The proposed Anthropocene Global Boundary Stratotype Section and Point (GSSP) candidate site of West Flower Garden Bank (27.8762°N, 93.8147°W) is an open ocean location in the Gulf of Mexico with a submerged coral reef and few direct human impacts. Corals contain highly accurate and precise (<±1 year) internal chronologies, similar to tree rings, and their exoskeletons are formed of aragonite and can be preserved in the rock record. Here we present results from a large Siderastrea siderea coral (core 05WFGB3; 1755–2005 CE) sampled with annual and monthly resolutions that show clear markers of global and regional human impacts. Atmospheric nuclear bomb testing by-products (14C,239+240Pu) have clear increases in this coral starting in 1957 for14C and the first increase in 1956 for239+240Pu (potential bases for the Anthropocene GSSP). Coral δ13C declined especially after 1956 consistent with the Suess Effect resulting from the burning of fossil fuels. Coral skeletal δ15N starts to increase in 1963 corresponding with the increase in agricultural fertilizers. Coral Hg concentrations (1933–1980) loosely track fluctuations in industrial pollution and coral Ba/Ca increases from 1965–1983 when offshore oil operations expand after 1947. Coral temperature proxies contain the 20th-century global warming trend whereas coral growth declines during this interval.
This content will become publicly available on November 27, 2024
Radiocarbon (14C) is a critical tool for understanding the global carbon cycle. During the Anthropocene, two new processes influenced14C in atmospheric, land and ocean carbon reservoirs. First,14C-free carbon derived from fossil fuel burning has diluted14C, at rates that have accelerated with time. Second, ‘bomb’14C produced by atmospheric nuclear weapon tests in the mid-twentieth century provided a global isotope tracer that is used to constrain rates of air–sea gas exchange, carbon turnover, large-scale atmospheric and ocean transport, and other key C cycle processes. As we write, the14C/12C ratio of atmospheric CO2is dropping below pre-industrial levels, and the rate of decline in the future will depend on global fossil fuel use and net exchange of bomb14C between the atmosphere, ocean and land. This milestone coincides with a rapid increase in14C measurement capacity worldwide. Leveraging future14C measurements to understand processes and test models requires coordinated international effort—a ‘decade of radiocarbon’ with multiple goals: (i) filling observational gaps using archives, (ii) building and sustaining observation networks to increase measurement density across carbon reservoirs, (iii) developing databases, synthesis and modelling tools and (iv) establishing metrics for identifying and verifying changes in carbon sources and sinks.
This article is part of the Theo Murphy meeting issue 'Radiocarbon in the Anthropocene'.more » « less
- Award ID(s):
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- Publisher / Repository:
- Philosophical Transactions of the Royal Society
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- Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
- Medium: X
- Sponsoring Org:
- National Science Foundation
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