Modeling the Response of Lambert Glacier–Amery Ice Shelf System, East Antarctic, to Uncertain Climate Forcing Over the 21St and 22Ndy

Open Access ciently high melt Discussions ffi The Cryosphere cient thinning of the ice shelf ffi ect the global sea level (van den ff 3 5684 5683 for 2000–2011 (Shepherd et al., 2012). These con- 1 − , and A. J. Payne 3 ect an ice sheet by altering its mass balance directly through ff , S. L. Cornford 1,2 This discussion paper is/has beenPlease under refer review to for the the corresponding journal final The paper Cryosphere in (TC). TC if available. School of Earth Sciences, UniversityArctic of Centre, Bristol, Lapland Bristol, University, UK Rovaniemi, Finland School of Geographical Sciences, University of Bristol, Bristol, UK Broeke et al., 2009):Antarctica the is rate of about sea-level 0.25 mmyr rise due to the present-day mass loss from surface accumulation and melting,ice or shelf/ocean indirectly interface through and meltingden the and Broeke consequential refreezing et dynamic on al., thickening 2009; the the and Williams et retreat thinning al., and (van 2001; disintegration Huybrechtstica of and Peninsula ice de Wolde, as shelves 1999). well in Soobserved the as far in west some Pine and of Island east theing Glacier coast (Scambos most are of et dramatic associated the al., thinning Antarc- 2000; with2002). and Skvarca Mass atmospheric elevation et change and changes al., over oceanic 1999; the warm- Joughin ice et sheet al., will 2003; in Shepherd turn et a al., is negative. 1 Introduction Climate change can a by surface accumulation and basalsphere melt models. The rates change computed of byinfluenced by the two the ice ocean basal thickness and melting and distribution, twoof velocity but, the atmo- although simulations, in the there the is ice ice little shelfgrounding shelf line grounding thins can line in is retreat retreat. the mainly as We most much findsouth as that of 30 the km Clemence Lambert if Massif, Glacier there butrates is none su in of that the region. ocean Overall, modelsmodels the provide outweighs increased su ice accumulation stream computed acceleration by so the that atmosphere the net contribution to sea level rise The interaction between thea climate key system process in and global theof environmental large one change. polar We of carried the ice out largest sheetsIce ice drainage Shelf regions dynamic systems system, simulations is with in an East adaptive Antarctica: mesh ice the sheet Lambert model. Glacier–Amery The ice sheet model is driven Abstract Modeling the response of Lambert Glacier–Amery Ice Shelf system, East Antarctic, to uncertain climate forcing over the 21st and 22ndY. centuries Gong 1 2 3 Received: 23 October 2013 – Accepted: 31Correspondence October to: 2013 A. – J. Published: Payne 2 ([email protected]) DecemberPublished 2013 by Copernicus Publications on behalf of the European Geosciences Union. The Cryosphere Discuss., 7, 5683–5709,www.the-cryosphere-discuss.net/7/5683/2013/ 2013 doi:10.5194/tcd-7-5683-2013 © Author(s) 2013. CC Attribution 3.0 License. 5 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent climate ff ) leaves the ice shelf through 1 − 6.9 Gtyr ± 5686 5685 ering roles of SMB , basal melt rate and the topographic fea- ff Comparing the di tures on the dynamics of the LG-AIS system; Investigating the dynamic changes ofchange, the ice LG-AIS velocity system change includingforcing; and ice grounding thickness line migration under di Estimating the responses oftribution the to changes the of global the sea LG-AIS level. system, namely its con- Through the model simulation three specific subjects have been looked at in order to The ice sheet model used in this study employs adaptive mesh refinement (AMR) A set of previously published surface mass balance (SMB) and basal melt rate cal- (2) the Clemence Massif (Hambrey and Dowdeswell, 1994), whichThe is AIS an has elongated, long been considered a stable ice shelf that is currently undergoing In this study, we carried out dynamic simulations of the Lambert Glacier–Amery Ice AIS has a relatively narrow shape comparing to the Ross Ice Shelf and the Ronne– (1) the Prince Charles Mountains in the west and Mawson Escarpment, Manning As one of the largest ice drainage systems in Antarctic (Rignot and Thomas, 2002) 3. 1. 