scholarly journals A wireless subglacial probe for deep ice applications

2012 ◽  
Vol 58 (211) ◽  
pp. 841-848 ◽  
Author(s):  
C.J.P.P. Smeets ◽  
W. Boot ◽  
A. Hubbard ◽  
R. Pettersson ◽  
F. Wilhelms ◽  
...  
Keyword(s):  
Water Pressure ◽  
Greenland Ice Sheet ◽  
Depth Range ◽  
Measured Temperature ◽  
Transmission Power ◽  
The West ◽  
System A ◽  
Antenna Type ◽  
First Results ◽  
Good Agreement

AbstractWe present the design and first results from two experiments using a wireless subglacial sensor system (WiSe) that is able to transmit data through 2500 m thick ice. Energy consumption of the probes is minimized, enabling the transmission of data for at least 10 years. In July 2010 the first prototype of the system was used to measure subglacial pressure at the base and a temperature profile consisting of 23 probes in two 600 m deep holes at Russell Glacier, a land-terminating part of the West Greenland ice sheet near Kangerlussuaq. The time series of subglacial pressure show very good agreement between data from the WiSe system and the wired reference system. The wireless-measured temperature data were validated by comparison with the theoretical decrease of melting point with water pressure inside the water-filled hole directly after installation. To test the depth range of the WiSe system a second experiment using three different probe types and two different surface antennas was performed inside the 2537 m deep hole at NEEM. It is demonstrated that, with the proper combination of transmission power and surface antenna type, the WiSe system transmits data through 2500 m thick ice.

scholarly journals Analyses of Two Ice Cores Drilled at the Ice-Sheet Margin in West Greenland

1988 ◽  
Vol 10 ◽  
pp. 23-27 ◽  
Author(s):  
H.B. Clausen ◽  
B. Stauffer
Keyword(s):  
Flow Line ◽  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
The West ◽  
Surface Samples ◽  
Insight Into

In 1978 two ice cores were drilled to depths of 46 and 92 m respectively at Camp 3, at the west margin of the Greenland ice sheet. Both core drillings reached bedrock. In addition, surface samples were collected in the marginal area along an estimated flow line.The δl8O profiles of the two ice cores and of the surface samples show similar features. All three δ180 records reveal the characteristic shift (of 5–6 per mil for the Pleistocene-Holocene transition 11 000 years ago) observed in Greenland deep ice cores from Camp Century and Dye 3.The δ18O results, as well as the measured temperature profiles in the bore holes, are used to provide more insight into the rheology of the ice sheet. The analyses of marginal ice samples is an important supplement to deep ice-core analyses.

scholarly journals Analyses of Two Ice Cores Drilled at the Ice-Sheet Margin in West Greenland

1988 ◽  
Vol 10 ◽  
pp. 23-27 ◽  
Author(s):  
H.B. Clausen ◽  
B. Stauffer
Keyword(s):  
Flow Line ◽  
Ice Core ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Ice Cores ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
The West ◽  
Surface Samples ◽  
Insight Into

In 1978 two ice cores were drilled to depths of 46 and 92 m respectively at Camp 3, at the west margin of the Greenland ice sheet. Both core drillings reached bedrock. In addition, surface samples were collected in the marginal area along an estimated flow line. The δl8O profiles of the two ice cores and of the surface samples show similar features. All three δ180 records reveal the characteristic shift (of 5–6 per mil for the Pleistocene-Holocene transition 11 000 years ago) observed in Greenland deep ice cores from Camp Century and Dye 3. The δ18O results, as well as the measured temperature profiles in the bore holes, are used to provide more insight into the rheology of the ice sheet. The analyses of marginal ice samples is an important supplement to deep ice-core analyses.

Estimating the Wall Heat Flux of Unsteady Conjugated Forced Convection Between Two Corotating Disks Using an Inverse Solution Scheme

2008 ◽  
Vol 130 (12) ◽  
Author(s):  
David T. W. Lin ◽  
Hung Yi Li ◽  
Wei Mon Yan
Keyword(s):  
Heat Flux ◽  
Forced Convection ◽  
Boundary Surface ◽  
Temperature Sensors ◽  
Inverse Solution ◽  
Wall Heat Flux ◽  
Unknown Boundary ◽  
Measured Temperature ◽  
Solution Scheme ◽  
Good Agreement

An inverse solution scheme based on the conjugate gradient method with the minimization of the object function is presented for estimating the unknown wall heat flux of conjugated forced convection flows between two corotating disks from temperature measurements acquired within the flow field. The validity of the proposed approach is demonstrated via the estimation of three time- and space-dependent heat flux profiles. A good agreement is observed between the estimated results and the exact solution in every case. In general, the accuracy of the estimated results is found to improve as the temperature sensors are moved closer to the unknown boundary surface and the error in the measured temperature data is reduced.

