Akademik Mstislav Keldysh Research Articles

Providing Satellite Data to R/V Akademik Mstislav Keldysh during a Mission in the Southern Ocean

During cruise 79 of R/V Akademik Mstislav Keldysh in the Atlantic Antarctic, information is supplied using optical and radar high-, mid-, and low-resolution satellite data, in combination with geoinformation technologies. During field studies from December 2019 to February 2020, preliminarily processed information obtained by a multisatellite Earth remote sensing (ERS) system on sea surface temperature, sea ice concentration, icebergs, altimetry, and the concentration of near-surface layer matter (chlorophyll, particulate organic carbon, inorganic suspended particulate matter, and total suspended matter) is transmitted to the vessel. A description is given of the information infrastructure that provides the research vessel with routine satellite data that is automatically integrated into the user’s geoinformation environment as unified spatiotemporal distributions of important water environment parameters. Aspects of using satellite information when planning a ship’s route and making measurements are described.

The distribution of microplastics in the surface layer of the Atlantic Ocean from the subtropics to the equator according to visual analysis

This study reports the levels of plastic contamination in the Atlantic Ocean between 35°N and 32°S during the 1st stage of the 79th cruise of the “Akademik Mstislav Keldysh” from December 12, 2019, to January 4, 2020. A subsurface pump system and a Manta net were used for seawater filtration. Twenty-seven samples were visually analyzed with a microscope. It was found that almost every subsurface sample contained potentially plastic particles, which were classified according to their type and size. Plastic fragments were more commonly found in the samples taken from the surface. In the subsurface layer, the majority of the detected particles were fibers. These results also indicate that minimal concentrations of plastics tend to be found near the equator and to the north of the Canary Islands. The maximum microplastic concentrations were found in tropical zones. The obtained results are in good agreement with previous models and field studies.

Investigation of the Modern Lateral Sedimentation on the Argentine Continental Slope during Cruise 79 of the R/V Akademik Mstislav Keldysh

Herein we provide information on the sedimentological and paleoceanographic research on the Argentine Patagonian continental slope during cruise 79 of the R/V Akademik Mstislav Keldysh in March 2020. The preliminary scientific results are discussed.

The Seismotectonics and Seismicity of the Laptev Sea Region: The Current Situation and a First Experience in a Year-Long Installation of Ocean Bottom Seismometers on the Shelf

This paper is a review of current concepts concerning the seismotectonics and seismicity in the Laptev Sea region. The chief feature of the region is a rift system extending in the shelf from the continental slope with the adjacent Gakkel Ridge to the mainland coast. There are several models to describe the present-day evolution of the region, but no one of these is preferable because of the lack of local instrumental observations of shelf microseismicity, while such microseismicity is characteristic of rift zones. One alternative approach consists in the installation of ocean bottom seismometers on the shelf itself. During the 73rd cruise of the R/V Akademik Mstislav Keldysh, a temporary network was deployed consisting of 7 broadband bottom seismic stations on the Laptev Sea shelf. Comparative analysis of noise spectra based on records of a hydrophone, a bottom seismograph, and a wavegauge, showed that the noise amplitude strongly depends on wind waves, which is in turn dependent on marine ice cover, so that the recording potential of a local network of bottom seismographs is restricted to the winter period of observation.

Structure of Phytocenoses of the Yenisei Estuary and Adjacent Kara Sea Shelf in Late Spring

The research is based on the materials collected during cruise 66 of R/V Akademik Mstislav Keldysh in the Yenisei estuary and over the adjacent Kara Sea shelf in the latitudinal range from 71°50.5′ to 75°55.0′ N. The studies were performed from July 25 to 27, 2016, three weeks after the end of the flood period. Two hundred fifty species of plankton algae were recorded. Well-pronounced latitudinal zoning in phytoplankton communities structure associated with changes in the hydrophysical and hydochemical conditions of the pelagic environmental was determined. The maximum species diversity was formed by diatoms, green and blue-green algae in the southern desalinated part of the estuary (<1 PSU) and by diatoms and dinoflagellates in the offshore areas. The highest algae abundance and biomass, 2.7–2.9 × 106 cell/L and 1.1–1.5 g/m3, respectively, were recorded in the inner desalinated part of the estuary, where freshwater diatoms of the genus Aulacoseira dominated. The distribution of freshwater algae northwards was bounded by the 12–15 PSU surface isohaline (74°20′ N). The most pronounced decline in phytoplankton abundance and biomass was found in the outer part of the estuary north of ~73° N. In the middle shelf to the north of the Yenisei estuary, the maximum abundance (up to 740 × 103 cell/L) and biomass (up to 240 mg/m3) of phytoplankton were recorded at the depths of 30–40 m with low illumination and high nutrient concentration, which was also typical of the Ob region in spring–summer.