2. centuries. They are: resolution is unnecessary. As theGL resolution (Cornford of et the al., mesh 2012), evolves thisand with model dynamic time is thinning to well follow in suited the the to studying region grounding of line the migration Ameryassess Ice the Shelf. responses of LG-AIS system to uncertain climate forcing in 21st and 22nd et al., 2012),Timmermann and et two al., ocean 2002; TimmermannSMB models, and and BRIOS Helmer, basal 2013), melt and are rateby chosen FESOM respectively. They two to are Global (Beckmann provide driven Climate the et Models by (GCMs), theby al., HadCM3 boundary Green and 1999; data House ECHAM5 computed Gases which are (GHG) in Emission turn Scenarios driven E1 orto A1B. obtain a non-uniformas mesh grounding that line has and fast finer flowing spatial ice resolution stream where exist dynamics and such coarser resolution where fine one is the issue ofthe migration whether of the the ice grounding sheet line model (GL) can and properly the fast captureculations flow the were of character employed the of as icespheric climate across Models, the forcing LMDZ4 GL. in and this RACMO2 study. (Agosta, Two 2012; higher Agosta resolution et atmo- al., 2012; Ligtenberg dynamic simulations (Payne et al., 2013). One is the input climatic forcing; the other Shelf (LG-AIS) system. Two factors govern the results of the projection when doing mostly ice-free massif located at the south-eastern part ofa the natural ice shelf. advance–calve–advance cyclemass (Fricker et balance al., (Wen 2002a, etpropagation b). al., process Observations 2006, on of its 2008; its iceet Yu front et al., (Larour 2007) al., et support 2010) al., thathas 2004; and hypothesis. Bassis But large model the et uncertainties studies future al., under state 2005; ofperhaps of the MacAyeal throw the the influence light whole rift of on drainage the global system future warming of and the model ice studies shelf and can its adjacent glaciers. tic coastline (Budd et al.,ics 1966). of Several AIS topographic including: features characterize the dynam- Nunataks and Reinbolt Hills in the east, which provide large lateral drag; tem is thought to beet in al., balance 2006, or 2008; positive Yu etbeneath imbalance al., by resulting 2010). numerous in The observations Amery complex (Wen 2012). Ice patterns In Shelf total, interacts of 50 with % melting the ofbasal and ocean the melting cavity mass refreezing (Wen (around (Galton-Fenzi 46.4 et et al.,northern al., 2010), edge (Yu with et the al., remainder 2010). lost though calvingFilchner events Ice at Shelf the and its ice shelf front only accounts for 1.7 % of the total East Antarc- ice sheets and their response to future climate forcing. the Lambert Glacier–Amery Ice Shelfing (LG-AIS) the system plays future a responses crucialof of role the in East grounded determin- Antarctica East to Antarctica (Fricker climate et change al., 2000). as The it grounded drains portion about of 16 the % sys- cerns the application of numerical models that attempt to simulate the current state of 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | er- ff , decomposed 0 b required to keep M 0 s cient field, along with M ffi ective viscosity. The ice cient and enhancement ff ffi . 0 b M toolkit, to maintain fine resolution and 10, 5, or 2.5 km (a 3-level mesh) and ++ 0 s = M ∂x 5688 5687 10, 5, 2.5, or 1.25 km have both applied in this study. = ∂x With the type of optimization we used we find high-frequency variation in the ice To initialize the model, we need to provide a basal friction coe Ice thickness and bedrock topography data are drawn from the 5 km ALBMAP DEM distributed over grounded ice.a However, warming the or water cooling temperature trend beneath depending AIS on exhibits the model. The BRIOS-HadCM3-E1 com- perturbations described in the next section to 2.2 Climate forcing Table 1 shows the time-and-spaceperature for averaged each SMB atmospheric and forcing,oceanic mean and the forcing. annual melt The surface rate air surface andbinations temperature tem- water show temperature outputs for increasing obtained the by trends,bination. all especially Most of that of the of the forcing the com- SMB LMDZ4-HadCM3-A1B values com- increase slightly, with positive and growing SMB the grounded ice in steadyinto state, ambient and and a near spatiallyto smoothed grounding melt line steady rate components, state. which WeThe will then resulting keep run ice the the ice sheetprojections shelf model state starting close is for from closer 50 yr this to, state, starting but with again not SMB at, from and equilibrium, the melt and initial rates we state. computed carry by out adding all the thinning (or thickening) rate,other which sources are of assumedet error to al., in be 2011), the artefacts orobserved. of mismatch ice So between interpolation sheet before the carrying and geometry out timefor all at (Morlighem a the period which targeted et with the experiments a al., we geometry presentis run day 2011; and (relax) carried forcing velocity to Seroussi the out bring were model it inRACMO/HadCM3/E1 closer data, two to and a stages. steady-state. the First The sub-shelfin relaxation we melt steady set rate is state. the chosen After SMB to to 50 keep yr, the the we ice 2000–2009 shelf compute mean an from accumulation the rate ence between the magnitude ofobservations modelled acquired velocity during and the velocityshows data year the taken 2007 observed from to InSAR ice 2009elled velocity (Rignot velocity of et at the the al., LG-AIS start 2011a). system, of Figure while the 2a Fig. simulation. 