Kara Sea Water Research Articles

Organic Carbon Content in Dissolved and Particulate Forms in Kara Sea Water

Organic Carbon Content in Dissolved and Particulate Forms in Kara Sea Water

Dynamics of Carbonate Characteristics of the Kara Sea Waters in the Late Autumn Season of 2021

Dynamics of Carbonate Characteristics of the Kara Sea Waters in the Late Autumn Season of 2021

Analysis of Entropy of Temperature and Salinity Distribution in Subsurface Layer of the Kara Sea Water Area by Geomatics Methods

In recent years the nature of the Kara Sea is greatly influenced by human economic activity. It is stipulated mainly by extensive development of the Kara Sea coastline and by huge deposits of hydrocarbons on its shelf. An attempt to estimate the entropy of temperature and salinity distribution in subsurface layer of the Kara Sea water area has been made in this study aided by the newest geoinformational methods of study (Quantum GIS Desktop program complex). The computation and cartographic modeling of this problem show that the greatest values of entropy indices are registered within littoral and shelf regions. It can testify to the high diversity of these water areas and it is necessary that special (nature protection) regimes of nature use should be set up.

Freshwater Sources in the Bays of Yuzhnyi Island of the Novaya Zemlya Archipelago According to Isotopic (δD, δ18O) Data

An isotope–geochemical study was performed on the waters of Abrosimov and Stepovoi bays along the southeastern coasts of the Novaya Zemlya Archipelago. The waters considered were freshened by several sources: the continental river runoff, the regional atmospheric precipitation, and the waters supplied from the archipelago. The contributions of these freshwater constituents appeared to be different for surface and subhalocline waters. It was shown that the surface waters were freshened with the local runoff from the archipelago, whereas those situated under the halocline were affected by a mixture of the Ob and Yenisei waters along with thawed riverine ice. The supply of the constituents mentioned into aquatic areas of the bays was determined by the global circulation of the Kara Sea waters freshened in turn with those of the continental runoff as well.

Sources and Mechanisms of Seawater Freshening in Tsivolky and Sedov Bays (Novaya Zemlya Archipelago) Based on Isotope Data (δD and δ18О)

Three-year monitoring (2014–2016) of isotope parameters (δD and δ18О) of water in Sedov and Tsivolky bays (Novaya Zemlya Archipelago) freshened by water of different origin (continental river runoff, atmospheric precipitation, and water supplied from the archipelago) showed that the degrees of freshening and sources of fresh water components were different for water located at different depths. The variability of the δD and δ18О values was characteristic only of surface layer water containing up to 30% freshwater component. In 2015, surface water of Sedov Bay contained Ob River water, whereas water supplied from Novaya Zemlya predominated in Tsivolky Bay. The deep water of both bays showed evidence of freshening by high-latitude atmospheric precipitation. This water might have been transported via the St. Anna and Voronin troughs. The difference in freshening mechanisms of water in Sedov and Tsivolky bays was determined by the different seafloor morphologies and degrees of free exchange with Kara Sea water.

The role of river runoff in the Kara Sea surface layer acidification and carbonate system changes

This study aims to perform the results of the investigation of the Kara Sea carbonate system (CS) changes and the factors that determine it. The important feature of the Kara Sea water structure is strong stratification caused mainly by the Ob’ and Yenisey rivers discharge which is estimated as 81% of the total continental runoff to sea. Occurring climate changes, as an increase in the total volume of the Arctic Ocean water (due to melting of glaciers, sea ice decline and river runoff increase), air temperature and CO2 concentration growth should affect greatly the Kara Sea CS. However, riverine water influence seems to be the main driver of future acidification of the Kara Sea water due to permafrost thawing as it stores a great amount of buried carbon. An increase of carbon (mainly inorganic) flow to the sea will lead to carbonate equilibrium shift, oxidation of organic matter and release of CO2 that ultimately leads to a decrease in pH and therefore acidification. The area of the riverine plume depends on the amount of freshwater flowing into the sea and the conditions of the wind forcing. According to the data from Shirshov Institute cruises within the plume area aragonite saturation is below 1 that shows its state as acidified. Prevalence of pCO2 values in the freshened surface layer over the atmospheric shows that atmospheric carbon dioxide, apparently, cannot serve as the main driver for the acidification of the surface waters of the Kara Sea. At the shallow shelf to the north of the Ob′ Inlet mouth we observe acidification of the whole water column from surface to the bottom layer due to elevated riverine discharge and increase of flowing terrestrial carbon.

