust storm generation in the long term. In this study, we focused on two major environmental factors: local surface roughness and soil moisture. Since installments of ground observation networks in sandy deserts are unfeasible, remote sensing techniques for mining desert environmental factors were employed. The test area was established within the Badain Jaran and Kubuqi Deserts in Inner Mongolia, China, where significant seasonal aeolian processes emit mineral dust that influences all of East Asia. To trace local surface roughness, we employed a multi-angle imaging spectroradiometer (MISR) image sequence to extract multi-angle viewing (MAV) topographic parameters such as normalized difference angular index, which represents characteristics of the target desert topography. The backscattering coefficient from various space-borne SAR and stereotopography were compared with MAV observations to determine calibrated local surface roughness. Soil moisture extraction techniques from InSAR-phase coherence stacks were developed and compiled with advanced scatterometer (ASCAT) soil moisture data. Combined with metrological information such as the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA interim, correlations between intensity of sand dune activity as a proxy of aeolian processes in desert environments, surface wind conditions, and surface soil moisture were traced. Overall, we have confirmed that tracking sandy desert aeolian environments for long-term observations is feasible with space-borne, multi-sensor observations when combined with

  2. Holocene aeolian activity in the Gonghe Basin, north-eastern Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Stauch, Georg; Lai, Zhongping; Lehmkuhl, Frank; Schulte, Philipp

    2016-04-01

    The Gonghe Basin is located on the north-eastern edge of Tibetan Plateau and has a mean altitude of 3000 m asl. With a size of 20.000 km² it is the largest intramontane Basin on the north-eastern Plateau. The well-studied Qinghai Basin is situated north of the Basin, while the drier central Plateau is further south-west. Previous research indicated an early onset of the aeolian accumulation in the Qinghai Basin at around 18 ka while in the areas further to the south-west aeolian archives date back only to the beginning of the Holocene. First new OSL ages from aeolian sand and loess indicate a intermediate timing of the aeolian accumulation in the Gonghe Basin at the transition from the late glacial to the Holocene. Late glacial and early Holocene ages of aeolian sediments were hitherto associated with wetter climate conditions caused by the strengthening of the Asian summer monsoon. Higher moisture availability resulted in an increased vegetation cover, leading to the permanent stabilization of the aeolian sediments. Under glacial climate conditions a constant remobilization of the sediments can be assumed. The new OSL ages from the Gonghe Basin indicate a progressive shift of the monsoonal strength in westward directions during the late glacial until the early Holocene.

  3. Identification of a late Quaternary alluvial-aeolian sedimentary sequence in the Sichuan Basin, China

    NASA Astrophysics Data System (ADS)

    Feng, Jin-Liang; Ju, Jian-Ting; Chen, Feng; Hu, Zhao-Guo; Zhao, Xiang; Gao, Shao-Peng

    2016-03-01

    The late Quaternary sedimentary sequence in the northwestern part of the Sichuan Basin consists of five lithological units and with increasing depth include the: Chengdu Clay; Brown Clay; Red Clay; Sandy Silt; and basal Muddy Gravel. The genesis, provenance and age of the sediments, as well as the possible presence of hiatuses within this sequence are debated. Measurements of grain-size, magnetic susceptibility, quartz content, quartz δ18O values, element composition, and Sr-Nd isotopic concentrations of samples from a typical sedimentary sequence in the area provides new insights into the genesis and history of the sequence. The new data confirm that the sediments in study site are alluvial-aeolian in origin, with basal alluvial deposits overlain by aeolian deposits. Like the uppermost Chengdu Clay, the underlying Brown Clay and Red Clay are aeolian in origin. In contrast, the Silty Sand, like the basal Muddy Gravel, is an alluvial deposit and not an aeolian deposit as previously thought. Moreover, the succession of the aeolian deposits very likely contains two significant sedimentary hiatuses. Sedimentological analysis demonstrates that the source materials for the aeolian deposits in the northwestern part of the Sichuan Basin and those on the eastern Tibetan Plateau are different. Furthermore, the loess deposits on the eastern Tibetan Plateau are derived from heterogeneous local sources.

  4. Source Characterization of African Dust Using CCSEM Analysis

    NASA Astrophysics Data System (ADS)

    Rogers, R.; Hunt, A.; Oldfield, F.

    2013-12-01

    A preliminary investigation is underway to determine whether African dust is developed through Pedogenic or Aeolian processes. 85 dust samples were taken from the Sahel and Saharan region of Africa and analyzed using computer controlled scanning electron microscopy (CCSEM). Optimized secondary electron detectors (SED) and back-scattered electron detectors (BSED) with adjustable quadrants was used with a light element Peltier-cooled energy dispersive x-ray spectrometer. A variable pressure system was utilized for the analysis of insulating materials, which eliminated the need for special specimen coating to dissipate charge and remove artifacts. Data from these samples are being used to address two primary questions: (1) Can CCSEM technology accurately describe elemental compounds derived from dust samples and therefore derive mineral content and (2) Are African dusts created through Pedogenic or Aeolian processes. The creation of a 19-point elemental classification system was used to separate and analyze each of the 4000 data points that were taken from 85 samples. Initial findings show large amounts of Fe, Si, and Al-rich minerals. The Al-Si-rich minerals show a close correlation in relative elemental amounts. This is to be expected from clay minerals of the pyroxene group. The Fe, Si-rich minerals trend towards an inverse relationship, which is also consistent with iron oxides of the spinel group that generally consist of magnetite. Other elemental constituents within the samples include varying amounts of Ti, Ca, and K. An initial run of samples, 6 Burkina Soils and 6 Burkina Laterites, show a similarity in chemical composition, leading to the hypothesis that the Burkina Soils originated from the Burkina Laterites. As the experiment progresses we expect to see similar Aeolian processes contributing to the mineral content of other surface dusts. Further research on the effects of these wind driven dusts is needed to assess the potential health impacts and

  5. Numerical Prediction of Dust. Chapter 10

    NASA Technical Reports Server (NTRS)

    Benedetti, Angela; Baldasano, J. M.; Basart, S.; Benincasa, F.; Boucher, O.; Brooks, M.; Chen, J. P.; Colarco, P. R.; Gong, S.; Huneeus, N.; Jones, L; Lu, S.; Menut, L.; Mulcahy, J.; Nickovic, S.; Morcrette, J.-J.; Perez, C.; Reid, J. S.; Sekiyama, T. T.; Tanaka, T.; Terradellas, E.; Westphal, D. L.; Zhang, X.-Y.; Zhou, C.-H.

    2013-01-01

    Covers the whole breadth of mineral dust research, from a scientific perspective Presents interdisciplinary work including results from field campaigns, satellite observations, laboratory studies, computer modelling and theoretical studies Explores the role of dust as a player and recorder of environmental change This volume presents state-of-the-art research about mineral dust, including results from field campaigns, satellite observations, laboratory studies, computer modelling and theoretical studies. Dust research is a new, dynamic and fast-growing area of science and due to its multiple roles in the Earth system, dust has become a fascinating topic for many scientific disciplines. Aspects of dust research covered in this book reach from timescales of minutes (as with dust devils, cloud processes, and radiation) to millennia (as with loess formation and oceanic sediments), making dust both a player and recorder of environmental change. The book is structured in four main parts that explore characteristics of dust, the global dust cycle, impacts of dust on the Earth system, and dust as a climate indicator. The chapters in these parts provide a comprehensive, detailed overview of this highly interdisciplinary subject. The contributions presented here cover dust from source to sink and describe all the processes dust particles undergo while travelling through the atmosphere. Chapters explore how dust is lifted and transported, how it affects radiation, clouds, regional circulations, precipitation and chemical processes in the atmosphere, and how it deteriorates air quality. The book explores how dust is removed from the atmosphere by gravitational settling, turbulence or precipitation, how iron contained in dust fertilizes terrestrial and marine ecosystems, and about the role that dust plays in human health. We learn how dust is observed, simulated using computer models and forecast. The book also details the role of dust deposits for climate reconstructions

  6. A 13000-year, high-resolution multi-proxy record of climate variability with episodes of enhanced atmospheric dust in Western Asia: Evidence from Neor peat complex in NW Iran

    NASA Astrophysics Data System (ADS)

    Sharifi, O.; Pourmand, A.; Canuel, E. A.; Peterson, L. C.

    2011-12-01

    The regional climate over West Asia, extending between Iran and the Arabian Peninsula to the eastern Mediterranean Sea, is governed by interactions between three major synoptic systems; mid-latitude Westerlies, the Siberian Anticyclone and the Indian Ocean Summer Monsoon. In recent years, a number of paleoclimate studies have drawn potential links between episodes of abrupt climate change during the Holocene, and the rise and fall of human civilizations across the "Fertile Crescent" of West Asia. High-resolution archives of climate variability from this region, however, are scarce, and at times contradicting. For example, while pollen and planktonic data from lakes in Turkey and Iran suggest that dry, continental conditions prevailed during the early-middle Holocene, oxygen isotope records indicate that relatively wet conditions dominated during this interval over West Asia. We present interannual to decadal multi-proxy records of climate variability from a peat complex in NW Iran to reconstruct changes in moisture and atmospheric dust content during the last 13000 years. Radiocarbon dating on 20 samples from a 775-cm peat core show a nearly constant rate of accumulation (1.7 mm yr-1, R2=0.99) since 13356 ± 116 cal yr B.P. Down-core X-ray fluorescence measurements of conservative lithogenic elements (e.g., Al, Zr, Ti) as well as redox-sensitive elements (e.g., Fe, K, Rb, Zn, Cu, and Co) at 2 mm intervals reveal several periods of elevated dust input to this region since the early Holocene. Down-core variations of total organic carbon and total nitrogen co-vary closely and are inversely correlated with conservative lithogenic elements (Al, Si, Ti), indicating a potential link between climate change and accumulation of organic carbon in the Neor peat mire. Major episodes of enhanced dust deposition (13000-12000, 11700-11200, 9200-8800, 7000-6000, 4200-3200, 2800-2200 and 1500-600 cal yr B.P) are in good agreement with other proxy records that document more arid

  7. Iron Speciation in Urban Dust

    SciTech Connect

    E Elzinga; Y Gao; J Fitts; R Tappero

    2011-12-31

    An improved understanding of anthropogenic impacts on ocean fertility requires knowledge of anthropogenic dust mineralogy and associated Fe speciation as a critical step toward developing Fe solubility models constrained by mineralogical composition. This study explored the utility of micro-focused X-ray absorption spectroscopy ({mu}-XAS) in characterizing the speciation of Fe in urban dust samples. A micro-focused beam of 10 x 7 {micro}m made possible the measurement of the Fe K edge XAS spectra of individual dust particles in the PM5.6 size fraction collected in Newark, New Jersey, USA. Spectral analysis indicated the presence of mixtures of Fe-containing minerals within individual dust particles; we observed significant magnetite content along with other Fe(III)-(hydr)oxide minerals which could not be conclusively identified. Our data indicate that detailed quantitative determination of Fe speciation requires extended energy scans to constrain the types and relative abundance of Fe species present. We observe heterogeneity in Fe speciation at the dust particle level, which underscores the importance of analyzing a statistically adequate number of particles within each dust sample. Where possible, {mu}-XAS measurements should be complemented with additional characterization techniques such as {mu}-XRD and bulk XAS to obtain a comprehensive picture of the Fe speciation in dust materials. X-ray microprobes should be used to complement bulk methods used to determine particle composition, methods that fail to record particle heterogeneity.

  8. The likelihood of observing dust-stimulated phytoplankton growth in waters proximal to the Australian continent

    NASA Astrophysics Data System (ADS)

    Cropp, R. A.; Gabric, A. J.; Levasseur, M.; McTainsh, G. H.; Bowie, A.; Hassler, C. S.; Law, C. S.; McGowan, H.; Tindale, N.; Viscarra Rossel, R.

    2013-05-01

    We develop a tool to assist in identifying a link between naturally occurring aeolian dust deposition and phytoplankton response in the ocean. Rather than examining a single, or small number of dust deposition events, we take a climatological approach to estimate the likelihood of observing a definitive link between dust deposition and a phytoplankton bloom for the oceans proximal to the Australian continent. We use a dust storm index (DSI) to determine dust entrainment in the Lake Eyre Basin (LEB) and an ensemble of modelled atmospheric trajectories of dust transport from the basin, the major dust source in Australia. Deposition into the ocean is computed as a function of distance from the LEB source and the local over-ocean precipitation. The upper ocean's receptivity to nutrients, including dust-borne iron, is defined in terms of time-dependent, monthly climatological fields for light, mixed layer depth and chlorophyll concentration relative to the climatological monthly maximum. The resultant likelihood of a dust-phytoplankton link being observed is then mapped as a function of space and time. Our results suggest that the Southern Ocean (north of 45°S), the North West Shelf, and Great Barrier Reef are ocean regions where a rapid biological response to dust inputs is most likely to be observed. Conversely, due to asynchrony between deposition and ocean receptivity, direct causal links appear unlikely to be observed in the Tasman Sea and Southern Ocean south of 45°S.

  9. News and Views: Betelgeuse bubbles up dust; Hydrothermal activity on early asteroids; Is this a record? Galaxy evolution in 3D; LOFAR looks farther; IOPD makes plans

    NASA Astrophysics Data System (ADS)

    2011-08-01

    Red supergiant star Betelgeuse is surrounded by a vast halo of silicate and aluminium dust, visible in false colour in this infrared image from the European Southern Observatory's Very Large Telescope. This material may eventually form planets around a new star. Biochemical analysis of the Tagish Lake meteorites, some of the most pristine samples of carbonaceous chondrites known, suggests that much of the variation in organic matter between different meteorite samples can be ascribed to hydrothermal activity on meteorite parent bodies. European Southern Observatory astronomers have discovered the most distant quasar yet - and reckon it is one of the brightest objects in the early universe.

  10. Dust and canopy effects on snowpack melt and ecosystem processes in a subalpine forest

    NASA Astrophysics Data System (ADS)

    Maurer, G. E.; Bowling, D. R.

    2013-12-01

    Dust deposition lowers the albedo of mountain snowpacks and can significantly impact the rate of spring snowpack melt. Recent research has shown that aeolian dust deposition may significantly advance the timing of snowmelt and spring runoff in the hydrologic basins of the western U.S. These studies have focused on alpine and subalpine snowpacks with little to no overstory vegetation cover. We conducted a manipulative experiment to assess the impacts of dust deposition on snowpack melt and ecosystem processes in a subalpine conifer forest. From mid-March to the snow all gone date in 2010-2012, we scattered dust in forested plots at weekly to bi-weekly frequency. This roughly doubled the ambient dust loading at the site. In control and dust-addition treatments we measured the springtime decline in snow water equivalent, continuous soil temperature and moisture, and litter mass loss (decomposition) and soil respiration below the snowpack and during the warm season. Xylem water potential in conifers was also measured during the warm season. We found that the effect of dust deposition on the melt rate was dependent on the openness of the canopy within our forest, as were differences in the timing and magnitude of soil moisture changes. Ecosystem processes were similar in dust-addition and control plots and were responsive to soil temperature and moisture variations below the snowpack and during the warm season. From this we conclude that the effect of aeolian dust deposition on snowpack energy balance, and associated ecohydrological processes, varies with canopy structure in subalpine forests.

  11. Dust Storm, Aral Sea

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Aral Sea has shrunk to less than half its size since 1985. The Aral Sea receives little water (sometimes no water) from the two major rivers that empty into it-the Syr Darya and Amu Darya. Instead, the river water is diverted to support irrigation for the region's extensive cotton fields. Recently, water scarcity has increased due to a prolonged drought in Central Asia. As the Aral Sea recedes, its former sea bed is exposed. The Aral's sea bed is composed of fine sediments-including fertilizers and other agricultural chemicals-that are easily picked up by the region's strong winds, creating thick dust storms. The International Space Station crew observed and recorded a large dust storm blowing eastward from the Aral Sea in late June 2001. This image illustrates the strong coupling between human activities (water diversions and irrigation), and rapidly changing land, sea and atmospheric processes-the winds blow across the

  12. Lunar and Planetary Science XXXV: Mars: Wind, Dust Sand, and Debris

    NASA Technical Reports Server (NTRS)

    2004-01-01

    The session "Mars: Wind, Dust Sand, and Debris" included: Mars Exploration Rovers: Laboratory Simulations of Aeolian Interactions; Thermal and Spectral Analysis of an Intracrater Dune Field in Amazonis Planitia; How High is that Dune? A Comparison of Methods Used to Constrain the Morphometry of Aeolian Bedforms on Mars; Dust Devils on Mars: Scaling of Dust Flux Based on Laboratory Simulations; A Close Encounter with a Terrestrial Dust Devil; Interpretation of Wind Direction from Eolian Features: Herschel Crater, Mars Erosion Rates at the Viking 2 Landing Site; Mars Dust: Characterization of Particle Size and Electrostatic Charge Distributions; Simple Non-fluvial Models of Planetary Surface Modification, with Application to Mars; Comparison of Geomorphically Determined Winds with a General Circulation Model: Herschel Crater, Mars; Analysis of Martian Debris Aprons in Eastern Hellas Using THEMIS; Origin of Martian Northern Hemisphere Mid-Latitude Lobate Debris Aprons; Debris Aprons in the Tempe/Mareotis Region of Mars;and Constraining Flow Dynamics of Mass Movements on Earth and Mars.

  13. ChemCam analysis of Martian fine dust

    NASA Astrophysics Data System (ADS)

    Lasue, Jeremie; Mangold, Nicolas; Cousin, Agnes; Meslin, Pierre-Yves; Wiens, Roger; Gasnault, Olivier; Rapin, William; Schroder, Susanne; Ollila, Ann; Fabre, Cécile; Berger, Gilles; Le Mouélic, Stéphane; Dehouck, Erwin; Forni, Olivier; Maurice, Sylvestre; Anderson, Ryan; Bridges, Nathan; Clark, Benton; Clegg, Samuel; d'Uston, Claude; Goetz, Walter; Johnson, Jeffrey R.; Lanza, Nina; Madsen, Morten; Melikechi, Noureddine; Newsom, Horton; Sautter, Violaine; Martin-Torres, Javier; Zorzano, Maria-Paz; MSL Science Team

    2016-10-01

    In this work, we examine the chemical composition of dust observed by the Chemistry Camera (ChemCam) instrument onboard the Mars Science Laboratory (MSL) rover at Gale Crater. The Laser Induced Breakdown Spectroscopy technique analyses samples without preparation, which allows detection of the elemental composition of surface deposits. Mars aeolian fine dust (<2-3 microns) composition is analyzed on the first shot of each Mars target. It is reproducible over time and present a composition characteristic of the global martian fine dust, which covers the entire planet and contributes to the local geology analyzed by MSL. Its composition can also be retrieved on the ChemCam Calibration Targets (CCCT) by subtraction of the well characterized CCCT spectra. The CCCT include eight glasses and ceramics that have been generated to simulate Martian rocks of interest and two targets of a single element (graphite for carbon and an alloy of titanium). ChemCam passive spectroscopy also indicates varying deposition of the dust cover on the CCCT.Major elements are quantified and shown to be very similar to the fine soils encountered at Gale crater. The composition is also similar to the soils and fine dust measured by APXS for the elements common to both instruments. The minor elements quantified by ChemCam (Ba, Sr, Rb, Li, Mn, Cr) are within the range of soil surveys, but we see a higher concentration of Li than in other types of remotely characterized targets. Sulfur is possibly detected at the ChemCam limit of detection. Hydrogen is clearly identified, indicating that this fine dust is a contributor to the H content of the martian soils, as also detected by the SAM and CheMin instruments, and provides constraints as to which fraction of the Martian surface is hydrated and altered. In conclusion, the finest fraction of dust particles on the surface of Mars contains hydrated components mixed intimately within the fine aeolian dust fraction, suggesting that this dust likely

  14. Natural gamma-radiation in the Aeolian volcanic arc.

    PubMed

    Chiozzi, P; Pasquale, V; Verdoya, M; Minato, S

    2001-11-01

    Pulse-height distributions of gamma-rays, obtained with a field NaI(Tl) scintillation spectrometer in numerous sites of the Lipari and Vulcano islands (Aeolian volcanic arc, Italy), were measured to determine the U, Th and K concentrations of the bedrock and the relative values of the air absorbed dose rate. U is spatially related to both Th and K and the Th/U ratio is on average 3.1-3.5. The magmatic evolution is reflected by the concentration of the three radioelements, as they are more abundant within the more felsic units of the volcanic series. The higher values of U (15.7-20.0 ppm) coincide with higher Th (48.3-65.9 ppm) and K (4.9-6.1%) concentrations associated with rhyolitic rocks of the third cycle (< 50 ky). The air absorbed dose rate varies from 20 to 470 nGy h(-1). The highest values (> 350 nGy h(-1)) are observed on outcrops of rhyolitic obsidian lava flows. The cosmic-ray contribution is also evaluated to estimate the total background radiation dose rate. PMID:11573810

  15. Energy regimes for aeolian sand grain surface textures

    NASA Astrophysics Data System (ADS)

    Marshall, J. R.; Bull, P. A.; Morgan, R. M.

