Svalbard surge dynamics derived from geometric changes

Sund, Monica; Eiken, Trond; Hagen, Jon Ove; Kääb, Andreas

doi:10.3189/172756409789624265

Cited by 113 publications

(155 citation statements)

References 38 publications

(65 reference statements)

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“…Dobrowolskibreen was the first glacier in the system to surge (Sund et al, 2009), resulting in activation of the stagnant marginal ice at the northern side of the NGS terminus (Sund and Eiken, 2010). The ERS-1-InSAR 3-day interferograms from January 1992 indicated a nucleus of increased speed just up-glacier of the confluence (Fig.…”

Section: Dobrowolskibreenmentioning

confidence: 98%

“…1). Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data from 2003, with a spatial resolution of 15 m, were used to generate a DEM following the same concept as in Sund et al (2009). ASTERderived elevations are not sufficient to detect changes in topographic details.…”

Section: Digital Elevation Modelsmentioning

confidence: 99%

“…2b). In 2003, when the Dobrowolskibreen was in stage 2 of a surge with thinning at higher elevations and thickening close to the terminus (Sund et al, 2009) …”

Section: Dobrowolskibreenmentioning

confidence: 99%

“…Up-glacier propagation of surges from their suggested trigger area has been inferred from up-glacier propagation of crevasses (Raymond, 1987;Hodgkins and Dowdeswell, 1994). While mainly focusing on relative changes in surface elevation rather than traditional surge characteristics, Sund et al (2009) found several glaciers showing signs of early-stage surges before they had reached the visible or advancing stage, and suggested three stages for the surge development during the active phase. Stage 1 is characterised by a moderate surface lowering in the upper part of the glacier and is followed by a relative thickening further downglacier in stage 2.…”

Section: Introductionmentioning

confidence: 99%

“…The joint termini of Zawadzkibreen (previously spelled Zawadskibreen), Polakkbreen and Nathorstbreen (Fig. 1) (Sund et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

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Surge dynamics in the Nathorstbreen glacier system, Svalbard

2014

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Abstract. Nathorstbreen glacier system (NGS) recently experienced the largest surge in Svalbard since 1936, and this was examined using spatial and temporal observations from DEM differencing, time series of surface velocities from satellite synthetic aperture radar (SAR) and other sources. The upper basins with maximum accumulation during quiescence corresponded to regions of initial lowering. Initial speed-up exceeded quiescent velocities by a factor of several tens. This suggests that polythermal glacier surges are initiated in the temperate area before mass is displaced downglacier. Subsequent downglacier mass displacement coincided with areas where glacier velocity increased by a factor of 100-200 times (stage 2). After more than 5 years, the joint NGS terminus advanced abruptly into the fjord during winter, increasing velocities even more. The advance was followed by up-glacier propagation of crevasses, indicating the middle and subsequently the upper part of the glaciers reacting to the mass displacement. NGS advanced ∼15 km, while another ∼3 km length was lost due to calving. Surface lowering of ∼50 m was observed in some up-glacier areas, and in 5 years the total glacier area increased by 20 %. Maximum measured flow rates were at least 25 m d −1 , 2500 times quiescent velocity, while average velocities were about 10 m d −1 . The surges of Zawadzkibreen cycle with ca. 70-year periods.

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Section: Dobrowolskibreenmentioning

confidence: 98%

Section: Digital Elevation Modelsmentioning

confidence: 99%

“…2b). In 2003, when the Dobrowolskibreen was in stage 2 of a surge with thinning at higher elevations and thickening close to the terminus (Sund et al, 2009) …”

Section: Dobrowolskibreenmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…The joint termini of Zawadzkibreen (previously spelled Zawadskibreen), Polakkbreen and Nathorstbreen (Fig. 1) (Sund et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

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Surge dynamics in the Nathorstbreen glacier system, Svalbard

2014

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Adjustment of regional climate model output for modeling the climatic mass balance of all glaciers on Svalbard

et al. 2016

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Large‐scale modeling of glacier mass balance relies often on the output from regional climate models (RCMs). However, the limited accuracy and spatial resolution of RCM output pose limitations on mass balance simulations at subregional or local scales. Moreover, RCM output is still rarely available over larger regions or for longer time periods. This study evaluates the extent to which it is possible to derive reliable region‐wide glacier mass balance estimates, using coarse resolution (10 km) RCM output for model forcing. Our data cover the entire Svalbard archipelago over one decade. To calculate mass balance, we use an index‐based model. Model parameters are not calibrated, but the RCM air temperature and precipitation fields are adjusted using in situ mass balance measurements as reference. We compare two different calibration methods: root mean square error minimization and regression optimization. The obtained air temperature shifts (+1.43°C versus +2.22°C) and precipitation scaling factors (1.23 versus 1.86) differ considerably between the two methods, which we attribute to inhomogeneities in the spatiotemporal distribution of the reference data. Our modeling suggests a mean annual climatic mass balance of −0.05 ± 0.40 m w.e. a−1 for Svalbard over 2000–2011 and a mean equilibrium line altitude of 452 ± 200 m above sea level. We find that the limited spatial resolution of the RCM forcing with respect to real surface topography and the usage of spatially homogeneous RCM output adjustments and mass balance model parameters are responsible for much of the modeling uncertainty. Sensitivity of the results to model parameter uncertainty is comparably small and of minor importance.

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Automated detection of unstable glacier flow and a spectrum of speedup behavior in the Alaska Range

Herreid

Truffer

2016

JGR Earth Surface

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Surge‐type glaciers are loosely defined as glaciers that experience periodic alterations between slow and fast flow regimes. Glaciers from a variety of mountain ranges around the world have been classified as surge type, yet consensus of what defines a glacier as surge type has not always been met. A common source of dispute is the lack of a succinct and globally applicable delimiter between a surging and nonsurging glacier. The attempt is often a Boolean classification; however, glacier speedup events can vary significantly with respect to event magnitude, duration, and the fraction of the glacier that participates in the speedup. For this study, we first updated the inventory of glaciers that show flow instabilities in the Alaska Range and then quantified the spectrum of speedup behavior. We developed a new method that automatically detects glaciers with flow instabilities. Our automated results show a 91% success rate when compared to direct observations of speedup events and glaciers that are suspected to display unstable flow based on surface features. Through a combination of observations from the Landsat archive and previously published data, our inventory now contains 36 glaciers that encompass at least one branch exhibiting unstable flow and we document 53 speedup events that occurred between 1936 and 2014. We then present a universal method for comparing glacier speedup events based on a normalized event magnitude metric. This method provides a consistent way to include and quantify the full spectrum of speedup events and allows for comparisons with glaciers that exhibit clear surge characteristics yet have no observed surge event to date. Our results show a continuous spectrum of speedup magnitudes, from steady flow to clearly surge type, which suggests that qualitative classifications, such as “surge‐type” or “pulse‐type” behavior, might be too simplistic and should be accompanied by a standardized magnitude metric.

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Svalbard surge dynamics derived from geometric changes

Cited by 113 publications

References 38 publications

Surge dynamics in the Nathorstbreen glacier system, Svalbard

Surge dynamics in the Nathorstbreen glacier system, Svalbard

Adjustment of regional climate model output for modeling the climatic mass balance of all glaciers on Svalbard

Automated detection of unstable glacier flow and a spectrum of speedup behavior in the Alaska Range

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