Geomorphology最新文献_第2页

Predicting urban channel morphology amidst multiple complexities 在多重复杂性中预测城市河道形态

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2024-11-12 DOI: 10.1016/j.geomorph.2024.109511

Lukman A. Soboyejo, Kathryn L. Russell, Tim D. Fletcher

Urbanisation has resulted in rapid geomorphic changes and ecosystem degradation in many streams worldwide. The question of how channel response to urbanisation can be accurately predicted amid multiple driving factors remains a significant scientific challenge. Numerous efforts have been made to address this issue over the past 80 years. Nevertheless, channel response resulting from urbanisation differs across physiographic regions, making it difficult to predict. The main goal of this study is to investigate the most important factors influencing morphological changes, such as channel area, in streams with urbanised catchments. To accomplish this aim, we reviewed the literature on the application of hydraulic geometry models to urban-impacted rivers worldwide. We set out to investigate two specific questions: (i) to what extent and under what circumstances can urban stream bankfull cross-sectional area be predicted by catchment area and impervious cover metrics? and (ii) is stream bankfull width more susceptible than stream bankfull depth to urban-induced enlargement? However, over 90 % of the urban channels studied in the literature we reviewed showed irregular response patterns to urbanisation, owing to the complex interplay of local factors, such as geology, sediment, hardpoints, and riparian vegetation. Our most important conclusion is that local context is an important controller of stream channel response to urbanisation. While catchment area is a good predictor of channel area in some urban sites, it is a poor predictor of channel area in other urban sites. This contrasts with non-urban sites, where catchment area usually predicts channel area more strongly. In addition, impervious cover alone, which represents the direct hydrological impact of urbanisation, is insufficient to fully explain channel enlargement and incision. Therefore, models of channel response to urbanisation must consider the specific local factors that drive or limit these responses in order to be effective as predictive and explanatory tools.

城市化导致全球许多河流的地貌迅速变化和生态系统退化。在多种驱动因素的作用下，如何准确预测河道对城市化的反应仍然是一个重大的科学挑战。在过去的 80 年中，人们为解决这一问题做出了大量努力。然而，城市化导致的河道响应在不同的地理区域存在差异，因此难以预测。本研究的主要目标是调查影响城市化集水区河道面积等形态变化的最重要因素。为了实现这一目标，我们查阅了有关将水力几何学模型应用于全球受城市影响河流的文献。我们着手研究两个具体问题：(i) 在何种程度上和何种情况下，城市河流的河岸横截面积可以通过集水面积和不透水覆盖率指标进行预测？ (ii) 与河岸深度相比，河岸宽度是否更容易受到城市引起的河道扩大的影响？然而，由于地质、沉积物、硬点和河岸植被等当地因素的复杂相互作用，在我们查阅的文献中，超过 90% 的城市河道对城市化的反应模式不规则。我们最重要的结论是，当地环境是河道对城市化反应的重要控制因素。在某些城市地区，集水区可以很好地预测河道面积，但在其他城市地区，集水区却不能很好地预测河道面积。这与非城市地区形成了鲜明对比，在非城市地区，集水面积通常能更准确地预测河道面积。此外，仅仅是不透水覆盖（代表城市化的直接水文影响）还不足以完全解释河道的扩大和内切。因此，河道对城市化反应的模型必须考虑驱动或限制这些反应的当地特定因素，才能有效地作为预测和解释工具。

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引用次数: 0

Topographic ridges express late Quaternary faulting peripheral to the New Madrid seismic zone, intraplate USA: Their tectonic implications 美国板块内新马德里地震带外围第四纪晚期断层的地形山脊：其构造影响

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2024-11-08 DOI: 10.1016/j.geomorph.2024.109502

