Maike Nowatzki, Kathryn E. Fitzsimmons, Hartwig Harder, Hans‐Joachim Rosner
The Ili‐Balkhash region in southeastern Kazakhstan hosts morphologically diverse dormant desert dune fields and presents an interesting opportunity for geomorphological and palaeoenvironmental studies. Because the morphology of aeolian dunes is primarily driven by wind dynamics, the dormant dunes in the study area may reflect past wind conditions. We assess their concurrence with modern ERA5 wind data to test whether there has been a change in wind regime since the dunes' last phase of activity. Our approach includes dune mapping, the quantification of dune orientations, the modelling of modern bedform orientations, and optically stimulated luminescence (OSL) dating for temporal context. The centrepiece of our methodological contribution is a novel semi‐automated mapping workflow using geographic object‐based image analysis (GEOBIA) and machine learning (ML) on Sentinel‐2 satellite imagery. Within the scope of a case study, we map dune fields in the Ili‐Balkhash region and quantify dune orientations. We further apply the maximum gross bedform‐normal transport (MGBNT) concept to model bedform orientations matching modern wind regimes for each of the sites. We find that strong winds show better alignment with observed dune orientations than wind regimes comprising all wind speeds. Furthermore, bedform orientations in some of our study sites, namely those that are located in the open plain southeast of Lake Balkhash, do not reflect modern winds. The divergence between dune orientations and wind regime suggests changes in local wind dynamics since the dune fields' last phase of activity.
{"title":"Investigating palaeodune orientations and contemporary wind regimes in Southeast Kazakhstan using a semi‐automated mapping framework","authors":"Maike Nowatzki, Kathryn E. Fitzsimmons, Hartwig Harder, Hans‐Joachim Rosner","doi":"10.1002/esp.5981","DOIUrl":"https://doi.org/10.1002/esp.5981","url":null,"abstract":"The Ili‐Balkhash region in southeastern Kazakhstan hosts morphologically diverse dormant desert dune fields and presents an interesting opportunity for geomorphological and palaeoenvironmental studies. Because the morphology of aeolian dunes is primarily driven by wind dynamics, the dormant dunes in the study area may reflect past wind conditions. We assess their concurrence with modern ERA5 wind data to test whether there has been a change in wind regime since the dunes' last phase of activity. Our approach includes dune mapping, the quantification of dune orientations, the modelling of modern bedform orientations, and optically stimulated luminescence (OSL) dating for temporal context. The centrepiece of our methodological contribution is a novel semi‐automated mapping workflow using geographic object‐based image analysis (GEOBIA) and machine learning (ML) on Sentinel‐2 satellite imagery. Within the scope of a case study, we map dune fields in the Ili‐Balkhash region and quantify dune orientations. We further apply the maximum gross bedform‐normal transport (MGBNT) concept to model bedform orientations matching modern wind regimes for each of the sites. We find that strong winds show better alignment with observed dune orientations than wind regimes comprising all wind speeds. Furthermore, bedform orientations in some of our study sites, namely those that are located in the open plain southeast of Lake Balkhash, do not reflect modern winds. The divergence between dune orientations and wind regime suggests changes in local wind dynamics since the dune fields' last phase of activity.","PeriodicalId":11408,"journal":{"name":"Earth Surface Processes and Landforms","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Eduardo Luquin, Chelsea Ferrie, Brian Gelder, Daryl Herzmann, Emily Zimmerman, David James, Richard Cruse, Thomas Isenhart
Agriculture continues to be one of the most important sources of nonpoint source pollution to surface water bodies. Consequently, it is critical to identify and prioritize high‐contributing agricultural fields and sub‐field areas for reducing soil erosion and sediment delivery by implementing best management practices (BMPs). Current erosion risk assessment tools are either complex modelling approaches or rely on a simplified reality and generalized assumption. The Daily Erosion Project (DEP) is a daily estimator of precipitation, hillslope runoff, detachment and soil loss covering ~630 000 km2 across the Midwest United States. These estimations are reported daily and publicly at the hydrologic unit code 12 watershed resolution (approximately 100 km2). The main objective of this study was to develop a new tool (named Overland Flow Element tool [OFEtool]) that downscales the watershed scale of DEP to estimate average runoff and soil displacement within a field, helping to locate erosive hotspots at multiple scales. We also demonstrated the applicability of OFEtool in Bennet Creek‐Sugar Creek in East Central Iowa (the United States) and compared its results with other erosion vulnerability tools such as the Soil Vulnerability Index for Cultivated Cropland (SVI‐cc) and a GIS‐based Revised Universal Soil Loss Equation (RUSLE). The same erosion risk classes and ranges (low, moderate, moderately high and high) were implemented for all indexes. The advantages of the OFEtool compared to the SVI‐cc and RUSLE models are related to the use of an event‐based modelling approach, such as DEP, with updated soil loss estimates based on temporal changes in climate inputs and land use and management. The OFEtool uses a 6‐year time frame and a more up‐to‐date field inputs, while RUSLE provides a long‐term average and SVI‐cc only considers soil and topographical factors for risk assessment. Results indicated that the spatial distribution of vulnerable fields (and parts of the fields) followed a similar trend as other tested indices. However, the risk level associated with each tool differed (SVI‐cc > RUSLE > OFEtool). These differences could arise from intrinsic disparities within the tools (inputs, timing, processes considered, assumptions). While currently limited to the DEP domain and relying on the DEP random sampling scheme, further research is warranted to validate the tool at other Midwest locations and ensure it captures the watershed's landscape variability (combination of terrain, soil, land use and management) required to identifying critical erosion hotspots.
