scholarly journals Brief communication: Unabated wastage of the Juneau and Stikine icefields (southeast Alaska) in the early 21<sup>st</sup> century

2018 ◽  
Author(s):  
Etienne Berthier ◽  
Christopher Larsen ◽  
William Durkin ◽  
Michael Willis ◽  
Matthew Pritchard
Keyword(s):  
Mass Loss ◽  
Field Measurements ◽  
Radar Signal ◽  
Srtm Dem ◽  
Laser Altimetry ◽  
Southeast Alaska ◽  
Early 21St Century ◽  
The North ◽  
Digital Elevation ◽  
Geodetic Mass Balance

Abstract. The large Juneau and Stikine icefields (Alaska, JIF and SIF) lost mass rapidly in the second part of the 20th century. Laser altimetry, gravimetry and sparse field measurements suggest continuing mass loss in the early 21st century. However, two recent studies based on time series of SRTM and ASTER digital elevation models (DEMs) indicate a slowdown in mass loss after 2000. Here, the ASTER-based geodetic mass balance is recalculated, carefully avoiding the use of the SRTM DEM because of the unknown penetration depth of the C-Band radar signal. We find strongly negative mass balances from 2000 to 2016 (−0.68 ± 0.15 m w.e. a-1 for JIF and −0.83 ± 0.12 m w.e. a-1 for SIF), in agreement with laser altimetry, confirming that mass losses are continuing at unabated rates for both icefields. The SRTM DEM should be avoided or used very cautiously to estimate glacier volume change, especially in the North Hemisphere and over timescales of less than ~ 20 yrs.

scholarly journals Brief communication: Unabated wastage of the Juneau and Stikine icefields (southeast Alaska) in the early 21st century

2018 ◽  
Vol 12 (4) ◽  
pp. 1523-1530 ◽  
Author(s):  
Etienne Berthier ◽  
Christopher Larsen ◽  
William J. Durkin ◽  
Michael J. Willis ◽  
Matthew E. Pritchard
Keyword(s):  
Mass Loss ◽  
21St Century ◽  
Thermal Emission ◽  
Field Measurements ◽  
Radar Signal ◽  
Mass Balances ◽  
Srtm Dem ◽  
Laser Altimetry ◽  
Early 21St Century ◽  
The Early 21St Century

Abstract. The large Juneau and Stikine icefields (Alaska) lost mass rapidly in the second part of the 20th century. Laser altimetry, gravimetry and field measurements suggest continuing mass loss in the early 21st century. However, two recent studies based on time series of Shuttle Radar Topographic Mission (SRTM) and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) digital elevation models (DEMs) indicate a slowdown in mass loss after 2000. Here, the ASTER-based geodetic mass balances are recalculated carefully avoiding the use of the SRTM DEM because of the unknown penetration depth of the C-band radar signal. We find strongly negative mass balances from 2000 to 2016 (−0.68 ± 0.15 m w.e. a−1 for the Juneau Icefield and −0.83 ± 0.12 m w.e. a−1 for the Stikine Icefield), in agreement with laser altimetry, confirming that mass losses are continuing at unabated rates for both icefields. The SRTM DEM should be avoided or used very cautiously to estimate glacier volume change, especially in the North Hemisphere and over timescales of less than ∼ 20 years.

scholarly journals Balanced conditions or slight mass gain of glaciers in the Lahaul and Spiti region (northern India, Himalaya) during the nineties preceded recent mass loss

2013 ◽  
Vol 7 (2) ◽  
pp. 569-582 ◽  
Author(s):  
C. Vincent ◽  
Al. Ramanathan ◽  
P. Wagnon ◽  
D. P. Dobhal ◽  
A. Linda ◽  
...  
Keyword(s):  
Mass Loss ◽  
Field Measurements ◽  
Mass Gain ◽  
Negative Mass ◽  
Northern India ◽  
Chhota Shigri Glacier ◽  
Digital Elevation ◽  
Recent Compilation ◽  
Spiti Region ◽  
Dem Differencing

