A comparison of the present and last interglacial in six Antarctic ice cores

1. A comparison of the present and last interglacial in six Antarcticicecores V. Masson-Delmotte, D. Buiron, A. Ekaykin, M. Frezzotti, H. Gallée, J. Jouzel, G. Krinner, Landais, H. Motoyama, H. Oerter, K. Pol, D. Pollard, C. Ritz, E. Schlosser, L.C. Sime, H. Sodemann, B. Stenni, R. Uemura, F. Vimeux LSCE and LGGE, France - AARI, Russia - ENEA, U. Trieste, Italy - NIPR and U. Ryukyus, Japan - AWI, Germany - Penn State, USA - U. Innsbruck, Austria - BAS, UK - NILU, Norway • Whatcanbe the causes for regionaldifferences in Antarctic stable isotope records? • What are the differencesbetween the current and last interglacial?

2. Context • Different orbital contexts : excentricity, phase betweenprecession and obliquity • Differentdeglacialcontexts and earlyinterglacialbipolarseesaw EPICA Dome C Greenland Masson-Delmotte et al, PNAS, 2010

3. Drilling Sites • Seasonality of seaice and « continentality » • Ice flow thinning Masson-Delmotte et al, CP, in press

4. Origin of Moisture and PrecipitationSeasonality Moistureorigins : largerseasonality for the coastal sites (Taylor Dome and TALDICE) Differencebetweenprecipitationweightedtemperature and annualmeantemperature (ERA40) : largerbias for the inland sites Masson-Delmotte et al, CP, in press

5. Stable Isotope Records on EDC3 agescale • Site-specific trends • Common to the current and last interglacial • Abrupt drop in d18O during glacial inceptionat EDML and TALDICE (increasedseaicecover?) Masson-Delmotte et al, CP, in press

6. Common Signals (EOF analysis) • First EOF : temperaturehistory • Second EOF : elevation changes • No trivial relationshipwith the orbital context Masson-Delmotte et al, CP, in press

7. Site SpecificResiduals • Main possible causes : • Precipitationintermittency • To assesswithclimate model simulations with isotopes (difficult in response to orbital forcing alone) • See the poster of Louise Sime • Site elevation changes • Qualitatively consistent withicesheet model outputs; • Suggestslargerelevation changes thansimulated. Masson-Delmotte et al, CP, in press

8. 20 yrresolution analyses in EPICA Dome C • Larger variance during MIS5.5 • Significant changes in variance • Shifts in multi-centennial to millennialperiodicities MIS1 MIS1 CenteredδD ‰ Period (ky) Frequency (1/ky)  variability  variability Signal ‰ minus trend  variability  variability Age (ky BP) Holocene MIS5.5 (Resampledevery 20y) CenteredδD ‰ MIS5.5 Running standard Deviation over 3ky MIS5 Transition (Resampled every 20y) Signal ‰ minus trend High variability variability Period (ky) Frequency (1/ky) Running standard Deviation over 3ky Transition  variability highvariability Age (ky BP) Pol et al, EPSL, 2010; CP, 2010; in prep Age (ky BP)

9. Conclusions and Perspectives • Differencesbetween the current and last interglacial in Antarctica • - Changes in meanstate (common to 6 icecoresin East Antarctica) • - Changes in variability(atDome C) : variance level, power spectrum • Mechanismsresponsible for these changes poorlyunderstood • - climatemodels show verysmallresponse to orbital forcing • - importance of changes in pasticesheetgeometry (WAIS+EAIS) • - oceandynamics, natural(solar, volcanic) forcings (not documented for MIS5.5) • Differencesbetweenicecore records • long term: changes in icesheettopography • short term: precipitationintermittency, moistureorigin (links withseaicecover) • Perspectives: • comparisonswithclimate and icesheet model results • new information on MIS5.5 may come from the NEEM and WAIS icecores