Meltwater flow through a rapidly deglaciating glacier and foreland catchment system: Virkisjökull, SE Iceland

Abstract Virkisjökull is a rapidly retreating glacier in south-east Iceland. A proglacial lake has formed in the last ten years underlain by buried ice. In this study we estimate water velocities through the glacier, proglacial foreland and proglacial river using tracer tests and continuous meltwater flow measurements. Tracer testing from a glacial moulin to the glacier outlet in September 2013 demonstrated a rapid velocity of 0.58 m s−1. This was comparable to the velocity within the proglacial river, also estimated from tracer testing. A subsequent tracer test from the same glacial moulin under low flow conditions in May 2014 demonstrated a slower velocity of 0.07 m s−1. The glacier outlet river sinks back into the buried ice, and a tracer test from this sink point through the proglacial foreland to the meltwater river beyond the lake indicated a velocity of 0.03 m s−1, suggesting that an ice conduit system within the buried ice is transferring water rapidly beneath the lake. Ground penetrating radar profiles confirm the presence of this buried conduit system. This study provides an example of rapid deglaciation being associated with extensive conduit systems that enable rapid meltwater transfer from glaciers through the proglacial area to meltwater rivers.

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Hydrogeology of an alpine rockfall aquifer system and its role in flood attenuation and maintaining baseflow

Hydrology and Earth System Sciences Discussions ◽

10.5194/hessd-11-6805-2014 ◽

2014 ◽

Vol 11 (6) ◽

pp. 6805-6841 ◽

Cited By ~ 1

Author(s):

U. Lauber ◽

P. Kotyla ◽

D. Morche ◽

N. Goldscheider

Keyword(s):

Tracer Tests ◽

Low Flow ◽

Flow Conditions ◽

Flow Measurements ◽

Aquifer System ◽

Alpine Regions ◽

Lag Times ◽

Alpine Catchments ◽

Underground Flow ◽

Flood Attenuation

Abstract. The frequency and intensity of extreme hydrological events in alpine regions is projected to increase with climate change. The goal of this study was to better understand the functioning of aquifers composed of complex alluvial and rockfall deposits in alpine valleys and to quantify the role of these natural storage spaces in flood attenuation and baseflow maintenance. Geomorphological and hydrogeological mapping, tracer tests, and continuous flow measurements were conducted in the Reintal valley (German Alps), where runoff from a karst spring infiltrates into a series of postglacial alluvial/rockfall aquifers. During high-flow conditions, groundwater velocities of 30 m h−1 were determined along 500 m; hydrograph analyses revealed short lag times (5 h) between discharge peaks upstream and downstream from the aquifer series; the maximum discharge ratio downstream (22) and the peak recession coefficient (0.196 d−1) are low compared with other alpine catchments. During low-flow conditions, the underground flow path length increased to 2 km and groundwater velocities decreased to 13 m h−1. Downstream hydrographs revealed a delayed discharge response after 101 h and peaks dampened by a factor of 1.5. These results indicate that alluvial/rockfall aquifers might play an important role in the flow regime and attenuation of floods in alpine regions.

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Hydrogeology of an Alpine rockfall aquifer system and its role in flood attenuation and maintaining baseflow

Hydrology and Earth System Sciences ◽

10.5194/hess-18-4437-2014 ◽

2014 ◽

Vol 18 (11) ◽

pp. 4437-4452 ◽

Cited By ~ 12

Author(s):

U. Lauber ◽

P. Kotyla ◽

D. Morche ◽

N. Goldscheider

Keyword(s):

Tracer Tests ◽

Low Flow ◽

Flow Conditions ◽

Flow Measurements ◽

Aquifer System ◽

Alpine Regions ◽

Lag Times ◽

Alpine Catchments ◽

Underground Flow ◽

Flood Attenuation

Abstract. The frequency and intensity of extreme hydrological events in Alpine regions is projected to increase with climate change. The goal of this study is to better understand the functioning of aquifers composed of complex alluvial and rockfall deposits in Alpine valleys and to quantify the role of these natural storage spaces in flood attenuation and baseflow maintenance. Geomorphological and hydrogeological mapping, tracer tests, and continuous flow measurements were conducted in the Reintal (German Alps), where runoff from a karst spring infiltrates a series of postglacial alluvial/rockfall aquifers. During high-flow conditions, groundwater velocities of 30 m h−1 were determined along 500 m; hydrograph analyses revealed short lag times (5 h) between discharge peaks upstream and downstream from the aquifer series; the maximum discharge ratio downstream (22) and the peak recession coefficient (0.196 d−1) are low compared with other Alpine catchments. During low-flow conditions, the underground flow path length increased to 2 km and groundwater velocities decreased to 13 m h−1. Downstream hydrographs revealed a delayed discharge response after 101 h and peaks damped by a factor of 1.5. These results indicate that alluvial/rockfall aquifers might play an important role in the flow regime and attenuation of floods in Alpine regions.

