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Characterizing bed roughness on the Antarctic continental margin 描述南极大陆边缘河床粗糙度的特征
3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2023-10-31 DOI: 10.1017/jog.2023.88
Santiago Munevar Garcia, Lauren Elizabeth Miller, Francesca Anna Maria Falcini, Leigh Asher Stearns
Abstract Spatial variability in bed topography, characterized as bed roughness, impacts ice-sheet flow and organization and can be used to infer subglacial conditions and processes, yet is difficult to quantify due to sparse observations. Paleo-subglacial beds of formerly expanded glaciers found across the Antarctic continental shelf are well preserved, have relatively limited post-glacial sediment cover and contain glacial landforms that can be resolved at sub-meter vertical scales. We analyze high-resolution bathymetry offshore of Pine Island and Thwaites glaciers in the Amundsen Sea to explore spatial variability of bed roughness where streamlined subglacial landforms allow for the determination of ice-flow direction. We quantify bed roughness using std dev. and Fast Fourier Transform methods, each employed at local (10 0 km) and regional (10 1–2 km) scales and in along- and across-flow orientations to determine roughness expressions across spatial scales. We find that the magnitude of roughness is impacted by the parameters selected – which are often not sufficiently reported in studies – to quantify roughness. Important spatial patterns can be discerned from high-resolution bathymetry, highlighting both its usefulness in identifying patterns of streaming ice flow and underscores the need for a standardized way of characterizing topographic variability.
以床面粗糙度为特征的床面地形空间变异性影响冰盖的流动和组织,可用于推断冰下条件和过程,但由于观测数据稀疏,难以量化。在南极大陆架上发现的原扩张冰川的古冰下床保存完好,冰后沉积物覆盖相对有限,并且包含可以在亚米垂直尺度上解析的冰川地貌。我们分析了阿蒙森海松树岛和Thwaites冰川近海的高分辨率水深测量,以探索河床粗糙度的空间变动性,其中流线型冰下地貌允许确定冰流方向。我们使用std发展和快速傅立叶变换方法来量化床层粗糙度,每种方法都在局部(10 0 km)和区域(10 1-2 km)尺度上以及沿流和跨流方向上使用,以确定不同空间尺度上的粗糙度表达式。我们发现粗糙度的大小受到所选择的参数的影响-这些参数在研究中通常没有得到充分的报道-以量化粗糙度。通过高分辨率测深技术可以识别出重要的空间格局,突出了其在识别冰流模式方面的有用性,并强调了对表征地形变化的标准化方法的需求。
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引用次数: 0
Historical occurrence of Antarctic icebergs within mercantile shipping routes and the exceptional events of the 1890s 南极冰山在商业航线上的历史事件和19世纪90年代的特殊事件
3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2023-10-27 DOI: 10.1017/jog.2023.80
Robert Keith Headland, Nicholas Edward Hughes, Jeremy Paul Wilkinson
Abstract A major consideration for maritime activity in the Southern Hemisphere is the northern limit of icebergs, or the Southern Ocean Limit Of Known Ice (SOLOKI). This analysis of historical reports of icebergs during Southern Hemisphere voyages from 1687 to 1933 provides a basis for examination of their geographical and chronological occurrence during ~250 years. The analyses use tabulated data from 742 voyages and other reports from many sources, some including first-person descriptions. While these data are dependent on icebergs being reported by mariners, as well as the variable frequency of voyages, they demonstrate distinct periods of exceptional frequency of icebergs occurring in certain localities, particularly the far South Atlantic. Based upon historical records the evidence suggests unprecedented numbers of icebergs were present in southern shipping channels in the 1890s. When these historical observations are combined with modern iceberg drift trajectories, their possible origin can be elucidated. Owing to the numbers of icebergs seen and their geographical spread, our results suggest that this was possibly the largest near-synchronous calvings in the last 300 years, and the northernmost extent of the SOLOKI.
