Reactions of a calving glacier to large changes in water level

Annals of Glaciology ◽

10.3189/1992aog16-1-158-162 ◽

1992 ◽

Vol 16 ◽

pp. 158-162 ◽

Cited By ~ 1

Author(s):

Tron Laumann ◽

Bjørn Wold

Keyword(s):

Water Level ◽

Lake Level ◽

Surface Velocity ◽

Hydropower Development ◽

Outlet Glacier ◽

Glacier Terminus ◽

Western Norway ◽

Measured Response ◽

Good Agreement

Austdalsvatn in western Norway was regulated in 1988 as a reservoir for a hydropower development. From a pre-1988 water level of 1157 m a.s.l. the new water level will vary more or less annually from 1170 to 1200 m a.s.l. The outlet glacier Austdalsbreen calves into this reservoir. About 1600 m up-valley from its terminus the glacier flows over a bedrock riegel that is, at its lowest point, ∼ 15 m above the projected maximum lake level of 1200 m. As a result of the increase in water level, the surface velocity near the front has increased from about 0.07 to 0.13 m d−1.Calculations suggest that the glacier terminus will retreat about 750 m in 50 years. The measured response of the glacier terminus for the first three years is in good agreement with the simulations.

Observation of recent surges of Vatnajökull, Iceland, by means of ERS SAR interferometry

Annals of Glaciology ◽

10.3189/172756403781815546 ◽

2003 ◽

Vol 37 ◽

pp. 69-76 ◽

Cited By ~ 16

Author(s):

Andrea Fischer ◽

Helmut Rott ◽

Helgi Björnsson

Keyword(s):

Sar Interferometry ◽

Surface Velocity ◽

Outlet Glacier ◽

Ice Cap ◽

Glacier Terminus ◽

New Information ◽

Basal Sliding ◽

Velocity Changes ◽

Extended Area ◽

In The Beginning

AbstractRecent surges of two outlet glaciers of the Vatnajökull ice cap, Iceland, were observed using European Remote-sensing Satellite (ERS) synthetic aperture radar (SAR) tandem interferograms from12 different dates between December 1995 and January 2000. ERS SAR interferometry provided new information on the temporal and spatial variations in surface velocity during surges, after fieldwork became impossible. The area affected by the surge and therefore by increased basal sliding was delineated. Themigration of flow divides on the ice cap during a surge was described. At Sylgjujökull, a western outlet glacier covering an area of 175 km2, the fully developed surge and its abating phase were studied. Over a period of 4 2 years after December 1995, the ice motion decreased steadily, with initially the highest velocities and subsequently the most pronounced decrease in velocity at the glacier terminus. The surge of Dyngjujökull, a northern outlet glacier covering an area of 1040 km2, reached its maximum in 1999/2000. Slow acceleration over an area of about 200 km2 was first observed between March 1996 and January 1997. The interferogram from January 1999 shows a well-developed surge area, covering 210 km2. This area more than doubled by January 2000, with maximum velocities reaching >7 md–1. Between January 1997 and January 2000, the flow divide between Dyngju- and Skeiðararjökull shifted 16 km to the south. The investigations indicate that a surge cycle on these glaciers spans several years, with slowly increasing motion over an extended area in the beginning, and more pronounced velocity changes during the active surge phase lasting 1–2 years.

Response of glacier flow and structure to proglacial lake development and climate at Fjallsjökull, south-east Iceland

Journal of Glaciology ◽

10.1017/jog.2019.18 ◽

2019 ◽

Vol 65 (250) ◽

pp. 321-336 ◽

Cited By ~ 4

Author(s):

REBECCA DELL ◽

RACHEL CARR ◽

EMRYS PHILLIPS ◽

ANDREW J. RUSSELL

Keyword(s):

Satellite Imagery ◽

Surface Velocity ◽

Outlet Glacier ◽

Lake Development ◽

Glacier Terminus ◽

Air Temperatures ◽

Glacier Dynamics ◽

Proglacial Lake ◽

Glacier Flow ◽

Structural Architecture

ABSTRACTOver recent decades, the number of outlet glaciers terminating in lakes in Iceland has increased in line with climate warming. The mass-balance changes of these lake-terminating outlet glaciers are sensitive to rising air temperatures, due to altered glacier dynamics and increased surface melt. This study aims to better understand the relationship between proglacial lake development, climate, glacier dynamics and glacier structure at Fjallsjökull, a large, lake-terminating outlet glacier in south-east Iceland. We used satellite imagery to map glacier terminus position and lake extent between 1973 and 2016, and a combination of aerial and satellite imagery to map the structural architecture of the glacier's terminus in 1982, 1994 and 2011. The temporal evolution of ice surface velocities between 1990 and 2018 was calculated using feature tracking. Statistically significant increases in the rate of terminus retreat and lake expansion were identified in 2001, 2009 and 2011. Our surface velocity and structural datasets revealed the development of localised flow ‘corridors’ over time, which conveyed relatively faster flow towards the glacier's terminus. We attribute the overall changes in dynamics and structural architecture at Fjallsjökull to rising air temperatures, but argue that the spatial complexities are driven by glacier specific factors, such as basal topography.

