Special Issue "Aeolian Processes and Geomorphology"

A special issue of Geosciences (ISSN 2076-3263).

Deadline for manuscript submissions: closed (30 June 2018)

Special Issue Editor

Guest Editor
Dr. Eric J. R. Parteli

Department of Geosciences, Universität zu Köln, Germany
Website | E-Mail
Interests: granular materials; aeolian processes; planetary geomorphology; physics of complex systems

Special Issue Information

Dear Colleagues,

This Special Issue is dedicated to recent progress in our understanding of aeolian processes—the emission, transport and deposition of dust and sand particles by wind—and the concatenated geomorphology of Earth and extra-terrestrial environments.

Wind-blown particles shape a substantial portion of the surface of our planet, and play a major role for weather, climate, and several other components of the Earth system. Airborne dust particles can be transported over thousands of kilometers from their source, thereby affecting the hydrological cycle, ecosystem productivity and human health. Moreover, wind-blown sand erodes rocks and soils, and creates a broad range of aeolian bedforms, including migrating ripples, megaripples and dunes, which are largely responsible for the morphodynamics of Earth’s deserts and coasts. Aeolian sand plays an important role for the propagation of desertification, which contributes to increase global warming and enhance poverty in many countries of the Earth.

The understanding of aeolian processes and their geomorphological implications has impact not only in the research of Earth’s climate and geology, but also in the planetary science. Aeolian dust research may help understand climate processes on Mars, where large dust storms obscuring the Sun over entire regions of the planet for several days at a time have been detected at different occasions since the first missions sent to the red planet. Moreover, aeolian bedforms are widespread on Mars, and occur also on Venus, Saturn’s moon Titan and the comet 67P/Churyumov-Gerasimenko. Images sent by New Horizons revealed that wind-blown particles have helped to shape the complex geology of the surface of Pluto as well. Bedform morphology and migration rates can serve as proxy for wind regimes, as well as attributes of sediment and atmosphere in extra-terrestrial environments. However, the accurate prediction of aeolian sediment fluxes and dune morphodynamics in such environments still poses one of the biggest challenges in planetary aeolian geomorphology.

Manuscripts in this Special Issue report progress in our understanding of aeolian transport of sand and the resulting landforms, the emission, transport and deposition of dust as well as the impact of dust on the Earth’s system, the characteristics and impact of aeolian processes in extra-terrestrial worlds, as well as the application of aeolian dust and dune research in the investigation of paleoenvironments, dating of aeolian deposits and bedforms of the Pleistocene and Holocene. This Special Issue further aims at highlighting progress in our understanding of the interaction between aeolian processes and biota, the impact of anthropogenic influences on aeolian sediment dynamics, the development of large sand seas, the characteristics of dune sediments, aeolian snow particles and landforms, dune management, wind erosion on agricultural fields and the control of dust and drifting sand. Moreover, manuscripts in this Special Issue report advances in theoretical and numerical models, as well as the newest developments in field and laboratory techniques, to investigate aeolian particles and bedforms.

This Special Issue is open both for manuscripts reporting results from original research and for inspiring review articles, which include a critical overview of the state-of-the-art in the research field considered, as well as an outlook of open, challenging problems to be addressed in future work.

Dr. Eric J. R. Parteli
Guest Editor

 

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Keywords

  • aeolian processes and geomorphology
  • planetary aeolian processes
  • paleoenvironments
  • dune sediments
  • wind erosion
  • control of dust and drifting sand
  • advances in theory, numerical modeling, field and lab methods

Published Papers (10 papers)