南半球海洋活动的一个主要考虑因素是冰山的北部界限,或已知冰的南大洋界限(SOLOKI)。本文对1687年至1933年南半球航行中冰山的历史报告进行了分析,为考察250年来冰山在地理和时间上的发生提供了基础。这些分析使用了来自742次航行的表格数据和来自许多来源的其他报告,其中一些包括第一人称描述。虽然这些数据依赖于水手报告的冰山,以及航行频率的变化,但它们表明,在某些地方,特别是在遥远的南大西洋,冰山出现的频率不同。根据历史记录,有证据表明,在19世纪90年代,南部航道上出现了数量空前的冰山。当这些历史观测与现代冰山漂移轨迹相结合时,它们可能的起源就可以得到阐明。根据看到的冰山数量和它们的地理分布,我们的研究结果表明,这可能是近300年来最大的近同步崩解,也是索洛基冰川最北端的崩解。
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引用次数: 0
Measuring seismic attenuation in polar firn: method and application to Korff Ice Rise, West Antarctica 极地冰层地震衰减测量方法及在南极西部科尔夫冰脊的应用
3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2023-10-26 DOI: 10.1017/jog.2023.82
Ronan S. Agnew, Roger A. Clark, Adam D. Booth, Alex M. Brisbourne, Andrew M. Smith
Abstract We present seismic measurements of the firn column at Korff Ice Rise, West Antarctica, including measurements of compressional-wave velocity and attenuation. We describe a modified spectral-ratio method of measuring the seismic quality factor ( Q ) based on analysis of diving waves, which, combined with a stochastic method of error propagation, enables us to characterise the attenuative structure of firn in greater detail than has previously been possible. Q increases from 56 ± 23 in the uppermost 12 m to 570 ± 450 between 55 and 77 m depth. We corroborate our method with consistent measurements obtained via primary reflection, multiple, source ghost, and critically refracted waves. Using the primary reflection and its ghost, we find Q = 53 ± 20 in the uppermost 20 m of firn. From the critical refraction, we find Q = 640 ± 400 at 90 m depth. Our method aids the understanding of the seismic structure of firn and benefits characterisation of deeper glaciological targets, providing an alternative means of correcting seismic reflection amplitudes in cases where conventional methods of Q correction may be impossible.
摘要本文介绍了南极西部Korff冰隆起的firn柱的地震测量,包括压缩波速度和衰减的测量。我们描述了一种基于潜水波分析的改进的测量地震质量因子(Q)的频谱比方法,该方法与误差传播的随机方法相结合,使我们能够比以前更详细地表征公司的衰减结构。Q从最上层12 m的56±23增加到55 ~ 77 m深度的570±450。我们通过主反射波、多重波、源虚波和临界折射波获得一致的测量结果来证实我们的方法。利用主反射及其鬼影,我们得到在光线最上方20 m处Q = 53±20。根据临界折射,我们发现在90 m深度处Q = 640±400。我们的方法有助于了解firn的地震结构,并有利于表征更深层次的冰川目标,在传统的Q校正方法可能无法实现的情况下,提供一种校正地震反射振幅的替代方法。
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引用次数: 0
Tracking coarse sediment in an Alpine subglacial channel using radio-tagged particles 利用放射性标记粒子追踪高山冰下通道中的粗沉积物
3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2023-10-09 DOI: 10.1017/jog.2023.77
Matt Jenkin, Margaux Hofmann, Bryn Hubbard, Davide Mancini, Floreana M. Miesen, Frédéric Herman, Stuart N. Lane
Abstract We present a method for tracking radio-tagged pebbles and cobbles through subglacial meltwater channels under shallow temperate glaciers. Natural particles tagged with active radio transmitters were injected directly into a large subglacial channel 300 m up-glacier from the terminus of the Glacier d'Otemma, Switzerland. A roving antenna was developed to localise tagged particles planimetrically in subglacial and proglacial channel reaches (350 and 150 m long, respectively) using a probabilistic technique, delivering records of the change in particle location and transport distance over time with uncertainty. The roving antenna had a ±5−15 m planimetric precision, a 75% particle localisation rate and operated at a maximum ice depth of 47 m. Additionally, stationary supraglacial and proglacial antennas continuously monitored the passage of tagged particles through consecutive reaches of the channel, constraining the timing of particle transport events. The proglacial antenna system had a 98.1% detection rate and was operational to 0.89 m water depth during testing. Roving and stationary antenna records were combined to create a transport distance model for each particle, which may be used in conjunction with hydraulic data to investigate the kinematics of particle motion. When applied at scale in future studies, this method may be used to reveal the mechanisms and timescales of coarse sediment export from Alpine glaciers.
