Southwestern Kara Sea Research Articles

The influence of heavy shipping traffic on the structure and dynamics of sea ice in the southwestern Kara Sea

The development of the Northern Sea Route and the beginning of year-round transit shipping require not only the production of new icebreakers and ice-class vessels, but also the development of a specialized hydrometeorological support system for ice shipping. For the analysis of satellite data and the development and validation of ice forecasts, actual field data on the ice cover is required. This data can only be obtained from shipboard observations; however, scientific expeditions are rarely organized during the winter. In order to obtain new data over the area of intensive shipping, two expeditions were organized on board of nuclear icebreakers in the southwestern Kara Sea (“LED-SMP” expeditions) in 2023 and 2024. Specialized hydrometeorological maintenance of ice shipping in the southwestern Kara Sea together with the research expeditions “LED-SMP” carried out in the same place and time on board the nuclear icebreakers revealed the influence of the technogenic factor on the sea ice structure and dynamics was revealed. In winter and spring, two main routes are used for navigation in the southwestern Kara Sea: through the Kara Gate Strait and north of Cape Zhelaniya. In April 2024, a unique situation occurred when, due to the difficult ice conditions east of the Kara Gate Strait, the entire ship traffic was directed north of Cape Zhelaniya. In preparing a long-term ice forecast, it was noted that after the redirection the natural development of ice processes changed. At the beginning of the winter period 2024,

Lithological and mineralogical characteristic of the bottom sediments in the areas of ice scouring in the south-western Kara Sea

Lithological and mineralogical characteristic of the bottom sediments in the areas of ice scouring in the south-western Kara Sea

Morphometry of Ice Scours in the Southwestern Kara Sea

Morphometry of Ice Scours in the Southwestern Kara Sea

Phytoplankton Communities in the Southeastern Barents Sea and the Southwestern Kara Sea as Indicators of the Phytogeographic Status of These Regions

Phytoplankton Communities in the Southeastern Barents Sea and the Southwestern Kara Sea as Indicators of the Phytogeographic Status of These Regions

Structure and Productivity of the Phytoplankton Community in the Southwestern Kara Sea in Early Summer

Knowledge of the features of the structure and productivity of the Arctic communities of marine planktonic algae is necessary to identify possible changes in the pelagic ecosystem functioning under the changing climate condition of the Kara Sea. This study shows that the species diversity, abundance of phytoplankton, and production activity of algae are at a maximum at the beginning of summer during a seasonal ice melting period. The studies were carried out in the southwestern Kara Sea and in the estuarine zone of the Ob and Yenisei rivers from 29 June to 15 July 2018. The concentrations of nutrients and dissolved organic carbon were determined. The optical properties of chromophoric dissolved organic matter, species composition, abundance and biomass of all size groups of phototrophic and heterotrophic phytoplankton, and parameters of primary production and potential photosynthetic capacity were considered. Statistical data analysis showed that the leading factors influencing changes in the abundance of phytoplankton and its productivity are the content of silicates and salinity. At the same time, the production potential of algae is realized as short-lived and small phytoplankton assemblages differed in number taxa and diversity, with an equally rapid decrease in photosynthetic activity. Such changes affect the Marine Zone to a greater extent and the Estuarine Zone to a lesser extent.

Community Structure and Abiotic Characteristics of Pelagic Microalgal in Adjacent Areas of the Barents Sea and Kara Sea

This study aimed to confirm the hypothesis of a floristic identity between the southeastern Barents Sea and the southwestern Kara Sea. We conducted integrated studies of pelagic microalgae communities including microscope cell counting and taxonomical identification as well as photosynthetic pigments determination and defining of hydrological and hydrochemical characteristics during a cruise in late August and the first half of September 2020. As far as we are concerned, no such observations had been carried out in this region at this time of the year before. During our observations, 35 species were identified, 14 (40%) of which were present in both water bodies. The communities of both regions were in a state corresponding to the autumn stage of the annual succession cycle. In the southeastern Barents Sea, the mean abundance of organisms in the water column varied from 10.650 to 41.840 cells per liter with a biomass of 71.04 to 300.55 µg/L. In the southwestern Kara Sea, these values were 3.510–28.420 cell/L and 16.31–66.96 µg/L, respectively. In general, the results of a comparative analysis suggest that the pelagic algal communities in the regions under comparison, despite the difference in hydrological parameters, demonstrate similar qualitative and quantitative characteristics and thus may belong to the same phytogeographic region.

