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

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

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slide1

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?
slide2

Context

  • Different orbital contexts : excentricity, phase betweenprecession and obliquity
  • Differentdeglacialcontexts and earlyinterglacialbipolarseesaw

EPICA

Dome C

Greenland

Masson-Delmotte et al, PNAS, 2010

slide3

Drilling Sites

  • Seasonality of seaice and « continentality »
  • Ice flow thinning

Masson-Delmotte et al, CP, in press

slide4

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

slide5

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

slide6

Common Signals (EOF analysis)

  • First EOF : temperaturehistory
  • Second EOF : elevation changes
  • No trivial relationshipwith the orbital context

Masson-Delmotte et al, CP, in press

slide7

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

slide8

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)

slide9

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
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