In uence of West Antarctic Ice Sheet collapse on Antarctic

GEOPHYSICAL RESEARCH LETTERS, VOL. ???, XXXX, DOI:10.1002/,

1

2

Influence of West Antarctic Ice Sheet collapse on

Antarctic surface climate and ice core records

Eric J. Steig,1,2

Kathleen Huybers,3

Hansi A. Singh,2

Nathan J. Steiger,2

Qinghua Ding,4

Dargan M.W. Frierson,2, Trevor Popp

5, James W.C. White

6

Corresponding author: Eric J. Steig, Department of Earth and Space Sciences, University of

Washington, Seattle, Washington 98195, USA. ([email protected])

1Department of Earth and Space Sciences, University of Washington, Seattle, WA, USA.

2Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA.

3Department of Geosciences, Pacific Lutheran University, Tacoma, WA, USA.

4Polar Science Center, Applied Physics Laboratory, University of Washington, Seattle, WA, USA.

5Centre for Ice and Climate, Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark.

6Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO, USA.

D R A F T March 25, 2015, 10:32am D R A F T

X - 2 STEIG ET AL.: CLIMATE RESPONSE TO WAIS COLLAPSE

Abstract. Climate-model simulations are used to examine the impact of3

a collapse of the West Antarctic Ice Sheet (WAIS) on the surface climate of4

Antarctica. The lowered topography following WAIS collapse produces anomalous5

cyclonic circulation with increased flow of warm, maritime air towards the6

South Pole, and cold-air advection from the East Antarctic plateau towards7

the Ross Sea and Marie Byrd Land, West Antarctica. Relative to the background8

climate, some areas in the East Antarctic interior warm moderately, while9

substantial cooling (several ◦C) occurs over parts of West Antarctica. Anomalously10

low isotope-paleotemperature values at Mt. Moulton, West Antarctica, compared11

with ice core records in East Antarctica, are consistent with collapse of the12

WAIS during the last interglacial period, Marine Isotope Stage (MIS) 5e. More13

definitive evidence might be recoverable from an ice core record at Hercules14

Dome, East Antarctica, which would experience significant warming and oxygen-isotope15

anomalies if the WAIS collapsed.16


STEIG ET AL.: CLIMATE RESPONSE TO WAIS COLLAPSE X - 3

1. Introduction

Sea level records provide indirect evidence that the West Antarctic Ice Sheet (WAIS)17

collapsed during the last interglacial period, Marine Isotope Stage (MIS) 5e, ∼130 to18

116 ka (thousands of years before present). Eustatic sea level was 4 to 6 meters higher19

than present, possibly more [Dutton and Lambeck , 2012]. Mass loss from the Greenland20

ice sheet is thought to have contributed about 2 m of that total [NEEM Community21

Members , 2013]. Full retreat (“collapse”) of the WAIS would produce about 3.3 m of sea22

level rise [Bamber et al., 2009], which could account for the balance of MIS 5e sea level23

rise. Sediment cores from beneath the WAIS [Scherer et al., 1998] and the present-day24

Ross Ice Shelf [Naish et al., 2009] provide more direct evidence of WAIS collapse, several25

times in the past few million years, but it remains equivocal whether WAIS collapsed26

during MIS 5e.27

In this paper, we evaluate whether collapse of the WAIS, if it occurred, would have28

caused regional climate changes sufficiently large to be detectable in ice core records,29

several of which extend to MIS 5e. The idea of using ice core records to determine ice sheet30

changes has been exploited previously, chiefly under the assumption of a fixed climate,31

with elevation change expressed through the lapse-rate effect on temperature and on the32

stable-isotope ratios in precipitation [Steig et al., 2001; Bradley et al., 2013]. Here, we33

consider changes in regional climate induced by a reduced WAIS topograpy. We evaluate34

the influence of WAIS collapse on atmospheric circulation and temperature using general35

circulation model (GCM) experiments at varying levels of complexity. We compare our36

results with existing ice core records that extend through MIS 5e.37



2. Methods

2.1. Climate Model Experiments

We compare GCM control simulations using modern Antarctic topography, with38

“WAIS-collapse” simulations, in which the Antarctic topography is reduced. In all39

experiments, climate boundary conditions (greenhouse gases, orbital configuration) are40

set to preindustrial values and are not changed. The surface characteristics (e.g. albedo)41

are unchanged in all areas between the full modern topgraphy and the altered topography42

that simulates WAIS collapse. The ice shelves are unchanged.43

We conducted aquaplanet simulations with the Gray Radiation Moist (GRaM) GCM44

[Frierson et al., 2006], and the Geophyical Fluid Dynamics Laboratory Atmospheric Model45

