scholarly journals Interannual variability of glacier basal pressure from a 20 year record

2015 ◽  
Vol 56 (70) ◽  
pp. 33-44 ◽  
Author(s):  
Pierre-Marie Lefeuvre ◽  
Miriam Jackson ◽  
Gaute Lappegard ◽  
Jon Ove Hagen
Keyword(s):  
Interannual Variability ◽  
Load Transfer ◽  
Pearson Correlation ◽  
Drainage System ◽  
Stress Redistribution ◽  
Basal Pressure ◽  
Load Cells ◽  
Glacier Ice ◽  
Cavity Opening ◽  
Rock Interface

AbstractBasal pressure has been recorded at the Svartisen Subglacial Laboratory, northern Norway, for 20 years, and is measured by load cells installed at the ice–rock interface under ~200m of glacier ice. Synchronous pressure variations between load cells are investigated as evidence of stress redistribution and hydrological bed connectivity. A running Pearson correlation is used to study the temporal variation in the response of several sensors. By studying the nature of this correlation as well as the correlation between sensor pairs, it is possible to investigate the evolution of the degree of synchronous response, and to some extent basal connectivity, at the glacier bed. Persistent seasonal variations associated with the melt season are observed throughout the measurement period, indicating dependence on surface hydrological forcing. Overlying this pattern, specific years with longer periods of positive and negative correlation of pressure between sensors are presented to show contrasting interannual variability in basal pressure. An anticorrelated connectivity is associated with a local increase in the rate of daily subglacial discharge, and is caused by load transfer or passive cavity opening. Stable weather appears to enhance connectivity of the sensors, which is attributed to the development of a persistent drainage system and stress redistribution.

scholarly journals Towards Including Dynamic Vegetation Parameters in the EUMETSAT H SAF ASCAT Soil Moisture Products

2021 ◽  
Vol 13 (8) ◽  
pp. 1463
Author(s):  
Susan C. Steele-Dunne ◽  
Sebastian Hahn ◽  
Wolfgang Wagner ◽  
Mariette Vreugdenhil
Keyword(s):  
Soil Moisture ◽  
Interannual Variability ◽  
Incidence Angle ◽  
Pearson Correlation ◽  
The United States ◽  
Research Network ◽  
Window Width ◽  
High Frequency Variability ◽  
Vegetation Parameters ◽  
The Impact

The TU Wien Soil Moisture Retrieval (TUW SMR) approach is used to produce several operational soil moisture products from the Advanced Scatterometer (ASCAT) on the Metop series of satellites as part of the EUMETSAT Satellite Application Facility on Support to Operational Hydrology and Water Management (H SAF). The incidence angle dependence of backscatter is described by a second-order Taylor polynomial, the coefficients of which are used to normalize ASCAT observations to the reference incidence angle of 40∘ and for correcting vegetation effects. Recently, a kernel smoother was developed to estimate the coefficients dynamically, in order to account for interannual variability. In this study, we used the kernel smoother for estimating these coefficients, where we distinguished for the first time between their two uses, meaning that we used a short and fixed window width for the backscatter normalisation while we tested different window widths for optimizing the vegetation correction. In particular, we investigated the impact of using the dynamic vegetation parameters on soil moisture retrieval. We compared soil moisture retrievals based on the dynamic vegetation parameters to those estimated using the current operational approach by examining their agreement, in terms of the Pearson correlation coefficient, unbiased RMSE and bias with respect to in situ soil moisture. Data from the United States Climate Research Network were used to study the influence of climate class and land cover type on performance. The sensitivity to the kernel smoother half-width was also investigated. Results show that estimating the vegetation parameters with the kernel smoother can yield an improvement when there is interannual variability in vegetation due to a trend or a change in the amplitude or timing of the seasonal cycle. However, using the kernel smoother introduces high-frequency variability in the dynamic vegetation parameters, particularly for shorter kernel half-widths.

scholarly journals Mechanical forcing of water pressure in a hydraulically isolated reach beneath Western Greenland's ablation zone

2016 ◽  
Vol 57 (72) ◽  
pp. 62-70 ◽  
Author(s):  
Toby W. Meierbachtol ◽  
Joel T. Harper ◽  
Neil F. Humphrey ◽  
Patrick J. Wright
Keyword(s):  
Load Transfer ◽  
Water Pressure ◽  
Drainage System ◽  
Hot Water ◽  
Diurnal Changes ◽  
Basal Cavity ◽  
In Situ Investigation ◽  
Borehole Water ◽  
Borehole Drilling ◽  
Thermal Signature