摘要:我们提出了一种追踪温带浅冰川下冰下融水通道中放射性标记鹅卵石和鹅卵石的方法。标记有主动无线电发射机的天然粒子被直接注入从瑞士奥德马冰川末端冰川上方300米的大型冰下通道。研究人员开发了一种漫游天线,利用概率技术在冰下和冰前通道(分别为350米和150米长)中平面定位标记粒子,记录粒子位置和传输距离随时间的不确定性变化。粗纱天线的平面精度为±5 - 15 m,粒子定位率为75%,最大冰深为47 m。此外,静止的冰川上和冰川前天线持续监测标记粒子在通道连续到达的通道,限制了粒子输运事件的时间。前冰川天线系统的检出率为98.1%,测试时工作水深为0.89 m。将漫游和固定天线记录结合起来,创建每个粒子的传输距离模型,该模型可以与水力数据结合使用,以研究粒子运动的运动学。在未来的研究中,该方法可用于揭示高山冰川粗沙输出的机制和时间尺度。
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引用次数: 0
Temporal downscaling of glaciological mass balance using seasonal observations 利用季节观测的冰川物质平衡的时间降尺度
3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2023-10-09 DOI: 10.1017/jog.2023.66
Michael Zemp, Ethan Welty
Abstract Glaciological mass-balance measurements have been the backbone of internationally coordinated glacier monitoring. The resulting annual observations have been used to understand glacier reactions to climate change, and to assess both regional and global glacier mass changes and related contributions to runoff and sea-level rise. However, the comparability of annual observations is hampered by differences in survey periods and mass-balance amplitudes between glaciers, regions and hemispheres. This study presents a simple approach to temporally downscale glaciological mass balance using seasonal observations and sine functions. The proposed analytical model allows reconstruction of the seasonal course of glacier mass balance at weekly to monthly resolution from only annual or seasonal observations. Strengths and limitations of this analytical approach are discussed and compared with results from numerical mass-balance modelling. Potential applications include seasonal corrections of glaciological and geodetic observations and comparisons to monthly results from spaceborne gravimetry and altimetry.
冰川质量平衡测量一直是国际协调冰川监测的支柱。由此产生的年度观测已用于了解冰川对气候变化的反应,并评估区域和全球冰川质量变化及其对径流和海平面上升的相关贡献。然而,年度观测的可比性受到冰川、区域和半球之间的调查周期和质量平衡振幅差异的影响。本研究提出了一种利用季节观测和正弦函数来研究时间尺度下冰川物质平衡的简单方法。所提出的分析模型允许仅从年度或季节观测资料,以周至月的分辨率重建冰川物质平衡的季节过程。讨论了这种分析方法的优点和局限性,并与数值质量平衡模拟的结果进行了比较。潜在的应用包括冰川学和大地测量观测的季节校正以及与星载重力和测高每月结果的比较。
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引用次数: 0
The speedup of Pine Island Ice Shelf between 2017 and 2020: revaluating the importance of ice damage 2017 - 2020年松岛冰架的加速:冰损重要性的重新评估
3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2023-10-09 DOI: 10.1017/jog.2023.76
Sainan Sun, G. Hilmar Gudmundsson
Abstract From 2017 to 2020, three significant calving events took place on Pine Island Glacier, West Antarctica. Ice-shelf velocities changed over this period and the calving events have been suggested as possible drivers. However, satellite observations also show significant changes in the areal extent of fracture zones, especially in the marginal areas responsible for providing lateral support to the ice shelf. Here, we conduct a model study to identify and quantify drivers of recent ice-flow changes of the Pine Island Ice Shelf. In agreement with recent studies, we find that the calving events caused significant velocity changes over the ice shelf. However, calving alone cannot explain observed velocity changes. Changes in the structural rigidity, i.e. ice damage, further significantly impacted ice flow. We suggest that ice damage evolution of the ice-shelf margins may have influenced recent calving events, and these two processes are linked.
