Abstract

Radiocarbon (14C) is produced by spallation reactions in the atmosphere, mixes with the stable carbon isotopes and becomes part of the global carbon cycle. The large oceanic carbon reservoir hosts the majority of 14C decay, and thus the partitioning of radiocarbon between atmosphere and ocean holds key information on the exchange of carbon between ocean and atmosphere as well as the rate of ocean overturning and the ventilation of deep waters. During the Last Glacial Maximum (LGM) atmospheric 14C/C was ~40% greater than in the pre-nuclear modern, and 14C/C declined over the course of the deglacial in a manner that very much mirrors the rise of atmospheric CO2 . Furthermore, anomalously low 14C/C reconstructions correlated to deglacial climate swings and CO2 rise have been interpreted as the release of a hypothesised, previously stagnated deep ocean reservoir of sequestered CO2 . This talk describes numerical model results that speak to the occurrence (or not) of deep ocean stagnation during the LGM and mechanisms that explain (or not) the deglacial decline of atmospheric 14C/C.

References:

Hain et al (2014) Distinct roles of the Southern Ocean and North Atlantic in the deglacial atmospheric radiocarbon decline. EPSL 394 , 198-208

Hain et al (2014) The biological pump in the past. Treatise on geochemistry, vol 8 pp 485 – 517 (email nr297@cam.ac.uk if you would like a copy)