Investigating the 13C Suess effect in the northwestern North Atlantic

Abstract

The carbon isotope signature (δ13C) of atmospheric CO2 has decreased as a direct result of anthropogenic CO2 emissions since the industrial revolution. This climate phenomenon has been termed the 13C Suess effect, and can be used to trace anthropogenic CO2 penetration into the surface ocean. This thesis presents the first long-term δ13C time series from the northwestern shelf region of the North Atlantic recorded in fossil foraminifera from five high-resolution sediment cores. These records reveal a Suess effect signal that emerges in the mid-twentieth century with a magnitude of -0.64±0.32 permil (i.e., 40% of the atmospheric signal) and a δ13C decrease rate of -0.014±0.005 permil/yr (58% of the atmospheric rate), a δ13C decrease unprecedented over the 4000 years sampled by the foraminifera records. The implications of these findings are discussed in the context of air-sea CO2 exchange rates, foraminiferal calcification vital effects, and post-depositional processes in the sediments.