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A method to estimate surface mass-balance in glacier accumulation areas based on digital elevation models and submergence velocities 基于数字高程模型和淹没速度估算冰川堆积区地表物质平衡的方法
IF 3.4 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2023-06-30 DOI: 10.1017/jog.2023.29
B. Jourdain, C. Vincent, M. Réveillet, A. Rabatel, F. Brun, D. Six, Olivier Laarman, L. Piard, P. Ginot, Olivier Sanchez, E. Berthier
Measuring surface mass-balance in the accumulation areas of glaciers is challenging because of the high spatial variability of snow accumulation and the difficulty of conducting annual field glaciological measurements. Here, we propose a method that can solve both these problems for many locations. Ground-penetrating radar measurements and firn cores extracted from a site in the French Alps were first used to reconstruct the topography of a buried end-of-summer snow horizon from a past year. Using these data and surface elevation observations from LiDAR and Global Navigation Satellite System instruments, we calculated the submergence velocities over the period between the buried horizon and more recent surface elevation observations. The differences between the changes in surface elevation and the submergence velocities were then used to calculate the annual surface mass-balances with an accuracy of ±0.34 m w.e. Assuming that the submergence velocities remain stable over several years, the surface mass-balance can be reconstructed for subsequent years from the differences in surface elevation alone. As opposed to the glaciological method that requires substantial fieldwork year after year to provide only point observations, this method, once submergence velocities have been calculated, requires only remote-sensing data to provide spatially distributed annual mass-balances in accumulation areas.
测量冰川堆积区的表面质量平衡具有挑战性,因为积雪的空间变异性很高,而且难以进行年度实地冰川学测量。在这里,我们提出了一种方法,可以在许多地方解决这两个问题。探地雷达测量和从法国阿尔卑斯山的一个地点提取的冷杉岩心首次用于重建去年夏末雪层的地形。利用这些数据和激光雷达和全球导航卫星系统仪器的地表高程观测,我们计算了埋藏地平线和最近地表高程观测之间的一段时间内的淹没速度。然后,利用地表高程变化和淹没速度之间的差异来计算年地表质量平衡,精度为±0.34 m w.e。假设淹没速度在几年内保持稳定,则可以仅根据地表高程的差异重建随后几年的地表质量平衡。与冰川学方法不同的是,这种方法需要年复一年的大量实地调查,只提供点观测,一旦计算出淹没速度,这种方法只需要遥感数据,就可以在堆积区提供空间分布的年度质量平衡。
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引用次数: 0
Bathymetry and bed conditions of Lago Subglacial CECs, West Antarctica 南极洲西部Lago冰下CECs的水深和海床条件
IF 3.4 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2023-06-29 DOI: 10.1017/jog.2023.38
A. Brisbourne, A. Smith, A. Rivera, R. Zamora, F. Napoleoni, J. Uribe, M. Ortega
Although over 600 Antarctic subglacial lakes have been identified using radar and satellite observations, the bathymetry and bed properties, which are key to understanding conditions within the lake, have been determined in very few localities. We present measurements of water column thickness and lakebed properties from Lago Subglacial CECs (SLC), located beneath 2653 m of ice at the Rutford-Institute-Minnesota divide in Antarctica. Seismic profiles indicate a maximum water column thickness of 301.3 ± 1.5 m, at the widest part of the lake, with an estimated lake volume of 2.5 ± 0.3 km3. Seismic imaging and measurements of the reflection strength at the ice base and lakebed indicate >15 m of high-porosity fine-grained sediment in the central section of the lakebed, consistent with a depositional sequence with an age of up to 0.5 Ma. These observations, along with previous radar measurements and modelling, indicate a low-energy sedimentary environment with a long water-residence time. As such, SLC is a suitable target for exploration via direct access to recover sediment records of ice sheet and climate history and investigate microbial life with long periods of isolation.