    2012-05-01

    An experimental study of aeolian sand grain surface texture development was undertaken with an air-driven grain-recirculating desktop apparatus. Scanning electron microscope analysis of resulting textures indicated that different texture types can be associated with distinct zones in a grain-shape/grain speed matrix. In particular, for subrounded and rounded grains, low and high energy transport can be unequivocally distinguished by the occurrence of upturned plates and Hertzian frustra respectively. Textural development does not have a simple relationship to grain velocity, but appears to relate to the energy expended per unit area within the contact zone generated by elastic deformation during impact. Hertzian theory was adapted to irregular sand grain shapes and close agreement was found between experimental results and theoretical predictions for textural development. Results of this study improve our ability to reconstruct palaeoaeolian environments and therefore our ability to determine grain provenance; in particular, the latter is shown to have direct relevance to forensic inquiries and terrorism investigations.

  16. Shallow Submarine Hydrothermal Systems in the Aeolian Volcanic Arc, Italy

    NASA Astrophysics Data System (ADS)

    Monecke, Thomas; Petersen, Sven; Lackschewitz, Klas; Hügler, Michael; Hannington, Mark D.; Gemmell, J. Bruce

    2009-03-01

    The majority of known high-temperature hydrothermal vents occur at mid-ocean ridges and back-arc spreading centers, typically at water depths from 2000 to 4000 meters. Compared with 30 years of hydrothermal research along spreading centers in the deep parts of the ocean, exploration of the approximately 700 submarine arc volcanoes is relatively recent [de Ronde et al., 2003]. At these submarine arc volcanoes, active hydrothermal vents are located at unexpectedly shallow water depth (95% at <1600-meter depth), which has important consequences for the style of venting, the nature of associated mineral deposits, and the local biological communities. As part of an ongoing multinational research effort to study shallow submarine volcanic arcs, two hydrothermal systems in the submerged part of the Aeolian arc have been investigated in detail during research cruises by R/V Poseidon (July 2006) and R/V Meteor (August 2007). Comprehensive seafloor video surveys were conducted using a remotely operated vehicle, and drilling to a depth of 5 meters was carried out using a lander-type submersible drill. This research has resulted in the first detailed, three-dimensional documentation of shallow submarine hydrothermal systems on arc volcanoes.

  17. Natural gamma-radiation in the Aeolian volcanic arc.

    PubMed

    Chiozzi, P; Pasquale, V; Verdoya, M; Minato, S

    2001-11-01

    Pulse-height distributions of gamma-rays, obtained with a field NaI(Tl) scintillation spectrometer in numerous sites of the Lipari and Vulcano islands (Aeolian volcanic arc, Italy), were measured to determine the U, Th and K concentrations of the bedrock and the relative values of the air absorbed dose rate. U is spatially related to both Th and K and the Th/U ratio is on average 3.1-3.5. The magmatic evolution is reflected by the concentration of the three radioelements, as they are more abundant within the more felsic units of the volcanic series. The higher values of U (15.7-20.0 ppm) coincide with higher Th (48.3-65.9 ppm) and K (4.9-6.1%) concentrations associated with rhyolitic rocks of the third cycle (< 50 ky). The air absorbed dose rate varies from 20 to 470 nGy h(-1). The highest values (> 350 nGy h(-1)) are observed on outcrops of rhyolitic obsidian lava flows. The cosmic-ray contribution is also evaluated to estimate the total background radiation dose rate.

  18. Boundary-layer turbulence characteristics during aeolian saltation

    NASA Astrophysics Data System (ADS)

    Li, Bailiang; McKenna Neuman, Cheryl

    2012-06-01

    A great deal of effort has been expended in measuring turbulence phenomena in clean air flows. However, no previous measurements have been successfully made of the vertical distributions of turbulence intensity and Reynolds stress in a fully adjusted boundary-layer flow saturated with saltating particles. The present wind tunnel study addresses this knowledge gap using a custom designed laser-Doppler anemometer (LDA). The amount of turbulence is found to increase with the introduction of saltating particles to the airflow. Over the lowest 15% of boundary layer, vertical profiles of the streamwise wind speed provide friction velocities that lie well within the narrow range of those derived from direct measurement of the Reynolds stress. Relative to clean air, aeolian saltation is demonstrated to increase the magnitude but not the frequency of burst-sweep events that primarily contribute to the total fluid stress. Within several millimeters above the bed surface, all vertical profiles of wind speed converge upon a focal point, as the local fluid stress declines toward the mobile bed.

  19. Boundary-layer turbulence characteristics during aeolian saltation

    NASA Astrophysics Data System (ADS)

    Li, B.; McKenna Neuman, C. L.

    2012-12-01

    A great deal of effort has been expended in measuring turbulence phenomena in clean air flows. However, no previous measurements have been successfully made of the vertical distributions of turbulence intensity and Reynolds stress in a fully adjusted boundary-layer flow saturated with saltating particles. The present wind tunnel study addresses this knowledge gap using a custom designed laser-Doppler anemometer (LDA). The amount of turbulence is found to increase with the introduction of saltating particles to the airflow. Over the lowest 15% of boundary layer, vertical profiles of the streamwise wind speed provide friction velocities that lie well within the narrow range of those derived from direct measurement of the Reynolds stress. Relative to clean air, aeolian saltation is demonstrated to increase the magnitude but not the frequency of burst-sweep events that primarily contribute to the total fluid stress. Within several millimeters above the bed surface, all vertical profiles of wind speed converge upon a focal point, as the local fluid stress declines toward the mobile bed.

  20. Simultaneous observations of the critical aeolian threshold of two surfaces

    NASA Astrophysics Data System (ADS)

    Stout, John E.

    2007-03-01

    Threshold is an important parameter in wind erosion research and in the field of aeolian research in general. A new technique was recently developed that provides a means of determining threshold with a sampling system that continuously collects wind data along with critical information regarding saltation activity. By employing two identical sampling systems, it was possible to monitor the threshold of a highly mobile sand surface while simultaneously monitoring the threshold of a less mobile playa surface. Results indicate that threshold could be measured at both locations with enough precision to establish clear differences between the surfaces. The sandy surface at the Morgenstern Dunes site was considerably more active than the Yellow Lake playa site over the 113-day sampling period because of its consistently lower threshold. The Morgenstern site tended to maintain a fairly constant threshold of around 5.4 to 5.5 m/s whereas the threshold of the Yellow Lake playa surface varied from a low of 6.4 m/s to values greater than 13.3 m/s. Limitations of this method lie in the fact that threshold can be determined only when winds are blowing sufficiently strongly to cause sediment transport.

  1. Optical dating of aeolian dynamism on the West African Sahelian margin

    NASA Astrophysics Data System (ADS)

    Stokes, S.; Bailey, R. M.; Fedoroff, N.; O'Marah, K. E.

    2004-04-01

    The Sahelian Margin of West Africa is widely recognised as an area of recent environmental catastrophe and human suffering arising from food shortage and land degradation associated with prolonged drought. The propensity of this region to suffer drought has been related, using environmental data collected during the period of instrumental records, to a combination of low mean annual rainfall levels and a high degree of rainfall variability which relates to sea surface temperature anomalies in the adjacent tropical Atlantic Ocean. Despite the significant environmental and human consequences of such droughts, there is a paucity of long-term environmental data for the West African Sahel. Aeolian dune reactivations in this area are a potentially highly useful environmental archive of past periods of extended drought conditions, which may have resulted in localised or widespread dune reactivation. Here we describe the initial results from an ongoing programme of research, which seeks to develop a detailed record of past dune reactivations in Mali. We find evidence for repeated Holocene dune reactivation events and a significant number of reactivations, which commenced at the time of onset of the last major drought cycle in the early 1970s. We obtain ages as young as 20-30 years for some significant dune units (thickness up to 1 m) and describe the results of experiments which test the performance of our dating exercise. We specifically test for the significance of preheat temperature on single aliquot regeneration (SAR) equivalent dose determinations and recycling ratios; neither are found vary significantly as a function of preheating. Optical dating of sand sized quartz could provide a useful tool for palaeogeographical mapping of ancient and historical dune reactivations in this region and elsewhere.

  2. Landscape evolution on Mars - A model of aeolian denudation in Gale Crater

    NASA Astrophysics Data System (ADS)

    Day, M. D.; Kocurek, G.; Grotzinger, J. P.

    2015-12-01

    Aeolian erosion has been the dominant geomorphic agent to shape the surface of Mars for the past ~3.5 billion years. Although individual geomorphic features evidencing aeolian activity are well understood (e.g., yardangs, dune fields, and wind streaks), landscapes formed by aeolian erosion remain poorly characterized. Intra-crater sedimentary mounds are hypothesized to have formed by wind deflation of craters once filled with flat-lying strata, and, therefore, should be surrounded by landscapes formed by aeolian erosion. Here we present a landscape evolution model that provides both an initial characterization of aeolian landscapes, and a mechanism for large-scale excavation. Wind excavation of Gale Crater to form the 5 km high Mount Sharp would require removal of 6.4 x 104 km3 of sediment. Imagery in Gale Crater from satellites and the Mars Science Laboratory rover Curiosity shows a surface characterized by first-cycle aeolian erosion of bedrock. The overall landscape is interpreted to represent stages in a cycle of aeolian deflation and excavation, enhanced by physical weathering (e.g., thermal fracturing, cratering). Initial wind erosion of bedrock is enhanced along fractures, producing retreating scarps. Underlying less resistant layers then erode faster than the armoring cap rock, increasing relief in scarps to form retreating mesas. As scarp retreat continues, boulders from the armoring cap unit break away and cover the hillslopes of less resistant material below the scarps. Eventually all material from the capping unit is eroded away and a boulder-capped hill remains. Winnowing of fine material flattens hillslope topography, leaving behind a desert pavement. Over long enough time, this pavement is breached and the cycle begins anew. This cycle of landscape denudation by the wind is similar to that of water, but lacks characteristic subaqueous features such as dendritic drainage networks.

  3. Aeolian process-induced hyper-concentrated flow in a desert watershed

    NASA Astrophysics Data System (ADS)

    Ta, Wanquan; Wang, Haibin; Jia, Xiaopeng

    2014-04-01

    Ephemeral desert channels are characterized by very high rates of sediment transport during infrequent flood events. Here we show that aeolian process-induced hyper-concentrated (AHC) flows occur in the Sudalaer desert watershed in the Ordos Plateau of China, which primarily transport 0.08-0.25 mm non-cohesive aeolian sand and have a peak suspended sediment concentration of 1.1-1.4 × 106 mg l-3. Aeolian sand supply and storage in the channel play a crucial role in causing hyper-concentrated flow. Our results indicate that non-cohesive aeolian sand can be entrained from the bed and suspended in the turbulent flow when the channel bed slope exceeds a critical threshold (0.0003). We also show that if the frequency ratio of wind-blown sandstorms to rainstorms Tw/Tp exceeds β(γ - γ0)/α (P/V3) (A/L) (where α is the wind-blown sand transport coefficient, β is the runoff coefficient, γ - γ0 is the increase in suspension concentration caused by addition of aeolian sands, P is the density of rainstorms, V is the wind speed of sandstorms, A is the runoff-generating area, L is the aeolian sand-filled channel length), an AHC flow occurs during the passage of a flood in a desert channel. Since high-frequency aeolian processes provide an adequate quantity of transportable sediment and promote AHC flow, most of the infrequent rainfall-induced floods occurring in arid zones can develop as AHC flows.

  4. Dust Complex onboard the ExoMars-2018 lander for investigations of Martian dust dynamics

    NASA Astrophysics Data System (ADS)

    Zakharov, Alexander; Horanyi, Mihaly; Afonin, Valeri; Esposito, Francesca; Seran, Elena; Gotlib, Vladimir; Koepke, Mark; Kuznetsov, Ilya; Lyash, Andrey; Dolnikov, Gennady

    The load of suspended dust in the Martian atmosphere varies dramatically but never drops entirely to zero. Effects of airborne dust contribute to the dynamic and thermodynamic evolution of the atmosphere and its large-scale circulation processes on diurnal, seasonal and annual time-scales. Suspended dust plays a key role in determining the present climate of Mars and probably influenced the past climatic conditions and surface evolution. Atmosphere dust and windblown dust are responsible for erosion, redistribution of dust on the surface, and surface weathering. The mechanisms for dust entrainment in the atmosphere are not completely understood, as the current data available so far do not allow us to identify the efficiency of the various processes. Dust-grain transport on the surface of Mars has never been directly measured despite great interest in and high scientific and technological ramifications of the associated phenomena. This paper describes planned, future investigations of the Martian dust environment made possible by the proposed scientific payload “Dust Complex” (DC) of the ExoMars-2018 mission’s landing platform. DC is a suite of four sensors devoted to the study of Aeolian processes on Mars with a primary aim of monitoring the diurnal, seasonal, and annual dust-environment cycles by Martian-ground-based measurements of dust flux in situ, i.e., in the near-surface atmosphere of Mars. This suite includes 1) an Impact Sensor, for the measurement of the sand-grain dynamics and electrostatics, 2) a particle-counter sensor, MicroMED, for the measurement of airborne dust size distribution and number density, 3) an Electric Probe, for the measurement of the ambient electric field, and 4) a radiofrequency antenna. Besides outlining design details of DC and the characterisation of its capabilities, this presentation reviews various dust effects and dust phenomena that are anticipated to occur in the near-surface environment on Mars and that are possible

  5. Aeolian erosion and sand transport over the Mejillones Pampa in the coastal Atacama Desert of northern Chile

    NASA Astrophysics Data System (ADS)

    Flores-Aqueveque, Valentina; Alfaro, Stéphane; Muñoz, Ricardo; Rutllant, José A.; Caquineau, Sandrine; Le Roux, Jacobus P.; Vargas, Gabriel

    2010-08-01

    The Mejillones Peninsula in the coastal Atacama Desert of northern Chile is a region in which ocean-atmosphere-land interactions are particularly strong, resulting in enhanced alongshore winds that erode the surface and transport sand particles to the sea. Because the aeolian particles in the laminated sediments at the bottom of Mejillones Bay record long-term changes in the intensity of prevailing southerly winds, it is fundamental to understand aeolian processes such as wind erosion and sand transport to improve paleoceanographic reconstructions. The aim of the present study is to characterize the wind erosion process over the flat geomorphology of the northern portion of the Mejillones Peninsula, the Mejillones Pampa, including the influence of wind erosion on the initial particle size distribution and the associated fractionation processes of the mineralogical composition of moving particles, through field measurements. In addition, we test the ability of an existing saltation model (MB95) to reproduce the variability of the erosion process during the field experiment. Soil samples from 17 locations on this flat surface contain significant amounts of highly erodible particles with diameters in the 200-300 µm and 100-150 µm size ranges. Aeolian particles collected in BSNE sand traps located at different heights near the surface, exhibit a bimodal size distribution similar to that of the erodible fraction of the soils; the abundance of the fine class increasing with height. Small stones that have a spatially variable distribution can locally reduce the intensity of wind erosion. The mineralogical composition of moving particles is similar to that of the soils, with quartz, feldspar and calcite as the most important minerals, followed by clay minerals, gypsum and amphibole. A value of u*t is calculated for each soil particle size class. Subsequently, the elementary contribution of each size class to the horizontal flux is calculated using White (1979)'s equation

  6. Abundances of Volatile - Bearing Species from Evolved Gas Analysis of Samples from the Rocknest Aeolian Bedform in Gale Crater

    NASA Technical Reports Server (NTRS)

    Archer, P. D., Jr.; Franc, H. B.; Sutter, B.; McAdam, A.; Ming, D. W.; Morris, R. V.; Mahaffy, P. R.

    2013-01-01

    The Sample Analysis at Mars (SAM) instrument suite on board the Mars Science Laboratory (MSL) recently ran four samples from an aeolian bedform named Rocknest. SAM detected the evolution of H2O, CO2, O2, and SO2, indicative of the presence of multiple volatile bearing species (Fig 1). The Rocknest bedform is a windblown deposit selected as representative of both the windblown material in Gale crater as well as the globally-distributed martian dust. Four samples of Rocknest material were analyzed by SAM, all from the fifth scoop taken at this location. The material delivered to SAM passed through a 150 m sieve and is assumed to have been well mixed during the sample acquisition/preparation/handoff process. SAM heated the Rocknest samples to approx.835 C at a ramp rate of 35 C/min with a He carrier gas flow rate of apprx.1.5 standard cubic centimeters per minute and at an oven pressure of 30 mbar [1]. Evolved gases were detected by a quadrupole mass spectrometer (QMS). This abstract presents the molar abundances of H2O, CO2, O2, and SO2 as well as their concentration in rocknest samples using an estimated sample mass.

  7. Sand transport by wind, erosion and deposition and the origin of aeolian bedforms

    NASA Astrophysics Data System (ADS)

    Duran Vinent, Orencio

    2014-05-01

    Aeolian processes involve the wind action on a sedimentary substrate, namely erosion, sand transport and deposition. They are responsible for the emergence of aeolian dunes and ripples. Here, we discuss the physics of aeolian sediment transport from a physical point of view. Relevant time and length scales associated to turbulent wind fluctuations are summarized using aerodynamic theory. At the microscopic scale, the main forces acting on the grains are detailed. Sand transport is then studied using two phase numerical simulations based on a discrete element method for particles coupled to a continuum Reynolds averaged description of hydrodynamics. We then introduce the concepts - e.g. saturated flux, saturation length - and the relevant framework for the development of a continuum (macroscopic) quantitative description of transport at the core of our current understanding of aeolian dunes formation. At smaller scales, aeolian ripples arise from the interaction of sediment transport and topography. At larger scales, the nonlinear nature of the interaction between dunes leads to the formation of dune fields.

  8. Aeolian and fluvial processes in dryland regions: the need for integrated studies

    USGS Publications Warehouse

    Belnap, Jayne; Munson, Seth M.; Field, Jason P.

    2011-01-01

    Aeolian and fluvial processes play a fundamental role in dryland regions of the world and have important environmental and ecological consequences from local to global scales. Although both processes operate over similar spatial and temporal scales and are likely strongly coupled in many dryland systems, aeolian and fluvial processes have traditionally been studied separately, making it difficult to assess their relative importance in drylands, as well as their potential for synergistic interaction. Land degradation by accelerated wind and water erosion is a major problem throughout the world's drylands, and although recent studies suggest that these processes likely interact across broad spatial and temporal scales to amplify the transport of soil resources from and within drylands, many researchers and land managers continue to view them as separate and unrelated processes. Here, we illustrate how aeolian and fluvial sediment transport is coupled at multiple spatial and temporal scales and highlight the need for these interrelated processes to be studied from a more integrated perspective that crosses traditional disciplinary boundaries. Special attention is given to how the growing threat of climate change and land-use disturbance will influence linkages between aeolian and fluvial processes in the future. We also present emerging directions for interdisciplinary needs within the aeolian and fluvial research communities that call for better integration across a broad range of traditional disciplines such as ecology, biogeochemistry, agronomy, and soil conservation.

