Variations in the isotopic composition of particulate organic carbon and their relation with carbon dynamics in the western Arctic Ocean

The relation between the dissolved carbon dioxide (CO2) and the stable isotopic composition of particulate organic matter in the water column has not been well quantified, but this information could help provide a better understanding of carbon dynamics in a warmer Arctic Ocean. The stable carbon isotopic composition of suspended particulate organic carbon (delta C-13(POC)) in the surface waters of the western Arctic Ocean was measured during July September 2003, to evaluate the spatial variability of delta C-13(POC) and its key controlling factors. Values of delta C-13(POC) fell within the range of -28.5 parts per thousand to -21.1 parts per thousand, with an average of -24.5 +/- 2.3 parts per thousand. The spatial variability of delta C-13(POC) showed a general decreasing trend from shallow waters in the continental shelf toward the deeper, colder waters in the basin. A negative correlation between delta C-13(POC) and the dissolved CO2 concentration in surface waters was observed, indicating that carbon isotopic fractionation during photosynthesis was largely dependent on the dissolved CO2 concentration. Compared to the solubility pump, biological processes may play a more important role in determining the distribution and variation of delta C-13(POC) in the western Arctic Ocean during summer. The coupled relationship between CO2 concentration and stable isotopic composition of particulate organic matter has the potential to be used for reconstruction of sea-surface CO2 changes in the past, provided a quantitative relationship of delta C-13 between POC and sediments can be established. (C) 2011 Elsevier Ltd. All rights reserved.