S. Pinardi , R.T. Cox , D. Leslie , Md.R. Hasan , N. Adhikari , R.B. Van Arsdale

Northeast-trending linear topographic ridges in Pliocene and Quaternary sediments adjacent to the New Madrid seismic zone (NMSZ), intraplate North America, have been long speculated to be neotectonic landforms related to reactivation of basement faults of the eastern Mississippi Valley Rift margin. Earthquake epicenters and paleoseismological studies show that eastern rift margin faults (ERMF) were active during late Quaternary south of a restraining bend in the Mississippi Valley Rift fault complex, but the ERMF zone north of the restraining bend (ERM-N) and underlying the linear ridges is seismically quiescent. A previous P-wave seismic reflection survey across the most prominent linear ridge (Rives lineament) revealed that it overlies a horst in Eocene sediment. To ascertain whether the Rives lineament could have been produced by surface faulting/folding, we collected electrical resistivity tomography (ERT) and ground penetrating radar (GPR) profiles to image the ridge's shallow subsurface features. We interpret shallow folding and faulting of late Pleistocene sediment in our ERT and GPR images. Additionally, convexity of multiple topographic profiles of scarps along margins of the Rives lineament was quantified and compared to the convexity of profiles of known neotectonic scarps and of fluvial terrace riser profiles within the region. Comparison of these profiles reveals a high degree of similarity between the scarps along the Rives lineament margins and the Holocene Reelfoot thrust scarp. When combined, our results strongly suggest late Pleistocene or Holocene folding and faulting created this ridge despite its current seismic quiescence, and thus they provide useful insight for assessing the seismic hazard potential of quiescent faults in strike-slip systems in general. We conclude that the late Quaternary series of movements documented on the Reelfoot thrust was initiated to accommodate crustal shortening after transpressional fault movements on the ERM-N became inactive in late Pleistocene or early Holocene and that movement along the ERM-N may resume if the Reelfoot thrust has an interval of inactivity in the future. Our results suggest how fault interactions within a strike-slip system can change, making faults with significant amounts of seismic potential appear as though they are inactive.

长期以来，人们一直推测毗邻北美板块内部新马德里地震带（NMSZ）的上新世和第四纪沉积物中的东北走向线状地形山脊是与密西西比河谷裂谷东缘基底断层重新活化有关的新构造地貌。地震震中和古地震学研究表明，密西西比河谷裂谷断裂复合体约束弯以南的东部裂谷边缘断层（ERMF）在第四纪晚期十分活跃，但约束弯以北的ERMF区（ERM-N）和线性山脊下层则处于地震静止状态。之前对最突出的线性山脊（里夫线）进行的 P 波地震反射勘测显示，该山脊覆盖在始新世沉积物的一个地角之上。为了确定里夫斯线状构造是否由地表断层/褶皱产生，我们采集了电阻率层析成像（ERT）和地面穿透雷达（GPR）剖面图，对该脊的浅表次表层特征进行成像。我们在 ERT 和 GPR 图像中解释了晚更新世沉积物的浅层褶皱和断层。此外，我们还对里夫斯线边缘疤痕的多个地形剖面的凸度进行了量化，并将其与该地区已知新构造疤痕和河流阶地隆起剖面的凸度进行了比较。对这些剖面进行比较后发现，里夫斯褶皱带边缘的疤痕与全新世的里尔富特推力疤痕具有高度的相似性。综合这些结果，我们强烈认为晚更新世或全新世的褶皱和断层造成了这一山脊，尽管它目前处于地震静止状态，因此它们为评估一般走向滑动系统中静止断层的地震危险潜力提供了有用的见解。我们的结论是，记录在案的第四纪晚期里尔富特推力上的一系列运动是在更新世晚期或全新世早期ERM-N上的转压断层运动不活跃之后为适应地壳缩短而开始的，如果里尔富特推力在未来有一段时间不活跃，ERM-N上的运动可能会恢复。我们的研究结果表明，走向滑动系统中的断层相互作用可能会发生变化，从而使具有巨大地震潜力的断层看起来似乎处于不活跃状态。

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引用次数: 0

Applying geoarchaeological principles to marine archaeology: A new reappraisal of the “first marine” and “in-situ” lithic scatters, Murujuga (Dampier Archipelago), NW Australia 将地质考古学原理应用于海洋考古：对澳大利亚西北部穆鲁朱加（丹皮尔群岛）"第一海洋 "和 "原地 "碎石散落的新评价

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2024-11-08 DOI: 10.1016/j.geomorph.2024.109494

Piers Larcombe , Peter J. Ross , Chris Fandry

The absence or paucity of known underwater cultural heritage (UCH) sites on the Australian inner shelf stands in stark contrast to the thousands of sites revealed elsewhere in the world. A series of papers have asserted the first in situ (i.e., primary context) UCH sites in the shallow waters of Murujuga (Dampier Archipelago), NW Australia, each arguing the stone artefact scatters are at least 7000 years old and are now submerged because of Post-Glacial sea-level rise. Subsequent papers presented new data and repeated these claims. We present new hydrodynamic modelling and data on coastal erosion and bathymetry, and re-assess each sites' sedimentary setting and archaeological site-formation history.