  9. Mars Orbiter Camera climatology of textured dust storms

    NASA Astrophysics Data System (ADS)

    Guzewich, Scott D.; Toigo, Anthony D.; Kulowski, Laura; Wang, Huiqun

    2015-09-01

    We report the climatology of "textured dust storms", those dust storms that have visible structure on their cloud tops that are indicative of active dust lifting, as observed in Mars Daily Global Maps produced from Mars Orbiter Camera wide-angle images. Textured dust storms predominantly occur in the equinox seasons while both solstice periods experience a planet-wide "pause" in textured dust storm activity. These pauses correspond to concurrent decreases in global atmospheric dust opacity. Textured dust storms most frequently occur in Acidalia Planitia, Chryse Planitia, Arcadia Planitia, and Hellas basin. To examine the nature of the link between textured dust storms and atmospheric dust opacity, we compare the textured dust storm climatology with a record of atmospheric dust opacity and find a peak global correlation coefficient of approximately 0.5 with a lag of 20-40° in solar longitude in the opacity compared to the solar climatology. This implies that textured dust storms observed at 1400 local time by MOC are responsible for a large fraction of atmospheric dust opacity and that other mechanisms (e.g., dust devil lifting or storm-scale lifting not observed in this study) may supply a comparable amount of dust.

  10. Iron speciation in urban dust

    SciTech Connect

    Elzinga, E.J.; Fitts, J.; Gao, Y.; Tappero, R.

    2011-08-01

    An improved understanding of anthropogenic impacts on ocean fertility requires knowledge of anthropogenic dust mineralogy and associated Fe speciation as a critical step toward developing Fe solubility models constrained by mineralogical composition. This study explored the utility of micro-focused X-ray absorption spectroscopy ({mu}-XAS) in characterizing the speciation of Fe in urban dust samples. A micro-focused beam of 10 x 7 {mu}m made possible the measurement of the Fe K edge XAS spectra of individual dust particles in the PM5.6 size fraction collected in Newark, New Jersey, USA. Spectral analysis indicated the presence of mixtures of Fe-containing minerals within individual dust particles; we observed significant magnetite content along with other Fe(III)-(hydr)oxide minerals which could not be conclusively identified. Our data indicate that detailed quantitative determination of Fe speciation requires extended energy scans to constrain the types and relative abundance of Fe species present. We observe heterogeneity in Fe speciation at the dust particle level, which underscores the importance of analyzing a statistically adequate number of particles within each dust sample. Where possible, {mu}-XAS measurements should be complemented with additional characterization techniques such as {mu}-XRD and bulk XAS to obtain a comprehensive picture of the Fe speciation in dust materials. X-ray microprobes should be used to complement bulk methods used to determine particle composition, methods that fail to record particle heterogeneity. Keywords - Urban dust; Iron; Speciation; Micro-focused X-ray absorption spectroscopy.

  11. Erupted cumulate fragments in rhyolites from Lipari (Aeolian Islands)

    NASA Astrophysics Data System (ADS)

    Forni, Francesca; Ellis, Ben S.; Bachmann, Olivier; Lucchi, Federico; Tranne, Claudio A.; Agostini, Samuele; Dallai, Luigi

    2015-12-01

    Over the last ~267 ky, the island of Lipari has erupted magmas ranging in compositions from basaltic andesites to rhyolites, with a notable compositional gap in the dacite field. Bulk geochemical and isotopic compositions of the volcanic succession, in conjunction with major and trace elemental compositions of minerals, indicate that the rhyolites were dominantly generated via crystal fractionation processes, with subordinate assimilation. Radiogenic (Sr, Nd, and Pb) and stable (O) isotopes independently suggest ≤30 % of crustal contamination with the majority of it occurring in mafic compositions, likely relatively deep in the system. Within the rhyolites, crystal-rich, K2O-rich enclaves are common. In contrast to previous interpretations, we suggest that these enclaves represent partial melting, remobilization and eruption of cumulate fragments left-over from rhyolite melt extraction. Cumulate melting and remobilization is supported by the presence of (1) resorbed, low-temperature minerals (biotite and sanidine), providing the potassic signature to these clasts, (2) reacted Fo-rich olivine, marking the presence of mafic recharge, (3) An38-21 plagioclase, filling the gap in feldspar composition between the andesites and the rhyolites and (4) strong enrichment in Sr and Ba in plagioclase and sanidine, suggesting crystallization from a locally enriched melt. Based on Sr-melt partitioning, the high-Sr plagioclase would require ~2300 ppm Sr in the melt, a value far in excess of Sr contents in Lipari and Vulcano magmas (50-1532 ppm) but consistent with melting of a feldspar-rich cumulate. Due to the presence of similar crystal-rich enclaves within the rhyolites from Vulcano, we propose that the eruption of remobilized cumulates associated with high-SiO2 rhyolites may be a common process at the Aeolian volcanoes, as already attested for a variety of volcanic systems around the world.

  12. Identification of Dust Source Regions at High-Resolution and Dynamics of Dust Source Mask over Southwest United States Using Remote Sensing Data

    NASA Astrophysics Data System (ADS)

    Sprigg, W. A.; Sahoo, S.; Prasad, A. K.; Venkatesh, A. S.; Vukovic, A.; Nickovic, S.

    2015-12-01

    Identification and evaluation of sources of aeolian mineral dust is a critical task in the simulation of dust. Recently, time series of space based multi-sensor satellite images have been used to identify and monitor changes in the land surface characteristics. Modeling of windblown dust requires precise delineation of mineral dust source and its strength that varies over a region as well as seasonal and inter-annual variability due to changes in land use and land cover. Southwest USA is one of the major dust emission prone zone in North American continent where dust is generated from low lying dried-up areas with bare ground surface and they may be scattered or appear as point sources on high resolution satellite images. In the current research, various satellite derived variables have been integrated to produce a high-resolution dust source mask, at grid size of 250 m, using data such as digital elevation model, surface reflectance, vegetation cover, land cover class, and surface wetness. Previous dust source models have been adopted to produce a multi-parameter dust source mask using data from satellites such as Terra (Moderate Resolution Imaging Spectroradiometer - MODIS), and Landsat. The dust source mask model captures the topographically low regions with bare soil surface, dried-up river plains, and lakes which form important source of dust in southwest USA. The study region is also one of the hottest regions of USA where surface dryness, land use (agricultural use), and vegetation cover changes significantly leading to major changes in the areal coverage of potential dust source regions. A dynamic high resolution dust source mask have been produced to address intra-annual change in the aerial extent of bare dry surfaces. Time series of satellite derived data have been used to create dynamic dust source masks. A new dust source mask at 16 day interval allows enhanced detection of potential dust source regions that can be employed in the dust emission and

  13. 10 years of aeolian geomorphology at the EGU: past achievements and future challenges

    NASA Astrophysics Data System (ADS)

    Baas, Andreas C. W.; Wiggs, Giles F. S.; Claudin, Philippe

    2016-04-01

    On this tenth anniversary of the Aeolian Processes & Landforms session at the EGU the original conveners review and reflect on the recent achievements and expansion in aeolian geomorphological research, focussing on advances in our understanding of sand transport processes, dune development and dynamics, and the mechanisms and scalings involved. This talk will highlight the variety and impact of the dramatic increase in the extent and interest of research on aeolian processes and landforms in the last ten years, including the increasingly strong community presence at international meetings, the diversity and extent of collaborations across subject boundaries, and the application of new measurement technologies and mathematical approaches. We conclude with a forward-looking prospectus of exciting future challenges and open research questions.

  14. Vegetation and substrate properties of aeolian dune fields in the Colorado River corridor, Grand Canyon, Arizona

    USGS Publications Warehouse

    Draut, Amy E.

    2011-01-01

    This report summarizes vegetation and substrate properties of aeolian landscapes in the Colorado River corridor through Grand Canyon, Arizona, in Grand Canyon National Park. Characterizing these parameters provides a basis from which to assess future changes in this ecosystem, including the spread of nonnative plant species. Differences are apparent between aeolian dune fields that are downwind of where modern controlled flooding deposits new sandbars (modern-fluvial-sourced dune fields) and those that have received little or no new windblown sand since river regulation began in the 1960s (relict-fluvial-sourced dune fields). The most substantial difference between modern- and relict-fluvial-sourced aeolian dune fields is the greater abundance of biologic soil crust in relict dune fields. These findings can be used with similar investigations in other geomorphic settings in Grand Canyon and elsewhere in the Colorado River corridor to evaluate the health of the Colorado River ecosystem over time.

  15. Canyon Dust

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA03682 Canyon Dust

    These dust slides are located on the wall of Thithonium Chasma.

    Image information: VIS instrument. Latitude -4.1N, Longitude 275.7E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  16. Dust Slides

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA03677 Linear Clouds

    Dust slides are common in the dust covered region called Lycus Sulci. A large fracture is also visible in this image.

    Image information: VIS instrument. Latitude 28.1N, Longitude 226.3E. 18 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  17. Dust agglomeration

    NASA Technical Reports Server (NTRS)

    2000-01-01

    John Marshall, an investigator at Ames Research Center and a principal investigator in the microgravity fluid physics program, is studying the adhesion and cohesion of particles in order to shed light on how granular systems behave. These systems include everything from giant dust clouds that form planets to tiny compressed pellets, such as the ones you swallow as tablets. This knowledge should help us control the grains, dust, and powders that we encounter or use on a daily basis. Marshall investigated electrostatic charge in microgravity on the first and second U.S. Microgravity Laboratory shuttle missions to see how grains aggregate, or stick together. With gravity's effects eliminated on orbit, Marshall found that the grains of sand that behaved ever so freely on Earth now behaved like flour. They would just glom together in clumps and were quite difficult to disperse. That led to an understanding of the prevalence of the electrostatic forces. The granules wanted to aggregate as little chains, like little hairs, and stack end to end. Some of the chains had 20 or 30 grains. This phenomenon indicated that another force, what Marshall believes to be an electrostatic dipole, was at work.(The diagram on the right emphasizes the aggregating particles in the photo on the left, taken during the USML-2 mission in 1995.)

  18. Landscape-Scale Interpretation of the Loess Record

    NASA Astrophysics Data System (ADS)

    Mason, J. A.

    2008-12-01

    Intensive OSL dating and a growing array of paleoecological and paleoclimatic proxies hold great promise for extracting new insights from the loess record, but are by necessity applied to a limited number of sections. These well-studied sections need to be placed within the broader context of the complex, landscape-scale geomorphic, ecological, and pedological processes that interact to produce the loess record. Source- proximal locations where loess accumulation can be exceptionally rapid potentially offer high-resolution paleoenvironmental records; however, observations in the Great Plains, the Upper Mississippi Valley, and the Chinese Loess Plateau demonstrate that geomorphic complexity is also greatest in these proximal settings. Large variations in loess thickness over short distances, together with streamlined hills and fluted landscapes, are most plausibly interpreted as the result of spatially variable remobilization of loess by aeolian as well as hillslope processes. An intriguing hypothesis is that some striking wind-aligned landforms result from catastrophic wind erosion of coarse noncohesive proximal loess. Remobilization by any means can clearly lead to incomplete records, but less easily detected effects could also be important. Loess grain size and deposition rate decrease rapidly with distance from the proximal edge of the loess deposit. If that edge shifts over time through large-scale wind erosion or stabilization of loess in previously unstable areas, nearby locations could experience large changes in grain size or accumulation rate not directly linked to regional climate. These changes could in turn affect proxies that respond to local vegetation or to the effectiveness of pedogenic processes. For example, the stable carbon isotope composition of organic matter records a shift toward greater C3 plant abundance at some sites in the central Great Plains, during Holocene episodes of accelerated dust influx from nearby active dunefields, possibly

  19. Perchlorate in dust fall and indoor dust in Malta: An effect of fireworks.

    PubMed

    Vella, Alfred J; Chircop, Cynthia; Micallef, Tamara; Pace, Colette

    2015-07-15

    We report on the presence of perchlorate in the settleable dust of Malta, a small central Mediterranean island. Both dust fall collected directly as it precipitated from atmosphere over a period of one month and deposited indoor dust from domestic residences were studied. Perchlorate was determined by ion chromatography of water extracts of the collected dusts. Dust fall was collected from 43 towns during 2011 to 2013 and indoor dust was sampled from homes in the same localities. Perchlorate was detected in 108 of 153 samples of dust fall (71%) and in 28 of 37 indoor dust samples (76%). Detectable perchlorate in dust fall ranged from 0.52μgg(-1) to 561μgg(-1) with a median value of 6.2μgg(-1); in indoor dust, levels were from 0.79μgg(-1) to 53μgg(-1) with a median value of 7.8μgg(-1), the highest recorded anywhere to date. Statistical analysis suggested that there was no significant difference in perchlorate content of indoor dust and dust fall. Perchlorate levels in dust fall escalate during the summer in response to numerous religious feasts celebrated with fireworks and perchlorate persists at low μgg(-1) concentrations for several months beyond the summer festive period. In Malta, perchlorate derives exclusively from KClO4, imported for fireworks manufacture. Its residue in dust presents an exposure risk to the population, especially via ingestion by hand to mouth transfer. Our results suggest that wherever intensive burning of fireworks takes place, the environmental impact may be much longer lived than realised, mainly due to re-suspension and deposition of contaminated settled dust in the urban environment.

  20. Perchlorate in dust fall and indoor dust in Malta: An effect of fireworks.

    PubMed

    Vella, Alfred J; Chircop, Cynthia; Micallef, Tamara; Pace, Colette

    2015-07-15

    We report on the presence of perchlorate in the settleable dust of Malta, a small central Mediterranean island. Both dust fall collected directly as it precipitated from atmosphere over a period of one month and deposited indoor dust from domestic residences were studied. Perchlorate was determined by ion chromatography of water extracts of the collected dusts. Dust fall was collected from 43 towns during 2011 to 2013 and indoor dust was sampled from homes in the same localities. Perchlorate was detected in 108 of 153 samples of dust fall (71%) and in 28 of 37 indoor dust samples (76%). Detectable perchlorate in dust fall ranged from 0.52μgg(-1) to 561μgg(-1) with a median value of 6.2μgg(-1); in indoor dust, levels were from 0.79μgg(-1) to 53μgg(-1) with a median value of 7.8μgg(-1), the highest recorded anywhere to date. Statistical analysis suggested that there was no significant difference in perchlorate content of indoor dust and dust fall. Perchlorate levels in dust fall escalate during the summer in response to numerous religious feasts celebrated with fireworks and perchlorate persists at low μgg(-1) concentrations for several months beyond the summer festive period. In Malta, perchlorate derives exclusively from KClO4, imported for fireworks manufacture. Its residue in dust presents an exposure risk to the population, especially via ingestion by hand to mouth transfer. Our results suggest that wherever intensive burning of fireworks takes place, the environmental impact may be much longer lived than realised, mainly due to re-suspension and deposition of contaminated settled dust in the urban environment. PMID:25828411

  1. Interstellar Dust: Contributed Papers

    NASA Technical Reports Server (NTRS)

    Tielens, Alexander G. G. M. (Editor); Allamandola, Louis J. (Editor)

    1989-01-01

    A coherent picture of the dust composition and its physical characteristics in the various phases of the interstellar medium was the central theme. Topics addressed included: dust in diffuse interstellar medium; overidentified infrared emission features; dust in dense clouds; dust in galaxies; optical properties of dust grains; interstellar dust models; interstellar dust and the solar system; dust formation and destruction; UV, visible, and IR observations of interstellar extinction; and quantum-statistical calculations of IR emission from highly vibrationally excited polycyclic aromatic hydrocarbon (PAH) molecules.

  2. Dust emissions and dune mobilization in the southern Kalahari: possible effects on biotic-abiotic interactions in the Earth system (Invited)

    NASA Astrophysics Data System (ADS)

    D'Odorico, P.; Bhattachan, A.; Zobeck, T. M.; Baddock, M.; Dintwe, K.; Okin, G. S.

    2010-12-01

    Dust emissions from terrestrial landscapes affect global biogeochemical cycles, climate, and human health. Most sources of atmospheric dust are located in the northern hemisphere, while the southern hemisphere remains relatively dust free. The activation of new sources of dust emission is typically associated either with losses/reductions in vegetation cover or with the drying of lakes and rivers. Here we show how, by mobilizing ancient aeolian deposits at the southern and south-western edges of the Kalahari’s sand sea, the loss of vegetation cover resulting from overgrazing and rangeland degradation may activate important new dust sources in the southern hemisphere. We investigate the implications of these dust emissions on local soil nutrient availability, the stability and resilience of the stabilizing vegetation, and the fertilization of the Southern Ocean.

  3. Active aeolian processes on Mars: A regional study in Arabia and Meridiani Terrae

    NASA Astrophysics Data System (ADS)

    Silvestro, S.; Vaz, D. A.; Fenton, L. K.; Geissler, P. E.

    2011-10-01

    We present evidence of widespread aeolian activity in the Arabia Terra/Meridiani region (Mars), where different kinds of aeolian modifications have been detected and classified. Passing from the regional to the local scale, we describe one particular dune field in Meridiani Planum, where two ripple populations are distinguished by means of different migration rates. Moreover, a consistent change in the ripple pattern is accompanied by significant dune advancement (between 0.4-1 meter in one Martian year) that is locally triggered by large avalanche features. This suggests that dune advancement may be common throughout the Martian tropics.

  4. Active aeolian processes on Mars: A regional study in Arabia and Meridiani Terrae

    USGS Publications Warehouse

    Silvestro, S.; Vaz, D.A.; Fenton, L.K.; Geissler, P.E.

    2011-01-01

    We present evidence of widespread aeolian activity in the Arabia Terra/Meridiani region (Mars), where different kinds of aeolian modifications have been detected and classified. Passing from the regional to the local scale, we describe one particular dune field in Meridiani Planum, where two ripple populations are distinguished by means of different migration rates. Moreover, a consistent change in the ripple pattern is accompanied by significant dune advancement (between 0.4-1 meter in one Martian year) that is locally triggered by large avalanche features. This suggests that dune advancement may be common throughout the Martian tropics. ?? 2011 by the American Geophysical Union.

  5. Dust in the Earth system: the biogeochemical linking of land, air and sea.

    PubMed

    Ridgwell, Andy J

    2002-12-15

    Understanding the response of the Earth's climate system to anthropogenic perturbation has been a pressing priority for society since the late 1980s. However, recent years have seen a major paradigm shift in how such an understanding can be reached. Climate change demands analysis within an integrated 'Earth-system' framework, taken to encompass the suite of interacting physical, chemical, biological and human processes that, in transporting and transforming materials and energy, jointly determine the conditions for life on the whole planet. This is a highly complex system, characterized by multiple nonlinear responses and thresholds, with linkages often between apparently disparate components. The interconnected nature of the Earth system is wonderfully illustrated by the diverse roles played by atmospheric transport of mineral 'dust', particularly in its capacity as a key pathway for the delivery of nutrients essential to plant growth, not only on land, but perhaps more importantly, in the ocean. Dust therefore biogeochemically links land, air and sea. This paper reviews the biogeochemical role of mineral dust in the Earth system and its interaction with climate, and, in particular, the potential importance of both past and possible future changes in aeolian delivery of the micro-nutrient iron to the ocean. For instance, if, in the future, there was to be a widespread stabilization of soils for the purpose of carbon sequestration on land, a reduction in aeolian iron supply to the open ocean would occur. The resultant weakening of the oceanic carbon sink could potentially offset much of the carbon sequestered on land. In contrast, during glacial times, enhanced dust supply to the ocean could have 'fertilized' the biota and driven atmospheric CO(2) lower. Dust might even play an active role in driving climatic change; since changes in dust supply may affect climate, and changes in climate, in turn, influence dust, a 'feedback loop' is formed. Possible feedback

  6. Dust Measurements in Tokamaks

    SciTech Connect

    Rudakov, D; Yu, J; Boedo, J; Hollmann, E; Krasheninnikov, S; Moyer, R; Muller, S; Yu, A; Rosenberg, M; Smirnov, R; West, W; Boivin, R; Bray, B; Brooks, N; Hyatt, A; Wong, C; Fenstermacher, M; Groth, M; Lasnier, C; McLean, A; Stangeby, P; Ratynskaia, S; Roquemore, A; Skinner, C; Solomon, W M

    2008-04-23

    Dust production and accumulation impose safety and operational concerns for ITER. Diagnostics to monitor dust levels in the plasma as well as in-vessel dust inventory are currently being tested in a few tokamaks. Dust accumulation in ITER is likely to occur in hidden areas, e.g. between tiles and under divertor baffles. A novel electrostatic dust detector for monitoring dust in these regions has been developed and tested at PPPL. In DIII-D tokamak dust diagnostics include Mie scattering from Nd:YAG lasers, visible imaging, and spectroscopy. Laser scattering resolves size of particles between 0.16-1.6 {micro}m in diameter; the total dust content in the edge plasmas and trends in the dust production rates within this size range have been established. Individual dust particles are observed by visible imaging using fast-framing cameras, detecting dust particles of a few microns in diameter and larger. Dust velocities and trajectories can be determined in 2D with a single camera or 3D using multiple cameras, but determination of particle size is problematic. In order to calibrate diagnostics and benchmark dust dynamics modeling, pre-characterized carbon dust has been injected into the lower divertor of DIII-D. Injected dust is seen by cameras, and spectroscopic diagnostics observe an increase of carbon atomic, C2 dimer, and thermal continuum emissions from the injected dust. The latter observation can be used in the design of novel dust survey diagnostics.