2 (AM2) [GFDL, 2004], in which the only topography is a “water mountain” having the46

shape of Antarctica. Both are coupled to a shallow (2.4 m) slab ocean and have no seasonal47

cycle. In GRaM, radiative fluxes are functions of temperature alone; there is a convective48

scheme but no cloud parameterization. In AM2, there are more complete radiation and49

convection schemes and the model includes cloud and water-vapor feedbacks. GRaM was50

run at T85 (spatial resolution of ∼ 1.4◦), with 25 vertical levels, AM2 at 2◦ latitude x 2.5 ◦51

longitude with 24 vertical levels. In the WAIS-collapse simulations with these models, all52

elevations in West Antarctica were reduced to zero elevation; topographic features such53

as mountains are not retained. We use the last 5 years of 15-year simulations.54

55 We also conducted simulations with the ECHAM4.6 atmospheric model [Roeckner et al.,

1996] at T42 ( ∼2.5◦ ) with 19 vertical levels coupled to a slab ocean with thermodynamic56

sea ice. We included the ECHAM4.6 isotope module [Hoffmann et al., 1998] to obtain57

simulations of changes in the oxygen isotope ratios in precipitation. We use the final58



30 years of 40-year-long simulations. In these experiments, we use global topography,59

and realistic topographic changes in Antarctica. The “WAIS-collapse” topography is60

given by the ice-sheet model simulations of Pollard and DeConto [2009], as shown in61

Fig. 1. The model topography accounts for isostatic adjustment to ice thickness changes.62

Major topographic features such as Hercules Dome and the mountain ranges of coastal63

Marie Byrd Land do not change elevation, though moderate (50–100 m) lowering occurs64

as an artifact of the smoothing of the high-resolution topography to match the GCM65

resolution. There are elevation changes in the major East Antarctic drainage basins66

with reductions of more than 100 m extending well inland.67

Finally, we used the fully coupled ocean-atmosphere GCM, Community Climate System68

Model version 4 [CCSM4, Gent et al., 2011], with the same topography as for the69

ECHAM4.6 experiments, at a land/atmosphere resolution of 1.9◦ x 2.5◦ with 26 vertical70

levels and an ocean resolution of 1◦; the sea ice is fully dynamic. The WAIS-collapse71

simulation was branched from the control simulation at year 700, and run for an additional72

230 years; the climatology of the final 30 years is compared to that of the control.73

2.2. Ice Core Data

We restrict our analysis of ice core data to the conventional stable isotope ratio of74

oxygen (δ18O) in the ice, a well-established proxy for temperature, facilitating comparison75

with the climate model output. Isotope-ratio records that include MIS 5e are currently76

available at six locations in East Antarctica (Fig. 1): at Dome C [EDC, Jouzel et al.,77

2007], Taylor Dome [Steig et al., 2000], Talos Dome [Stenni et al., 2011], Vostok [Jouzel78

et al., 1993], Dronning Maud Land [EDML, EPICA Community Members , 2006] and79



Dome F [Watanabe et al., 2003] and one in West Antarctica, at Mount Moulton, Marie80

Byrd Land [Dunbar et al., 2008; Korotkikh et al., 2011]. We also discuss Hercules Dome in81

East Antarctica. Hercules Dome is of interest because it is close to West Antarctica, and82

owing to the bounding bedrock topography, would have remained at a similar elevation83

and ice thickness even if WAIS collapsed [Jacobel et al., 2005]. Only a shallow (72-m)84

ice core has been recovered from Hercules Dome but radar profiles indicate that ice from85

MIS 5e may be recoverable there [Jacobel et al., 2005]. Locations are shown in Fig. 1,86

and isotope records in Fig. S1 in the supporting information.87

The Mt. Moulton record is the only currently-available West Antarctic record that88

includes MIS 5e. It is not strictly an ice “core” record; it was developed from a transect89

along an exposed section on the southern shoulder of Mt. Moulton, in the Flood Range90

of Marie Byrd Land, where ice flow brings old ice to the surface. The exposed section is91

at ∼76◦S, 134.7◦W, at an elevation of 2820 m above sea level. The Mt. Moulton record92

was dated radiometrically by a series of volcanic tephra layers that span the ∼600 m long93

exposed section [Dunbar et al., 2008; Korotkikh et al., 2011]. The isotope data we use here94

are from the Ph.D. thesis of Popp [2008].95

We are specifically interested in the differences among the ice core δ18O records during96