In-stream uptake and retention of C, N and P in a supraglacial stream

Annals of Glaciology ◽

10.3189/172756411795932065 ◽

2010 ◽

Vol 51 (56) ◽

pp. 80-86 ◽

Cited By ~ 11

Author(s):

Durelle Scott ◽

Eran Hood ◽

Michael Nassry

Keyword(s):

Nutrient Retention ◽

Flow Paths ◽

Lower Velocity ◽

Outlet Glacier ◽

Glacier Terminus ◽

Order Of Magnitude ◽

Bedload Sediment ◽

Nutrient Injection ◽

Carbon Processing ◽

Ice Water

AbstractSupraglacial streams form annually during the melt season, transporting dissolved solutes from the melting ice and snowpack to subglacial flow paths and the glacier terminus. Although nutrient and carbon processing has been documented in other supraglacial environments (cryoconite holes, snowpack), little work has examined the potential for in-stream nutrient retention in supraglacial streams. Here we carried out a solute nutrient injection experiment to quantify NH3+, PO43−and labile dissolved organic carbon (DOC) retention in a supraglacial stream. The experiment was performed on a 100 m stream reach on Mendenhall Glacier, an outlet glacier on the Juneau Icefield, southeastern Alaska, USA. The study stream contained two distinct reaches of equal length. The first reach had a lower velocity (0.04 ms−1) and contained abundant gravel sediment lining the ice–water interface, while the second reach was devoid of bedload sediment and had an order-of-magnitude higher velocity. At the end of the second reach, the stream emptied into a moulin, which is typical of supraglacial streams on this and other temperate glaciers. We found that N and P were transported largely conservatively, although NO3−increased along the reach, suggestive of nitrification. Labile DOC was retained slightly within the stream, although rates were low relative to the travel times observed within the supraglacial stream. Although our findings show that these streams have low processing rates, measurable in-stream nitrification and dissolved organic matter uptake within this biologically unfavorable environment suggests that supraglacial streams with longer residence times and abundant fine substrate have the potential to modify and retain nutrients during transport to the glacier terminus.

Quantifying recent lake level changes in Patagonia (Argentina and Chile): Back to the future?

10.5194/egusphere-egu21-8467 ◽

2021 ◽

Author(s):

Daniel Ariztegui ◽

Clément Pollier ◽

Andrés Bilmes

Keyword(s):

Water Level ◽

Lake Level ◽

Satellite Images ◽

Meteorological Data ◽

Tierra Del Fuego ◽

Water Level Fluctuations ◽

Lake Levels ◽

The Past ◽

Rainfall Variations ◽

The Impact

Lake levels in hydrologically closed-basins are very sensitive to climatically and/or anthropogenically triggered environmental changes. Their record through time can provide valuable information to forecast changes that can have substantial economical and societal impact.Increasing precipitation in eastern Patagonia (Argentina) have been documented following years with strong El Ni&#241;o (cold) events using historical and meteorological data. Quantifying changes in modern lake levels allow determining the impact of rainfall variations while contributing to anticipate the evolution of lacustrine systems over the next decades with expected fluctuations in ENSO frequencies. Laguna Carrilaufquen Grande is located in the intermontane Maquinchao Basin, Argentina. Its dimension fluctuates greatly, from 20 to 55 km2 water surface area and an average water depth of 3 m. Several well-preserved gravelly beach ridges witness rainfall variations that can be compared to meteorological data and satellite images covering the last ~50 years. Our results show that in 2016 lake level was the lowest of the past 44 years whereas the maximum lake level was recorded in 1985 (+11.8 m above the current lake level) in a position 1.6 km to the east of the present shoreline. A five-years moving average rainfall record of the area was calculated smoothing the extreme annual events and correlated to the determined lake level fluctuations. The annual variation of lake levels was up to 1.2 m (e.g. 2014) whereas decadal variations related to humid-arid periods for the interval 2002 to 2016 were up to 9.4 m. These data are consistent with those from other monitored lakes and, thus, our approach opens up new perspectives to understand the historical water level fluctuations of lakes with non-available monitoring data.&#160;Laguna de los Cisnes in the Chilean section of the island of Tierra del Fuego, is a closed-lake presently divided into two sections of 2.2 and 11.9 km2, respectively. These two water bodies were united in the past forming a single larger lake. The lake level was&#160; ca. 4 m higher than today as shown by clear shorelines and the outcropping of large Ca-rich microbialites. Historical data, aerial photographs and satellite images indicate that the most recent changes in lake level are the result of a massive decrease of water input during the last half of the 20th century triggered by an indiscriminate use of the incoming water for agricultural purposes. The spectacular outcropping of living and fossil microbialites is not only interesting from a scientific point of view but has also initiated the development of the site as a local touristic attraction. However, if the use of the incoming water for agriculture in the catchment remains unregulated the lake water level might drop dangerously and eventually the lake might fully desiccate.These two examples illustrate how recent changes in lake level can be used to anticipate the near future of lakes. They show that ongoing climate changes along with the growing demand of natural resources have already started to impact lacustrine systems and this is likely to increase in the decades to come.

