The Marine Radiocarbon Reservoir Effect and its correlation with the ocean dynamics

The marine reservoir effect (MRE) is closely related to the ocean dynamics of each region and, therefore, can be used as a powerful tool to understand ocean circulation. Radiocarbon measurements on marine taxa and/or water masses can be related to density and temperature data to yield an useful picture of coastal processes.

This study presents MRE data for the Brazilian coast, where the two main ocean currents display different features. The Brazil current carries warm subtropical waters while the Falklands current is composed by cold subantartic waters. They flow in opposite directions along the coast and their encounter, around 38S, creates a strong thermohaline front referred to as Brazil-Falklands Confluence (Roden, 1986; Gordon,1989).

Radiocarbon dating of marine species was performed for different regions on the Brazilian coast. The use of samples from both, archaeological sites and museum collections, can give a consistent time frame for changes in the MRE and, potentially, in the South Atlantic Ocean circulation patterns. Moreover, seasonally or annually resolved coral carbon concentration measurements constitute a convenient tool for assessing sea-water radiocarbon signatures (Druffel and Linick, 1978; Dunbar and Colle, 1999; Druffel et al., 2007). These measurements are being performed in an attempt of creating a coral-based database for radiocarbon variability in the South Atlantic Ocean through time.

Dunbar, R. G., and J. E. Cole (1999), Annual records of tropical systems (ARTS), Workshop Rep., 99-1, 72pp., Past Global Changes, Bern. Druffel, E. R. M., and T.W. Linick (1978), Radiocarbon in annual coral rings of Florida, J. Geophys. Res. Lett., 5(11), 913-917.

Druffel, E. R. M., S. Griffin, S. R. Beaupre, and R. B. Dunbar (2007), Oceanic climate and circulation changes during the past four centuries from radiocarbon in corals, Geophys. Res. Lett., 34, L09601.

Gordon, A. L. (1989), Brazil-Malvinas Confluence - 1984. Deep Sea Research, 36, 359-384.

Roden, G. I. (1986), Thermohaline fronts and baroclinic flow in the Argentine basin during the Austral Spring of 1984. J. Geophys. Res., 91, 5075-5093.