Structure and productivity of the phytoplankton community in the southwestern Kara Sea in early summer

As a result of research conducted in July 2018 in the southwestern part of the Kara Sea, it was revealed that during the period of the beginning of the seasonal ice shift, the pelagic phytocen was at the stage of ice/marginal bloom, which was realized within a single spatiotemporal field. Distinctive features of the organization of the community of pelagic microalgae were a characteristic set of dominants and a mosaic structure of the pelagial. The mosaic pattern of marine phytoplankton is determined by the interaction between physical environmental factors and the biological activity of microalgae populations. In this case, the pelagic phytocene was a network of short-lived basins limited by local frontal sections with the predominant development of individual species/species complexes against the background of the functioning of the basic cluster of early spring cryophilic diatoms.

Current state of macrobenthos in the southwestern Kara Sea

The study of the bottom biota of the Kara Sea has been going on for over 100 years. Since the 1990s, the interest to ecosystems of the Sea has increased due to the growth of anthropogenic impact, namely, the intensification of the oil and gas field development in the shelf zone. Up to date, the recent survey is the most detailed and extensive investigation of the macrobenthos (for the entire observation period) in the southwestern Kara Sea. Macrobenthic distribution was assessed at 119 stations at depths ranging from 4 to 415 m in August–September 2012–2013. The results obtained allow suggesting the absence of serious changes in macrobenthos structure in the study area for last 80–90 years. Despite the differences in sampling methods and data processing, the main trends noted in the macrobenthic distribution in 2012–2013 were similar to those noted before. The identified abiotic factors most significant for distribution of benthic organisms - salinity, depth, sediment characteristics - were the same as reported in previous researches. Apparently, the state of macrobenthos in the study area at the beginning of the 21st century was close to the long-term norm. The presented data can be used as a reference point when tracking future ecosystem changes and possible consequences of anthropogenic and natural impacts.

The Role of Thermal Denudation in Erosion of Ice-Rich Permafrost Coasts in an Enclosed Bay (Gulf of Kruzenstern, Western Yamal, Russia)

Coastal erosion in the Arctic has numerous internal and external environmental drivers. Internal drivers include sediment composition, permafrost properties and exposure which contribute to its spatial variability, while changing hydrometeorological conditions act as external drivers and determine the temporal evolution of shoreline retreat. To reveal the relative role of these factors, we investigated patterns of coastal dynamics in an enclosed bay in the southwestern Kara Sea, Russia, namely the Gulf of Kruzenstern, which is protected from open-sea waves by the Sharapovy Koshki Islands. Using multitemporal satellite imagery, we calculated decadal-scale retreat rates for erosional segments of the coastal plain from 1964 to 2019. In the field, we studied and described Quaternary sediments and massive ground-ice beds outcropping in the coastal bluffs. Using data from regional hydrometeorological stations and climate reanalysis (ERA), we estimated changes in the air thawing index, sea ice-free period duration, wind-wave energy and total hydrometeorological stress for the Gulf of Kruzenstern, and compared it to Kharasavey and Marre-Sale open-sea segments north and south of the gulf to understand how the hydrometeorological forcing changes in an enclosed bay. The calculated average shoreline retreat rates along the Gulf in 1964–2010 were 0.5 ± 0.2 m yr−1; the highest erosion of up to 1.7 ± 0.2 m yr−1 was typical for segments containing outcrops of massive ground-ice beds and facing to the northwest. These retreat rates, driven by intensive thermal denudation, are comparable to long-term rates measured along open-sea sites known from literature. As a result of recent air temperature and sea ice-free period increases, average erosion rates rose to 0.9 ± 0.7 m yr−1 in 2010–2019, with extremes of up to 2.4 ± 0.7 m yr−1. The increased mean decadal-scale erosion rates were also associated with higher spatial variability in erosion patterns. Analysis of the air thawing index, wave energy potential and their total effect showed that inside the Gulf of Kruzenstern, 85% of coastal erosion is attributable to thermal denudation associated with the air thawing index, if we suppose that at open-sea locations, the input of wave energy and air thawing index is equal. Our findings highlight the importance of permafrost degradation and thermal denudation on increases in ice-rich permafrost bluff erosion in the Arctic.

