I. I. Pipko

The Dispersion of Siberian River Flows into Coastal Waters: Meteorological, Hydrological and Hydrochemical Aspects

Global effects on the Arctic are reflected in regional climate changes and their impacts and consequences. Essentially all cryospheric features of the Arctic will be affected in one way or another. Energy and water fluxes clearly shape the regional temperature regime, which is a primary factor in determining the surface state (frozen vs. thawed), trace gas fluxes, rates of productivity, and the link to regional climate [1,2].

Carbonate chemistry dynamics in Bering Strait and the Chukchi Sea

Fall dynamics of the carbonate system in the shallow Chukchi Sea is a result of the interaction between physical and biological processes such as mixing of different water masses, cooling, photosynthesis-respiration. The study area acts as a sink for atmospheric CO2. The general trend in surface pCO2 distribution is a decrease towards the ice edge, which is determined by the temperature decrease, whereas mesoscale variability of the carbonate parameters is controlled by the interaction between different waters. The calculated September 1996 flux of CO2 from the air into the sea on eastern Chukchi Sea is about 1×1012 g C.

On carbon transport and fate in the East Siberian Arctic land?shelf?atmosphere system

This review paper summarizes current understanding of the transport of organic carbon to, and the fate of organic carbon within, the East Siberian Arctic Shelf (ESAS), and of processes determining carbon dioxide (CO2) and methane (CH4) fluxes from the ESAS to the atmosphere achieved from analyzing the data sets obtained on 20 expeditions performed from 1999 to 2011. This study of the ESAS was aimed at investigating how redistribution of old carbon from degrading terrestrial and sub-sea permafrost and from coastal erosion contributes to the carbon pool of the ESAS, how changes in the hydrological cycle of the surrounding land and alteration of terrestrial carbon cycles affect the hydrological and biogeochemical parameters of shelf water masses, and which factors control CH4 and CO2 emissions from the ESAS. This report describes selected results achieved by a developing international scientific partnership that has been crucial at every stage of the study and will be even more important in the future.

Variability of the carbonate system parameters in the coast-shelf zone of the East Siberian Sea during the autumn season

The publication presents the results of the studies on the carbonate system of the waters of the East Siberian Sea performed aboard R/V Ivan Kireev in September 2003–2004. It is shown that the aquatic area considered may be subdivided into two biohydrochemical provinces. The western part of the sea is a CO2 supplier to the atmosphere, while its eastern part is a sink for CO2. This is caused by the fact that the western part of the East Siberian Sea was affected by the waters of the southeastern part of the Laptev Sea, which were desalinated by riverine runoff, turbid, and enriched in the bioactive organic matter supplied into the water due to the coastal (and bottom) erosion. In the eastern part, cold waters of Pacific origin prevailed (saline, transparent, and productive), which caused a pronounced decrease in the partial pressure of CO2(pCO2) in the surface layer. In the frontal zone delimiting the desalinated shelf waters and those of the Pacific origin, the direction of the CO2 flux between the atmosphere and the sea changed (from evasion to invasion). The interannual variability of the carbonate system parameters in the coastal-shelf zone of the East Siberian Sea was determined by the intensity of the propagation of the waters of different origins over the sea aquatic area caused by the atmospheric circulation, as well as by the riverine runoff intensity and the dynamics of erosion processes.

Carbonate characteristics of waters of the Arctic Ocean continental slope

Carbonate characteristics of the water mass of the deepwater part of the Arctic Ocean (AO) in the continental slope area were determined, and the range and reasons of their variability during summer-fall season were revealed. The AO water area is a meaningful sink for atmospheric carbon dioxide. The warm intermediate Atlantic waters (AW) are also undersaturated with carbon dioxide relative to its content in the atmosphere. While these waters move along AO continental slope, the value pCO2 in the AW core decreases to 8–10 μatm (mainly, due to drop in the water temperature). The potential absorption capacity of the AO deepwater basin is estimated at approximately 48 Tg of carbon (without sea ice taken into account). Joint analysis of carbonate and hydrological parameters showed that near-bottom waters formed on the shallow shelf of the Laptev Sea, which is rich in inorganic and organic carbon of terrestrial and marine genesis, take part in formation of halocline waters of the AO. They are modified due to interaction with AW penetrating to the shelf and are transferred to the deepwater AO segment, where they occur in the halocline according to their density. Transformed near-bottom waters of the Laptev Sea shelf, similar to waters of the halocline of Pacific origin in the eastern sector of the AO, are traced above the continental slope in Amundsen Basin on the basis of higher CO2 concentrations.

Comparison of calculated and measured CO2 fluxes between the ocean and atmosphere in the southwestern part of the East Siberia Sea