The arguments for these sites being of primary context and reflecting Early Holocene land surfaces are unfounded, and at best untested. All artefacts are of unknown age, and many or all are likely to have been reworked, including the subtidal artefacts in Flying Foam Passage. Such sites of secondary context, if treated appropriately, can inform our understanding of site-formation processes, and may support more powerful contributions to submerged archaeology than attempts to seek the first or the oldest.

澳大利亚内陆架上没有或很少有已知的水下文化遗产（UCH）遗址，这与世界其他地方发现的数以千计的遗址形成了鲜明对比。一系列论文声称，澳大利亚西北部穆鲁朱加（丹皮尔群岛）浅水区发现了首个原地（即原生环境）水下文化遗产遗址，每篇论文都认为这些石器散落点至少有 7000 年的历史，现在由于冰川期后海平面上升而被淹没。随后的论文提供了新的数据，并重复了这些说法。我们提出了新的水动力模型以及海岸侵蚀和水深测量数据，并重新评估了每个遗址的沉积环境和考古遗址形成史。所有出土文物的年代都不清楚，许多或所有出土文物都可能经过了再加工，包括飞沫通道的潮下带出土文物。如果处理得当，这些次生遗址可以帮助我们了解遗址的形成过程，并为水下考古学做出比寻找最早或最古老遗址更有力的贡献。

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引用次数: 0

Channel breakdown and avulsion in arroyos feeding the Little Colorado River, Arizona, USA 美国亚利桑那州小科罗拉多河溪谷的河道破裂和崩塌

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2024-11-07 DOI: 10.1016/j.geomorph.2024.109501

B.P. Graves , T.J. Ralph , A.M. Morgan

Improved knowledge regarding dryland river character and behaviour is important as the increasing threats of climate change and anthropogenic activities exacerbate water security issues in channels prone to discontinuity and termination. Dryland river character and behaviour is determined by a complex and dynamic interplay between extrinsic controls and intrinsic processes. Polacca and Oraibi Wash are two discontinuous dryland rivers, tributaries of the Little Colorado River in semi-arid, north-eastern Arizona, USA. Valley-scale morphometrics and downstream longitudinal trends were derived from remote sensing and geospatial analyses, hydraulic modelling, and field measurements, to assess the key controls, patterns, and processes driving channel diminution and discontinuity. Both rivers are entrenched along most of their valleys and experience downstream hydro-geomorphic changes as valley confinement eases in their low gradient floodplains. The rivers exhibit non-equilibrium responses to a concomitant decline in calculated discharge (from ∼82 to <4 m³ s⁻¹), stream power (from ∼334 to <5 W m⁻²), and channel cross-sectional area (from ∼82 to <3 m²), which are the principal factors contributing to channel breakdown and the development of broad floodouts. Small distributary channels and avulsions are evident in the lowland reaches where channel discontinuity occurs, with a dominance of knickpoints in distal floodout reaches as they attempt to re-establish channel continuity. Using historical aerial imagery we show that knickpoint headcut retreat rates have ranged from ∼1.7 to 53 m a⁻¹. Channel breakdown patterns and processes in the Polacca and Oraibi Washes are similar to other dryland rivers around the world, and reveal common underlying factors that are central to river termination and reformation. This study reveals a combination of intrinsic erosion and sedimentation processes and avulsion threshold responses that trigger channel adjustment resulting from downstream fluvial decline. However, key extrinsic controls, such as valley confinement and hydroclimate, influence and limit the rate and nature of these adjustments. Early recognition of these geomorphic changes can inform river, land, and water management strategies across the American southwest.

