Glacier surge dynamics of Sortebræ, east Greenland, from synthetic aperture radar feature tracking

Pritchard, Hamish D.; Murray, Tavi; Luckman, Adrian; Strozzi, Tazio; Barr, SL

doi:10.1029/2004jf000233

Cited by 81 publications

(80 citation statements)

References 66 publications

(98 reference statements)

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“…The flow rates of NGS during surge advance are consistent with those observed from other large surges in Svalbard such as Hinlopenbreen (Liestøl, 1973) and Bråsvellbreen (Schytt, 1969), although the NGS did not entirely reach the levels found at Negribreen (Liestøl, 1969). The NGS velocities are also comparable with velocities in other regions, for example West Fork Glacier, Alaska (Harrison et al, 1994), and Sortebrae, (Pritchard et al, 2005).…”

Section: Front Velocities Advance Rate and Surge Terminationsupporting

confidence: 82%

“…Immediately prior to the advance of NGS, the front of the NathorstbreenZawadzkibreen section showed few visible signs of surge behaviour. The situation is comparable to that of Sortebrae, Greenland, where a gradual retreat took place before a rapid switch to advance (Pritchard et al, 2005). Nevertheless, our study proves that retreated front positions are not evidence of contemporary quiescence.…”

Section: Front Velocities Advance Rate and Surge Terminationsupporting

confidence: 73%

“…Nevertheless, our study proves that retreated front positions are not evidence of contemporary quiescence. The NGS dynamics are consistent with the propagation pattern found on Variegated Glacier (Raymond and Harrison, 1988) and differ from the suggested fast flow initiation in the lower parts of other tidewater glaciers, such as Monacobreen (Murray et al, 2003a, b) and Sortebrae (Pritchard et al, 2005). Interpretation for these two could have been misled by temporal data coverage being too short.…”

Section: Front Velocities Advance Rate and Surge Terminationsupporting

confidence: 65%

“…In previous studies, up-glacier propagation of velocities and crevasses has been related to up-glacier propagation of the surge (e.g. Meier and Post, 1969;Hodgkins and Dowdeswell, 1994;Murray et al, 2003b;Pritchard et al, 2005). We suggest a different interpretation.…”

Section: Glacier Surface Expressionsmentioning

confidence: 55%

“…For example, several studies have observed surge initiation during winter (e.g. Raymond and Harrison, 1985;Echelmeyer et al, 1987;Osipova and Tsvekov, 1991;Eisen et al, 2005;Pritchard et al, 2005). 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).…”

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: Front Velocities Advance Rate and Surge Terminationsupporting

confidence: 82%

Section: Front Velocities Advance Rate and Surge Terminationsupporting

confidence: 73%

Section: Front Velocities Advance Rate and Surge Terminationsupporting

confidence: 65%

Section: Glacier Surface Expressionsmentioning

confidence: 55%

Section: Introductionmentioning

confidence: 99%

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Surge dynamics in the Nathorstbreen glacier system, Svalbard

2014

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Dynamics of surge‐type glaciers in West Kunlun Shan, Northwestern Tibet

2015

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Here we examine 31 glaciers in the West Kunlun Shan of the northwestern Tibetan Plateau and identify 9 as surge type. The method is based on satellite synthetic aperture radar and Landsat optical images, the former going back to 1992, the latter to 1972. To identify surge-type glaciers, we consider temporal changes in velocity, changes in glacier terminus position, propagation of a surge bulge, presence of looped and/or contoured medial moraines, and extensive crevassing. Other than the nine surge-type glaciers, we identify two that have likely surged, and six that may be surge type. But no glacier surges more than once during the observation period, meaning that the recurrence interval exceeds 42 years. In addition, we examine the evolution of the surface velocities at two surging glaciers with the unprecedented temporal resolution of down to 11 days over ∼7 years. The results show clear seasonal modulations by as much as ∼200% in early winter against those in early summer. This seasonal modulation in surface velocity suggests the presence of surface meltwater that reroutes through the englacial and subglacial drainage systems. Thus, our findings suggest that the hydrological processes originating in the surface meltwater play an important role in maintaining the yearlong active surging phase.

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Glacier crevasses: Observations, models, and mass balance implications

Colgan

Rajaram

Abdalati

et al. 2016

Reviews of Geophysics

160

199

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We review the findings of approximately 60 years of in situ and remote sensing studies of glacier crevasses, as well as the three broad classes of numerical models now employed to simulate crevasse fracture. The relatively new insight that mixed-mode fracture in local stress equilibrium, rather than downstream advection alone, can introduce nontrivial curvature to crevasse geometry may merit the reinterpretation of some key historical observation studies. In the past three decades, there have been tremendous advances in the spatial resolution of satellite imagery, as well as fully automated algorithms capable of tracking crevasse displacements between repeat images. Despite considerable advances in developing fully transient three-dimensional ice flow models over the past two decades, both the zero stress and linear elastic fracture mechanics crevasse models have remained fundamentally unchanged over this time. In the past decade, however, multidimensional and transient formulations of the continuum damage mechanics approach to simulating ice fracture have emerged. The combination of employing damage mechanics to represent slow upstream deterioration of ice strength and fracture mechanics to represent rapid failure at downstream termini holds promise for implementation in large-scale ice sheet models. Finally, given the broad interest in the sea level rise implications of recent and future cryospheric change, we provide a synthesis of 10 mechanisms by which crevasses can influence glacier mass balance. Field ObservationsBy virtue of providing relatively easy access to a glacier's interior, crevasses can be an asset to observational glaciologists, permitting, for example, the efficient examination of glacier stratigraphy. Annual accumulation

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Glacier surge dynamics of Sortebræ, east Greenland, from synthetic aperture radar feature tracking

Cited by 81 publications

References 66 publications

Surge dynamics in the Nathorstbreen glacier system, Svalbard

Surge dynamics in the Nathorstbreen glacier system, Svalbard

Dynamics of surge‐type glaciers in West Kunlun Shan, Northwestern Tibet

Glacier crevasses: Observations, models, and mass balance implications

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