ABSTRACTA suite of surface and basal measurements during and after borehole drilling is used to perform in situ investigation of the local basal drainage system and pressure forcing in western Greenland. Drill and borehole water temperature were monitored during borehole drilling, which was performed with dyed hot water. After drilling, borehole water pressure and basal dye concentration were measured concurrently with positions in a GPS strain diamond at the surface. Water pressure exhibited diurnal changes in antiphase with velocity. Dye monitoring in the borehole revealed stagnant basal water for nearly 2 weeks. The interpretation of initial connection to an isolated basal cavity is corroborated by the thermal signature of borehole water during hot water drilling. Measurement-based estimates of cavity size are on the order of cubic meters, and analysis indicates that small changes in its volume could induce the observed pressure variations. It is found that longitudinal coupling effects are unable to force necessary volume changes at the site. Sliding-driven basal cavity opening and elastic uplift from load transfer are plausible mechanisms controlling pressure variations. Elastic uplift requires forcing from a hydraulically connected reach, which observations suggest must be relatively small and in close proximity to the isolated cavity.

scholarly journals HUBUNGAN ANTARA SEDIMEN DENGAN LOGAM BERAT DAN MAKROZOOBENTOS DI SUNGAI SIANGKER, SEMARANG

2016 ◽  
Vol 5 (4) ◽  
pp. 337-344
Author(s):  
Arini Indah Lestari ◽  
Mustofa Niti Supardjo ◽  
Boedi Hendrarto
Keyword(s):  
Heavy Metals ◽  
Principle Component Analysis ◽  
Random Sampling ◽  
Pearson Correlation ◽  
Drainage System ◽  
Component Analysis ◽  
Sediment Characteristics ◽  
The West ◽  
Principle Component ◽  
The Relationship

ABSTRAK Sungai Siangker merupakan salah satu sub sistem dari sistem drainase Semarang Barat yang mengalami pendangkalan.Limbah yang berasal dari pabrik diduga mengandung logam berat Pb dan Cd. Oleh karena itu, penelitian ini diadakan untuk mengetahui kadar logam berat Pb dan Cd dan hubungan antara sedimen serta kandungan logam berat Pb dan Cd dengan komunitas makrozoobentos. Pengambilan sampel dilakukan secara random  sampling. PCA (Principle Component Analysis) digunakan untuk mengetahui kedekatan hubungan antara makrozoobentos, nilai bahan organik dan karakteristik sedimen.Perbedaan variabel tiap stasiunnya diuji dengan Uji Kruskal-Wallis. Korelasi Pearson digunakan untuk menganalisis hubungan antara variabel kelimpahan, keanekaragaman, kadar logam berat dan karakteristik sedimen di tiap stasiunnya. Hasil rerata yang diperoleh dari analisa kadar logam berat (Pb) di muara dan sungai Siangker adalah 1,10 – 1,64 mg/l,  sedangkan untuk rerata (Cd) sebesar 0,13 – 0,43 mg/l. Kadar debu mempunyai korelasi positif yang erat (p < 0,05) dengan keanekaragaman dan kelimpahan makrozoobentos. Kadar logam berat berpengaruh nyata (p < 0,05) terhadap keanekaragaman maupun kelimpahan makrozoobentos. Kata Kunci : Sungai, logam berat, karakteristik sedimen, makrozoobentos  ABSTRACTSiangker river is one of the sub-systems of the West Semarang drainage system that experiencing siltation. Waste from the factories is suspected to contain heavy metals (Pb) and (Cd). This study was conducted to understand concentration of Pb and Cd and the relationship between characteristics of the sediments containing heavy metals (Pb) and (Cd) as well as macrozoobenthos community. Sampling was done by random sampling. PCA (Principle Component Analysis) was used to determine proximity of the relationships between macrozoobenthos and the value of organic matter as well as sediment characteristics. Meanwhile, the differences in the station of each variable was tested using Kruskal-Wallis test. Pearson correlation was used to analyze the relationship between abundance variables, diversity, the levels of heavy metals and sediment characteristics in each station. The results showed that the levels of heavy metals (Pb) in the estuary and  river Siangker were  1,10 to 1,64 mg / l, while concentration of  (Cd) is 0,13 to 0,43 mg / l. Dust levels were closely positively correlated (p < 0,05) with the diversity and abundance of macrozoobenthos. Levels of heavy metals was significant (p < 0,05) for the diversity and abundance of macrozoobenthos.     Keywords : River, heavy metal, sediment characteristic, macrozoobenthos

scholarly journals Criterion and Construct Validity of Prosthesis-Integrated Measurement of Joint Moment Data in Persons With Transtibial Amputation