虽然利用雷达和卫星观测已经确定了600多个南极冰下湖泊,但对了解湖泊内部条件至关重要的水深和河床性质,只在极少数地方确定了。我们展示了位于南极洲Rutford-Institute-Minnesota分界处2653米冰下的Lago冰下cec (SLC)的水柱厚度和湖床特性的测量结果。地震剖面显示,湖最宽处水柱最大厚度为301.3±1.5 m,湖体积估计为2.5±0.3 km3。冰基和湖床的地震成像和反射强度测量表明,湖床中部有> ~ 15m的高孔隙度细粒沉积物,与沉积序列一致,沉积年龄可达0.5 Ma。这些观测结果,加上之前的雷达测量和建模,表明这是一个低能量的沉积环境,水停留时间很长。因此,通过直接获取冰盖沉积物记录和气候历史,以及研究长期隔离的微生物生活,SLC是一个合适的勘探目标。
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引用次数: 0
Global clustering of recent glacier surges from radar backscatter data, 2017–2022 2017-2022年雷达后向散射数据对近期冰川涌动的全球聚类分析
IF 3.4 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2023-06-29 DOI: 10.1017/jog.2023.35
A. Kääb, V. Bazilova, P. Leclercq, E. Mannerfelt, T. Strozzi
Using global Sentinel-1 radar backscatter data, we systematically map the locations of glaciers with surge-type activity during 2017–22. Patterns of pronounced increases or decreases in the strongest backscatter between two winter seasons often indicate large changes in glacier crevassing, which we treat here as a sign of surge-type activity. Validations against velocity time series, terminus advances and crevassing found in optical satellite images confirm the robustness of this approach. We find 115 surge-type events globally between 2017 and 2022, around 100 of which on glaciers already know as surge-type. Our data reveal a pronounced spatial clustering in three regions, (i) Karakoram, Pamirs and Western Kunlun Shan (~50 surges), (ii) Svalbard (~25) and (iii) Yukon/Alaska (~9), with only a few other scattered surges elsewhere. This spatial clustering is significantly more pronounced than the overall global clustering of known surge-type glaciers. The 2017–22 clustering may point to climatic forcing of surge initiation.
利用全球Sentinel-1雷达后向散射数据,我们系统地绘制了2017 - 2022年间具有涌浪型活动的冰川位置。两个冬季之间最强烈的后向散射的明显增加或减少的模式通常表明冰川裂缝的巨大变化,我们在这里将其视为涌浪型活动的标志。对光学卫星图像中速度时间序列、终端推进和裂缝的验证证实了该方法的鲁棒性。我们发现,在2017年至2022年期间,全球发生了115起涌浪型事件,其中约100起发生在冰川上。我们的数据显示,在喀喇昆仑、帕米尔高原和西昆仑山三个地区(~50个浪涌),(ii)斯瓦尔巴群岛(~25个浪涌)和(iii)育空/阿拉斯加(~9个浪涌)存在明显的空间聚集性,其他地方只有少数零散的浪涌。这种空间聚类明显比已知涌浪型冰川的总体全球聚类更为明显。2017-22年的聚集可能表明气候因素推动了浪涌的形成。
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引用次数: 1
Influence of seasonally varying sea-ice concentration and subsurface ocean heat on sea-ice thickness and sea-ice seasonality for a ‘warm-shelf’ region in Antarctica 季节性变化的海冰浓度和海底热对南极洲“暖架”地区海冰厚度和海冰季节性的影响
IF 3.4 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2023-06-29 DOI: 10.1017/jog.2023.36
B. Saenz, D. McKee, S. Doney, D. Martinson, S. Stammerjohn
Processes driving changes in sea-ice seasonality and sea-ice thickness were explored for a ‘warm-shelf’ region along the West Antarctic Peninsula using vertically coupled sea-ice-ocean thermodynamic simulations, with and without assimilated satellite sea-ice observations and moored ocean temperature observations. Simulations with assimilated sea-ice observations permitted investigation of surface [thermodynamic and dynamic (e.g., wind-driven)] processes affecting sea-ice thickness and seasonality. Assimilation of quasi-weekly variability in the depth and temperature of the deep warm pycnocline permitted examination of subsurface processes affecting sea-ice. Simulations using assimilated sea-ice observations (and implied motion) always produced greater surface heat fluxes and overall thinner sea ice. Assimilating seasonal and quasi-weekly variability in the depth and temperature of the pycnocline modified the start of the sea-ice season by −23 to +1 d, and also modified the sea ice thickness/seasonality to be thinner/shorter or thicker/longer at sub-seasonal and seasonal timescales, highlighting a mechanism where a shoaling pycnocline enhanced upward deep-water heat fluxes as transient surface-induced turbulence had a greater effect on a reduced mixed layer volume. The observed interplay of surface, subsurface, and sea-ice modulation of ocean-atmosphere heat transfer underscores the importance of representing the interaction between sea-ice concentration and upper ocean variability in climate projections.