{"title":"Estimating erosion vulnerability within agricultural fields by downscaling the Daily Erosion Project (DEP): the OFEtool","authors":"Eduardo Luquin, Chelsea Ferrie, Brian Gelder, Daryl Herzmann, Emily Zimmerman, David James, Richard Cruse, Thomas Isenhart","doi":"10.1002/esp.5978","DOIUrl":"https://doi.org/10.1002/esp.5978","url":null,"abstract":"Agriculture continues to be one of the most important sources of nonpoint source pollution to surface water bodies. Consequently, it is critical to identify and prioritize high‐contributing agricultural fields and sub‐field areas for reducing soil erosion and sediment delivery by implementing best management practices (BMPs). Current erosion risk assessment tools are either complex modelling approaches or rely on a simplified reality and generalized assumption. The Daily Erosion Project (DEP) is a daily estimator of precipitation, hillslope runoff, detachment and soil loss covering ~630 000 km<jats:sup>2</jats:sup> across the Midwest United States. These estimations are reported daily and publicly at the hydrologic unit code 12 watershed resolution (approximately 100 km<jats:sup>2</jats:sup>). The main objective of this study was to develop a new tool (named Overland Flow Element tool [OFEtool]) that downscales the watershed scale of DEP to estimate average runoff and soil displacement within a field, helping to locate erosive hotspots at multiple scales. We also demonstrated the applicability of OFEtool in Bennet Creek‐Sugar Creek in East Central Iowa (the United States) and compared its results with other erosion vulnerability tools such as the Soil Vulnerability Index for Cultivated Cropland (SVI‐cc) and a GIS‐based Revised Universal Soil Loss Equation (RUSLE). The same erosion risk classes and ranges (low, moderate, moderately high and high) were implemented for all indexes. The advantages of the OFEtool compared to the SVI‐cc and RUSLE models are related to the use of an event‐based modelling approach, such as DEP, with updated soil loss estimates based on temporal changes in climate inputs and land use and management. The OFEtool uses a 6‐year time frame and a more up‐to‐date field inputs, while RUSLE provides a long‐term average and SVI‐cc only considers soil and topographical factors for risk assessment. Results indicated that the spatial distribution of vulnerable fields (and parts of the fields) followed a similar trend as other tested indices. However, the risk level associated with each tool differed (SVI‐cc > RUSLE > OFEtool). These differences could arise from intrinsic disparities within the tools (inputs, timing, processes considered, assumptions). While currently limited to the DEP domain and relying on the DEP random sampling scheme, further research is warranted to validate the tool at other Midwest locations and ensure it captures the watershed's landscape variability (combination of terrain, soil, land use and management) required to identifying critical erosion hotspots.","PeriodicalId":11408,"journal":{"name":"Earth Surface Processes and Landforms","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We evaluated the post‐fire sediment dynamics in beaver ponds to examine these ponds' contributions to sediment storage following disturbance. Beaver dams and beaver mimicry structures impound water and sediment, a function that is of growing interest in wildfire‐prone landscapes. Wildfires typically lead to high sediment loading into rivers in the years following fire, constituting a disturbance to aquatic ecosystems and a challenge to water resource managers. Previous work establishes that beaver dams trap substantial volumes of sediment, but sedimentation appears spatially and temporally heterogeneous and it remains unclear the extent to which short‐term pulses of sediment are attenuated by these structures. We examine the conditions under which beaver dams and beaver mimicry structures store post‐fire sediment by quantifying the sediment volume of 40 ponds, about half of which were burned in large wildfires in the Colorado and Wyoming Rocky Mountains in 2020. The median relative volume of burned ponds is 85%, which is greater than the median for unburned ponds (58%), meaning that burned ponds store higher relative volumes of sediment when pond size is accounted for. Furthermore, sediment accumulated at a median rate of 3.0 cm/year over the entire history of the pond. Post‐fire sedimentation rates, with a median of 20.4 cm/year, were an order of magnitude higher than pre‐fire rates with a median of 1.8 cm/year. In addition, vegetation and geomorphic characteristics correlated with sediment storage in ponds. Sediment surveys confirmed that ponds with greater surface areas contain higher volumes of sediment. Additionally, older ponds and ponds abandoned by beavers stored higher volumes of sediment compared to recently constructed ponds, ponds actively maintained by beaver, and beaver mimicry structures. These findings demonstrate that beaver ponds and mimicry structures may function as sediment sinks capable of attenuating post‐fire sediment. The biogeomorphic context, defined across multiple scales from the pond to the catchment, provides additional explanation for the wide range of sediment storage observed and remains an important consideration for beaver‐based restoration, catchment sediment management, and resilience evaluation.
