Laptev Sea Research Articles

Biogeochemical structure of the Laptev Sea in 2015-2020 associated with the River Lena plume

The discharge of rivers and the subsequent dispersion of their plumes play a pivotal role in the biogeochemical cycling of the Arctic Ocean. Based on the data collected during annual transects conducted in the autumn period (September-October) from 2015-2020, this study explores the effect of River Lena plume dispersion on the seasonal and interannual changes in the hydrophysical and biogeochemical structure of the southeastern Laptev Sea. The temperature-salinity relationship (T-S), Redfield ratio and multiparameter cluster analysis were used to investigate variations in the water mass structure along the transect. The results revealed that the plume’s interannual and seasonal spreading patterns play a crucial role in regulating the local physical, biogeochemical, and biological processes in the southern Laptev Sea. During September-October, the hydrochemical water mass structure along the transects shifted from highly stratified to unstratified as the plume’s mixing intensity increased. Anomalous hydrochemical distributions were observed due to coastal upwelling, which was primarily characterized by high total alkalinity and nitrate levels, and low organic phosphorus, nitrite, and ammonia levels in the seawater. Wind and cold weather conditions drive deep vertical mixing of seawater, causing the resuspension of bottom sediment and the subsequent enrichment of bottom water by nutrients. Multi-parameter cluster analysis is used to describe the details of water mass structures in the highly dynamic southern Laptev Sea, with water mass structures typically undergoing significant changes within two weeks between September and October. The migration and transformation of water masses throughout the seasons are influenced by the volume of river discharge, fall-winter cooling, and atmospheric circulation patterns. Furthermore, the general atmospheric circulation is confirmed to be the primary cause of the interannual variation in the spread of the Lena River plume over the southeast Laptev Sea.

Morphodynamic Types of the Laptev Sea Coast: A Review

The Laptev Sea coast has a unique high-latitude and dynamic landscape. The presence of low-temperature permafrost (below −7 °C) and its high ice content (up to 90%) determine a wide array of permafrost landforms and features. Under the actions of thermal abrasion and thermal denudation, high rates of coastal retreat are evident within this region. Local differences in the geological structure and sea hydrodynamic conditions determine the diversity of this sea coast’s types. In this review, we present the results of a morphodynamic classification and segmentation of the Laptev Sea coast. The integrated approach used in the classification took into account the leading relief-forming processes that act upon this coastal zone. The research scale of 1:100,000 made it possible to identify and characterize the morphologies of the coast and their spatial distributions within the study area. The presented original classification can be considered to be universal for the eastern Arctic seas of Eurasia; it may be used as a basis for further scientific and applied research.

First Record of the Northern Wolffish Anarhichas denticulatus Krøyer, 1845 (Anarhichadidae: Zoarcoidei: Perciformes) in the Siberian Arctic: Further Evidence of Atlantification?

A single specimen of the northern wolffish Anarhichas denticulatus Krøyer, 1845, 393 mm in length, was documented for the first time in the Siberian Arctic (Laptev Sea, Russia). Species identification was confirmed by an integrative taxonomic approach that included examination of external morphology and DNA barcoding using the COI mtDNA gene. This species is widely distributed in the North Atlantic, but records in the Arctic Ocean are limited to the Canadian and US coasts. This record might represent a significant range extension of about 7500 km for the species and may be associated with the eastward transport of a pelagic juvenile specimen from the Northeastern Atlantic to the Laptev Sea by the North Atlantic current, consistent with the hypothesis of Atlantification of the Arctic Ocean. X-ray images of the Laptev Sea specimen and photographs showing ontogenetic variations of species’ coloration are provided for reference. The Laptev Sea specimen had a more elongated shape, longer preorbital distance, and longer pectoral, dorsal, and anal fins, as well as a larger eye and wider caudal fin compared to North Atlantic samples. The size differences are likely associated with conditions experienced as a juvenile during the pelagic stage of the lifecycle.

