气候变化领域集成服务门户(CCPortal): Monitoring the seasonal changes of an englacial conduit network using repeated ground-penetrating radar measurements

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DOI	10.5194/tc-14-3269-2020
	Monitoring the seasonal changes of an englacial conduit network using repeated ground-penetrating radar measurements
	Church G.; Grab M.; Schmelzbach C.; Bauder A.; Maurer H.
发表日期	2020
ISSN	19940416
起始页码	3269
结束页码	3286
卷号	14 期号:10
英文摘要	Englacial conduits act as water pathways to feed surface meltwater into the subglacial drainage system. A change of meltwater into the subglacial drainage system can alter the glacier's dynamics. Between 2012 and 2019, repeated 25MHz ground-penetrating radar (GPR) surveys were carried out over an active englacial conduit network within the ablation area of the temperate Rhonegletscher, Switzerland. In 2012, 2016, and 2017 GPR measurements were carried out only once a year, and an englacial conduit was detected in 2017. In 2018 and 2019 the repetition survey rate was increased to monitor seasonal variations in the detected englacial conduit. The resulting GPR data were processed using an impedance inversion workflow to compute GPR reflection coefficients and layer impedances, which are indicative of the conduit's infill material. The spatial and temporal evolution of the reflection coefficients also provided insights into the morphology of the Rhonegletscher's englacial conduit network. During the summer melt seasons, we observed an active, water-filled, sediment-transporting englacial conduit network that yielded large negative GPR reflection coefficients (>-0:2). The GPR surveys conducted during the summer provided evidence that the englacial conduit was 15-20m±6m wide, ∼ 0:4m±0:35m thick, ∼ 250m±6m long with a shallow inclination (2°), and having a sinusoidal shape from the GPR data. We speculate that extensional hydraulic fracturing is responsible for the formation of the conduit as a result of the conduit network geometry observed and from borehole observations. Synthetic GPR waveform modelling using a thin water-filled conduit showed that a conduit thickness larger than 0.4m (0:3× minimum wavelength) thick can be correctly identified using 25MHz GPR data. During the winter periods, the englacial conduit no longer transports water and either physically closed or became very thin (< 0:1 m), thereby producing small negative reflection coefficients that are caused by either sediments lying within the closed conduit or water within the very thin conduit. Furthermore, the englacial conduit reactivated during the following melt season at an identical position as in the previous year. © 2020 Copernicus GmbH. All rights reserved.
英文关键词	geometry; ground penetrating radar; meltwater; network analysis; partition coefficient; seasonal variation; waveform analysis; Rhone Glacier [Valais]; Switzerland; Valais
语种	英语
来源期刊	Cryosphere
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/202052
作者单位	Laboratory of Hydraulics, Hydrology and Glaciology (VAW), ETH Zurich, Zurich, Switzerland; Institute of Geophysics, ETH Zurich, Zurich, Switzerland
推荐引用方式 GB/T 7714	Church G.,Grab M.,Schmelzbach C.,et al. Monitoring the seasonal changes of an englacial conduit network using repeated ground-penetrating radar measurements[J],2020,14(10).
APA	Church G.,Grab M.,Schmelzbach C.,Bauder A.,&Maurer H..(2020).Monitoring the seasonal changes of an englacial conduit network using repeated ground-penetrating radar measurements.Cryosphere,14(10).
MLA	Church G.,et al."Monitoring the seasonal changes of an englacial conduit network using repeated ground-penetrating radar measurements".Cryosphere 14.10(2020).