Abstract. The volume change of the Chhota Shigri Glacier (India, 32° 20 N, 77° 30' E) between 1988 and 2010 has been determined using in situ geodetic measurements. This glacier has experienced only a slight mass loss between 1988 and 2010 (−3.8 ± 2.0 m w.e. (water equivalent) corresponding to −0.17 ± 0.09 m w.e. yr−1). Using satellite digital elevation models (DEM) differencing and field measurements, we measure a negative mass balance (MB) between 1999 and 2010 (−4.8 ± 1.8 m w.e. corresponding to −0.44 ± 0.16 m w.e. yr−1). Thus, we deduce a slightly positive or near-zero MB between 1988 and 1999 (+1.0 ± 2.7 m w.e. corresponding to +0.09 ± 0.24 m w.e. yr−1). Furthermore, satellite DEM differencing reveals that the MB of the Chhota Shigri Glacier (−0.39 ± 0.15 m w.e. yr−1) has been only slightly less negative than the MB of a 2110 km2 glaciarized area in the Lahaul and Spiti region (−0.44 ± 0.09 m w.e. yr−1) during 1999−2011. Hence, we conclude that the ice wastage is probably moderate in this region over the last 22 yr, with near equilibrium conditions during the nineties, and an ice mass loss after. The turning point from balanced to negative mass budget is not known but lies probably in the late nineties and at the latest in 1999. This positive or near-zero MB for Chhota Shigri Glacier (and probably for the surrounding glaciers of the Lahaul and Spiti region) during at least part of the 1990s contrasts with a recent compilation of MB data in the Himalayan range that indicated ice wastage since 1975. However, in agreement with this compilation, we confirm more negative balances since the beginning of the 21st century.

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 A doubling of glacier mass loss in the Karlik Range, easternmost Tien Shan, between the periods 1972–2000 and 2000–2015

2020 ◽  
pp. 1-12
Author(s):  
Zhujun Wan ◽  
Yetang Wang ◽  
Shugui Hou ◽  
Baojuan Huai ◽  
Qi Liu
Keyword(s):  
Climate Change ◽  
Mass Loss ◽  
Radar Data ◽  
Tien Shan ◽  
Topographic Maps ◽  
Glacier Mass Balance ◽  
Regional Warming ◽  
Early 21St Century ◽  
Digital Elevation ◽  
X Band

Abstract Despite a number of studies reporting glacier extent changes and their response to climate change over the eastern Tien Shan, glacier mass-balance changes over multiple decades are still not well reconstructed. Here, glacier mass budgets on the Karlik Range, easternmost Tien Shan during the time spans of 1972–2000 and 2000–2015 are quantified using digital elevation models reconstructed from topographic maps, SRTM X-band radar data and ASTER images. The results exhibit significant glacier mass loss in the Karlik Range for the two time spans, with a mean mass loss of −0.19 ± 0.08 m w.e. a−1 for the 1972–2000 period and −0.45 ± 0.17 m w.e. a−1 for the 2000–2015 period. The doubling of mass loss over the latter period suggests an acceleration of glacier mass loss in the early 21st century. The accelerated mass loss is associated with regional warming whereas the decline in annual precipitation is not significant.

scholarly journals 21st-century increase in glacier mass loss in the Wrangell Mountains, Alaska, USA, from airborne laser altimetry and satellite stereo imagery

2014 ◽  
Vol 60 (220) ◽  
pp. 283-293 ◽  
Author(s):  
Indrani Das ◽  
Regine Hock ◽  
Etienne Berthier ◽  
Craig S. Lingle
Keyword(s):  
Mass Loss ◽  
Mass Balance ◽  
High Elevation ◽  
Center Line ◽  
Laser Altimetry ◽  
Tidewater Glaciers ◽  
Airborne Laser ◽  
Digital Elevation ◽  
Stereo Imagery ◽  
Elevation Model

