Carbon isotope composition of Caribbean Sea surface waters: Response to the uptake of anthropogenic CO2

Abstract

[1] The burning of fossil fuels and deforestation have significantly increased atmospheric CO2 levels, from ∼280 ppm prior to the industrial revolution to the present value of ∼390 ppm. Suess (1955) was the first to show that the carbon isotopic composition of the atmosphere is changing in response to the anthropogenic input of radiocarbon-dead, 13C depleted CO2 from fossil fuel combustion. Here we report a high resolution planktonic foraminiferal δ13C record from the Caribbean Sea for the last 300 years that clearly resolves the timing and magnitude of the marine 13C Suess effect associated with the oceanic uptake of anthropogenically derived CO2. Cariaco Basin sediment trap and upper-most box core sediment δ13C match both the trend and magnitude of observed δ13C changes in atmospheric CO2 over the last 15 years. The longer sediment record suggests the marine Suess effect to be −0.75 ‰ from pre-industrial values, with most of the change occurring since 1950, coincident with the rapid rise in atmospheric CO2 noted in ice core and instrumental data. If the current anthropogenic CO2 emission trend continues, extrapolating our marine δ13C rate curve into the future suggests that the rate of marine δ13C change caused by anthropogenic CO2 will increase to −0.10 ‰ yr−1 by the end of this century, an increase of more than an order of magnitude from 1950 values.