使用垂直耦合的海冰-海洋热力学模拟,在有和没有同化卫星海冰观测和系泊海洋温度观测的情况下,探索了南极半岛西部“温暖大陆架”地区驱动海冰季节性和海冰厚度变化的过程。利用同化海冰观测进行模拟,可以研究影响海冰厚度和季节性的表面[热力学和动力学(如风力驱动)]过程。通过同化深部温暖的比重跃层的深度和温度的准周变化,可以检查影响海冰的地下过程。使用同化海冰观测(和隐含运动)的模拟总是产生更大的表面热通量和更薄的海冰。在亚季节性和季节性时间尺度上,同化固冰层深度和温度的季节性和准周性变化使海冰季节的开始时间缩短了−23至+1天,还使海冰厚度/季节性变薄/变短或变厚/变长,强调了一种机制,即变浅的比重跃层增强了向上的深水热通量,因为瞬态表面诱导的湍流对减少的混合层体积有更大的影响。观测到的海洋-大气热传递的表面、地下和海冰调节的相互作用强调了在气候预测中代表海冰浓度和上层海洋可变性之间的相互作用的重要性。
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引用次数: 1
Subglacial hydrology modeling predicts high winter water pressure and spatially variable transmissivity at Helheim Glacier, Greenland 冰下水文模型预测格陵兰赫尔海姆冰川冬季高压和空间可变透射率
IF 3.4 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2023-06-21 DOI: 10.1017/jog.2023.39
A. Sommers, C. Meyer, M. Morlighem, H. Rajaram, K. Poinar, W. Chu, J. Mejia
Water pressure beneath glaciers influences ice velocity. Subglacial hydrology models are helpful for gaining insight into basal conditions, but models depend on unconstrained parameters, and a current challenge is reproducing elevated water pressures in winter. We eliminate terms related to englacial storage, opening by sliding, and melt due to changes in the pressure-melting-point temperature, to create a minimalist version of the Subglacial Hydrology And Kinetic, Transient Interactions (SHAKTI) model, and apply this model to Helheim Glacier in east Greenland to explore the winter base state of the subglacial drainage system. Our results suggest that meltwater produced at the bed alone supports active winter drainage with large areas of elevated water pressure and preferential drainage pathways, using a continuum approach that allows for transitions between flow regimes. Transmissivity varies spatially over several orders of magnitude from 10−4 to 103 m2s−1, with regions of weak transmissivity representing poorly connected regions of the system. Bed topography controls the location of primary drainage pathways, and high basal melt rates occur along the steep valley walls. Frictional heat from sliding is a dominant source of basal melt; different approaches for calculating basal shear stress produce significantly different basal melt rates and subglacial discharge.
