Operational failure assessment of Remotely Operated Vehicle (ROV) in harsh offshore environments

For an effective integrity assessment of marine robotic in offshore environments, the elements’ failure characteristics need to be understood. A structured probabilistic methodology is proposed for the operational failure assessment (OFA) characteristics of ROV. The first step is to assess the likely failure mode of the ROV system and its support systems. This captures the interaction and failure induced events during operation. The identified potential failure modes are further developed into logical connectivity based on the cause-effect relationship. The logical framework is modeled using the fault tree analysis technique to predict the ROV operational failure probability in an uncertain harsh environment. The fault tree analysis captured the logical relationship between the primary, intermediate, and top events probability. The importance measure criteria were adopted to identify the most probable events, links, and their importance on the failure propagation. The model was demonstrated with an ROV for deep arctic water subsea operations. The result identified the control system, communication linkages, human factor, among others, as most critical in the ROV operational failure. The methodology’s application provides core information on the Mean time between failure (MTBF) of the ROV system that could aid integrity management and provides a guide on early remedial action against total failure.

Modeling of hydrocarbon systems and quantitative assessment of the hydrocarbon potential of Eastern Arctic seas

Background. Three prospective sedimentary complexes — Aptian-Upper Cretaceous, Paleogene and Neogene — are predicted in the waters of the Eastern Arctic seas. Here, the search for oil and gas is associated with harsh Arctic conditions at sea, as well as with high geological risks and significant expenditures under the conditions of poor knowledge of the region. In this regard, the localisation of prospecting drilling objects and the assessment of the geological risks of deposit discovery should be carried out.Aim. To assess geological risks and to determine the probability of discovering oil and gas fields, as well as to identify prospective areas for licensing and exploration in the water areas of the Eastern Arctic.Materials and methods. Structural and heat flow maps along with the results of geochemical analysis, as well as typical terrestrial sections were used as initial materials. Using the method of basin analysis, the modelling of generation-accumulation hydrocarbon systems (GAHS) and the quantitative assessment of its hydrocarbon potential in the Eastern Arctic water area was carried out. The assessment of geological risks and the probability of field discovery was performed using the conventional methodology widely applied by oil companies.Results. The GAHS modelling using a variation approach showed that, regardless of the kerogen type, with average values of Сorg in sediments, potential oil-and-gas source strata (OGSS) were capable of saturating the prospective objects with hydrocarbons. The “OGSS assessment” factor was determined as “encouraging” (0.7). Active geodynamic regime and the manifestation of several folding phases within the study area provided favourable conditions for the formation of anticlinaltraps in sedimentary basins. However, the cap rock quality rating was assessed as “neutral” (0.5). The overall risk for the “Trap assessment” factor was estimated based on the minimum criterion of 0.5.Conclusion. The most prospective areas recommended for licensing were selected, and the recommendations for further geological exploration work in these areas were given in order to clarify their hydrocarbon potential and reduce geological risks.

Viral characteristics of the warm Atlantic and cold Arctic water masses in the Nordic Seas

Nordic Seas are the subarctic seas connecting the Arctic Ocean and North Atlantic Ocean with complex water masses, experiencing an abrupt climate change. Though the knowledge of the marine virosphere has been expanded rapidly, the diversity of viruses and their relationships with host cells and water masses in the Nordic Seas remains to be fully revealed. Here we establish the Nordic Seas DNA viromes (NSVs) dataset of 55,315 viral contigs including 1,478 unique viral populations from seven stations influenced by both the warm Atlantic and cold Arctic water masses. Caudovirales dominated in the seven NSVs, especially in the warm Atlantic waters. The major giant nucleocytoplasmic large DNA viruses (NCLDVs) contributed a significant proportion of the classified viral contigs in the NSVs (32.2%), especially in the cold Arctic waters (44.9%). The distribution patterns of Caudovirales and NCLDVs were a reflection of the community structure of their hosts in the corresponding water masses and currents. Latitude, pH, and flow speed were found to be key factors influencing the microbial communities and co-influencing the variation of viral communities. Network analysis illustrated the tight coupling between the variation of viral communities and microbial communities in the Nordic Seas. This study suggests a probable linkage between the viromes, host cells and the surface water masses from both the cool Arctic and warm Atlantic Oceans. Importance: This is a systematic study of Nordic Seas Viromes using metagenomic analysis. The viral diversity, community structure, and their relationships with host cells and the complex water masses from both the cool Arctic and warm Atlantic Oceans were illustrated. The NCLDVs and Caudovirales are proposed as the viral characteristics of the cold Arctic and the warm Atlantic waters, respectively. This study provided an important background for the viromes in the subarctic seas connecting the Arctic Ocean and North Atlantic Ocean, and will shed a light on their responses to the abrupt climate change in the future.