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Research

Jump to: Review

Open AccessArticle Aeolian Material Migration in Transbaikalia (Asian Russia)
Geosciences 2019, 9(1), 41; https://doi.org/10.3390/geosciences9010041
Received: 25 November 2018 / Revised: 21 December 2018 / Accepted: 2 January 2019 / Published: 14 January 2019
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Abstract
We revealed regional features of functioning of a large Transbaikalian aeolian morphodynamic system. Natural pre-conditions, current realities and factors of development of aeolian processes are investigated. The paper considers regularities of spatial distribution of deflation, transit, and aeolian accumulation zones. Main directions of [...] Read more.
We revealed regional features of functioning of a large Transbaikalian aeolian morphodynamic system. Natural pre-conditions, current realities and factors of development of aeolian processes are investigated. The paper considers regularities of spatial distribution of deflation, transit, and aeolian accumulation zones. Main directions of aeolian migration of matter are determined. Pulsating nature of aeolian processes development in Holocene has been established. Identified are intrasecular cycles and Holocene dynamics of aeolian processes. We identified intrasecular (11, 27–35 years old), secular (80 year old) and Holocene (500, 2000 year old) cycles of aeolian process dynamics. The paper shows the influence of anthropogenic activity on the activation of aeolian migration of material for the historical period. It presents an overview of extreme aeolian events. Regionalization of Transbaikalia was carried out according to the degree of probable desertification of the territory due to development of aeolian processes. Areas of catastrophic manifestation of processes are highlighted. The results of long-term experimental observations of deflation and aeolian accumulation are presented. Particular attention is paid to the characteristics of the aeolian corridors. The important role of aeolian processes in the intensive material transport from Transbaikalia to the south and southeast to neighboring regions of Mongolia and China is shown. Full article
(This article belongs to the Special Issue Aeolian Processes and Geomorphology)
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Open AccessArticle The Critical Role of the Boundary Layer Thickness for the Initiation of Aeolian Sediment Transport
Geosciences 2018, 8(9), 314; https://doi.org/10.3390/geosciences8090314
Received: 29 June 2018 / Revised: 15 August 2018 / Accepted: 20 August 2018 / Published: 23 August 2018
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Abstract
Here, we propose a conceptual framework of Aeolian sediment transport initiation that includes the role of turbulence. Upon increasing the wind shear stress τ above a threshold value τt, particles resting at the bed surface begin to rock in their [...] Read more.
Here, we propose a conceptual framework of Aeolian sediment transport initiation that includes the role of turbulence. Upon increasing the wind shear stress τ above a threshold value τ t , particles resting at the bed surface begin to rock in their pockets because the largest turbulent fluctuations of the instantaneous wind velocity above its mean value u ¯ induce fluid torques that exceed resisting torques. Upon a slight further increase of τ , rocking turns into a rolling regime (i.e., rolling threshold τ t τ t ) provided that the ratio between the integral time scale T i δ / u ¯ (where δ is the boundary layer thickness) and the time T e d / [ ( 1 1 / s ) g ] required for entrainment (where d is the particle diameter and s the particle–air–density ratio) is sufficiently large. Rolling then evolves into mean-wind-sustained saltation transport provided that the mean wind is able to compensate energy losses from particle-bed rebounds. However, when T i / T e is too small, the threshold ratio scales as τ t / τ t T e / T i s d 2 / δ 2 , consistent with experiments. Because δ / d controls T i / T e and the relative amplitude of turbulent wind velocity fluctuations, we qualitatively predict that Aeolian sediment transport in natural atmospheres can be initiated under weaker (potentially much weaker) winds than in wind tunnels, consistent with indirect observational evidence on Earth and Mars. Full article
(This article belongs to the Special Issue Aeolian Processes and Geomorphology)
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Open AccessArticle Tree Belts for Decreasing Aeolian Dust-Carried Pesticides from Cultivated Areas