{"title":"Post‐fire sediment attenuation in beaver ponds, Rocky Mountains, CO and WY, USA","authors":"Sarah B. Dunn, Sara L. Rathburn, Ellen Wohl","doi":"10.1002/esp.5970","DOIUrl":"https://doi.org/10.1002/esp.5970","url":null,"abstract":"We evaluated the post‐fire sediment dynamics in beaver ponds to examine these ponds' contributions to sediment storage following disturbance. Beaver dams and beaver mimicry structures impound water and sediment, a function that is of growing interest in wildfire‐prone landscapes. Wildfires typically lead to high sediment loading into rivers in the years following fire, constituting a disturbance to aquatic ecosystems and a challenge to water resource managers. Previous work establishes that beaver dams trap substantial volumes of sediment, but sedimentation appears spatially and temporally heterogeneous and it remains unclear the extent to which short‐term pulses of sediment are attenuated by these structures. We examine the conditions under which beaver dams and beaver mimicry structures store post‐fire sediment by quantifying the sediment volume of 40 ponds, about half of which were burned in large wildfires in the Colorado and Wyoming Rocky Mountains in 2020. The median relative volume of burned ponds is 85%, which is greater than the median for unburned ponds (58%), meaning that burned ponds store higher relative volumes of sediment when pond size is accounted for. Furthermore, sediment accumulated at a median rate of 3.0 cm/year over the entire history of the pond. Post‐fire sedimentation rates, with a median of 20.4 cm/year, were an order of magnitude higher than pre‐fire rates with a median of 1.8 cm/year. In addition, vegetation and geomorphic characteristics correlated with sediment storage in ponds. Sediment surveys confirmed that ponds with greater surface areas contain higher volumes of sediment. Additionally, older ponds and ponds abandoned by beavers stored higher volumes of sediment compared to recently constructed ponds, ponds actively maintained by beaver, and beaver mimicry structures. These findings demonstrate that beaver ponds and mimicry structures may function as sediment sinks capable of attenuating post‐fire sediment. The biogeomorphic context, defined across multiple scales from the pond to the catchment, provides additional explanation for the wide range of sediment storage observed and remains an important consideration for beaver‐based restoration, catchment sediment management, and resilience evaluation.","PeriodicalId":11408,"journal":{"name":"Earth Surface Processes and Landforms","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199195","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Large wood causes and responds to deposition and erosion within a river corridor. We focus on the anastomosing, gravel‐bed Swan River and two meandering, gravel‐bed tributaries in northwestern Montana, USA to explore the temporal dimensions of deposition and erosion associated with channel avulsions and island formation and to introduce the concept of wood levees. Channel avulsion represents isolation of part of the existing floodplain and formation of an anastomosing channel planform, with wood‐induced deposition at the point of channel bifurcation. Islands form at a wood jam that migrates upstream with time as sediment accumulates in the lee of the jam. The island creates only a local interruption of the single‐channel planform. We use tree‐ring and 14C dating to constrain wood‐induced island ages. We interpret the three wood‐induced forms of deposition and erosion that we describe here as reflecting a temporal continuum. Wood levees have primarily non‐woody vegetation and may be transient relative to the other features. Tributary islands appear to persist from a decade to over a century. Tree ages of 100–200 years at the floodplain avulsion site and the characteristics of the secondary channels suggest that these wood‐induced avulsion features can persist for more than a century. Understanding the temporal dynamics of wood‐induced features and spatial variation in erosion and deposition provides insight into the dynamics and spatial heterogeneity of natural river corridors, with implications for river restoration.
