scholarly journals Post-jökulhlaup geomorphic evolution of the Gígjökull Basin, Iceland

2019 ◽  
Vol 60 (80) ◽  
pp. 127-137 ◽  
Author(s):  
D. Harrison ◽  
N. Ross ◽  
A. J. Russell ◽  
S. A. Dunning
Keyword(s):  
Physical Properties ◽  
Satellite Image ◽  
Surface Elevation ◽  
Geomorphic Evolution ◽  
Rapid Melting ◽  
Outburst Floods ◽  
Glacier Ice ◽  
Ground Based Lidar ◽  
Geomorphic Processes ◽  
Gps Observations

AbstractHow landscapes respond to, and evolve from, large jökulhlaups (glacial outburst floods) is poorly constrained due to limited observations and detailed monitoring. We investigate how melt of glacier ice transported and deposited by multiple jökulhlaups during the 2010 eruption of Eyjafjallajökull, Iceland, modified the volume and surface elevation of jökulhlaup deposits. Jökulhlaups generated by the eruption deposited large volumes of sediment and ice, causing significant geomorphic change in the Gígjökull proglacial basin over a 4-week period. Observation of these events enabled robust constraints on the physical properties of the floods which informs our understanding of the deposits. Using ground-based LiDAR, GPS observations and the satellite-image-derived ArcticDEMs, we quantify the post-depositional response of the 60 m-thick Gígjökull sediment package to the meltout of buried ice and other geomorphic processes. Between 2010 and 2016, total deposit volume reduced by −0.95 × 106 m3 a−1, with significant surface lowering of up to 1.88 m a−1. Surface lowering and volumetric loss of the deposits is attributed to three factors: (i) meltout of ice deposited by the jökulhlaups; (ii) rapid melting of the buried Gígjökull glacier snout; and (iii) incision of the proglacial meltwater system into the jökulhlaup deposits.

scholarly journals A History of Jökulhlaups from Strandline Lake, Alaska, U.S.A.

1985 ◽  
Vol 31 (109) ◽  
pp. 272-280 ◽  
Author(s):  
Matthew Sturm ◽  
Carl S. Benson
Keyword(s):  
North America ◽  
Release Mechanism ◽  
Contour Maps ◽  
Outburst Floods ◽  
Before And After ◽  
Glacier Ice ◽  
History Of ◽  
Subglacial Drainage

AbstractJökulhlaups, also known as outburst floods, have occurred every 1 to 5 years from Strandline Lake, one of the largest glacier-dammed lakes in North America. The development of a distinct calving embayment in the lobe of Triumvirate Glacier which dams the lake, as well as the filling of a number of supraglacier pools, appear to be reliable precursors to a jökulhlaup. Analysis of contour maps made from photographs taken immediately before and after the jökulhlaup of 17 September 1982 indicate that over 95% of the lake drains, a volume of approximately 7 × 108 m3 of water. The glacier lobe which dams the lake fractures and subsides during a jökulhlaup, indicating that the release mechanism is hydrostatic lifting of the ice off of a sub-glacial spillway. Evidence from the ice-free margins of the glacier suggests that the spillway may be controlled by bedrock. Large variation in the refilling period of Strandline Lake indicates that the subglacial drainage tunnels can remain open for as much as a few years after a jökulhlaup, before they become sealed by sediments and/or glacier ice.

scholarly journals A History of Jökulhlaups from Strandline Lake, Alaska, U.S.A.

1985 ◽  
Vol 31 (109) ◽  
pp. 272-280 ◽  
Author(s):  
Matthew Sturm ◽  
Carl S. Benson
Keyword(s):  
North America ◽  
Release Mechanism ◽  
Contour Maps ◽  
Outburst Floods ◽  
Before And After ◽  
Glacier Ice ◽  
History Of ◽  
Subglacial Drainage

AbstractJökulhlaups, also known as outburst floods, have occurred every 1 to 5 years from Strandline Lake, one of the largest glacier-dammed lakes in North America. The development of a distinct calving embayment in the lobe of Triumvirate Glacier which dams the lake, as well as the filling of a number of supraglacier pools, appear to be reliable precursors to a jökulhlaup. Analysis of contour maps made from photographs taken immediately before and after the jökulhlaup of 17 September 1982 indicate that over 95% of the lake drains, a volume of approximately 7 × 108m3of water. The glacier lobe which dams the lake fractures and subsides during a jökulhlaup, indicating that the release mechanism is hydrostatic lifting of the ice off of a sub-glacial spillway. Evidence from the ice-free margins of the glacier suggests that the spillway may be controlled by bedrock. Large variation in the refilling period of Strandline Lake indicates that the subglacial drainage tunnels can remain open for as much as a few years after a jökulhlaup, before they become sealed by sediments and/or glacier ice.

