Radiocarbon in annual coral rings of Florida

Abstract

Radiocarbon measurements on a 175‐year (A.D. 1800 to 1974) growth of the coral Montastrea annularis from The Rocks reef off the Florida Keys reveal the rate of local uptake of fossil fuel CO2 and bomb 14C by surface ocean waters of the Gulf Stream. In the nineteenth century, the pre‐bomb, pre‐industrial Δ14C value of surface ocean waters as seen in these corals of the Gulf Stream in the Florida Straits was −51 ± 2‰. By 1955, uptake of industrial CO2 by these waters had lowered the Δ14C values to about −61‰. The results can be used to make predictions regarding anthropogenic CO2 that can be expected to enter the oceans in future decades. Bomb‐produced 14C is found to be present in the corals in comparable concentrations to that found in the dissolved inorganic carbon (DIOC) of the North Pacific and North Atlantic Oceans.

New views of tropical paleoclimates from corals

“…Over longer time scales of several centuries, records of C in corals have been used to reconstruct past mixing rates between surface and subsurface waters in an ocean basin (Dru!el, 1989;1997b), detect the presence of fossil fuel-derived CO in the upper ocean (Dru!el and Linick, 1978;Nozaki et al, 1978), and help determine the decadal variability of ocean circulation (Dru!el and Gri$n, 1993). A biennial C record for a coral from Abraham Reef in the southern Great Barrier Reef of Australia is shown in Fig.…”

“…The evolution of radiocarbon in the surface ocean in response to nuclear testing was "rst described by Nozaki et al (1978) and Dru!el and Linick (1978) using corals sampled at annual resolution. More recently, large seasonal and interannual variability (i.e., 30}100 ), of the same order as the spatial variability of radiocarbon across the surface ocean (&100 ), was identi"ed in corals sampled at sub-annual resolution at a variety of locations (Dru!el, 1987;Brown et al, 1993;Moore et al, 1997;.…”

Decadal- to interannual-scale source water variations in the Caribbean Sea recorded by Puerto Rican coral radiocarbon

“…What is needed is a multi-decadal record of water-mass tracers that integrates the high frequency variability such as eddies and tides, but resolves the interannual-to decadal-scale variability. Massive corals provide an ideal archive of such information because their skeletons record the Δ 14 C of the dissolved inorganic carbon (DIC) in the water as they grow, which can be used as a water-mass tracer (e.g., Druffel and Griffin 1993;Druffel and Linick 1978;Guilderson et al 2004;Guilderson et al 1998). These corals can be long-lived (centuries), and their skeletons have annual density bands, much like tree rings, which can be counted to provide excellent age control for the measured geochemical tracer time series.…”

Seasonal Radiocarbon Variation of Surface Seawater Recorded in A Coral from Kikai Island, Subtropical Northwestern Pacific

“…Thus, corals can provide long-term histories with an exact time axis, as opposed to the snapshot views of ∆ 14 C distributions that accrue from occasional observations made by big projects such as the Geochemical Oceans Sections Study (GEOSECS) and the World Ocean Circulation Experiment (WOCE). 14 C measurements across coral density bands have revealed the lowering of ∆ 14 C at the ocean surface from the late 1800s through to 1955, which was mostly due to the uptake of anthropogenic 14 C-free CO 2 emission to the atmosphere by burning of fossil fuels, as well as a sudden increase in the atmospheric testing of nuclear weapons in the 1950s and 1960s (Druffel and Linick 1978;Nozaki et al 1978). Recent investigations on the coral ∆ 14 C variations with sub-annual resolution give a new insight of intra-annual decadal variability of the ocean circulations in surface and subsurface water and air-sea CO 2 exchange (Druffel 1989;.…”