MIS 5e. To minimize artifacts arising from errors in the ice core age vs. depth97

relationships, we use the common AICC2012 timescale [Veres et al., 2013; Bazin et al.,98

2013], and adjust the preliminary timescale [Popp, 2008] of the Mt. Moulton record by99

maximizing its correlation with EPICA Dome C record (Fig. S2). This adjustment is100

conservative with respect to the calculations we make when comparing the records.101



3. Results

Fig. 2 shows the temperature and potential-temperature response of the climate models102

to the changed Antarctic topography, as compared to the climatology from the control103

runs. The largest temperature increases occur in areas with reduced elevation, but there is104

also substantial warming over areas of East Antarctica where the topography is unchanged.105

In all model experiments there is warming over parts of the East Antarctic ice sheet areas106

adjacent to West Antarctica, including Hercules Dome and coastal Dronning Maud Land107

(though not extending as far inland as the EDML ice core site). There is also cooling108

over parts of East Antarctica and significant cooling in West Antarctica along the Siple109

Coast (eastern Ross Sea), and either cooling or no warming in coastal Marie Byrd Land.110

In the experiments with ECHAM4.6 and CCSM4, there are also areas of greater warming111

in East Antarctica corresponding to, and upslope from, the areas of reduced topography112

in the major ice drainage basins there. Temperature changes off the Antarctic continent113

vary, but all models agree in showing warming over the Ronne-Filchner Ice Shelf and the114

South Atlantic sector of the Southern Ocean. The spatial pattern of the δ18O response is115

very similar to the temperature response (Fig. S3).116

Fig. 3 shows the response of the surface wind field to the changed topography. All117

the models show the same pattern, with increased cyclonic flow over areas where the118

topography is lower. There is commonality between the patterns of wind and temperature119

anomalies, with greater onshore flow towards areas of West Antarctica and East Antarctica120

that warm, and greater flow off of the East Antarctic continent towards the Ross Sea and121

Marie Byrd Land – both areas that cool. Changes in the large scale circumpolar winds122



are less consistent between the models, and in all cases these changes are small compared123

with those over the West Antarctic region and adjacent areas of East Antarctica.124

Fig. 4 compares the δ18O record from Mt. Moulton with the average of the East125

Antarctic records (excluding the low-resolution Taylor Dome record), normalized to the126

peak warmth (maximum δ18O values) of the early Holocene. The Mt. Moulton record127

is distinctive in having a smaller maximum in δ18O during MIS 5e. This difference is128

significant (more than 2 standard deviations below the mean) for most of MIS 5e.129

4. Discussion

4.1. Climate Dynamics

The large scale wind and temperature changes over West Antarctica can be understood130

as consequences of relatively simple dynamics. The cyclonic circulation anomaly over131

West Antarctica that occurs when the topography is lowered would be expected from132

potential vorticity conservation, in that stretching of the air column requires that it spin133

up in the same direction as the planetary vorticity, i.e. cyclonically. James [1988] showed134

that linear, barotropic dynamics causes an anticyclonic anomaly over topography when135

an idealized Antarctic-like continent is added in a barotropic model; thus, removal of136

the topography causes a cyclonic anomaly. Watterson and James [1992] found further137

support for this purely dynamical mechanism in a primitive equation model. Parish and138

Cassano [2003] show that there is little sensitivity of the winds to strong longwave cooling139

of the continent, implying that the katabatic component of the observed large-scale winds140

is weak. These considerations explain why all four models show such similar responses to141

the removal of topography, despite quite different model details.142



Adiabatic warming would be expected as a direct response to the thicker atmosphere143

where the topography is lowered. The changed atmospheric circulation then accounts144

for the warming observed over the Ronne-Filchner Ice Shelf and the Atlantic sector of145

the Southern Ocean, as well as areas of the ice sheet where the topography has not146

changed, including along coastal Dronning Maud Land, and in the vicinity of Hercules147

Dome towards the South Pole from West Antarctica. Cooling over the Ross Sea and148

towards coastal areas of Marie Byrd Land reflects advection of cold-air anomalies from149

the East Antarctic plateau. The importance of advection in explaining the temperature150

pattern is particularly evident in the potential temperature (Fig. 2); if the warming were151

strictly adiabatic, there would be no changes in potential temperature.152

The more variable response of the models over the Southern Ocean and most of East153

Antarctica suggests that the direct effects of WAIS collapse on climate over most of East154

Antarctica and the Southern Ocean are small, relative to other processes and feedbacks.155