2014 ◽  
Vol 30 (3) ◽  
pp. 431-438 ◽  
Author(s):  
Goeran Fiedler ◽  
Brooke Slavens ◽  
Roger O. Smith ◽  
Douglas Briggs ◽  
Brian J. Hafner
Keyword(s):  
Construct Validity ◽  
Gait Analysis ◽  
Pearson Correlation ◽  
Measurement Methods ◽  
Load Cell ◽  
Joint Moments ◽  
Transtibial Amputation ◽  
Study Results ◽  
Flexion Extension ◽  
Load Cells

Prosthesis-integrated sensors are appealing for use in clinical settings where gait analysis equipment is unavailable, but accurate knowledge of patients’ performance is desired. Data obtained from load cells (inferring joint moments) may aid clinicians in the prescription, alignment, and gait rehabilitation of persons with limb loss. The purpose of this study was to assess the accuracy of prosthesis-integrated load cells for routine use in clinical practice. Level ground walking of persons with transtibial amputation was concurrently measured with a commercially available prosthesis-integrated load cell, a 10-camera motion analysis system, and piezoelectric force plates. Ankle and knee flexion/extension moments were derived and measurement methods were compared via correlation analysis. Pearson correlation coefficients ranged from 0.661 for ankle pronation/supination moments to 0.915 for ankle flexion/extension moments (P < .001). Root mean squared errors between measurement methods were in the magnitude of 10% of the measured range and were explainable. Differences in results depicted differences between systems in definition and computation of measurement variables. They may not limit clinical use of the load cell, but should be considered when data are compared directly to conventional gait analysis data. Construct validity of the load cell (ie, ability to measure joint moments in-situ) is supported by the study results.

scholarly journals Seasonal Variation of Drainage System in the Lower Ablation Area of a Monsoonal Temperate Debris-Covered Glacier in Mt. Gongga, South-Eastern Tibet

Water ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 1050 ◽  
Author(s):  
Qiao Liu ◽  
Shiyin Liu ◽  
Wulong Cao
Keyword(s):  
Seasonal Variation ◽  
Dispersion Model ◽  
Drainage System ◽  
Hydrodynamic Dispersion ◽  
Ablation Area ◽  
Advection Dispersion ◽  
Dye Tracer ◽  
Eastern Tibet ◽  
Glacier Ice ◽  
Subglacial Drainage

Seasonal evolution of the subglacial drainage system in the lower ablation area of the Hailuogou glacier ice tongue were revealed by repeated dye tracer (Rhodamine WT) experiments during the 2009 ablation season. Between April and October, 18 dye tracer experiments were conducted by injecting the tracer at one location of the lower ablation area of the Hailuogou Glacier to diagnose the seasonal variation of the subglacial drainage system of this section of glacier ice tongue. Using a simple advection-dispersion model (ADM), the flow velocity, hydrodynamic dispersion coefficient, and degree of tracer spreading were deduced. Tracer transit velocity through the tested subglacial channel varied from 0.148 to 0.555 m s−1 during the 2009 ablation season. Dispersivity showed a relatively high value than that found at other glaciers, which varied between 27.05 and 287.49 m2 s−1. Seasonal changes of these indexes indicated that the subglacial drainage system of the lower ablation area of the Hailougou Glacier is a relatively stable existing system in the case of its longitudinal shape, whereas its hydraulic efficiency is low in the early and late ablation seasons and high during the middle of summer due to subglacial channel expansion.

Rock Glaciers of the Dalton Range, Kluane Ranges, South-West Yukon Territory, Canada

1988 ◽  
Vol 34 (118) ◽  
pp. 327-332 ◽  
Author(s):  
Peter G. Johnson ◽  
Diane Lacasse
Keyword(s):  
Late Pleistocene ◽  
Lower Cretaceous ◽  
Drainage System ◽  
Upper Jurassic ◽  
Yukon Territory ◽  
High Susceptibility ◽  
Frost Action ◽  
South West ◽  
Glacier Ice ◽  
Rock Glaciers

Abstract Glaciated valleys of the Dalton Range in the south-west Yukon Territory are dominated by rock glaciers identified as glacier ice-cored debris systems. The two rock glaciers studied have different amounts of deformation at present, resulting from post-formation mechanics. The primary formation of lobes of the rock glaciers resulted from periods of glacier activity in the Neoglacial, although older lobes, probably late Pleistocene in age, occur below the Neoglacial lobes. The hydrological systems of the rock glaciers have played a major role in the post-formation deformation of the land forms and the present drainage system is entirely sub-surface. The explanation for the extensive occurrence of rock glaciers in the Dalton Range is lithological as a result of the high susceptibility of the Upper Jurassic/Lower Cretaceous sediments to frost action and glacier erosion.