Statistical results of the numerical model of sea ice drift extremes in the south-western part of the Kara Sea

The aim of the study was to identify the basic characteristics of ice drift in the south-western Kara Sea and to estimate the extreme drift speed of given probability, including its spatial variability and statistical correlation with the main drift-forming factors. In order to obtain the ice drift data, the numerical dynamic-thermodynamic model of ice cover evolution developed in AARI was used. Its basic specific feature is imitation of ice cover with the help of so-called markers (conventional ice floes). Using three variants of the model grid net (25, 12.5 and 5 km), the ice conditions in the Baidara Bay and the adjoining area in January-March 2018 were simulated. The analysis of the simulation results showed that the average ice drift (average ice transport) is directed from the Baidara Bay to the open sea, i.e. northward with slight deviations mostly to the west. A less detailed grid net results in a smoothed ice drift field, while an increase in the spatial resolution of the model increases the spatial contrasts of the ice drift. The maximum values of the extreme ice drift velocity expressed as “once per N years” occur in the northern part of the model area at the directions of the north-western quarter (up to 1.5-1.8 m/s “once per 10 years” - “once per 100 years”, respectively). The frequency of ice drift velocity exceeding 0.3 m/s is about 4-7 %, and that of ice drift velocity exceeding 0.6 m/s is not more than 1 %. At low drift velocity, the role of inertia is very high, but as the drift rate grows, the inertia contribution decreases noticeably. At increasing drift velocity, the statistical correlation between the ice drift (on the one hand) and the wind, current and sea level tilt (on the other hand) becomes evident. This effect is especially evident for the correlation “drift / wind”. The correlation “drift / ice pressure” depends on the drift speed more or less noticeably at low and high drift speeds, when unidirectional changes of the ice drift and ice pressure happen more often than the opposite ones. At the drift velocities within 0.15-0.60 m\s, the correlation between the ice drift and ice pressure is insignificant, i.e. the unidirectional and opposite changes of the ice drift and ice pressure are almost equally likely.

Interannual variability of the ice-free period duration in the southwestern Kara Sea

In the coming years, exploration drilling in the geological structures in the Kara Sea is planned. It will be carried out during the ice-free period using floating drilling facilities of a different ice class. The aim of the work is analysis of the interannual variability of duration of the ice-free period in the area of the geological structures the results of which are necessary for planning operational activity of the drilling platforms and optimization of expenses for exploration drilling on the Arctic shelf. For an assessment of interannual variability of the ice-free period duration in the area of the geological structures there were used data on the dates of water area clearance from ice and beginning of ice formation in the southwestern part of the Kara Sea for the period of 30 years on the basis of the AARI weekly ice charts. An analysis of interannual variability of the ice-free period duration showed that a 20-year summer (1989–2008) and a 10-year (2009–2018) intervals could be identified. It is shown that in the last decade as a result of combination of favorable hydrometeorological conditions the ice-free period duration has increased by more than 1 month. An analysis of the main hydrometeorological factors determining the ice-free period duration indicated that it is possible to perform an assessment of duration of exploration drilling operations in the water area of the East-Prinovozemelsky license blocks with a period in advance of several months. Drilling with the use of ice-resistant drilling platform allows us to extend the operation period, as drilling could be started after disappearance of close ice and finished after the ice thickness growth up to 30 cm.