  7. Metal dusting

    SciTech Connect

    Edited by K. Natesan

    2004-01-01

    This workshop was held soon after the September 11th incident under a climate of sorrow and uncertainty among the people of the world, in particular the Workshop participants and their host organizations. With considerable help from the partiicpants, the Workshop was conducted as planed and we had excellent participation in spite of the circumstances. A good fraction of the attendees in the Workshop were from abroad and from several industries, indicating the importance and relevance of the subject for the chemical process industry. Degradation of structural metallic alloys by metal dusting has been an issue for over 40 years in the chemical, petrochemical, syngas, and iron ore reduction plants. However, the fundamental scientific reasons for the degradation of complex alloys in high carbon activity environments are not clear. one of the major parameters of importance is the variation in gas chemistry in both the laboratory experiments and in the plant-service environments. the industry has questioned the applicability of the laboratory test data, obtained in low steam environments, in assessment and life prediction for the materials in plant service where the environments contain 25-35% steam. Several other variables such as system pressure, gas flow velocity, incubation time, alloy chemistry, surface finish, and weldments, were also identified in the literature as to having an effect on the initiatino and propagation of metal dusting attack. It is the purpose of this Workshop to establish a forum in which the researchers from scientific and industrial laboratories, alloy manufacturers, end users, and research and development sponsors can exchange information, discuss different points of view, prioritize the issues, and to elaborate on the trends in industry for the future. We believe that we accomplished these goals successfully and sincerely thank the participants for their contributions.

  8. Dust Devil Populations and Statistics

    NASA Astrophysics Data System (ADS)

    Lorenz, Ralph D.; Jackson, Brian K.

    2016-08-01

    The highly-skewed diameter and pressure drop distributions of dust devils on Earth and Mars are noted, and challenges of presenting and comparing different types of observations are discussed. The widely-held view that Martian dust devils are larger than Earth's is critically assessed: the question is confounded somewhat by different observation techniques, but some indication of a {˜} 3x larger population on Mars is determined. The largest and most intense (in a relative pressure sense) devils recorded are on Mars, although the largest reported number density is on Earth. The difficulties of concepts used in the literature of `average' diameter, pressure cross section, and area fraction are noted in the context of estimating population-integral effects such as dust lifting.

  9. Gully annealing by fluvially-sourced Aeolian sand: remote sensing investigations of connectivity along the Fluvial-Aeolian-hillslope continuum on the Colorado River

    USGS Publications Warehouse

    Sankey, Joel B.; East, Amy E.; Collins, Brian D.; Caster, Joshua

    2015-01-01

    Processes contributing to development of ephemeral gully channels are of great importance to landscapes worldwide, and particularly in dryland regions where soil loss and land degradation from gully erosion pose long-term, land-management problems. Whereas gully formation has been relatively well studied, much less is known of the processes that anneal gullies and impede their growth. This work investigates gully annealing by aeolian sediment, along the Colorado River downstream of Glen Canyon Dam in Glen, Marble, and Grand Canyons, Arizona, USA (Figure 1). In this segment of the Colorado River, gully erosion potentially affects the stability and preservation of archaeological sites that are located within valley margins. Gully erosion occurs as a function of ephemeral, rainfall-induced overland flow associated with intense episodes of seasonal precipitation. Measurements of sediment transport and topographic change have demonstrated that fluvial sand in some locations is transported inland and upslope by aeolian processes to areas affected by gully erosion, and aeolian sediment activity can be locally effective at counteracting gully erosion (Draut, 2012; Collins and others, 2009, 2012; Sankey and Draut, 2014). The degree to which specific locations are affected by upslope wind redistribution of sand from active channel sandbars to higher elevation valley margins is termed “connectivity”. Connectivity is controlled spatially throughout the river by (1) the presence of upwind sources of fluvial sand within the contemporary active river channel (e.g., sandbars), and (2) bio-physical barriers that include vegetation and topography that might impede aeolian sediment transport. The primary hypothesis of this work is that high degrees of connectivity lead to less gullying potential.

  10. Electrostatic Dust Detection and Removal in Tokamaks

    NASA Astrophysics Data System (ADS)

    Hensley, R.; Skinner, C. H.; Roquemore, A. L.

    2006-10-01

    The inventory of in-vessel dust particles in next-step tokamaks will increase with the rise in stored energy and pulse duration. Dust levels will need to be measured and controlled for safety reasons and to avoid plasma contamination. A novel electrostatic dust detector has been developed with a sensitivity appropriate for the carbon dust levels expected in next-step devices.^23 Higher sensitivity is desired for real-time measurements in contemporary tokamaks that have less dust. We report on results from a larger area, more sensitive detector. A 2 x 2 circuit board has two interlocking combs of copper traces spaced by 25 microns and biased at 30-50 V. The carbon test dust is delivered to the circuit board by a mesh tray vibrated at 60 Hz. The impinging dust creates a short circuit and the resulting current pulse is recorded. We will present results on the dust detection sensitivity and dust removal efficiency of these new detectors in three environments: air, vacuum, and inert gas. ^2 C. Voinier et al., J. Nucl. Mater. 346 (2005) 266-271. ^3 C. Parker et al., PPPL Report, PPPL-4169.

  11. Perspective View, Mt. Etna, Italy & the Aeolian Islands

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Italy's Mount Etna and the Aeolian Islands are the focus of this perspective view made from an Advanced Spaceborne Thermal and Emission Radiometer (ASTER) image from NASA's Terra spacecraft overlaid on Shuttle Radar Topography Mission (SRTM) topography. The image is looking south with the islands of Lipari and Vulcano in the foreground and Etna with its dark lava flows on the skyline. Vulcano also hosts an active volcano, the cone of which is prominent. In late October 2002, Etna erupted again, sending lava flows down the north and south sides of the volcano. The north flows are near the center of this view, but the ASTER image is from before the eruption.

    In addition to the terrestrial applications of these data for understanding active volcanoes and hazards associated with them such as lava flows and explosive eruptions, geologists studying Mars find these data useful as an analog to martian landforms and geologic processes. In late September 2002, a field conference with the theme of Terrestrial Analogs to Mars focused on Mount Etna allowing Mars geologists to see in person the types of features they can only sample remotely.

    Elevation data used in this image was acquired by SRTM aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., for NASA's Earth Science Enterprise, Washington, D

  12. Microtopography-Induced Lag Formation on Bedforms and Biogenic Structures in Aeolian Settings

    NASA Astrophysics Data System (ADS)

    Buynevich, I. V.

    2010-12-01

    In a variety of sand-dominated depositional settings, high-energy events typically culminate with the formation of a lag deposit, expressed as an increase in coarse fraction, accumulation of shell fragments, or a concentration of heavy minerals (density >2.9) beyond their background values. In aeolian settings, grain impact plays a greater role in sediment transport than under subaqueous conditions, but there is a similar segregation of minerals by size and density due to different threshold entrainment and fall velocities of sand grains. For fine-to-medium sand transition, near-surface wind velocities increase from 4.5 m/s for quartz to 6.5 m/s for magnetite, which has twice the density. Most heavy minerals occur in a finer fraction of the surface sediment layer, which further increases their entrainment threshold due to high pivot angles and sheltering by the lighter minerals. Prolonged periods of increased wind activity generate heavy-mineral-enriched horizons ranging in thickness from a few grain diameters to more than 10-20 cm, producing distinct marker horizons and placers of economic importance. However, even under relatively low wind regime, localized density lag may form due to minor variations in topography and bed roughness. This process was exemplified along Revere Beach (Massachusetts, USA), where a series of 15-cm-high steps were installed at the base of a low seawall to prevent the formation of aeolian ramp that facilitated frequent overtopping. During the following months, a clear trend was established where the heavy-mineral fraction (primarily almandine garnet) progressively increased in a landward direction, toward higher substrate elevations. In natural settings with even a small background fraction of heavy minerals (2-5%), microtopographic highs of less than 1 cm are sufficient for the formation of a density lag. In a backshore area of Assateague Island (Maryland, USA), a clear increase in heavy-mineral content (mostly magnetite) was observed

  13. Modeling the processing of mineral iron during dust transport

    NASA Astrophysics Data System (ADS)

    Vogelsberg, Ulrike; Wolke, Ralf; Tilgner, Andreas; Tegen, Ina; Herrmann, Hartmut

    2014-05-01

    The Saharan desert and the Gobi desert are the main contributors to Aeolian desert dust, which is a major source of micronutrients to the remote ocean regions. Micronutrients, such as transition metals like iron or copper, are regarded essential for biological processes of different marine species. In this context recent studies have shown that soluble iron, since it is generally the most abundant transition metal in dust particles, has the ability to control marine productivity and thereby likely influence the CO2- budget. Nevertheless, the processing of desert dust leading to the release of soluble iron still lacks sufficient understanding since several factors control the solubilization process. Especially anthropogenic emissions are regarded to significantly add to the amount of soluble iron by acidification of dust particles or by the direct emission of soluble iron comprised, e.g. in coal fly ash. For the investigation of the dissolution process of iron that takes place during dust transportation the spectral air parcel model SPACCIM is used. A mechanism describing the precipitation and dissolution of mineral particles by heterogeneous surface reactions has been implemented. Trajectory properties were derived from COSMO-MUSCAT simulations or from re-analysis data by HYSPLIT. Differences in the chemical composition and the amount of anthropogenic and naturally emitted species on the North African continent and the highly industrialized region of South-East Asia have considerable impact on the acidification of the desert dust. Under this aspect, special cases of dust outbreaks of the Saharan desert and the Gobi desert are investigated and compared with focus on soluble iron produced.

  14. Dust deposition on the Mars Exploration Rover Panoramic Camera (Pancam) calibration targets

    USGS Publications Warehouse

    Kinch, K.M.; Sohl-Dickstein, J.; Bell, J.F.; Johnson, J. R.; Goetz, W.; Landis, G.A.

    2007-01-01

    The Panoramic Camera (Pancam) on the Mars Exploration Rover mission has acquired in excess of 20,000 images of the Pancam calibration targets on the rovers. Analysis of this data set allows estimates of the rate of deposition and removal of aeolian dust on both rovers. During the first 150-170 sols there was gradual dust accumulation on the rovers but no evidence for dust removal. After that time there is ample evidence for both dust removal and dust deposition on both rover decks. We analyze data from early in both rover missions using a diffusive reflectance mixing model. Assuming a dust settling rate proportional to the atmospheric optical depth, we derive spectra of optically thick layers of airfall dust that are consistent with spectra from dusty regions on the Martian surface. Airfall dust reflectance at the Opportunity site appears greater than at the Spirit site, consistent with other observations. We estimate the optical depth of dust deposited on the Spirit calibration target by sol 150 to be 0.44 ?? 0.13. For Opportunity the value was 0.39 ?? 0.12. Assuming 80% pore space, we estimate that the dust layer grew at a rate of one grain diameter per ???100 sols on the Spirit calibration target. On Opportunity the rate was one grain diameter per ???125 sols. These numbers are consistent with dust deposition rates observed by Mars Pathfinder taking into account the lower atmospheric dust optical depth during the Mars Pathfinder mission. Copyright 2007 by the American Geophysical Union.

  15. Dust feed mechanism

    DOEpatents

    Milliman, Edward M.

    1984-01-01

    The invention is a dust feed device for delivery of a uniform supply of dust for long periods of time to an aerosolizing means for production of a dust suspension. The device utilizes at least two tandem containers having spiral brushes within the containers which transport the dust from a supply to the aerosolizer means.

  16. Wind-blown origin of Dongwan late Miocene Pliocene dust sequence documented by land snail record in western Chinese Loess Plateau

    NASA Astrophysics Data System (ADS)

    Li, Fengjiang; Wu, Naiqin; Pei, Yunpeng; Hao, Qingzhen; Rousseau, Denis-Didier

    2006-05-01

    Recently, the first late Miocene Pliocene eolian deposits from the western Chinese Loess Plateau have been reported. These deposits would complement the eolian record between Quaternary loess-paleosol sequences and Miocene loess sequences, if their wind-blown origin could be documented. However, although several lines of evidence indicate the eolian origin of this sequence, it is still necessary to address this issue through further efforts. Among these, biological approaches are of particular value. Here we analyze the composition and preservation conditions of mollusk assemblages in the Dongwan section. Our results show that all mollusk fossil individuals are preserved in perfect condition without indicating any reworking. All identifiable mollusk species are terrestrial, and are mostly identical to those identified in the Quaternary loess-paleosol sequences of the Chinese Loess Plateau. Generally, the cold-aridiphilous species are dominant in the loess layers, while thermo-humidiphilous species are mostly encountered in the paleosols. The close similarity of the mollusk record in both the Dongwan late Miocene Pliocene deposits and the Quaternary loess sequence in the Chinese Loess Plateau supports the supposition that the Dongwan section is a typical loess-paleosol sequence, and is, without any doubt, of wind-blown origin.

  17. Atmospheric mineral dust in dryland ecosystems: Applications of environmental magnetism

    NASA Astrophysics Data System (ADS)

    Reynolds, Richard L.; Goldstein, Harland L.; Miller, Mark E.

    2010-07-01

    Magnetic properties of shallow (<10-cm depth), fine-grained surficial sediments contrast greatly with those of immediately underlying bedrock across much of the dry American Southwest. At 26 study sites in fine-grained (<63 μm) surficial sediments isolated from alluvial inputs, isothermal remanent magnetization (IRM; mean of 67 samples = 6.72 × 10-3 Am2 kg-1) is more than two orders of magnitude greater than that for underlying Paleozoic and Mesozoic sedimentary rocks. This contrast is mainly caused by the presence of silt-size, titanium-bearing magnetite particles in the surficial deposits and their absence in bedrock. Because of their size, composition, and isolated location, the magnetite particles represent a component of atmospheric dust likely deposited over the past few centuries. The positive correlation of sediment-IRM values with amounts of potential plant nutrients reveals the importance of atmospheric dust to soil fertility over much of the American Southwest. Subsequent disturbance of landscapes, by domestic livestock grazing as an example, commonly results in wind erosion, which then depletes exposed surfaces of original aeolian magnetite and associated fine-grained sediment. Declines in soil fertility and water-holding capacity in these settings can be estimated in some field settings via decreases in magnetic susceptibility, relative to nearby undisturbed areas. Along gentle hillslope gradients of the Colorado Plateau, field measures for aeolian magnetite demonstrate that the redistribution of deposited atmospheric dust influences landscape-level patterns in the distribution of invasive exotic plant species. Our results indicate that environmental magnetism has high potential for assessing the development and degradation of dry landscapes elsewhere.

  18. A process-based model for aeolian sediment transport and spatiotemporal varying sediment availability

    NASA Astrophysics Data System (ADS)

    Hoonhout, Bas M.; Vries, Sierd de

    2016-08-01

    Aeolian sediment transport is influenced by a variety of bed surface properties, like moisture, shells, vegetation, and nonerodible elements. The bed surface properties influence aeolian sediment transport by changing the sediment transport capacity and/or the sediment availability. The effect of bed surface properties on the transport capacity and sediment availability is typically incorporated through the velocity threshold. This approach appears to be a critical limitation in existing aeolian sediment transport models for simulation of real-world cases with spatiotemporal variations in bed surface properties. This paper presents a new model approach for multifraction aeolian sediment transport in which sediment availability is simulated rather than parameterized through the velocity threshold. The model can cope with arbitrary spatiotemporal configurations of bed surface properties that either limit or enhance the sediment availability or sediment transport capacity. The performance of the model is illustrated using four prototype cases, the simulation of two wind tunnel experiments from literature and a sensitivity analysis of newly introduced parameters.

  19. Aeolian nutrient fluxes following wildfire in sagebrush steppe: Implications for soil carbon storage

    USGS Publications Warehouse

    Hasselquist, N.J.; Germino, M.J.; Sankey, J.B.; Ingram, L.J.; Glenn, N.F.

    2011-01-01

    Pulses of aeolian transport following fire can profoundly affect the biogeochemical cycling of nutrients in semi-arid and arid ecosystems. Our objective was to determine horizontal nutrient fluxes during an episodic pulse of aeolian transport that occurred following a wildfire in a semi-arid sagebrush steppe ecosystem in southern Idaho, USA. We also examined how temporal trends in nutrient fluxes were affected by changes in particle sizes of eroded mass as well as nutrient concentrations associated with different particle size classes. In the burned area, total carbon (C) and nitrogen (N) fluxes were as high as 235 g C m????'1 d????'1 and 19 g N m????'1 d????'1 during the first few months following fire, whereas C and N fluxes were negligible in an adjacent unburned area throughout the study. Temporal variation in C and N fluxes following fire was largely attributable to the redistribution of saltation-sized particles. Total N and organic C concentrations in the soil surface were significantly lower in the burned relative to the unburned area one year after fire. Our results show how an episodic pulse of aeolian transport following fire can affect the spatial distribution of soil C and N, which, in turn, can have important implications for soil C storage. These findings demonstrate how an ecological disturbance can exacerbate a geomorphic process and highlight the need for further research to better understand the role aeolian transport plays in the biogeochemical cycling of C and N in recently burned landscapes. ?? 2011 Author(s).

  20. A tribute to Michael R. Raupach for contributions to aeolian fluid dynamics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Since the early work of Bagnold in the 1940s, aeolian research has grown to become a major integral part of earth-system studies. Many individuals have contributed to this development, and Dr. Michael R. Raupach (MR2, 1950 – 2015) was one of the most outstanding. MR2 worked for about a decade (1985 ...

  1. A modeling study of aeolian erosion enhanced by surface wind confluences over Mexico City

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Using erosion and air quality models, a study on the effect of PM10 episodes in Mexico City is presented. The important contribution of Aeolian erosion on urban air quality, its genesis, morphology, location and regional implications such as the role played by surface confluences, the dry Lake of T...

  2. A Fuzzy Cognitive Model of aeolian instability across the South Texas Sandsheet

    NASA Astrophysics Data System (ADS)

    Houser, C.; Bishop, M. P.; Barrineau, C. P.

    2014-12-01

    Characterization of aeolian systems is complicated by rapidly changing surface-process regimes, spatio-temporal scale dependencies, and subjective interpretation of imagery and spatial data. This paper describes the development and application of analytical reasoning to quantify instability of an aeolian environment using scale-dependent information coupled with conceptual knowledge of process and feedback mechanisms. Specifically, a simple Fuzzy Cognitive Model (FCM) for aeolian landscape instability was developed that represents conceptual knowledge of key biophysical processes and feedbacks. Model inputs include satellite-derived surface biophysical and geomorphometric parameters. FCMs are a knowledge-based Artificial Intelligence (AI) technique that merges fuzzy logic and neural computing in which knowledge or concepts are structured as a web of relationships that is similar to both human reasoning and the human decision-making process. Given simple process-form relationships, the analytical reasoning model is able to map the influence of land management practices and the geomorphology of the inherited surface on aeolian instability within the South Texas Sandsheet. Results suggest that FCMs can be used to formalize process-form relationships and information integration analogous to human cognition with future iterations accounting for the spatial interactions and temporal lags across the sand sheets.