In the aquaplanet experiments, large areas over the Southern Ocean cool, while in the156

fully coupled-results with CCSM4, warming occurs over nearly the entire Southern Ocean.157

The latter can be attributed to dynamical changes in the ocean due to wind forcing, as has158

also been observed in a recent WAIS-collapse experiment with a coarse-resolution fully159

coupled model [Justino et al., 2015], though we note that there is also warming over much160

of the Southern Ocean in the slab-ocean experiment with ECHAM4.6. Meltwater fluxes161

– not considered in our experiments – may play a role in the ocean circulation response162

to a real WAIS collapse [Holden et al., 2010], but this would not alter the fundamental163

atmospheric response.164



Other changes in climate boundary conditions that might be associated with WAIS165

collapse could potentially influence our results. In particular, we assumed that the166

albedo does not change where the WAIS has been removed; in reality the land ice167

and ice shelves might be replaced by ocean water that could be partly free of sea ice168

in summer. The difference, however, is evidently not large: Otto-Bliesner et al. [2013]169

conducted a similar fully-coupled experiment to ours (though with simpler topography)170

using CCSM3, in which they replaced WAIS land ice and ice shelves with ocean, and used171

130 ka boundary conditions. Their results show the same pattern of potential temperature172

and winds changes (Fig. S4). We conclude that cooling along the mountains of Marie173

Byrd Land, relative to the background climate state, as well as the advection of warm174

anomalies towards adjacent areas of East Antarctica, are fundamental features of the175

climate response to a collapse of the WAIS.176

4.2. Ice Core Interpretation

Our results have important implications for the interpretation of ice-core paleotemperature177

records. Popp [2008] presaged our results by suggesting that the comparatively low δ18O178

values for MIS 5e in the Mt. Moulton record from coastal Marie Byrd Land could179

180

181

182

183

be explained by altered atmospheric circulation owing to lowered elevations over the

WAIS. Our results clearly support this idea. Given a characteristic scaling of δ18O with

temperature of ∼ 0.8h/◦C [e.g., Steig et al., 2013], the relatively small δ18O anomaly at

Mt. Moulton, about 1–2 h less than in the East Antarctic ice cores, is in good agreement

with the temperature and δ18O anomalies from the GCM experiments.184



The distinctive character of the Mt. Moulton isotope record supports other, independent185

evidence of WAIS collapse during MIS 5e, but there are some caveats to this interpretation.186

The Mt. Moulton record has not only relatively low δ18O values during MIS 5e; it also has187

relatively high δ18O during the coldest part of the glacial period (∼20–40ka) compared188

with other records (Fig. S1). From our model results, elevated δ18O at Mt. Moulton189

might be expected if the WAIS were thicker than present, but evidence for a substantially190

thicker WAIS is equivocal [e.g., Steig et al., 2001]. Furthermore other changes associated191

with MIS 5e climate that are not considered here, including more modest changes in192

WAIS – short of a full “collapse” – may perhaps be sufficient to give rise to the anomalies193

observed.194

These caveats notwithstanding, δ18O records from the East Antarctic ice cores may195

provide indirect supporting evidence for the interpretation of the Mt. Moulton data in196

terms of WAIS collapse. Comparison of the model results for surface temperature with197

ice core δ18O implicitly assumes a fixed linear relationship between the two, whereas the198

significant circulation changes associated with WAIS-collapse may lead to non-linearities199

in the isotope-temperature relationship. Sime et al. [2009] suggested that varying200

magnitude of the MIS 5e δ18O peak could be explained by different δ18O/temperature201

sensititives, owing to much higher MIS 5e temperatures than previously thought. However,202

they did not examine the possibility that atmospheric circulation changes associated with203

WAIS collapse could explain those differences. In our results with ECHAM4.6, the δ18O204

response is stronger at Dome C than at Vostok, even though the elevation at neither205

site changes. This is consistent with the observations. Such results are sensitive to the206



assumed ice sheet configuration, but it is clear that topography-induced atmospheric207

circulation changes need to be accounted for in the interpretation of ice core records.208

Whether differences among the East Antarctic records can be used to constrain past209

topographic changes should be examined further with a fully-coupled GCM that includes210

isotope tracers.211

Finally, our experiments may be used to guide the selection of new ice core records212

that could be used to obtain more definitive evidence for or against WAIS collapse.213

Comparison between the Mt. Moulton record and East Antarctic sites is complicated214

by the uncertainty associated with East Antarctic elevation change, and the problem of215

ice flow for some locations (EDML, Vostok, Talos). Furthermore, Mt. Moulton may be216

less than ideally situated as an indicator of WAIS elevation changes as it lies (at least217

in our experiments) near the boundary between positive and negative anomalies in δ18O.218

