Measurements of carbon-14 in polar ice : discoveries, future applications and challenges

Séminaire de V. Petrenko (Univ. Rochester - USA), le Vendredi 5 Avril 2019 à 11h en salle Lliboutry, Bât. Glaciologie

Title : Measurements of carbon-14 in polar ice : discoveries, future applications and challenges

Abstract :
The carbon-14 (14C) content in polar ice is determined primarily by trapping of carbon-containing atmospheric gases (carbon dioxide (CO2), methane (CH4), carbon monoxide (CO)) and in situ production by cosmic rays directly in the ice. Considered separately, both the paleoatmospheric and the in situ cosmogenic 14C components have a range of interesting applications in geosciences. For example, paleoatmospheric 14C-CH4 serves as an unambiguous tracer of the fossil component of the global methane budget. Paleoatmospheric 14C-CO can be used as a proxy for long-term changes in the oxidative capacity of the atmosphere. The in situ cosmogenic 14C content in ice depends on 14C production rates, and has the potential to be used as a proxy for past changes in the flux of galactic cosmic rays.
However, 14C measurements in ice are inherently challenging because 1) 14C is an ultra-trace isotope, requiring very large sample sizes, 2) the paleoatmospheric and in situ cosmogenic signals are present in a combined form and 3) there are important gaps in our understanding of in situ cosmogenic 14C production in ice. This talk will present an overview of our recent results from work on 14C in polar ice and highlight promising future directions.

Vasilii Petrenko
Associate Professor
Dept of Earth and Environmental Sciences
University of Rochester
USA