Simplified Lake Surface Area Method for the Minimum Ecological Water Level of Lakes and Wetlands

Water ◽

10.3390/w10081056 ◽

2018 ◽

Vol 10 (8) ◽

pp. 1056 ◽

Cited By ~ 6

Author(s):

Songpu Shang ◽

Songhao Shang

Keyword(s):

Water Level ◽

Surface Area ◽

Lake Level ◽

Lake Ecosystem ◽

Lake Surface ◽

Area Method ◽

Ecosystem Protection ◽

Lake Morphology ◽

Lake Surface Area ◽

Ecological Water Level

The determination of the rational minimum ecological water level is the base for the protection of ecosystems in shrinking lakes and wetlands. Based on the lake surface area method, a simplified lake surface area method was proposed to define the minimum ecological lake level from the lake level-logarithm of the surface area curve. The curve slope at the minimum ecological lake level is the ratio of the maximum lake storage to the maximum surface area. For most practical cases when the curve cannot be expressed as a simple analytical function, the minimum ecological lake level can be determined numerically using the weighted sum method for an equivalent multi-objective optimization model that balances ecosystem protection and water use. This method requires fewer data of lake morphology and is simple to compute. Therefore, it is more convenient to use this method in the assessment of the ecological lake level. The proposed method was used to determine the minimum ecological water level for one freshwater lake, one saltwater lake, and one wetland in China. The results can be used in the lake ecosystem protection planning and the rational use of water resources in the lake or wetland basins.

The propagation of a surge front on Bering Glacier, Alaska, 2001–2011

Annals of Glaciology ◽

10.3189/2013aog63a341 ◽

2013 ◽

Vol 54 (63) ◽

pp. 221-228 ◽

Cited By ~ 13

Author(s):

James Turrin ◽

Richard R. Forster ◽

Chris Larsen ◽

Jeanne Sauber

Keyword(s):

Feature Tracking ◽

Average Rate ◽

Surface Velocity ◽

Ablation Zone ◽

Ice Surface ◽

Glacier Terminus ◽

Bering Glacier ◽

Landsat 7 ◽

Ice Velocity ◽

Recent Activity

AbstractBering Glacier, Alaska, USA, has a ∼20 year surge cycle, with its most recent surge reaching the terminus in 2011. To study this most recent activity a time series of ice velocity maps was produced by applying optical feature-tracking methods to Landsat-7 ETM+ imagery spanning 2001-11. The velocity maps show a yearly increase in ice surface velocity associated with the down-glacier movement of a surge front. In 2008/09 the maximum ice surface velocity was 1.5 ±0.017 km a-1 in the mid-ablation zone, which decreased to 1.2 ±0.015 km a-1 in 2009/10 in the lower ablation zone, and then increased to nearly 4.4 ± 0.03 km a-1 in summer 2011 when the surge front reached the glacier terminus. The surge front propagated down-glacier as a kinematic wave at an average rate of 4.4 ±2.0 km a-1 between September 2002 and April 2009, then accelerated to 13.9 ± 2.0 km a-1 as it entered the piedmont lobe between April 2009 and September 2010. The wave seems to have initiated near the confluence of Bering Glacier and Bagley Ice Valley as early as 2001, and the surge was triggered in 2008 further down-glacier in the mid-ablation zone after the wave passed an ice reservoir area.

TermPicks: A century of Greenland glacier terminus data for use in machine learning applications

10.5194/tc-2021-311 ◽

2021 ◽

Author(s):

Sophie Goliber ◽

Taryn Black ◽

Ginny Catania ◽

James M. Lea ◽

Helene Olsen ◽

...