Features of Formation of the Lena Polynya on the Estuarine Coast of the Bykovsky Arm in the Summer

Based on the results of the global oceanic reanalysis (GLORYS12.v.1), materials of hydrometeorological observations of the Roshydromet network in the Laptev Sea and the mouth of the Lena River, reviews of the ice processes in the Arctic Ocean by the Arctic and Antarctic Research Institute, this paper considers the features of the evolution of the Lena Polynya on the estuarine coast of the Bykovsky Arm in the warm period 1993–2019. The relationship between the timing of the formation of a polynya on the seashore of this arm with the dates of the beginning of the flood at the top of the Lena River delta has been revealed. The assumption is confirmed that the average growth rate of the Lena polynya in summer is determined by the timing of its formation – the earlier the flood begins, the earlier the polynya forms on the coast of the Bykovsky arm and the smaller the average rate its growth. It has been established that the process of warming in the mouth area of the Lena in 2008–2019 stabilized, as there are no significant trends in the characteristics of water and ice regimes. These regularities may be invariant for other mouths of the rivers of the Laptev Sea basin, and the obtained dependences can be used to improve the forecast of the dates of cleansing of the water area at the estuary seashore of the Lena from ice and planning icebreaking navigation along the route Tiksi port–Lena River.

Thermal Regime of the Lithosphere under the Taimyr Peninsula According to Geomagnetic Data

This article presents the results of a study of the thermal regime of the lithosphere under the TaimyrPeninsula and adjacent territories (70°–80° N, 80°–115° E) based on geomagnetic data. Spectral analysis ofthe lithospheric geomagnetic field given by the EMAG2v3 model was performed using the centroid method.The calculations we performed showed that the minimum depths of the top boundary of lithospheric magneticsources (2.5 km) are typical for the entire Taimyr fold belt and the considered part of the Siberian Platform,and the maximum (6 km) for the North Kara Basin. The position of the top boundary of the magneticallyactive layer of the lithosphere above the bottom of the sedimentary layer under the Yenisei-Khatangaand Khatanga-Lena basins can be associated with the widespread intrusion of basalt traps into the sedimentarylayer. The minimum depths of the bottom boundary of lithospheric magnetic sources (36 km) are confinedto the Eurasian Basin and neighboring territories of the Laptev Sea shelf and the islands of the SevernayaZemlya archipelago, which indicates the greatest heating of the lithosphere under them within theregion under consideration. The depth of the bottom boundary reaches maximum values (≥48 km) under theYenisei-Khatanga and North Kara basins and the Siberian Platform, indicating the existence of the cold and,accordingly, thick lithosphere here, which is confirmed by other independent geophysical data

Sensitivity of Seawater Temperature and Salinity to their Restoring Times, Appending in the Boundary Conditions for these Variables at the Free Surface of the Laptev Sea in the No-Ice Period

In order to study sensitivity of seawater temperature and salinity in the no-ice Laptev Sea to their restoring times, appending in the boundary conditions for these variables at the free surface, the 3D finite-element hydrostatic model QUODDY-4 and the indirect means of describing internal tidal waves have been applied. The latter is based on the use of the corrected eddy diffusivity representing the sum of the same uncorrected diffusivity and the diapycnal diffusivity. The first of them characterizes the influence of non-tidal factors, computed using 2.5-level eddy closure scheme, the second, determined by the ratio of internal tidal waves induced baroclinic tidal energy dissipation to the buoyancy frequency in square, the influence of purely tidal factor. The estimate of this dissipation obtained from a solution of auxiliary problem on the internal tidal waves dynamics and energetics is attached. Seawater temperature and salinity in the subsurface and near-bottom layers of the Sea and also their vertical distributions along the 120E meridional transection obtained for the strong, moderate, and mixed restoring times are discussed. As a result, it is clarified that seawater temperature and salinity are weakly sensitive to changes in the restoring time. The saying follows from a comparison of model averaged (over a chosen period and by the Sea area) values of seawater temperature and salinity, and from their local vertical profiles, computed with regard to accepted estimates of the restoring time.