气候变化和人为活动的威胁日益严重，加剧了易发生断流和终止的河道的水安全问题，因此，提高对旱地河流特征和行为的认识非常重要。旱地河流的特征和行为是由外在控制和内在过程之间复杂而动态的相互作用决定的。Polacca 和 Oraibi Wash 是两条不连续的旱地河流，是美国亚利桑那州东北部半干旱地区小科罗拉多河的支流。通过遥感和地理空间分析、水力模型和实地测量，得出了河谷尺度的形态计量学和下游纵向趋势，以评估驱动河道缩小和不连续的关键控制因素、模式和过程。这两条河流的大部分河谷都有淤积，随着低坡度洪泛区河谷淤积的缓解，下游的水文地质也会发生变化。这两条河流的计算排泄量（从 82 m3 s-1 到 4 m3 s-1）、水流功率（从 334 W m-2 到 5 W m-2）和河道横截面积（从 82 m2 到 3 m2）都出现了非均衡反应，这是导致河道断裂和大面积洪泛的主要因素。在发生河道断裂的低洼地段，小的支流河道和崩塌非常明显，而在洪水泛滥的远端，由于试图重建河道的连续性，则以节理点为主。我们利用历史航拍图像显示，戗点顶切的后退速度在 1.7 至 53 米/秒之间。波拉克卡和奥赖比冲沟的河道断裂模式和过程与世界上其他旱地河流相似，揭示了河流终止和改造的共同基本因素。这项研究揭示了内在侵蚀和沉积过程与崩塌阈值反应的结合，它们触发了河道调整，导致下游河道衰退。然而，河谷封闭性和水文气候等关键的外在控制因素也会影响和限制这些调整的速度和性质。及早认识到这些地貌变化可以为美国西南部的河流、土地和水资源管理策略提供参考。

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引用次数: 0

Recognition of palaeo-glacial troughs with cirques on parts of Tibetan Plateau using multi-modal datasets with deep learning models 利用多模态数据集和深度学习模型识别青藏高原部分地区的古冰川槽与圈层

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2024-11-06 DOI: 10.1016/j.geomorph.2024.109499

Chenhe Zhu , Fei Guo , Zhigang Zhang , Mingyuan Xu , Hong Zhang , Yiman Li , Shilong Li

Recognition of landforms associated with past glaciation is crucial for understanding past ice dynamics and their relationship to climate. With the development of artificial intelligence technology, deep learning techniques have assisted in the automatic extraction of glacial landforms, but these methods still face problems of low precision and weak transferability. This study proposes a new method named geomorphology-attention DeeplabV3+ (GA-DeeplabV3+) model. This method adds spatial attention and channel attention modules based on the DeeplabV3+ network and utilizes a combination of multi-modal geographic data. Verification shows that the model proposed in this paper significantly enhances the recognition precision of glacial troughs with cirques compared to existing models, reaching a Mean Intersection over Union (MIoU) of 86.2% and a mean Pixel Accuracy (mPA) of 90.64% in the area of the Palaeo-Daocheng ice cap. In addition, validation experiments were conducted in the Peiku Gangri region and the Tenasserim mountains, achieving MIoU scores of 70.09% and 73.28% respectively. This accomplishment represents a vital stride towards automating the extraction of palaeo-glacial landforms, which holds great significance for analyzing the scale and evolution of ancient glaciers.

识别与过去冰川作用相关的地貌对于了解过去的冰川动力学及其与气候的关系至关重要。随着人工智能技术的发展，深度学习技术为冰川地貌的自动提取提供了帮助，但这些方法仍面临精度低、可移植性弱等问题。本研究提出了一种新方法，命名为地貌注意 DeeplabV3+（GA-DeeplabV3+）模型。该方法在 DeeplabV3+ 网络的基础上增加了空间注意力和通道注意力模块，并综合利用了多模态地理数据。验证结果表明，与现有模型相比，本文提出的模型显著提高了带圈层冰川槽的识别精度，在古稻城冰盖地区的平均交叉率（MIoU）达到 86.2%，平均像素精度（mPA）达到 90.64%。此外，还在培古岗日地区和特纳塞林山脉进行了验证实验，MIoU 分数分别达到 70.09% 和 73.28%。这一成果标志着古冰川地貌提取自动化迈出了重要一步，对分析古冰川的规模和演化具有重要意义。

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引用次数: 0

Pothole formation on Rock Window Mesa, Chinle valley, AZ 亚利桑那州钦莱山谷岩窗梅萨形成的坑洞

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2024-11-06 DOI: 10.1016/j.geomorph.2024.109498

