Invasion of anthropogenic CO2 recorded in planktonic foraminifera from the northern Gulf of Aqaba

The stable carbon isotopic composition of the planktonic foraminifera Globigerinoides sacculifer and G. ruber (white) and sedimentary organic matter from the northern Gulf of Aqaba have been investigated to estimate changes in δ^sup 13^C^sub DIC^ in surface waters during the last 1,000 years. The high sedimentation rates at the core sites (about 54 cm/Kyear) provide high temporal resolution (~10 years). Recent sediments at the top of the cores reflect conditions younger than 1950. The δ^sup 13^C records of the planktonic foraminifera from three multicores display similar trends, showing a uniform and consistent pattern before the 1750s, and a gradual decrease of approximately 0.63[per thousand] over the last two centuries. This decrease seems to track the decrease of δ^sup 13^C^sub DIC^ in surface waters, which is mainly caused by the increase of anthropogenic input of ^sup 13^C-depleted CO^sub 2^ into the atmosphere. Similarly, a trend towards lighter values of the carbon isotopic composition of sedimentary organic matter (δ^sup 13^C^sub org^) during the last 200 years supports the interpretation obtained from the planktonic foraminiferal δ^sup 13^C. Furthermore, direct measurements of seawater show that δ^sup 13^C of the dissolved inorganic carbon (DIC) in the northern Gulf of Aqaba has decreased by about 0.44[per thousand] during the period 1979-2000. The average annual decrease is 0.021[per thousand], which is similar to that observed globally. The δ^sup 13^C values of planktonic foraminifera combined with organic matter δ^sup 13^C from marine sediments are good indicators for reconstructing past changes in atmospheric CO^sub 2^ concentrations from the northern Gulf of Aqaba.[PUBLICATION ABSTRACT]