THE POTENTIAL FOR SULFATE REDUCTION AND PYRITE DEPOSITION TO ALTER THE OCEAN ATMOSPHERE CARBON BALANCE DURING AN OCEANIC ANOXIC EVENT
Oceanic Anoxic Events (OAEs) coincide with large changes in the global carbon system. Deep water anoxia is believed to be induced by increased transport of nutrients to the ocean in turn caused by a warm climate. The enhanced primary production and burial results in a draw down of CO2 from the atmosphere. However, there are other processes taking place in an anoxic water column with the potential to affect the carbon system. Here we develop a three box ocean-atmosphere model to investigate the effect of sulfate reduction and subsequent pyrite deposition. Sulfate reduction results in an addition of alkalinity. Although this effect is counteracted by re-oxidation of the produced hydrogen sulfide as it reaches oxygenated surface waters, a fraction of the alkalinity increase persists as hydrogen sulfide reacts with iron minerals to form pyrite. Using an estimate of the amount of pyrite sulfur deposited during the Toarcian OAE, we evaluate the effect on the carbon system. Furthermore, motivated by the scarcity of carbonates deposited during anoxic events, we scrutinize the system including and excluding the regulation by calcite compensation. We find that the effect of pyrite deposition is probably small compared to the increased organic carbon burial. However, the importance of calcite compensation is underlined by the much greater carbon system response when excluding this mechanism.
Hieronymus, J., Stockholm University, Sweden, firstname.lastname@example.org
Walin, G., University of Gothenburg, Sweden, email@example.com
Nycander, J., Stockholm University, Sweden, firstname.lastname@example.org
Location: 316 A
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