{"title":"Islands in the stream: Wood‐induced deposition and erosion in the river corridor","authors":"Anna Marshall, Ellen Wohl","doi":"10.1002/esp.5968","DOIUrl":"https://doi.org/10.1002/esp.5968","url":null,"abstract":"Large wood causes and responds to deposition and erosion within a river corridor. We focus on the anastomosing, gravel‐bed Swan River and two meandering, gravel‐bed tributaries in northwestern Montana, USA to explore the temporal dimensions of deposition and erosion associated with channel avulsions and island formation and to introduce the concept of wood levees. Channel avulsion represents isolation of part of the existing floodplain and formation of an anastomosing channel planform, with wood‐induced deposition at the point of channel bifurcation. Islands form at a wood jam that migrates upstream with time as sediment accumulates in the lee of the jam. The island creates only a local interruption of the single‐channel planform. We use tree‐ring and <jats:sup>14</jats:sup>C dating to constrain wood‐induced island ages. We interpret the three wood‐induced forms of deposition and erosion that we describe here as reflecting a temporal continuum. Wood levees have primarily non‐woody vegetation and may be transient relative to the other features. Tributary islands appear to persist from a decade to over a century. Tree ages of 100–200 years at the floodplain avulsion site and the characteristics of the secondary channels suggest that these wood‐induced avulsion features can persist for more than a century. Understanding the temporal dynamics of wood‐induced features and spatial variation in erosion and deposition provides insight into the dynamics and spatial heterogeneity of natural river corridors, with implications for river restoration.","PeriodicalId":11408,"journal":{"name":"Earth Surface Processes and Landforms","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142225585","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vanessa Gabel, Gregory E. Tucker, Benjamin Campforts
Gravel‐bed rivers that incise into bedrock are common worldwide. These systems have many similarities with other alluvial channels: they transport large amounts of sediment and adjust their forms in response to discharge and sediment supply. At the same time, the occurrence of bedrock incision implies behaviour that falls on a spectrum between fully detachment‐limited ‘bedrock channels’ and fully transport‐limited ‘alluvial channels’. Here, we present a mathematical model of river profile evolution that integrates bedrock erosion, gravel transport and the formation of channels whose hydraulic geometry is consistent with that of near‐threshold alluvial channels. We combine theory for five interrelated processes: bedload sediment transport in equilibrium gravel‐bed channels, channel width adjustment to flow and sediment characteristics, abrasion of bedrock by mobile sediment, plucking of bedrock and progressive loss of gravel‐sized sediment due to grain attrition. This model contributes to a growing class of models that seek to capture the dynamics of both bedrock incision and alluvial sediment transport. We demonstrate the model's ability to reproduce expected fluvial features such as inverse power law scaling between slope and area, and width and depth consistent with near‐threshold channel theory, and we discuss the role of sediment characteristics in influencing the mode of channel behaviour, erosional mechanism, channel steepness and profile concavity.
{"title":"A mathematical model for bedrock incision in near‐threshold gravel‐bed rivers","authors":"Vanessa Gabel, Gregory E. Tucker, Benjamin Campforts","doi":"10.1002/esp.5957","DOIUrl":"https://doi.org/10.1002/esp.5957","url":null,"abstract":"Gravel‐bed rivers that incise into bedrock are common worldwide. These systems have many similarities with other alluvial channels: they transport large amounts of sediment and adjust their forms in response to discharge and sediment supply. At the same time, the occurrence of bedrock incision implies behaviour that falls on a spectrum between fully detachment‐limited ‘bedrock channels’ and fully transport‐limited ‘alluvial channels’. Here, we present a mathematical model of river profile evolution that integrates bedrock erosion, gravel transport and the formation of channels whose hydraulic geometry is consistent with that of near‐threshold alluvial channels. We combine theory for five interrelated processes: bedload sediment transport in equilibrium gravel‐bed channels, channel width adjustment to flow and sediment characteristics, abrasion of bedrock by mobile sediment, plucking of bedrock and progressive loss of gravel‐sized sediment due to grain attrition. This model contributes to a growing class of models that seek to capture the dynamics of both bedrock incision and alluvial sediment transport. We demonstrate the model's ability to reproduce expected fluvial features such as inverse power law scaling between slope and area, and width and depth consistent with near‐threshold channel theory, and we discuss the role of sediment characteristics in influencing the mode of channel behaviour, erosional mechanism, channel steepness and profile concavity.","PeriodicalId":11408,"journal":{"name":"Earth Surface Processes and Landforms","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Kupferschmidt, A.D. Binns, K.L. Kupferschmidt, G.W. Taylor
SummaryText‐to‐image (TTI) generative models can be used to generate photorealistic images from a given text‐string input. However, the rapid increase in their use has raised questions about fairness and biases, with most research to date focusing on social and cultural areas rather than domain‐specific considerations. We conducted a case study for the Earth sciences, focusing on the field of fluvial geomorphology, where we evaluated subject‐area‐specific biases in the training data and downstream model performance of Stable Diffusion (v1.5). In addition to perpetuating Western biases, we found that the training data overrepresented scenic locations, such as famous rivers and waterfalls, and showed serious underrepresentation and overrepresentation of many morphological and environmental terms. Despite biassed training data, we found that with careful prompting, the Stable Diffusion model was able to generate photorealistic synthetic river images reproducing many important environmental and morphological characteristics. Furthermore, conditional control techniques, such as the use of condition maps with ControlNet, were effective for providing additional constraints on output images. Despite great potential for the use of TTI models in the Earth sciences field, we advocate for caution in sensitive applications and advocate for domain‐specific reviews of training data and image generation biases to mitigate perpetuation of existing biases.