2017年至2020年,南极西部松岛冰川发生了三次重大的产犊事件。冰架的速度在这一时期发生了变化,而裂冰事件被认为是可能的驱动因素。然而,卫星观测也显示,断裂带的面积范围发生了显著变化,特别是在为冰架提供横向支撑的边缘地区。在这里,我们进行了一个模型研究,以确定和量化松岛冰架最近冰流变化的驱动因素。与最近的研究一致,我们发现冰裂事件引起了冰架上显著的速度变化。然而,单靠产犊不能解释观测到的速度变化。结构刚度的变化,即冰损伤,进一步显著影响冰流。我们认为冰架边缘的冰损演化可能影响了最近的冰裂事件,这两个过程是相互联系的。
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引用次数: 0
Radiofrequency ice dielectric measurements at Summit Station, Greenland 格陵兰峰顶站的射频冰介电测量
3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2023-10-09 DOI: 10.1017/jog.2023.72
Juan Antonio Aguilar, Patrick Allison, Dave Besson, Abby Bishop, Olga Botner, Sjoerd Bouma, Stijn Buitink, Maddalena Cataldo, Brian A. Clark, Kenny Couberly, Zach Curtis-Ginsberg, Paramita Dasgupta, Simon de Kockere, Krijn D. de Vries, Cosmin Deaconu, Michael A. DuVernois, Anna Eimer, Christian Glaser, Allan Hallgren, Steffen Hallmann, Jordan Christian Hanson, Bryan Hendricks, Jakob Henrichs, Nils Heyer, Christian Hornhuber, Kaeli Hughes, Timo Karg, Albrecht Karle, John L. Kelley, Michael Korntheuer, Marek Kowalski, Ilya Kravchenko, Ryan Krebs, Robert Lahmann, Uzair Latif, Joseph Mammo, Matthew J. Marsee, Zachary S. Meyers, Kelli Michaels, Katharine Mulrey, Marco Muzio, Anna Nelles, Alexander Novikov, Alisa Nozdrina, Eric Oberla, Bob Oeyen, Ilse Plaisier, Noppadol Punsuebsay, Lilly Pyras, Dirk Ryckbosch, Olaf Scholten, David Seckel, Mohammad Ful Hossain Seikh, Daniel Smith, Jethro Stoffels, Daniel Southall, Karen Terveer, Simona Toscano, Delia Tosi, Dieder J. Van Den Broeck, Nick van Eijndhoven, Abigail G. Vieregg, Janna Z. Vischer, Christoph Welling, Dawn R. Williams, Stephanie Wissel, Robert Young, Adrian Zink
Abstract We recently reported on the radio-frequency attenuation length of cold polar ice at Summit Station, Greenland, based on bi-static radar measurements of radio-frequency bedrock echo strengths taken during the summer of 2021. Those data also allow studies of (a) the relative contributions of coherent (such as discrete internal conducting layers with sub-centimeter transverse scale) vs incoherent (e.g. bulk volumetric) scattering, (b) the magnitude of internal layer reflection coefficients, (c) limits on signal propagation velocity asymmetries (‘birefringence’) and (d) limits on signal dispersion in-ice over a bandwidth of ~100 MHz. We find that (1) attenuation lengths approach 1 km in our band, (2) after averaging 10 000 echo triggers, reflected signals observable over the thermal floor (to depths of ~1500 m) are consistent with being entirely coherent, (3) internal layer reflectivities are ≈–60 $to$ –70 dB, (4) birefringent effects for vertically propagating signals are smaller by an order of magnitude relative to South Pole and (5) within our experimental limits, glacial ice is non-dispersive over the frequency band relevant for neutrino detection experiments.
