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, A. 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

• What can be the causes for regional differences in Antarctic stable isotope records?

• What are the differences between the current and last interglacial?

Masson-Delmotte et al, PNAS, 2010

EPICADome C

Greenland

CONTEXT

• Different orbital contexts : excentricity, phase between precession and obliquity

• Different deglacial contexts and early interglacial bipolar seesaw

Masson-Delmotte et al, CP, in press

DRILLING SITES

• Seasonality of sea ice and « continentality »

• Ice flow thinning

Masson-Delmotte et al, CP, in press

ORIGIN OF MOISTURE AND PRECIPITATION SEASONALITY

Moisture origins : larger seasonality for the coastal sites (Taylor Dome and TALDICE)

Difference between precipitation weighted temperature and annual mean temperature (ERA40) : larger bias for the inland sites

Masson-Delmotte et al, CP, in press

STABLE ISOTOPE RECORDS ON EDC3 AGE SCALE

• Site-specific trends

• Common to the current and last interglacial

• Abrupt drop in d18O during glacial inception at EDML and TALDICE (increased sea ice cover?)

Masson-Delmotte et al, CP, in press

COMMON SIGNALS (EOF ANALYSIS)

• First EOF : temperature history

• Second EOF : elevation changes

• No trivial relationship with the orbital context

Masson-Delmotte et al, CP, in press

SITE SPECIFIC RESIDUALS

Main possible causes :

• Precipitation intermittency

To assess with climate model simulations with isotopes (difficult in response to orbital forcing alone)

See the poster of Louise Sime

• Site elevation changes

Qualitatively consistent with ice sheet model outputs;Suggests larger elevation changes than simulated.

Pol et al, EPSL, 2010; CP, 2010; in prep

20 YR RESOLUTION ANALYSES IN EPICA DOME C

Freq

uenc

y (1

/ky)

Age (ky BP)

Period (ky)

variability high variability

Tran

sitio

n

Running standard

Deviation over 3ky

Running standard

Deviation over 3ky

Holocene

MIS5

(Resampled every 20y)

(Resampled every 20y)

Age (ky BP)

Freq

uenc

y (1

/ky)

Period (ky)

Age (ky BP)

MIS1

MIS5.5 Centered δD

‰

Signal ‰

minus trend

Centered δD

‰

Signal ‰

minus trend

High variability variabilityTransition

variability variability

variability variability

• Larger variance during MIS5.5• Significant changes in variance • Shifts in multi-centennial to millennial periodicities

MIS1

MIS5.5

CONCLUSIONS AND PERSPECTIVES

• Differences between the current and last interglacial in Antarctica- Changes in mean state (common to 6 ice cores in East Antarctica)- Changes in variability (at Dome C) : variance level, power spectrum

• Mechanisms responsible for these changes poorly understood- climate models show very small response to orbital forcing- importance of changes in past ice sheet geometry (WAIS+EAIS)- ocean dynamics, natural (solar, volcanic) forcings (not documented for MIS5.5)

• Differences between ice core records- long term: changes in ice sheet topography- short term: precipitation intermittency, moisture origin (links with sea ice cover)

• Perspectives: - comparisons with climate and ice sheet model results- new information on MIS5.5 may come from the NEEM and WAIS ice cores