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An LDV Study of the Influence of the Radiator on a Cooling Module Fan

Volume 1: Fora, Parts A and B ◽

10.1115/fedsm2002-31426 ◽

2002 ◽

Author(s):

Robert J. Martinuzzi ◽

Gregory A. Kopp ◽

Brian Havel

Keyword(s):

Laser Doppler Velocimetry ◽

Reverse Flow ◽

Low Flow ◽

Doppler Velocimetry ◽

Flow Conditions ◽

Flow Rates ◽

Cooling Fan ◽

Outlet Flow ◽

Flow Through ◽

Cooling Module

The influence of the radiator on the flow through an automotive cooling fan module was investigated using Laser Doppler Velocimetry for three different flow conditions. It is found that at the nominal design point, the radiator acts as an effective flow straightener. At low flow rates, fan induced pre-swirl is significant, but the radiator helps reduce reverse flow through the fan. Under ram air conditions the upstream inlet distortions persist through the module resulting in a highly distorted outlet flow.

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Wet subglacial bedforms of the NE Greenland Ice Stream shear margins

Annals of Glaciology ◽

10.1017/aog.2019.43 ◽

2019 ◽

Vol 60 (80) ◽

pp. 91-99 ◽

Cited By ~ 2

Author(s):

Kiya L. Riverman ◽

Sridhar Anandakrishnan ◽

Richard B. Alley ◽

Nicholas Holschuh ◽

Christine F. Dow ◽

...

Keyword(s):

Ground Penetrating Radar ◽

Acoustic Impedance ◽

Impedance Analysis ◽

Flow Conditions ◽

Lateral Shear ◽

Ice Flow ◽

Ice Stream ◽

Water Saturated ◽

Ground Penetrating

AbstractWe describe elongate, wet, subglacial bedforms in the shear margins of the NE Greenland Ice Stream and place some constraints on their formation. Lateral shear margin moraines have been observed across the previously glaciated landscape, but little is known about the ice-flow conditions necessary to form these bedforms. Here we describe in situ sediment bedforms under the NE Greenland Ice Stream shear margins that are observed in active-source seismic and ground-penetrating radar surveys. We find bedforms in the shear margins that are ~500 m wide, ~50 m tall, and elongated nearly parallel to ice-flow, including what we believe to be the first subglacial observation of a shear margin moraine. Acoustic impedance analysis of the bedforms shows that they are composed of unconsolidated, deformable, water-saturated till. We use these geophysical observations to place constraints on the possible formation mechanism of these subglacial features.

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Time-lapse ground penetrating radar difference reflection imaging of saline tracer flow in fractured rock

Geophysics ◽

10.1190/geo2019-0481.1 ◽

2020 ◽

Vol 85 (3) ◽

pp. H25-H37 ◽

Cited By ~ 2

Author(s):

Peter-Lasse Giertzuch ◽

Joseph Doetsch ◽

Mohammadreza Jalali ◽

Alexis Shakas ◽

Cédric Schmelzbach ◽

...

Keyword(s):

Ground Penetrating Radar ◽

Fractured Rock ◽

Sampling Rate ◽

Time Lapse ◽

Transport Processes ◽

Local Data ◽

Tracer Injection ◽

Flow Through ◽

Reflection Imaging ◽

Ground Penetrating

The characterization of flow and transport processes in fractured rock is challenging because they cannot be observed directly and hydrologic tests can only provide sparse and local data. Time-lapse ground penetrating radar (GPR) can be a valuable tool to monitor such processes in the subsurface, but it requires highly reproducible data. As part of a tracer injection experiment at the Grimsel Test Site (GTS) in Switzerland, borehole reflection GPR data were acquired in a time-lapse survey to monitor saline tracer flow through a fracture network in crystalline rock. Because the reflections from the tracer in the sub-mm fractures appear extremely weak, a differencing approach has been necessary to identify the tracer signal. Furthermore, several processing steps and corrections had to be applied to meet the reproducibility requirements. These steps include (1) single-trace preprocessing, (2) temporal trace alignment, (3) correction of sampling rate fluctuations, (4) spatial trace alignment, (5) spike removal, and (6) postprocessing procedures applied to the difference images. This allowed successful tracer propagation monitoring with a clear signal that revealed two separate tracer flow paths. The GPR results are confirmed by conductivity meters that were placed in boreholes in the GTS. If sufficient data processing is applied, GPR is shown to be capable of resolving tracer flow through sub-mm aperture fractures by difference reflection imaging even in challenging surroundings where many reflectors are present.

