The oldest ice challenge: potential sites and new drilling technology
Jérôme Chappellaz and the Ice&Lasers/Subglacior teamLaboratoire de Glaciologie et Géophysique de l’Environnement, Grenoble, France
• Climate and CO2 record covering the last 1.5 million years to evaluate climate sensitivity
• One shot with conventional ice core drilling operations : too risky and costly
40 kyr periodicity100 kyr periodicity
The “Oldest Ice“ challenge
Continental ice volume from δ18O stack of benthic foraminifera
Lisiecki & Raymo, 2005
Where to find such old ice in Antarctica?
Pattyn, 2010
IPICS Oldest Ice workshop, 6-7 October 2012, France
Best guess:
• 2500-m thickness max.
• Smooth bedrock
• Close to current domes or saddles
• Simple ice flow regime
Where to find such old ice in Antarctica?
Current requirements :
• High-resolution 3D radar reconstructions
• 3D ice-flow modelling
• Shallow-intermediate drilling and snow radar for accumulation rate steadiness
• Rapid access drilling Van Liefferinge and Pattyn, 2013
Basal temperature
VANISH / EXPLORE 2011/2012 traverseL. Arnaud, O. Alemany , J. Chappellaz, E. Lefebvre, M. Lemeur, G. Teste (LGGE), M. Bes de Bec (IPG Strasboug), M.
Schneebeli (SLF, Davos)
A. Vende, D. Colin, A. Leluc (IPEV)
M. Fily (LGGE métropole)
Vostok
ConcordiaPoint
Barnola
8
S2
DC
DC S1B
Example of isochrones between Concordia and S1B
Lemeur et al., à soumettre
Mean accumulation over the last 300 years:•DC : 2.5 cm H2O/yr•Point Barnola : 2.3 cm•S2 : 2.1 cm•S3 : 1.6 cm•S4 : 1.6 cm
S3S4
Point Barnola
Bedrock:Texas radar
• Run in a single field season down to bedrock• Check statigraphic continuity within the ice sheet • Real-time in-situ measurement of water isotopes (climate) and greenhouse gases (CH4, maybe more)
Innovative approach : in-situ probe with embedded OF-CEAS to qualify potential sites
Design : O. Alemany
DFB diode laser
PDsignal
PZT
LD
translationVariableattenuator
PDref
current ramp
O.F.
Advantages:• Simple optical layout with few components• Small cavity (~ 10 cc), small sample size• Built-in frequency scale calibration (determined by cavity)• High light transmission• Switch between CEAS and CRDS modes for absorption calibration
Optical self-locking and narrowing of the laser frequency to the very narrow cavity transmission peaks
Optical Feedback Cavity Enhanced Absorption Spectroscopy(OF-CEAS)
Morville et al., Patent 2005
Semi-continuous CH4 profile from NEEMusing OF-CEAS technology and CFA
Chappellaz et al., 2013
How to handle the drilling chips ?
A 3500 hose pipe in one pieceCertified to -40°C (to be tested up to -50°C)
One winch for the hoseOne winch for the main cable (power, data)
Winch and hose
50 mm external diameter!!!
LaserLens1PD refAttenuator
CavityPD sig
WedgeLens2
50 mm external diameter!!!
OF-CEAS probe instrument
R. Grilli, unpublished
OF-CEAS probe instrument housing
Spectro housing
First insulation
Gas exit/vacuumFluid channel x3
Second insulation
Conclusions
• The Oldest Ice challenge requires a lot of parallel tasks to reach success : snow radar, bedrock radar, modelling, rapid access drilling
• We hope that the Subglacior probe will be able to qualify sites and to provide the primary information (climate, GHG), notably in the vicinity of Concordia
• The LIA Vostok can frame the technological collaboration between the LGGE and Mining Institute, and future prospects south of Vostok
Thanks !