A Short Research Guide on Arctic Historical Bryozoan Collections and a Few Associated Biocoenosis at the Zoological Institute of the Russian Academy of Sciences

Russian bryozoans and other invertebrate biocenosis material collected in the Arctic Ocean over a period of more than 250 years, and the corresponding literature citing them, are deposited in the Zoological Institute of the Russian Academy of Sciences, Saint Petersburg, Russia. This paper provides a general description and historical quantitative information about the Historical Bryozoan Collection kept in this Russian institute. Access to species-level data is available via the data portal ( www.zin.ru ). The quantitative distribution of benthos, specifically bryozoans, in the Russian Arctic seas remained nearly unexplored until recent times. The first systematic quantitative studies were conducted by the Zoological Institute in the Laptev Sea, in its southeastern part, on the New Siberian Shoal in 1973; the Chaun Bay of the East Siberian Sea in 1986; and near Wrangel Island and Cape Schmidt of the Chukchi Sea in 1976.

Eocene–Oligocene glaciation on a high central Tibetan Plateau

Abstract The nature of glaciation (bipolar vs. unipolar) during the Eocene–Oligocene transition (EOT) remains unresolved. Here, we report the occurrence of frost marks, ice-rafted debris (IRD), and glendonites from the Upper Eocene to Lower Oligocene Niubao Formation (Fm.) deposited in a proglacial lake above glaciolacustrine conglomerates and diamictite facies in the Lunpola Basin, central Tibetan Plateau (CTP). Magnetostratigraphy dates these cryospheric deposits to ca. 36.2–31.8 Ma, synchronous with a stratigraphic interval containing IRD offshore of SE Greenland and in the Barents, Chukchi, and Laptev Seas, suggesting a strong continental-oceanic coupling. Our results provide robust continental evidence for intermittent cryospheric processes in the midlatitude Northern Hemisphere during the late Eocene and EOT. The global cold snap EOT-1 influenced already glacierized high-altitude mountains, lowering equilibrium line altitudes (ELAs) of glaciers and leading to local development of ice fields, ice caps, and valley glaciers with proglacial lake systems, such as the one recorded in the Niubao Fm. The record of IRD, glendonites, and frost marks before the onset of EOT-1 points to an active cryosphere on a plateau already elevated by ca. 36.2 Ma.

A Complex of Marine Geophysical Methods for Studying Gas Emission Process on the Arctic Shelf.

The Russian sector of the arctic shelf is the longest in the world. Quite a lot of places of massive discharge of bubble methane from the seabed into the water column and further into the atmosphere were found there. This natural phenomenon requires an extensive complex of geological, biological, geophysical, and chemical studies. This article is devoted to aspects of the use of a complex of marine geophysical equipment applied in the Russian sector of the arctic shelf for the detection and study of areas of the water and sedimentary strata with increased saturation with natural gases, as well as a description of some of the results obtained. This complex contains a single-beam scientific high-frequency echo sounder and multibeam system, a sub-bottom profiler, ocean-bottom seismographs, and equipment for continuous seismoacoustic profiling and electrical exploration. The experience of using the above equipment and the examples of the results obtained in the Laptev Sea have shown that these marine geophysical methods are effective and of particular importance for solving most problems related to the detection, mapping, quantification, and monitoring of underwater gas release from the bottom sediments of the shelf zone of the arctic seas, as well as the study of upper and deeper geological roots of gas emission and their relationship with tectonic processes. Geophysical surveys have a significant performance advantage compared to any contact methods. The large-scale application of a wide range of marine geophysical methods is essential for a comprehensive study of the geohazards of vast shelf zones, which have significant potential for economic use.

Distribution of Siboglinids (Annelida, Siboglinidae) in the Laptev Sea and Adjacent Areas of the Arctic Basin.

Biodiversity in the Laptev Sea was assessed for gutless marine worms of the family Siboglinidae (Annelida), whose metabolism is provided by symbiotic bacteria that oxidize hydrogen sulfide and methane. Seven siboglinid species were found within the geographical boundaries of the Laptev Sea, and another species was found in an adjacent sector of the Arctic Basin. The largest number of finds and the greatest biological diversity of siboglinids were observed in the eastern part of the Laptev Sea in a field of numerous methane flares. One find was made in the estuary area of the Lena River at a depth of 25 m. A possible association of siboglinids with methane seepage areas is discussed.