The interaction between the degradation of land and underwater permafrost, which is a storage of enormous resources of organic matter [1, 2], and the emission of the final product of its decomposition ( CO 2 ) into the atmosphere is of special interest in global warming manifested most strongly in the Arctic region. Insufficient attention has been paid thus far to investigation of the carbonate system in the seas of the Eastern Arctic with the widest and shallowest shelf in the World Ocean. Previously, it was commonly accepted that the Arctic seas serve as sinks of atmospheric CO 2 [3] in the summer‐autumn period due to low water temperature and high seasonal productivity. However, our previous investigations demonstrated that the southwestern part of the East Siberia Sea (ESS) is an important source of carbon dioxide for the atmosphere in summer. It is assumed that high partial CO 2 pressure is formed due to the influence of the river discharge and destruction of labile organic matter transported to seawater as a result of the destruction of the coastal ice complex [2‐6]. Up to the present time, there is no commonly accepted opinion about the preference of applying one or another method for calculating CO 2 fluxes in the ocean‐atmosphere system, in particular, in the polar regions. Based on the study of the ESS, this work presents the first results of the comparison of calculated values obtained by different algorithms with the fluxes measured by the micrometeorological method. The optimal method for calculating the CO 2 fluxes in the ocean‐atmosphere system is chosen for the study region. This work is based on the materials of the expedition in the southwestern ESS in September 2005 (Fig. 1). In these expeditions, CO 2 fluxes between the ocean and the atmosphere in the eastern arctic region were measured synchronously and calculated for the first time. The methods of measurements and calculation of elements of the carbonate system and the CO 2 fluxes between seawater and the atmosphere are described in detail in [5]. The mean CO 2 concentration in the atmosphere (372 µ atm), hourly and daily mean wind velocities ( U ) at a height of 10 m, and quadratic and cubic dependence of gas transport ( k ) on wind velocity were used in the calculations [7, 8]. The peculiarities of the micrometeorological method of measuring CO 2 fluxes are described in [6, 9].

Optical characteristics of the colored dissolved organic matter on the East Siberian shelf

This work is based on the results of a cruise of the R/V Akademik Lavrent’ev in September 2011 in the Laptev and East Siberian seas. The optical characteristics of one of the most characteristic components of the river runoff colored dissolved organic matter (CDOM), which intensely absorbs solar radiation in the short-wave spectrum range are analyzed. On the basis of experimental data, the possibility to use spectral characteristic not only for quantitative estimations but also for determination of the DOM composition in the waters of the East Siberian shelf is shown.

The autumn distribution of the CO2 partial pressure in bottom waters of the East Siberian Sea

Climate changes in the Arctic region result in transformation of atmospheric circulation, degradation of the ice cover, and a reduced “ice free” season, which stimulates processes in the land‐sea and lithosphere‐ hydrosphere‐atmosphere systems. It is thought that these processes influence substantially the carbon cycle in the Arctic seas. Serving as a connecting link between terrestrial, oceanic, and atmospheric carbon reservoirs, the coastal zone of shelf seas plays an important role in the carbon cycle. The main agents supplying allochthonous carbon to the Arctic shelf are rivers as well as a degrading coastal (and subaqueous) ice complex that contains fossil labile organic matter The East Siberian Sea is characterized by the shortest (among Arctic seas) shoreline (3500 km), although it receives the maximal (for the Arctic shelf) volume of terrigenous organic carbon (2.2 × 10 6 t C/year) [1]. In this area alone, this value exceeds the contribution of its river influx (1.86 × 10 6 t C/year). Rivers transport organic carbon to the shelf mainly in dissolved form, which is more resistant to biodestruction as compared with carbon buried in the coastal ice complex; the latter is labile being involved in the recent biochemical cycle [2‐5]. This is primarily reflected in the distribution of the carbon dioxide partial pressure ( p ee 2 ), the most changeable parameter of the carbonate system, in the water column. As was shown [6], the surface layer generally in the open part of the East Siberian Sea represents a major source of carbon dioxide for the atmosphere. Nevertheless, the dynamics of parameters in the carbonate system of bottom waters in the Arctic seas remain poorly studied so far. The purpose of this work is study of the factors that are responsible for the formation of CO 2 partial pressure fields in the bottom layer of shallow shelf waters in the East Siberian Sea representing a potential source of this greenhouse gas for the atmosphere. The analysis of carbonate system dynamics in bottom waters of the coastal‐shelf zone in the East Sibe

Assessment of the CO2 fluxes between the ocean and the atmosphere in the eastern part of the Laptev Sea in the ice-free period

The carbonate system of waters of the inner, middle, and outer shelves was studied for a long period in the eastern part of the Laptev Sea. It is shown that the inner and middle shelves is a heterotrophic province and is a source of CO2 to the atmosphere during August–September. The average CO2 flux is 7.9 mmol m–2 day–1 and during one month waters of inner and middle shelves release into the atmosphere up to 0.7 Tg of carbon (C). The outer part of the shelf absorbs up to ~0.1 Tg C at an average rate of 3.9 mmol m–2 day–1 during the month. Generally, the ice-free zone of the eastern shelf of the Laptev Sea is a source of CO2 in the studied season: the amount of C released into the atmosphere within a month is ~0.6 Tg.

Characteristic features of the dynamics of carbonate parameters in the eastern part of the Laptev Sea

This report presents the results of studies of the sea water carbonate system performed in September 2011 at the inner, middle, and outer shelf of the east of the Laptev Sea. It was shown that the key factor controlling the carbonate chemistry of the shelf waters during the warm season is the significant terrigenous runoff. In the autumn season, the surface waters of the inner and middle shelf of the eastern part of the Laptev Sea are a source of carbon dioxide to the atmosphere; those of the outer shelf act as a sink of atmospheric CO2. It is found that the waters of the inner shelf of the east of the Laptev Sea over the entire water column are now corrosive against calcium carbonate. The surface and near-bottom waters of the middle shelf are also undersaturated with respect to aragonite. It was shown that the main factors determining the undersaturation are the significant volume of freshwaters supplied with the riverine runoff and the ice melting, as well as the large amount of labile allochthonous organic matter involved into the modern biogeochemical cycle at the shelf. The performed studies showed that the shelf waters of the eastern part of the Laptev Sea constitute one of the most corrosive zones with respect to calcium carbonate in the World Ocean.