Carbon isotopes in ice cores

LAME is developing an ultra-sensitive, laser-based spectrometer for the ¹³C analysis of atmospheric carbon dioxide in gas trapped in bubbles in ice-cores, and to couple this device to the dry gas extraction instruments of the Grenoble Glaciology Laboratory (LGGE). This requires the analysis of exceedingly small samples of CO₂ (nano-mols), while maintaining an extremely high level of precision (~0.05 permil).

While this project started as the project of PhD student Miral Shah (co-supervised by Dr. Chappellaz of the LGGE) with funding from the UJF ("Pole SMINGUE"), it is currently an integral part of Ice&Lasers, and carried principally by Dr. Romanini as far as the quantum cascade laser (QCL) instrumentation is concerned.

Compared to the current ¹³C measurement technique of isotope ratio mass spectrometry, the laser system will provide both a higher measurement precision (necessary to resolve the small natural ¹³C variations) and a more than two orders of magnitude higher sample throughput, enabling us to improve the temporal resolution of the signal, while at the same time running more samples for improved statistics. This is expected to lead to a true revolution in the field of ice-core paleo-climatology, which has been engaged for over one decade in a struggle to understand the mechanisms that control the natural variability of the carbon dioxide greenhouse gas between glacial and interglacial cycles. Considering the strong correlation between the carbon cycle and climate, and in light of the post-industrial revolution, anthropogenic increase of the CO₂ concentration, this is becoming an ever more urgent issue.