  3. Atmospheric stability and diurnal patterns of aeolian saltation on the Llano Estacado

    NASA Astrophysics Data System (ADS)

    Lanigan, David; Stout, John; Anderson, William

    2016-06-01

    Aeolian transport is driven by aerodynamic surface stress imposed by turbulent winds in the Earth's atmospheric boundary layer (ABL). ABL regime is influenced by stratification, which can either enhance or suppress production of turbulence by shear associated with the vertical gradient of streamwise velocity. During the day and night, surface heat fluxes induce a negative (unstable) and positive (stable) vertical gradient of potential temperature, respectively, which modifies the role of buoyancy in turbulence production. During the brief morning and evening transition periods, the vertical gradient of potential temperature vanishes (neutral stratification). The Monin-Obukhov similarity theory describes how the vertical gradient of streamwise velocity varies with stratification. Simultaneous field measurement of wind speed and aeolian activity were obtained over a 218-day period on a bare, sandy surface on the high plains of the Llano Estacado region of west Texas. Wind speed was measured at a height of 2 m with a propeller-type anemometer and aeolian activity was measured at the surface with a piezoelectric saltation sensor. We have used the wind speed measurements within the framework of the Monin-Obukhov similarity theory to estimate "typical" shear velocity, u∗ , of the ABL as stratification is varied (characterized with the stability parameter). This approach results in a color flood contour of u∗ against time of day and stability parameter: the procedure demonstrates that aeolian activity is most likely to occur during the day, when buoyancy acts in conjunction with mechanical shear to increase u∗ .

  4. Atmospheric stability and diurnal patterns of aeolian saltation on the Llano Estacado

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aeolian transport is driven by aerodynamic surface stress imposed by turbulent winds in the Earth’s atmospheric boundary layer (ABL). ABL regime is influenced by stratification, which can either enhance or suppress production of turbulence by shear associated with the vertical gradient of streamwise...

  5. Aeolian nutrient fluxes following wildfire in sagebrush steppe: implications for soil carbon storage

    NASA Astrophysics Data System (ADS)

    Hasselquist, N. J.; Germino, M. J.; Sankey, J. B.; Ingram, L. J.; Glenn, N. F.

    2011-08-01

    Pulses of aeolian transport following fire can profoundly affect the biogeochemical cycling of nutrients in semi-arid and arid ecosystems. Our objective was to determine horizontal nutrient fluxes during an episodic pulse of aeolian transport that occurred following a wildfire in a semi-arid sagebrush steppe ecosystem in southern Idaho, USA. We also examined how temporal trends in nutrient fluxes were affected by changes in particle sizes of eroded mass as well as nutrient concentrations associated with different particle size classes. In the burned area, total carbon (C) and nitrogen (N) fluxes were as high as 235 g C m-1 d-1 and 19 g N m-1 d-1 during the first few months following fire, whereas C and N fluxes were negligible in an adjacent unburned area throughout the study. Temporal variation in C and N fluxes following fire was largely attributable to the redistribution of saltation-sized particles. Total N and organic C concentrations in the soil surface were significantly lower in the burned relative to the unburned area one year after fire. Our results show how an episodic pulse of aeolian transport following fire can affect the spatial distribution of soil C and N, which, in turn, can have important implications for soil C storage. These findings demonstrate how an ecological disturbance can exacerbate a geomorphic process and highlight the need for further research to better understand the role aeolian transport plays in the biogeochemical cycling of C and N in recently burned landscapes.

  6. A review of Computational Fluid Dynamics (CFD) airflow modelling over aeolian landforms

    NASA Astrophysics Data System (ADS)

    Smyth, Thomas A. G.

    2016-09-01

    Aeolian landforms occur on all earths' continents as well as on Mars, Titan and Venus and are typically formed where sediment is eroded and/or deposited by near surface wind flow. As wind flow approaches an aeolian landform, secondary flow patterns are created that cause wind to deviate in both speed and direction, producing complex patterns of sediment erosion, deposition and transportation. Computational Fluid Dynamics (CFD) modelling of wind flow has become a common tool to predict and understand secondary wind flow and resulting sediment transport. Its use has progressed from simulating wind flow over simple two dimensional dune shapes, to calculating a multitude of flow parameters over a range of increasingly complex landforms. Analysis of 25 peer reviewed journal articles, found that CFD has been crucial to providing additional insight to flow dynamics on the stoss slope of dunes, the structure and nature of wind flow separation in the lee of landforms and information on localised wind flow variations in large-scale dune fields. The findings of this assay demonstrate that further research is required regarding the parameterisation and modelling of surface roughness, the incorporation of accurate sediment transport to wind flow models, and the prediction of topographic surface changes. CFD is anticipated to be increasingly utilised in aeolian geomorphology and this work aims to be a starting point for aeolian geomorphologists wishing to better understand and review the utilisation of the technique to date.

  7. Detection and Preliminary Assessment of Source Areas of the 15 December 2003 Dust Storm in the Chihuahuan Desert, Southwestern North America

    NASA Astrophysics Data System (ADS)

    Rivera Rivera, N. I.; Gill, T. E.; Bleiweiss, M. P.; Hand, J. L.; Dominguez A., M.; Ruiz, A.; Perez, A. E.; Emmert, S. P.; Lee, J. A.; Mulligan, K. R.

    2005-12-01

    Dust storms can disperse large quantities of fine aeolian sediment regionally and even globally. These extreme aerosol events frequently originate with multiple dust plumes developing simultaneously over a large region. Dust outbreaks originating in the southwestern USA and northern Mexico seasonally transport aerosols long distances across continental North America. However, dust sources in this region are not well characterized. Remote sensing data can be used to assess the frequency and magnitude of these dust events for potential impacts on climate, visibility and health-related air quality issues. We applied a technique that consists of examining visible spectral bands, as well as difference "split-window" images for far-infrared (far-IR) channels using a variety of satellite imagery (NOAA/GOES/GVAR/Imager, NOAA/POES/AVHRR and NASA/TERRA/MODIS). This technique was used to locate the origin of multiple dust plumes in the Chihuahuan Desert region of the southwestern United States and northwestern Mexico during a significant dust event that occurred on December 15, 2003. After dust sources were identified, we superimposed their locations on Landsat-7 images to assess surface features of these aeolian "hotspots," and visited many of these sites to determine the geomorphology, soil/sediment properties, and land use associated with these dust sources. Dust plumes in the Chihuahuan Desert on 15 December 2003 emanated from several land types, including saline playas, bare desert soils, disturbed/abandoned lands, and agricultural areas. In Mexico, sources included several sites along the edges of pluvial Lake Palomas near the contacts between sand sheets and lacustrine sediments, small dry lake beds (lagunas secas) and several sites in the Casas Grandes river basin in Chihuahua. In the United States, dust emission hotspots included dry, unvegetated saline playas (the White Sands near the E and SE edges of Lake Lucero, New Mexico, and the northern Salt Basin west of the

  8. Geochemical characterization of a Holocene aeolian profile in the Zhongba area (southern Tibet, China) and its paleoclimatic implications

    NASA Astrophysics Data System (ADS)

    Li, Tuoyu; Wu, Yongqiu; Du, Shisong; Huang, Wenmin; Hao, Chengzhi; Guo, Chao; Zhang, Mei; Fu, Tianyang

    2016-03-01

    The Zhongba area lies in the valley of the Maquan River in southern Tibet, where there are both strong modern aeolian activities and ancient aeolian sand sediments. A Holocene aeolian sand and paleosol profile in the Zhongba area was selected for study and termed (Zhuzhu (ZZ) profile). The chronology of the ZZ profile was established by optically stimulated luminescence (OSL) and accelerator mass spectrometry (AMS) 14C dating. Based on the grain size and geochemical elements of the ZZ profile, the geochemical characterization was analyzed, the Holocene aeolian activity processes were reconstructed in the study area, and the paleoclimatic implications were discussed. The major elements and the chemical indicators are highly correlated with different grain-sizes in the ZZ profile. The evolutionary sequence of the aeolian activities and the paleoclimate in Holocene reveal four stages: before 7.3 ka BP, the climate was warm and wet with weak winds when the sand paleosol developed; at 7.3-3.8 ka BP, the climate turned dry, with strong aeolian activities; at 3.8-0.7 ka BP, the climate became wetter and the winds weakened when the silt paleosol developed; and since 0.7 ka BP, it was cold and dry with strong aeolian activities.

  9. Selective deposition response to aeolian-fluvial sediment supply in the desert braided channel of the upper Yellow River, China

    NASA Astrophysics Data System (ADS)

    Wang, H.; Jia, X.; Li, Y.; Peng, W.

    2015-09-01

    Rivers flow across aeolian dunes and develop braided stream channels. Both aeolian and fluvial sediment supplies regulate sediment transport and deposition in such cross-dune braided rivers. Here we show a significant selective deposition in response to both aeolian and fluvial sediment supplies in the Ulan Buh desert braided channel. The Ulan Buh desert is the main coarse sediment source for this desert braided channel, and the mean percentage of the coarser (> 0.08 mm) grains on the aeolian dunes surface is 95.34 %. The lateral selective deposition process is developed by the interaction between the flows and the aeolian-fluvial sediment supplies, causing the coarser sediments (> 0.08 mm) from aeolian sand supply and bank erosion to accumulate in the channel centre and the finer fluvial sediments (< 0.08 mm) to be deposited on the bar and floodplain surfaces, forming a coarser-grained thalweg bed bounded by finer-grained floodplain surfaces. This lateral selective deposition reduces the downstream sediment transport and is a primary reason for the formation of an "above-ground" river in the braided reach of the upper Yellow River in response to aeolian and fluvial sediment supplies.

  10. Dust Avalanches

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Crater wall dust avalanches in southern Arabia Terra.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

    Image information: VIS instrument. Latitude 10.3, Longitude 24.5 East (335.5 West). 19 meter/pixel resolution.

  11. Dust particle dynamics in atmospheric dust devils

    NASA Astrophysics Data System (ADS)

    Izvekova, Yulia; Popel, Sergey

    2016-04-01

    Dust particle dynamics is modeled in the Dust Devils (DDs). DD is a strong, well-formed, and relatively long-lived whirlwind, ranging from small (half a meter wide and a few meters tall) to large (more than 100 meters wide and more than 1000 meters tall) in Earth's atmosphere. We develop methods for the description of dust particle charging in DDs, discuss the ionization processes in DDs, and model charged dust particle motion. Our conclusions are consistent with the fact that DD can lift a big amount of dust from the surface of a planet into its atmosphere. On the basis of the model we perform calculations and show that DDs are important mechanism for dust uplift in the atmospheres of Earth and Mars. Influence of DD electric field on dynamics of dust particles is investigated. It is shown that influence of the electric field on dust particles trajectories is significant near the ground. At some altitude (more then a quarter of the height of DD) influence of the electric field on dust particles trajectories is negligible. For the calculation of the dynamics of dust electric field can be approximated by effective dipole located at a half of the height of DD. This work was supported by the Russian Federation Presidential Program for State Support of Young Scientists (project no. MK-6935.2015.2).

  12. Aeolian process effects on vegetation communities in an arid grassland ecosystem.

    PubMed

    Alvarez, Lorelei J; Epstein, Howard E; Li, Junran; Okin, Gregory S

    2012-04-01

    Many arid grassland communities are changing from grass dominance to shrub dominance, but the mechanisms involved in this conversion process are not completely understood. Aeolian processes likely contribute to this conversion from grassland to shrubland. The purpose of this research is to provide information regarding how vegetation changes occur in an arid grassland as a result of aeolian sediment transport. The experimental design included three treatment blocks, each with a 25 × 50 m area where all grasses, semi-shrubs, and perennial forbs were hand removed, a 25 × 50 m control area with no manipulation of vegetation cover, and two 10 × 25 m plots immediately downwind of the grass-removal and control areas in the prevailing wind direction, 19° north of east, for measuring vegetation cover. Aeolian sediment flux, soil nutrients, and soil seed bank were monitored on each treatment area and downwind plot. Grass and shrub cover were measured on each grass-removal, control, and downwind plot along continuous line transects as well as on 5 × 10 m subplots within each downwind area over four years following grass removal. On grass-removal areas, sediment flux increased significantly, soil nutrients and seed bank were depleted, and Prosopis glandulosa shrub cover increased compared to controls. Additionally, differential changes for grass and shrub cover were observed for plots downwind of vegetation-removal and control areas. Grass cover on plots downwind of vegetation-removal areas decreased over time (2004-2007) despite above average rainfall throughout the period of observation, while grass cover increased downwind of control areas; P. glandulosa cover increased on plots downwind of vegetation-removal areas, while decreasing on plots downwind of control areas. The relationships between vegetation changes and aeolian sediment flux were significant and were best described by a logarithmic function, with decreases in grass cover and increases in shrub cover

  13. 2008 Weather and Aeolian Sand-Transport Data from the Colorado River Corridor, Grand Canyon, Arizona

    USGS Publications Warehouse

    Draut, Amy E.; Sondossi, Hoda A.; Hazel, Joseph E.; Andrews, Timothy; Fairley, Helen C.; Brown, Christopher R.; Vanaman, Karen M.

    2009-01-01

    This report presents measurements of weather parameters and aeolian (windblown) sand transport made in 2008 near selected archaeological sites in the Colorado River corridor through Grand Canyon, Ariz. The quantitative methods and data discussed here form a basis for monitoring ecosystem processes that affect archeological-site stability. Combined with forthcoming work to evaluate landscape evolution at nearby archaeological sites, these data can be used to document the relationship between physical processes, including weather and aeolian sand transport, and their effects on the physical integrity of archaeological sites. Data collected in 2008 reveal event- and seasonal-scale variations in rainfall, wind, temperature, humidity, and barometric pressure. Broad seasonal changes in aeolian sediment flux are also apparent at most study sites. The continuation of monitoring that began in 2007, and installation of equipment at several new sites in early 2008, allowed evaluation of the effects of the March 2008 high-flow experiment (HFE) on aeolian sand transport. At two of the nine sites studied, spring and summer winds reworked 2008 HFE sandbars to form new aeolian dunes, at which sand moved inland toward larger, well-established dune fields. At the other seven study sites, neither dune formation nor enhanced sand transport after the HFE were observed. At several of those sites, dominant wind directions in spring 2008 were not oriented such that much HFE sand would have moved inland; at other sites, lack of increased inland sand flux is attributable to lack of sandbar enlargement near the study sites or to inhibition of sand movement by vegetation or local topography.

  14. Solar wind magnetic field bending of Jovian dust trajectories.

    PubMed

    Zook, H A; Grün, E; Baguhl, M; Hamilton, D P; Linkert, G; Liou, J; Forsyth, R; Phillips, J L

    1996-11-29

    From September 1991 to October 1992, the cosmic dust detector on the Ulysses spacecraft recorded 11 short bursts, or streams, of dust. These dust grains emanated from the jovian system, and their trajectories were strongly affected by solar wind magnetic field forces. Analyses of the on-board measurements of these fields, and of stream approach directions, show that stream-associated dust grain masses are of the order of 10(-18) gram and dust grain velocities exceed 200 kilometers per second. These masses and velocities are, respectively, about 10(3) times less massive and 5 to 10 times faster than earlier reported. PMID:8929405

  15. The MECA Payload as a Dust Analysis Laboratory on the MSP 2001 Lander

    NASA Astrophysics Data System (ADS)

    Marshall, J.; Anderson, M.; Buehler, M.; Frant, M.; Fuerstenau, S.; Hecht, M.; Keller, U.; Markiewicz, W.; Meloy, T.; Pike, T.

    1999-09-01

    planetology perspective, there are many enigmatic issues relating to dust and the aeolian regime in general. MECA will be able to address many questions in this area. For example, if MECA determines a particular particle size distribution (size and sorting values), it will be possible to make inferences about the origin of the dust - - is it all aeolian, or a more primitive residue of weathering, volcanic emissions, and meteoritic gardening? Trenching with the Lander/MECA robot arm will enable local stratigraphy to be determined in terms of depositional rates, amounts and cyclicity in dust storms and/or local aeolian transport. Grain shape will betray the origin of the dust fragments as being the product of recent or ancient weathering, or the comminution products of aeolian transport --the dust-silt ratio might be a measure of aeolian comminution energy. Additional information is contained in the original.

  16. The MECA Payload as a Dust Analysis Laboratory on the MSP 2001 Lander

    NASA Technical Reports Server (NTRS)

    Marshall, J.; Anderson, M.; Buehler, M.; Frant, M.; Fuerstenau, S.; Hecht, M.; Keller, U.; Markiewicz, W.; Meloy, T.; Pike, T.

    1999-01-01

    planetology perspective, there are many enigmatic issues relating to dust and the aeolian regime in general. MECA will be able to address many questions in this area. For example, if MECA determines a particular particle size distribution (size and sorting values), it will be possible to make inferences about the origin of the dust - - is it all aeolian, or a more primitive residue of weathering, volcanic emissions, and meteoritic gardening? Trenching with the Lander/MECA robot arm will enable local stratigraphy to be determined in terms of depositional rates, amounts and cyclicity in dust storms and/or local aeolian transport. Grain shape will betray the origin of the dust fragments as being the product of recent or ancient weathering, or the comminution products of aeolian transport --the dust-silt ratio might be a measure of aeolian comminution energy. Additional information is contained in the original.

  17. Surface Dust Redistribution on Mars as Observed by the Mars Global Surveyor

    NASA Technical Reports Server (NTRS)

    Szwast, M. A.; Richardson, M. I.; Vasavada, A. R.

    2005-01-01

    The global redistribution of dust by the atmosphere is geologically and climatologically important. Dust deposition and removal at the surface represents ongoing sedimentary geology: a vestige of aeolian processes responsible for the concentration of vast dustsheets and potentially for ancient layered units at various locations on Mars. The varying amount of dust on the surface has also long been hypothesized as a factor in determining whether regional or global dust storms occur in a given year. Indeed, the atmosphere has a very short, sub-seasonal time-scale (or memory) and as such, any inter-annual variability in the climate system that is not simply ascribable to stochastic processes, must involve changing conditions on the surface. An excellent, multi-year dataset is provided by the Mars Global Surveyor (MGS) Thermal Emission Spectrometer (TES) and the Mars Orbiter Camera Wide Angle imager (MOC-WA). This dataset allows investigation into the degree to which surface dust deposits on Mars really change: over decadal time scales, over the course of the annual cycle, and as a result of global and regional dust storms. The MGS mapping orbit data set extends over almost 3 Martian years at the time of writing. These data sets include one global dust storm and smaller regional storms (one in the first TES mapping year and two in the third).

  18. Monitoring Saharan dust from source to sink: from Iwik [Mauritania] to Statia [Caribbean

    NASA Astrophysics Data System (ADS)

    van Hateren, Hans; van der Does, Michelle; Friese, Carmen; Korte, Laura; Munday, Chris; Stuut, Jan-Berend

    2015-04-01

    The particle-size distribution and composition of mineral dust is often used as a tool to reconstruct palaeo-environmental conditions in the source(s) of the dust. In on-land (loess), lacustrine, and marine archives, the size of dust deposits is considered a proxy for paleo-wind intensity. However, next to wind strength, the particle size of aeolian deposits is also influenced by various other parameters such as source-to-sink distance, altitude at which the particles have been transported, and various environmental conditions in the sources of the dust. To verify if we can quantify a relationship between the size and composition of mineral dust particles and prevailing environmental conditions, we study "modern" dust. Within three ongoing projects, funded by the Dutch NWO, German DFG, and the ERC, we are studying dust collected on land in Mauritania (Iwik, in the Parc National de Banc d'Arguin, sampling on a monthly resolution) with an array of marine sediment-traps (five moorings at 12°N across the Atlantic Ocean with two sediment traps each between 23° and 57°W, sampling on a 2-weekly resolution) as well as automated mineral-dust collection at sea (on dust-collecting buoys at 12°N/38°W and 12°N/49°W, sampling on a 2-weekly resolution), and finally with a high-volume dust collector on St Eustatius (17°N/63°W, sampling on a 2-weekly resolution). Here we compare initial results of the particle-size distributions of the "minimally-disturbed" fraction of the on-land dust collectors with the terrigenous sediment fraction from the sediment traps, and discuss temporal and spatial trends.

  19. Soil heterogeneity of an East and West facing ridge above timberline due to differences in snow and aeolian deposition

    NASA Astrophysics Data System (ADS)

    Traver, E.