2b shows the mod- Joughin et al. (2009) and Morlighem et al. (2010) which seeks to minimise the di model constructed by Pattynfactor (2010). are The calculated basal by friction an coe optimization method similar to that of MacAyeal (1992), BEDMAP datasets but more data havebathymetry been underneath provided ice in shelves. ALBMAP The data icethrough thickness sets, data especially incorporation of of grounded ice the isdata produced original (Vaughan BEDMAP et ice al.,hydrostatic thickness assumption 2006; and from Holt the surface elevations. AGASEA/BBAS et al., 2006). Thetemperature ice and shelf enhancement factor thickness fieldstemperature is profile to is derived compute provided the by by a e three-dimensional thermo-mechanical higher-order (Le Brocq et al.,Mosaic 2010). of The Antarctic basic (MOA)2007). mask coastline Modifications for shape have the files been whole made (Haranbine Antarctic to et the the is al., grounded grounding obtained 2005; line ice2001), from Scambos in with sheet, the et the order ice which al., to shelf. smoothly is The com- basal largely topography and from marine BEDMAP bathymetry is datasets based (Lythe on the et al., grated model based on Schooflateral and strains and Hindmarsh, a 2010, simplified which treatmentshelves of includes and vertical longitudinal shear fast and strain, floating and ice isrefinement best streams. (AMR), suited It to supported ice makes by usealong the of the Chombo block-structured grounding C adaptive line mesh et and al., in 2000). ice Meshes stream, havinga and grid set coarser cells of resolution 4-level with elsewhere meshesA with (Colella 2-level mesh covering the AIS region is shown in Fig. 1. 2.1 Ice sheet model The comprehensive description of thein BISICLES this adaptive study mesh can ice be found sheet in model Cornford used et al. (2012). BISICLES employs a vertically inte- 2 Methodology 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ) ). ◦ 1 − , the 0 0.35 S − erences be- 625 m) to as- ff = for WC-BRI and and the changes 1 − 0 ∂x s M and 0 b M in a portion of the ice shelf, ef- 1 a region north of a line (shown in − 5 S erent accumulation and melting – 1 ff S 5690 5689 ) and the smallest averaged basal melt rate (23.77 Gtyr 1 − ). Most of the melt rate data exhibit a positive trend during the simulation for WC-FES). The Best Case (BC) simulation has the largest averaged ◦ ) and the largest averaged basal melt rate (229.43 Gtyr 1 1 − ect of the resolution on the grounding line migration. The di − ff 1.78 − inputs All simulations we carried out on both 3-level and 4-level refined meshes, and se- In the extreme simulations, intended to investigate the stability of the southern SMB and melt rates have been selected to drive 5 basic simulation cases (Ta- converge into the icethickness shelf of and the downstream entire to ice Clemence shelf Massif thickens decreases most. in The WC-FES and WC-FES-Melt most sig- well as the controlthe run shelf are is determined showncontrol by in run, the Fig. and ocean 3. model, the Unsurprisingly,simulations with combined the show the cases pattern SMB thinning resembling of only those insouthern cases thinning with the part resembling in no northern the except SMB part for anomaly.WC-BRI All WC-FES of simulations the (and the (corresponding WC-FES-Melt) ice toconcentrated and the shelf along N1 E1 and the (and climate thickening north-east400 N1-Melt). m in scenario), and In thinning the high north-west the there, melt-rates of while are the the region shelf, where leading the to Fisher, more Mellor than and Lambert Glaciers 3 Results and discussion 3.1 The response of LG-AIS system to di The ice thickness changes of the LG-AIS system of all climate-driven simulations as entire ice shelf isFig. 2b) removed disappears. while in cases lected simulations on 5-level refinedsess meshes the (with e finest resolution tween simulations due to mesh resolution are no more than 12 % of mass imbalance. constant forcing to quantify the model’s drift (no anomalies aregrounding applied). line, we setfectively removing the that melt part rateulations of the to from shelf 1980 1000 entirely myr to within 2220. a few In years the and most run extreme these sim- case, sensitive experiment fect equilibrium even without climate perturbations, we also carry out a control run with models are not in close agreement for the 1980s. As the model ice sheet is not in per- ulations (Table 2). In normalried simulations, 14 out climate-driven by simulations applying have climateto been forcing 2220 car- as or anomalies 2100 againstto (the the 2100). forcing 1980–1990 In provided average other run byclimate words combinations before we contain the assume ECHAM5 1990s,SMB that are as and AIS only suggested melt was up rate by approximately from Rignotcomputed in the et by sum balance the al. of with