Double diffusion, shear instabilities, and heat impacts of a Pacific Summer Water intrusion in the Beaufort Sea

Pacific Summer Water eddies and intrusions transport heat and salt from boundary regions into the western Arctic basin. Here we examine concurrent effects of lateral stirring and vertical mixing using microstructure data collected within a Pacific Summer Water intrusion with a length scale of ∼20 km. This intrusion was characterized by complex thermohaline structure in which warm Pacific Summer Water interleaved in alternating layers of O(1 m) thickness with cooler water, due to lateral stirring and intrusive processes. Along interfaces between warm/salty and cold/fresh water masses, the density ratio was favorable to double-diffusive processes. The rate of dissipation of turbulent kinetic energy (ε) was elevated along the interleaving surfaces, with values up to 3×10−8 W kg−1 compared to background ε of less than 10−9 W kg−1. Based on the distribution of ε as a function of density ratio Rρ , we conclude that double-diffusive convection is largely responsible for the elevated ε observed over the survey. The lateral processes that created the layered thermohaline structure resulted in vertical thermohaline gradients susceptible to double-diffusive convection, resulting in upward vertical heat fluxes. Bulk vertical heat fluxes above the intrusion are estimated in the range of 0.2-1 W m−2, with the localized flux above the uppermost warm layer elevated to 2- 10 W m−2. Lateral fluxes are much larger, estimated between 1000-5000 W m−2, and set an overall decay rate for the intrusion of 1-5 years.

Distribution of Nereilinum murmanicum (Annelida, Siboglinidae) in the Barents Sea in the Context of Its Oil and Gas Potential

Frenulate siboglinids are a characteristic component of communities living in various reducing environments, including sites with hydrocarbon seeps. High concentrations of hydrocarbons in the sediments of the Arctic basin seas, including the Barents Sea, suggest the presence of a rich siboglinid fauna there. This reflects the fact that microbiological oxidation of methane occurs under reducing conditions, generating high concentrations of hydrogen sulfide in the sediment. This hydrogen sulfide acts as an energy source for the sulfide-oxidizing symbionts of siboglinids. Here we report on the findings of the frenulate siboglinid species Nereilinum murmanicum made between 1993 and 2020 in the Barents Sea. These data significantly expand the range of this species and yield new information on its habitat distribution. The depth range of N. murmanicum was 75–375 m. The species was most abundant from 200 to 350 m and was associated with temperatures below 3 °C and salinities from 34.42 to 35.07. Most of the findings (43 locations or 74%) fall on areas highly promising for oil and gas production. Twenty-eight locations (48%) are associated with areas of known oil deposits, 22 locations (37%) with explored areas of gas hydrate deposits. N. murmanicum was also found near the largest gas fields in the Barents Sea, namely Shtokman, Ludlovskoye and Ledovoye.

Tight association between microbial eukaryote and Imitervirales communities in the Pacific Arctic Ocean

Viruses are important regulatory factors of marine microbial community including microeukaryotes. However, little is known about their role in the northern Chukchi Sea of the Arctic basin, which remains oligotrophic conditions in summer. To elucidate linkages of microbial eukaryotic community with viruses as well as environmental variables, we investigated the community structures of microeukaryotes (3-144 μm and 0.2-3 μm size fractions) and Imitervirales (0.2-3 μm size fraction), a major group of viruses infecting marine microeukaryotes. Surface water samples were collected at 21 ocean stations located in the northeastern Chukchi Sea (NECS), an adjacent area outside the Beaufort Gyre (Adjacent Sea; AS), and two melt ponds on sea ice in the summer of 2018. At the ocean stations, nutrient concentrations were low in most of the locations expect at the shelf in the AS. The community variations were significantly correlated between eukaryotes and Imitervirales, even within the NECS characterized by relatively homogeneous environmental conditions. The association of the eukaryotic community with the viral community was stronger than that with geographical and physicochemical environmental factors. These results suggest that Imitervirales are actively infecting their hosts even in cold and oligotrophic sea water in the Arctic Ocean.

Numerical simulation of underwater cable laying with account of non-uniform hydrostatic force at Arctic basin condition