Monte Fleming , Cornelis Bootsman , Norman Moll , Leonard Brand

In areas of the Colorado Plateau, rock basins, or potholes, occur in abundance. Because of their impressive size and often enigmatic location, their presence begs an explanation. Our goal in undertaking this research is to suggest a model for the origin of Rock Window Mesa's potholes, by which we might better interpret the geomorphological history of the mesa and Chinle Valley. Data collection consisted of both field work and analysis of a high-resolution 3D point cloud of the mesa. The southern and western edges of the mesa, closest to the Chinle Wash, and close to where knickpoints may have been, are the areas of highest pothole density. The pothole-forming processes disrupted drainage systems, and pothole sizes do not correlate with the catchment areas of the potholes. There are abundant, fluvially deposited erratic pebbles and cobbles on the mesa, and the joints and cracks that are present in the bedrock exert little to no control over pothole morphology. These data suggest that the potholes were formed subaqueously. A proposal that may point us to a possible mechanism is that similar potholes, in the Navajo Sandstone exposed in the Henry Mountains, appear to have been formed via fluvial processes in over-steepened tributary junctions. At our research location, the water that carved out the potholes appears to have come from ENE, and the point at which this water met the Chinle Wash may have been over-steepened as a result of rapid incision of the Chinle Wash through the poorly lithified Navajo Sandstone.

在科罗拉多高原的一些地区，岩石盆地或洼地大量出现。由于它们的大小令人印象深刻，位置也往往令人费解，因此它们的存在需要一个解释。我们开展这项研究的目的是为岩窗山丘洼地的起源提出一个模型，从而更好地解释该山丘和钦莱山谷的地貌历史。数据收集工作包括实地考察和分析岩窗台的高分辨率三维点云。台地的南边和西边最靠近钦莱冲沟，也靠近可能曾有疙瘩的地方，是坑洞密度最高的区域。坑洞的形成过程破坏了排水系统，坑洞的大小与坑洞的集水区域并不相关。台地上有大量经冲积而成的鹅卵石和卵石，基岩中存在的节理和裂缝对坑洞形态几乎没有控制作用。这些数据表明，坑洞是在水下形成的。亨利山脉出露的纳瓦霍砂岩中也有类似的洼坑，这些洼坑似乎是在过度陡峭的支流交汇处通过河流过程形成的。在我们的研究地点，凿出洼坑的水流似乎来自东偏东方向，而这些水流与钦勒冲沟的交汇点可能由于钦勒冲沟快速切入岩性较差的纳瓦霍砂岩而过度陡峭。

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引用次数: 0

Cross-shore profile evolution induced by real emergent vegetation in a sandbar-lagoon coast: Laboratory experiments 沙洲-泻湖海岸真实新生植被诱发的跨岸剖面演变：实验室实验

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2024-11-06 DOI: 10.1016/j.geomorph.2024.109500

Cuiping Kuang , Xin Cong , Lixin Gong , Jiantao Liu , Xuejian Han , Wei Xing

Pressures from anthropogenic activities and climate change in lagoon ecosystems have increased rapidly in recent years. Coastal vegetation serves as a natural sea defense mechanism and is pivotal in maintaining a robust ecological balance. However, our understanding of how vegetation influences the evolution of typical sandbar-lagoon coasts is limited. To address this gap, a series of mobile-bed flume experiments were conducted within a typical sandbar-lagoon cross-section to investigate the impact of sparse Phragmites spp. planted on the sandbar on wave propagation and the evolution of the cross-shore profile under varying water depths and irregular wave conditions. These findings revealed that vegetation attenuates infragravity and sea-swell waves. Notably, infragravity waves are associated with the formation of a right- or obtuse-angled foredune scarp, whereas sea-swell waves tend to create an acute-angled scarp. Vegetation-induced changes in the local amplitudes of short waves within wave groups and the local mean water level are instrumental in reshaping foredune scarps. Additionally, the cross-shore width of the vegetation had a more pronounced influence on sediment transport within the lagoon than that of the solid volume fraction. Sparse vegetation not only reduces sediment deposition in the lagoon but also enhances offshore sediment transport. These insights significantly advance our understanding of wave-vegetation-sediment dynamics and provide essential scientific support for the implementation of coastal ecological restoration initiatives, particularly in the context of sandbar-lagoon coasts.

