Validation of high-resolution GRACE mascon estimates of glacier mass changes in the St Elias Mountains, Alaska, USA, using aircraft laser altimetry

Arendt, A. A.; Luthcke, S. B.; Larsen, Curtis E.; Abdalati, W.; Krabill, William B.; Beedle, M. J.

doi:10.3189/002214308787780067

Cited by 57 publications

(67 citation statements)

References 48 publications

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“…Vertical accuracy of the surveyed points ranges from ±0.1 m to ±0.3 m and is dependent largely upon the quality of the trajectory solution for the aircraft (position and orientation from GPS and inertial measurement unit onboard the aircraft). To calculate changes in elevation between nadir pointing laser surveys, we followed techniques and error estimations as described by Arendt et al (2008). Calculating elevation changes between nadir laser surveys and LiDAR surveys, and between LiDAR to LiDAR surveys is done by interpolating the later survey onto a 5 m gridded surface, then sampling that surface at the earlier survey's points.…”

Section: Airborne Altimetrymentioning

confidence: 99%

Surge dynamics on Bering Glacier, Alaska, in 2008–2011

et al. 2012

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Abstract.A surge cycle of the Bering Glacier system, Alaska, is examined using observations of surface velocity obtained using synthetic aperture radar (SAR) offset tracking, and elevation data obtained from the University of Alaska Fairbanks LiDAR altimetry program. After 13 yr of quiescence, the Bering Glacier system began to surge in The quiescent phase was characterized by small-scale acceleration events that increased driving stresses up to 70 %. When the surge initiated, synchronous acceleration occurred throughout much of the glacier length. Results suggest that downstream propagation of the surge is closely linked to the evolution of the driving stress during the surge, because driving stress appears to be tied to the amount of resistive stress provided by the bed. In contrast, upstream acceleration and upstream surge propagation is not dependent on driving stress evolution.

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Section: Airborne Altimetrymentioning

confidence: 99%

Surge dynamics on Bering Glacier, Alaska, in 2008–2011

et al. 2012

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“…For example, surge-type glaciers in their quiescent phases can experience thickening in their upper reaches even in the presence of regional glacier mass loss (e.g., Nuth et al, 2010). This complex behaviour of surgetype and tidewater glaciers, often appearing unrelated to prevailing climate, makes projections of glacier change more difficult in areas where these glaciers are found in abundance (e.g., Arendt et al, 2008).…”

Section: G E Flowers Et Al: Present Dynamics and Future Prognosis mentioning

confidence: 99%

Present dynamics and future prognosis of a slowly surging glacier

et al. 2011

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Abstract. Glacier surges are a well-known example of an internal dynamic oscillation whose occurrence is not a direct response to the external climate forcing, but whose character (i.e. period, amplitude, mechanism) may depend on the glacier's environmental or climate setting. We examine the dynamics of a small (∼5 km 2 ) valley glacier in Yukon, Canada, where two previous surges have been photographically documented and an unusually slow surge is currently underway. To characterize the dynamics of the present surge, and to speculate on the future of this glacier, we employ a higher-order flowband model of ice dynamics with a regularized Coulomb-friction sliding law in both diagnostic and prognostic simulations. Diagnostic (force balance) calculations capture the measured ice-surface velocity profile only when non-zero basal water pressures are prescribed over the central region of the glacier, coincident with where evidence of the surge has been identified. This leads to sliding accounting for 50-100% of the total surface motion in this region. Prognostic simulations, where the glacier geometry evolves in response to a prescribed surface mass balance, reveal a significant role played by a bedrock ridge beneath the current equilibrium line of the glacier. Ice thickening occurs above the ridge in our simulations, until the net mass balance reaches sufficiently negative values. We suggest that the bedrock ridge may contribute to the propensity for surges in this glacier by promoting the development of the reservoir area during quiescence, and may permit surges to occur under more negative balance conditions than would otherwise be possible. Collectively, these results corroborate our interpretation of the current glacier flow regime as indicative of a slow surge that has been ongoing for some time, and support a relationship between surge incidence or character and the Correspondence to: G. E. Flowers (gflowers@sfu.ca) net mass balance. Our results also highlight the importance of glacier bed topography in controlling ice dynamics, as observed in many other glacier systems.

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“…1). The St. Elias Mountains are extensively glacierized (Arendt et al, 2008) and have contributed significantly to sea level during the latter half of the 20th century (e.g. Kaser et al, 2006;Berthier et al, 2010).…”

Section: Study Sitementioning

confidence: 99%

A preliminary assessment of glacier melt-model parameter sensitivity and transferability in a dry subarctic environment

2011

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Abstract. Efforts to project the long-term melt of mountain glaciers and ice-caps require that melt models developed and calibrated for well studied locations be transferable over large regions. Here we assess the sensitivity and transferability of parameters within several commonly used melt models for two proximal sites in a dry subarctic environment of northwestern Canada. The models range in complexity from a classical degree-day model to a simplified energybalance model. Parameter sensitivity is first evaluated by tuning the melt models to the output of an energy balance model forced with idealized inputs. This exercise allows us to explore parameter sensitivity both to glacier geometric attributes and surface characteristics, as well as to meteorological conditions. We then investigate the effect of model tuning with different statistics, including a weighted coefficient of determination (wR 2 ), the Nash-Sutcliffe efficiency criterion (E), mean absolute error (MAE) and root mean squared error (RMSE). Finally we examine model parameter transferability between two neighbouring glaciers over two melt seasons using mass balance data collected in the St. Elias Mountains of the southwest Yukon. The temperature-index model parameters appear generally sensitive to glacier aspect, mean surface elevation, albedo, wind speed, mean annual temperature and temperature lapse rate. The simplified energy balance model parameters are sensitive primarily to snow albedo. Model tuning with E, MAE and RMSE produces similar, or in some cases identical, parameter values. In twelve tests of spatial and/or temporal parameter transferability, the results with the lowest RMSE values with respect to ablation stake measurements were achieved twice with a Correspondence to: G. E. Flowers (gflowers@sfu.ca) classical temperature-index (degree-day) model, three times with a temperature-index model in which the melt parameter is a function of potential radiation, and seven times with a simplified energy-balance model. A full energy-balance model produced better results than the other models in nine of twelve cases, though the tuning of this model differs from that of the others.

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Validation of high-resolution GRACE mascon estimates of glacier mass changes in the St Elias Mountains, Alaska, USA, using aircraft laser altimetry

Cited by 57 publications

References 48 publications

Surge dynamics on Bering Glacier, Alaska, in 2008–2011

Surge dynamics on Bering Glacier, Alaska, in 2008–2011

Present dynamics and future prognosis of a slowly surging glacier

A preliminary assessment of glacier melt-model parameter sensitivity and transferability in a dry subarctic environment

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