The oldest ice challenge: potential sites and new drilling technology Jérôme Chappellaz and the Ice&Lasers/Subglacior team Laboratoire de Glaciologie et Géophysique de l’Environnement, Grenoble, France

Climate and CO 2 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 traverse L. 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 Concordia Point Barnola

8 S2 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 H 2 O/yr Point Barnola : 2.3 cm S2 : 2.1 cm S3 : 1.6 cm S4 : 1.6 cm S3 S4 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 (CH 4, maybe more) Innovative approach : in-situ probe with embedded OF-CEAS to qualify potential sites Design : O. Alemany

DFB diode laser PD signal PZ T LD translation Variable attenuator PD ref 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 CH 4 profile from NEEM using OF-CEAS technology and CFA Chappellaz et al., 2013

How to handle the drilling chips ?

A 3500 hose pipe in one piece Certified to -40°C (to be tested up to -50°C) One winch for the hose One winch for the main cable (power, data) Winch and hose

50 mm external diameter!!! Laser Lens 1 PD ref Attenuator Cavity PD sig Wedge Lens 2 50 mm external diameter!!! OF-CEAS probe instrument R. Grilli, unpublished

OF-CEAS probe instrument housing Spectro housing First insulation Gas exit/vacuum Fluid 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 !