    2015-12-01

    Hans Jenny's soil forming factors—time, parent material, climate, topography, and organisms—represent the major components of his system to describe and quantify soil development. In almost all situations, it is difficult to hold even one of these factors constant while focusing on another factor; however, in our study site—the East and West side of a narrow North-South running ridge, above timberline in SE Wyoming—we can hold three factors nearly constant (time, parent material, and climate) and focus on how topography, in particular, has influenced the soil differences on the two sides. The East side is the leeside of prevailing and strong westerly winds and receives a large snow pack while the West is consistently snow-free during winter creating a very different moisture and soil temperature regime. The East receives aeolian dust deposition while the West loses surface material from wind scour. A standard chemical and physical analysis found that while the two sides are nearly identical textually, with a similar pH and low electrical conductivity, the East side is richer in minerals. During the short growing season, soil moisture results show that the West side is holding more water than the East side; however, the East side has a higher percentage of organic matter and is more shrub and forb rich. An isotope analysis shows that the C:N ratios are very similar on the two sides. Microbial biomass and functional groups will be analyzed in the soil samples as well as a seismic study conducted to quantity depth of soil to bedrock. Using all these results will help quantify the differences on the two sides of this narrow ridge and add to our understanding of fine-scale soil heterogeneity and its relationship to watershed hydrology.

  20. Mass Spectrometry of Contemporary Interstellar Dust by the Cassini Space Craft

    NASA Astrophysics Data System (ADS)

    Postberg, F.; Fiege, K.; Altobelli, N.; Srama, R.; Trieloff, M.

    2014-09-01

    Cassini’s dust detector (CDA) recorded over 30 mass spectra of individual interstellar dust grains crossing the solar system. The composition of all grains is surprisingly similar and is depleted in organics if compared with astronomical observations.

  1. Ocean biogeochemistry exhibits contrasting responses to a large scale reduction in dust deposition

    NASA Astrophysics Data System (ADS)

    Tagliabue, A.; Bopp, L.; Aumont, O.

    2008-01-01

    Dust deposition of iron is thought to be an important control on ocean biogeochemistry and air-sea CO2 exchange. In this study, we examine the impact of a large scale, yet climatically realistic, reduction in the aeolian Fe input during a 240 year transient simulation. In contrast to previous studies, we find that the ocean biogeochemical cycles of carbon and nitrogen are relatively insensitive (globally) to a 60% reduction in Fe input from dust. Net primary productivity (NPP) is reduced in the Fe limited regions, but the excess macronutrients that result are able to fuel additional NPP elsewhere. Overall, NPP and air-sea CO2 exchange are only reduced by around 3% between 1860 and 2100. While the nitrogen cycle is perturbed more significantly (by ~15%), reduced N2 fixation is balanced by a concomitant decline in denitrification. Feedbacks between N2 fixation and denitrification are controlled by variability in surface utilization of inorganic nitrogen and subsurface oxygen consumption, as well as the direct influence of Fe on N2 fixation. Overall, there is relatively little impact of reduced aeolian Fe input (<4%) on cumulative CO2 fluxes over 240 years. The lower sensitivity of our model to changes in dust input is primarily due to the more detailed representation of the continental shelf Fe, which was absent in previous models.

  2. Ocean biogeochemistry exhibits contrasting responses to a large scale reduction in dust deposition

    NASA Astrophysics Data System (ADS)

    Tagliabue, A.; Bopp, L.; Aumont, O.

    2007-08-01

    Dust deposition of iron is thought to be an important control on ocean biogeochemistry and air-sea CO2 exchange. In this study, we examine the impact of a large scale, yet climatically realistic, reduction in the aeolian Fe input during a 240 year transient simulation. In contrast to previous studies, we find that the ocean biogeochemical cycles of carbon and nitrogen are relatively insensitive to a 60% reduction in Fe input from dust. Net primary productivity (NPP) is reduced in the Fe limited regions, but the excess macronutrients that result are able to fuel additional NPP elsewhere. Overall, NPP and air-sea CO2 exchange are only reduced by around 3% between 1860 and 2100. While the nitrogen cycle is perturbed more significantly (by ~15%), reduced N2 fixation is balanced by a concomitant decline in denitrification. Feedbacks between N2 fixation and denitrification are controlled by variability in surface utilization of inorganic nitrogen and subsurface oxygen consumption, as well as the direct influence of Fe on N2 fixation. Overall, there is relatively little impact of reduced aeolian Fe input (<4%) on cumulative CO2 fluxes over 240 years. The lower sensitivity of our model to changes in dust input is primarily due to the more detailed representation of the continental shelf Fe, which was absent in previous models.

  3. Impact of desert dust on the biogeochemistry of phosphorus in terrestrial ecosystems

    NASA Astrophysics Data System (ADS)

    Okin, Gregory S.; Mahowald, Natalie; Chadwick, Oliver A.; Artaxo, Paulo

    2004-06-01

    Leaching, biomass removal, and partitioning of phosphorus (P) into reservoirs not available to plants can limit the long-term productivity of terrestrial ecosystems. We evaluate the importance of atmospheric P inputs to the world's soils by estimating the total soil P turnover time with respect to dustborne P additions. Estimated turnover times range from ˜104 to ˜107 years. Our estimates provide a unique perspective on the importance and patterns of aeolian deposition to terrestrial landscapes. Dust source regions are areas of intense soil P cycling on large scales, but are too water-limited for this rapid cycling to have a major influence on ecosystem dynamics. By contrast, semiarid desert margins receive significant aeolian P from neighboring deserts and are likely influenced by dustborne P additions for the long-term maintenance of productivity. This is particularly true for the semiarid steppes of Africa and Eurasia. The prevalence of large dust sources in Africa and Eurasia indicates that these areas may generally be more influenced by dustborne P additions than soils in the Americas. Significant western hemisphere exceptions to this pattern occur on very old landscapes, such as the forests of the southeastern United States and the Amazon Basin. The Amazon Basin is highly dependent on aeolian deposition for the maintenance of long-term productivity. Dust deposition to terrestrial environments has not been constant with time. Variability in past P deposition related to geologically recent climate change may provide the strongest controls on present and future soil P in the Amazon and elsewhere.

  4. Twelve thousand years of dust: the Holocene global dust cycle constrained by natural archives

    NASA Astrophysics Data System (ADS)

    Albani, S.; Mahowald, N. M.; Winckler, G.; Anderson, R. F.; Bradtmiller, L. I.; Delmonte, B.; François, R.; Goman, M.; Heavens, N. G.; Hesse, P. P.; Hovan, S. A.; Kang, S. G.; Kohfeld, K. E.; Lu, H.; Maggi, V.; Mason, J. A.; Mayewski, P. A.; McGee, D.; Miao, X.; Otto-Bliesner, B. L.; Perry, A. T.; Pourmand, A.; Roberts, H. M.; Rosenbloom, N.; Stevens, T.; Sun, J.

    2015-06-01

    Mineral dust plays an important role in the climate system by interacting with radiation, clouds, and biogeochemical cycles. In addition, natural archives show that the dust cycle experienced variability in the past in response to global and local climate change. The compilation of the DIRTMAP (Dust Indicators and Records from Terrestrial and MArine Palaeoenvironments) paleodust data sets in the last 2 decades provided a benchmark for paleoclimate models that include the dust cycle, following a time slice approach. We propose an innovative framework to organize a paleodust data set that builds on the positive experience of DIRTMAP and takes into account new scientific challenges by providing a concise and accessible data set of temporally resolved records of dust mass accumulation rates and particle grain size distributions. We consider data from ice cores, marine sediments, loess-paleosol sequences, lake sediments, and peat bogs for this compilation, with a temporal focus on the Holocene period. This global compilation allows the investigation of the potential, uncertainties, and confidence level of dust mass accumulation rate reconstructions and highlights the importance of dust particle size information for accurate and quantitative reconstructions of the dust cycle. After applying criteria that help to establish that the data considered represent changes in dust deposition, 45 paleodust records have been identified, with the highest density of dust deposition data occurring in the North Atlantic region. Although the temporal evolution of dust in the North Atlantic appears consistent across several cores and suggests that minimum dust fluxes are likely observed during the early to mid-Holocene period (6000-8000 years ago), the magnitude of dust fluxes in these observations is not fully consistent, suggesting that more work needs to be done to synthesize data sets for the Holocene. Based on the data compilation, we used the Community Earth System Model to

  5. Long-term dust climatology in the western United States

    NASA Astrophysics Data System (ADS)

    Tong, D.; Lei, H.; Wang, J. X.; Lee, P.

    2013-12-01

    Dust activity is an important indicator to regional climate change. The Dust Bowl in the 1930s was the largest natural catastrophe in the North America history, caused by extended drought and poor land management. Although the severity and duration of the 1930s drought was exceptional, reconstructed paleo-climatic records show that the central U.S. plains have experienced severe droughts about once or twice a century over the past 400 years. Dust record is hence an integral component of the national climate assessment (NCA). This work presents our recent efforts to develop a climate-quality indicator of local windblown dust storms in the U.S. For the arid and semi-arid regions of the western United States, we have developed a novel approach to identify local windblown dust events through routine ambient aerosol monitoring (Tong et al., 2012). This work uses the dust identification algorithm to develop a dust storm dataset (dust indicator), and rely on satellite dust detection and model dust prediction as independent data sources to test, cross-check and validate the dust indicator. This work will extend our research capabilities to contribute developing new climate indicators that are especially aimed at needs of local environmental managers in the Southwestern communities.

  6. Long-term dust climatology in the western United States

    NASA Astrophysics Data System (ADS)

    Tong, D.; Lee, P.; Lei, H.; Wang, J. X. L.

    2014-12-01

    Dust activity is an important indicator to regional climate change. The Dust Bowl in the 1930s was the largest natural catastrophe in the North America history, caused by extended drought and poor land management. Although the severity and duration of the 1930s drought was exceptional, reconstructed paleo-climatic records show that the central U.S. plains have experienced severe droughts about once or twice a century over the past 400 years. Dust record is hence an integral component of the national climate assessment (NCA). This work presents our recent efforts to develop a climate-quality indicator of local windblown dust storms in the U.S. For the arid and semi-arid regions of the western United States, we have developed a novel approach to identify local windblown dust events through routine ambient aerosol monitoring (Tong et al., 2012). This work uses the dust identification algorithm to develop a dust storm dataset (dust indicator), and rely on satellite dust detection and model dust prediction as independent data sources to test, cross-check and validate the dust indicator. This work will extend our research capabilities to contribute developing new climate indicators that are especially aimed at needs of local environmental managers in the Southwestern communities.

  7. Lead atmospheric deposition rates and isotopic trends in Asian dust during the last 9.5 kyr recorded in an ombrotrophic peat bog on the eastern Qinghai-Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Ferrat, Marion; Weiss, Dominik J.; Dong, Shuofei; Large, David J.; Spiro, Baruch; Sun, Youbin; Gallagher, Kerry

    2012-04-01

    A full understanding of the atmospheric Pb cycle in Asia during the Holocene is key to palaeoclimate studies of past atmospheric circulation patterns, as well as to assess the impact of increasing industrial activities in this region. However, long-term records of atmospheric Pb isotopic trends in Asia are still sparse. Consequently, we study changes in the concentrations, fluxes and isotopic signature of deposited Pb contained in a 14C-dated peat core from the eastern Qinghai-Tibetan Plateau, dating back to 9.5 kyr BP, and present the first peat record of the changing isotopic composition of atmospheric Pb in dust in Asia during this time. Lead concentrations and fluxes vary between 2.96-21.58 μg g-1 and 0.06-3.52 mg m-2 y-1, respectively, with an average Pb baseline of 6.80 ± 4.18 μg g-1. These values agree with other Pb studies of lake and peat archives in China but are one order of magnitude larger than early and mid-Holocene values measured in Europe. Lead isotopic variability throughout the core is small, varying between 206Pb/207Pb = 1.190-1.197, 206Pb/204Pb = 18.648-18.786, 207Pb/204Pb = 15.666-15.694 and 208Pb/204Pb = 38.890-39.090. The application of Bayesian trans-dimensional changepoint modelling to the Pb dataset enabled the identification of eight significant changes in the isotopic composition of the deposited Pb. Such changes mark different phases of atmospheric Pb deposition, and hence variations in atmospheric circulation patterns and environmental conditions. Temporal variations in the potential natural and/or anthropogenic Pb sources are assessed based on the 206Pb, 207Pb, 208Pb and 204Pb isotopic composition and the 1/[Pb] ratio of the peat samples. Our results suggest that Pb deposition throughout the Holocene was governed by local deposition and long-range input from natural dust sources in northwestern (Taklamakan desert and Qaidam basin) and northern China (Badain Jaran and Tengger deserts). Input from the northern sources seems to have

  8. Temporal variations of mineral dust, biogenic tracers, and anthropogenic species during the past two centuries from Belukha ice core, Siberian Altai - article no. D05309

    SciTech Connect

    Olivier, S.; Blaser, C.; Brutsch, S.; Frolova, N.; Gaggeler, H.W.; Henderson, K.A.; Palmer, A.S.; Papina, T.; Schwikowski, M.

    2006-03-07

    In July 2001, a 140 m long ice core was recovered from the Belukha glacier (49 degrees 48'26''N, 86 degrees 34'43''E, 4062 m a.s.l.) in the Siberian Altai. The ion chemistry of the upper 86 m, covering the last two centuries, is characterized by biogenic emissions (ammonium and formate), aeolian dust (calcium, magnesium, chloride, and sodium) and anthropogenic species (sulfate, nitrate, and ammonium). Particularly high ammonium and formate concentrations indicate pronounced emissions from Siberian forests. The inferred fire frequency does not show a long-term trend but distinct periods of enhanced activity. Sulfate has the highest industrial to preindustrial ratio and an anthropogenic contribution of more than 80%. Variations in this record reflect sulfur dioxide emissions in Siberia and Kazakhstan. Sulfate concentrations remained low until 1950, then sharply increased and peaked in the 1970s. The decrease in the 1980s is attributed to the economic, political, and social crises and to the replacement of coal with gas. Rising nitrate concentrations since 1960 reflect traffic growth and enhanced fertilizer application. Increasing ammonium concentrations since the 1950s are attributable to population inflow in southern Siberia with the associated enhancement of agricultural activity. A nitrate peak of short duration in 1908 is thought to be the atmospheric signature from the Tunguska event on 30 June 1908.

  9. Aeolian Dune Deformation in a Multi-Directional Wind Regime, White Sands Dune Field, New Mexico

    NASA Astrophysics Data System (ADS)

    Pedersen, A.; Kocurek, G.

    2013-12-01

    Aeolian dunes commonly exist in a multi-directional wind regime. With each constructive wind event, dunes both migrate and deform as a function of the incidence angle of the primary wind to the local brinkline orientation. Can dune shape after many wind events be predicted from the resultant of these wind events? This question was addressed for sinuous crescentic dunes at the White Sands Dune Field, New Mexico, using: (1) a record of wind events from nearby Holloman AFB, and (2) a time-series of LiDAR-derived digital elevation models (DEMs) in which changes in dune shape can be accurately measured. From June 2007 to June 2010, 1,590 wind events occurred in which wind velocity was above the threshold of 18.66 m/s. Based upon the sand-transporting capacity of each wind event, the rose diagram for the overall wind regime shows three modes: (1) a dominant mode from the SW that occurred throughout the year but was most common during the spring, (2) a secondary mode from the N-NE during winter during the passage of frontal weather systems during the summer, and (3) a tertiary mode from the S-SE that occurred primarily during the summer months. From brinkline tracing and difference maps made from DEMs for June 2007, June 2008, January 2009, September 2009, and June 2010, the impact of each component of the wind regime upon dune morphology is evident. Winds from the SW cause dune migration to the NE, and dune crestlines are oriented nearly perpendicular to this wind direction. N-NE winds cause along-crest crabbing of dune sinuosity, accompanied by scour along the northern flank of convex-downwind lee-face segments. S-SE winds cause local crestal reversal and scour of the lee face. Idealized dune cross-strata can be constructed based upon the impact of each wind event. However, beginning with an initial dune shape, subsequent dune shapes in the DEM time-series cannot be predicted using the resultant for the period and its incidence angle with the initial brinkline

  10. Middle Pleistocene magnetostratigraphy and susceptibility stratigraphy: data from a carbonate aeolian system, Mallorca, Western Mediterranean

    NASA Astrophysics Data System (ADS)

    Nielsen, K. A.; Clemmensen, L. B.; Fornós, J. J.

    2004-09-01

    This study shows that successions of Pleistocene carbonate aeolian deposits can be placed successfully in a geochronologic framework using magnetostratigraphic and susceptibility stratigraphic analysis supplemented by luminescence dating, studies of wave-cut platforms, and biostratigraphic evidence. The investigated aeolian system covers a significant part of southernmost Mallorca and is exposed in impressive coastal cliff sections. At the study site at Els Bancals the aeolian system has a maximum thickness of 16 m and is composed of alternating dark red colluvial deposits and greyish red aeolian dune and sand-sheet deposits forming seven cyclostratigraphic units. Each cyclostratigraphic unit represents landscape stabilisation, colluviation, and soil formation followed by dunefield development, when marine carbonate sand was transported far inland by westerly or north-westerly winds. The aeolian system is located on top of a wave-cut marine platform 12-14 m a.s.l. This platform probably formed during a sea-level highstand in Marine Isotope Stage (MIS) 11 (427-364 ka), and renewed marine activity probably later in MIS 11 is indicated by the formation of beach deposits. Two sections at Els Bancals were sampled for a paleomagnetic study; additional samples were taken to detect variations in magnetic susceptibility (MS). The characteristic remanent magnetisation has been recovered for the most part of the succession in spite of diagenetic overprinting. There is evidence for two probably three reversal polarity excursions, possible connected to the Levantine, CR1 and CR0/Biwa III episodes. If this correlation is correct, the sampled succession represents a time interval in the Middle Pleistocene between ca 410 and ca 260 ka. This age estimate is supported by the MS study and by luminescence dates of 333±70 ka (aeolianite from lower part of the succession) and 275±23 ka (aeolianite from the top of the succession). The nature of the succession suggests deposition during

  11. The Significant Roles of Landscape Pattern and Spatial Scale in Assessing Aeolian Desertification

    NASA Astrophysics Data System (ADS)

    Kang, W.; Kang, S.

    2015-12-01

    One of research focus in combating desertification is monitoring and assessing aeolian desertification by temporal satellite remote sensing imageries. Landscape heterogeneity hampers robust interpretation from the satellite imagery on the status and process of aoelian desertification in arid regions, for which scale effect on satellite-imagery interpretation must be investigated. In this study, area and degree of aeolian desertification were assessed at different spatial scales from 30m to 1km by using TM and Landsat8 imageries, respectively. Then, landscape pattern index was utilized to explain effect of spatial resolution on the satellite-based assessment of aeolian desertification in the middle of Mu Us and the west of Otindag Sandy Lands in Inner Mongolia of China. Our results indicate: (1) The middle of Mu Us was rehabilitated from 2000 to 2014 by reduction of desertified area from 12,861 km2 to 11,700 km2. Whereas, the desertified area of the west of Otindag fluctuated but rebounded during the last five years; (2) scale effects on the area and degree of desertified land were not significant, along the spatial resolution, the desertified area fluctuated from12,962km2 to 12,861km2 for Mu Us hinterland and from 7,752km2to 7,700km2 for Otindag west, which corresponds 0.78% and 0.67 % of relative variations, respectively. The aeolian desertification degree index(ADI) fluctuated from 0.36 to 0.35 for Mu Us hinterland and from 0.17 to 0.16 for Otindag west, which corresponds 2.78% and 5.88 % of relative variations, respectively. (3) scale effects on landscape pattern indices were significant, particular in landscape fragment; the correlation of spatial resolution and landscape fragment are positive(RMu Us2=0.76-0.77, ROtindag2=0.73-0.78). It was found substantial uncertainty in satellite-based assessment on aeolian desertification in Mu Us and Otindag Sandy Lands and the relevance of the uncertainty with the landscape pattern indices. Our study proposes more

  12. 2009 weather and aeolian sand-transport data from the Colorado River corridor, Grand Canyon, Arizona

    USGS Publications Warehouse

    Draut, Amy E.; Sondossi, Hoda A.; Dealy, Timothy P.; Hazel, Joseph E.; Fairley, Helen C.; Brown, Christopher R.