Other blue-ice areas that retain ice from MIS 5e, if they can be identified further westward219

along the Marie Byrd Land coast, would be useful. Another interesting site is Fletcher220

Promontory, which extends from the WAIS into the Ronne-Filchner Ice Shelf; an ice core221

record there was recently obtained by the British Antarctic Survey and may contain MIS222

5e ice. However, local elevation changes at Fletcher Promontory, and the possibilty of223

ice flow from higher elevations, are likely to complicate interpretation of that record. An224

especially promising location is Hercules Dome, located between the WAIS and the South225

Pole. Hercules Dome is not likely to have significantly changed in elevation in response226

to WAIS collapse [Jacobel et al., 2005; Pollard and DeConto, 2009], but its proximity to227



the WAIS means that warmer temperatures and elevated δ18O anomalies at that location228

may be diagnostic of the changed atmospheric circulation associated with WAIS collapse.229

5. Conclusion

Collapse of the West Antarctic Ice Sheet (WAIS) would cause regional changes in230

atmospheric circulation, with significant temperature anomalies over adjacent land and231

ocean areas. Robust responses to WAIS collapse include cooling over the Ross Ice Shelf232

and coastal Marie Byrd Land, and warming over the Ronne-Filchner Ice Shelf, coastal233

Dronning Maud Land, and at Hercules Dome. Ice core paleotemperature data show a234

significantly smaller difference between last-interglacial and Holocene temperature at Mt.235

Moulton, West Antarctica, than at all locations in East Antarctica. This observation is236

consistent with the climate model response, and thus provides supporting evidence for237

WAIS collapse during the last interglacial period.238

Acknowledgments. T. Sowers was the first to point out the evident correspondence239

between our model results and the Mt. Moulton record. We thank C.M. Bitz and E.240

Maroon for modeling support, L. Sime, E. Wolff, D.S. Battisti, T.J. Fudge and M. Whipple241

for helpful feedback, J. Pedro and F. Parrenin for assistance with the AICC2012 timescale,242

and R. DeConto for providing ice sheet model output data. This work was supported by243

U.S. National Science Foundation (grants 1043092 to EJS and 0230316 to JWCW) and244

the Deparment of Energy (Computational Science Graduate Fellowship to HAS). We also245

thank the Leverhulme Trust and the University of Edinburgh for support to EJS. This246

paper is dedicated to the memory of Stephen C. Porter. All data and model results from247



this paper will be archived at the National Snow and Ice Data Center (nsidc.org), in248

accordance with the AGU Data Policy.249

250

References

Bamber, J. L., R. E. M. Riva, B. L. A. Vermeersen, and A. M. LeBrocq (2009),251

Reassessment of the potential sea-level rise from a collapse of the West Antarctic Ice252

Sheet, Science, 324 (5929), 901–903.253

Bazin, L., A. Landais, B. Lemieux-Dudon, H. Toye Mahamadou Kele, D. Veres,254

F. Parrenin, P. Martinerie, C. Ritz, E. Capron, V. Lipenkov, M.-F. Loutre, D. Raynaud,255

B. Vinther, A. Svensson, S. O. Rasmussen, M. Severi, T. Blunier, M. Leuenberger,256

H. Fischer, V. Masson-Delmotte, J. Chappellaz, and E. Wolff (2013), An optimized257

multi-proxy, multi-site Antarctic ice and gas orbital chronology (AICC2012): 120–800258

ka, Climate of the Past, 9 (4), 1715–1731, doi:10.5194/cp-9-1715-2013.259

Bradley, S. L., M. Siddall, G. A. Milne, V. Masson-Delmotte, and E. Wolff (2013),260

Combining ice core records and ice sheet models to explore the evolution of the east261

antarctic ice sheet during the last interglacial period, Global and Planetary Change,262

100 (0), 278–290, doi:http://dx.doi.org/10.1016/j.gloplacha.2012.11.002.263

Dunbar, N. W., W. C. McIntosh, and R. P. Esser (2008), Physical setting and264

tephrochronology of the summit caldera ice record at Mount Moulton, West Antarctica,265

Geological Society of America Bulletin, 120 (7-8), 796–812.266

Dutton, A., and K. Lambeck (2012), Ice volume and sea level during the last interglacial,267

Science, 337 (6091), 216–219.268



EPICA Community Members (2006), One-to-one coupling of glacial climate variability in269