Within-Arctic horizontal gene transfer as a driver of convergent evolution in distantly related microalgae

The Arctic Ocean is being impacted by warming temperatures, increasing freshwater and highly variable ice conditions. The microalgal communities underpinning Arctic marine food webs, once thought to be dominated by diatoms, include a phylogenetically diverse range of small algal species, whose biology remains poorly understood. Here, we present genome sequences of a cryptomonad, a haptophyte, a chrysophyte, and a pelagophyte, isolated from the Arctic water column and ice. Comparing protein family distributions and sequence similarity across a densely-sampled set of algal genomes and transcriptomes, we note striking convergences in the biology of distantly related small Arctic algae, compared to non-Arctic relatives; although this convergence is largely exclusive of Arctic diatoms. Using high-throughput phylogenetic approaches, incorporating environmental sequence data from Tara Oceans, we demonstrate that this convergence was partly explained by horizontal gene transfers (HGT) between Arctic species, in over at least 30 other discrete gene families, and most notably in ice-binding domains (IBD). These Arctic-specific genes have been repeatedly transferred between Arctic algae, and are independent of equivalent HGTs in the Antarctic Southern Ocean. Our data provide insights into the specialised Arctic marine microbiome, and underlines the role of geographically-limited HGT as a driver of environmental adaptation in eukaryotic algae.

Hydroclimatic Controls on the Isotopic (δ18 O, δ2 H, d-excess) Traits of Pan-Arctic Summer Rainfall Events

Arctic sea-ice loss is emblematic of an amplified Arctic water cycle and has critical feedback implications for global climate. Stable isotopes (δ18O, δ2H, d-excess) are valuable tracers for constraining water cycle and climate processes through space and time. Yet, the paucity of well-resolved Arctic isotope data preclude an empirically derived understanding of the hydrologic changes occurring today, in the deep (geologic) past, and in the future. To address this knowledge gap, the Pan-Arctic Precipitation Isotope Network (PAPIN) was established in 2018 to coordinate precipitation sampling at 19 stations across key tundra, subarctic, maritime, and continental climate zones. Here, we present a first assessment of rainfall samples collected in summer 2018 (n = 281) and combine new isotope and meteorological data with sea ice observations, reanalysis data, and model simulations. Data collectively establish a summer Arctic Meteoric Water Line where δ2H = 7.6⋅δ18O–1.8 (r2 = 0.96, p < 0.01). Mean amount-weighted δ18O, δ2H, and d-excess values were −12.3, −93.5, and 4.9‰, respectively, with the lowest summer mean δ18O value observed in northwest Greenland (−19.9‰) and the highest in Iceland (−7.3‰). Southern Alaska recorded the lowest mean d-excess (−8.2%) and northern Russia the highest (9.9‰). We identify a range of δ18O-temperature coefficients from 0.31‰/°C (Alaska) to 0.93‰/°C (Russia). The steepest regression slopes (>0.75‰/°C) were observed at continental sites, while statistically significant temperature relations were generally absent at coastal stations. Model outputs indicate that 68% of the summer precipitating air masses were transported into the Arctic from mid-latitudes and were characterized by relatively high δ18O values. Yet 32% of precipitation events, characterized by lower δ18O and high d-excess values, derived from northerly air masses transported from the Arctic Ocean and/or its marginal seas, highlighting key emergent oceanic moisture sources as sea ice cover declines. Resolving these processes across broader spatial-temporal scales is an ongoing research priority, and will be key to quantifying the past, present, and future feedbacks of an amplified Arctic water cycle on the global climate system.