{"title":"Stable rivers: A case study in the application of text‐to‐image generative models for Earth sciences","authors":"C. Kupferschmidt, A.D. Binns, K.L. Kupferschmidt, G.W. Taylor","doi":"10.1002/esp.5961","DOIUrl":"https://doi.org/10.1002/esp.5961","url":null,"abstract":"SummaryText‐to‐image (TTI) generative models can be used to generate photorealistic images from a given text‐string input. However, the rapid increase in their use has raised questions about fairness and biases, with most research to date focusing on social and cultural areas rather than domain‐specific considerations. We conducted a case study for the Earth sciences, focusing on the field of fluvial geomorphology, where we evaluated subject‐area‐specific biases in the training data and downstream model performance of Stable Diffusion (v1.5). In addition to perpetuating Western biases, we found that the training data overrepresented scenic locations, such as famous rivers and waterfalls, and showed serious underrepresentation and overrepresentation of many morphological and environmental terms. Despite biassed training data, we found that with careful prompting, the Stable Diffusion model was able to generate photorealistic synthetic river images reproducing many important environmental and morphological characteristics. Furthermore, conditional control techniques, such as the use of condition maps with ControlNet, were effective for providing additional constraints on output images. Despite great potential for the use of TTI models in the Earth sciences field, we advocate for caution in sensitive applications and advocate for domain‐specific reviews of training data and image generation biases to mitigate perpetuation of existing biases.","PeriodicalId":11408,"journal":{"name":"Earth Surface Processes and Landforms","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199203","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kristaps Lamsters, Jānis Karušs, Jurijs Ješkins, Pēteris Džeriņš, Shinta Ukai, Shin Sugiyama
Glaciers and ice caps surrounding the Greenland Ice Sheet are found to be sensitive to warming climate thus the knowledge of their thickness and internal structure is substantial to determine their future impact on sea level and local environment. Still, in situ glaciological measurements of such glaciers are very scarce. Here, we present the results of ground penetrating radar (GPR) and uncrewed aerial vehicle surveys conducted on the two southern outlet glaciers of Qaanaaq Ice Cap in NW Greenland. GPR measurements reveal up to 170 m thick ice and the lack of englacial hyperbolae indicating no developed en/subglacial drainage system. The glaciers consist mainly of radar transparent facies characteristic for cold ice, while limited scattering facies appear closer to the glacier's terminus beneath the thinnest ice and are attributed to debris inside the ice. Results show that the glaciers flow into narrow V‐shaped valleys suggesting spatio‐temporally limited subglacial erosion and restricted possible distribution of temperate ice in the past. The comparison of the ice thickness measurement data with global ice thickness model estimates shows considerable discrepancies emphasising the need of modelling improvements in the case of narrow valley and outlet glaciers.