冰川下的水压影响冰的流速。冰下水文模型有助于深入了解基础条件,但模型依赖于不受约束的参数,目前的挑战是再现冬季升高的水压。我们消除了与冰川储存、滑动打开和压力熔点温度变化相关的术语,创建了极简版本的冰下水文和动力学、瞬态相互作用(SHAKTI)模型,并将该模型应用于格陵兰东部的Helheim冰川,以探索冰下排水系统的冬季基本状态。我们的研究结果表明,仅在床上产生的融水就可以通过大面积的高水压和优先的排水路径来支持冬季的主动排水,使用连续的方法,允许在流动状态之间转换。透射率在空间上从10−4到103 m2s−1变化了几个数量级,弱透射率的区域代表系统中连接不良的区域。河床地形控制着主要排水通道的位置,沿陡峭的山谷壁发生高基底融化速率。滑动摩擦热是基底熔体的主要热源;计算基底剪应力的不同方法会产生显著不同的基底融化速率和冰下流量。
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引用次数: 3
‘Stable’ and ‘unstable’ are not useful descriptions of marine ice sheets in the Earth's climate system “稳定”和“不稳定”不是对地球气候系统中海洋冰盖的有用描述
IF 3.4 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2023-06-21 DOI: 10.1017/jog.2023.40
O. Sergienko, M. Haseloff
Investigations of the time-dependent behavior of marine ice sheets and their sensitivity to basal conditions require numerical models because existing theoretical analyses focus only on steady-state configurations primarily with a power-law basal shear stress. Numerical results indicate that the choice of the sliding law strongly affects ice-sheet dynamic behavior. Although observed or simulated grounding-line retreat is typically interpreted as an indication of marine ice sheet instability introduced by Weertman (1974), this (in)stability is a characteristic of the ice sheet's steady states – not time-variant behavior. To bridge the gap between theoretical and numerical results, we develop a framework to investigate grounding line dynamics with generalized basal and lateral stresses (i.e. the functional dependencies are not specified). Motivated by observations of internal variability of the Southern Ocean conditions we explore the grounding-line response to stochastic variability. We find that adding stochastic variability to submarine melt rates that produced stable steady-state configurations leads to intermittently advancing and retreating grounding lines. They can also retreat in an unstoppable manner on time-scales significantly longer than the stochastic correlation time-scales. These results suggest that at any given time of their evolution, the transient behavior of marine ice sheets cannot be described in terms of ‘stable’ or ‘unstable’.
研究海洋冰盖的时间依赖行为及其对基底条件的敏感性需要数值模型,因为现有的理论分析只关注主要具有幂律基底剪切应力的稳态结构。数值结果表明,滑动规律的选择对冰盖的动力特性有很大影响。尽管观察到或模拟的接地线后退通常被解释为Weertman(1974)引入的海洋冰盖不稳定的迹象,但这种(内)稳定性是冰盖稳态的特征,而不是时变行为。为了弥补理论结果和数值结果之间的差距,我们开发了一个框架来研究具有广义基底应力和侧向应力的接地线动力学(即未指定函数相关性)。受南大洋条件内部变化观测的启发,我们探索了接地线对随机变化的响应。我们发现,在产生稳定稳态配置的海底融化速率中增加随机可变性会导致接地线间歇性前进和后退。它们也可以在时间尺度上以不可阻挡的方式撤退,时间尺度明显长于随机相关时间尺度。这些结果表明,在其演化的任何给定时间,海洋冰盖的瞬态行为都不能用“稳定”或“不稳定”来描述。
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引用次数: 2
Water blister geomorphology and subglacial drainage sediments: an example from the bed of the Fennoscandian Ice Sheet in SW Finland 水疱地貌和冰下排水沉积物:芬兰西南部芬诺斯坎德冰盖床的一个例子
3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2023-06-21 DOI: 10.1017/jog.2023.37
Joni Mäkinen, Christine F. Dow, Elina Ahokangas, Antti Ojala, Kari Kajuutti, Juulia Kautto, Jukka-Pekka Palmu
Abstract This study presents the first light detection and ranging (LiDAR)-based morphometric description of a water blister from a past ice-sheet bed caused by rapid supraglacial drainage. The blister formed during the rapid early Holocene deglaciation of the Fennoscandian Ice Sheet (FIS). It is located in southwest Finland within a subglacial meltwater route interpreted to represent the transition from a distributed to a channelized drainage system. A LiDAR digital elevation model was supplemented with sedimentological and ground-penetrating radar data on blister outflow channels and sedimentology of downflow polymorphous mounds and ridges (PMRs). Unlike the water blisters recorded from the rapid drainage of supraglacial lakes on the Greenland Ice Sheet, the smaller blister size here was either due to crevasse or moulin drainage, or was a supraglacial lake drainage that tapped into a pre-existing, relatively efficient drainage system and related semi-sorted sediments, promoting rapid drainage and reworking of PMRs along the meltwater route. The preservation potential or exposure probability of blister marks is presumably low but they can provide important information about evolution of subglacial drainage systems that is of value to modern interpretations of glacial hydrology.