Spatial Distribution of Arctic Bacterioplankton Abundance Is Linked to Distinct Water Masses and Summertime Phytoplankton Bloom Dynamics (Fram Strait, 79°N)

The Arctic is impacted by climate warming faster than any other oceanic region on Earth. Assessing the baseline of microbial communities in this rapidly changing ecosystem is vital for understanding the implications of ocean warming and sea ice retreat on ecosystem functioning. Using CARD-FISH and semi-automated counting, we quantified 14 ecologically relevant taxonomic groups of bacterioplankton (Bacteria and Archaea) from surface (0–30 m) down to deep waters (2,500 m) in summer ice-covered and ice-free regions of the Fram Strait, the main gateway for Atlantic inflow into the Arctic Ocean. Cell abundances of the bacterioplankton communities in surface waters varied from 105 cells mL–1 in ice-covered regions to 106 cells mL–1 in the ice-free regions. Observations suggest that these were overall driven by variations in phytoplankton bloom conditions across the Strait. The bacterial groups Bacteroidetes and Gammaproteobacteria showed several-fold higher cell abundances under late phytoplankton bloom conditions of the ice-free regions. Other taxonomic groups, such as the Rhodobacteraceae, revealed a distinct association of cell abundances with the surface Atlantic waters. With increasing depth (>500 m), the total cell abundances of the bacterioplankton communities decreased by up to two orders of magnitude, while largely unknown taxonomic groups (e.g., SAR324 and SAR202 clades) maintained constant cell abundances throughout the entire water column (ca. 103 cells mL–1). This suggests that these enigmatic groups may occupy a specific ecological niche in the entire water column. Our results provide the first quantitative spatial variations assessment of bacterioplankton in the summer ice-covered and ice-free Arctic water column, and suggest that further shift toward ice-free Arctic summers with longer phytoplankton blooms can lead to major changes in the associated standing stock of the bacterioplankton communities.

Terrestrial sources of summer arctic moisture and the implication for arctic temperature patterns

Sea ice melt and ocean heat accumulation in the Arctic are strongly influenced by the presence of atmospheric water vapor during summer. While the relationships between water vapor concentration, radiation, and surface energy fluxes in the Arctic are well understood, the sources of summer Arctic water vapor are not, inhibiting understanding and prediction of Arctic climate. Here we use the Community Earth System Model version 1.3 with online numerical water tracers to determine the geographic sources of summer Arctic water vapor. We find that on average the land surface contributes 56% of total summer Arctic vapor with 47% of that vapor coming from central and eastern Eurasia. Given the proximity to Siberia, near-surface temperatures in the Arctic between 90°E-150°E, including the Laptev Sea, are strongly influenced by concentrations of land surface-based vapor. Years with anomalously large concentrations of land surface-based vapor in the Arctic, and especially in the Laptev Sea region, often exhibit anomalous near-surface poleward flow from the high latitudes of Siberia, with links to internal variability such as the Arctic Dipole anomaly.

The Prospects of Evolution of the Baseline Systems in the Arctic

The article discusses the notion of “baselines” and the legal framework for drawing them, as well as the practice of drawing baselines, primarily by the coastal Arctic states. As a result of analysis, we make a suggestion that the existing system of baselines in the Arctic Ocean seas may evolve on the basis of international legal rules, with due account taken of the practice of applying them, and through the use of such a legal concept as “historic waters.” The article covers the interpretation of the concept of “historic waters” in various sources, indicating how this concept is used by different states to proclaim their rights to adjacent maritime areas on historical grounds. We have drawn on our extensive research and documents identified that may be used by the Russian Federation to expand its “historic waters” on the Arctic coast. At the same time, we have not aimed at making specific proposals on changing the location of the existing baselines or declaring new Arctic water areas “historic waters.” Rather, our objective was to comprehensively study the possibility of preparing such proposals.