scholarly journals Reconstruction of historical surface mass balance, 1984–2017 from GreenTrACS multi-offset ground-penetrating radar

2020 ◽  
pp. 1-10
Author(s):  
Tate G. Meehan ◽  
H. P. Marshall ◽  
John H. Bradford ◽  
Robert L. Hawley ◽  
Thomas B. Overly ◽  
...  
Keyword(s):  
Mass Balance ◽  
Ground Penetrating Radar ◽  
Greenland Ice Sheet ◽  
Snow Accumulation ◽  
Surface Mass Balance ◽  
Snow Density ◽  
Surface Mass ◽  
Age Model ◽  
Ground Penetrating ◽  
Good Agreement

Abstract We present continuous estimates of snow and firn density, layer depth and accumulation from a multi-channel, multi-offset, ground-penetrating radar traverse. Our method uses the electromagnetic velocity, estimated from waveform travel-times measured at common-midpoints between sources and receivers. Previously, common-midpoint radar experiments on ice sheets have been limited to point observations. We completed radar velocity analysis in the upper ~2 m to estimate the surface and average snow density of the Greenland Ice Sheet. We parameterized the Herron and Langway (1980) firn density and age model using the radar-derived snow density, radar-derived surface mass balance (2015–2017) and reanalysis-derived temperature data. We applied structure-oriented filtering to the radar image along constant age horizons and increased the depth at which horizons could be reliably interpreted. We reconstructed the historical instantaneous surface mass balance, which we averaged into annual and multidecadal products along a 78 km traverse for the period 1984–2017. We found good agreement between our physically constrained parameterization and a firn core collected from the dry snow accumulation zone, and gained insights into the spatial correlation of surface snow density.

V64 The Phorbas system – a new single incision adjustable male sling: Implantation technique and first results

2014 ◽  
Vol 13 (1) ◽  
pp. eV64 ◽  
Author(s):  
R.M. Bauer ◽  
S. Herschorn ◽  
T.B. Olmedo ◽  
O.D. Reyes ◽  
W. Huebner
Keyword(s):  
Single Incision ◽  
Implantation Technique ◽  
Male Sling ◽  
System A ◽  
First Results

The Possibility of Visualizing Temperature Fields Using Digital Holographic Interferometry

2013 ◽  
Vol 284-287 ◽  
pp. 988-995 ◽  
Author(s):  
Tomáš Vít ◽  
Vít Lédl ◽  
Roman Dolecek ◽  
Pavel Psota
Keyword(s):  
Holographic Interferometry ◽  
Rapid Change ◽  
Optical Methods ◽  
Temperature Fields ◽  
Constant Current ◽  
Special Technique ◽  
Limiting Factor ◽  
Measured Temperature ◽  
Hot Wire ◽  
First Results

The presented paper compares results of measured temperature fields achieved by digital holographic interferometry (DHI) and hot wire anemometry. It shows the possibility of using holographic interferometry for the visualization of temperature fields in periodically moving fluids. The measurement of temperature fields in moving fluids has many inherent difficulties. The usage of point temperature measurement methods, such as Constant Current Anemometry (CCA), is limited to frequencies up to 3000 Hz. This frequency should be the limiting factor for using CCA in fluids when a rapid change of temperature occurs. This shortcoming of CCA measurements could be overcome through the use of optical methods such as digital holographic interferometry. It is necessary to employ a special holographic setup with double sensitivity instead of the commonly used Mach-Zehnder type of holographic interferometer in order to attain parameters sufficient for the studied case. This setup is not as light-efficient as the Mach-Zehnder type but has double sensitivity. The special technique of acquiring and phase averaging the results from holographic interferometry is presented. The paper also shows the first results of an evaluated 3D temperature field.

Design of differential-mode bandpass filter with common-mode suppression using ring dielectric resonator

2016 ◽  
Vol 9 (5) ◽  
pp. 1029-1035 ◽  
Author(s):  
Jugul Kishor ◽  
Binod K. Kanaujia ◽  
Santanu Dwari ◽  
Ashwani Kumar
Keyword(s):  
Dielectric Resonator ◽  
High Performance ◽  
Bandpass Filter ◽  
Ring Resonator ◽  
Differential Mode ◽  
Common Mode ◽  
Mode Suppression ◽  
Transmission Zeros ◽  
System A ◽  
Good Agreement

Synthesis of differential-mode bandpass filter (BPF) with good common-mode suppression has been described and demonstrated on the basis of ring dielectric resonator (RDR) for high-performance communication system. A RDR with two pairs of feeding lines has been used to excite TE01δ-mode. This unique combination of feeding lines and the ring resonator creates a differential passband. Meanwhile, TM01δ-mode of the DR can also be excited to achieve common-mode rejection in the stopband. Transmission zeros are created in the lower and upper stopband to further improve the selectivity of the proposed BPF. A second-order differential BPF is designed, fabricated and its performance is measured to validate the concept. There is good agreement between simulated and measured results.