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Modelling of Kealey Ice Rise, Antarctica, reveals stable ice-flow conditions in East Ellsworth Land over millennia

Journal of Glaciology ◽

10.3189/2014jog13j089 ◽

2014 ◽

Vol 60 (219) ◽

pp. 139-146 ◽

Cited By ~ 14

Author(s):

Carlos Martín ◽

G. Hilmar Gudmundsson ◽

Edward C. King

Keyword(s):

Ground Penetrating Radar ◽

Stationary Flow ◽

Radar Data ◽

Flow Conditions ◽

West Antarctica ◽

Land Area ◽

Ice Flow ◽

Local Conditions ◽

Flow Solver ◽

Ground Penetrating

AbstractFlow at ice divides, their shape, size and internal structure depend not only on local conditions, but also on the flow regimes and past histories of the surrounding ice masses. Here we use field data from Kealey Ice Rise, Ellsworth Land, West Antarctica, in combination with flow modelling to investigate any possible signs of transients in the flow of the surrounding ice masses. Kealey Ice Rise shows linear surface features running parallel to its ridge in satellite imagery and a conspicuous layering in the ground-penetrating radar data known as double-peaked Raymond bumps. Through numerical modelling, by using an anisotropic full-Stokes thermomechanical flow solver, we analyse the evolution of Kealey Ice Rise and the timescales involved. We conclude that the features observed in the stratigraphy of Kealey Ice Rise require at least 3 ka of near-stationary flow conditions. However, we cannot exclude the possibility of a recent flow reorganization in the last century. We stress that the signs of stationary flow in radar stratigraphy observed in Kealey Ice Rise have been observed in other ice divides in the East Ellsworth Land area, suggesting stationary flow conditions over a millennial timescale in the region.

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Evaluating the potential of a novel dual heat-pulse sensor to measure volumetric water use in grapevines under a range of flow conditions

Functional Plant Biology ◽

10.1071/fp13156 ◽

2014 ◽

Vol 41 (8) ◽

pp. 874 ◽

Cited By ~ 13

Author(s):

Kyle R. Pearsall ◽

Larry E. Williams ◽

Sean Castorani ◽

Tim M. Bleby ◽

Andrew J. McElrone

Keyword(s):

Water Use ◽

Sap Flow ◽

Heat Pulse ◽

Low Flow ◽

Ratio Method ◽

Flow Conditions ◽

Thompson Seedless ◽

Flow Measurements ◽

Highly Correlated ◽

Weighing Lysimeter

The aim of this study was to validate a novel, dual sap-flow sensor that combines two heat-pulse techniques in a single set of sensor probes to measure volumetric water use over the full range of sap flows found in grapevines. The heat ratio method (HRM), which works well at measuring low and reverse flows, was combined with the compensation heat-pulse method (CHPM) that captures moderate to high flows. Sap-flow measurements were performed on Vitis vinifera L. (cvv. Thompson seedless, Chardonnay and Cabernet Sauvignon) grapevines growing in a greenhouse and in three different vineyards, one of which contained a field weighing lysimeter. The combined heat-pulse techniques closely tracked diurnal grapevine water use determined through lysimetry in two growing seasons, and this was true even at very high flow rates (>6 L vine–1 h–1 for Thompson seedless vines in the weighing lysimeter). Measurements made with the HRM technique under low flow conditions were highly correlated (R2 ~ 0.90) with those calculated using the compensated average gradient method that is used to resolve low flow with the CHPM method. Volumetric water use determined with the dual heat-pulse sensors was highly correlated with hourly lysimeter water use in both years (R2 = 0.92 and 0.94 in 2008 and 2009 respectively), but the nature of the relationship was inconsistent among replicate sensors. Similar results were obtained when comparing grapevine water use determined from sap-flow sensors to miniaturised weighing lysimetry of 2-year-old potted vines and to meteorological estimates for field-grown vines in two additional vineyards. The robust nature of all of the correlations demonstrates that the dual heat-pulse sensors can be used to effectively track relative changes in plant water use, but variability of flow around stems makes it difficult to accurately convert to sap-flow volumes.

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