Greenland and Antarctica, Nature, 444 (7116), 195–198.270

Frierson, D. M. W., I. M. Held, and P. Zurita-Gotor (2006), A gray-radiation aquaplanet271

moist GCM. part I: Static stability and eddy scale, Journal of the Atmospheric Sciences,272

63 (10), 2548–2566, doi:10.1175/JAS3753.1.273

Gent, P. R., G. Danabasoglu, L. J. Donner, M. M. Holland, E. C. Hunke, S. R. Jayne,274

D. M. Lawrence, R. B. Neale, P. J. Rasch, M. Vertenstein, P. H. Worley, Z.-L. Yang,275

and M. Zhang (2011), The Community Climate System Model version 4, Journal of276

Climate, 24 (19), 4973–4991, doi:10.1175/2011JCLI4083.1.277

GFDL (2004), The new GFDL global atmosphere and land model AM2–LM2:278

Evaluation with prescribed SST simulations, Journal of Climate, 17 (24), 4641–4673,279

doi:10.1175/JCLI-3223.1.280

Hoffmann, G., M. Werner, and M. Heimann (1998), Water isotope module of the ECHAM281

atmospheric general circulation model: A study on timescales from days to several years,282

Journal Of Geophysical Research, 103 (16871—16896).283

Holden, P. B., N. R. Edwards, E. W. Wolff, N. J. Lang, J. S. Singarayer, P. J. Valdes, and284

T. F. Stocker (2010), Interhemispheric coupling, the West Antarctic Ice Sheet and warm285

Antarctic interglacials, Climate of the Past, 6 (4), 431–443, doi:10.5194/cp-6-431-2010.286

Jacobel, R. W., B. C. Welch, E. J. Steig, and D. P. Schneider (2005), Glaciological and287

climatic significance of Hercules Dome, Antarctica: An optimal site for deep ice core288

drilling, Journal Of Geophysical Research, 110, F01,015, doi:10.1029/2004JF000188.289



James, I. N. (1988), On the forcing of planetary-scale Rossby waves by Antarctica,290

Quarterly Journal Of The Royal Meteorological Society, 114, 619–637.291

Jouzel, J., N. I. Barkov, J. M. Barnola, M. Bender, J. Chappellaz, C. Genthon, V. M.292

Kotlyakov, V. Lipenkov, C. Lorius, J. R. Petit, D. Raynaud, G. Raisbeck, C. Ritz,293

T. Sowers, M. Stievenard, F. Yiou, and P. Yiou (1993), Extending the Vostok ice-core294

record of palaeoclimate to the penultimate glacial period, Nature, 364 (6436), 407–412.295

Jouzel, J., V. Masson-Delmotte, O. Cattani, G. Dreyfus, S. Falourd, G. Hoffmann,296

B. Minster, J. Nouet, J. M. Barnola, J. Chappellaz, H. Fischer, J. C. Gallet, S. Johnsen,297

M. Leuenberger, L. Loulergue, D. Luethi, H. Oerter, F. Parrenin, G. Raisbeck,298

D. Raynaud, A. Schilt, J. Schwander, E. Selmo, R. Souchez, R. Spahni, B. Stauffer,299

J. P. Steffensen, B. Stenni, T. F. Stocker, J. L. Tison, M. Werner, and E. W. Wolff300

(2007), Orbital and millennial Antarctic climate variability over the past 800,000 years,301

Science, 317 (5839), 793–796.302

Justino, F., A. S. Silva, M. P. Pereira, F. Stordal, D. Lindemann, and F. Kucharski303

(2015), The large-scale climate in response to the retreat of the West Antarctic Ice304

Sheet, Journal of Climate, 28 (2), 637–650, doi:10.1175/JCLI-D-14-00284.1.305

Korotkikh, E. V., P. A. Mayewski, M. J. Handley, S. B. Sneed, D. S. Introne,306

A. V. Kurbatov, N. W. Dunbar, and W. C. McIntosh (2011), The last307

interglacial as represented in the glaciochemical record from Mount Moulton blue308

ice area, West Antarctica, Quaternary Science Reviews, 30 (15–16), 1940–1947,309

doi:http://dx.doi.org/10.1016/j.quascirev.2011.04.020.310



Naish, T., R. Powell, R. Levy, G. Wilson, R. Scherer, F. Talarico, L. Krissek, F. Niessen,311