An Updated View of the Water Masses on the Northeast Greenland Shelf and Their Link to the Laptev Sea and Lena River

AbstractThe Northeast Greenland shelf is a broad Arctic shelf located between Greenland and Fram Strait. It is the principal gateway for sea ice export and sea ice‐associated freshwater from the Arctic Ocean. Sea ice thickness has decreased by 15% per decade since the early 1990s and meteoric freshwater discharge has increased. The consequence of changing sea‐ice and freshwater conditions in the region on ocean dynamics and the biological system remains unknown. Determining the source(s) of freshwater is important to be able to understand how the area will react to future upstream change. Here we present a synoptic survey of the Northeast Greenland shelf and slope with observations of hydrography, the nutrients nitrate, phosphate and silicate, and conservative tracers δ18O, δ2H, and total alkalinity during late summer 2017. We compare these to previously published values, including those which identify Pacific and Atlantic water, the Siberian shelf seas, and the six largest Arctic rivers. We show that a major source of freshwater on the Northeast Greenland shelf during late summer 2017 is the Laptev Sea and find no conclusive evidence of Pacific Water. Our observations indicate a direct link between Northeast Greenland hydrology and processes occurring on Eurasian shelves.

Моделирование ветрового волнения в море Лаптевых, Восточно-Сибирском и Чукотском морях

The paper presents an analysis of wind wave parameters in the Laptev, East Siberian and Chukchi seas based on the results of numerical experiments with the WAVEWATCH III wave model for a period from 1979 to 2021. Wave modeling was carried out using an unstructured computational grid with a high resolution (up to 800 m) in the coastal zone. The NCEP/CFSR/CFSv2 reanalysis was used as wind forcing. The maps of the long-term mean values of the wave height, wave length and period were obtained. For the several points in the central part of each sea, the mean annual values of wave heights are calculated and the analysis of interannual variability is carried out. The maximum significant wave height was 5–6 m in the Laptev Sea, 6–7 m in the East Siberian Sea, and 7–7.5 m in the Chukchi Sea. The analysis of interannual variability showed that there is a positive trend in wave height for all seas under consideration. The largest increase in the annual mean wave height is observed in the East Siberian Sea (from 0.4 to 1.4 m in the ice-free period). Keywords: Laptev Sea, Chukchi Sea, East Siberian Sea, wave modeling, Arctic wind waves, WAVEWATCH III

Distinct Role of a Spring Atmospheric Circulation Mode in the Arctic Sea Ice Decline in Summer

AbstractA distinguishing feature of Arctic sea ice is the rapid declining in the Pacific Arctic Sector (PAS) in recent years. The atmospheric variability during spring (March‐May) plays a critical role in determining the sea ice extent (SIE) during the following summer. The summertime (June‐August) SIE reduction in the eastern part of PAS, including the East Siberian Sea and the Laptev Sea, is strongly related to the first two leading atmospheric circulation modes in spring, the Arctic Oscillation and the Arctic Dipole, retrieved from empirical orthogonal function analysis. Here, we show that the third leading mode of atmospheric circulation in spring, namely the Barents‐Beaufort Oscillation (BBO), can also change the summer SIE, especially on the western regime of the PAS across the Beaufort and Chukchi Seas. We find that a positive phase of springtime BBO (i.e., BBO+), relative to the BBO−, acts to decrease sea ice thickness via advection and generate sea ice deformation through divergence and shear processes, thereby preconditioning for a rapid sea ice loss within the PAS in the following summer. Furthermore, the occurrence of BBO is state‐dependent and potentially modulated by the phase shift of the Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO). Since the mid‐1990s, the AMO (PDO) index has changed from a dominant negative (positive) to a positive (negative) phase. These phase shifts in AMO and PDO would have contributed to the subsequently increased appearance of anomalous BBO+ after 2000 and enhanced the summertime sea ice loss in the western regions of the PAS in recent years.

