Ice Flow of the Antarctic Ice Sheet

Rignot, Eric; Mouginot, J.; Scheuchl, B.

doi:10.1126/science.1208336

Cited by 1,085 publications

(1,408 citation statements)

References 31 publications

(7 reference statements)

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“…We applied both SAR interferometry (InSAR) (Goldstein et al, 1993;Joughin et al, 1996) as well as the SAR offsettracking method (Strozzi et al, 2002;Rignot et al, 2011;Paul et al, 2013) in order to estimate glacier velocities. The InSAR method measures displacement in the radar line-ofsight (LOS) direction, with a precision of the order of millimetres to centimetres, while offset tracking provides information about azimuth and range surface displacements, with a precision of the order of decimetres to metres.…”

Section: Velocity Measurementsmentioning

confidence: 99%

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: Velocity Measurementsmentioning

confidence: 99%

Surge dynamics in the Nathorstbreen glacier system, Svalbard

2014

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“…1). This floating platform has been relatively stable in recent decades, with different behaviours of the GLZ and very small net mass balance changes (Rignot et al, 2011b). The relative stability of the RnIS is partly explained by the Weddell Seas oceanographic and atmospheric conditions, and the associated broad extent of sea ice (Mayewski et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Recent ice dynamic and surface mass balance of Union Glacier in the West Antarctic Ice Sheet

et al. 2014

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Abstract.Here we present the results of a comprehensive glaciological investigation of Union Glacier (79°46 S/83°24 W) in the West Antarctic Ice Sheet (WAIS), a major outlet glacier within the Ellsworth Mountains. Union Glacier flows into the Ronne Ice Shelf, where recent models have indicated the potential for significant grounding line zone (GLZ) migrations in response to changing climate and ocean conditions. To elaborate a glaciological base line that can help to evaluate the potential impact of this GLZ change scenario, we installed an array of stakes on Union Glacier in 2007. The stake network has been surveyed repeatedly for elevation, velocity, and net surface mass balance. The region of the stake measurements is in near-equilibrium, and ice speeds are 10 to 33 m a −1 . Ground-penetrating radars (GPR) have been used to map the subglacial topography, internal structure, and crevasse frequency and depth along surveyed tracks in the stake site area. The bedrock in this area has a minimum elevation of −858 m a.s.l., significantly deeper than shown by BEDMAP2 data. However, between this deeper area and the local GLZ, there is a threshold where the subglacial topography shows a maximum altitude of 190 m. This subglacial condition implies that an upstream migration of the GLZ will not have strong effects on Union Glacier until it passes beyond this shallow ice pinning point.

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“…The measurement errors for these observations are usually small: for instance for the DEM (digital elevation model) of Antarctica, 42 % of the map has an RMS smaller than 2 m, but RMS can be up to 130 m in mountainous regions; see Griggs and Bamber (2009). Ice velocity is obtained by radar interferometry and maps are available over the major part of both ice sheets with a kilometric resolution (Rignot et al, 2011 for Antarctica, Joughin et al, 2010 for Greenland). The uncertainty ranges from 1 to 17 m per year (Rignot et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Ice velocity is obtained by radar interferometry and maps are available over the major part of both ice sheets with a kilometric resolution (Rignot et al, 2011 for Antarctica, Joughin et al, 2010 for Greenland). The uncertainty ranges from 1 to 17 m per year (Rignot et al, 2011). Beside satellite observations, there are also localised measurements of the bedrock topography generally obtained by radar measurements from planes and thus restricted to flight lines.…”

Section: Introductionmentioning

confidence: 99%

An ETKF approach for initial state and parameter estimation in ice sheet modelling

Bonan

Nodet

Ritz

et al. 2014

Nonlin. Processes Geophys.

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Abstract. Estimating the contribution of Antarctica andGreenland to sea-level rise is a hot topic in glaciology. Good estimates rely on our ability to run a precisely calibrated ice sheet evolution model starting from a reliable initial state. Data assimilation aims to provide an answer to this problem by combining the model equations with observations. In this paper we aim to study a state-of-the-art ensemble Kalman filter (ETKF) to address this problem. This method is implemented and validated in the twin experiments framework for a shallow ice flowline model of ice dynamics. The results are very encouraging, as they show a good convergence of the ETKF (with localisation and inflation), even for small-sized ensembles.

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Ice Flow of the Antarctic Ice Sheet

Abstract: A high-resolution map of ice motion in Antarctica shows the details of ice movement in a warming climate.

Cited by 1,085 publications

References 31 publications

Surge dynamics in the Nathorstbreen glacier system, Svalbard

Surge dynamics in the Nathorstbreen glacier system, Svalbard

Recent ice dynamic and surface mass balance of Union Glacier in the West Antarctic Ice Sheet

An ETKF approach for initial state and parameter estimation in ice sheet modelling

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