climate (2011b), thecause the equilibrium models. and the rates We construct ice need both sheet torespect model run to state our any described of simulations in the this Sect. climate 2.1 way models firstly is around not be- 1980 near and to secondly equilibrium because with the climate to the ice sheet model as anomalies relative to2.3 their 1980–1989 temporal Experiment mean. In this study, we categorised the simulations into normal simulations and extreme sim- (51.12 Gtyr 221.77 Gtyr SMB value (137.05 Gtyr Two neutral cases (N1and and averaged melting N2) data have arerate also close outputs. been to In the chosen addition, meanWC-Melt, whose the values BC-SMB, among averaged cases all BC-Melt, SMB with the N1-SMB, data onlyout SMB N1-Melt, SMB to and or investigate N2-SMB melt the melt and influences rate N2-Melt) separately. anomalies All were the (WC-SMB, carried data of those 14 cases are applied beneath Amery Ice Shelf,coldest and ( that given byperiod the except FESOM-ECHAM5-E1 for BRIOS-HadCM3-A1B combination and is BRIOS-HadCM3-E1. ble 1). Two Worst Case (WC) simulations have the smallest averaged SMB value bination has a temporal and spatial averaged warmest water temperature ( 5 5 20 25 15 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent ff and WC-FES cases. The ects of the SMB inputs are 0 ff S , which melts the ice shelf right at 3 S ) of the ice shelf the final southern GL 1 S 5 km) among all the simulation cases. 5692 5691 > simulation are shown in Fig. 5. The ice shelf does 0 S case. N1 cases accelerate downstream the most significantly as 0 S The results of the retreat distance of the southern and western GL are shown in Ta- The southern GL of all the normal simulations except for WC-FES and WC-FES- In theory, the thinning of the ice shelf would cause buttressing loss which would According to Yu et al. (2010), the melt rate of AIS decreases rapidly from the ground- From the results above, it can be concluded that the e The ice velocity along A-Aitof all climate-driven simulations in the final simulation Through comparison between the GL migration of ing providing we didextents. sensitivity tests by removing the iceble 3. shelf By stepwise removing the toinland entire ice di which shelf, is the relatively grounding smallIsland line comparing has area to retreated (retreats for the just for removalto 30.5 150 of km km) some the (Payne entire point et ice approximatelyremains al., shelf in in 2013). at the Pine When the middle we ( advance. same remove By the position ice removing as shelf the the ice initial shelf year, gradually namely further the inland GL the neither GL retreat start nor to retreat. cause immediately acceleration and thinningand of the the GL ice sheet retreatHowever, (Dupont might even and the be Alley, two 2005) expected WC in meltthe response only assumption to cases that buttressing do the not losecertain GL give (Rignot, topographic noticeable migration 2002). features GL of and retreat. Amery its It narrow Ice raises shape. Shelf In is order more to investigate complicated the due buttress- to No significant migrations can bethe control found run. in the results of all the normalMelt simulations have and advanced (lessgone than through 5 dramatic km) thinning. evenin The though some GL in simulations of retreats certain the duringWC-BRI-Melt cases Charybdis the are simulation the Glacial the period. ice basin most The significant (western shelf retreats ( GL) of has WC-BRI and The distances of theshape GL of migration GL of is irregular allof we one simulations have are point only displayed along roughlycontrol in considered the run the is Table GL 3. shown largest before in distance As Fig. and change 6a. the after The GL the changes migration of other happen. normal The simulations are GL similar. change of 3.2 Grounding line migration actly, which would cause large uncertainties to the projection of the LG-AIS system. pattern of velocity andshelf ice thickens thickness and can accelerates also in the bethat front found the at in ice the N1 end shelf of andthe actually the N1-Melt basal gains simulation that as accumulation mass the it only from can ice thicken. starts be beneath seen at after the about northern 2090 part when (Fig. the 4). iceing And shelf zone also to starts the icestream to shelf section. front From and preliminary significantmelt studies basal rate refreezing (only distribution is three of detected results all in the are the model shown down- combinations in have Fig. matched 4), the no observation ex- The melting of thebetween the former southern is grounding distributed zonelater and is throughout distributed Clemence the mainly Massif, at entire in theues contrast, northern ice along which part the shelf of of northeast and the the andhas ice is northwest shelf given and edge. larger a has The corresponding slightly melting distribution larger distribution, val- of to thickness some