Structure and Productivity of the Phytocenosis in the Southwestern Kara Sea in Early Spring

Results of plankton biota studies in the southwestern Kara are presented. The spatial distribution of hydrochemical and hydrophysical parameters related to structural and functional characteristics of phytoplankton in the surface water is considered. The chlorophyll a concentration varied in the surface layer of the Kara Sea from 0.08 to 3.22 mg m–3 (mean value 0.62 mg m–3). Primary production varied from 0 to 1.92 mg C m–3 day–1 (the mean value of 0.42 mg C m–3 day–1) in the ice-covered water areas and was greater by a factor of four, ranging from 1.01 to 3.46 mg C m–3 day–1 (the mean value of 1.79 mg C m–3 day–1) in ice-free areas. In this case, the total algal biomass varied from 0.8 to 110.7 mg C m–3 (mean value 10.6 mg C m–3). It is shown that in the study period, waters from the western Kara Sea were more productive than the estuarine water areas of the Ob and Yenisei rivers. The activity of phototrophic phytoplankton in river waters was almost completely absent. It is established that the contents of nutrients and iron were higher than the threshold for limitation of phytoplankton development. The experiments showed that the production activity of phototrophic algae is restrained by light deficit beneath the ice.

The Quantitative Features of the Phytoplankton Community in the Southwestern Kara Sea in the Summer of 2015

This paper presents results from a study of phytoplankton communities that was performed in 2015 at 213 stations in the southwestern part of the Kara Sea. The values of primary production at most stations exceeded the estimates obtained in 1993 by several times. A continued increase in productivity indices and no outbreaks of phytoplankton were consistent with long-term satellite monitoring data. At the same time, grouping of stations showed a highly mosaic structure of the spatial distribution of phytoplankton and a significant range of variation of most of the studied parameters.

Microbial Community Composition and Rates of the Methane Cycle Microbial Processes in the Upper Sediments of the Yamal Sector of the Southwestern Kara Sea

Geochemical, biogeochemical, and molecular genetic investigation of the upper (0–5 cm) bottom sediments of the Yamal sector of the Kara Sea was carried out. The Yamal sector is well-protected from the massive inflow of river water. The sediments were oxidized at the surface and weakly reduced in the 3−5-cm layer. Corg content varied from 0.1 to 1.3%, while the level of dissolved СН4 was 1.9 to 20.3 μmol L–1. The isotopic composition of organic matter (OM) carbon, δ13Corg, varied from–27.5 to–22.2‰ (–25.4‰ on average). The share of terrigenous OM was 13.3 to 72.2% (48.9% on average). The rate of methane production, methane oxidation, and sulfate reduction varied from 0.8 to 9.0 (2.7 on average) nmol СН4 dm–3 day–1, from 9.9 to 103 (31.6 on average) nmol СН4 dm–3 day–1, and from 0.49 to 2.2 (1.1 on average) μmol S dm–3 day–1, respectively. High-throughput sequencing of the amplicons of the 16S rRNA genes was used to reveal the physiological groups of microorganisms responsible for the processes of methane production and oxidation, sulfate reduction, and oxidation of reduced sulfur compounds. Members of the phylum Woesearchaeota were predominant among archaea. Methanogenic archaea belonged to the families Methanobacteriaceae, Methanococcaceae, and Methanosarcinaceae (Euryarchaeota). Methanotrophs of the family Methylococcaceae were revealed among the Gammaproteobacteria, with their share in the sediments ~1%. In the class Deltaproteobacteria (15.4%), three orders of sulfate reducers were predominant: Desulfobacterales, Desulfovibrionales, and Desulfuromonadales. Oxidation of reduced sulfur compounds was carried out by chemolithoautotrophic bacteria of the genera Sulfurovum, Sulfurimonas, and Arcobacter of the class Epsilonproteobacteria (1.1% of the total microbial number).