    2010-01-01

    This report presents measurements of weather parameters and aeolian sand transport made in 2009 near selected archeological sites in the Colorado River corridor through Grand Canyon, Ariz. The quantitative methods and data discussed here form a basis for monitoring ecosystem processes that affect archeological-site stability. Combined with forthcoming work to evaluate landscape evolution at nearby archeological sites, these data can be used to document the relation between physical processes, including weather and aeolian sand transport, and their effects on the physical integrity of archeological sites. Data collected in 2009 reveal event- and seasonal-scale variations in rainfall, wind, temperature, humidity, and barometric pressure. Broad seasonal changes in aeolian sediment flux are also apparent at most study sites. Differences in weather patterns between 2008 and 2009 included an earlier spring windy season, greater spring precipitation even though 2009 annual rainfall totals were in general substantially lower than in 2008, and earlier onset of the reduced diurnal barometric-pressure fluctuations commonly associated with summer monsoon conditions. Weather patterns in middle to late 2009 were apparently affected by a transition of the ENSO cycle from a neutral phase to the El Ni?o phase. The continuation of monitoring that began in 2007, and installation of additional equipment at several new sites in early 2008, allowed evaluation of the effects of the March 2008 high-flow experiment (HFE) on aeolian sand transport. As reported earlier, at 2 of the 9 sites studied, spring and summer winds in 2008 reworked the HFE sandbars to form new aeolian dunes, where sand moved inland toward larger, well-established dune fields. Observations in 2009 showed that farther inland migration of the dune at one of those two sites is likely inhibited by vegetation. At the other location, the new aeolian dune form was found to have moved 10 m inland toward older, well

  13. Braidplain, floodplain and playa lake, alluvial-fan, aeolian and palaeosol facies composing a diversified lithogenetical sequence in the permian and triassic of South Devon (England)

    NASA Astrophysics Data System (ADS)

    Mader, Detlef

    The Permian and Triassic of South Devon (England) are a continental red bed sequence of very diversified lithogenetical composition. Within the thick series, the distribution of the main depositional environments being fluvial braidplain, fluvial floodplain and playa lake, alluvial fan, aeolian dune and calcrete palaeosol changes repeatedly in both horizontal and vertical direction. Significant sedimentary milieus such as aeolian dunes and calcrete palaeosols occur repeatedly within the succession, but are also lacking in several parts of the sequence. Fluvial braidplain deposits comprise conglomerates, sandstones, intraformational reworking horizons and mudstones and originate in channels and overbank plains of a braided river system. Conglomerates and sandstones are formed by migration of bars and spreading out of sheets during infilling of streams and aggradation of flats. Gravel is often enriched as lag pockets or veneers within steeper scour holes and kolk pots or on the plane floor of the watercourse. Finer-grained sandstones and mudstones are laid down by suspension settling in stagnant water bodies such as small lakes in the overbank area and residual pools in interbar depressions during low-stage or waning-flow in active channels or in abandoned streams. Spectacular bioturbation features in some sandstones with both horizontal tubes and vertical burrows testify to the colonization of the sediments at the bottom of the rivers with declining discharge and transport capacity. Intraformational reworking horizons with ghost-like remnants of degraded sandstones, mudstones and pedogenic carbonates document partially severe condensation of the sequence by removal of some facies elements from the depositional record. The occasionally occurring gravel-bearing mudstones or silty-clayey sandstones represent products of high-energy water surges overspilling the channel banks and transporting sandy and gravelly bed-load in limited amounts beyond the levee wall. The

  14. Fate and Transport of Dust-borne Trace Metals and Solutes during Snowmelt Runoff in the Provo River, Utah

    NASA Astrophysics Data System (ADS)

    Carling, G. T.; Dastrup, D.; Fernandez, D. P.; Tingey, D. G.; Aanderud, Z.; Nelson, S.

    2015-12-01

    Aeolian dust is an important physical and chemical flux to mountain snowpack, with potentially significant contributions of trace metals and solutes to mountain streams during snowmelt. However, it is difficult to differentiate element contributions from dust relative to inputs from soil erosion and weathering. Sr isotopes show promise as a tracer of the soluble fraction of dust from snowpack to snowmelt runoff. We analyzed 87Sr/86Sr ratios, Sr and trace metal concentrations, and other parameters in bulk snowpack (wet and dry deposition), dust, and snowmelt runoff in the upper Provo River watershed in the Uinta Mountains (Utah, USA) over three years (2013-2015). In 2014 snowpack and dust samples had the same 87Sr/86Sr ratio (~0.7110), indicating that dust was responsible for the majority of Sr deposition to snowpack. Preliminary results using a two end-member mixing model (end-members of bulk snowpack and river baseflow) indicate that dust contributed up to 40% of Sr riverine load during peak runoff in 2014. In contrast, in 2013 there were no visible dust layers in the snowpack and mixing models indicate a different Sr source (e.g., soil water). Analyses are still underway on the 2015 samples. Sequential leaching experiments on dust samples suggest that Sr is likely associated with the highly soluble carbonate mineral fraction in dust, but other elements such as Cr, Cu, Pb, and U are associated with the relatively insoluble organic fraction. Additional work is underway to investigate transport of the less soluble dust-borne metals during snowmelt by complexation with organic matter or other mechanisms. These results suggest that dust on snowpack is an important but variable source of soluble elements during snowmelt, and that dust should be considered when investigating solute loads in mountain streams.

  15. Allergies, asthma, and dust

    MedlinePlus

    ... much dust. Dust particles collect in fabrics and carpets. If you can, get rid of fabric or ... are covered in cloth. Replace wall-to-wall carpet with wood or other hard flooring. Since mattresses, ...

  16. The National Aeolian Detritus Project, A Student-controlled, Standards-based Research Opportunity for Middle and Hight School Students

    NASA Astrophysics Data System (ADS)

    Sammons, J. I.; Murray, D. D.; Reid, J. B.

    2001-12-01

    Schools across the United States are adopting Standards-based philosophies and practices at a quickening pace. Two of the biggest challenges in this transition are the integration of concepts and the development of meaningful evaluation of student progress. The National Aeolian Detritus Project is a collaboration among Jamestown School, the University of Rhode Island, Hampshire College, the Rhode Island Space Grant Consortium at Brown University and the Rhode Island Nuclear Science Center. This Project provides students with an opportunity to integrate and enhance previous elements of instruction and allows them decision-making control over the direction of an extended research investigation. This project also provides opportunities for undergraduate community service development through University - Local School collaboration and mentoring. Students first collect Aeolian Detritus, that is, randomly deposited airborne particulate matter (APM) by deploying flat sheet collectors. Retained APM is removed from the collectors with repulpable tape and concentrated by vacuum filtration. APM is initially identified by simple light microscopy, solubility, density, and magnetic response. More advanced identification includes ICP and Neutron Activation. With assistance from collaborating universities, students craft research questions based on these initial samples and develop investigation designs. Sample research questions include: 1) Can insect infestations or possible defoliation events be predicted by identification of insect bodies, parts, and excrement? 2) What information can we collect about micrometeorites when typed, analyzed, and compared to NASA comet track data? 3) Can the distribution of flora be confirmed or modified based on pollen grain collection and mapping? 4) Can the distribution of mineral particulate matter be mapped by collection and comparison with wind patterns over known geologic features? Schools correlate collection data with National Weather

  17. Saharan dust and Florida red tides: The cyanophyte connection

    NASA Astrophysics Data System (ADS)

    Walsh, John J.; Steidinger, Karen A.

    2001-06-01

    Prediction of the consequences of harmful algal blooms for humans and other vertebrates is constrained by an inadequate understanding of the factors that promote their initiation. A simple exponential growth model of net production is used for analysis of four time series at different sampling intervals over ˜40 years of red tide strandings, associated fish kills, and concomitant dust loadings on the West Florida shelf. At least large summer blooms of a toxic dinoflagellate Gymnodinium breve appear to be primed regularly by an aeolian supply of nutrients. Wet deposition of Saharan mineral aerosols may alleviate iron limitation of diazotrophic cyanophytes, which in turn fuel the nitrogen economy of red tides in the eastern Gulf of Mexico. Vagaries of the wind-induced circulation and of selective grazing pressure on phytoplankton competitors within phosphorus replete coastal waters then determine each year the residence times for exposure of G. breve-mediated neurotoxins to fish, manatees, and humans along the southeastern United States.

  18. Geochemical and microbiological fingerprinting of airborne dust that fell in Canberra, Australia, in October 2002

    NASA Astrophysics Data System (ADS)

    de Deckker, Patrick; Abed, Raeid M. M.; de Beer, Dirk; Hinrichs, Kai-Uwe; O'Loingsigh, Tadhg; Schefuß, Enno; Stuut, Jan-Berend W.; Tapper, Nigel J.; van der Kaars, Sander

    2008-12-01

    During the night of 22-23 October 2002, a large amount of airborne dust fell with rain over Canberra, located some 200 km from Australia's east coast, and at an average altitude of 650 m. It is estimated that during that night about 6 g m-2 of aeolian dust fell. We have conducted a vast number of analyses to "fingerprint" some of the dust and used the following techniques: grain size analysis; scanning electron microscope imagery; major, trace, and rare earth elemental, plus Sr and Nd isotopic analyses; organic compound analyses with respective compound-specific isotope analyses; pollen extraction to identify the vegetation sources; and molecular cloning of 16S rRNA genes in order to identify dust bacterial composition. DNA analyses show that most obtained 16S rRNA sequences belong mainly to three groups: Proteobacteria (25%), Bacteriodetes (23%), and gram-positive bacteria (23%). In addition, we investigated the meteorological conditions that led to the dust mobilization and transport using model and satellite data. Grain sizes of the mineral dust show a bimodal distribution typical of proximal dust, rather than what is found over oceans, and the bimodal aspect of size distribution confirms wet deposition by rain droplets. The inorganic geochemistry points to a source along/near the Darling River in NW New South Wales, a region that is characteristically semiarid, and both the organic chemistry and palynoflora of the dust confirm the location of this source area. Meteorological reconstructions of the event again clearly identify the area near Bourke-Cobar as being the source of the dust. This study paves the way for determining the export of Australian airborne dust both in the oceans and other continents.

  19. Humidity control of particle emissions in aeolian systems

    NASA Astrophysics Data System (ADS)

    McKenna Neuman, Cheryl; Sanderson, Steven

    2008-06-01

    Humidity is an important control of the wind speed required to entrain particles into an air flow and is well known to vary on a global scale, as do dust emissions. This paper reports on wind tunnel experiments which quantify this control through placing a polymer capacitance sensor immediately at the bed surface. The sensor measured changes in the humidity (RH) of the pore air in real time. RH was varied between 15% and 80% and the critical wind speed determined for the release of particles to the air stream. The results strongly support earlier suggestions that fine particles are most affected in relatively dry atmospheres, particularly those which are tightly packed. An analytical model is proposed to describe this relationship which depends on determination of the matric potential from the Kelvin equation. The total contact area between particle asperities adjoined by pendular rings is represented as a power function of the number of layers of adsorbed water. The value of the exponent appears to be governed by the surface roughness of the particles and their packing arrangement. Parallel developments in colloid interface science and atomic force microscopy, relevant to industrial and pharmaceutical applications, support these conclusions in principle and will likely have an important bearing on future progress in parameterization of the proposed model.

  20. Niamey Dust Observations

    DOE Data Explorer

    Flynn, Connor

    2008-10-01

    Niamey aerosol are composed of two main components: dust due to the proximity of the Sahara Desert, and soot from local and regional biomass burning. The purpose of this data product is to identify when the local conditions are dominated by the dust component so that the properties of the dust events can be further studied.

  1. Middle East Dust

    Atmospheric Science Data Center

    2013-04-16

    ... (nadir) camera. Here only some of the dust over eastern Syria and southeastern Turkey can be discerned. The dust is much more obvious ... October 18, 2002 - A large dust plume extends across Syria and Turkey. project:  MISR category:  ...

  2. China Dust and Sand

    Atmospheric Science Data Center

    2013-04-16

    ... article title:  Dust and Sand Sweep Over Northeast China     View Larger Image ... these views of the dust and sand that swept over northeast China on March 10, 2004. Information on the height of the dust and an ...

  3. Dust in the Universe

    ERIC Educational Resources Information Center

    Hemenway, Mary Kay; Armosky, Brad J.

    2004-01-01

    Space is seeming less and less like empty space as new discoveries and reexaminations fill in the gaps. And, ingenuity and technology, like the Spitzer Space Telescope, is allowing examination of the far reaches of the Milky Way and beyond. Even dust is getting its due, but not the dust everyone is familiar with. People seldom consider the dust in…

  4. Vegetation and substrate on aeolian landscapes in the Colorado River corridor, Cataract Canyon, Utah

    USGS Publications Warehouse

    Draut, Amy E.; Gillette, Elizabeth R.

    2010-01-01

    Vegetation and substrate data presented in this report characterize ground cover on aeolian landscapes of the Colorado River corridor through Cataract Canyon, Utah, in Canyonlands National Park. The 27-km-long Cataract Canyon reach has undergone less anthropogenic alteration than other reaches of the mainstem Colorado River. Characterizing ecosystem parameters there provides a basis against which to evaluate future changes, such as those that could result from the further spread of nonnative plant species or increased visitor use. Upstream dams have less effect on the hydrology and sediment supply in Cataract Canyon compared with downstream reaches in Grand Canyon National Park. For this reason, comparison of these vegetation and substrate measurements with similar data from aeolian landscapes of Grand Canyon will help to resolve the effects of Glen Canyon Dam operations on the Colorado River corridor ecosystem.

  5. Adhesion and abrasion of surface materials in the Venusian aeolian environment

    NASA Astrophysics Data System (ADS)

    Marshall, J. R.; Fogleman, G.; Greeley, R.; Hixon, R.; Tucker, D.

    1991-02-01

    In laboratory simulations of the Venusian environment, rock and mineral 'target' surfaces struck by aeolian particles develop a thin layer of accretionary material derived from the particles' attrition debris. Accretion may be (in part) a manifestation of 'cold welding', a process well known in engineering, where bonding occurs between metals at a tribological interface. Accretion on geological materials was found to occur at all Venusian surface temperatures and for all types of materials tested. First-order variations in the amount deposited by particles are related to relative attrition susceptibilities. Second-order variations relate to properties of the particle-target interface. Variations in accretion volume are apparently independent of mineral chemistry and are only weakly dependent on crystallography. The results suggest that accretion should be a fairly universal phenomenon in areas of Venus subject to aeolian activity.

  6. New Method for Estimation of Aeolian Sand Transport Rate Using Ceramic Sand Flux Sensor (UD-101)

    PubMed Central

    Udo, Keiko

    2009-01-01

    In this study, a new method for the estimation of aeolian sand transport rate was developed; the method employs a ceramic sand flux sensor (UD-101). UD-101 detects wind-blown sand impacting on its surface. The method was devised by considering the results of wind tunnel experiments that were performed using a vertical sediment trap and the UD-101. Field measurements to evaluate the estimation accuracy during the prevalence of unsteady winds were performed on a flat backshore. The results showed that aeolian sand transport rates estimated using the developed method were of the same order as those estimated using the existing method for high transport rates, i.e., for transport rates greater than 0.01 kg m−1 s−1. PMID:22291553

  7. Late Amazonian aeolian features, gradation, wind regimes, and Sediment State in the Vicinity of the Mars Exploration Rover Opportunity, Meridiani Planum, Mars

    NASA Astrophysics Data System (ADS)

    Fenton, Lori K.; Michaels, Timothy I.; Chojnacki, Matthew

    2015-03-01

    LDD morphology and migration dominated by a northwesterly wind. This apparent inconsistency may be caused by spatial topographic variations at a local scale and temporal variations in atmospheric conditions (e.g., static stability and wind velocity), such that aeolian transport in larger craters (>15 km) responds differently to a regionally-uniform wind than that in smaller craters (<3 km). The preserved surface record from the Late Amazonian consists of four periods of bedform construction. (1) The oldest wind corresponds to putative east-west oriented bedforms on the plains, from which little information may be recovered. (2) Prior to ∼200 ka, an easterly wind created TARs, plains ripples, plains-like ripples on crater floors, and ripple streaks. (3) At some point between ∼50 and ∼200 ka, smaller bedforms with northeast-southwest oriented crestlines partially reworked both plains ripples and TARs, and small similarly-oriented bedforms accumulated in the floors of craters. (4) Finally, the present-day crestline orientations of LDDs and dark sand streaks are inconsistent with each of the older bedforms. Excluding the first wind regime, the remaining bedforms can be represented by an easterly wind gradually giving way to a relative strengthening of northwesterly and southeasterly winds. Based on observations, one possible scenario describing the sediment state of the plains alternated between transport-limited contemporaneous and lagged sediment influx (CLITL), during which bedforms are constructed, and relatively long periods (including the present-day) of availability-limited contemporaneous sediment influx (CIAL).

  8. Long-Term Simulation of Dust Distribution with the GOCART Model: Correlation with the North Atlantic Oscillation

    NASA Technical Reports Server (NTRS)

    Ginoux, P.; Prospero, J.; Torres, O.; Chin, M.

    2002-01-01

    Global distribution of aeolian dust is simulated from 1981 to 1996 with the Goddard Ozone Chemistry Aerosol Radiation and Transport (GOCART) model. The results are assessed with in-situ measurements and the Total Ozone Mapping Spectrometer (TOMS) aerosol products. The annual budget over the different continents and oceans are analyzed. It is found that there is a maximum of 25% difference of global annual emission from the minimum in 1996 to the maximum in 1988. There is a downward trend of dust emission over Africa and East Asia, of 6 and 2 Tg/yr, respectively. The inter-annual variability of dust distribution is analyzed over the North Atlantic and Africa. It is found that in winter most of the North Atlantic and Africa dust loading is correlated with the North Atlantic Oscillation. The GOCART model indicates that a controlling factor of such correlation can be attributed to dust emission from the Sahel. The Bodele depression is the major dust source in winter and its inter-annual variability is highly correlated with the NAO. However, it is not possible to conclude without further analysis that the North Atlantic Oscillation is forcing the inter-annual variability of dust emission and in-turn dust concentration over the North Atlantic.

  9. Community variability of bacteria in alpine snow (Mont Blanc) containing Saharan dust deposition and their snow colonisation potential.

    PubMed

    Chuvochina, Maria S; Marie, Dominique; Chevaillier, Servanne; Petit, Jean-Robert; Normand, Philippe; Alekhina, Irina A; Bulat, Sergey A

    2011-01-01

    Microorganisms uplifted during dust storms survive long-range transport in the atmosphere and could colonize high-altitude snow. Bacterial communities in alpine snow on a Mont Blanc glacier, associated with four depositions of Saharan dust during the period 2006-2009, were studied using 16S rRNA gene sequencing and flow cytometry. Also, sand from the Tunisian Sahara, Saharan dust collected in Grenoble and Mont Blanc snow containing no Saharan dust (one sample of each) were analyzed. The bacterial community composition varied significantly in snow containing four dust depositions over a 3-year period. Out of 61 phylotypes recovered from dusty snow, only three phylotypes were detected in more than one sample. Overall, 15 phylotypes were recognized as potential snow colonizers. For snow samples, these phylotypes belonged to Actinobacteria, Proteobacteria and Cyanobacteria, while for Saharan sand/dust samples they belonged to Actinobacteria, Bacteroidetes, Deinococcus-Thermus and Proteobacteria. Thus, regardless of the time-scale, Saharan dust events can bring different microbiota with no common species set to alpine glaciers. This seems to be defined more by event peculiarities and aeolian transport conditions than by the bacterial load from the original dust source.

  10. Aeolian nutrient fluxes following wildfire in sagebrush steppe: Implications for soil carbon storage

    USGS Publications Warehouse

    Hasselquist, N.J.; Germino, M.J.; Sankey, J.B.; Ingram, L.J.; Glenn, N.F.

    2011-01-01

    Pulses of aeolian transport following fire can profoundly affect the biogeochemical cycling of nutrients in semi-arid and arid ecosystems. Our objective was to determine horizontal nutrient fluxes occurring in the saltation zone during an episodic pulse of aeolian transport that occurred following a wildfire in a semi-arid sagebrush steppe ecosystem in southern Idaho, USA. We also examined how temporal trends in nutrient fluxes were affected by changes in particle sizes of eroded mass as well as nutrient concentrations associated with different particle size classes. In the burned area, total carbon (C) and nitrogen (N) fluxes were as high as 235 g C m????'1 d????'1 and 19 g N m????'1 d????'1 during the first few months following fire, whereas C and N fluxes were negligible in an adjacent unburned area throughout the study. Temporal variation in C and N fluxes following fire was largely attributable to the redistribution of saltation-sized particles. Total N and organic C concentrations in the soil surface were significantly lower in the burned relative to the unburned area one year after fire. Our results show how an episodic pulse of aeolian transport following fire can affect the spatial distribution of soil C and N, which, in turn, can have important implications for soil C storage. These findings demonstrate how an ecological disturbance can exacerbate a geomorphic process and highlight the need for further research to better understand the role aeolian transport plays in the biogeochemical cycling of C and N in recently burned landscapes. ?? Author(s) 2011. CC Attribution 3.0 License.