Atmospheric composition study based on ship measurements in the Russian Arctic seas in summer 2019

We present observation results of methane (CH4), its isotopic signature (δ13CCH4) and carbon dioxide (CO2) surface concentrations, made aboard the research vessel (R/V) “Akademik Mstislav Keldysh” in the Russian Arctic seas in summer 2019. The main goal of the study is to determine the possible sources of methane. As a result of the study, localized areas with an increased methane concentration (up to 2092 ppb) in the surface layer are identified. It may be related to the advection of water masses rich in organic matter from the Ob and Yenisei Rivers. In addition, increased methane concentrations (up to 2010 ppb) are observed in the Kara Sea near the Yamal Peninsula, where gas deposits are concentrated, and active methane emissions from wetland ecosystems are noted. We conclude that the average concentration of methane in surface air in the Arctic seas is determined mainly by large-scale transport of air masses.

Biochemical Composition and Energy Content in the Zooplankton of the Kara Sea

This article presents a data set on ash, proteins, lipids, carbohydrates, chitin, organic carbon (OC), total nitrogen (TN) and total phosphorus (TP) contents, macronutrients ratio (C, N, and P) and energy content of zooplankton (size fraction >500 μm) from the Kara Sea. Zooplankton samples were collected at 22 stations during the 76th interdisciplinary cruise of the R/V “Akademik Mstislav Keldysh” in July 2019. Proteins constituted the main component of zooplankton dry weight (43.39 ± 2.57% DW), while lipids amounted to 26.67 ± 2.28% DW and carbohydrates reached 4.91 ± 0.49% DW. Ash and chitin contents were 18.78 ± 1.39% and 3.68 ± 0.37% DW, respectively. The concentrations of macronutrients (C, N, and P) corresponded to the values of Arctic zooplankton and averaged 47.52 ± 1.12% for OC, 7.34 ± 0.39% for TN, and 0.70 ± 0.04% for TP of DW. The contribution of the individual components of the biochemical composition of zooplankton of the Kara Sea to the total OC revealed the dominant role of not only lipids but also proteins as compounds used by zooplankton in organic carbon accumulation. The Redfield ratio varied widely. The average values of C6.6:N, C70:P and N10.5:P were low and reflected certain features of the biochemical composition of the Kara Sea zooplankton community in the spring. The energy content of zooplankton of the Kara Sea ranged from 18.3 to 25.58 J mg-1 and averaged 20.25 ± 0.53 J mg-1 DW. The proportions of lipids and proteins in the total energy reserve of zooplankton were ~47 and ~46%, respectively, while the share of carbohydrates, their derivatives and chitin amounted to ~7%.

Grain Size Distribution of the Surface Layer of Bottom Sediments in the Barents Sea

The paper presents data from a granulometric analysis based on the results of studying of 44 surface (0–5 cm) sediment samples obtained on cruise 67 of the R/V Akademik Mstislav Keldysh (2016) from different parts of the Barents Sea. Pebble and gravel material is found in surface sediments as an admixture scattered throughout the sea. Such a chaotic distribution pattern is apparently associated with ice rafting. Coarse material is most common in the Barents Sea off the coast of the Kola Peninsula, Novaya Zemlya, and Svalbard, where it accumulates due to coastal abrasion, glacial exaration and bottom erosion. In addition, the >1 mm fraction is widespread at depths where fine fractions are stirred and washed away. The most common sediments in coastal shallow waters are sands. Sands (0.1–1 mm) are widespread in the southern and southeastern regions of the sea, in the region of the Pechora test area, the Kanin Shoal, the Kola Peninsula shallows; and in the northwest, off the coast of Svalbard. With increasing depth, coarse sediments are replaced by mixed sediments with a low pelite admixture. Fine-grained sediments are prevalent in the central part of the sea. Sediments with a pelitic fraction (<0.01 mm) of more than 50% occupy about 70% of the Barents Sea. They are widespread in deep-sea depressions and troughs, as well as in the numerous fiords of the Northern Island of Novaya Zemlya and Franz Josef Land.

