Roles of marine ice, rheology, and fracture in the flow and stability of the Brunt/Stancomb‐Wills Ice Shelf

Khazendar, A.; Rignot, Eric; Larour, Eric

doi:10.1029/2008jf001124

Cited by 84 publications

(149 citation statements)

References 57 publications

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“…The two models of Humbert and others (2009) differed however in a number of technical details, but these differences did not affect the results significantly. Similar to Khazendar andothers (2009), andothers (2014), Humbert and others (2009) stressed the importance of the highly heterogeneous structure of the BIS and the SWGT for ice flow.…”

Section: Past Studies Of Ice Flowmentioning

confidence: 95%

Five decades of strong temporal variability in the flow of Brunt Ice Shelf, Antarctica

Gudmundsson¹,

Rydt²,

Nägler

2016

J. Glaciol.

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ABSTRACT. Data showing velocity changes on the Brunt Ice Shelf (BIS), Antarctica, over the last 55 years are presented and analysed. During this period no large-scale calving events took place and the ice shelf gradually grew in size. Ice flow velocities, however, fluctuated greatly, increasing twofold between 1970 and 2000, then decreasing again to previous levels by 2012 after which velocities started to increase yet again. In the observational period, velocity changes in the order of 10% a −1 have commonly been observed, and currently velocities are increasing at this rate. By modelling the ice flow numerically, we explore potential causes for the observed changes in velocity. We find that a loss of mechanical contact between the BIS and the McDonald Ice Rumples following a local calving event in 1971 would explain both the increase and the subsequent decrease in ice velocities. Other explanations involving enlargement of observed rift structures are discounted as the effects on ice flow are found to be too small and the spatial pattern of velocity change inconsistent with data. The most recent phase of acceleration remains unexplained but may potentially be related to a recent re-activation of a known rift structure within the BIS.

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Section: Past Studies Of Ice Flowmentioning

confidence: 95%

Five decades of strong temporal variability in the flow of Brunt Ice Shelf, Antarctica

Gudmundsson¹,

Rydt²,

Nägler

2016

J. Glaciol.

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“…[14] In order to determine a, we rely on inverse methods, which have been extensively documented in MacAyeal [1992,1993], Rommelaere and MacAyeal [1997], Larour et al [2005], Vieli et al [2006], Khazendar et al [2007Khazendar et al [ , 2009, Larour et al [2012b], and Morlighem et al [2010]. A significant difference between our approach and the latter studies is that we invert a in steady state mode, similar to Morlighem et al [2010].…”

Section: Modelmentioning

confidence: 99%

An improved method for estimating water-mass ventilation age from radiocarbon data

DeVries

Primeau

2010

Earth and Planetary Science Letters

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[1] Model projections of ice flow in a changing climate are dependent on model inputs such as surface elevation, bedrock position or surface temperatures, among others. Of all these inputs, geothermal heat flux is the one for which uncertainty is greatest. In the area of Pine Island Glacier, Antarctica, available data sets differ by up to a factor of 2.5. Here, we evaluate the impact of such uncertainty on ice flow, using sampling analyses based on the Latin-Hypercube method. First, we quantify the impact of geothermal heat flux errors on ice hardness, a thermal parameter that critically controls the magnitude of ice flow. Second, we quantify the impact of the same errors on mass balance, specifically on the mass flux advecting through thirteen fluxgates distributed across Pine Island Glacier. We contrast our results with similar uncertainties generated by errors in the specification of ice thickness. Model outputs indicate that geothermal heat flux errors yield uncertainties on ice hardness on the order of 5-7%, with maximum uncertainty reaching 15%. Resulting uncertainties in mass balance remain however below 1%. We discuss the uncertainty distribution and its relationship to the amount of heat available at the base of the ice sheet from friction, viscous and geothermal heating. We also show that comparatively, errors in ice thickness contribute more to model uncertainty than errors in geothermal heat flux, especially for fast-flowing ice streams.

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“…A common approach in the cryosphere community to obtain gradients of forward models has been to rely on the adjoint method (MacAyeal, 1993;Rommelaere andMacAyeal, 1997 Vieli andPayne, 2003;Joughin et al, 2004b;Larour et al, 2005;Vieli et al, 2006;Khazendar et al, 2007Khazendar et al, , 2009Morlighem et al, 2010;Arthern and Gudmundsson, 2010). The approach consists in analytically deriving the adjoint state of the forward model, which allows for an easy computation of the The Cryosphere, 8, 2335-2351, 2014…”

Section: Algorithmic Differentiation Of the Gradient Of Jmentioning

confidence: 99%

Inferred basal friction and surface mass balance of the Northeast Greenland Ice Stream using data assimilation of ICESat (Ice Cloud and land Elevation Satellite) surface altimetry and ISSM (Ice Sheet System Model)

et al. 2014

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Abstract. We present a new data assimilation method within the Ice Sheet System Model (ISSM) framework that is capable of assimilating surface altimetry data from missions such as ICESat (Ice Cloud and land Elevation Satellite) into reconstructions of transient ice flow. The new method relies on algorithmic differentiation to compute gradients of objective functions with respect to model forcings. It is applied to the Northeast Greenland Ice Stream, where surface mass balance and basal friction forcings are temporally inverted, resulting in adjusted modeled surface heights that best fit existing altimetry. This new approach allows for a better quantification of basal and surface processes and a better understanding of the physical processes currently missing in transient ice-flow models to better capture the important intra-and interannual variability in surface altimetry. It also demonstrates that large spatial and temporal variability is required in model forcings such as surface mass balance and basal friction, variability that can only be explained by including more complex processes such as snowpack compaction at the surface and basal hydrology at the bottom of the ice sheet. This approach is indeed a first step towards assimilating the wealth of high spatial resolution altimetry data available from EnviSat, ICESat, Operation IceBridge and CryoSat-2, and that which will be available in the near future with the launch of ICESat-2.

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Roles of marine ice, rheology, and fracture in the flow and stability of the Brunt/Stancomb‐Wills Ice Shelf

Cited by 84 publications

References 57 publications

Five decades of strong temporal variability in the flow of Brunt Ice Shelf, Antarctica

Five decades of strong temporal variability in the flow of Brunt Ice Shelf, Antarctica

An improved method for estimating water-mass ventilation age from radiocarbon data

Inferred basal friction and surface mass balance of the Northeast Greenland Ice Stream using data assimilation of ICESat (Ice Cloud and land Elevation Satellite) surface altimetry and ISSM (Ice Sheet System Model)

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