Automated Identification of Landfast Sea Ice in the Laptev Sea from the True-Color MODIS Images Using the Method of Deep Learning

Landfast sea ice (LFSI) refers to sea ice attached to the shoreline with little or no horizonal motion in contrast to drifting sea ice. The LFSI plays an important role in the Arctic marine environmental and biological systems. Therefore, it is crucial to accurately monitor the spatiotemporal changes in the LFSI distribution. Here we present an automatic LFSI retrieval method for the Laptev Sea, eastern Arctic Ocean, based on a conditional generative adversarial network Pix2Pix using the true-color images of Moderate Resolution Imaging Spectroradiometer (MODIS). The spatial resolution of the derived product is 1.25 km, with a temporal interval of 7 days. Compared to the manually identified data from the true-color images of MODIS, the average precision of the LFSI area derived from LFSI mapping model reaches 91.4%, with the recall reaching 98.7% and F1-score reaching 94.5%. The LFSI coverage is consistent with the traditional large-scale LFSI products, but provides more details. Intraseasonal and interannual variations in LFSI area of the Laptev Sea in spring (March–May) during the period of 2002–2021 are investigated using the new product. The spring LFSI area in this region decreases at a rate of 0.67 × 103 km2 per year during this period (R2 = 0.117, p < 0.01). According to the spatial and temporal changes, we conclude that the LFSI is becoming more stable while the area is shrinking. The method is fully-automatic and computationally efficient, which can be further applied to the entire Arctic Ocean for LFSI identification and monitoring.

A new interpretation of the inscriptions on the handles of signature knives found on the shores of Sims Bay

The article reports on a new interpretation of the inscriptions on two personalized knives found on the coast of Sims Bay in the Laptev Sea. This interpretation differs from the readings published previously by paleographers and source-study experts due to the fact that it has been possible to devise correct transcription of these inscrip-tions with the aid of the method of non-contact 3D modeling of epigraphic records developed by the RSSDA Laboratory and used in the Code of Russian Inscriptions (CIR). The reading of the inscriptions on the signature knives proposed by the authors of this paper has enabled establishing their ownership to Gurii (baptismal name) — Akakii (prayer? name) Ivanov son of Karzyaev’s, likely the head of the commercial and industrial expedition of the 1620s. The site of the polar mariners of the 17th century in Sims Bay is located 70 km west of the island of Thad-deus Severny, where in 1940 members of the hydrographic detachment of the East Taimyr hydrographic expedi-tion found similar articles, including 8 other knives. Unfortunately, these knives have only partially preserved han-dles, and most of them turned out to be represented only by the blades. Inscriptions made in the Slavic ligature could be found only on two knives from a hut in Sims Bay. According to the official version, both sites belong to the members of the Russian trade and industrial expedition of the 17th century. The rich composition of the collec-tion of archaeological artifacts assembled at the locations of these two sites makes this monument unique for the Russian culture of the 17th century.

The Content and Speciation of Radionuclides in Water and Bottom Sediments of the Laptev Sea

In the presented work, the features of the distribution of Cs-137 and plutonium isotopes in modern sediments of various parts of the Laptev Sea, selected during the expedition studies on the RV “Academician Mstislav Keldysh” in 2017 and 2019, were studied. It was found that the activity of Cs-137 in water and sediments is within the global level, which is typical for the seas of the Arctic region. In all the collected samples the specific content of Pu-239,240 isotopes is below the level of the minimum detectable activity. According to the results of isotope analysis of Pb-210, the sedimentation rates in two columns collected in the Laptev Sea are 0.18 and 0.23 cm/year. The study by several methods of the speciation forms of Pu-239, introduced into the samples of bottom sediments under laboratory conditions, showed that the main content of Pu-239 is associated with difficult-to-dissolve organo-mineral components. 30-39% Pu-239 was found in the composition of organic easily soluble acids and humic substances, which include fulvic and humic acids of bottom sediments.

DISTRIBUTION OF SIBOGLINIDS (ANNELIDA, SIBOGLINIDAE) IN THE LAPTEV SEA AND ADJACENT AREAS OF THE ARCTIC BASIN

The purpose of the article is to assess the biodiversity of gutless marine worms of the family Siboglinidae (Annelida), whose metabolism is provided by symbiotic bacteria that oxidize hydrogen sulfide and methane. Within the geographical boundaries of the Laptev Sea, 7 species of siboglinids were found, another 1 species was found in the adjacent sector of the Arctic basin. The largest number of finds and the greatest biological diversity of siboglinids were found in the eastern part of the Laptev Sea in the field of numerous methane. One find was noted in the estuary area of the Lena River at a depth of 25 m. The possible connection of siboglinids with methane seepage areas is discussed.

