Sustained retreat of the Pine Island Glacier

Park, J. W.; Gourmelen, Noël; Shepherd, A.; Kim, S. W.; Vaughan, David G.; Wingham, D. J.

doi:10.1002/grl.50379

Cited by 123 publications

(158 citation statements)

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“…Starting times of experiments computed by Joughin et al (2010) and Seroussi et al (2014) correspond to the acquisition year of the surface velocities used for inversion, 1996 and 2008, respectively. As detailed in Favier et al (2014), the starting time of their experiments corresponds to the last grounding line measurements available, i.e., completed in 2011 (Park et al, 2013). Cumulated contribution was offset to zero in 2009.…”

Section: Discussionmentioning

confidence: 99%

Reducing uncertainties in projections of Antarctic ice mass loss

Durand

Pattyn

2015

The Cryosphere

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Abstract.Climate model projections are often aggregated into multi-model averages of all models participating in an intercomparison project, such as the Coupled Model Intercomparison Project (CMIP). The "multi-model" approach provides a sensitivity test to the models' structural choices and implicitly assumes that multiple models provide additional and more reliable information than a single model, with higher confidence being placed on results that are common to an ensemble. A first initiative of the ice sheet modeling community, SeaRISE, provided such multi-model average projections of polar ice sheets' contribution to sealevel rise. The SeaRISE Antarctic numerical experiments aggregated results from all models devoid of a priori selection, based on the capacity of such models to represent key ice-dynamical processes. Here, using the experimental setup proposed in SeaRISE, we demonstrate that correctly representing grounding line dynamics is essential to infer future Antarctic mass change. We further illustrate the significant impact on the ensemble mean and deviation of adding one model with a known bias in its ability of modeling grounding line dynamics. We show that this biased model can hardly be identified from the ensemble only based on its estimation of volume change, as ad hoc and untrustworthy parametrizations can force any modeled grounding line to retreat. However, tools are available to test parts of the response of marine ice sheet models to perturbations of climatic and/or oceanic origin (MISMIP, MISMIP3d). Based on recent projections of Pine Island Glacier mass loss, we further show that excluding ice sheet models that do not pass the MISMIP benchmarks decreases the mean contribution and standard deviation of the multi-model ensemble projection by an order of magnitude for that particular drainage basin.

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Section: Discussionmentioning

confidence: 99%

Reducing uncertainties in projections of Antarctic ice mass loss

Durand

Pattyn

2015

The Cryosphere

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“…Corresponding times are indicated by a square and a circle respectively in the upper rows. The thirdbottom row also shows the areas (shaded) separating the GL as observed in 2011 (purple line, [17]) from the relaxed model GLs, which cover 364±50 km 2 , 426±50 km 2 for Elmer/Ice, BISICLES , respectively (not shown for Úa because of the non continuous profile of the GL). The thick grey lines in the top row indicate the same area.…”

Section: Acknowledgmentsmentioning

confidence: 99%

“…The thick grey lines in the top row indicate the same area. The results have been shifted to equal a null contribution at the year 2011 which is also the year of the last measured GL [17]. The corresponding offsets were estimated from the intersection between thick grey lines and changes in grounded areas from the first row in Figure 2.…”

Section: Acknowledgmentsmentioning

confidence: 99%

“…The accelerated thinning observed since the 1980s has essentially been attributed to enhanced sub-ice shelf melting [21] induced by the recent alteration of Circumpolar Deep Water circulation [10]. This has reduced the buttressing exerted by the ice shelf, leading to the acceleration of the ice stream and the ongoing retreat of the grounding line (GL) along the glacier's trunk observed since 1992 [17]. Today the GL lies over bedrock that has a steep retrograde slope [29] (Figure 1c) raising the possibility that PIG may already be engaged in an irrevocable retreat.…”

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confidence: 99%

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Retreat of Pine Island Glacier controlled by marine ice-sheet instability

et al. 2014

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Currently Pine Island Glacier (PIG) is responsible for 20% of the total ice loss offdischarge from the West Antarctic Ice Sheet (WAIS) ([22]; [30]). The accelerated thinning observed since the 1980s has essentially been attributed to enhanced sub-ice shelf melting [21] induced by the recent alteration of Circumpolar Deep Water circulation [10]. This has reduced the buttressing exerted by the ice shelf, leading to the acceleration of the ice stream and the ongoing retreat of the grounding line (GL) along the glacier's trunk observed since 1992 [17]. Today the GL lies over bedrock that has a steep retrograde slope [29] (Figure 1c) raising the possibility that PIG may already be engaged in an irrevocable retreat. ProvidedAssuming that ice flow is dominated * durand@lgge.obs.ujf-grenoble.fr 2 by basal sliding and lateral variation can be ignored, grounding lines located on retrograde slopes are always unstable [24,3], but in realistic, three-dimensional geometries lateral drag and buttressing in the ice shelf can act to prevent unstable retreat [9]. Assessing the stability of PIG therefore requires numerical models that accurately represent these additional forces.Models designed to study the evolution of PIG have been reported, though limited to flowline geometries [7] or extreme forcings [11]. Overall, the short-term behaviour of PIG is not well understood, and projections vary wildly, ranging from modest retreat to almost full collapse of the main trunk within a century [11,7].Here, we evaluate the potential instability of PIG and its short-term contribution to sea-level rise (SLR) using state-of-the-art ice flow models. To decide whether PIG is subject to Marine Ice Sheet Instability (MISI) at present, we must answer two questions: (i) to what extent is the dynamic response of PIG to changes in its ice shelf dictated by the bedrock topography rather than the type and amplitude of the perturbation, and, (ii) can the GL be stabilized on the retrograde slope? Confidence in the answers we propose is of course affected by the accuracy of both the physics implemented in the models that we use and our estimates of poorly constrained parameters. We addressed these questions using three different ice-flow models: the full Stokes For all three models, the geometry is relaxed over 15 years to remove unphysical surface undulations induced by remaining uncertainties in the model initial conditions [6]. Surface accumu-3 lation is given by the regional atmospheric model RACMO (1980RACMO ( -2004) and sub-ice shelf melting is imposed as a piecewise linear function of the lower surface elevationwater depth with a maximum melting rate of 100 m a −1 below -800 m depth, linearly decreasing to no melt above -400 m. This melt-rate parametrisation, which we will refer to as m0 control, is in reason- The recent retreat of PIG is now firmly attributed to acceleration of the glacier in response to sub-ice shelf melting. To evaluate the consequences of melting on PIG dynamics, fivefour different melt-rate perturbations are tested. These ar...

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“…following deglaciation from the LGM (19-23 kyr). According to Larter et al (in press) the rates of change currently observed in the ASE are too high to be a simple continuation of deglaciation from the LGM as such high modern retreat rates (i.e., 0.95 ± 0.09 km yr -1 between 1992-2011; Park et al 2013) would have resulted in deglaciation of the entire continental shelf within 500 years, which is in conflict with recent marine geological data (e.g., Smith et al, 2011). There is also a growing body of geomorphological evidence that ice sheet retreat following the LGM was oscillatory with periods of rapid change punctuated by periods of relative stability (Graham et al, 2010;Jakobsson et al 2011).…”

Section: Introductionmentioning

confidence: 99%