Сейсмогеологическая модель палеозой-мезозойских отложений Белоостровского, Скуратовского и Нярмейского лицензионных участков акватории Карского моря по данным сейсморазведки 3D

Сейсмогеологическая модель палеозой-мезозойских отложений Белоостровского, Скуратовского и Нярмейского лицензионных участков акватории Карского моря по данным сейсморазведки 3D

Heavy Metals in Atmospheric Air in the Kara Sea Water Area in September–October 2011

The article presents the results of measurements of Pb, Cd, Cu, Zn, Ni, Co Cr, As, and Fe concentrations in atmospheric aerosols in the surface layer over the Kara Sea. The data were collected on 12 segments of a cruise of the R/V Akademik Mstislav Keldysh in September–October 2011. The trace element contents in atmospheric aerosol samples were determined by atomic absorption spectrometry with electrical and thermal atomization and automatic background correction. The dataset was analyzed in relation to the direction in which air masses moved into the study area; the direction was determined from the reverse motion trajectories of air particles. It is demonstrated that concentrations of pollutants increase in air masses coming off the continent and decrease in air masses coming off the ocean. The enrichment of Arctic aerosols in trace elements is calculated.

Modelling Kara Sea phytoplankton primary production: Development and skill assessment of regional algorithms

Empirical region-specific (RSM), depth-integrated (DIM) and depth-resolved (DRM) primary production models are developed based on data from the Kara Sea during the autumn (September–October 1993, 2007, 2011). The model is validated by using field and satellite (MODIS-Aqua) observations. Our findings suggest that RSM algorithms perform better than non-region-specific algorithms (NRSM) in terms of regression analysis, root-mean-square difference (RMSD) and model efficiency. In general, the RSM and NRSM underestimate or overestimate the in situ water column integrated primary production (IPP) by a factor of 2 and 2.8, respectively. Additionally, our results suggest that the model skill of the RSM increases when the chlorophyll specific carbon fixation rate, efficiency of photosynthesis and photosynthetically available radiation (PAR) are used as input variables. The parameterization of chlorophyll (chl a) vertical profiles is performed in Kara Sea waters with different trophic statuses. Model validation with field data suggests that the DIM and DRM algorithms perform equally (RMSD of 0.29 and 0.31, respectively). No changes in the performance of the DIM and DRM algorithms are observed (RMSD of 0.30 and 0.31, respectively) when satellite-derived chl a, PAR and the diffuse attenuation coefficient (Kd) are applied as input variables.

Isotope parameters (δD, δ18O) and sources of freshwater input to Kara Sea

The isotope characteristics (δD, δ18О) of Kara Sea water were studied for quantitative estimation of freshwater runoff at stations located along transect from Yamal Peninsula to Blagopoluchiya Bay (Novaya Zemlya). Freshwater samples were studied for glaciers (Rose, Serp i Molot) and for Yenisei and Ob estuaries. As a whole, δD and δ18O are higher in glaciers than in river waters. isotope composition of estuarial water from Ob River is δD =–131.4 and δ18O =–17.6‰. Estuarial waters of Yenisei River are characterized by compositions close to those of Ob River (–134.4 and–17.7‰), as well as by isotopically “heavier” compositions (–120.7 and–15.8‰). Waters from studied section of Kara Sea can be product of mixing of freshwater (δD =–119.4, δ18O =–15.5) and seawater (S = 34.9, δD = +1.56, δ18O = +0.25) with a composition close to that of Barents Sea water. isotope parameters of water vary significantly with salinity in surface layer, and Kara Sea waters are desalinated along entire studied transect due to river runoff. concentration of freshwater is 5–10% in main part of water column, and 100 m. maximum contribution of freshwater (>65%) was recorded in surface layer of central part of sea.

Ocean circulation and freshwater pathways in the Arctic Mediterranean based on a combined Nd isotope, REE and oxygen isotope section across Fram Strait