The tides in the south-western Kara sea. Tides calibration method effects

The estimates of the tides harmonic constants are given over the period from 1962 to 1993. They were received using a least square method according to AARI. Quality estimation of the sea level observations was performed. The annual series with bad observations were transformed by means of tides calibration. The Estimation of the tides fi ne structure – harmonics of the second and third degree of the potential according to analysis over the period from 1962–1985 was received. The statistical estimations of the sea level in the separate typical years were calculated using initial and corrected series.

Structure of the macrozoobenthic communities in the southwestern Kara Sea

The structure and distribution of the macrobenthic communities were studied in the southwestern Kara Sea. The material was collected in Baidaratskaya Bay in July 2007 and in a section running westward of the Yamal Peninsula in September 2007. The depths of the sampling stations ranged from 5 to 25 m in the Baidaratskaya Bay area and between 16 and 46 m in the Yamal section. A total of 212 benthic invertebrate species were recorded. In both areas, Bivalvia was the group with the highest biomass (54.88 g/m2 in the Yamal section and 59.71 g/m2 in the Baidaratskaya Bay area), while polychaetes were the group with the highest number of species (45 in the Yamal section and 64 the Baidaratskaya Bay area). Three major macrozoobenthic communities were recognized: the Astarte borealis community (20–46 m, the deepest sampling stations in both areas); the “medium-depth” community (10–20 m, extremely mosaic, usually dominated by Serripes groenlandicus); and the Nephtys longosetosa community (depth smaller than 10 m, characterized by low biomass and the absence of large bivalves and echinoderms). The western Yamal shallow-water communities were shown to be generally similar to those of Baidaratskaya Bay. The comparison of these results with those of the benthos censuses performed in 1927–1945, 1975, and 1993 showed that the benthic communities in the southwestern Kara Sea remained relatively stable during the second half of the 20th century and the early 21st century.

Circulation in the southwestern part of the Kara Sea in September 2007

During cruise 54 of the R/V Akademik Mstislav Keldysh to the southwestern Kara Sea (September 6 to October 7, 2007), a large amount of hydrophysical data with unique spatial resolution was obtained on the basis of measurements using different instruments. The analysis of the data gave us the possibility to study the dynamics and hydrological structure of the southwestern Kara Sea basin. The main elements of the general circulation are the following: the Yamal Current, the Eastern Novaya Zemlya Current, and the St. Anna Trough Current. All these currents are topographically controlled; they flow over the bottom slopes along the isobaths. The Yamal Current begins at the Kara Gates Strait and turns to the east as part of the cyclonic circulation. Then, it turns to the north and propagates along the Yamal coast over the 100-m isobath. The Eastern Novaya Zemlya Current (its core is located over the eastern slope of the Novaya Zemlya Trough) flows to the northeast. Near the northern edge of Novaya Zemlya, it encounters the St. Anna Trough Current, separates from the coast, and flows practically to the east merging with the continuation of the Yamal Current. A strong frontal zone is formed in the region where the two currents merge above the threshold that separates the St. Anna Trough from the Novaya Zemlya Trough and divides the warm and saline Arctic waters from the cooler and fresher waters of the southwestern part of the Kara Sea. This threshold, whose depth does not exceed 100–150 m, is a barrier that prevents the spreading of the Barents Sea and Arctic waters to the southwestern part of the Kara Sea basin through the St. Anna Trough.

The upper desalinated layer in the Kara Sea

An area of about 40000 km2 of desalinated upper layer waters with a salinity of less than 25 psu was found during cruise 54 of the R/V Akademik Mstislav Keldysh in the southwestern part of the Kara Sea (September 2007). Close to the boundary of this region located near the eastern coast of Novaya Zemlya, the salinity was less than 16 psu. The thickness of the desalinated layer was about 10 m. The results of the chemical analysis revealed that the observed desalination of the sea water was produced, first of all, by the Yenisei River, while the contribution of the Ob River’s waters was secondary. However, the most desalinated region near the eastern coast of Novaya Zemlya was separated from the Ob-Yenisei estuary and corresponded to a quasi-isolated lens. It is likely that the formation of this lens, as well as the major part of the desalinated upper layer waters, occurred in June when the flood of the Yenisei was maximal, while the further drift of the desalinated waters to the west of the Ob-Yenisei estuary was forced by the prevailing northern wind. The additional desalination (by 2–3 psu and even more) of the upper layer waters near the eastern coast of Novaya Zemlya might be related to the melting of the Novozemelskiy ice massif. The regularities of the temporal evolution of the upper desalinated layer, as well as the influence of this layer on the hydrological structure and dynamics of the southwestern Kara Sea, are discussed.