Keyword(s):

Machine Learning ◽

Greenland Ice Sheet ◽

Median Number ◽

Google Earth ◽

Training Data ◽

Machine Learning Techniques ◽

Data Set ◽

Outlet Glacier ◽

Glacier Terminus ◽

Median Error

Abstract. Marine-terminating outlet glacier terminus traces, mapped from satellite and aerial imagery, have been used extensively in understanding how outlet glaciers adjust to climate change variability over a range of time scales. Numerous studies have digitized termini manually, but this process is labor-intensive, and no consistent approach exists. A lack of coordination leads to duplication of efforts, particularly for Greenland, which is a major scientific research focus. At the same time, machine learning techniques are rapidly making progress in their ability to automate accurate extraction of glacier termini, with promising developments across a number of optical and SAR satellite sensors. These techniques rely on high quality, manually digitized terminus traces to be used as training data for robust automatic traces. Here we present a database of manually digitized terminus traces for machine learning and scientific applications. These data have been collected, cleaned, assigned with appropriate metadata including image scenes, and compiled so they can be easily accessed by scientists. The TermPicks data set includes 39,060 individual terminus traces for 278 glaciers with a mean and median number of traces per glacier of 136 ± 190 and 93, respectively. Across all glaciers, 32,567 dates have been picked, of which 4,467 have traces from more than one author (duplication of 14 %). We find a median error of ∼100 m among manually-traced termini. Most traces are obtained after 1999, when Landsat 7 was launched. We also provide an overview of an updated version of The Google Earth Engine Digitization Tool (GEEDiT), which has been developed specifically for future manual picking of the Greenland Ice Sheet.

Spending Less Than 100$ on Real-Time Sewer Flow Measurements

10.5194/egusphere-egu21-15635 ◽

2021 ◽

Author(s):

Robert Meier ◽

Franz Tscheikner-Gratl ◽

Christos Makropoulos

Keyword(s):

Water Level ◽

Industrial Revolution ◽

New Technologies ◽

Surface Velocity ◽

Prediction Algorithm ◽

Raspberry Pi ◽

Laboratory Setting ◽

Flow Sensors ◽

Flow Measurements

As more and more computational power becomes available at increasingly affordable prices, the last years have seen a veritable explosion in the number of sensors and interconnected devices. This evolution is well known and often referred to as the 4th industrial revolution, or the IoT. The water sector, albeit often conservative in adopting new technologies, will profit from this continued digitalisation in various ways.In this work we focus on the vision of covering entire sewer systems by tightly knit sensor networks which can process the generated amount of data simultaneously. Given the large number of sensors required, the only possibility to implement such a network is keeping costs as low as possible for the individual devices or use already existing sensors in multiple ways (e.g., traffic cameras helping in flood detection).Using hardware of the Raspberry Pi ecosystem, currently retailing at less than 100$, we collected continuous video footage of an artificial open channel in a laboratory setting and used a deep neural network to extract the water level and surface velocity. The measurement accuracy of the prediction algorithm was then compared to conventional flow sensors to assess the practicality of this approach. Preliminary results in a laboratory setting indicate a sufficient prediction accuracy of the water level for engineering uses but further work is needed to verify this in a long-term field study.After this initial stage, deploying the sensor in a real-world setting as part of the B-WaterSmart project is planned. Apart from verifying the results under real conditions, we will then be able to assess the long-term behaviour of this approach. This includes an evaluation of the maintenance effort. As the sensor is not in direct contact with the sewage, the typical need for frequent cleaning should be greatly reduced, which in turn is expected to further lower the costs.We argue that if such a cheap sensor can ultimately be established as a viable alternative to more conventional flow sensors, the vision of sewer networks covered entirely by sensors, could become more attainable in practice.

Estimation of hydraulic properties of subglacial till from ploughmeter measurements

Journal of Glaciology ◽

10.1017/s0022143000002033 ◽

1998 ◽

Vol 44 (148) ◽

pp. 517-522 ◽

Cited By ~ 18

Author(s):

Urs H. Fischer ◽

Neal R. Iverson ◽

Brian Hanson ◽

Roger LeB. Hooke ◽

Peter Jansson

Keyword(s):

Water Level ◽

Hydraulic Properties ◽

Water Pressure ◽

Inverse Correlation ◽

Borehole Water ◽

Potential Gradients ◽

Glacial Tills ◽

Basal Till ◽

Range Of Values ◽

Good Agreement

Abstract Force variations on a "ploughmeter" and fluctuations in subglacial water pressure have been measured in the same borehole at Storglaciaren, Sweden, to investigate hydraulic properties of the basal till layer. A strong inverse correlation of the pressure and force records, in conjunction with a significant lime lag between the two signals, suggests that pore-water pressures directly affect the strength of the till. Variations in sub-glacial water pressure result in potential gradients across the water till interlace at the bottom of the borehole that drive pressure waves downwards through the till layer when the borehole water level is high and back upwards when the water level is low. Analysis of the propagation velocity of this pressure wave indicates that the hydraulic diffusivity of Storglaciaren till is in the range 1.9−3.6 x 10−6m2s−1,in good agreement with estimates obtained in the laboratory. Hydraulic conductivity values associated with these difrusivities are between 10−9 and 10−8ms−1 and thus are well within the range of values for other glacial tills.