change extent, (Fig. 3). An odd changing velocity of the WC-FEShalf cases of that that is of southalmost the the of entire Clemence ice Massif shelf increases thickens in to the around end ofminor the comparing simulation. to thatBesides, of the basal distribution melt of melt rateseen rate in from seems terms Figs. as 3 of important and thickness asdramatic 5 the and that than total both velocity WC-BRI amount. thickness change. though It and they velocity can have changes be of similar WC-FES amount are of more melt rate in total (Table 1). thickens in N1 (andshelf N1-Melt) produced due by to BRIOS the with A1B re-freezing scenario under (Fig. the 4). northernyear as portion well of as the not the accelerate control south and of Clemence Massif except for the nificantly to the south of the Clemence Massif. In contrast, almost the entire ice shelf 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 3 km 3 10 × 5.7 mm SLR) − ( 3 10 km) much as in km > 3 10 × 5694 5693 Positive SMB, increasing Tamean (Table 1) and 1 − the significance of Clemence Massif for the buttressing 4 ) does the southern GL retreat dramatically ( 4 The authors would like to thank Daniel F. Martin for his contributions to (1.0 mm SLR) by the end of the simulation. The majority of the remaining ce of Science, Advanced Scientific Computing Research and Biological and En- erent combinations of SMB and melt rate inputs provided by several cli- 3 ff ffi km 3 simulation (Fig. 5). 10 0 S × 2.7 mm SLR). VAF increases in all but the WC-FES and WC-FES-Melt simulations. Almost all the simulations show a decrease of the global sea level at the end of the The retreat of the western GL is rather limited by the topography that even removing Therefore, we suggest that the buttressing for the grounded ice in the southern basin modelling of thecenturies. Antarctic Paper surface presented mass atenne, balance, Autriche, European application 2013. Geosciences for Union the General 20th, Assembly 21st 2013, and Vi- 22nd conséquences sur les variations du niveau des mers, Université de Grenoble, 2012. − grounded ice. The groundingbasal line migration melting. is Grounding more lineMassif sensitive retreat to are noticeably the greater only distribution than ifVAF of change 1000 melt the myr (Fig. rates 7) south maycontributor of suggest to Clemence that the global the sea LG-AISthe level system relationship rise is between in unlikely surface the to warmingLG-AIS future become system even and under a needs the warm further big quantity climate. investigation. and However distribution of SMB in We have presented the modellingdriven results by of di Lambert Glacier–Amerymate Ice models. Shelf The system iceby thickness basal and melt rates velocity rather of than Amery SMB as Ice the Shelf majority is of the influenced positive mainly SMB located on the 4 Conclusions by 1.01 mm) case. 0.4 simulations show a positive changein in the VAF: best as case much (BC, as BC-SMB) 2.2 simulations. simulation (Table 3).The results2.79 of mm. the And the control steepestglobal run sea falling may level is by lower given 5.58 the mm bysea at global BC level the sea and rising end BC-SMB level of are 2100. that by the The will WC-FES only decrease simulations (increase the that by cause 1.01 global mm) and WC-FES-Melt (increase The evolution of the volumeAIS of system, ice above which flotation isNote (VAF) integrated directly that over the related the control entire toflux run LG- global is data, sea not as in level( steady change, described state is because in shown of Sect.In in the these Fig. smoothing 2.1, worst-case of 7. so simulations, the VAF mass that reaches model a peak drift – amounts around to 2125, then 1.1 drops, by sif may be alsodistance magnified between as the AIS two isproviding sides. needs confined The further between role investigation. high the mountains Clemence with Massif a played narrow the in entire buttressing section in front of it does not3.3 cause retreat larger The than contribution 10 of km. Amery Ice Shelf to the global sea level of the grounded ice canClemence be Massif found. (S Only whenthe the ice shelf is removed right behind the is largely provided by Clemence Massif. And the buttressing provided by a single mas- the Clemence Massif, and S Agosta, C., Favier, V., Krinner, G., Gallée, H, Fettweis, X., and Genthon, C.: High-resolution Agosta, C.: Evolution du bilan de masse de surface antarctique par regionalization physique et References Acknowledgements. the BISICLES code. BISICLES isCalifornia, jointly USA developed and at the Lawrenceentific Berkeley University Discovery National of through Laboratory, Bristol, Advancedof UK Computing Energy, with (SciDAC) O program financial funded supportvironmental by provided Research US through and Department Sci- theCentre UK for Natural Science Environment Research Ltd,simulations. Council. 