格陵兰冰原周围的冰川和冰盖对气候变暖非常敏感，因此，了解它们的厚度和内部结构对确定它们未来对海平面和当地环境的影响非常重要。然而，对这类冰川的现场冰川学测量仍然非常稀少。在此，我们介绍了对格陵兰西北部 Qaanaaq 冰盖的两个南出口冰川进行的地面穿透雷达（GPR）和无人驾驶飞行器勘测的结果。GPR 测量显示，冰层厚达 170 米，而且没有冰川双峰，这表明没有发达的冰川内部/冰川下排水系统。冰川主要由冷冰特有的雷达透明面组成，而有限的散射面出现在最薄冰层下靠近冰川终点的地方，是冰层内部的碎屑造成的。结果表明，冰川流向狭窄的 V 形山谷，这表明冰川下侵蚀在时空上是有限的，过去温带冰的分布可能受到限制。冰层厚度测量数据与全球冰层厚度模型估计值的比较显示出相当大的差异，强调了改进窄谷和出口冰川模型的必要性。
{"title":"Geometry and thermal regime of the southern outlet glaciers of Qaanaaq Ice Cap, NW Greenland","authors":"Kristaps Lamsters, Jānis Karušs, Jurijs Ješkins, Pēteris Džeriņš, Shinta Ukai, Shin Sugiyama","doi":"10.1002/esp.5966","DOIUrl":"https://doi.org/10.1002/esp.5966","url":null,"abstract":"Glaciers and ice caps surrounding the Greenland Ice Sheet are found to be sensitive to warming climate thus the knowledge of their thickness and internal structure is substantial to determine their future impact on sea level and local environment. Still, <jats:italic>in situ</jats:italic> glaciological measurements of such glaciers are very scarce. Here, we present the results of ground penetrating radar (GPR) and uncrewed aerial vehicle surveys conducted on the two southern outlet glaciers of Qaanaaq Ice Cap in NW Greenland. GPR measurements reveal up to 170 m thick ice and the lack of englacial hyperbolae indicating no developed en/subglacial drainage system. The glaciers consist mainly of radar transparent facies characteristic for cold ice, while limited scattering facies appear closer to the glacier's terminus beneath the thinnest ice and are attributed to debris inside the ice. Results show that the glaciers flow into narrow V‐shaped valleys suggesting spatio‐temporally limited subglacial erosion and restricted possible distribution of temperate ice in the past. The comparison of the ice thickness measurement data with global ice thickness model estimates shows considerable discrepancies emphasising the need of modelling improvements in the case of narrow valley and outlet glaciers.","PeriodicalId":11408,"journal":{"name":"Earth Surface Processes and Landforms","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Andrew M. Tye, Kathryn A. Leeming, Mengyi Gong, Benjamin Marchant, Martin D. Hurst
The Coln is an ecologically sensitive river in a limestone dominated catchment with no major tributaries. Three in‐line turbidity sensors were installed to monitor changes in the dynamics of suspended sediment transport from headwaters to the confluence. The aims were to (i) provide estimates of yield (t km−2 year−1) and likely drivers of suspended sediment over ~3 years and (ii) assess turbidity dynamics during storm events in different parts of the catchment. In addition, the sensor installation allowed a novel wavelet analysis based on identifying groups of turbidity peaks to estimate transport times of suspended sediment through the catchment. Yearly suspended sediment yields calculated for the upper catchment were typically less than 4 t ha−1 year−1 being similar to other UK limestone or chalk‐based rivers. Time series autoregressive integrated moving average models including explanatory variable regression modelling indicated that river discharge, groundwater level and water temperature were all significant predictors of turbidity levels throughout the year. However, high model residuals demonstrate that the models failed to capture random turbidity events. Five parts of the time series data were used to examine sediment dynamics. Plots of scaled discharge verses turbidity demonstrated that in the upper catchment, after initial suspended sediment generation, sediment quickly became limited. In the lower catchment, hysteresis analysis suggested that sediment dilution occurred, due to increasing base flow. The novel wavelet analysis demonstrated that during winter ‘sediment events’ identified as groups of turbidity peaks, took ~18 h to pass from the first sensor in the upper catchment to the second sensor (10.3 km downstream of sensor 1) and 24 h to the third sensor (23.3 km from sensor 1). The work demonstrates the potential for using multiple turbidity sensors and time series statistical techniques in developing greater understanding of suspended sediment dynamics and associated poor water quality in ecologically sensitive rivers.