AbstractAlaskan glaciers are among the largest regional contributors to sea-level rise in the latter half of the 20th century. Earlier studies have documented extensive and accelerated ice wastage in most regions of Alaska. Here we study five decades of mass loss on high-elevation, land-terminating glaciers of the Wrangell Mountains (~ 4900 km2) in central Alaska based on airborne center-line laser altimetry data from 2000 and 2007, a digital elevation model (DEM) from ASTER and SPOT5, and US Geological Survey topographic maps from 1957. The regional mass-balance estimates derived from center-line laser altimetry profiles using two regional extrapolation techniques agree well with that from DEM differencing. Repeat altimetry measurements reveal accelerated mass loss over the Wrangell Mountains, with the regional mass-balance rate evolving from –0.07 ± 0.19 m w.e. a–1 during 1957–2000 to –0.24 ± 0.16 m w.e. a–1 during 2000–07. Nabesna, the largest glacier in this region (˜1056 km2), lost mass four times faster during 2000–07 than during 1957–2000. Although accelerated, the mass change over this region is slower than in other glacierized regions of Alaska, particularly those with tidewater glaciers. Together, our laser altimetry and satellite DEM analyses demonstrate increased wastage of these glaciers during the last 50 years.

scholarly journals Long-term contributions of Baffin and Bylot Island Glaciers to sea level rise: an integrated approach using airborne and satellite laser altimetry, stereoscopic imagery and satellite gravimetry

2012 ◽  
Vol 6 (2) ◽  
pp. 1563-1610 ◽  
Author(s):  
A. S. Gardner ◽  
G. Moholdt ◽  
A. Arendt ◽  
B. Wouters
Keyword(s):  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
Integrated Approach ◽  
Laser Altimetry ◽  
Satellite Gravimetry ◽  
Ice Cap ◽  
Digital Elevation ◽  
Grace Satellite Gravimetry ◽  
Summer Temperatures

Abstract. Canadian Arctic glaciers have recently contributed large volumes of meltwater to the world's oceans. To place recently observed glacier wastage into a historical perspective and to determine the region's longer-term (~50 years) contribution to sea level, we estimate mass and volume changes for the glaciers of Baffin and Bylot Islands using Digital Elevation Models generated from airborne and satellite stereoscopic imagery and elevation postings from repeat airborne and satellite laser altimetry. In addition, we update existing glacier mass change records from GRACE satellite gravimetry to cover the period from 2003 to 2011. Using an integrated approach we find that the rate of mass loss from the region's glaciers increased from 11.1 ± 1.8 Gt a−1 (–270 ± 40 kg m−2 a−1) in 1963–2006 to 23.8 ± 3.1 Gt a−1 (–580 ± 80 kg m2 a−1) in 2003–2011. The doubling of the rate of mass loss is attributed to higher temperatures in summer with little change in annual precipitation. Through both direct and indirect effects, changes in summer temperatures accounted for 68–98 % of the variance in the rate of mass loss to which the Barnes Ice Cap was found to be 1.6 times more sensitive than either the Penny Ice Cap or the regions glaciers as a whole. Between 2003 and 2011 the glaciers of Baffin and Bylot Islands contributed 0.07 ± 0.01 mm a−1 to sea level rise, a rate equivalent to the contribution coming from Patagonian glaciers. Over the 48-year period between 1963 and 2011 the glaciers of Baffin and Bylot Islands contributed 1.7 mm to the world's oceans.

scholarly journals SRTM DEM levels over papyrus swamp vegetation – a correction approach

2009 ◽  
Vol 21 ◽  
pp. 81-84 ◽  
Author(s):  
G. Petersen ◽  
I. Lebed ◽  
N. Fohrer
Keyword(s):  
Correction Factor ◽  
Ground Level ◽  
Shuttle Radar Topography Mission ◽  
Radar Signal ◽  
Real Surface ◽  
Srtm Dem ◽  
Ground Control Points ◽  
Digital Elevation ◽  
Elevation Data ◽  
Elevation Model