The water masses passing the Fram Strait are mainly responsible for the exchange of heat and freshwater between the Nordic Seas and the Arctic Ocean (the Arctic Mediterranean, AM). Disentangling their exact sources, distribution and mixing, however, is complex. This work provides new insights based on a detailed geochemical tracer inventory including dissolved Nd isotope (εNd), rare earth element (REE) and stable oxygen isotope (δ18O) data along a full water depth section across Fram Strait.We find that Nd isotope and REE distributions in the open AM primarily reflect lateral advection of water masses and their mixing. Seawater-particle interactions exert important control only above the shelf regions, as observed above the NE Greenland Shelf. Advection of northward flowing warm Atlantic Water (AW) is clearly reflected by an εNd signature of −11.7 and a Nd concentration ([Nd]) of 16pmol/kg in the upper ∼500m of the eastern and central Fram Strait. Freshening and cooling of the AW on its way trough the AM are accompanied by a continuous change towards more radiogenic εNd signatures (e.g. −10.4 of dense Arctic Atlantic Water). This mainly reflects mixing with intermediate waters but also admixture of dense Kara Sea waters and Pacific-derived waters. The more radiogenic εNd signatures of the intermediate and deep waters (reaching −9.5) are mainly acquired in the SW Nordic Seas through exchange with basaltic formations of Iceland and CE Greenland. Inputs of Nd from Svalbard are not observed and surface waters and Nd on the Svalbard shelf originate from the Barents Sea. Shallow southward flowing Arctic-derived waters (<200m) form the core of the East Greenland Current above the Greenland slope and can be traced by their relatively radiogenic εNd (reaching −8.8) and elevated [Nd] (21–29pmol/kg). These properties are used together with δ18O and standard hydrographic tracers to define the proportions of Pacific-derived (<∼30% based on Nd isotopes) and Atlantic-derived waters, as well as of river waters (<∼8%). Shallow waters (<150m) on the NE Greenland Shelf share some characteristics of Arctic-derived waters, but exhibit less radiogenic εNd values (reaching −12.4) and higher [Nd] (up to 38pmol/kg) in the upper ∼100m. This suggests local addition of Greenland freshwater of up to ∼6%. In addition to these observations, this study shows that the pronounced gradients in εNd signatures and REE characteristics in the upper water column provide a reliable basis for assessments of shallow hydrological changes within the AM.

Shelf basin exchange along the Siberian continental margin: Modification of Atlantic Water and Lower Halocline Water

Salinity and stable oxygen isotope (δ18O) evidence shows a modification of Atlantic Water in the Arctic Ocean by a mixture of sea-ice meltwater and meteoric waters along the Barents Sea continental margin. On average no further influence of meteoric waters is detectable within the core of the Atlantic Water east of the Kara Sea as indicated by constant δ18O, while salinity further decreases along the Siberian continental slope.Lower Halocline Waters (LHW) may be divided into different types by Principal Component Analysis. All LHW types show the addition of river water and an influence of sea-ice formation to a varying extent. The geographical distribution of LHW types suggest that the high salinity type of LHW forms in the Barents and Kara seas, while other LHW types are formed either in the northwestern Laptev Sea or from southeastern Kara Sea waters that enter the northwestern Laptev Sea through Vilkitsky Strait. No further modification of LHW is seen in the eastern Laptev Sea but the distribution of LHW-types suggest a bifurcation of LHW at this location, possibly with one branch continuing along the continental margin and a second branch along the Lomonosov Ridge. We see no pronounced distinction between onshore and offshore LHW types, as the LHW components that are found within the halocline over the basin also show a narrow bottom-bound distribution at the continental slope that is consistent with a shelf boundary current as well as a jet of water entering the western Laptev Sea from the Kara Sea through Vilkitsky Strait.

Geochemical signature of bottom sediments in the mixing zones of Ob and Yenisei waters with Kara Sea water

This paper reports the results of a study of the geochemistry of bottom sediments from the zones of mixing between the freshwater of the Ob and Yenisei rivers and the saline water of the Kara Sea by means of neutron activation analysis. Using separate datasets for the sediments of the Ob and Yenisei estuaries accumulated under identical facies conditions, some characteristic features of the distribution of a number of chemical elements (mostly lithophile group elements) were established. The differences between them were attributed to distinctive regional geological and geochemical features of the catchments of the Ob and Yenisei, which are inherited by the geochemical characteristics of terrigenous material transported to the sea. The choice of the most informative indicator elements and their grouping on the basis of the character of behavior demonstrated that bottom sediments of the Ob or Yenisei origin can be identified in the marine region studied using the geochemical characteristics of a small group of samples.

Spatiotemporal variability of the organic matter and the rates of its transformation in the Ob Inlet

The data on the qualitative and quantitative variability of the organic matter (OM) and its transformation rates in the waters of the Ob Inlet during different seasons are considered. The OM distribution was quite nonuniform over the entire Ob Inlet aquatic area: the concentrations of Corg varied from 2.8 to 14.1 mg/L and from 0.32 to 4.59 mg/L for the dissolved and particulate forms, respectively. The maximum concentrations of dissolved OM were registered in the main flow of the Ob River water supplied to the bay, whereas the minimum concentrations were characteristic for the near-bottom layers formed by the Kara Sea waters of high salinity in the northern part of the bay. Both in the summer and in the autumn, the fraction of particulate matter within the total OM reached its maximum values in the mixing zone of the Taz and Ob riverine waters, as well as in the mixing zone of the Ob River and Kara Sea waters. These boundary zones were characterized by the widest variability of the elemental (C: N: P) and biochemical (proteins and carbohydrates) composition of the OM, as well as of its transformation rates measured by the activities of the enzymes (alkaline phosphatase and the electron transport system).

