Ice thickness and volume of the Renland Ice Cap, East Greenland

Koldtoft, Iben; Grinsted, Aslak; Vinther, Bo M.; Hvidberg, Christine S.

doi:10.1017/jog.2021.11

Cited by 6 publications

(8 citation statements)

References 41 publications

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“…It should be noted that one is not guaranteed that the misfit between measured surface elevation and modelled surface elevation will reduce after each iteration. However, this iterative inverse method which I am using have shown promising results in other studies [Koldtoft et al, 2020, Pelt et al, 2013.…”

Section: Modelling Choicesmentioning

confidence: 97%

“…To generate a best guess of the ice thickness and thereby also bedrock topography, I have used an iterative inverse method [Koldtoft et al, 2020, Pelt et al, 2013 by tuning to the surface elevation, S DEM , from ArcticDEM assuming that the ice cap is in steady state. PISM is used as a forward model in this process, where the bedrock, B, and the ice thickness, H, is changed after each iteration, i, using…”

Section: Modelling Purpose and Proceduresmentioning

confidence: 99%

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Surface velocity and ice thickness of the Müller ice cap, Axel Heiberg Island

Zinck¹

2021

Preprint

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Muller ice cap is situated on Axel Heiberg Island in Arctic Canada. It is characterised by a mountanious region separating the ice cap in the east from the outlet glaciers in the west. Research has taken place on the outlet glaciers of the ice cap since 1959, but only limited research has been conducted on the main ice cap, and no full depth ice cores have ever been drilled. The interesting location of the ice cap facing the Arctic Ocean, the chance of finding ice dating back to the Innuitian Ice Sheet, and the fact that no full depth ice cores have been drilled, makes it an obvious place to do so. In order to achieve a long and undisturbed chronology of the ice core, one needs to find a location for the drilling site, where there is a great ice thickness, low surface velocity and little melt. In this project the aim is to make surface velocity maps of the ice cap and estimate the ice thickness to be able to come up with suggestions of possible drill site areas.Surface velocities are calculated using feature tracking of optical satellite images from the Landsat satellites in the period of 2004-2019. A median velocity map of all Landsat 8 velocity maps is used as validation in modelling the ice thickness and in the investigation of possible drill site areas.To estimate the ice thickness various methods are used and are being compared to the ice thickness measured by Operation IceBridge. The first method is an iterative inverse method where the ice sheet model PISM works as a forward model. The model is found to work rather well on the ice cap, with a root mean squared error (RMS) of 138.9 m, but overestimates the ice thickness on the outlet glaciers. The second model uses a simple inversion of the shallow ice approximation. It overestimates the ice thickness in areas with low surface slope, but has a RMS of 131.4 m on the ice cap. The third and and fourth models uses Monte Carlo sampling methods of the shallow ice approximation without and with sliding, respectively. The latter uses an initial ice thickness guess, and the modelled ice thickness was proofed not to differ from that initial guess at all. The RMSs on the icecap of the two models were found to be 132.1 m and 129.9 m, respectively. Finally, the fifth model uses the PISM setup but with an initial geometry defined by the SIA inversion. The RMS on the ice cap is found to be 135.4 m.Based on the median Landsat 8 surface velocity map, the modelled ice thicknesses and the surface elevation from the Arctic Digital Elevation Model, a map of suggested drill site areas is made. The site which fulfilled the criteria the most is located at 526629 m easting and 8866463 m northing in UTM zone 15N. In this site the surface velocity is 1.2 m yr−1, the surface elevation is 1804 m and the modelled ice thicknesses varies from 535-579 m. The melt in this area is estimated to be less than 20 melt days per year based on the backscatter from Sentinel-1.

