scholarly journals Ice tectonic deformation during the rapid in situ drainage of a supraglacial lake on the Greenland Ice Sheet

2013 ◽  
Vol 7 (1) ◽  
pp. 129-140 ◽  
Author(s):  
S. H. Doyle ◽  
A. L. Hubbard ◽  
C. F. Dow ◽  
G. A. Jones ◽  
A. Fitzpatrick ◽  
...  
Keyword(s):  
Global Positioning System ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Tectonic Deformation ◽  
Positioning System ◽  
Differential Motion ◽  
Global Positioning ◽  
Lake Drainage ◽  
Lake Record

Abstract. We present detailed records of lake discharge, ice motion and passive seismicity capturing the behaviour and processes preceding, during and following the rapid drainage of a 4 km2 supraglacial lake through 1.1-km-thick ice on the western margin of the Greenland Ice Sheet. Peak discharge of 3300 m3 s−1 coincident with maximal rates of vertical uplift indicates that surface water accessed the ice–bed interface causing widespread hydraulic separation and enhanced basal motion. The differential motion of four global positioning system (GPS) receivers located around the lake record the opening and closure of the fractures through which the lake drained. We hypothesise that the majority of discharge occurred through a 3-km-long fracture with a peak width averaged across its wetted length of 0.4 m. We argue that the fracture's kilometre-scale length allowed rapid discharge to be achieved by combining reasonable water velocities with sub-metre fracture widths. These observations add to the currently limited knowledge of in situ supraglacial lake drainage events, which rapidly deliver large volumes of water to the ice–bed interface.

scholarly journals GPS based surface displacements – a proxy for discharge and sediment transport from the Greenland Ice Sheet

2014 ◽  
Vol 8 (4) ◽  
pp. 3829-3850 ◽  
Author(s):  
B. Hasholt ◽  
S. A. Khan ◽  
A. B. Mikkelsen
Keyword(s):  
Sediment Transport ◽  
Global Positioning System ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Winter Precipitation ◽  
Annual Runoff ◽  
Surface Displacements ◽  
Global Positioning ◽  
Loss Of Mass ◽  
Gps Observations

Abstract. The elastic respond of the Earth's surface to mass changes has been measured with Global Positioning System (GPS). Mass loss as accumulated runoff and sediment transport from a 10 000 km2 segment of the Greenland Ice Sheet (GrIS) correlated very well (R2 = 0.83) with GPS measured uplift. Accumulated winter precipitation correlated fairly well with surface depression (R2 = 0.69). The relationships are based on seven years of runoff and sediment transport observations from the Watson River (2007–2013), winter precipitation from Kangerlussuaq Airport and GPS observations at Kellyville. GPS recordings of surface subsidence and uplift from 1996–2013 are used to calculate 18 years time series of annual runoff, sediment and solute transport and winter precipitation. Runoff and related transport of sediment and solutes increase over the period, while winter precipitation (land depression) tends to decrease. Based on the entire GPS record (1996–2013), it is shown that until 2005–2006 the mass balance of this segment of the GrIS was rather stable – since then there has been an increasing loss of mass, culminating in 2012.

scholarly journals Measurement of Environmental Gamma Dose at AECD Campus of Bangladesh

2014 ◽  
Vol 6 (2) ◽  
pp. 285-291 ◽  
Author(s):  
M. S. Rahman ◽  
M. A. Islam ◽  
A. Begum ◽  
M. M. Rahman ◽  
M. H. Ahsan
Keyword(s):  
Dose Rate ◽  
Global Positioning System ◽  
Hpge Detector ◽  
Gamma Ray ◽  
Gamma Dose ◽  
Positioning System ◽  
Gps Navigation ◽  
Global Positioning ◽  
Measured Dose

A portable HPGe detector has been employed to assess environmental gamma-ray dose following in-situ technique from the primordial radionuclide 40K in the soil at 15 monitoring points (MPs) in the environment at the Atomic Energy Centre, Dhaka (AECD) campus, Bangladesh. The MPs were marked-out using Global Positioning System (GPS) navigation. The measured dose rate due to 40K range from 0.0428 µGy.h-1 to 0.1222 µGy.h-1 with an average of 0.0828 ± 0.0225 µGy.h-1. Keywords: Gamma; Environment; Dose rate.© 2014 JSR Publications. ISSN: 2070-0237 (Print); 2070-0245 (Online). All rights reserved. doi: http://dx.doi.org/10.3329/jsr.v6i2.17146 J. Sci. Res. 6 (2), 285-291 (2014)  

scholarly journals One century of tectonic deformation along the Sumatran fault from triangulation and Global Positioning System surveys

