Dissolved Inorganic Carbon in the Estuarine Area of the Lena River: Results of Expeditions in 2015 and 2017

Abstract

Transects near the estuarine area of the Lena River were studied on cruises 63 and 69 of the R/V Akademik Mstislav Keldysh, organized by the Institute of Oceanology, Russian Academy of Sciences, in 2015 and 2017, the program of which included hydrochemical studies. Based on the results, the components of the carbonate system were calculated, and their dynamics was studied in sea–river mixing zone. Despite the general similarity in the distribution of hydrochemical parameters, the patterns of variations in the content of dissolved inorganic carbon along the river–sea mixing line in 2015 and 2017 were significantly different. In 2015, the increase in the content of dissolved inorganic carbon along the river–sea mixing line was higher than can be provided by the oxidation of organic matter. In 2017, almost the entire influx of dissolved inorganic carbon into water could be controlled by the destruction of dissolved and/or particulate organic matter. The difference in the state of components of the carbonate equilibrium of waters and their dynamics may be the result of significantly higher runoff of particulate matter from the Lena River in 2015 than that in 2017.