Post-Bomb Radiocarbon Records of Surface Corals from the Tropical Atlantic Ocean

• Published in: Radiocarbon
• Main Author: Druffel, Ellen R. M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1996
• Subjects: North Atlantic
• Online Access: http://dx.doi.org/10.1017/s0033822200030095; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033822200030095

Δ 14 C records are reported for post-bomb corals from three sites in the tropical Atlantic Ocean. In corals from 18°S in the Brazil Current, Δ 14 C values increased from ca . −58% in the early 1950s to +138% by 1974, then decreased to 110‰ by 1982. Shorter records from 8ºS off Brazil and from the Cape Verde Islands (17°N) showed initially higher Δ 14 C values before 1965 than those at 18ºS, but showed lower rates of increase of Δ 14 C during the early 1960s. There is general agreement between the coral results and Δ 14 C of dissolved inorganic carbon (DIC) measured in seawater previously for locations in the tropical Atlantic Ocean. Δ 14 C values at our tropical ocean sites increased at a slower rate than those observed previously in the temperate North Atlantic (Florida and Bermuda), owing to the latter's proximity to the bomb 14 C input source in the northern, hemisphere. Model results show that from 1960–1980 the Cape Verde coral and selected DIG Δ 14 C values from the North Equatorial Current agree with that calculated for the North Atlantic based on an isopycnal mixing model with a constant water mass renewal rate between surface and subsurface waters. This is in contrast to Δ 14 C values in Bermuda corals that showed higher post-bomb values than those predicted using a constant water mass renewal rate, hence indicating that ventilation in the western north Atlantic Ocean had decreased by a factor of 3 during the 1960s and 1970s (Druffel 1989).