Geosciences 2018, 8(8), 286; https://doi.org/10.3390/geosciences8080286
Received: 29 June 2018 / Revised: 24 July 2018 / Accepted: 24 July 2018 / Published: 30 July 2018
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Abstract
The aim of this study was to investigate the function of tree belts in reducing the aeolian transport of dust particles carrying pesticides. The study examined the importance of the buffer zones created by commonly planted trees (Eucalyptus camaldulensis, Pinus halepensis [...] Read more.
The aim of this study was to investigate the function of tree belts in reducing the aeolian transport of dust particles carrying pesticides. The study examined the importance of the buffer zones created by commonly planted trees (Eucalyptus camaldulensis, Pinus halepensis (pine) and Ceratonia siliqua (carob)). The methods include analyzing the quantity and the chemical composition of pesticides carried by aeolian dust particles from the intensively cultivated fields and orchards, where pesticides were applied, towards the tree belts nearby. Eighteen different chemicals used as insecticides, fungicides and herbicides, were found both in the agricultural fields and in the adjacent tree belts, suggesting an important function of the trees. This ecological service has rarely been taken into consideration by management policies of tree plantings in farmland areas. To integrate this service into agriculture, especially in the case of agricultural fields and orchards, which are adjacent to populated areas, planting tree belts should be positively considered as a means for reducing aeolian dust and air pollution, mainly in order to reduce leakage of pesticides, which are a cause for significant health concerns. Full article
(This article belongs to the Special Issue Aeolian Processes and Geomorphology)
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Open AccessArticle Migration of Barchan Dunes in Qatar–Controls of the Shamal, Teleconnections, Sea-Level Changes and Human Impact
Geosciences 2018, 8(7), 240; https://doi.org/10.3390/geosciences8070240
Received: 29 April 2018 / Revised: 21 June 2018 / Accepted: 22 June 2018 / Published: 29 June 2018
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Abstract
Barchan dune fields are a dominant landscape feature in SE Qatar and a key element of the peninsula’s geodiversity. The migration of barchan dunes is mainly controlled by dune size, wind patterns, vegetation cover and human impact. We investigate the variability of dune [...] Read more.
Barchan dune fields are a dominant landscape feature in SE Qatar and a key element of the peninsula’s geodiversity. The migration of barchan dunes is mainly controlled by dune size, wind patterns, vegetation cover and human impact. We investigate the variability of dune migration in Qatar over a time period of 50 years using high-resolution satellite and aerial imagery. We then explore its relation to the regional Shamal wind system, teleconnection patterns, and limitations in sand supply associated with the transgression of the Arabian Gulf. Strong size-dependent differences in migration rates of individual dunes as well as significant decadal variability on a dune-field scale are detected, which are found to correlate with the intensity of the North Atlantic Oscillation (NAO) and the Indian Summer Monsoon (ISM), in particular during years of relatively strong (weak) summer Shamals. High uncertainties associated with the extrapolation of migration rates back into the Holocene, however, do not permit further examination of the timing of the loss of sand supply and the onset of the mid-Holocene relative sea-level (RSL) highstand. For the youngest phase considered in this study (2006–2015), human impact has likely accelerated dune migration under a weakening Shamal regime through sand mining and excessive vehicle traffic upwind of the core study area. Full article
(This article belongs to the Special Issue Aeolian Processes and Geomorphology)
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Open AccessArticle Migration and Morphology of Asymmetric Barchans in the Central Hexi Corridor of Northwest China
Geosciences 2018, 8(6), 204; https://doi.org/10.3390/geosciences8060204
Received: 4 May 2018 / Revised: 30 May 2018 / Accepted: 1 June 2018 / Published: 6 June 2018
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Abstract
Crescent-shaped barchan dunes often display an asymmetric shape, with one limb longer than the other. As shown in previous studies, asymmetric bimodal winds constitute one major cause of barchan asymmetry, but the heterogeneous conditions of sand availability or flux, as well as topographic [...] Read more.