Статья посвящена моделированию динамического равновесия установившегося движения протяженной кабельной линии с учетом действия гидродинамических сил сопротивления и неоднородной гидростатической силы. Учитывая различные условия и глубины укладки, а также требования функционального назначения и защиты от враждебных факторов морского дна, необходимо рассмотреть широкий диапазон кабелей с различными механическими характеристиками: трехжильный кабель с одиночным бронированием 2XS2YRAA, одножильный кабель с одиночным бронированием ZS-YJQ41 и одножильный кабель с двойным бронированием – аналог GASLMLTV. Целью работы является развитие цифровой технологии по моделированию укладки подводных коммуникационных и силовых кабелей, позволяющей учитывать многочисленные физико-механические явления, имеющие место при проведении реальных морских работ. Для достижения поставленной цели работы используется программная среда Matlab Math Works с использованием разработанного комплекса программ для инженерной оценки формы и натяжения провисающего участка кабеля. Научная новизна состоит в апробации модели подводной укладки кабеля, учитывающей действие неоднородной гидростатической силы. Результаты моделирования представлены в виде формы и натяжения провисающей части кабеля при различных углах схода кабеля с движущегося судна при различных механических параметрах кабелей. Практическое значение работы состоит в повышении эффективности освоения перспективных месторождений, путем определения характеристик укладки кабеля в условиях Арктического бассейна: газовое месторождение Лудловское, газоконденсатное месторождение Ленинградское, нефтяное месторождение Медынское-море. This article studies the numerical simulation of underwater steady motion of the cable line with account of hydrodynamic water resistance forces and non-uniform hydrostatic force. It is necessary to consider distinctive types of cables due to various depths, laying conditions, functional requirements and protection requirements against adverse factors of seabed. Three-core single armoured cable 2XS2YRAA, one-core single armoured cable ZS-YJQ41 and one-core double armoured cable – analogue GASLMLTV are considered in this article. The aim of the research consists in digital technology development for underwater cable laying modeling, which allows taking into account numerous physical and mechanical features. These features occur during real marine operations for communication and power cables. Programming and numeric computing platform Matlab Math Works with developed software package is chosen as the research method. Simulation results are presented in dimensionless form for cable shape and tension for engineering purposes. The novelty of the work consists in approbation of underwater cable laying analytical model considering non-uniform hydrostatic force. Simulation results are presented for underwater cable laying during reeling from spool mounted on the vessel, moving with constant speed for distinctive types of cables. The influence of the cable run-off angle on the investigated characteristics was also considered. The practical value of the research consists in increasing of efficiency of exploration of oil, gas and condensate fields by determining underwater cable laying characteristics for perspective fields. At the end of the paper, the results of estimation of the shape and tension of the cable being laid undersea were presented for several fields at Arctic basin condition: gas field Ludlovskoe, condensate field Leningradskoe and oil field Medinskoe sea.

Influences of changing sea ice and snow thicknesses on Arctic winter heat fluxes

In the high latitude Arctic, wintertime sea ice and snow insulate the relatively warmer ocean from the colder atmosphere. As the climate warms, wintertime Arctic surface heat fluxes will be dominated by the insulating effect of snow and sea-ice covering the ocean until the sea ice thins enough or sea ice concentrations decrease enough such that direct ocean-atmosphere heat fluxes become more important. Simulated wintertime conductive heat fluxes in the ice-covered Arctic Ocean increase ~7–11 W m−2 by mid-21st century and are due to both thinning sea ice and snow on sea ice. Surface heat flux estimates calculated using grid-cell mean values of sea ice thicknesses underestimate mean heat fluxes by ~16–35 % and overestimate changes in conductive heat fluxes by up to ~36 % in the wintertime Arctic basin even while sea ice concentrations remain above 90 %.

Ocean Acidification Amplifies Multi-Stressor Impacts on Global Marine Invertebrate Fisheries

Elevated atmospheric carbon dioxide (CO2) is causing global ocean changes and drives changes in organism physiology, life-history traits, and population dynamics of natural marine resources. However, our knowledge of the mechanisms and consequences of ocean acidification (OA) – in combination with other climatic drivers (i.e., warming, deoxygenation) – on organisms and downstream effects on marine fisheries is limited. Here, we explored how the direct effects of multiple changes in ocean conditions on organism aerobic performance scales up to spatial impacts on fisheries catch of 210 commercially exploited marine invertebrates, known to be susceptible to OA. Under the highest CO2 trajectory, we show that global fisheries catch potential declines by as much as 12% by the year 2100 relative to present, of which 3.4% was attributed to OA. Moreover, OA effects are exacerbated in regions with greater changes in pH (e.g., West Arctic basin), but are reduced in tropical areas where the effects of ocean warming and deoxygenation are more pronounced (e.g., Indo-Pacific). Our results enhance our knowledge on multi-stressor effects on marine resources and how they can be scaled from physiology to population dynamics. Furthermore, it underscores variability of responses to OA and identifies vulnerable regions and species.

The nature of regional magnetic anomalies in the northeast of the Barents-Kara continental margin based on the results of seismic data interpretation

Based on the interpretation of seismic sections via seismic reflection method, the lines of which intersect the positive magnetic anomalies in the St. Anna Trough and on the North Kara Shelf, the authors have substantiated the position of the Early Cretaceous dike belt in the north of the Barents-Kara platform for the first time. They traced the belt from the arch-block elevation of arch. Franz Josef Land, which belongs to the Svalbard platе through the Saint Anna Trough and further into the Kara platе to arch. Severnaya Zemlya. The distinguished dyke belt has discordant relationships with the structural-tectonic plan of the region under consideration. The authors illustrate the manifestations of dyke magmatism in the marked tectonic elements in seismic sections, and conclude that the dyke belt relates to the formation of the structural system of the Arctic basin.

The poleward enhanced Arctic Ocean cooling machine in a warming climate

As a cooling machine of the Arctic Ocean, the Barents Sea releases most of the incoming ocean heat originating from the North Atlantic. The related air-sea heat exchange plays a crucial role in both regulating the climate and determining the deep circulation in the Arctic Ocean and beyond. It was reported that the cooling efficiency of this cooling machine has decreased significantly. In this study, we find that the overall cooling efficiency did not really drop: When the cooling efficiency decreased in the southern Barents Sea, it increased in the northern Barents and Kara Seas, indicating that the cooling machine has expanded poleward. According to climate model projections, it is very likely that the cooling machine will continue to expand to the Kara Sea and then to the Arctic Basin in a warming climate. As a result, the Arctic Atlantification will be enhanced and pushed poleward in the future.