INFLUENCE OF THE CONTINENTAL RUNOFF ON THE BIOGEOCHEMICAL STRUCTURE OF THE KARA SEA SURFACE LAYER in 2021
Authors: Kazakova Uliana , Polukhin Alexander , Kostyleva Anna , Pronina Julia , Yakushev Evgeniy , Osadchiev Alexander 
Published: March 2022

&lt;p&gt;A large volume of river runoff influences the Kara Sea annually. The water masses coming from estuaries form a surface desalinated layer, which propagates under the influence of the wind forcing. A water during the melting of sea ice contributes to the desalination of the surface layer as well. At the end of the summer period of 2021, the presence of ice cover was observed in the northern and northeastern parts of the Kara Sea. The hydrological regime of rivers at the end of the summer period is characterized by a decrease in water consumption and, accordingly, a small volume of incoming river runoff.&lt;/p&gt;&lt;p&gt;Together with the fresh waters of the Ob, Yenisei and other rivers, various nutrients are transported into the sea. A part of nutrients is deposited in the estuaries of the Ob and Yenisei gulfs within the frontal zone. The other part is carried out to the open sea and serves as the basis for the activity of marine organisms in coastal ecosystems. The observed climatic changes in the Arctic affect the change in the distribution of parameters of the carbonate system, which, in turn, affects the marine ecosystem.&lt;/p&gt;&lt;p&gt;The main purpose of the work is to analyze the temporal and spatial variability of the hydrochemical structure and carbonate parameters at the end of the summer period of 2021.&lt;/p&gt;&lt;p&gt;The work uses the data obtained during the 58th cruise of the RV &quot;Academik Ioffe&quot; in august 2021 and the 86th cruise of the RV &quot;Academik Mstislav Keldysh&quot; to the Kara Sea in October 2021. The hydrochemical parameters that were determined included biogenic elements, dissolved oxygen, pH of hydrogen, alkalinity and components of the carbonate system.&lt;/p&gt;&lt;p&gt;Several groups of parameters are identified depending on the nature of the distribution of biogeochemical values in the water column of the Kara Sea. These groups include parameters that clearly mark the influence of river runoff, parameters in the distribution of which extremes in the frontal zone are distinguished, and parameters characterized by heterogeneity of distribution in the zone of mixing of fresh and marine waters.&lt;/p&gt;&lt;p&gt;The hydrochemical structure was characterized by great temporal and spatial variability associated with the influence of hydrological, meteorological and hydrobiological factors.&lt;/p&gt;&lt;p&gt;The temporal variability of biogeochemical parameters at the end of the summer period is considered. The change in the hydrogen pH index during the period under review is characterized by a decrease in the range of values. In august, the pH varied in the range of 7.5-8.5, in November - from 7.5 to 7.9. The partial pressure of carbon dioxide in August ranged from 136 ppm to 1260 ppm, in October - from 267 ppm to 850 ppm. The aragonite saturation varies from 0.07 to 2.4 in august and 0.2-1.75 in November.&lt;/p&gt;&lt;p&gt;The research is implemented in the framework of the state assignment of the Shirshov Institute of Oceanology (theme No. 0128-2021-0007), with the support of the Russian Scientific Foundation (project &amp;#8470; 19-17-00196) and the grant of the President of Russian Federation &amp;#8470; &amp;#1052;&amp;#1050;-3506.2022.1.5&lt;/p&gt;