近年来，人为活动和气候变化对泻湖生态系统造成的压力迅速增加。海岸植被是一种天然的海防机制，在维持稳健的生态平衡方面起着举足轻重的作用。然而，我们对植被如何影响典型沙洲-泻湖海岸演变的了解十分有限。为了填补这一空白，我们在典型的沙洲-泻湖断面上进行了一系列移动水槽实验，研究在不同水深和不规则波浪条件下，沙洲上种植的稀疏葭藻对波浪传播和跨岸剖面演变的影响。这些研究结果表明，植被可减弱次重力波和海涌波。值得注意的是，次重力波与直角或钝角前沙丘疤痕的形成有关，而海涌波则倾向于形成锐角疤痕。植被引起的波群内短波局部振幅的变化和局部平均水位的变化有助于重塑前沙丘疤痕。此外，与固体体积分数相比，植被的跨岸宽度对泻湖内沉积物迁移的影响更为明显。稀疏的植被不仅能减少泻湖内的沉积物沉积，还能增强离岸沉积物的迁移。这些见解极大地推动了我们对波浪-植被-沉积物动力学的理解，为实施海岸生态恢复计划，尤其是沙洲-泻湖海岸的生态恢复计划提供了重要的科学支持。

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引用次数: 0

Surface exposure ages of middle–late Pleistocene marine and fluvial terraces along the northern and southern Sanriku coasts, Northeast Japan 日本东北部三陆北部和南部海岸中更新世晚期海洋和河流阶地的地表暴露年龄

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2024-11-04 DOI: 10.1016/j.geomorph.2024.109497

Sachi Wakasa , Tatsuya Ishiyama , Daisuke Hirouchi , Nobuhisa Matta , Natsuko Fujita , Tomoo Echigo

To estimate long-term rates of coastal uplift along the northern Pacific coast of Northeast Japan, we determined the surface exposure ages of marine and fluvial terraces based on terrestrial in situ cosmogenic radionuclide dating of exposed bedrock surfaces. Based on reinterpretation of marine and fluvial terraces, we collected samples from the northern and southern Sanriku coast. The surface exposure ages from ¹⁰Be concentrations in quartz calculated from the measured ¹⁰Be/⁹Be ratios commonly suggest MIS 5 and MIS 7 for the marine and fluvial terraces and averaged coastal uplift rates of ca. 0.25 ± 0.15 and 0.4 mm/yr along the northern and southern Sanriku coast at intermediate timescales. The results may demonstrate different styles of crustal strain accommodation in the northern Northeast Japan arc above the subducting Pacific plate.

为了估算日本东北部北太平洋沿岸的长期海岸隆升速率，我们根据暴露基岩表面的陆地原位宇宙放射性核素测年法，确定了海洋和河流阶地的地表暴露年龄。根据对海洋和河流阶地的重新解释，我们在三陆海岸北部和南部采集了样本。根据测得的 10Be/9Be 比率计算出的石英中 10Be 浓度所得出的地表暴露年龄通常表明，海洋阶地和河川阶地的年代为 MIS 5 和 MIS 7，三陆海岸北部和南部的平均海岸隆升速率为大约 0.25 ± 0.15 和 0.4 毫米/年（中时间尺度）。这些结果可能表明，俯冲太平洋板块之上的日本东北弧北部地壳应变容纳方式不同。

引用次数: 0

Relating ten years of rock temperature monitoring to rockwall weathering processes in steep mountain valleys in western Norway 将十年的岩石温度监测与挪威西部陡峭山谷的岩壁风化过程联系起来

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2024-11-03 DOI: 10.1016/j.geomorph.2024.109496

Katja Laute, Achim A. Beylich

Most existing studies on rockwall frost regimes and frost weathering at rockwalls focus on permafrost-affected rockwalls. However, a high share of rockwall surface areas in Norway and in many other cold-climate environments is actually free of permafrost. It is therefore of interest how these permafrost-free rockwall systems will respond to future changes in air and rock temperatures. In this study, we report field measurements conducted at rockwalls beneath the current permafrost limit and investigate thermal regimes at rockwalls that include both rockwall areas with and without permafrost. We present a unique dataset of up to ten years of rockwall temperature measurements from ten temperatures sensors installed in two mountain valleys in western Norway. An analysis of the different rockwall thermal regimes with respect to rock weathering and associated rockfall supply for both, permafrost-affected and permafrost-free rockwalls is provided. The highest intensity of recent rockwall weathering including determined rockwall retreat rates and associated rockfall supply is detected for northeast-facing rockwalls followed by south-facing rockwalls in our study area. Frost cracking activity, probably in the form of segregation ice growth, seems to be an important factor particularly for the high weathering intensity on northeast-facing rockwalls whereas solar radiation-induced thermal stresses, which favour incremental subcritical crack growth, is assumed to play a relevant role in the moderate weathering intensity on south- and southwest-facing rockwalls. A mean annual and study area-wide rockwall retreat rate of 0.24 mm yr⁻¹ is estimated for our ten-year investigation period (2010−2020) which is comparable to other published rates in similar lithologies and climates. As it can be assumed that seasonal frost regimes and permafrost will react differently to ongoing and future climate changes, more attention should be paid to analyse these two different thermal regimes with respect to possible varied implications for mechanical rockwall weathering and associated rockfall supply.