Crescent-shaped barchan dunes often display an asymmetric shape, with one limb longer than the other. As shown in previous studies, asymmetric bimodal winds constitute one major cause of barchan asymmetry, but the heterogeneous conditions of sand availability or flux, as well as topographic influences, may be also important. Understanding the morphology and dynamics of asymmetric barchans may have an impact in a broad range of areas, particularly as these dunes may serve as a proxy for planetary wind regimes and soil conditions in extraterrestrial environments. However, in addition to the existing theories and numerical models that explain barchan asymmetry, direct measurements of migration rates and morphologic changes of real asymmetric barchans over a time span of several years would be beneficial. Therefore, here we report such measurements, which we have acquired by investigating asymmetric barchans in the Hexi Corridor, northwest of China. We have found that dune interactions and asymmetric influx conditions are the most important causes of barchan asymmetry in this field. Particle size distributions in the Hexi Corridor display strong variations over different parts of the asymmetric barchans, as well as over different dunes, with gravel particles being incorporated from the substrate as the dunes migrate. Our observations have shown that upwind sediment sources are important for dune formation in the Hexi Corridor, and that interdune interactions affect dune shape in different ways, depending on their offset. The asymmetric barchans in the Hexi Corridor are active, with an average migration rate (MR) between 8 and 53 m year−1, in spite of the different asymmetric shapes. Our data for dune migration rates can be described well by a scaling of MR = A/(W + W0), where W is the barchan cross-wind width, A ≈ 2835 m2 s−1, and W0 ≈ 44 m. A similar scaling fits very well the migration rate as a function of dune along-wind width L, (i.e., MR = B/(L + L0), with B ≈ 1722 m2 s−1 and L0 ≈ 13 m). Linear relations are also found between both dune widths and the average limb and windward side lengths, thus indicating that the morphometric relations that are predicted from models for steady-state, symmetric crescent-shaped dunes can be applied to different transitional morphologies of interacting, asymmetric barchans. Full article
(This article belongs to the Special Issue Aeolian Processes and Geomorphology)
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Open AccessArticle Airflow Dynamics over a Beach and Foredune System with Large Woody Debris
Geosciences 2018, 8(5), 147; https://doi.org/10.3390/geosciences8050147
Received: 6 March 2018 / Revised: 18 April 2018 / Accepted: 20 April 2018 / Published: 24 April 2018
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Abstract
Airflow dynamics over beach-foredune systems can be complex. Although a great deal is known about the effects of topographic forcing and vegetation cover on wind-field modification, the role of large woody debris (LWD) as a roughness element and modifier of boundary layer flow [...] Read more.
Airflow dynamics over beach-foredune systems can be complex. Although a great deal is known about the effects of topographic forcing and vegetation cover on wind-field modification, the role of large woody debris (LWD) as a roughness element and modifier of boundary layer flow is relatively understudied. Individual pieces of LWD are non-porous elements that impose bluff body effects and induce secondary flow circulation that varies with size, density, and arrangement. Large assemblages of LWD are common on beaches near forested watersheds and collectively have a degree of porosity that increases aerodynamic roughness in ways that are not fully understood. A field study on a mesotidal sandy beach with a scarped foredune (Calvert Island, British Columbia, Canada) shows that LWD influences flow patterns and turbulence levels. Overall mean and fluctuating energy decline as flow transitions across LWD, while mean energy is converted to turbulent energy. Such flow alterations have implications for sand transport pathways and resulting sedimentation patterns, primarily by inducing deposition within the LWD matrix. Full article
(This article belongs to the Special Issue Aeolian Processes and Geomorphology)
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Open AccessArticle Late Quaternary Soil Development Enhances Aeolian Landform Stability, Moenkopi Plateau, Southern Colorado Plateau, USA
Geosciences 2018, 8(5), 146; https://doi.org/10.3390/geosciences8050146
