Calving speed of Alaska tidewater glaciers, with application to Columbia Glacier

Brown, C. S.; Meier, Mark F.; Post, Austin

doi:10.3133/pp1258c

Cited by 198 publications

(243 citation statements)

References 11 publications

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“…In addition, the detailed modeling shows that the stress peak at the glacier surface moves upstream for lowering water level A higher relative water level results in a more stable calving front (as emphasized by Bassis and Walker, 2012) which seems to be in contrast with the often-used relations which predict that calving rates increase with water depth (Brown et al, 1982;Meier and Post, 1987;Hanson and Hooke, 2000). In nature, however, glaciers terminating in deeper waters are also thicker and calve at higher rates as they experience higher absolute (unscaled) stresses.…”

mentioning

confidence: 70%

“…A simple empirical relationship of linearly increasing calving rate with water depth, based on observations of tidewater glaciers in Alaska, has been established, used and extended for different regions (Brown et al, 1982;Benn et al, 2007b). This 30 approach depends on the local water depth at the terminus only and is not process-based, and therefore independent of glacier geometry and dynamics (Vieli et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

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Calving relation for tidewater glaciers based on detailed stress field analysis

Mercenier¹,

Lüthi²,

Vieli³

2017

Preprint

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Abstract. Ocean terminating glaciers in Arctic regions have undergone rapid dynamic changes in recent years, which have been related to a dramatic increase in calving rates. Iceberg calving is a dynamical process strongly influenced by the geometry at the terminus of tidewater glaciers. We investigate the effect of varying water level, calving front slope and basal sliding on the stress state and flow regime for an idealized grounded ocean-terminating glacier and scale these results with ice thickness and velocity. Results show that water depth and calving front slope strongly affect the stress state while the effect from variations in 5 basal sliding is much smaller. An increased relative water level or a reclining calving front slope strongly decrease the stresses and velocities in the vicinity of the terminus and hence have a stabilizing effect on the calving front. We find that surface stress magnitude and distribution are determined by solely the water depth relative to ice thickness for simple geometries. Based on this scaled relationship for the stress peak at the surface, and assuming a critical stress for damage initiation, we propose a simple and new parametrization for calving rates for grounded tidewater glaciers that is in good agreement with observations.

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mentioning

confidence: 70%

Section: Introductionmentioning

confidence: 99%

Calving relation for tidewater glaciers based on detailed stress field analysis

Mercenier¹,

Lüthi²,

Vieli³

2017

Preprint

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“…Calving is accomodated using an empirical function related to water depth (Brown et al, 1982), which although simplistic compared to more complex relationships (e.g. Benn et al, 2007a,b), does at least offer a reasonable approximation of calving loss with minimal computation.…”

Section: Methodsmentioning

confidence: 99%

High-resolution numerical simulation of Younger Dryas glaciation in Scotland

Golledge

Hubbard

Sugden

2008

Quaternary Science Reviews

116

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We use a 500 m resolution three-dimensional thermomechanical ice -sheet model forced by a scaled GRIP temperature pattern to retrodict the extent of glaciers during the Younger Dryas episode in Scotland. Using empirical data from sources spanning half a century we systematically perturb temperature depression, precipitation distribution, and the amount of basal sliding to identify the parameter space that most closely reproduces the glacier margins identified from field investigations. Arithmetic comparison of predicted ice cover with empirical glacier extent enables mismatch to be quantified and an 'optimum fit' timeslice to be identified. This 'best-fit' scenario occurs with a maximum mean annual temperature depression from present of 10 C and steep eastward and northward gradients imposed on a modern precipitation distribution, coupled with restricted basal sliding. Even small deviations around these values produce considerably less well-fitting glacier configurations, suggesting that only a narrow range of optimal parameterisation exists. Mismatch between modelled and empirically reconstructed glacier extents occurs as a consequence of local conditions not accommodated by the model, such as wind-blown snow accumulation and lake (loch) bathymetry, and where geological evidence is equivocal. At the domain scale, however, our simulation suggests that inception of Scottish glaciers occurs rapidly, and leads to a coherent ice cap within 400 years of initial climatic cooling. According to our model, the ice cap begins to decay relatively early in the stadial, probably as a result of increasing aridity leading to net thinning and recession of many of its margins, with final and catastrophic collapse of the ice cap occurring largely within a century.

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“…For the inner fjord basin, the up-glacier borehole was drilled through the ice reaching the bed at an (2012) bed model and surface elevation fields. The 265 resulting estimates of ice flux through the calving front are then smoothed at annual time steps using a nonparametric kernel-smoothing filter (Bowman and Azzalini, 1997). We use a 3 a window sampled on 15 June each year, when the seasonal variation is near its average value.…”

Section: Implications For Glacial Erosion and The Subglacial Storage mentioning

confidence: 99%

Observations and modeling of fjord sedimentation during the 30 year retreat of Columbia Glacier, AK

et al. 2016

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ABSTRACT. To explore links between glacier dynamics, sediment yields and the accumulation of glacial sediments in a temperate setting, we use extensive glaciological observations for Columbia Glacier, Alaska, and new oceanographic data from the fjord exposed during its retreat. High-resolution seismic data indicate that 3.2 × 10 8 m 3 of sediment has accumulated in Columbia Fjord over the past three decades, which corresponds to ∼5 mm a −1 of erosion averaged over the glaciated area. We develop a general model to infer the sediment-flux history from the glacier that is compatible with the observed retreat history, and the thickness and architecture of the fjord sediment deposits. Results reveal a fivefold increase in sediment flux from 1997 to 2000, which is not correlated with concurrent changes in ice flux or retreat rate. We suggest the flux increase resulted from an increase in the sediment transport capacity of the subglacial hydraulic system due to the retreat-related steepening of the glacier surface over a known subglacial deep basin. Because variations in subglacial sediment storage can impact glacial sediment flux, in addition to changes in climate, erosion rate and glacier dynamics, the interpretation of climatic changes based on the sediment record is more complex than generally assumed.

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Calving speed of Alaska tidewater glaciers, with application to Columbia Glacier

Abstract: Highest altitude a t which thinning occurred m Dimensions depend on form of the calving relation.

Cited by 198 publications

References 11 publications

Calving relation for tidewater glaciers based on detailed stress field analysis

Calving relation for tidewater glaciers based on detailed stress field analysis

High-resolution numerical simulation of Younger Dryas glaciation in Scotland

Observations and modeling of fjord sedimentation during the 30 year retreat of Columbia Glacier, AK

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