Greenland land-terminating glaciers velocity trends during the last two decades

2021 ◽  
Author(s):  
Paul Halas ◽  
Jeremie Mouginot ◽  
Basile de Fleurian ◽  
Petra Langebroek
Keyword(s):  
Water Pressure ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Surface Melting ◽  
Limited Area ◽  
Ice Dynamics ◽  
Basal Sliding ◽  
Surface Melt ◽  
Ice Sheet Dynamics ◽  
The Impact

<div> <p>Ice losses from the Greenland Ice Sheet have been increasing in the last two decades, leading to a larger contribution to the global sea level rise. Roughly 40% of the contribution comes from ice-sheet dynamics, mainly regulated by basal sliding. The sliding component of glaciers has been observed to be strongly related to surface melting, as water can eventually reach the bed and impact the subglacial water pressure, affecting the basal sliding.  </p> </div><div> <p>The link between ice velocities and surface melt on multi-annual time scale is still not totally understood even though it is of major importance with expected increasing surface melting. Several studies showed some correlation between an increase in surface melt and a slowdown in velocities, but there is no consensus on those trends. Moreover those investigations only presented results in a limited area over Southwest Greenland.  </p> </div><div> <p>Here we present the ice motion over many land-terminating glaciers on the Greenland Ice Sheet for the period 2000 - 2020. This type of glacier is ideal for studying processes at the interface between the bed and the ice since they are exempted from interactions with the sea while still being relevant for all glaciers since they share the same basal friction laws. The velocity data was obtained using optical Landsat 7 & 8 imagery and feature-tracking algorithm. We attached importance keeping the starting date of our image pairs similar, and avoided stacking pairs starting before and after melt seasons, resulting in multiple velocity products for each year.  </p> </div><div> <p>Our results show similar velocity trends for previously studied areas with a slowdown until 2012 followed by an acceleration. This trend however does not seem to be observed on the whole ice sheet and is probably specific to this region’s climate forcing. </p> </div><div> <p>Moreover comparison between ice velocities from different parts of Greenland allows us to observe the impact of different climatic trends on ice dynamics.</p> </div>

scholarly journals Topographic and Glaciological Controls on Holocene Ice-Sheet Margin Dynamics. Central West Greenland

1990 ◽  
Vol 14 ◽  
pp. 307-310 ◽  
Author(s):  
C.R. Warren ◽  
N.R.J. Hulton
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Glacial Maximum ◽  
Warm Climate ◽  
Short Term ◽  
The West ◽  
West Greenland ◽  
The Past

The retreat of the West Greenland ice sheet from its Sisimiut (Wisconsinan) glacial maximum, was punctuated by a series of Stillstands or small readvances that formed numerous moraines. These landforms have been interpreted in the past as the result of short-term, regional falls in ablation-season temperatures. However, mapping of the geomorphological evidence south of Ilulissat (Jakobshavn) suggests that retreat behaviour was not primarily governed by climate, and therefore that the former ice margins are not palaeoclimatically significant. During warm climate ice-sheet wastage, the successive quasi-stable positions adopted by the ice margin were largely governed by topography. The retreat of the inherently unstable calving glaciers was arrested only at topographically-determined locations where stability could be achieved.

Stability of Water-Lubricated, Hydrostatic, Conical Bearings With Spiral Grooves for High-Speed Spindles

2001 ◽  
Vol 124 (2) ◽  
pp. 398-405 ◽  
Author(s):  
S. Yoshimoto ◽  
S. Oshima ◽  
S. Danbara ◽  
T. Shitara
Keyword(s):  
High Speed ◽  
Water Pressure ◽  
Rotating Shaft ◽  
Pressurized Water ◽  
High Speeds ◽  
Theoretical Predictions ◽  
The Stability ◽  
Stability Of Water ◽  
Spiral Grooves ◽  
Good Agreement

In this paper, the stability of water-lubricated, hydrostatic, conical bearings with spiral grooves for high-speed spindles is investigated theoretically and experimentally. In these bearing types, pressurized water is first fed to the inside of the rotating shaft and then introduced into spiral grooves through feeding holes located at one end of each spiral groove. Therefore, water pressure is increased due to the effect of the centrifugal force at the outlets of the feeding holes, which results from shaft rotation. In addition, water pressure is also increased by the viscous pumping effect of the spiral grooves. The stability of the proposed bearing is theoretically predicted using the perturbation method, and calculated results are compared with experimental results. It was consequently found that the proposed bearing is very stable at high speeds and theoretical predictions show good agreement with experimental data.

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