Error sources and guidelines for quality assessment of glacier area, elevation change, and velocity products derived from satellite data in the Glaciers_cci project

Paul, Frank; Bolch, Tobias; Briggs, K.; Kääb, Andreas; McMillan, Malcolm; McNabb, Robert; Nägler, Thomas; Nuth, Christopher; Rastner, Philipp; Strozzi, Tazio; Wuite, Jan

doi:10.1016/j.rse.2017.08.038

Cited by 129 publications

(157 citation statements)

References 131 publications

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“…Common problems in ice‐cover mapping from optical imagery are related to shadows as well as cloud and snow cover (Figures a and b; e.g., Winsvold et al, ). In manual approaches, the selection of suitable images is therefore an important but time‐consuming first step (Paul et al, ). In our automatic approach, we tackled these problems by using a pixel‐based instead of an image‐based approach.…”

Section: Methodsmentioning

confidence: 99%

Global Assessment of Supraglacial Debris‐Cover Extents

Scherler

Wulf

Gorelick

2018

Geophysical Research Letters

173

206

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Rocky debris on glacier surfaces influences ice melt rates and the response of glaciers to climate change. However, scarce data on the extent and evolution of supraglacial debris cover have so far limited its inclusion in regional to global glacier models. Here we present global data sets of supraglacial debris‐cover extents, based on Landsat 8 and Sentinel‐2 optical satellite imagery. We find that about 4.4% (~26,000 km2) of all glacier areas (excluding the Greenland ice sheet and Antarctica) are covered with debris, but that the distribution is heterogeneous. The largest debris‐covered areas are located in high‐mountain ranges, away from the poles. At a global scale, we find a negative scaling relationship between glacier size and percentage of debris. Therefore, the influence of debris cover on glacier mass balances is expected to increase in the future, as glaciers continue to shrink.

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Section: Methodsmentioning

confidence: 99%

Global Assessment of Supraglacial Debris‐Cover Extents

Scherler

Wulf

Gorelick

2018

Geophysical Research Letters

173

206

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“…An assessment of the uncertainties in the ice displacement maps is essential for the interpretation of changes in glacier dynamics, but is inherently difficult because glacier surface velocities are variable temporally and spatially [49]. For an estimation of the error we compare our satellite-derived displacement maps with products derived from independent image data of better resolution and precision.…”

Section: Error Assessmentmentioning

confidence: 99%

Circum-Arctic Changes in the Flow of Glaciers and Ice Caps from Satellite SAR Data between the 1990s and 2017

et al. 2017

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Abstract:We computed circum-Arctic surface velocity maps of glaciers and ice caps over the Canadian Arctic, Svalbard and the Russian Arctic for at least two times between the 1990s and 2017 using satellite SAR data. Our analyses are mainly performed with offset-tracking of ALOS-1 PALSAR-1 (2007)(2008)(2009)(2010)(2011) and Sentinel-1 (2015Sentinel-1 ( -2017 data. In certain cases JERS-1 SAR (1994)(1995)(1996)(1997)(1998), TerraSAR-X (2008TerraSAR-X ( -2012, Radarsat-2 (2009Radarsat-2 ( -2016 and ALOS-2 PALSAR-2 (2015-2016) data were used to fill-in spatial or temporal gaps. Validation of the latest Sentinel-1 results was accomplished by means of SAR data at higher spatial resolution (Radarsat-2 Wide Ultra Fine) and ground-based measurements. In general, we observe a deceleration of flow velocities for the major tidewater glaciers in the Canadian Arctic and an increase in frontal velocity along with a retreat of frontal positions over Svalbard and the Russian Arctic. However, all regions have strong accelerations for selected glaciers. The latter developments can be well traced based on the very high temporal sampling of Sentinel-1 acquisitions since 2015, revealing new insights in glacier dynamics. For example, surges on Spitsbergen (e.g., Negribreen, Nathorsbreen, Penckbreen and Strongbreen) have a different characteristic and timing than those over Eastern Austfonna and Edgeoya (e.g., Basin 3, Basin 2 and Stonebreen). Events similar to those ongoing on Eastern Austofonna were also observed over the Vavilov Ice Cap on Severnaya Zemlya and possibly Simony Glacier on Franz-Josef Land. Collectively, there seems to be a recently increasing number of glaciers with frontal destabilization over Eastern Svalbard and the Russian Arctic compared to the 1990s.

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“…where σ z was estimated based on the mean off-glacier difference between the two DEMs after co-registration and the residual differences after co-registration to ICESat (i.e., the triangulation procedure described in Paul et al, 2017), A is the glacier area, σ area is the error in glacier area, here equal to 0.1 in order to conservatively consider the uncertainty for the glacier areas which is 5% (or 0.05) according to Rastner et al (2012), and z is the mean elevation difference of on-glacier pixels. The uncertainty introduced by the void-filing approach (σ void fill ) we estimated for each glacier as 1.96 standard deviations of the elevation changes resulting from the two void-filling methods considered to produce reasonable results (i.e., local mean and local median, cf.…”

Section: Individual Error Componentsmentioning

confidence: 99%

Elevation Changes of West-Central Greenland Glaciers From 1985 to 2012 From Remote Sensing

2020

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Greenlandic glaciers distinct from the ice sheet make up 12% of the global glacierized area and store about 10% of the global glacier ice volume (Farinotti et al., 2019). However, knowledge about recent climate change-induced volume changes of these 19,000 individual glaciers is limited. The small number of available glaciological and geodetic mass-balance observations have a limited spatial coverage, and the representativeness of these measurements for the region is largely unknown, factors which make a regional assessment of mass balance challenging. Here we use two recently released digital elevation models (DEMs) to assess glacier-wide elevation changes of 1,526 glaciers covering 3,785 km 2 in west-central Greenland: The historical AeroDEM representing the surface in 1985 and a TanDEM-X composite representing 2010-2014. The results show that on average glacier surfaces lowered by about 14.0 ± 4.6 m from 1985 until 2012 or 0.5 ± 0.2 m yr −1 , which is equivalent to a sample mass loss of ∼45.1 ± 14.9 Gt in total or 1.7 ± 0.6 Gt yr −1 . Challenges arise from the nature of the DEMs, such as large areas of data voids, fuzzy acquisition dates, and potential radar penetration. We compared several different interpolation methods to assess the best method to fill data voids and constrain unknown survey dates and the associated uncertainties with each method. The potential radar penetration is considered negligible for this assessment in view of the overall glacier changes, the length of the observation period, and the overall uncertainties. A comparison with earlier studies indicates that for glacier change assessments based on ICESat, data selection and averaging methodology strongly influences the results from these spatially limited measurements. This study promotes improved assessments of the contribution of glaciers to sea-level rise and encourages to extend geodetic glacier mass balances to all glaciers on Greenland.

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Error sources and guidelines for quality assessment of glacier area, elevation change, and velocity products derived from satellite data in the Glaciers_cci project

Abstract: This is a repository copy of Error sources and guidelines for quality assessment of glacier area, elevation change, and velocity products derived from satellite data in the Glaciers_cci project.

Cited by 129 publications

References 131 publications

Global Assessment of Supraglacial Debris‐Cover Extents

Global Assessment of Supraglacial Debris‐Cover Extents

Circum-Arctic Changes in the Flow of Glaciers and Ice Caps from Satellite SAR Data between the 1990s and 2017

Elevation Changes of West-Central Greenland Glaciers From 1985 to 2012 From Remote Sensing

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