Abstract. The SRTM DEM, a digital elevation model based on the Shuttle Radar Topography Mission of February 2000 is a source of elevation data with nearly worldwide coverage. It has proven its usefulness in various regions but problems persist for densely vegetated areas where, caused by the organic matter and water content of the vegetation, the radar signal is reflected at some level between the vegetation canopy and the ground level. This level varies with different types and densities of vegetation cover and has so far not been assessed for papyrus areas. The paper describes the approach and establishment of a correction factor for a pilot area in the Sudd swamps of southern Sudan based on comparison of SRTM reference levels and ground control points collected during field surveys between 2004 and 2006. Results show a correction factor between the sensed and the real surface of 4.66 m and a average penetration depth of the radar signal into the dense papyrus vegetation of 0.34 m.

scholarly journals Combined Block Adjustment for Optical Satellite Stereo Imagery Assisted by Spaceborne SAR and Laser Altimetry Data

2021 ◽  
Vol 13 (16) ◽  
pp. 3062
Author(s):  
Guo Zhang ◽  
Boyang Jiang ◽  
Taoyang Wang ◽  
Yuanxin Ye ◽  
Xin Li
Keyword(s):  
Large Scale ◽  
Satellite Image ◽  
Field Measurements ◽  
High Elevation ◽  
Global Scale ◽  
Stereo Image ◽  
Image Process ◽  
Control Points ◽  
Altimetry Data ◽  
Laser Altimetry

To ensure the accuracy of large-scale optical stereo image bundle block adjustment, it is necessary to provide well-distributed ground control points (GCPs) with high accuracy. However, it is difficult to acquire control points through field measurements outside the country. Considering the high planimetric accuracy of spaceborne synthetic aperture radar (SAR) images and the high elevation accuracy of satellite-based laser altimetry data, this paper proposes an adjustment method that combines both as control sources, which can be independent from GCPs. Firstly, the SAR digital orthophoto map (DOM)-based planar control points (PCPs) acquisition is realized by multimodal matching, then the laser altimetry data are filtered to obtain laser altimetry points (LAPs), and finally the optical stereo images’ combined adjustment is conducted. The experimental results of Ziyuan-3 (ZY-3) images prove that this method can achieve an accuracy of 7 m in plane and 3 m in elevation after adjustment without relying on GCPs, which lays the technical foundation for a global-scale satellite image process.

scholarly journals Heterogeneous spatial and temporal pattern of surface elevation change and mass balance of the Patagonian ice fields between 2000 and 2016

2019 ◽  
Vol 13 (9) ◽  
pp. 2511-2535 ◽  
Author(s):  
Wael Abdel Jaber ◽  
Helmut Rott ◽  
Dana Floricioiu ◽  
Jan Wuite ◽  
Nuno Miranda
Keyword(s):  
Spatial Pattern ◽  
Mass Balance ◽  
Temporal Trend ◽  
Sar Interferometry ◽  
Surface Elevation ◽  
Radar Signal ◽  
Elevation Change ◽  
Mass Losses ◽  
Digital Elevation ◽  
Surface Elevation Change

