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 !