{"title":"Assessment of suspended sediment export and dynamics using in‐line turbidity sensors and time series statistical models","authors":"Andrew M. Tye, Kathryn A. Leeming, Mengyi Gong, Benjamin Marchant, Martin D. Hurst","doi":"10.1002/esp.5952","DOIUrl":"https://doi.org/10.1002/esp.5952","url":null,"abstract":"The Coln is an ecologically sensitive river in a limestone dominated catchment with no major tributaries. Three in‐line turbidity sensors were installed to monitor changes in the dynamics of suspended sediment transport from headwaters to the confluence. The aims were to (i) provide estimates of yield (t km<jats:sup>−2</jats:sup> year<jats:sup>−1</jats:sup>) and likely drivers of suspended sediment over ~3 years and (ii) assess turbidity dynamics during storm events in different parts of the catchment. In addition, the sensor installation allowed a novel wavelet analysis based on identifying groups of turbidity peaks to estimate transport times of suspended sediment through the catchment. Yearly suspended sediment yields calculated for the upper catchment were typically less than 4 t ha<jats:sup>−1</jats:sup> year<jats:sup>−1</jats:sup> being similar to other UK limestone or chalk‐based rivers. Time series autoregressive integrated moving average models including explanatory variable regression modelling indicated that river discharge, groundwater level and water temperature were all significant predictors of turbidity levels throughout the year. However, high model residuals demonstrate that the models failed to capture random turbidity events. Five parts of the time series data were used to examine sediment dynamics. Plots of scaled discharge verses turbidity demonstrated that in the upper catchment, after initial suspended sediment generation, sediment quickly became limited. In the lower catchment, hysteresis analysis suggested that sediment dilution occurred, due to increasing base flow. The novel wavelet analysis demonstrated that during winter ‘sediment events’ identified as groups of turbidity peaks, took ~18 h to pass from the first sensor in the upper catchment to the second sensor (10.3 km downstream of sensor 1) and 24 h to the third sensor (23.3 km from sensor 1). The work demonstrates the potential for using multiple turbidity sensors and time series statistical techniques in developing greater understanding of suspended sediment dynamics and associated poor water quality in ecologically sensitive rivers.","PeriodicalId":11408,"journal":{"name":"Earth Surface Processes and Landforms","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199200","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Since the timescale of a nebkha from the initial formation to the eventual destruction might be 1 to 200 years, little is known about the whole evolutionary path. In the phase of erosion and deflation, nebkhas are usually one source of aeolian sand and dust. Biocrust, a common living cover in arid and semiarid regions, could influence dune dynamic. In this study, the shear strength and hardness of the windward slope surface of erodible nebkhas are measured in the upwind margin of the Minqin oasis, China. It is found that both the shear strength and hardness of topsoil are commonly larger than these under the biocrust layer. From the force‐balance equation about the vane shear test, a novel expression for the shear strength of biocrust is derived. The field experiment in the windy season of 2023 shows that the biocrust layer of topsoil can effectively increase the resistance of nebkha surface against wind erosion. The relative larger strength and the self‐repair function of biocrust supported by the local non‐rain water are two main reasons the erodible nebkhas can exist for decades.
{"title":"Biocrust as a surface protection of erodible nebkhas","authors":"Ning‐Jing Tan, Xiao‐Mei Luo, Zhen‐Ting Wang","doi":"10.1002/esp.5958","DOIUrl":"https://doi.org/10.1002/esp.5958","url":null,"abstract":"Since the timescale of a nebkha from the initial formation to the eventual destruction might be 1 to 200 years, little is known about the whole evolutionary path. In the phase of erosion and deflation, nebkhas are usually one source of aeolian sand and dust. Biocrust, a common living cover in arid and semiarid regions, could influence dune dynamic. In this study, the shear strength and hardness of the windward slope surface of erodible nebkhas are measured in the upwind margin of the Minqin oasis, China. It is found that both the shear strength and hardness of topsoil are commonly larger than these under the biocrust layer. From the force‐balance equation about the vane shear test, a novel expression for the shear strength of biocrust is derived. The field experiment in the windy season of 2023 shows that the biocrust layer of topsoil can effectively increase the resistance of nebkha surface against wind erosion. The relative larger strength and the self‐repair function of biocrust supported by the local non‐rain water are two main reasons the erodible nebkhas can exist for decades.","PeriodicalId":11408,"journal":{"name":"Earth Surface Processes and Landforms","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142199201","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xuan Fang, Mingguo Peng, Yanzi Yan, Xia Xu, Jiaming Na
Terracing is an important measure to conserve water and soil on the Loess Plateau. Previous studies have showed that due to extreme rainstorms and a lack of maintenance, loess terraces have experienced degradation predominantly as collapses and sinkholes. Investigating the hydrological processes associated with terrace degradation is vital to understand terrace degradation mechanisms and maintain terraced landscape sustainability. Using a high‐resolution digital elevation model (DEM) based on unmanned aerial vehicle (UAV)remote sensing, as well as SIMulated Water Erosion (SIMWE) model, we explored the runoff–sediment dynamics on the terraced slopes on the Loess Plateau under rainstorm conditions and the terrace degradation patterns. The results showed that the dominant longitudinal water flow between terrace steps and converging lateral water flow along terrace surfaces indicate terrace ridge collapses and terrace surface sinkholes, respectively. Damaged areas exhibit high sediment flux and erosion potential. The water dynamics and degradation pattern were influenced by the original slope topography and terrace morphology. Specifically, most damages are distributed on concave slopes with concentrated water flow. In narrow terraces, under scattered longitudinal water flow, the dominant damages are ordinary collapses and the overall terraced topography tends to degrade into natural slopes. In wide terraces, concentrated longitudinal and well‐developed transverse water flows form a basic degradation pattern dominated by sinkhole‐induced collapses. This study verified the feasibility of SIMWE‐based hydrological simulation in assessing the degradation pattern of terraces on the Loess Plateau and demonstrated its potential for spatial scales and complex scenarios through compared with the soil moisture content (SMC)‐based method. The study concluded that the dominant runoff paths under the constraints of slope microtopography control the terrace degradation patterns. Our findings can serve as a theoretical basis for predicting hydrological hazards on terraces on the Loess Plateau and conducting a scientific design of terraces.