M. Pompilio, T. Wilson, L. Carter, R. DeConto, P. Huybers, R. McKay, D. Pollard,312

J. Ross, D. Winter, P. Barrett, G. Browne, R. Cody, E. Cowan, J. Crampton,313

G. Dunbar, N. Dunbar, F. Florindo, C. Gebhardt, I. Graham, M. Hannah, D. Hansaraj,314

D. Harwood, D. Helling, S. Henrys, L. Hinnov, G. Kuhn, P. Kyle, A. Laufer, P. Maffioli,315

D. Magens, K. Mandernack, W. McIntosh, C. Millan, R. Morin, C. Ohneiser, T. Paulsen,316

D. Persico, I. Raine, J. Reed, C. Riesselman, L. Sagnotti, D. Schmitt, C. Sjunneskog,317

P. Strong, M. Taviani, S. Vogel, T. Wilch, and T. Williams (2009), Obliquity-paced318

Pliocene West Antarctic ice sheet oscillations, Nature, 458 (7236), 322–328.319

NEEM Community Members (2013), Eemian interglacial reconstructed from a Greenland320

folded ice core, Nature, 493 (7433), 489–494.321

Otto-Bliesner, B. L., N. Rosenbloom, E. J. Stone, N. P. McKay, D. J. Lunt, E. C.322

Brady, and J. T. Overpeck (2013), How warm was the last interglacial? New323

model–data comparisons, Philosophical Transactions of the Royal Society of London324

A: Mathematical, Physical and Engineering Sciences, 371 (2001).325

Parish, T. R., and J. J. Cassano (2003), The role of katabatic winds on the Antarctic326

surface wind regime, Monthly Weather Review, 131, 317–333.327

Pollard, D., and R. M. DeConto (2009), Modelling West Antarctic ice sheet growth and328

collapse through the past five million years, Nature, 458 (7236), 329–332.329

Popp, T. J. (2008), The speed and timing of climate change: Detailed ice core stable330

isotope records from Northgrip, Greenland and Mt. Moulton, West Antarctica, Phd,331

University of Colorado.332



Roeckner, E., K. Arpe, L. Bengtsson, M. Christoph, M. Claussen, L. D. M. Esch,333

M. Giorgetta, U. Schlese, and U. Schulzweida (1996), The atmospheric general334

circulation model ECHAM-4: Model description and simulation of present-day climate,335

Max-Planck-Institut fur Meteorologie Report, 218 (90).336

Scherer, R. P., A. Aldahan, S. Tulaczyk, G. Possnert, H. Engelhardt, and B. Kamb (1998),337

Pleistocene collapse of the West Antarctic Ice Sheet, Science, 281 (5373), 82–85.338

Sime, L. C., E. W. Wolff, K. I. C. Oliver, and J. C. Tindall (2009), Evidence for warmer339

interglacials in East Antarctic ice cores, Nature, 462 (7271), 342–345.340

Steig, E., D. Morse, E. Waddington, M. Stuiver, P. Grootes, P. Mayewski, S. Whitlow,341

and M. Twickler (2000), Wisconsinan and Holocene climate history from an ice core342

at Taylor Dome, western Ross Embayment, Antarctica, Geografiska Annaler, 82A,343

213–235.344

Steig, E. J., J. L. Fastook, C. Zweck, I. D. Goodwin, K. J. Licht, J. W. C. White, and345

R. P. Ackert (2001), West Antarctic Ice Sheet elevation changes, Antarctic Research346

Series, 75, 75–90, doi:10.1029/AR077p0075.347

Steig, E. J., Q. Ding, J. W. C. White, M. Kuttel, S. B. Rupper, T. A. Neumann, P. D.348

Neff, A. J. E. Gallant, P. A. Mayewski, K. C. Taylor, G. Hoffmann, D. A. Dixon,349

S. W. Schoenemann, B. R. Markle, T. J. Fudge, D. P. Schneider, A. J. Schauer, R. P.350

Teel, B. H. Vaughn, L. Burgener, J. Williams, and E. Korotkikh (2013), Recent climate351

and ice-sheet changes in West Antarctica compared with the past 2,000 years, Nature352

Geoscience, 6 (5), 372–375.353



Stenni, B., D. Buiron, M. Frezzotti, S. Albani, C. Barbante, E. Bard, J. M. Barnola,354