Integrating and assessing Arctic glacier thickness data into Glacier Thickness Database (GlaThiDa) Version 3.0

2020 ◽  
Author(s):  
Ethan Welty ◽  
Francisco Navarro ◽  
Johannes Fürst ◽  
Isabelle Gärtner-Roer ◽  
Kathrin Naegeli ◽  
...  
Keyword(s):  
International Association ◽  
Surface Elevation ◽  
Survey Method ◽  
Ice Thickness ◽  
Unique Identifier ◽  
Related Information ◽  
Glacier Ice ◽  
Spatial Coordinates ◽  
Data Tables ◽  
Volume Estimates

<p>GlaThiDa is an internationally collected, standardized dataset of glacier thickness from in-situ and remotely sensed observations, based on data submissions, literature review, and airborne data from NASA's Operation IceBridge. GlaThiDa is a contribution to the working group on ‘glacier ice thickness estimation’ formed under the auspices of the International Association of Cryospheric Sciences (IACS). The database is hosted by the World Glacier Monitoring Service (WGMS). GlaThiDa is structured in three data tables of different levels of detail, which are linked together by a unique identifier for each glacier survey. The first table (T) is the overview table containing information on the location and area of the surveyed glacier, interpolated mean and maximum glacier-wide thickness and their reported uncertainties, the survey method and related information, as well as investigator names and source of the data. The second table (TT) includes mean and maximum ice thickness interpolated over surface elevation bands. The third table (TTT) contains the original point measurements, including spatial coordinates, surface elevation, and ice thickness. GlaThiDa was first released in 2014 (version 1.0) and first updated in 2016 (version 2.1). Version 3.0 was released in 2019. In addition to several technical improvements, nearly 3 600 ice-thickness surveys have been added, for a total of 5 181. Most of the new data are for Arctic glaciers, and some of these were collected for the H2020 INTAROS project. Moreover, GlaThiDa was assessed as a core component of the existing Arctic observing system in INTAROS Work Package 2.1 (an assessment of existing Arctic observational capacity and remaining gaps with respect to stakeholders needs). GlaThiDa has great potential as a reference dataset for calibrating and validating regional and global glacier volume estimates.</p>

scholarly journals Contrails to Cirrus—Morphology, Microphysics, and Radiative Properties

2006 ◽  
Vol 45 (1) ◽  
pp. 5-19 ◽  
Author(s):  
David Atlas ◽  
Zhien Wang ◽  
David P. Duda
Keyword(s):  
Satellite Image ◽  
Radiative Properties ◽  
Time Of Arrival ◽  
Regional Warming ◽  
Optical Extinction ◽  
Essentially Normal ◽  
Minimum Age ◽  
Ground Based Lidar ◽  
Time Of Travel ◽  
Ice Water

Abstract This work is two pronged, discussing 1) the morphology of contrails and their transition to cirrus uncinus, and 2) their microphysical and radiative properties. It is based upon the fortuitous occurrence of an unusual set of essentially parallel contrails and the unanticipated availability of nearly simultaneous observations by photography, satellite, automated ground-based lidar, and a newly available database of aircraft flight tracks. The contrails, oriented from the northeast to southwest, are carried to the southeast with a component of the wind so that they are spread from the northwest to southeast. Convective turrets form along each contrail to form the cirrus uncinus with fallstreaks of ice crystals that are oriented essentially normal to the contrail length. Each contrail is observed sequentially by the lidar and tracked backward to the time and position of the originating aircraft track with the appropriate component of the wind. The correlation coefficient between predicted and actual time of arrival at the lidar is 0.99, so that one may identify both visually and satellite-observed contrails exactly. Contrails generated earlier in the westernmost flight corridor occasionally arrive simultaneously with those formed later closer to the lidar to produce broader cirrus fallstreaks and overlapping contrails on the satellite image. The minimum age of a contrail is >2 h and corresponds to the longest time of travel to the lidar. The lag between the initial formation of the contrail and its first detectability by Moderate-Resolution Imaging Spectroradiometer (MODIS) is ≈33 min, thus accounting for the distance between the aircraft track and the first detectable contrail by satellite. The lidar also provides particle fall speeds and estimated sizes, optical extinction coefficients, optical thickness (τ = 0.35), and ice water path (IWP = 8.1 g m−2). These values correspond to the lower range of those found for midlatitude cirrus by Heymsfield et al. The ice water per meter of length along the cloud lines is 103–104 times that released by typical jet aircraft. The synthesis of these findings with those of prior investigators provides confidence in the present results. Various authors find that contrail-generated cirrus such as reported here contribute to net regional warming.

