A COMPARISON OF THE PRESENT AND LAST INTERGLACIAL IN SIX A NTARCTIC ICE CORES V. Masson-Delmotte, D....
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Transcript of A COMPARISON OF THE PRESENT AND LAST INTERGLACIAL IN SIX A NTARCTIC ICE CORES V. Masson-Delmotte, D....
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