我们最近报道了基于双基地雷达测量2021年夏季射频基岩回波强度的格陵兰峰顶站寒冷极地冰的射频衰减长度。这些数据还允许研究(a)相干(如亚厘米横向尺度的离散内部导电层)与非相干(如体积)散射的相对贡献,(b)内层反射系数的大小,(c)信号传播速度不对称的限制(“双折射”)和(d)在~100 MHz带宽上冰内信号色散的限制。我们发现(1)在我们的波段中衰减长度接近1 km,(2)在平均10000个回波触发后,在热层(深度~1500 m)上可观测到的反射信号与完全相干一致,(3)内层反射率为≈-60 $ $至$ -70 dB,(4)相对于南极,垂直传播信号的双折射效应小了一个数量级,(5)在我们的实验限制内。冰川冰在与中微子探测实验相关的频带上是非色散的。
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引用次数: 2
Coupled climate-glacier modelling of the last glaciation in the Alps 阿尔卑斯山末次冰期的耦合气候-冰川模拟
3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2023-10-06 DOI: 10.1017/jog.2023.74
Guillaume Jouvet, Denis Cohen, Emmanuele Russo, Jonathan Buzan, Christoph C. Raible, Wilfried Haeberli, Sarah Kamleitner, Susan Ivy-Ochs, Michael A. Imhof, Jens K. Becker, Angela Landgraf, Urs H. Fischer
Abstract Our limited knowledge of the climate prevailing over Europe during former glaciations is the main obstacle to reconstruct the past evolution of the ice coverage over the Alps by numerical modelling. To address this challenge, we perform a two-step modelling approach: First, a regional climate model is used to downscale the time slice simulations of a global earth system model in high resolution, leading to climate snapshots during the Last Glacial Maximum (LGM) and the Marine Isotope Stage 4 (MIS4). Second, we combine these snapshots and a climate signal proxy to build a transient climate over the last glacial period and force the Parallel Ice Sheet Model to simulate the dynamical evolution of glaciers in the Alps. The results show that the extent of modelled glaciers during the LGM agrees with several independent key geological imprints, including moraine-based maximal reconstructed glacial extents, known ice transfluences and trajectories of erratic boulders of known origin and deposition. Our results highlight the benefit of multiphysical coupled climate and glacier transient modelling over simpler approaches to help reconstruct paleo glacier fluctuations in agreement with traces they have left on the landscape.
我们对前冰期欧洲气候的有限了解是通过数值模拟重建阿尔卑斯山冰覆盖过去演变的主要障碍。为了应对这一挑战,我们采用了两步建模方法:首先,使用区域气候模式对全球地球系统模式的高分辨率时间片模拟进行缩小,从而获得末次盛冰期(LGM)和海洋同位素阶段4 (MIS4)期间的气候快照。其次,我们将这些快照与气候信号代理相结合,构建末次冰期的瞬态气候,并强迫平行冰盖模式模拟阿尔卑斯冰川的动态演变。结果表明,LGM期间模拟冰川的范围与几个独立的关键地质印记一致,包括基于冰碛的最大重建冰川范围、已知的冰流和已知起源和沉积的不规则巨石的轨迹。我们的研究结果强调了多物理耦合气候和冰川瞬态建模的好处,而不是更简单的方法来帮助重建古冰川波动,以符合它们在景观上留下的痕迹。
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引用次数: 3
JOG volume 69 issue 277 Cover and Back matter JOG卷69期277封面和封底
3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2023-10-01 DOI: 10.1017/jog.2023.85
An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.
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引用次数: 0
JOG volume 69 issue 277 Cover and Front matter JOG第69卷第277期封面和封面问题
3区 地球科学 Q1 Earth and Planetary Sciences Pub Date : 2023-10-01 DOI: 10.1017/jog.2023.84
An abstract is not available for this content so a preview has been provided. As you have access to this content, a full PDF is available via the ‘Save PDF’ action button.
此内容的摘要不可用,因此提供了预览。当您可以访问此内容时,可以通过“保存PDF”操作按钮获得完整的PDF。
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引用次数: 0
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Journal of Glaciology
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