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B.: Partitioning recent Greenland mass loss, melting in the 21st andOcean 22nd Dyn., centuries accepted, based 2013. on coupled ice-ocean finite element modelling, BRIOS-HadCM3-A1B (N1) 2000–2199 Melt Rate 130.54 ModelLMDZ4-HadCM3-A1B (BC) 2000–2199 SMB Period 137.05 Parameter 123.19 Temporal 13.84 Temporal Temporal Trend (LA) 0.2746 Trend (GI) Trend (FI) 0.2673 0.0074 LMDZ4-HadCM3-E1LMDZ4-ECHAM5-E1 (N2) 2000–2199 2000–2099 SMB SMB 121.10 111.82 105.30 95.66 15.78 16.14 0.0549 0.0558 BRIOS-HadCM3-E1(WC-BRI) 2000–2199 Melt Rate 229.43 RACMO-HadCM3-A1B (N1)RACMO-HadCM3-E1 (WC)RACMO-ECHAM5-A1BRACMO-ECHAM5-E1 2000–2199 2000–2199 SMB 2000–2099 SMB 2000–2099 SMB 57.98 SMB 51.12 53.57 56.72 47.20 4.40 52.97 51.45 3.91 0.0937 48.19 5.25 0.0279 0.0876 4.77 0.0244 0.0770 0.0061 0.0588 0.0035 0.0744 0.0528 0.0026 0.0588 BRIOS-ECHAM5-A1BBRIOS-ECHAM5-E1 (N2)FESOM-HadCM3-A1B(WC-FES) 2000–2199 2000–2099FESOM-ECHAM5-A1B 2000–2199 Melt Rate MeltFESOM-ECHAM5-E1 Rate (BC) Melt Rate 2000–2099 2000–2199 Melt Rate Melt Rate 221.77 71.93 64.00 25.07 23.78 2.4314 0.8309 0.3655 0.0766 0.0248 Table 1. outputs time series. Yu, J., Liu, H., Jezek, K. C., Warner, R. C., and Wen, J.: Analysis of velocity field, mass Wen, J., Wang, Y., Wang, W., Jezek, K. C.,Williams, Liu, M. H., and J. M., Allison, I.: Grosfeld, Basal K., melting Warner, and R. freezing C., Gerdes, R., and Determann, J.: Ocean circu- Wen, J., Wang, Y., Liu, J., Jezek, K. C., Huybrechts, P., Csatho, B. M., Farness, P., and Sun, B.: Wen, J., Jezek, K. C., Monaghan, A. J., Sun, B., Ren, J., and Huybrechts, P.:Accumulation vari- Velicogna, I.: Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets Vaughan, D. G., Corr, H. F. J., Ferraccioli, F., Frearson, N., O’Hare, A., Mach, D., Holt, J., van den Broeke, M. R., Bamber, J., Ettema, J., Rignot, E., Schrama, E., van de Berg, W. J., Timmermann, R., Hellmer, H. H., and Beckmann, A.: Simulations of ice-ocean dynamics in Timmermann, R. and Helmer, H. H.: Southern Ocean warming and increased ice shelf basal 5 30 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Period 2.79 1.52 1.52 2.79 5.58 2.03 5.32 6.59 2.53 6.84 2.54 1.78 2.28 − − − − − − − − − − − − − beneath the 1 ) Change − 3 km 3 0.40 1.01 0.30 1.01 3.30 8.36 10 − − − × Amery-balance-meltAmery-balance-melt 1980–2220 Amery-balance-melt 1980–2220 Amery-balance-melt 1980–2220 Amery-balance-melt 1980–2220 1980–2220 + + + + + )( 3 km 6 \\\ \\\ \\\ \\\ \\\ 10 × )( SMB Data Basal Melting Data Simulation 3 km 6 10 × 5702 5701 ))))) Amery-balance-SMB Amery-balance-SMB 1000 Amery-balance-SMB 1000 Amery-balance-SMB 1000 Amery-balance-SMB 1000 1000 1 2 3 4 5 S S S S S 5.3 2.8902 2.8908 0.60 2.5 2.8902 2.8898 6.3 2.8902 2.8908 0.60 2.5 2.8903 2.8900 2.5 2.8902 2.8928 2.60 2.5 2.8902 2.8912 1.00 2.5 2.8902 2.8912 1.00 2.5 2.8902 2.8909 0.70 7.6 2.8901 7.6 2.8901 7.6 2.8901 7.6 2.8901 7.6 2.8901 9.5 2.8901 2.8868 − − − − − − − − − − − − − − Best Case (BC) LMDZ4-HadCM3-A1B FESOM-ECHAM5-E1 1980–2100 Neutral Case 1 (N1)Neutral Case 2 (N2) RACMO-HadCM3-A1B LMDZ4-ECHAM5-E1 BRIOS-HadCM3-A1B BRIOS-ECHAM5-E1 1980–2220 1980–2100 Sensitive Test 2 ( Sensitive Test 3 ( Sensitive Test 4 ( Sensitive Test 5 ( Sensitive Test 1 ( Best Case Melt only (BC-melt) FESOM-ECHAM5-E1 1980–2100 Best Case SMB only (BC-SMB) LMDZ4-HadCM3-A1B 1980–2220 Worst Case SMB only (WC-SMB) RACMO-HadCM3-E1 1980–2220 Neutral Case 1 Melt onlyNeutral (N1-melt) Case 2 Melt only (N2-melt) BRIOS-HadCM3-A1B BRIOS-ECHAM5-E1 1980–2220 1980–2100 Neutral Case 1 SMB onlyNeutral (N1-SMB) Case 2 SMB only (N2-SMB) RACMO-HadCM3-A1B LMDZ4-ECHAM5-E1 1980–2220 1980–2100 6.3 3.8 2.5 2.5 16.3 21.3 32.5 (km) (km) (mm) − − − − − − − Worst Case-BRIOS Melt only (WC-BRI-melt) BRIOS-HadCM3-E1 1980–2220 Worst Case-FESOM Melt only (WC-FES-melt) FESOM-HadCM3-A1B 1980–2220 southern western ( Summaries of GL change and VAF change of each simulation case. Climate-DrivenSimulation Worst Case-BRIOS (WC-BRI) Worst Case-FESOM (WC-FES) RACMO-HadCM3-E1 RACMO-HadCM3-E1 BRIOS-HadCM3-E1 FESOM-HadCM3-A1B 1980–2220 1980–2220 Simulation combinations selected from the outputs of the RCMs and simulation period Experiment G.L. advance G.L.Control advance Initial VAF Final VAF VAF Gain 5 Sea level 0 2.8902 2.8913 1.10 WC-BRI 5 WC-FES WC-BRI-melt 2.5 WC-FES-melt WC-SMB 5 0 2.8902 2.8913 1.10 BC 2.5 0 2.8902 2.8924 2.20 BC-melt 2.5 0 2.8902 2.8910 0.80 BC-SMB 5 0 2.8902 2.8923 2.10 N1 2.5 N1-melt 5 N1-SMB 5 0 2.8902 2.8929 2.70 N2 2.5 N2-melt 2.5 N2-SMB 5 0 2.8902 2.8911 0.90 Sensitive test 1Sensitive test 2 0 Sensitive test 3 Sensitive test 4 Sensitive test 5 Sensitive test 0 Extreme Remove-ice shelf Amery-balance-SMB 1000 1980–2220 NormalSimulation Control Simulation Control Amery-balance-SMB Amery-balance-melt 1980–2220 Table 3. part that needs tothe be ice removes shelf. and remain the steady state melt rate beneath the rest part of Table 2. used in model study. The melt rate of Sensitive test 1–5 are set to be 1000 myr 1

Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2 ） b （ Observational ve- (a) 1 5704 5703 ） a ) along which the ice thickness and ice velocity are 0 （ 2 Modeled velocity constrained using control method to match the observational (b) The mesh in AIS region of a 2 level refinement. The finest solution (625 km) follows the Comparison between observational velocity and modeled velocity. grounding line. compared are presented on the map. Fig. 1. locity map obtained by multipleet satellites al., InSAR 2011). acquired duringvelocity the map. year 2007 The to longitudinal 2009 profile (Rignot (A–A Fig. 2.

(A) WC-BRI-SMB BC-SMB N1-SMB N2-SMB 0 1200 -1200 i 4 5706 5705 3 WC-FESWC-FES-Melt Control WC-BRIWC-BRI-Melt BC BC-Melt N1 N1-Melt N2 N2-Melt

The ice thickness changes of the Amery Ice Shelf at the end of the simulations. For N2, The temporal mean basal melt rate from 1980 to 2200 of Fig. 4. N1. Fig. 3. N2-Melt, N2-SMB and BC,other BC-Melt, simulation BC-SMB, cases, the the ﬁnal ﬁnalSMB simulation input. simulation year The year is plots 2200. are WC-FES WC-FESto and 2100. and WC-FES-Melt legend And refer WC-BRI ii. to for have legend the the i same and the rest of the plots refer

