Changes of altitudinal zones of Werenskioldbreen and Hansbreen in period 1990 – 2008, Svalbard

ABSTRACT. This is the first (Paper I) of three companion papers focused respectively, on the estimates of the errors in ice thickness retrieved from pulsed ground-penetrating radar (GPR) data, on how to estimate the errors at the grid points of an ice-thickness DEM, and on how the latter errors, plus the boundary delineation errors, affect the ice-volume estimates. We here present a comprehensive analysis of the various errors involved in the computation of ice thickness from pulsed GPR data, assuming they have been properly migrated. We split the ice-thickness error into independent components that can be estimated separately. We consider, among others, the effects of the errors in radio-wave velocity and timing. A novel aspect is the estimate of the error in thickness due to the uncertainty in horizontal positioning of the GPR measurements, based on the local thickness gradient. Another novel contribution is the estimate of the horizontal positioning error of the GPR measurements due to the velocity of the GPR system while profiling, and the periods of GPS refreshing and GPR triggering. Their effects are particularly important for airborne profiling. We illustrate our methodology through a case study of Werenskioldbreen, Svalbard.

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“…Reynolds, 1997) and it may be preferable to use λ/2 (e.g. Hubbard and Glasser, 2005;Pérez-Gracia and others, 2009;Navarro and Eisen, 2010).…”

Section: Discussionmentioning

confidence: 99%

On the errors involved in ice-thickness estimates I: ground-penetrating radar measurement errors

et al. 2016

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“…The accuracy of the model, in root mean square error (RMSE) terms, estimated by comparing the model outcome with elevation data obtained using ICESat in February 2008, was ±5 m (Moholdt et al ., ). On the other hand, comparing the modelled positions with the positions of 18 ablation stakes on Hansbreen in September 2008 (Ignatiuk et al ., ) return a RMSE value of ±7.30 m.…”

Section: Methodsmentioning

confidence: 99%

Coast formation in an Arctic area due to glacier surge and retreat: The Hornbreen–Hambergbreen case from Spistbergen

Grabiec

Ignatiuk

Jania

et al. 2017

Earth Surf Processes Landf

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Glacierised coasts undergo faster geomorphic processes than unglaciated ones. We have studied changes of the coastal area in southern Svalbard with the glacier bridge between Torell Land and Sørkapp Land since the beginning of the 20th century. The existence of a continuous subglacial depression beneath the Hornbreen–Hambergbreen glacier system has been debated since the 1960s, with inconclusive results. In this study we assess both the subglacial topography and the bathymetry of Hornsund Fjord and Hambergbukta bay. This included ~40 km of radar surveys over the glacial system and sea depth sounding. The extent of the glaciers from maps and satellite images together with digital terrain models and surface elevation data based on GPS profiling were used to analyse geometry changes of the glacier surfaces. The results confirm the existence of a continuous subglacial depression below sea level (c. 40 m deep) between Hornsund and the Barents Sea. The Hornbreen‐Hambergbreen system has changed in shape over the past century, reflecting its dynamic origin and activity, also exemplified by the sequential surges identified since 1899. There was a pre‐surge build‐up event of Flatbreen causing a surge and subsequent lowering of the Hornbreen‐Hambergbreen frontal parts by the 1960s. After, the entire surface lowered, albeit with a delay in the Hornbreen terminal zone. Since the year 2000, Hornbreen terminus has retreated at an average rate of 106 m a−1; ~50% faster than that of Hambergbreen. If the retreat continues at the 2000–2015 average rate, the ice bridge between Hornsund and Hambergbukta will be broken sometime between 2055 and 2065 and the Hornsund strait will separate Sørkapp Land from the Spitsbergen island. The processes and events described in this study, particularly the effects of the glacier surge, may provide a model for changes likely to occur in other coastal glaciated regions experiencing rapid change. Copyright © 2017 John Wiley & Sons, Ltd.

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“…Austre Torellbreen, Hansbreen and Paierlbreen cover areas of 141, 64 and 99 km 2 , respectively. West of the THPB complex lies Werenskioldbreen (Ignatiuk et al, 2014). WSB is land terminating and somewhat smaller with 27 km 2 .…”

Section: General Characteristicsmentioning

confidence: 99%

Application of a two-step approach for mapping ice thickness to various glacier types on Svalbard

et al. 2017

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Abstract. The basal topography is largely unknown beneath most glaciers and ice caps, and many attempts have been made to estimate a thickness field from other more accessible information at the surface. Here, we present a two-step reconstruction approach for ice thickness that solves mass conservation over single or several connected drainage basins. The approach is applied to a variety of test geometries with abundant thickness measurements including marine-and landterminating glaciers as well as a 2400 km 2 ice cap on Svalbard. The input requirements are kept to a minimum for the first step. In this step, a geometrically controlled, non-local flux solution is converted into thickness values relying on the shallow ice approximation (SIA). In a second step, the thickness field is updated along fast-flowing glacier trunks on the basis of velocity observations. Both steps account for available thickness measurements. Each thickness field is presented together with an error-estimate map based on a formal propagation of input uncertainties. These error estimates point out that the thickness field is least constrained near ice divides or in other stagnant areas. Withholding a share of the thickness measurements, error estimates tend to overestimate mismatch values in a median sense. We also have to accept an aggregate uncertainty of at least 25 % in the reconstructed thickness field for glaciers with very sparse or no observations. For Vestfonna ice cap (VIC), a previous ice volume estimate based on the same measurement record as used here has to be corrected upward by 22 %. We also find that a 13 % area fraction of the ice cap is in fact grounded below sea level. The former 5 % estimate from a direct measurement interpolation exceeds an aggregate maximum range of 6-23 % as inferred from the error estimates here.

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Changes of altitudinal zones of Werenskioldbreen and Hansbreen in period 1990 – 2008, Svalbard

Cited by 18 publications

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On the errors involved in ice-thickness estimates I: ground-penetrating radar measurement errors

On the errors involved in ice-thickness estimates I: ground-penetrating radar measurement errors

Coast formation in an Arctic area due to glacier surge and retreat: The Hornbreen–Hambergbreen case from Spistbergen

Application of a two-step approach for mapping ice thickness to various glacier types on Svalbard

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