Features of Bitumoid Distribution in Bottom Sediments of the Barents Sea

The results on the content, composition, and distribution of chloroform bitumoids (CBs) in the Holocene sediments of the Barents Sea are presented (Cruise 68 of the R/V Akademik Mstislav Keldysh, July–August 2017). Depending on the sedimentation conditions, CB concentrations varied on average (μg/g of dry mass) as follows: Novaya Zemlya Archipelago (174) > Svalbard Archipelago (131) > Western part (78) > Central part (69) > Franz Josef Land (52). Hydrocarbons comprised almost half (46% on average with the maximum of 85%) in the composition of CBs. Their distribution in the thickness of sediments is different and depends not only on the particle-size composition of sediments and the content of organic matter in them, but also on the variability of redox conditions and fluid flows of hydrocarbons from a sedimentary stratum. Therefore, markers of alkane composition and IR-Fourier spectra indicated both sedimentary (Murmansk bank, the Franz Josef Land shelf) and point oil (shelf of Svalbard Archipelago, Medvezhinskii Trench) sources of hydrocarbons.

Hydrochemical Structural Patterns of the Lena River–Laptev Sea Mixing Zone in the Autumn Period

This study was based on data obtained during the cruise 63 of the R/V Akademik Mstislav Keldysh in September 2015. We examine the features of the hydrochemical structure of the Lena River–Laptev Sea mixing zone. The studies were carried out in the eastern part of the Laptev Sea on a quasi-meridional transect, with the length of 710 km along 130°30' E. The distribution of dissolved oxygen, pH, alkalinity, major nutrients (phosphates, silicon, nitrate, and ammonium nitrogen), and chlorophyll a was analyzed. The relationship between the main hydrochemical parameters and chlorophyll a was considered. The distribution of hydrochemical parameters is similar to the data of previous studies: significant removal of silicon by waters of the Lena River (66.6 μM) with a moderate nitrate content (3.87 μM) and low concentration of mineral phosphorus (0.08 μM) in the area of strong influence of river runoff (salinity of 3.012 PSU). The presence of a near-bottom stagnant water zone in the part of research area affected by river runoff was detected. It is shown that the influx of mineral forms of nitrogen and phosphorus into the marine region of the Lena River delta occurs mostly as a result of nutrient recycling rather than due to the continental runoff.

Radiation-Geochemical Stability of Bottom Sediments in the Ob and Yenisei Estuaries and Adjacent Shoal Area of the Kara Sea

This paper reports the results of investigations on the radioecological state of bottom sediments of the Ob–Yenisei shoal area and Ob and Yenisei estuaries. Materials were obtained in two periods: 1995–2001 and 2014–2019 during seven expeditions on the R/V Akademik Boris Petrov, Professor Shtokman, and Akademik Mstislav Keldysh. Resampling of bottom sediment cores at key-points in areas of increased radiocesium activity and subsequent analysis of the radionuclide distribution made it possible to establish positive trends in the change of the radiation state of the regional ecosystem. The total degradation of the Ob radiocesium overactivity zone and quite significant degradation of the Yenisei zone (primarily the most polluted) were revealed. Comparison of current max-positions of specific activity in the vertical distribution of 137Cs in sediment cores made it possible to determine the sedimentation rate in the distal and proximal facies of the Yenisei estuary: 4.7–5.8 and 3.2–3.7 mm/year, respectively. The established changes that have occurred over ~20 years prove the ability of the Kara Sea ecosystem to self-purify. Pollutant diffusion and assimilation by bottom sediments play a significant role in the self-regeneration of the ecosystem. This is most intense in zone of influence of the river–sea geochemical barrier.

Albatross R package to study PARAFAC components of DOM fluorescence from mixing zones of arctic shelf seas

We have developed the package albatross in freely available R environment to perform parallel factor analysis of excitation–emission matrices (EEM/PARAFAC) analysis of seawaters. The key pre-processing steps for successful data analysis included intensity corrections for the instrument response function; inner filter effect correction; Raman and Rayleigh scattering handling. After implementing the necessary routines, we have focused on evaluation of their robustness for analysis of real data as well as on model validation and the assessment of adequacy of identified factors. The tolerance of 10−9 in the absolute change of R2 was found to be enough to prevent stopping before reaching the solution during the modeling. We have found that widely used S4C6T3 split-half procedure for validation cannot result in an unequivocal selection of the number of components. We have instead suggested a statistical evaluation of 100 randomly obtained splits to optimize number of factors (“randomized split-half”). The median split-half distance allows finding the unique optimal decomposition of EEM (4-component model in our case), and, therefore, it can serve as a criterion for model validation. The validation of the model was additionally supported by monitoring of a number of iterations before convergence and a decomposition R2.Finally, the validated EEM/PARAFAC model with 4 components for seawater obtained during the 63rd cruise of RV Akademik Mstislav Keldysh in 2015 (66 Arctic seawater samples)to those obtained by drEEM package in MatLab and to previous studies with the use of OpenFluor spectral library. A brief characterization of oceanographic data is provided.