摘要:本研究首次提出了基于光探测和测距(LiDAR)的形态学描述,描述了由冰川上快速排水引起的过去冰盖床上的水疱。该水疱形成于芬诺斯坎德冰原(FIS)全新世早期快速消冰期间。它位于芬兰西南部的冰下融水路线中,代表了从分布式到渠化排水系统的过渡。在激光雷达数字高程模型的基础上,补充了水疱流出通道的沉积学和探地雷达数据以及下流多形丘脊(PMRs)的沉积学数据。与格陵兰冰原上冰湖快速排水记录的水疱不同,这里较小的水疱大小要么是由于裂缝或冰穴排水,要么是冰原上湖排水利用了已有的、相对有效的排水系统和相关的半分类沉积物,促进了沿着融水路线的pmr的快速排水和改造。水疱痕迹的保存潜力或暴露可能性可能很低,但它们可以提供关于冰下排水系统演化的重要信息,对现代冰川水文学解释具有价值。
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引用次数: 0
Post-Little Ice Age glacial lake evolution in Svalbard: inventory of lake changes and lake types 斯瓦尔巴小冰期后冰川湖的演变:湖泊变化和湖泊类型清单
IF 3.4 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2023-06-14 DOI: 10.1017/jog.2023.34
Iwona Wieczorek, M. Strzelecki, Ł. Stachnik, J. Yde, Jakub Małecki
The rapid formation of glacial lakes is one of the most conspicuous landscape changes caused by atmospheric warming in glacierised regions. However, relatively little is known about the history and current state of glacial lakes in the High Arctic. This study aims to address this issue by providing the first inventory of glacial lakes in Svalbard, focusing in particular on the post-Little Ice Age evolution of glacial lakes and their typology. To do so, we used aerial photographs and satellite imagery together with archival topographic data from 1936 to 2020. The inventory comprises the development of 566 glacial lakes (146 km2) that were still in direct contact with glaciers during the period 2008–2012. The results show a consistent increase in the total area of glacial lakes from the 1930s to 2020 and suggest an apparent link between climatic and geological factors, and the formation of specific lake dam types: moraine, ice, or bedrock. We also detected 134 glacial lake drainage events that have occurred since the 1930s. This study shows that Svalbard has one of the highest rates of glacial lake development in the world, which is an indicator of the overall dynamics of landscape change in the archipelago in response to climate change.
冰川湖的快速形成是冰川地区大气变暖引起的最显著的景观变化之一。然而,人们对高北极地区冰川湖的历史和现状知之甚少。本研究旨在通过提供斯瓦尔巴群岛冰川湖的第一个清单来解决这个问题,特别关注小冰河期后冰川湖的演变及其类型学。为此,我们使用了航空照片和卫星图像以及1936年至2020年的档案地形数据。该清单包括2008-2012年期间仍与冰川直接接触的566个冰川湖(146平方公里)的发展情况。结果表明,从20世纪30年代到2020年,冰川湖的总面积持续增加,并表明气候和地质因素与特定湖坝类型(冰碛、冰或基岩)的形成之间存在明显的联系。我们还发现了自20世纪30年代以来发生的134次冰湖排水事件。这项研究表明,斯瓦尔巴群岛是世界上冰川湖发展速度最快的地区之一,这是该群岛应对气候变化的整体景观变化动态的一个指标。
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引用次数: 1
Strong impact of sub-shelf melt parameterisation on ice-sheet retreat in idealised and realistic Antarctic topography 理想和现实南极地形中亚陆架融化参数化对冰盖退缩的强烈影响
IF 3.4 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2023-06-01 DOI: 10.1017/jog.2023.33
Constantijn J. Berends, L. Stap, R. V. D. van de Wal
Future projections of sea-level rise under strong warming scenarios are dominated by mass loss in the marine-grounded sectors of West Antarctica, where thinning shelves as a result of warming oceans can lead to reduced buttressing. This consequently leads to accelerated flow from the upstream grounded ice. However, the relation between warming oceans and increased melt rates under the shelves is very uncertain, especially when interactions with the changing shelf geometry are considered. Here, we compare six widely used, highly parameterised formulations relating sub-shelf melt to thermal forcing. We implemented them in an ice-sheet model, and applied the resulting set-up to an idealised-geometry setting, as well as to the Antarctic ice sheet. In our simulations, the differences in modelled ice-sheet evolution resulting from the choice of parameterisation, as well as the choice of numerical scheme used to apply sub-shelf melt near the grounding line, generally are larger than differences from ice-dynamical processes such as basal sliding, as well as uncertainties from the forcing scenario of the model providing the ocean forcing. This holds for the idealised-geometry experiments as well as for the experiments using a realistic Antarctic topography.