scholarly journals Airborne and spaceborne DEM- and laser altimetry-derived surface elevation and volume changes of the Bering Glacier system, Alaska, USA, and Yukon, Canada, 1972–2006

2009 ◽  
Vol 55 (190) ◽  
pp. 316-326 ◽  
Author(s):  
Reginald R. Muskett ◽  
Craig S. Lingle ◽  
Jeanne M. Sauber ◽  
Austin S. Post ◽  
Wendell V. Tangborn ◽  
...  
Keyword(s):  
Surface Elevation ◽  
Laser Altimetry ◽  
Volume Changes ◽  
The North ◽  
Glacier System ◽  
Outburst Floods ◽  
Digital Elevation ◽  
Bering Glacier ◽  
Elevation Changes ◽  
Terra Modis

AbstractUsing airborne and spaceborne high-resolution digital elevation models and laser altimetry, we present estimates of interannual and multi-decadal surface elevation changes on the Bering Glacier system, Alaska, USA, and Yukon, Canada, from 1972 to 2006. We find: (1) the rate of lowering during 1972–95 was 0.9 ± 0.1 m a−1; (2) this rate accelerated to 3.0 ± 0.7 m a−1 during 1995–2000; and (3) during 2000–03 the lowering rate was 1.5 ± 0.4 m a−1. From 1972 to 2003, 70% of the area of the system experienced a volume loss of 191 ± 17 km3, which was an area-average surface elevation lowering of 1.7 ± 0.2 m a−1. From November 2004 to November 2006, surface elevations across Bering Glacier, from McIntosh Peak on the south to Waxell Ridge on the north, rose as much as 53 m. Up-glacier on Bagley Ice Valley about 10 km east of Juniper Island nunatak, surface elevations lowered as much as 28 m from October 2003 to October 2006. NASA Terra/MODIS observations from May to September 2006 indicated muddy outburst floods from the Bering terminus into Vitus Lake. This suggests basal–englacial hydrologic storage changes were a contributing factor in the surface elevation changes in the fall of 2006.

scholarly journals High-resolution inventory to capture glacier disintegration in the Austrian Silvretta

2021 ◽  
Author(s):  
Andrea Fischer ◽  
Bernd Seiser ◽  
Kay Helfricht ◽  
Martin Stocker-Waldhuber
Keyword(s):  
High Resolution ◽  
Spatial Resolution ◽  
Ice Age ◽  
Surface Elevation ◽  
Glacier Changes ◽  
Wide Range ◽  
Elevation Data ◽  
Glacier Ice ◽  
Geodetic Mass Balance

Abstract. Eastern Alpine glaciers have been receding since the LIA maximum, but the majority of glacier margins could be delineated unambiguously for the last Austrian glacier inventories. Even debris-covered termini, changes in slope, colour or the position of englacial streams enabled at least an in situ survey of glacier outlines. Today the outlines of totally debris-covered glacier ice are fuzzy and raise the theoretical discussion if these glaciogenic features are still glaciers and should be part of the respective inventory – or part of an inventory of transient cryogenic landforms. A new high-resolution glacier inventory (area and surface elevation) was compiled for the years 2017 and 2018 to quantify glacier changes for the Austrian Silvretta region in full. Glacier outlines were mapped manually, based on orthophotos and elevation models and patterns of volume change of 1 to 0.5 m spatial resolution. The vertical accuracy of the DEMs generated from 6 to 8 LiDAR points per m2 is in the order of centimetres. calculated in relation to the previous inventories dating from 2004/2006 (LiDAR), 2002, 1969 (photogrammetry) and to the Little Ice Age maximum extent (moraines). Between 2004/06 and 2017/2018, the 46 glaciers of the Austrian Silvretta lost −29 ± 4 % of their area and now cover 13.1 ± 0.4 km2. This is only 32 ± 2 % of their LIA extent of 40.9 ± 4.1 km2. The area change rate increased from −0.6 %/year (1969–2002) to −2.4 %/year (2004/06–2017/18). The annual geodetic mass balance showed a loss increasing from −0.2 ± 0.1 m w.e./year (1969–2002) to –0.8 m ±0.1 w.e./year (2004/06–2017/18) with an interim peak in 2002–2004/06 at −1.5 ± 0.7 m w.e./year. Identifying the glacier outlines offers a wide range of possible interpretations of former glaciers that have evolved into small and now totally debris-covered cryogenic geomorphological structures. Only the patterns and amounts of volume changes allow us to estimate the area of the buried glacier remnants. To keep track of the buried ice and its fate, and to distinguish increasing debris cover from ice loss, we recommend inventory repeat frequencies of three to five years and surface elevation data with a spatial resolution of one metre.