关于岩壁霜冻机制和岩壁霜冻风化的现有研究大多集中在受永久冻土影响的岩壁上。然而，在挪威和其他许多寒冷气候环境中，有很大一部分岩壁表面实际上是没有永久冻土的。因此，这些无永久冻土的岩壁系统将如何应对未来空气和岩石温度的变化是一个令人感兴趣的问题。在本研究中，我们报告了在当前永久冻土极限下的岩壁进行的实地测量，并研究了岩壁的热机制，包括有永久冻土和无永久冻土的岩壁区域。我们展示了一个独特的岩壁温度测量数据集，该数据集由安装在挪威西部两个山谷中的十个温度传感器提供，时间长达十年。我们分析了受永久冻土影响的岩壁和无永久冻土的岩壁在岩石风化和相关落石供应方面的不同岩壁热机制。在我们的研究区域，东北面岩壁的近期岩壁风化强度最高，包括确定的岩壁退缩率和相关的落石供应量，其次是南面岩壁。冻裂活动（可能以离析冰生长的形式出现）似乎是东北向岩壁风化强度较高的一个重要因素，而太阳辐射引起的热应力有利于增量亚临界裂缝的生长，被认为是南向和西南向岩壁风化强度适中的一个相关因素。据估计，在我们的十年调查期（2010-2020 年）内，整个研究区域的岩壁年平均退缩率为 0.24 mm/yr-1，与其他已公布的类似岩性和气候条件下的退缩率相当。可以认为，季节性霜冻机制和永久冻土将对当前和未来的气候变化做出不同的反应，因此应更加重视分析这两种不同的热机制对岩壁机械风化和相关落石供应可能产生的不同影响。

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引用次数: 0

Numerical investigation of the refractive properties of near-horizontal rocky shore platforms and their effects on harmonic and stationary wave patterns 近水平岩岸平台的折射特性及其对谐波和静波模式影响的数值研究

IF 3.1 2区地球科学 Q2 GEOGRAPHY, PHYSICAL

Geomorphology

Pub Date : 2024-11-03 DOI: 10.1016/j.geomorph.2024.109491

R.L. Krier-Mariani , W.J. Stephenson , S. Wakes , M.E. Dickson

Near-horizontal shore platforms display highly irregular plan shapes, but little is known about the way in which these irregularities influence the significant wave height (

\hat{H_{s}}

) on the platforms and the frequency components of the nearshore wavefield. As ocean waves share akin refractive properties to light rays, it can be assumed that, similarly to optical lenses, shore platforms can separate waves according to their frequency depending on their geometry. Thus, we use a non-linear Boussinesq wave model to conduct harmonic and bispectral mode decomposition analyses to study the control of concave and convex platform edges over wind waves (WW: 0.125–0.33 Hz), swell waves (SW: 0.05–0.125 Hz) and infragravity (IG: 0.008–0.05 Hz) waves frequencies. For breaking and non-breaking waves, increasing the platform edge concavity intensified wave divergence and subsequent attenuation of SW and IG across the outer platforms, reducing

\hat{H_{s}}

by up to 25 %. Increasing the platform edge convexity intensified focusing and amplification of SW and WW over the outer platforms, increasing

\hat{H_{s}}

by up to 18 % and 55 % for breaking and non-breaking waves. In the presence of breaking, IG amplification was affected by wave divergence across the inner platform, a condition determined by a critical convex curvature threshold (

(K)

=1.8) balancing wave focusing from refraction and defocusing from breaking. We find that convex curvature can determine the relative dominance of WW, SW and IG across platforms. Alongshore, coherent wave interactions governed IG stationary patterns defined by a node near the platform centreline and two antinodes on either side of concave edges. A node was generated at the platform centreline, and two antinodes were observed on either side of the convex edges for

(K)

>1.8, with the opposite pattern observed for

(K)

<1.8. Such patterns likely result in alongshore variations in wave-generated currents and erosion shaping rock coasts.