Results of Studying Physicochemical Characteristics of Atmospheric Aerosol in the 71st Cruise of RV Akademik Mstislav Keldysh

In summer 2018 along the route of the 71st cruise of RV Akademik Mstislav Keldysh in the North Atlantic we carried out the measurements of such atmospheric aerosol characteristics as aerosol optical depth, near-surface aerosol and black carbon concentrations, content of chemical elements in aerosol samples, and organic and elemental carbon, as well as the isotopic composition of black carbon. It is shown that the average values of most characteristics decrease severalfold during passage from the Baltic Sea to the North Atlantic (57°–60° N), and then to the Norwegian Sea. For instance, the average black carbon concentration decreased from 83 to 29 ng/m3. Episodic impact of continental aerosol was noted even in remote regions of ocean. Outflow of smokes from forest fires in the north of Canada to the region of measurements (southward of Greenland) had the strongest effect on aerosol characteristics. The average concentrations of chemical elements in aerosol composition over the North Atlantic were several times larger than in the Arctic region, and smaller than in the background region of Siberia.

In situ Measurements of the Characteristics of Suspended Particles in the Barents Sea by the LISST-Deep Laser Diffractometer

The key indicators of marine sediment genesis are the particle size distribution (PSD) and volume concentration of suspended particulate matter (SPM). However, their study is not widespread in ship oceanology research. This paper reviews experience in using the LISST-Deep laser particle size analyzer for the study of marine SPM in situ. We present the first data on the volume concentration and PSD of SPM in the Barents Sea obtained during the 75th cruise of the RV Akademik Mstislav Keldysh in June 2019. We carried out an assessment of the adequacy of information display on the polydisperse system composition of the Barents Sea water body, which contains particles of a wide particle size spectrum of differing genesis and shape. This paper gives a regression and correlation analysis of LISST-Deep data with a Wet Labs turbidity meter and Multisizer 3 Coulter Counter, as well as the SPM mass concentration measured by the membrane filtration technique. All of them demonstrated reliable correlations between characteristics of SPM of the Barents Sea. Their correlation and determination coefficients varied from 0.6 to 0.8. The laser diffractometer produces more detailed vertical distributions of marine SPM parameters than does a turbidity meter, especially for euphotic zones. We found a significant correlation of LISST-Deep data with the concentration of dissolved oxygen, which increases for coarse–silty and sandy fractions (47.7–92.6 and 92.6–250 µm, respectively). Also, there is a correlation with SPM composition between parameters as organic carbon concentration and phytoplankton pigments. These correlations give some indirect indications of SPM composition from laser diffractometer measurements.

Chemical Composition of Atmospheric Aerosol in the Arctic Region and Adjoining Seas along the Routes of Marine Expeditions in 2018–2019

We consider the chemical composition (ions, elements, and polycyclic aromatic hydrocarbons) of atmospheric aerosol in different regions of the North Atlantic, European and Russian parts of the Arctic Ocean, and northern latitude and Far East seas. The studies were carried out onboard marine ships along their cruising routes (RV Akademik Tryoshnikov, RV Akademik Mstislav Keldysh, and RV Professor Multanovsky). The air samples were collected using the method accepted in the international networks operating under the Acid Deposition Monitoring Network in East Asia (EANET) and European Monitoring and Evaluation Programme (EMEP). The average sum of ion concentrations and the concentrations of individual ions in the aerosol over the seas in the North Atlantic and in the European part of the Arctic Ocean is consistent with measurements in the Laptev and Kara Seas in 2018 and 2019. The high concnetrations of PAHs in aerosol in seas and the Arctic Ocean in the central part of the Russian Arctic coincide with high concentrations of ions and trace elements in the aerosol composition. A difference is noted in the distribution of concentrations of trace elements in aerosol composition between seas of the North Atlantic and central region of the Russian Arctic, which possibly points to different sources of these components.

Investigations of the Ecosystem in the Atlantic Sector of Antarctica (Cruise 79 of the R/V Akademik Mstislav Keldysh)

Field works on cruise 79 of the R/V Akademik Mstislav Keldysh aimed at investigating the ecosystems in the Atlantic sector of Antarctica were conducted from January 16 to March 1, 2020. Hydrophysical and biological studies were carried out in the Drake Passage and the Bransfield and Antarctic Sound straits. The regions of Russian fishery interest were covered. Data were collected that characterize the environmental state; plankton communities, including krill, ichthyoplankton, macronecton; bottom fauna; and spatiotemporal variations in the most important ecosystem components.