scholarly journals Investigation of a possible crevasse near the main airstrip on McMurdo Ice Shelf, Antarctica

1997 ◽  
Vol 24 ◽  
pp. 152-156 ◽  
Author(s):  
I. M. Whillans ◽  
C. J. Merry ◽  
G. S. Hamilton
Keyword(s):  
Global Positioning System ◽  
Sea Water ◽  
Satellite Image ◽  
Surface Expression ◽  
Surface Elevation ◽  
Positioning System ◽  
Ice Shelf ◽  
Dark Line ◽  
Global Positioning

A dark line appears on a recent satellite image of McMurdo Ice Shelf, Antarctica. It is parallel to the calving front. Initial thoughts were that the line marks an opening crevasse associated with an impending major calving event. The feature was studied by means of a strain and surface-elevation grid that was surveyed twice, 25 d apart, using global positioning system (GPS) techniques. Results show that the dark line is not due to an opening crevasse. The feature is probably the surface expression of firn collapse over sea water soaking horizontally into the ice shelf.

scholarly journals GLOFs in the WOS: bibliometrics, geographies and global trends of research on glacial lake outburst floods (Web of Science, 1979–2016)

2018 ◽  
Vol 18 (3) ◽  
pp. 813-827 ◽  
Author(s):  
Adam Emmer
Keyword(s):  
Web Of Science ◽  
Low Frequency ◽  
Glacial Lake ◽  
Global Trends ◽  
Research Activities ◽  
Lake Evolution ◽  
Outburst Floods ◽  
Glacial Lake Outburst Floods ◽  
Glacier Ice ◽  
Published Research

Abstract. Research on glacial lake outburst floods (GLOFs) – specific low-frequency, high-magnitude floods originating in glacial lakes, including jökulhlaups – is well justified in the context of glacier ice loss and glacial lake evolution in glacierized areas all over the world. Increasing GLOF research activities, which are documented by the increasing number of published research items, have been observed in the past few decades; however, comprehensive insight into the GLOF research community, its global bibliometrics, geographies and trends in research is missing. To fill this gap, a set of 892 GLOF research items published in the Web of Science database covering the period 1979–2016 was analysed. General bibliometric characteristics, citations and references were analysed, revealing a certain change in the publishing paradigm over time. Furthermore, the global geographies of research on GLOFs were studied, focusing on (i) where GLOFs are studied, (ii) who studies GLOFs, (iii) the export of research on GLOFs and (iv) international collaboration. The observed trends and links to the challenges ahead are discussed and placed in a broader context.

Glaciological Methods

Polar Record ◽  
1946 ◽  
Vol 4 (31) ◽  
pp. 315-319 ◽  
Author(s):  
W:son Ahlmann
Keyword(s):  
Physical Properties ◽  
Different Types ◽  
Glacier Ice ◽  
Transitional Forms

The study of glaciers may be divided into two branches: (1) the study of the physical properties of glacier ice, firn, and snow; (2) the investigation of the glacier's regime and its meteorological causes. The first branch comprises the thermal and crystallographic conditions of the ice, firn and snow of glaciers, and their transitional forms; also the plasticity, movement, erosion, etc. of glaciers. The second branch is concerned with quantitative determinations of accumulation, ablation and the total regime of glaciers, and with the meteorological causes affecting them. This second branch also includes the reactions of different types of glaciers to changes in their regime.

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