2000 ◽  
Vol 105 (B12) ◽  
pp. 28343-28361 ◽  
Author(s):  
L. Prawirodirdjo ◽  
Y. Bock ◽  
J. F. Genrich ◽  
S. S. O. Puntodewo ◽  
J. Rais ◽  
...  
Keyword(s):  
Global Positioning System ◽  
Tectonic Deformation ◽  
Positioning System ◽  
Global Positioning ◽  
Sumatran Fault

scholarly journals Supraglacial lake drainage at a fast-flowing Greenlandic outlet glacier

2019 ◽  
Vol 116 (51) ◽  
pp. 25468-25477 ◽  
Author(s):  
Thomas R. Chudley ◽  
Poul Christoffersen ◽  
Samuel H. Doyle ◽  
Marion Bougamont ◽  
Charlotte M. Schoonman ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Dynamic Responses ◽  
Surface Velocity ◽  
Outlet Glacier ◽  
Direct Observations ◽  
Ice Surface ◽  
Ice Sheet Dynamics ◽  
Lake Drainage

Supraglacial lake drainage events influence Greenland Ice Sheet dynamics on hourly to interannual timescales. However, direct observations are rare, and, to date, no in situ studies exist from fast-flowing sectors of the ice sheet. Here, we present observations of a rapid lake drainage event at Store Glacier, west Greenland, in 2018. The drainage event transported 4.8 × 106m3of meltwater to the glacier bed in ∼5 h, reducing the lake to a third of its original volume. During drainage, the local ice surface rose by 0.55 m, and surface velocity increased from 2.0 m⋅d−1to 5.3 m⋅d−1. Dynamic responses were greatest ∼4 km downstream from the lake, which we interpret as an area of transient water storage constrained by basal topography. Drainage initiated, without any precursory trigger, when the lake expanded and reactivated a preexisting fracture that had been responsible for a drainage event 1 y earlier. Since formation, this fracture had advected ∼500 m from the lake’s deepest point, meaning the lake did not fully drain. Partial drainage events have previously been assumed to occur slowly via lake overtopping, with a comparatively small dynamic influence. In contrast, our findings show that partial drainage events can be caused by hydrofracture, producing new hydrological connections that continue to concentrate the supply of surface meltwater to the bed of the ice sheet throughout the melt season. Our findings therefore indicate that the quantity and resultant dynamic influence of rapid lake drainages are likely being underestimated.

scholarly journals Underwater Doppler Navigation with Self-calibration

2015 ◽  
Vol 69 (2) ◽  
pp. 295-312 ◽  
Author(s):  
Xianfei Pan ◽  
Yuanxin Wu
Keyword(s):  
Global Positioning System ◽  
Autonomous Navigation ◽  
Doppler Velocity ◽  
Positioning System ◽  
Combined System ◽  
Inertial Measurement ◽  
Global Positioning ◽  
Measurement Units ◽  
Underwater Navigation

Precise autonomous navigation remains a substantial challenge to all underwater platforms. Inertial Measurement Units (IMU) and Doppler Velocity Logs (DVL) have complementary characteristics and are promising sensors that could enable fully autonomous underwater navigation in unexplored areas without relying on additional external Global Positioning System (GPS) or acoustic beacons. This paper addresses the combined IMU/DVL navigation system from the viewpoint of observability. We show by analysis that under moderate conditions the combined system is observable. Specifically, the DVL parameters, including the scale factor and misalignment angles, can be calibrated in-situ without using external GPS or acoustic beacon sensors. Simulation results using a practical estimator validate the analytic conclusions.

scholarly journals Finding and characterizing hidden dips in roads

2015 ◽  
Vol 10 (4) ◽  
pp. 340-345 ◽  
Author(s):  
María Castro ◽  
Alejandro de Blas ◽  
Roberto Rodríguez-Solano ◽  
José Angel Sánchez
Keyword(s):  
Information System ◽  
Geographic Information System ◽  
Global Positioning System ◽  
Video Camera ◽  
Geographic Information ◽  
Positioning System ◽  
Global Positioning ◽  
Quantitative Procedure

Sometimes when connecting a crest vertical curve, followed by a sag and another crest, a road disappears from the view of a driver to reappear later. Then, there is a loss of path or a hidden dip in a road. It is essential to avoid losses when they hide dangerous points, such as intersections or unexpected changes in direction. In addition, this loss disrupts drivers and its effect depends on quantitative relationships between the variables involved in the problem. This paper presents a quantitative procedure for studying hidden dips in roads. The method is based on calculating the sections visible and hidden by a driver using a Geographic Information System. An application to a Spanish road is presented. Procedure results were compared with in situ carried out studies and with a video of the highway recorded using a Global Positioning System equipped video camera embarked in a vehicle. The main quantitative issues related to hidden dips are discussed.

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