M. Baroni, M. Baumgartner, M. Bonazza, E. Capron, E. Castellano, J. Chappellaz,355

B. Delmonte, S. Falourd, L. Genoni, P. Iacumin, J. Jouzel, S. Kipfstuhl, A. Landais,356

B. Lemieux-Dudon, V. Maggi, V. Masson-Delmotte, C. Mazzola, B. Minster,357

M. Montagnat, R. Mulvaney, B. Narcisi, H. Oerter, F. Parrenin, J. R. Petit, C. Ritz,358

C. Scarchilli, A. Schilt, S. Schupbach, J. Schwander, E. Selmo, M. Severi, T. F. Stocker,359

and R. Udisti (2011), Expression of the bipolar see-saw in Antarctic climate records360

during the last deglaciation, Nature Geosci, 4 (1), 46–49.361

Veres, D., L. Bazin, A. Landais, H. Toye Mahamadou Kele, B. Lemieux-Dudon,362

F. Parrenin, P. Martinerie, E. Blayo, T. Blunier, E. Capron, J. Chappellaz, S. O.363

Rasmussen, M. Severi, A. Svensson, B. Vinther, and E. W. Wolff (2013), The Antarctic364

ice core chronology (AICC2012): an optimized multi-parameter and multi-site dating365

approach for the last 120 thousand years, Climate of the Past, 9 (4), 1733–1748,366

doi:10.5194/cp-9-1733-2013.367

Watanabe, O., J. Jouzel, S. Johnsen, F. Parrenin, H. Shoji, and N. Yoshida (2003),368

Homogeneous climate variability across East Antarctica over the past three glacial369

cycles, Nature, 422 (6931), 509–512.370

Watterson, I. G., and I. N. James (1992), Baroclinic waves propagating from371

a high-latitude source, Quarterly Journal Of The Royal Meteorological Society,372

118 (23-50).373



C

A

Amundsen

SeaBell.

RF

Ross Ice ShelfMarie Byrd Land

West Antarctic Ice SheetEAIS

AP

B EDML

Moulton Taylor

Dome F

EDCTalosVostok

HerculesDome

FP

Figure 1. Prescribed Antarctic topography used in the GCM simulations: (A) Modern

Antarctic topography, with geographic features. WAIS: West Antarctic Ice Sheet. EAIS:

East Antarctic Ice Sheet. RF: Ronne-Filchner Ice Shelf. AP: Antarctic Peninsula. Bell.:

Bellinghausen Sea. Wedd.: Weddell Sea. Blue circles: ice-core locations discussed in the text.

Blue cross: South Pole. Green contour: 2000 m above sea level. Contour interval 250 m.

(B) WAIS-collapse topography for the fully-coupled model experiments with CCSM4. For the

aquaplanet experiments with GRaM and GFDL-AM2, all of the West Antarctic sector (shaded)

is set to zero elevation, and East Antarctic elevations are unchanged. Ice core locations (named)

and contours as in (A). (C) Difference between control (A) and WAIS-collapse topography (B)

for the CCSM4 experiments. Red contour = 1000 m elevation change. Contour interval = 250

m. The 100 m elevation-change contour is also shown (gray).



CCSM

4GR

aMGF

DL-

AM2

A

-8 -6 -4 -2 0 4 862

Temperature Change (°C)

Surface Temperature Potential temperature

B

C D

E F

G H

ECHA

M 4

.6

Figure 2. Response (“WAIS-collapse” minus control) of surface temperature (left column) and

potential temperature (right colum) to changes Antarctic topography as shown in Fig 1b. A,B)

GRaM and C,D) GFDL-AM2 aquaplanet experiments; all of West Antarctica is removed in the

WAIS-collapse simulations. E,F) ECHAM 4.6 with a slab ocean. G,H) CCSM4 fully-coupled

ocean and atmosphere. Circles show locations of ice cores discussed in the text.



Wind speed change

G

ECHA

M 4

.6

C D

CCSM

4AM

2

GRaM

BA

5 m/s

Figure 3. Surface-wind response to elevation changes from WAIS collapse from the GCM

experiments using A) GRaM, B) GFDL-AM2, C) ECHAM4.6, D) CCSM4.



0 10 20

��

��

��

��

��

��

��

��

��

��

��

��

110 120 ��

�

��

��

��

��

��

��

0

1

2

�

��

Holocene

��

Age (ka)

Figure 4. Comparison of ice core δ18O records for the Holocene and the last interglacial

period (green shading: MIS 5e interval). Purple line: Mt. Moulton δ18O (purple). Black line;

average δ18O anomaly of Talos Dome, EDML, Vostok, Dome Fuji, and EDC records from East

Antarctica (black). Dark gray shading: ± one standard deviation (σ) about the East Antarctic

mean, relative to the early-Holocene peak value at ∼10 ka. Light gray shading: ±2σ. The ice

core records are shown individually in Fig. S1 in the supporting information.


Documents

In uence of West Antarctic Ice Sheet collapse on Antarctic