Optical characteristics of the Kara Sea derived from shipborne and satellite data

Results of optical studies of the Kara Sea waters are considered. The data of ship borne measurements are compared with satellite observations. The maximum values of the beam attenuation coefficient, the chlorophyll, and the yellow substance fluorescence were observed in the Ob gulf and in the coastal waters west of the Yamal Peninsula. The minimum values were observed in the central and western parts of the Kara Sea. Frontal zones with sharp changes of the parameters involved were observed. The distribution of the seawater’s optical characteristics was closely related to the hydrological structure of the Kara Sea’s waters. The data of the shipborne measurements were consistent with the satellite observations.

Natural background of hydrocarbon gases (C1–C5) in the waters of the Kara Sea

The distributions of methane and hydrocarbons (HC) C2+ throughout the vertical section of the water mass and sediments of the Kara Sea and the estuaries of the Ob and Yenisei rivers were examine during expeditions aboard the R/V “Akademik Boris Petrov” in 1997–2002. Data obtained during the expeditions and extensive information provided by the complex study of the carbon cycle in the aquatic area were used to analyze the genesis of hydrocarbon gases in marine water. The example of particulate matter was used to demonstrate that hydrocarbon gases of the composition C2–C5 contained in seawater are genetically related to aquatic organic matter (OM), regardless of seawater salinity. The hydrocarbon complex is dominated (80%) by higher C4–C5 homologues. The concentration of C4–C5 hydrocarbons in the estuarine fresh waters is comparable with the high methane concentration (2–3 μl/l), drastically decreases in the zone of water mixing, and then rapidly increases to values several times higher than the methane concentration in seawater outside the outer boundary of the sedimentation depocenter of riverine particulate matter. A direct correlation was established for the concentration of the C4 + C5 homologues with the OM of the water mass, and the leading role was demonstrated to be played by labile OM of the autochthonous biomass (marine phytoplankton) in the genesis of higher hydrocarbon gases (alkenes, alkanes, and isoalkanes) during the early diagenetic stage of OM transformations in water. Along with the biomass of phytoplankton, a significant role in the genesis of C2–C3 hydrocarbons is played by destruction products of terrigenous OM. The destruction of OM and generation of gaseous hydrocarbons, including methane, are restricted to the pycnocline and the water-sediment interface. The absolute predominance of the sum of the C4 + C5 homologues in the hydrocarbon C2+ gases and the presence of unsaturated C2–C4 hydrocarbons are typical of the natural background of hydrocarbons of the Kara Sea water mass.

228Ra and 226Ra in the Kara and Laptev seas

The surface water in the Transpolar Drift in the Arctic Ocean has a strong signature of 228Ra. In an earlier study of 228Ra in the open Arctic we showed that the major 228Ra source had to be in the Siberian shelf seas, but only a single shelf station was published so far. Here we investigate the sources of this signal on the Siberian shelves by measurements of 228Ra and 226Ra in surface waters of the Kara and Laptev Sea, including the Ob, Yenisey and Lena estuaries. In the Ob and Lena rivers we found an indication for a very strong and unexpected removal of both isotopes in the early stage of estuarine mixing, presumably related to flocculation of organic-rich material. Whereas 226Ra behaves conservatively on the shelf, the distribution of 228Ra is governed by large inputs on the shelves, although sources are highly variable. In the Kara Sea the maximum activity was found in the Baydaratskaya Bay, where tidal resonance and low freshwater supply favour 228Ra accumulation. The Laptev Sea is a stronger source for 228Ra than the Kara Sea. Since a large part of Kara Sea water flows through the Laptev Sea, the 228Ra signal in the Transpolar Drift can be described as originating on the Laptev shelf. The combined freshwater inputs from the Eurasian shelves thus produce a common radium signature with a 228Ra/ 226Ra activity ratio of 4.0 at 20% river water. The radium signals of the individual Siberian rivers and shelves cannot be separated, but their signal is significantly different from the signal produced on the Canadian shelf (Smith et al., in press). In this respect, the radium tracers add to the information given by Barium. Moreover, with the 5.8 year half-life of 228Ra, they have the potential to serve as a tracer for the age of a water mass since its contact with the shelves.