Entrainment of fine-grained surface deposits into new ice in the southwestern Kara Sea, Siberian Arctic

The entrainment of bottom deposits (silt and clay) into newly formed ice was investigated in the Amderma/Vaygach flaw lead in the southwestern Kara Sea, Siberian Arctic. Fine-grained bottom deposits and sea ice sediments (SIS) were analyzed by granulometry, scanning electron microscopy and X-ray diffractometry. On average, SIS contain by a factor of four times more silt than the shelf deposits (66.7% vs. 16.3%), and the SIS clay percentage is more than three-fold of the bottom value (31.2% vs. 9.1%). Sand-sized particles are significantly less abundant in SIS compared to bottom sediment (2.1% vs. 74.6%). The preferred entrainment of silt into ice is underpinned by the enhanced silt-to-clay-ratio in SIS compared to bottom deposits. Though silt is preferably entrained into SIS, no evidence was found for preferential ice-entrainment of any silt sub-fraction (coarse, medium or fine). However, sub-angular- and angular-discoidal silt particles are favorably entrained into local sea ice. Clay mineral assemblages in SIS and shelf surface sediments match very well revealing that no individual clay mineral is preferably enriched in SIS or reduced at the bottom. The general textural, compositional and statistical match of fine-grained shelf surface deposits and SIS proves that bottom sediment is the principle source for ice-entrained material in the study area. We propose e.g. wave action and thermohaline convection to take sediment particles upward from the bottom nepheloid layer into the well-mixed 10–40 m deep water column of the Amderma/Vaygach flaw lead, and the turbulent process of suspension freezing to bring sediment particles and frazil crystals into contact, finally leading to the formation of sediment-laden ice. The role of SIS entrainment and export for local/regional shelf erosion and coastal retreat is of minor importance in the SW Kara Sea compared to other circum-Arctic shelf seas. However, the characteristic clay mineral assemblage of local SIS and bottom deposits can help identify the origin of SIS both on regional and Arctic-wide scales.

Speciation of some heavy metals in bottom sediments of the Ob and Yenisei estuarine zones

The speciation of Fe, Mn, Zn, Cu, Co, Ni, Cr, Pb, and Cd was studied in 52 samples of bottom sediments collected during Cruise 49 of the R/V Dmitrii Mendeleev in estuaries of the Ob and Yenisei rivers in the southwestern Kara Sea. Immediately after sampling, the samples were subjected to on-board consecutive extraction to separate metal species according to their modes of occurrence in the sediments: (1) adsorbed, (2) amorphous Fe-Mn hydroxides and related metals, (3) organic + sulfide, and (4) residual, or lithogenic. The atomic absorption spectroscopy of the extracts was carried out at a stationary laboratory. The distribution of Fe, Zn, Cu, Co, Ni, Cr, Pb, and Cd species is characterized by the predominance of lithogenic or geochemically inert modes (70–95% of the bulk content), in which the metals are bound in terrigenous and clastic mineral particles and organic detritus. About half of the total Mn amount and 15–30% Zn and Cu is contained in geochemically mobile modes. The spatiotemporal variations in the proportions of metal species in the surface layer of sediments along the nearly meridional sections and through the vertical sections of bottom sediments cores testify that Mn and, to a lesser extent, Cu are the most sensitive to changes in the sedimentation environment. The role of their geochemically mobile species notably increases under reducing conditions.