scholarly journals Rock Glaciers of the Dalton Range, Kluane Ranges, South-West Yukon Territory, Canada

1988 ◽  
Vol 34 (118) ◽  
pp. 327-332
Author(s):  
Peter G. Johnson ◽  
Diane Lacasse
Keyword(s):  
Late Pleistocene ◽  
Lower Cretaceous ◽  
Drainage System ◽  
Upper Jurassic ◽  
Yukon Territory ◽  
High Susceptibility ◽  
Frost Action ◽  
South West ◽  
Glacier Ice ◽  
Rock Glaciers

AbstractGlaciated valleys of the Dalton Range in the south-west Yukon Territory are dominated by rock glaciers identified as glacier ice-cored debris systems. The two rock glaciers studied have different amounts of deformation at present, resulting from post-formation mechanics.The primary formation of lobes of the rock glaciers resulted from periods of glacier activity in the Neoglacial, although older lobes, probably late Pleistocene in age, occur below the Neoglacial lobes. The hydrological systems of the rock glaciers have played a major role in the post-formation deformation of the land forms and the present drainage system is entirely sub-surface. The explanation for the extensive occurrence of rock glaciers in the Dalton Range is lithological as a result of the high susceptibility of the Upper Jurassic/Lower Cretaceous sediments to frost action and glacier erosion.

scholarly journals Analysis of Vertical Response of Drilled Pile at the Crest of Rock Slope Based on Shear Behavior

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Chong Jiang ◽  
Ju Fang ◽  
Bowen Sun
Keyword(s):  
Analytical Solution ◽  
Rock Slope ◽  
Load Transfer ◽  
Rock Properties ◽  
Vertical Load ◽  
Modified Model ◽  
Difference Analysis ◽  
Side Resistance ◽  
Rock Interface ◽  
Shear Behaviors

This paper proposed a method for analysis of a drilled pile under vertical load at the crest of rock slope. Based on wedge theory, a modified model of normal stiffness of socket wall affected by the slope is obtained. Analyze the shear behaviors of the pile-rock interface, an analytical solution of load transfer of pile at the crest of rock slope is obtained. To evaluate the accuracy of the new method, this method is compared with the results of finite difference analysis. Finally, the method is used to analyze the effect of slope, pile, and rock properties on the unit side resistance and axial force.

scholarly journals Analysis of the changes in the lacrimal system before and after endoscopic dacryocystorhinostomy

2020 ◽  
Author(s):  
Sha Li ◽  
Yijun Zheng ◽  
Yong Zhang ◽  
Lin Chen
Keyword(s):  
Pearson Correlation ◽  
Drainage System ◽  
Select Committee ◽  
Dry Eyes ◽  
Endoscopic Dacryocystorhinostomy ◽  
Lacrimal System ◽  
Significant Difference ◽  
Before And After ◽  
Highly Correlated ◽  
Tear Meniscus Height

Abstract BackgroundWe aimed to analys and explore the changes in the lacrimal system before and after endoscopic dacryocystorhinostomy (EN-DCR).MethodsA series of case studies was reviewed. The clinical data of 104 patients (120 eyes) who underwent EN-DCR in our hospital from March 2019 to October 2019 were selected for the study. The tear meniscus height (TMH) and the Schirmer I test (SIt) values were compared preoperatively and 1 month and 3 months postoperatively and statistically analysed by Mauchly's test of sphericity and the Pearson correlation coefficient.ResultsThe TMH decreased across all 3 timepoints, and the differences were statistically significant (P<0.05). The TMH values were measured 3 times in 120 eyes and showed three patterns: increased steadily (34 eyes), descended first and then ascended (32 eyes), and decreased steadily (54 eyes); the changes in the three patterns were statistically significant (P<0.05). There were a significant increases in SIt values among the three timepoints, and the SIt values gradually increased when the SIt values were < 10 mm/5 min preoperatively. However, there was no significant difference in SIt values when the SIt values were ≥ 10 mm/5 min preoperatively. The TMH was highly correlated with the SIt value preoperatively (r = 0.763), moderately correlated at 1 month postoperatively (r = 0.515), and not correlated at 3 months postoperatively (r = 0.097).ConclusionsEN-DCR has a certain degree of influence on the tear system, which is not only reflected in the tear drainage system, but also in the tear secretion system and the interaction between the two systems; however, excess tear drainage, can also alleviate dry eyes.Funding programmeJoint Fund Project of Hubei Provincial Health Select Committee (No. WJ2019H318); General Key Projects of Medical Research in Wuhan City, Hubei Province (No. WX19A03)

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