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Abstract

The Anthropocene is a proposed term for the present geological epoch (from the time of the Industrial Revolution onwards), during which human influence significantly impacts the environment. We argue that the burning of isotopically light fossil fuel that causes the so-called “δ13C Suess effect” leaves such a strong imprint on marine sediments that it may serve to define the onset of this geological epoch. Sediment data with high temporal resolution from the recent past reveal a trend corresponding to a negative carbon isotope excursion of the order of one permil, comparable to carbon isotope excursions in the deep past that define stratigraphic boundaries such as the Paleocene–Eocene Thermal Maximum (PETM). A global carbon cycle model based on the MIT general circulation model (MITgcm), fitted with carbon isotopes 13C and 14C and forced with observed changes in the atmospheric carbon dioxide partial pressure (pCO2) and the carbon isotopic ratio 13C/12C (δ13Catm) allows us to investigate the temporal evolution and three-dimensional structure of the anomaly.Thus we show the carbon isotopic ratios of fossil shells of benthic foraminifera (δ13Cc) from selected ocean sediment cores, for example, for GeoB6008 (31° N) and GeoB9501 (17° N) over the Anthropocene (mainly the 20th century). The decrease in δ13Cc at 31° N is about 0.8 permil; off Mauretania (at 17° N in the shadow zone of the subtropical gyre) it still amounts to about 0.4 permil. We use the MITgcm including the global carbon isotopic cycles to extrapolate this change in δ13Cc to the future.