在强变暖情景下对海平面上升的未来预测主要是由西南极洲陆基部分的大量损失所主导,在那里,由于海洋变暖,冰架变薄可能导致支撑作用减少。这就导致了上游接地冰的加速流动。然而,海洋变暖与大陆架下融化速度增加之间的关系是非常不确定的,特别是考虑到与大陆架几何形状变化的相互作用。在这里,我们比较了六种广泛使用的、高度参数化的关于亚大陆架融化与热强迫的公式。我们在冰盖模型中实现了它们,并将结果设置应用于理想的几何设置,以及南极冰盖。在我们的模拟中,由于参数化的选择,以及用于应用接地线附近的亚大陆架融化的数值方案的选择,导致的模拟冰盖演变的差异通常大于冰动力过程(如基底滑动)的差异,以及来自提供海洋强迫的模式的强迫情景的不确定性。这既适用于理想几何实验,也适用于使用真实南极地形的实验。
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引用次数: 1
Detection of crevassed areas with minimum geometric information: Vernagtferner case study 用最小几何信息检测交叉区域:Vernagtferner案例研究
IF 3.4 3区 地球科学 Q2 GEOGRAPHY, PHYSICAL Pub Date : 2023-05-29 DOI: 10.1017/jog.2023.12
Theresa Dobler, W. Hagg, C. Mayer
Crevasses pose severe risks for mountaineers and field glaciologists. Smaller cracks between 0.5 and 2 m are still dangerous, but often not visible in medium resolution satellite imagery. If they are snow covered, they are completely undetectable by optical sensors. We set out to develop an approach to detect potentially crevassed areas by a minimum of geometric data, and to make the method generally applicable to glacier regions. On Vernagtferner, we compared a reference dataset of crevasses observed in high-resolution optical imagery with the curvature of the ice surface and the spatial gradients in driving stress. Both parameters can be derived from a digital surface model and a bedrock model, derived from ice thickness measurements. The correlation patterns show that crevasses preferably form in convex areas and in areas where the driving stress rapidly increases. This corresponds with the theory of crevasse formation. Although the method still misclassifies larger parts, the approach has the potential to define probable non-crevassed areas as well as to aid the planning of safe routes.
裂缝给登山者和野外冰川学家带来了严重的风险。0.5到2米之间的较小裂缝仍然很危险,但在中等分辨率的卫星图像中通常看不到。如果它们被雪覆盖,则光学传感器完全无法检测到它们。我们着手开发一种方法,通过最少的几何数据来检测潜在的裂缝区域,并使该方法普遍适用于冰川区域。在Vernagtferner上,我们将高分辨率光学图像中观察到的裂缝参考数据集与冰面曲率和驱动应力的空间梯度进行了比较。这两个参数都可以从数字表面模型和基岩模型中得出,基岩模型是从冰厚度测量中得出的。相关模式表明,裂缝最好形成在凸起区域和驱动应力迅速增加的区域。这与裂缝形成的理论是一致的。尽管该方法仍然错误地对较大的部分进行了分类,但该方法有可能定义可能的非裂缝区域,并有助于规划安全路线。
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引用次数: 0
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Journal of Glaciology
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