The Content and Speciation of Radionuclides in Water and Bottom Sediments of the Laptev Sea

The Content and Speciation of Radionuclides in Water and Bottom Sediments of the Laptev Sea

Late Mesozoic and Cenozoic Geodynamics of the Arctic Region: Implications for Abiogenic Generation of Hydrocarbons

Late Mesozoic and Cenozoic geodynamics of the Arctic region is discussed in the context of possible mechanisms which provide multistage cyclic transformations and transport of carbon through crust and mantle. Geodynamic processes control the abiogenic generation of hydrocarbons and the patterns of their localization. Possible mechanisms of abiotic hydrocarbon generation are explained in the context of carbon transport from subduction zones to rifts and serpentinization of ultramafic rocks in the rifts in the case of the Laptev Sea and Gakkel Ridge areas. The carbon of shallow crust origin migrates with encapsulated fragments of marine sediments which are consumed in the Pacific subduction zone where they become destroyed and transformed by different chemical and physical processes. The resulting C-species are involved in mantle convection flows and reach the continental rifts of the Laptev Sea and the Gakkel mid-ocean ridge. Thus, the hydrocarbons formed in the crust and in the mantle acquire signatures of abiotic origin. According to the authors, the scale of manifestation of abiogenic methanogenesis in the lower parts of the lithosphere and in the upper mantle is not so wide. Numerous small (mm and fractions of the mm) particles of exogenous matter and dispersed carbon pulled into the mantle can only form a stable crustal geochemical plume that propagates in the plane of movement of convective flows. Indirectly, the scale of manifestation of this process can be judged by the volumes of degassing of hydrocarbon and carbon dioxide gases, as well as hydrogen and its compounds in the rift systems of the earth’s crust, which are extremely insignificant. However, in the cold seas of the Eastern Arctic, massive emissions of bubble methane of mixed genesis were found. As shown in the literature, the range of variability of stable isotopes of carbon and 14C of methane in certain areas of discharge associated with rifting demonstrates values (anomalously heavy 13C, and young 14C) that can be considered as examples of presumably abiogenic origin. Our work is mostly theoretical and suggests further discussion and improvement of the mechanism of formation of abiogenic hydrocarbons and the processes of their transformation.

Changes in Sea Surface Temperature and Sea Ice Concentration in the Arctic Ocean over the Past Two Decades

With global warming, the decrease in sea ice creates favorable conditions for Arctic activities. Sea surface temperature (SST) is not only an important driven factor of sea ice concentration (SIC) changes but also an important medium of the ocean–atmosphere interaction. However, the response of sea surface temperature to Arctic sea ice varies in different sea areas. Using the optimal interpolated SST data from the National Centers for Environmental Information (NCEI) and SIC data from the University of Bremen, the temporal and spatial characteristics of SST and SIC in the Arctic above 60°N and their relationship are studied, and the melting and freezing time of sea ice are calculated, which is particularly important for the prediction of Arctic shipping and sea ice. The results show that (1) the highest and lowest monthly mean Arctic SST occur in August and March, respectively, while those of SIC are in March and September. The maximum trends of SST and SIC changes are in autumn, which are +0.01 °C/year and −0.45%/year, respectively. (2) There is a significant negative correlation between the Arctic SST and SIC with a correlation coefficient of −0.82. (3) The sea ice break-up occurs on Day of the Year (DoY) 143 and freeze-up occurs on DoY 296 in the Arctic. The melting and freezing processes lasted for 27 days and 14 days, respectively. (4) The Kara Sea showed the strongest trend of sea ice melting at −1.22 d/year, followed by the Laptev Sea at −1.17 d/year. The delay trend of sea ice freezing was the most significant in the Kara Sea +1.75 d/year, followed by the Laptev Sea +1.70 d/year. In the Arctic, the trend toward earlier melting of sea ice is smaller than the trend toward later freezing.