Understanding ice-sheet mass balance: progress in satellite altimetry and gravimetry

Pritchard, Hamish D.; Luthcke, S. B.; Fleming, Andrew

doi:10.3189/002214311796406194

Cited by 21 publications

(16 citation statements)

References 50 publications

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“…The events after the collapse of the Larsen A and B ice shelves show this clearly; substantial speed-up of parts of glaciers adjacent to the grounding line was observed almost instantly upon ice-shelf collapse (Rignot et al 2004; Scambos et al 2004) and spread upstream over the following years (Rott et al 2002; Pritchard et al 2011), associated with strong thinning. There are now a large number of similar examples, e.g.…”

Section: Introductionmentioning

confidence: 92%

Frequency response of ice streams

2012

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Changes at the grounding line of ice streams have consequences for inland ice dynamics and hence sea level. Despite substantial evidence documenting upstream propagation of frontal change, the mechanisms by which these changes are transmitted inland are not well understood. In this vein, the frequency response of an idealized ice stream to periodic forcing in the downstream strain rate is examined for basally and laterally resisted ice streams using a one-dimensional, linearized membrane stress approximation. This reveals two distinct behavioural branches, which we find to correspond to different mechanisms of upstream velocity and thickness propagation, depending on the forcing frequency. At low frequencies (centennial to millennial periods), slope and thickness covary hundreds of kilometres inland, and the shallow-ice approximation is sufficient to explain upstream propagation, which occurs through changes in grounding-line flow and geometry. At high frequencies (decadal to sub-decadal periods), penetration distances are tens of kilometres; while velocity adjusts rapidly to such forcing, thickness varies little and upstream propagation occurs through the direct transmission of membrane stresses. Propagation properties vary significantly between 29 Antarctic ice streams considered. A square-wave function in frontal stress is explored by summing frequency solutions, simulating some aspects of the dynamical response to sudden ice-shelf change.

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Section: Introductionmentioning

confidence: 92%

Frequency response of ice streams

2012

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“…By sampling the GrPGICs in addition to the GrIS, GRACE-derived mass loss estimates can be expected to have ∼ 35 Gt a −1 greater mass loss than volumetric or input-output methods that only sample the ice sheet proper (cf. Alley et al, 2007;Pritchard et al, 2010). While GRACE implicitly samples the mass changes associated with GrPGICs, whether or not these other methods include GrPGICs is dependent on the ice mask employed, which can vary tremendously from study to study (Vernon et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

Constraining GRACE-derived cryosphere-attributed signal to irregularly shaped ice-covered areas

Colgan¹,

Luthcke²,

Abdalati³

et al. 2013

Preprint

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We use a Monte Carlo approach to invert a spherical harmonic representation of cryosphere-attributed mass change in order to infer the most likely underlying mass changes within irregularly shaped ice-covered areas at nominal 26 km resolution. By inverting a spherical harmonic representation through the incorporation of additional fractional ice coverage information, this approach seeks to eliminate signal leakage between non- and ice-covered areas. The spherical harmonic representation suggests a Greenland mass loss of 251 ± 25 Gt yr⁻¹ over the December 2003 to December 2010 period. The inversion suggests 218 ± 20 Gt yr⁻¹ was due to the ice sheet proper, and 34 ± 5 Gt yr⁻¹ (or ~ 14%) was due to Greenland peripheral glaciers and ice caps (GrPGIC). This mass loss from GrPGIC exceeds that inferred from all ice masses on both Ellesmere and Devon Islands combined. This partition therefore highlights that GRACE-derived "Greenland" mass loss cannot be taken as synonymous with "Greenland ice sheet" mass loss when making comparisons with estimates of ice sheet mass balance derived from techniques that only sample the ice sheet proper

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“…An important design objective of ICESat was to measure ice sheet surface elevation change over regions of high surface slope and complex topography, with primary mission objectives to measure spatially-averaged (104 km 2 ) ice sheet surface elevation to <15 cm absolute accuracy and elevation change to <1.5 cm yr −1 accuracy [36,101]. Field validation suggests operational absolute accuracy achieved 2 ± 3 cm for optimal conditions [164].…”

Section: Laser Altimetry Sensors Methods and Datasetsmentioning

confidence: 99%

“…At the ice-sheet scale, knowledge of snow, firn, and ice density is the main source of uncertainty for conversion between ice sheet volume change and mass change [36]. Density changes are caused by snow and firn compaction and by meltwater refreezing, which both affect waveform interpretation by changing the scattering properties of the snow and firn [105,116].…”

Section: Current Challenges and Future Opportunitiesmentioning

confidence: 99%

Satellite Remote Sensing of the Greenland Ice Sheet Ablation Zone: A Review

Cooper

Smith

2019

Remote Sensing

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The Greenland Ice Sheet is now the largest land ice contributor to global sea level rise, largely driven by increased surface meltwater runoff from the ablation zone, i.e., areas of the ice sheet where annual mass losses exceed gains. This small but critically important area of the ice sheet has expanded in size by~50% since the early 1960s, and satellite remote sensing is a powerful tool for monitoring the physical processes that influence its surface mass balance. This review synthesizes key remote sensing methods and scientific findings from satellite remote sensing of the Greenland Ice Sheet ablation zone, covering progress in (1) radar altimetry, (2) laser (lidar) altimetry, (3) gravimetry, (4) multispectral optical imagery, and (5) microwave and thermal imagery. Physical characteristics and quantities examined include surface elevation change, gravimetric mass balance, reflectance, albedo, and mapping of surface melt extent and glaciological facies and zones. The review concludes that future progress will benefit most from methods that combine multi-sensor, multi-wavelength, and cross-platform datasets designed to discriminate the widely varying surface processes in the ablation zone. Specific examples include fusing laser altimetry, radar altimetry, and optical stereophotogrammetry to enhance spatial measurement density, cross-validate surface elevation change, and diagnose radar elevation bias; employing dual-frequency radar, microwave scatterometry, or combining radar and laser altimetry to map seasonal snow depth; fusing optical imagery, radar imagery, and microwave scatterometry to discriminate between snow, liquid water, refrozen meltwater, and bare ice near the equilibrium line altitude; combining optical reflectance with laser altimetry to map supraglacial lake, stream, and crevasse bathymetry; and monitoring the inland migration of snowlines, surface melt extent, and supraglacial hydrologic features.

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Understanding ice-sheet mass balance: progress in satellite altimetry and gravimetry

Cited by 21 publications

References 50 publications

Frequency response of ice streams

Frequency response of ice streams

Constraining GRACE-derived cryosphere-attributed signal to irregularly shaped ice-covered areas

Satellite Remote Sensing of the Greenland Ice Sheet Ablation Zone: A Review

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