ГРУБООБЛОМОЧНЫЙ МАТЕРИАЛ ЛЕДОВОГО РАЗНОСА НА ДНЕ БАРЕНЦЕВА МОРЯ

The coarse-grained material (CGM) obtained at 89 stations in 67 and 68 cruises of the R/V “Akademik Mstislav Keldysh” when washing modern sediments was studied. Its petrographic composition was studied, 35 petrographic types and subtypes of rocks were identified, their cyclograms were compiled. It was noted that the CGMof the Barents Sea is subject to significant fluctuations, but in general, it is complementary to the set of rocks of the adjacent land and is quantitatively ensured by the size of the examination and the removal of the material by the glacier to the sedimentation areas. Such mobility of the CGM makes it difficult to use it as a marker for geo-mapping the bottom of the Barents Sea.

ИССЛЕДОВАНИЕ СОСТАВА ОРГАНИЧЕСКОГО ВЕЩЕСТВА ДОННЫХ ОСАДКОВ МОРЯ ЛАПТЕВЫХ С ПРИМЕНЕНИЕМ МЕТОДА ROCK-EVAL

Актуальность исследования обусловлена необходимостью всестороннего изучения процессов, ответственных за изменения биогеохимического режима арктического региона. Увеличение темпов деградации прибрежной и подводной мерзлоты на Восточно-Сибирском шельфе приводит к вовлечению в современный биогеохимический цикл большого объема ремобилизованного органического углерода. Изучение особенностей его транспорта и преобразования в системе суша–шельф играет важную роль для оценки функционирования крайне хрупкой арктической экосистемы. Цель: изучение геохимических характеристик органического вещества, прослеживаемых по профилю от береговой зоны к континентальному склону моря Лаптевых с применением метода Rock-Eval и оценка их взаимосвязи с литологическими свойствами вмещающих осадков. Объектом исследования явились пробы донных осадков, взятые с поверхностного горизонта (0–2 см). Отбор проб проводился в морских арктических экспедициях 2018–2019 гг. на НИС «Академик Мстислав Келдыш». Результаты. На основе результатов пиролитического анализа дана геохимическая характеристика органического вещества, содержащегося в донных осадках моря Лаптевых. Органическое вещество, экспортируемое с речным стоком и продуктами береговой эрозии, характеризуется относительно низким кислородным (OI) и водородным (HI) индексами в прибрежной зоне и на глубинах до нескольких десятков метров. В районе среднего шельфа существенное влияние на состав органического вещества, по всей видимости, оказывает снос осадочного вещества с Новосибирских островов, где активно действуют термоабразионные процессы (снижение значений HI и увеличение OI). Высказано предположение, что для продуктов, выносимых речным стоком, и продуктов эрозии берегов характерны различные пиролитические параметры, определяемые методом Rock-Eval (в частности, значения HI, OI и Tpeak).

Hydrocarbons in the Water and Bottom Sediments of the Barents Sea during Ice Cover Variability

Aliphatic hydrocarbons (HCs) were studied in water and bottom sediments sampled during cruises 67th and 68th (August–September 2016 and July–August 2017, respectively) of the R/V Akademik Mstislav Keldysh in the Barents Sea to determine the lateral and interannual variability of their concentrations and composition. It has been established that the HC distribution in water was mainly determined by natural factors and depended on the hydrological peculiarites in different areas of the sea. From autumn 2016 to summer 2017, hydrocarbon concentrations slightly increased (on average, from 3 to 5 µg/L), which was related to a change in the biochemical composition of organic matter likely owing to the decrease of ice area. The content of HCs decreased mainly with the depth. An exception was observed in the area of troughs and deposits, where nepheloid bottom layers demonstrated an increase of HC concentration in suspended matter and in the surface layer of bottom sediments, whereas sedimentary sequence showed no correlation between HC distribution and organic carbon.

Ecological State and Mineral-Geochemical Characteristics of the Bottom Sediments of the East Siberian Sea

This paper reports the results of investigations in September 2017 on the radioecological state of bottom sediments of the East Siberian Sea during integrated research of the Siberian Arctic seas on cruise 69 of the R/V Akademik Mstislav Keldysh. Evaluation of the results of γ-spectrometric analysis found that the current specific activity of artificial cesium-137 in sediments is two orders of magnitude below the acceptable level and reflects the influence of global fallout from the atmosphere only. Sediments are not contaminated with heavy metals either. Bottom sediments are represented by silts: pelitic, aleuritic–pelitic, and fine aleuritic with a content of pelite (<0.01 mm) fractions of 40–80%. The western and eastern parts of the East Siberian Sea have differences in the distribution and composition of mineral components and element composition due to the influence of the catchments of the Indigirka and Kolyma rivers, respectively.