  11. The trace-element characteristics of Aegean and Aeolian volcanic arc marine tephra

    NASA Astrophysics Data System (ADS)

    Clift, Peter; Blusztajn, Jerzy

    1999-10-01

    High-silica volcanic ashes are found within deep-sea sediments throughout the Eastern Mediterranean. Although coring by Ocean Drilling Program has penetrated Lower Pliocene (˜4 Ma) sediments, few ashes older than 400 k.y. have been recovered, suggesting a young initiation to subaerial Aegean Arc volcanism. Ashes derived from the Aegean volcanic front were cored south and east of the arc, and are typified by medium-K, calc-alkaline major-element compositions, contrasting with high-K ashes from the Aeolian Arc found in the Ionian Sea and as far east as Crete. Ion microprobe analysis of individual glass shards shows that all the ashes have a light rare earth element (LREE)-enriched pattern after normalizing against a chondrite standard. Aeolian Arc-derived ashes show greater enrichment than those from the Aegean area. Within the latter set, two groups are discernible, a mildly enriched set similar to the volcanoes of the arc volcanic front, and a more enriched group corresponding to lavas from the backarc region or possible from western Anatolia. Multi-element `spider diagrams' also show a bimodal division of enriched and depleted Aegean ashes, possibly caused by source depletion due to melt extraction in the Aegean backarc followed by remelting under the volcanic front. Relative Nb depletion, a characteristic of arc volcanism, is seen to be modest in Aegean and non-existent in Aeolian ashes. Using B/Be as a proxy for the flux of material from the subducting slab, this influence is seen to be low in the Aeolian Arc but higher than at Vesuvius. B/Be is higher again in the Aegean Arc. These differences may reflect the rate of subduction in each system. Data suggest caution is required when correlating ashes solely on the basis of major elements, as alkaline ashes from the central part of the study may be derived from Italy or from the Aegean backarc.

  12. Aeolian nutrient fluxes following wildfire in sagebrush steppe: implications for soil carbon storage

    NASA Astrophysics Data System (ADS)

    Hasselquist, N. J.; Germino, M. J.; Sankey, J. B.; Ingram, L. J.; Glenn, N. F.

    2011-12-01

    Pulses of aeolian transport following fire can profoundly affect the biogeochemical cycling of nutrients in semi-arid and arid ecosystems. Our objective was to determine horizontal nutrient fluxes occurring in the saltation zone during an episodic pulse of aeolian transport that occurred following a wildfire in a semi-arid sagebrush steppe ecosystem in southern Idaho, USA. We also examined how temporal trends in nutrient fluxes were affected by changes in particle sizes of eroded mass as well as nutrient concentrations associated with different particle size classes. In the burned area, total carbon (C) and nitrogen (N) fluxes were as high as 235 g C m-1 d-1 and 19 g N m-1 d-1 during the first few months following fire, whereas C and N fluxes were negligible in an adjacent unburned area throughout the study. Temporal variation in C and N fluxes following fire was largely attributable to the redistribution of saltation-sized particles. Total N and organic C concentrations in the soil surface were significantly lower in the burned relative to the unburned area one year after fire. Our results show how an episodic pulse of aeolian transport following fire can affect the spatial distribution of soil C and N, which, in turn, can have important implications for soil C storage. These findings demonstrate how an ecological disturbance can exacerbate a geomorphic process and highlight the need for further research to better understand the role aeolian transport plays in the biogeochemical cycling of C and N in recently burned landscapes.

  13. Land surface memory effects on dust emission in a Mongolian temperate grassland

    NASA Astrophysics Data System (ADS)

    Nandintsetseg, Banzragch; Shinoda, Masato

    2015-03-01

    Aeolian processes in temperate grasslands are unique in that the plant growth-decay cycle, soil moisture/snowpack dynamics, and induced grazing interactively affect seasonal and interannual variations of dust emission. This study uses process-based ecosystem model DAYCENT and unique saltation flux measurements to (1) identify primary land surface factors that control dust emission with soil moisture and vegetation components (live grasses, standing dead grasses, and litter) in a Mongolian grassland and (2) test the dead-leaf hypothesis proposed by previous observational studies that correlates plant biomass in summer and dust events the following spring. In general, the DAYCENT model realistically simulates seasonal and interannual variations of the vegetation components and soil moisture that were captured by field observations during 2003-2010. Then, the land surface components are correlated with measured daily saltation flux in the springs of 2008-2009 and the frequency of monthly dusty days during March-June 2002-2010. Results show that dust emission had a similar amplitude of significant correlation with wind speed and a combination of all land surface components, which demonstrates a memory of the preceding year. The memory analysis reveals that vegetation and soil moisture anomalies during spring dust emission are significantly autocorrelated with the preceding year's (autumn) corresponding anomalies, which were controlled by rainfall during a given summer. Most importantly, of the vegetation components, the standing dead grasses had the strongest memory and simultaneous correlation with spring dust emission, suggesting the validity of the dead-leaf hypothesis.

  14. Alluvial Fans on Dunes in Kaiser Crater Suggest Niveo-Aeolian and Denivation Processes on Mars

    NASA Technical Reports Server (NTRS)

    Bourke, M. C.

    2005-01-01

    On Earth, cold region sand dunes often contain inter-bedded sand, snow, and ice. These mixed deposits of wind-driven snow, sand, silt, vegetal debris, or other detritus have been termed Niveo-aeolian deposits. These deposits are often coupled with features that are due to melting or sublimation of snow, called denivation features. Snow and ice may be incorporated into dunes on Mars in three ways. Diffusion of water vapour into pore spaces is the widely accepted mechanism for the accretion of premafrost ice. Additional mechanisms may include the burial by sand of snow that has fallen on the dune surface or the synchronous transportation and deposition of snow, sand and ice. Both of these mechanisms have been reported for polar dunes on Earth. Niveo-aeolian deposits in polar deserts on Earth have unique morphologies and sedimentary structures that are generally not found in warm desert dunes. Recent analysis of MOC-scale data have found evidence for potential niveo-aeolian and denivation deposits in sand dunes on Mars.

  15. Aeolian sediment transport and landforms in managed coastal systems: A review

    NASA Astrophysics Data System (ADS)

    Jackson, Nancy L.; Nordstrom, Karl F.

    2011-11-01

    Humans modify beaches and dunes and aeolian transport potential by building structures, walking or driving, extracting resources, accommodating recreation, increasing levels of protection, removing storm deposits, or restoring landforms and habitats. The effects of human adjustments are reviewed here in terms of cross-shore zones because humans tend to compartmentalize landforms and habitats through their actions and regulations. Common human modifications in the beach zone include nourishing beaches, constructing shore protection structures and raking to remove litter. Modifications affecting the dune zone include altering the location, size and stability of dunes using sand-trapping fences, vegetation plantings and bulldozers or replacing dunes with shore-parallel structures. Modifications affecting the landward zone include buildings, roads, and parking lots. Landform and habitat resilience requires levels of dynamism and geomorphic complexity not often found in managed systems. Preserving or enhancing dynamism and complexity requires emphasis on innovative designs rooted in geomorphological and aeolian research. Future studies are suggested for: (1) quantifying the effect of small and large scale beach nourishment designs and sediment characteristics on dune initiation, development, and evolution; (2) quantifying the extent to which size and spacing of human structures and landform alterations inhibit sediment transfers alongshore or onshore; (3) identifying the advantages or disadvantages of "niche" dunes formed by structures; (4) providing quantitative data on the effects of raking or driving on the beach; (5) identifying the role of aeolian landforms on private properties; and (6) identifying alternative ways of employing sand fences and vegetation plantings to increase topographic and habitat diversity.

  16. 2007 Weather and Aeolian Sand-Transport Data from the Colorado River Corridor, Grand Canyon, Arizona

    USGS Publications Warehouse

    Draut, Amy E.; Andrews, Timothy; Fairley, Helen C.; Brown, Christopher R.

    2009-01-01

    Weather data constitute an integral part of ecosystem monitoring in the Colorado River corridor and are particularly valuable for understanding processes of landscape change that contribute to the stability of archeological sites. Data collected in 2007 are reported from nine weather stations in the Colorado River corridor through Grand Canyon, Ariz. The stations were deployed in February and March 2007 to measure wind speed and direction, rainfall, air temperature, relative humidity, and barometric pressure. Sand traps near each weather station collect windblown sand, from which daily aeolian sand-transport rates are calculated. The data reported here were collected as part of an ongoing study to test and evaluate methods for quantifying processes that affect the physical integrity of archeological sites along the river corridor; as such, these data can be used to identify rainfall events capable of causing gully incision and to predict likely transport pathways for aeolian sand, two landscape processes integral to the preservation of archeological sites. Weather data also have widespread applications to other studies of physical, cultural, and biological resources in Grand Canyon. Aeolian sand-transport data reported here, collected in the year before the March 2008 High-Flow Experiment (HFE) at Glen Canyon Dam, represent baseline data against which the effects of the 2008 HFE on windblown sand will be compared in future reports.

  17. Geochemistry of selected lavas of the Panarea volcanic group, Aeolian Arc, Italy

    NASA Astrophysics Data System (ADS)

    Doherty, A. L.; Cannatelli, C.; Raia, F.; Belkin, H. E.; Albanese, S.; Lima, A.; De Vivo, B.

    2015-10-01

    The Panarea Volcanic Group (PVG) is a group of emergent islands rising from the truncated cone of an underwater edifice in the eastern sector of the Aeolian Island Arc in the Tyrrhenian Sea, Italy. Selected lava units from the main island of Panarea and some of the nearby islets were analysed for their major and trace element compositions to the dataset available in the literature. Major mineral phases were identified as plagioclase ± clinopyroxene ± orthopyroxene ± olivine ± amphibole ± mica. The lavas of this study range from andesite to rhyolite with major element compositions equivalent to previously published data. Pyroxene geobarometry suggests a polybaric distribution to crystal fractionation, beginning at the Moho, and continuing to a shallow magma reservoir, at approximately 0.8 km depth. A plot of Nd143/Nd144 vs. Sr87/Sr86 show the compositions of Panarea overlap with the compositions of the eastern and central Aeolian Arc, while Pb208/Pb204 vs. Pb206/Pb204 do not overlap, but fall between the central and eastern arc values. As major and trace element concentrations, and isotope compositions of the lavas of this study overlap most consistently with lava compositions from the central and eastern Aeolian Arc, indicating Panarea should be considered an "intermediate" volcano in the arc.

  18. Dust and Planetary Rings

    NASA Astrophysics Data System (ADS)

    Siddiqui, Muddassir

    ABSTRACT Space is not empty it has comic radiations (CMBR), dust etc. Cosmic dust is that type of dust which is composed of particles in space which vary from few molecules to 0.1micro metres in size. This type of dust is made up of heavier atoms born in the heart of stars and supernova. Mainly it contains dust grains and when these dust grains starts compacting then it turns to dense clouds, planetary ring dust and circumstellar dust. Dust grains are mainly silicate particles. Dust plays a major role in our solar system, for example in zodiacal light, Saturn's B ring spokes, planetary rings at Jovian planets and comets. Observations and measurements of cosmic dust in different regions of universe provide an important insight into the Universe's recycling processes. Astronomers consider dust in its most recycled state. Cosmic dust have radiative properties by which they can be detected. Cosmic dusts are classified as intergalactic dusts, interstellar dusts and planetary rings. A planetary ring is a ring of cosmic dust and other small particles orbiting around a planet in flat disc shape. All of the Jovian planets in our solar system have rings. But the most notable one is the Saturn's ring which is the brightest one. In March 2008 a report suggested that the Saturn's moon Rhea may have its own tenuous ring system. The ring swirling around Saturn consists of chunks of ice and dust. Most rings were thought to be unstable and to dissipate over course of tens or hundreds of millions of years but it now appears that Saturn's rings might be older than that. The dust particles in the ring collide with each other and are subjected to forces other than gravity of its own planet. Such collisions and extra forces tend to spread out the rings. Pluto is not known to have any ring system but some Astronomers believe that New Horizons probe might find a ring system when it visits in 2015.It is also predicted that Phobos, a moon of Mars will break up and form into a planetary ring

  19. Reconciling historical and contemporary evidence of aeolian-based, gully annealing processes in Glen, Marble, and Grand Canyon, USA

    NASA Astrophysics Data System (ADS)

    Sankey, J. B.; Draut, A. E.

    2013-12-01

    In the absence of large Colorado River floods in Glen, Marble, and Grand Canyons since the completion of Glen Canyon Dam, the geomorphic process most able to counteract the effects of gully incision on terraces and slopes above the contemporary active Colorado River channel is aeolian sand transport that can partially or entirely fill (anneal) small gullies. Whereas gully-formation processes have been much studied, relatively little is known about processes of gully annealing. Aeolian-based annealing has been observed in several instances in the modern Colorado River corridor operating on time scales of months. However, individual, short-term occurrences of aeolian deposition that counteract gully erosion have not yet been expanded into a landscape-scale evaluation of the prevalence of gully-annealing processes over longer time scales (years-decades) along the post-dam corridor. The extent that aeolian or other annealing processes might slow, or temporarily reverse, gully incision and erosion is important in this system because of the propensity for erosion damage to locations of cultural significance that are extensive on terraces and slopes above the contemporary active Colorado River channel. Moreover, the reduction of mainstem fluvial sediment inputs to the system since completion of Glen Canyon Dam might impact the potential of aeolian redistribution of Colorado River-derived sediment as an effective gully annealing mechanism on upper slopes and terraces. We present an investigation of the extent that observations of (i) historical annealing and (ii) contemporary annealing potential, reconcile with (iii) literature and/or model-based estimates of relative rates of gully formation and aeolian deposition in this system. The central question of this work is whether these complimentary lines of evidence support aeolian infilling as a viable mechanism for annealing gullies in Glen, Marble, and Grand Canyons, and analogous systems. We examine the evidence for

  20. Aeolian dust event in Korea observed by an EZ Lidar in the frame of global lidar networks.

    NASA Astrophysics Data System (ADS)

    Lolli, Simone

    2010-05-01

    Duststorms and sandstorms regularly devastate Northeast Asia and cause considerable damage to transportation system and public health; further, these events are conceived to be one of the very important indices for estimating the global warming and desertification. Previously, yellow sand events were considered natural phenomena that originate in deserts and arid areas. However, the greater scale and frequency of these events in recent years are considered to be the result of human activities such as overgrazing and over-cultivation. Japan, Korea, Cina and Mongolia are directly concerned to prevent and control these storms and have been able to some extent to provide forecasts and early warnings. In this framework, to improve the accuracy of forecasting , a compact and rugged eye safe lidar, the EZ LIDAR™, developed together by Laboratoire des Sciences du Climat et l'Environnement (LSCE) (CEA-CNRS) and LEOSPHERE (France) to study and investigate structural and optical properties of clouds and aerosols, thanks to the strong know-how of CEA and CNRS in the field of air quality measurements and cloud observation and analysis, was deployed in Seoul, Korea in order to detect and study yellow sand events, thanks to its depolarization channel and scan capabilities. The preliminary results, showed in this paper, of this measurement campaign put in evidence that EZ Lidar, for its capabilities of operating unattended day and night under each atmospheric condition, is mature to be deployed in a global network to study long-range transport, crucial in the forecasting model.

  1. Model of Image Artifacts from Dust Particles

    NASA Technical Reports Server (NTRS)

    Willson, Reg

    2008-01-01

    is the shape (typically, circular) of the aperture, and the contribution of the particle to the attenuation factor for a given pixel is the fraction of the cross-sectional area of the collection cone occupied by the particle. Assuming that dust particles do not overlap, the net transmission factor for a given pixel is calculated as one minus the sum of attenuation factors contributed by all dust particles affecting that pixel. In a test, the model was used to synthesize attenuation images for random distributions of dust particles on the front surface of a lens at various relative aperture (F-number) settings. As shown in Figure 2, the attenuation images resembled dust artifacts in real test images recorded while the lens was aimed at a white target.

  2. Natural variability versus human impact: Hydroclimate variability and the role of agriculture in changing dust emissions from Australia.

    NASA Astrophysics Data System (ADS)

    Marx, Samuel; Kamber, Balz; McGowan, Hamish; Hooper, James; Zawadzki, Atun

    2016-04-01

    Broad-scale dust emissions play an important role in Earth systems, for example influencing oceanic productivity via phytoplankton fertilisation. Existing palaeo dust records show that dust emissions vary significantly in time, implying its impact is similarly variable. There remains, however, a paucity of records which quantify variability in dust emissions. This study presents continuous, Holocene-aged, records of dust emissions from Australia, an important global dust source. Records demonstrate that rates of dust export have varied by 8-30 times over the mid to late Holocene. This variability is largely attributed to hydroclimate variability and its associated feedbacks within dust source areas. Significantly, however, a major disruption of dust emission rates is recorded in the past 200 years when dust emissions increased by between 2-10 times rates of natural variability in dust export. This change is concomitant with the arrival of Europeans in Australia and is primarily attributed to the development of agriculture which resulted in unprecedented environmental change in Australia's arid interior. This result broadly accords with the few other existing empirical dust records which both pre-date and post-date the onset of agriculture in various arid and semi-arid regions. Collectively, these records imply the impact of dust in Earth systems has changed as a result of agricultural development.

  3. Earlier vegetation green-up has reduced spring dust storms.

    PubMed

    Fan, Bihang; Guo, Li; Li, Ning; Chen, Jin; Lin, Henry; Zhang, Xiaoyang; Shen, Miaogen; Rao, Yuhan; Wang, Cong; Ma, Lei

    2014-01-01

    The observed decline of spring dust storms in Northeast Asia since the 1950s has been attributed to surface wind stilling. However, spring vegetation growth could also restrain dust storms through accumulating aboveground biomass and increasing surface roughness. To investigate the impacts of vegetation spring growth on dust storms, we examine the relationships between recorded spring dust storm outbreaks and satellite-derived vegetation green-up date in Inner Mongolia, Northern China from 1982 to 2008. We find a significant dampening effect of advanced vegetation growth on spring dust storms (r = 0.49, p = 0.01), with a one-day earlier green-up date corresponding to a decrease in annual spring dust storm outbreaks by 3%. Moreover, the higher correlation (r = 0.55, p < 0.01) between green-up date and dust storm outbreak ratio (the ratio of dust storm outbreaks to times of strong wind events) indicates that such effect is independent of changes in surface wind. Spatially, a negative correlation is detected between areas with advanced green-up dates and regional annual spring dust storms (r = -0.49, p = 0.01). This new insight is valuable for understanding dust storms dynamics under the changing climate. Our findings suggest that dust storms in Inner Mongolia will be further mitigated by the projected earlier vegetation green-up in the warming world.

  4. Earlier vegetation green-up has reduced spring dust storms.

    PubMed

    Fan, Bihang; Guo, Li; Li, Ning; Chen, Jin; Lin, Henry; Zhang, Xiaoyang; Shen, Miaogen; Rao, Yuhan; Wang, Cong; Ma, Lei

    2014-01-01

    The observed decline of spring dust storms in Northeast Asia since the 1950s has been attributed to surface wind stilling. However, spring vegetation growth could also restrain dust storms through accumulating aboveground biomass and increasing surface roughness. To investigate the impacts of vegetation spring growth on dust storms, we examine the relationships between recorded spring dust storm outbreaks and satellite-derived vegetation green-up date in Inner Mongolia, Northern China from 1982 to 2008. We find a significant dampening effect of advanced vegetation growth on spring dust storms (r = 0.49, p = 0.01), with a one-day earlier green-up date corresponding to a decrease in annual spring dust storm outbreaks by 3%. Moreover, the higher correlation (r = 0.55, p < 0.01) between green-up date and dust storm outbreak ratio (the ratio of dust storm outbreaks to times of strong wind events) indicates that such effect is independent of changes in surface wind. Spatially, a negative correlation is detected between areas with advanced green-up dates and regional annual spring dust storms (r = -0.49, p = 0.01). This new insight is valuable for unde