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Section: Modelling Choicesmentioning

confidence: 97%

Section: Modelling Purpose and Proceduresmentioning

confidence: 99%

Surface velocity and ice thickness of the Müller ice cap, Axel Heiberg Island

Zinck¹

2021

Preprint

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“…where B n is the bedrock used to force PISM in iteration n. K is a relaxation parameter which ensures that the bedrock topography is not overcompensated (van Pelt et al, 2013;Koldtoft et al, 2021). In this study we use a varying relaxation parameter with elevation, to prevent overcompensation in bedrock and ice build-up on the outlet glaciers west of the ice cap (see Fig.…”

Section: Pismmentioning

confidence: 99%

Comment on tc-2021-300

2021

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“…Localized elevation errors and data gaps could affect the estimated ice thickness by 5 %-25 % using Huss-Farinotti model (Huss and Farinotti, 2012). Therefore, it is imperative to choose a suitable DEM source for regional glacier thickness modeling (Koldtoft et al, 2021). Farinotti et al (2017Farinotti et al ( , 2021 intercompare the performance of several ITIMs and suggest that consideration of the uncertainty in the input data could improve the model output.…”

Section: Introductionmentioning

confidence: 99%

Towards ice-thickness inversion: an evaluation of global digital elevation models (DEMs) in the glacierized Tibetan Plateau

Chen

Zhang

et al. 2022

The Cryosphere

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Abstract. Accurate estimates of regional ice thickness, which are generally produced by ice-thickness inversion models, are crucial for assessments of available freshwater resources and sea level rise. A digital elevation model (DEM) derived from surface topography of glaciers is a primary data source for such models. However, the scarce in situ measurements of glacier surface elevation limit the evaluation of DEM uncertainty. Hence the influence of DEM uncertainty on ice-thickness modeling remains unclear over the glacierized area of the Tibetan Plateau (TP). Here, we examine the performance of six widely used and mainly global-scale DEMs: AW3D30 (ALOS – Advanced Land Observing Satellite – World 3D – 30 m; 30 m), SRTM-GL1 (Shuttle Radar Topography Mission Global 1 arc second; 30 m), NASADEM (NASA Digital Elevation Model; 30 m), TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement, synthetic-aperture radar; 90 m), SRTM v4.1 (Shuttle Radar Topography Mission; 90 m), and MERIT (Multi-Error-Removed Improved-Terrain; 90 m) over the glacierized TP by comparison with ICESat-2 (Ice, Cloud and land Elevation Satellite) laser altimetry data while considering the effects of glacier dynamics, terrain factors, and DEM misregistration. The results reveal NASADEM to be the best performer in vertical accuracy, with a small mean error (ME) of 0.9 m and a root mean squared error (RMSE) of 12.6 m, followed by AW3D30 (2.6 m ME and 11.3 m RMSE). TanDEM-X also performs well (0.1 m ME and 15.1 m RMSE) but suffers from serious errors and outliers on steep slopes. SRTM-based DEMs (SRTM-GL1, SRTM v4.1, and MERIT) (13.5–17.0 m RMSE) had an inferior performance to NASADEM. Errors in the six DEMs increase from the south-facing to the north-facing aspect and become larger with increasing slope. Misregistration of the six DEMs relative to the ICESat-2 footprint in most glacier areas is small (less than one grid spacing). In a next step, the influence of six DEMs on four ice-thickness inversion models – GlabTop2 (Glacier bed Topography), Open Global Glacier Model (OGGM), Huss–Farinotti (HF), and Ice Thickness Inversion Based on Velocity (ITIBOV) – is intercompared. The results show that GlabTop2 is sensitive to the accuracy of both elevation and slope, while OGGM and HF are less sensitive to DEM quality and resolution, and ITIBOV is the most sensitive to slope accuracy. NASADEM is the best choice for ice-thickness estimates over the whole TP.

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Ice thickness and volume of the Renland Ice Cap, East Greenland

Cited by 6 publications

References 41 publications

Surface velocity and ice thickness of the Müller ice cap, Axel Heiberg Island

Surface velocity and ice thickness of the Müller ice cap, Axel Heiberg Island

Comment on tc-2021-300

Towards ice-thickness inversion: an evaluation of global digital elevation models (DEMs) in the glacierized Tibetan Plateau

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