Received: 30 March 2018 / Revised: 18 April 2018 / Accepted: 19 April 2018 / Published: 24 April 2018
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Abstract
The Moenkopi dune field in northeastern Arizona covers roughly 1250 km2, but most of the field is inactive. Dune deposits on the Moenkopi Plateau (MP) have remained inactive throughout the Holocene despite periods of elevated aridity or historical reductions of vegetation [...] Read more.
The Moenkopi dune field in northeastern Arizona covers roughly 1250 km2, but most of the field is inactive. Dune deposits on the Moenkopi Plateau (MP) have remained inactive throughout the Holocene despite periods of elevated aridity or historical reductions of vegetation cover by livestock grazing. We argue that this inactivity is not because of any diminishment of driving forces in the aeolian system (e.g., insufficient winds), but rather because of increased cohesion due to soil development that enhances resistance to wind erosion. Abundant aeolian sediments were supplied to the Black Mesa region by the Little Colorado River and its tributaries during the late Pleistocene (MIS 2 and 3), which enabled the development of climbing dunes and transport of sand over the Adeii Eechii Cliffs and onto the MP. These deposits (Qe1) stabilized during the Pleistocene/Holocene climatic transition (~12–7.5 ka) because of reduced sediment supply and high dust flux which resulted in rapid soil formation. Erosion of climbing dunes/sand ramps from the Adeii Eechii Cliffs eliminated delivery of large quantities of new sand to the MP during the mid to late Holocene. Soil development within the Qe1 mantle increased sediment cohesion and prevented widespread aeolian reactivation during the Holocene, despite the occurrence of conditions (wind speed, climate, etc.) under which dune reactivation would be expected. Drylands comprise roughly 40% of the land cover of earth and climate models predict their expansion. Pedogenic stability is not commonly considered in climate-based models used to predict aeolian activity. To improve predictions of future dune activity in drylands, the degree of soil development in aeolian deposits should be considered when evaluating sediment availability in aeolian systems. Full article
(This article belongs to the Special Issue Aeolian Processes and Geomorphology)
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Open AccessArticle Sand Dune Albedo Feedback
Geosciences 2018, 8(3), 82; https://doi.org/10.3390/geosciences8030082
Received: 11 December 2017 / Revised: 22 January 2018 / Accepted: 13 February 2018 / Published: 27 February 2018
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Abstract
Sand dunes cover substantial parts of desert areas. Fully active dunes are bare, while fixed dunes are stabilized by vegetation and biogenic crust, and the dune activity is affected by the wind. Here we suggest the following atmosphere-sand dune feedback: spatial differences in [...] Read more.
Sand dunes cover substantial parts of desert areas. Fully active dunes are bare, while fixed dunes are stabilized by vegetation and biogenic crust, and the dune activity is affected by the wind. Here we suggest the following atmosphere-sand dune feedback: spatial differences in the dunes’ vegetation and biogenic crust cover lead to differences in albedo as the albedo of bare sand is larger than that of vegetation and biogenic crust. This leads to a higher temperature over the vegetated area, resulting in air flow from the bare dune area to the vegetated dune area, thus increasing the wind activity over the vegetated dune area. In turn, this leads to enhanced stress on the vegetation and enhanced dune activity and thus to a decrease in vegetation. These changes in vegetation cover affect the surface albedo, leading to a change in wind activity. We examined this feedback using an atmospheric general circulation model, Weather Research and Forecasting (WRF), in selected regions of the northwestern Negev Desert and the Sahara/Sahel region, and we show that changes in surface albedo do indeed lead to significantly enhanced wind activity over the lower albedo region. We then incorporated this feedback into a simple vegetated dune model, showing that the multiple states associated with active and fixed dunes can be obtained for a larger range of parameters and that the stables states become more extreme (i.e., the fixed dune state becomes more vegetated and the active dune state becomes less vegetated). Full article
(This article belongs to the Special Issue Aeolian Processes and Geomorphology)
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Review

