Carbonate mineral saturation states along the U.S. East Coast

Jiang, Li-Qing, Wei-Jun Cai, Richard A. Feely, Yongchen Wang, Xianghui Guo, Dwight K. Gledhill, Xinping Hu, Felipe Arzayus, Feizhou Chen, Justin Hartmann, and Longjun Zhang

Limnol. Oceanogr., 55(6), 2010, 2424-2432 | DOI: 10.4319/lo.2010.55.6.2424

ABSTRACT: To assess the impact of ocean acidification on the carbonate chemistry of the shelf waters off the southeastern United States (South Atlantic Bight [SAB]), we measured carbonate mineral saturation states from January 2005 to May 2006. The findings reveal that aragonite (Varag: 2.6-4.0) and calcite (Vcal: 4.1-6.0) saturation states were considerably higher than those recently reported along the West Coast of North America. Different water mass age between the Atlantic and Pacific Oceans during global ocean circulation is the primary reason for the higher carbonate mineral saturation states in the SAB than along the West Coast. The contrasting water temperatures in the two coasts contribute to such differences. Both upwelling and freshwater discharge also play important roles in controlling saturation state. Carbonate mineral saturation in the surface water of the West Coast is strongly controlled by the upwelling of high-salinity, low-temperature, low-oxygen, and low-pH deep water. In comparison, saturation states in the surface water of the SAB coast are rarely affected by upwelling. Instead, they are strongly influenced by the input of low-saturation-state water from rivers. Continued increases of atmospheric CO2 under the Intergovernmental Panel on Climate Change B1 emission scenario will decrease the carbonate mineral saturation states by up to 40% by the end of this century, and aragonite will approach undersaturation near the coast.

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