梯田是黄土高原水土保持的一项重要措施。以往的研究表明，由于极端暴雨和缺乏维护，黄土梯田出现了以崩塌和沉陷为主的退化现象。调查与梯田退化相关的水文过程对于了解梯田退化机制和保持梯田景观的可持续性至关重要。我们利用基于无人机遥感的高分辨率数字高程模型（DEM）和 SIMWE（SIMulated Water Erosion）模型，探讨了暴雨条件下黄土高原梯田坡面的径流-沉积动力学以及梯田退化模式。结果表明，阶梯之间的纵向水流和阶梯表面的横向水流汇聚分别表明了阶梯山脊坍塌和阶梯表面沉陷。受损区域表现出较高的沉积通量和侵蚀潜力。水流动力学和退化模式受到原始坡面地形和阶地形态的影响。具体来说，大部分损毁分布在水流集中的凹坡上。在狭窄的梯田中，在分散的纵向水流作用下，主要的破坏是普通塌方，梯田地形总体上趋向于退化为自然斜坡。在宽梯田中，集中的纵向水流和发达的横向水流形成了以沉井诱发的崩塌为主的基本退化模式。本研究验证了基于 SIMWE 的水文模拟在评估黄土高原梯田退化模式方面的可行性，并通过与基于土壤含水量（SMC）的方法进行比较，证明了其在空间尺度和复杂情况下的潜力。研究认为，在坡面微地形的限制下，主要径流路径控制着梯田退化模式。我们的研究结果可作为预测黄土高原梯田水文危害和科学设计梯田的理论依据。
{"title":"Runoff–sediment dynamics and degradation patterns in an abandoned terraced landscape on the Loess Plateau","authors":"Xuan Fang, Mingguo Peng, Yanzi Yan, Xia Xu, Jiaming Na","doi":"10.1002/esp.5960","DOIUrl":"https://doi.org/10.1002/esp.5960","url":null,"abstract":"Terracing is an important measure to conserve water and soil on the Loess Plateau. Previous studies have showed that due to extreme rainstorms and a lack of maintenance, loess terraces have experienced degradation predominantly as collapses and sinkholes. Investigating the hydrological processes associated with terrace degradation is vital to understand terrace degradation mechanisms and maintain terraced landscape sustainability. Using a high‐resolution digital elevation model (DEM) based on unmanned aerial vehicle (UAV)remote sensing, as well as SIMulated Water Erosion (SIMWE) model, we explored the runoff–sediment dynamics on the terraced slopes on the Loess Plateau under rainstorm conditions and the terrace degradation patterns. The results showed that the dominant longitudinal water flow between terrace steps and converging lateral water flow along terrace surfaces indicate terrace ridge collapses and terrace surface sinkholes, respectively. Damaged areas exhibit high sediment flux and erosion potential. The water dynamics and degradation pattern were influenced by the original slope topography and terrace morphology. Specifically, most damages are distributed on concave slopes with concentrated water flow. In narrow terraces, under scattered longitudinal water flow, the dominant damages are ordinary collapses and the overall terraced topography tends to degrade into natural slopes. In wide terraces, concentrated longitudinal and well‐developed transverse water flows form a basic degradation pattern dominated by sinkhole‐induced collapses. This study verified the feasibility of SIMWE‐based hydrological simulation in assessing the degradation pattern of terraces on the Loess Plateau and demonstrated its potential for spatial scales and complex scenarios through compared with the soil moisture content (SMC)‐based method. The study concluded that the dominant runoff paths under the constraints of slope microtopography control the terrace degradation patterns. Our findings can serve as a theoretical basis for predicting hydrological hazards on terraces on the Loess Plateau and conducting a scientific design of terraces.","PeriodicalId":11408,"journal":{"name":"Earth Surface Processes and Landforms","volume":null,"pages":null},"PeriodicalIF":3.3,"publicationDate":"2024-08-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142198965","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：