近水平海岸平台的平面形状极不规则，但人们对这些不规则性如何影响平台上的显著波高（Hŝ）以及近岸波场的频率成分知之甚少。由于海浪与光线具有相似的折射特性，因此可以假定，与光学透镜类似，海岸平台可以根据其几何形状按频率分离海浪。因此，我们使用非线性布森斯克波模型进行谐波和双谱模式分解分析，研究凹凸平台边缘对风浪（WW：0.125-0.33 Hz）、涌浪（SW：0.05-0.125 Hz）和次重力波（IG：0.008-0.05 Hz）频率的控制。对于断裂波和非断裂波，增加平台边缘凹度会加强波的发散，进而削弱外平台上的 SW 波和 IG 波，使 Hŝ 降低达 25%。增加平台边缘凸度会加强外平台上 SW 波和 WW 波的聚焦和放大，使 Hŝ在破浪和非破浪时分别增加 18%和 55%。在有破波的情况下，IG 的放大受波浪在内部平台发散的影响，这一条件由临界凸曲率阈值（K=1.8）决定，该阈值平衡了折射产生的波浪聚焦和破波产生的波浪散焦。我们发现，凸曲率可决定跨平台的 WW、SW 和 IG 的相对优势。在沿岸，相干波的相互作用支配着由平台中心线附近的一个节点和凹边两侧的两个反节点所定义的 IG 固定模式。K>1.8 时，在平台中心线处产生一个节点，在凸边两侧观察到两个反节点，K<1.8 时则观察到相反的模式。这种模式可能是波浪产生的水流沿岸变化和侵蚀岩石海岸的结果。

{"title":"Numerical investigation of the refractive properties of near-horizontal rocky shore platforms and their effects on harmonic and stationary wave patterns","authors":"R.L. Krier-Mariani , W.J. Stephenson , S. Wakes , M.E. Dickson","doi":"10.1016/j.geomorph.2024.109491","DOIUrl":"10.1016/j.geomorph.2024.109491","url":null,"abstract":"<div><div>Near-horizontal shore platforms display highly irregular plan shapes, but little is known about the way in which these irregularities influence the significant wave height (<span><math><mover><msub><mi>H</mi><mi>s</mi></msub><mo>̂</mo></mover></math></span>) on the platforms and the frequency components of the nearshore wavefield. As ocean waves share akin refractive properties to light rays, it can be assumed that, similarly to optical lenses, shore platforms can separate waves according to their frequency depending on their geometry. Thus, we use a non-linear Boussinesq wave model to conduct harmonic and bispectral mode decomposition analyses to study the control of concave and convex platform edges over wind waves (WW: 0.125–0.33 Hz), swell waves (SW: 0.05–0.125 Hz) and infragravity (IG: 0.008–0.05 Hz) waves frequencies. For breaking and non-breaking waves, increasing the platform edge concavity intensified wave divergence and subsequent attenuation of SW and IG across the outer platforms, reducing <span><math><mover><msub><mi>H</mi><mi>s</mi></msub><mo>̂</mo></mover></math></span> by up to 25 %. Increasing the platform edge convexity intensified focusing and amplification of SW and WW over the outer platforms, increasing <span><math><mover><msub><mi>H</mi><mi>s</mi></msub><mo>̂</mo></mover></math></span> by up to 18 % and 55 % for breaking and non-breaking waves. In the presence of breaking, IG amplification was affected by wave divergence across the inner platform, a condition determined by a critical convex curvature threshold (<span><math><mfenced><mi>K</mi></mfenced></math></span>=1.8) balancing wave focusing from refraction and defocusing from breaking. We find that convex curvature can determine the relative dominance of WW, SW and IG across platforms. Alongshore, coherent wave interactions governed IG stationary patterns defined by a node near the platform centreline and two antinodes on either side of concave edges. A node was generated at the platform centreline, and two antinodes were observed on either side of the convex edges for <span><math><mfenced><mi>K</mi></mfenced></math></span>>1.8, with the opposite pattern observed for <span><math><mfenced><mi>K</mi></mfenced></math></span><1.8. Such patterns likely result in alongshore variations in wave-generated currents and erosion shaping rock coasts.</div></div>","PeriodicalId":55115,"journal":{"name":"Geomorphology","volume":"468 ","pages":"Article 109491"},"PeriodicalIF":3.1,"publicationDate":"2024-11-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661879","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

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