Carbon Cycle in the Russian Arctic Seas

Studies of carbon cycling in the Arctic Seas of Russia (ASR) are carried out under the Russian State Scientific Program “Global Changes of the Natural Environment and Climate,” the Federal Program “World Ocean,” and International bilateral and multilateral agreements (Russian-French, Russian-German, and others).

The role of the Arctic Ocean and its seas in the formation of the climate of the World Ocean and the climate of the Earth is extremely important. They operate as a refrigerator of the oceanic heat machine and an energy source for the Arctic atmosphere. Being located at the interface between the climatic zones of the permafrost and of the all-the-year-round heating, the ASR represent one of the most nonequilibrium dynamical systems. In this system, scenarios of the adjacent sea areas are alternately implemented and, in addition, one can observe phenomena peculiar to transient processes only.

In the global carbon cycle of the biosphere, photosynthesis in the ocean occupies the most important place. It accomplishes the conversion of carbon from the mineral to organic form and provides the energy for the subsequent heterotrophic levels of the existence of life. Using carbon dioxide (its hydrocarbonate forms) as the main initial component, it shows itself as a powerful factor damping the consequences of the growth in the CO₂ content in the atmosphere and the greenhouse effect. Greater than four billion years ago, precisely the photosynthesis of unicellular algae in the ocean initiated transformation of the non-oxygen atmosphere of the Earth into the present-day atmosphere with a low content of CO₂ and a high content of oxygen (Yanshin 1997).

Commonly, the particulate matter (PM) is defined as the part of the suspended matter which is retained on filters with a pore size of 0.45–1 µm. It includes particulate OM as one of the most mobile and reactive components. At present, several methods for separation and evaluation of the distribution and fluxes of particulate matter are applied. Among them, we can note water filtration through the so-called nuclepore filters (organic polymer films with a pore diameter of 0.45 µm), which are used to determine the concentrations of particulate matter and metals; glass fiber filters preliminary calcinated at a temperature of 450°C and applicable for the determination of C, N, P, and composition of organic matter; sediment traps of various sizes and designs; and the “Flax-camera” and “Survey-camera” systems. The latter performs continuous-discrete measurements of the particle spectra, their sizes and amounts in the water column, while the flaxcamera is installed on the bottom as a sediment trap and shoots from beneath the process of particulate matter accumulation. A special place in these studies belongs to the technology of the observations of particulate matter from underwater manned submersibles such as the Mir, Pisces, and Argus; In addition, optical methods for particulate matter examination are applied. The high efficiency of the use of the optical methods is caused by the continuous-discrete character of the measurements and express mode of data acquisition over space and time. The degree of the light attenuation is closely related to the particulate matter concentration, which allows one to reveal the features of the horizontal and vertical structure of the field of particulate matter, especially when the optical measurements are accompanied by direct particulate matter determinations with the filtration methods providing a possibility to construct regional algorithms linking these parameters.

The estimation of the values of riverine runoff, sediment (particulate matter) runoff, that of carbon and other nutrients, the more so of their mean annual values represents a difficult task. Under the severe conditions of the Arctic, the difficulties increase manifold. This is related to a series of reasons, among which the principal, in a to the severe climatic conditions, are the strong spatiotemporal variability of the runoff intensity and its composition under the influence of various natural and anthropogenic factors, nonlinear and variable in time (Naidenov and Shveikina 1999; Savel’eva et al. 2000; Holmes et al. 2002). This determines the importance of development of nonlinear dynamical models (for example, for the surface and underground runoff) and the necessity of availability of series of instrumental observations in different seasons obtained with modern intercalibrated facilities or, at least, following compatible techniques. At present, there are no commonly accepted methods for monitoring, which could be applied at the existing gauging stations; this interannual an additional factor complicating the estimates of the mean values of water runoff and its composition. Along with this, the climatic change predicted to occur in the 21st century should first affect the runoff of the Arctic rivers and, in this regard, the importance of the evaluation of the water runoff and its composition still more increases (Gramberg et al. 2000; Houghton et al. 2001; Mogilevkin et al. 2002).

The burial and accumulation of carbon in the bottom sediments represents the final link in its turnover in the upper part of the biosphere. Subsequently to this stage, carbon is transformed within the geological cycling (katagenesis, metamorphism) and tens million of years pass before its reimbursement back to the upper spheres of the earth, ocean, and atmosphere.

In this chapter, we assess the parameters of the organic and carbonate carbon cycles in the system, namely primary photosynthetic production, carbon supply from land, exchange with adjacent basins, decomposition to CO₂ in the water column and on the floor surface, and its burial in the bottom sediments. These parameters represent the fluxes of the organic carbon participating in the cycle, its masses removed from the cycling, and the equivalent amount of O₂ released into the atmosphere. The estimates are mainly based on the analysis of the data presented in the previous chapters (Figs. 7.1, 7.2, and 7.3).