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Open AccessReview Role of Aeolian Dust in Shaping Landscapes and Soils of Arid and Semi-Arid South Africa
Geosciences 2018, 8(5), 171; https://doi.org/10.3390/geosciences8050171
Received: 1 April 2018 / Revised: 5 May 2018 / Accepted: 7 May 2018 / Published: 10 May 2018
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Abstract
The deposition of fine aeolian sediment profoundly influences the morphology of several different landscapes of the arid and semi-arid western portion of South Africa. Such landscapes and features include: (1) regularly-spaced mounds known as heuweltjies of the succulent Karoo region, (2) barren stone [...] Read more.
The deposition of fine aeolian sediment profoundly influences the morphology of several different landscapes of the arid and semi-arid western portion of South Africa. Such landscapes and features include: (1) regularly-spaced mounds known as heuweltjies of the succulent Karoo region, (2) barren stone pavements in the more arid regions, and (3) hillslopes with smooth, curvilinear slope profiles that are mantled with coarse, stony colluvium. Investigations of each of these are presented, together with comparisons of similar features found within arid and semi-arid portions of Western North America. Recent findings suggest that the formation of the distinct, regularly-spaced heuweltjies involves a linked set of biological and physical processes. These include nutrient accumulation by termites and the production of dense vegetation patches, which, in turn, serve as a trap for aeolian sediments. Dust deposition is also responsible for the formation of stone pavements as demonstrated by research conducted principally in the Mojave Desert region of the United States. Mineralogical and geochronological studies have demonstrated that the stone clasts remain on the surface as fine aeolian sediments are translocated downward beneath the clasts resulting in a silt-rich soil horizon directly beneath the clasts. Pavements examined in South Africa have the same morphological features that can only be explained by the same process. The formation of soils on hillslopes mantled with stony colluvium are commonly viewed as having formed through the in-situ weathering of the stony colluvium. However, like pavements, mantles of coarse, stony colluvium are effective dust traps that provide the long-term stability required for advanced development of thick, fine-grained soils. This process contributes to the evolution of smooth, vegetated, curvilinear slope profiles. In each of these examples, the accumulation of dust has a profound influence, not only in soil formation, but also on the development of dominant landform characteristics. A greater awareness of these processes will contribute considerably to the growth of knowledge about soils and landscape development in the drylands of South Africa. Full article
(This article belongs to the Special Issue Aeolian Processes and Geomorphology)
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Open AccessFeature PaperReview Transport of Mineral Dust and Its Impact on Climate
Geosciences 2018, 8(5), 151; https://doi.org/10.3390/geosciences8050151
Received: 31 March 2018 / Revised: 22 April 2018 / Accepted: 23 April 2018 / Published: 26 April 2018
Cited by 2 | PDF Full-text (913 KB) | HTML Full-text | XML Full-text
Abstract
Mineral dust plays a pivotal role in the Earth’s system. Dust modulates the global energy budget directly via its interactions with radiation and indirectly via its influence on cloud and precipitation formation processes. Dust is a micro-nutrient and fertilizer for ecosystems due to [...] Read more.
Mineral dust plays a pivotal role in the Earth’s system. Dust modulates the global energy budget directly via its interactions with radiation and indirectly via its influence on cloud and precipitation formation processes. Dust is a micro-nutrient and fertilizer for ecosystems due to its mineralogical composition and thus impacts on the global carbon cycle. Hence, dust aerosol is an essential part of weather and climate. Dust suspended in the air is determined by the atmospheric dust cycle: Dust sources and emission processes define the amount of dust entrained into the atmosphere. Atmospheric mixing and circulation carry plumes of dust to remote places. Ultimately, dust particles are removed from the atmosphere by deposition processes such as gravitational settling and rain wash out. During its residence time, dust interacts with and thus modulates the atmosphere resulting into changes such as in surface temperature, wind, clouds, and precipitation rates. There are still uncertainties regarding individual dust interactions and their relevance. Dust modulates key processes that are inevitably influencing the Earth energy budget. Dust transport allows for these interactions and at the same time, the intermittency of dust transport introduces additional fluctuations into a complex and challenging system. Full article
(This article belongs to the Special Issue Aeolian Processes and Geomorphology)
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