6 Distance along transects (km) Distance along 1982 221 1982 2218 2218 2100 2218 200 300 500 0 100 400 0 100 400 0 0 0 200 600 400 500 200 800

600 400

1000 1600 2500 2000 1500 1000 erent simulation cases in di

1400 1200

800

1000 1600

1400 1200

WC WC-BRI-Melt

Velocity (m/yr) Velocity Velocity (m/yr) Velocity

Velocity (m/yr) Velocity ﬀ 0 Control WC-BRIControl WC-FES BC N1 S WC-SMB BC-SMB N1- SMB

simulation. 4 C D A B S

Grounding line migration of the AIS in Ice velocity of di (left 2 columns). The year of the simulations are marked above the plots. All the normal (D) 0 tion, Fig. 6. Fig. 5. simulations have the same initialN2-SMB position and (in BC, BC-Melt, the BC-SMB, yearulation the 1982) cases, final the with simulation final control year simulation run. are year For is 2100. N2, 2200. And N2-Melt, for the other sim- A–A Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 2200 2160 2120 2080 5709 erent simulation cases. The legend can be found in 2040 ff 2000 05

2.8910

2.8900 2.89 2.8895 2.8935 2.8930 2.8925 2.8920 2.8915 10 x ( n o i otat l F bove ) A e m u l o V m k

6 3 The ice mass changes of the LG-AIS system over simulation period expressed as VAF. erent curves show the results of di ﬀ Fig. 4. Di Fig. 7.