Abstract. The northern and southern Patagonian ice fields (NPI and SPI) have been subject to accelerated retreat during the last decades, with considerable variability in magnitude and timing among individual glaciers. We derive spatially detailed maps of surface elevation change (SEC) of NPI and SPI from bistatic synthetic aperture radar (SAR) interferometry data of the Shuttle Radar Topography Mission (SRTM) and TerraSAR-X add-on for Digital Elevation Measurements (TanDEM-X) for two epochs, 2000–2012 and 2012–2016, and provide data on changes in surface elevation and ice volume for the individual glaciers and the ice fields at large. We apply advanced TanDEM-X processing techniques allowing us to cover 90 % and 95 % of the area of NPI and 97 % and 98 % of SPI for the two epochs, respectively. Particular attention is paid to precisely co-registering the digital elevation models (DEMs), accounting for possible effects of radar signal penetration through backscatter analysis and correcting for seasonality biases in case of deviations in repeat DEM coverage from full annual time spans. The results show a different temporal trend between the two ice fields and reveal a heterogeneous spatial pattern of SEC and mass balance caused by different sensitivities with respect to direct climatic forcing and ice flow dynamics of individual glaciers. The estimated volume change rates for NPI are -4.26±0.20 km3 a−1 for epoch 1 and -5.60±0.74 km3 a−1 for epoch 2, while for SPI these are -14.87±0.52 km3 a−1 for epoch 1 and -11.86±1.99 km3 a−1 for epoch 2. This corresponds for both ice fields to an eustatic sea level rise of 0.048±0.002 mm a−1 for epoch 1 and 0.043±0.005 mm a−1 for epoch 2. On SPI the spatial pattern of surface elevation change is more complex than on NPI and the temporal trend is less uniform. On terminus sections of the main calving glaciers of SPI, temporal variations in flow velocities are a main factor for differences in SEC between the two epochs. Striking differences are observed even on adjoining glaciers, such as Upsala Glacier, with decreasing mass losses associated with slowdown of flow velocity, contrasting with acceleration and increase in mass losses on Viedma Glacier.

Evaluation of planting sites common to a southeast Alaska clear-cut. IV. Nutrient levels in ectomycorrhizal Sitka spruce seedlings

1987 ◽  
Vol 17 (4) ◽  
pp. 340-345 ◽  
Author(s):  
Roy C. Sidle ◽  
Charles G. Shaw III
Keyword(s):  
Ectomycorrhizal Fungi ◽  
Mineral Soil ◽  
Sitka Spruce ◽  
Southeast Alaska ◽  
Clear Cut ◽  
The North ◽  
Rotten Wood ◽  
North Side ◽  
Foliar Concentrations ◽  
Nutritional Benefits

Sitka spruce (Piceasitchensis (Bong.) Carr.) seedlings colonized by the ectomycorrhizal fungi Laccarialaccata (Scop. ex Fr.) Berk and Br., Hebelomacrustuliniforme (Bull, ex St. Amans) Quel., or Cenococcumgeophilum Fr. and a noninoculated control were planted on rotten wood, undisturbed duff, undisturbed duff on the north side of large stumps, and exposed mineral soil in an area recently clear-cut on Chichagof Island, southeast Alaska. Uptake and concentrations of N, P, K, Ca, Mg, and several micronutrients in foliage, stems, and roots were determined 2 years after outplanting. There were no significant interactions between fungal treatments and microsite types for uptake or concentration of any nutrient. Uptake and concentrations of N and P in foliage and roots did not differ significantly among fungal treatments. Foliar K and Cu concentrations were significantly higher in control seedlings than in those with L. laccata ectomycorrhizae. Calcium was the only nutrient analyzed that was present in higher concentrations in seedlings inoculated with H. crustuliniforme than in controls. Concentrations of foliar P, Mn, and Zn were significantly greater in seedlings grown on undisturbed duff (protected north side) than in seedlings grown on exposed mineral soil. However, foliar concentrations of all nutrients tested were not significantly different between seedlings grown on undisturbed duff (unprotected sites) and those grown on mineral soil. Seedlings grown on rotten wood had significantly greater concentrations of foliar Ca than seedlings grown on either exposed mineral soil or undisturbed duff. The on-site colonization of control seedlings after outplanting indicates that resident ectomycorrhizal fungi readily establish and appear to provide equal if not improved nutrient benefits compared to inoculated seedlings. Greater nutritional benefits were derived by planting on certain microsite types (duff and protected duff) than by inoculating with specific ectomycorrhizal fungi.

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