Ice-covered Waters Research Articles

Estimation of travel time reduction for ice-breaking ships when considering ice information data

Abstract In light of the recent increase in polar shipping and potential future increase with continued climate change reliable routing in ice-covered waters becomes increasingly important for environmental, economic and safety concerns. Dependable route suggestions have the potential to reduce travel times through polar waters significantly. We apply the Anytime Repairing A* pathfinding algorithm to classified Copernicus Sentinel 1 radar images to estimate how much travel times can be reduced. For multiple example scenarios, it is quantified how much the travel time is reduced if a ship follows these suggestions compared to navigating without any ice information available exterior to the visual range (VR). It was found that having ice information available is most beneficial in complex ice situations, where it can reduce travel time by up to 34% for a VR of 2 km.

Extreme mismatch between phytoplankton and grazers during Arctic spring blooms and consequences for the pelagic food-web

Food-web structure determines the cycling pathways and fate of new production in marine ecosystems. Herbivorous zooplankton populations are usually seasonally coupled with pelagic primary producers. Synchrony of phytoplankton blooms with reproduction, recruitment and seasonal ascent of their main grazers ensures efficient transfer of organic carbon to higher trophic levels, including commercially harvested species, especially in high-latitude systems. Changes in light, nutrient, and sea-ice dynamics due to accelerating climate change in the Arctic, however, create large uncertainties in how these systems will function in the future. To address such knowledge gaps, we surveyed the pelagic ecosystem of the Barents Sea Polar Front in May of two consecutive years (2021 and 2022) to investigate the pelagic food-web from primary producers to planktivorous fish. In both years we observed unprecedentedly high phytoplankton chlorophyll a values in open as well as ice-covered waters, much of which was invisible to satellite remote sensing. We also measured very low densities of grazing zooplankton across a wide area and extending for at least one month. This extreme mismatch resulted in low feeding by capelin, and further suggests a high potential for vertical export of carbon to the benthos rather than efficient assimilation into the pelagic food web. As the Arctic continues to warm and is characterized by thinner and more mobile sea ice, we may expect higher variability in phytoplankton bloom phenology and more frequent mismatches with grazer life-histories. This could have significant impacts on ecosystem functioning by re-directing the flow of energy through the system towards seafloor rather than to the production of commercially valuable pelagic marine resources.

Advanced Human Reliability Analysis Approach for Ship Convoy Operations via a Model of IDAC and DBN: A Case from Ice-Covered Waters

The melting of Arctic ice has facilitated the successful navigation of merchant ships through the Arctic route, often requiring icebreakers for assistance. To reduce the risk of accidents between merchant vessels and icebreakers stemming from human errors during operations, this paper introduces an enhanced human reliability assessment approach. This method utilizes the Dynamic Bayesian Network (DBN) model, integrated with the information, decision, and action in crew context (IDAC) framework. First, a qualitative analysis of crew maneuvering behavior in scenarios involving a collision with the preceding vessel during icebreaker assistance is conducted using the IDAC model. Second, the D–S evidence theory and cloud models are integrated to process multi-source subjective data. Finally, the human error probability of crew members is quantified using the DBN. The research results indicate that during convoy operations, the maximum probability that the officer on watch (OOW) chooses an incorrect deceleration strategy is 8.259×10−2 and the collision probability is 4.129×10−3. Furthermore, this study also found that the factors of Team Effectiveness and Knowledge/Abilities during convoy operations have the greatest impact on collision occurrence. This research provides important guidance and recommendations for the safe navigation of merchant ships in the Arctic waters. By reducing human errors and adopting appropriate preventive measures, the risk of collisions between merchant ships and icebreakers can be significantly decreased.

Iron cycling and isotopic fractionation in a ferruginous, seasonally ice-covered lake

Ferruginous conditions, defined by anoxia and abundant dissolved ferrous iron (Fe2+aq), dominated the Precambrian oceans but are essentially non-existent in a modern, oxygenated world. Ferruginous meromictic lakes represent natural laboratories to ground truth our understanding of the stable Fe isotope proxy, which has been used extensively in interpreting the origins of Fe-rich sedimentary rocks like iron formations (IFs) and the interactions of early life with high-Fe2+aq conditions. Here we report comprehensive geochemical and Fe isotopic analyses of samples collected in May and August 2022, and March 2023, from Deming Lake, Minnesota, a ferruginous meromictic lake that undergoes surface freezing in winter and never becomes euxinic. Through chemical and Fe isotopic analyses of different putative Fe sources to Deming Lake; including eolian input trapped in winter ice cover, nearby bogs, and regional groundwaters sampled at surface springs; we find that a groundwater source provides the best chemical and Fe isotopic match for Deming Lake and can support Fe2+aq-rich waters at depth that maintain a permanent chemocline at ∼12 m. The ice-free Deming Lake water column can be split into three layers dominated by distinct Fe cycling regimes. Layer (I) extends from the lake surface to the base of the oxycline at ∼6 m, and its Fe cycling is dominated by isotopically light Fe uptake into biomass, likely from stabilized dissolved Fe3+, with variable eolian lithogenic influences. Layer (II) extends between the oxycline and the chemocline at ∼12 m and is dominated by partial Fe2+aq oxidation on approach to the oxycline, with the formation of variably isotopically heavy Fe3+-bearing particles. Layer (III) underlies the chemocline and is defined by Fe2+ phosphate (vivianite) and carbonate saturation and precipitation under anoxic, Fe2+aq-rich conditions with little Fe isotopic fractionation. The ice-covered winter water column features more homogenous Fe chemistry above the chemocline, which we attribute to seasonal homogenization of Layers (I) and (II), with suppressed ferric particle formation. Authigenic Fe minerals with non-crustal (light) Fe isotopic compositions only appreciably accumulate in sediments in Deming Lake underlying the chemocline. All sediments deposited above 12 m appear crustal in their Fe isotopic, Mn/Fe, and Fe/Al ratios, likely revealing efficient reductive dissolution of Fe3+-bearing lake precipitates and remineralization of Fe-bearing biomass. We find limited fractionation of Fe isotopes in the ice-covered water column and suggest this provides evidence that substantial delivery of oxidants is required to generate highly fractionated Fe isotopic compositions in Sturtian Snowball era IFs. By comparing Fe isotopic and Mn/Fe fractionation trends in the different Deming Lake layers, we also suggest that correlations between these two parameters in giant early Paleoproterozoic IFs requires the simultaneous deposition of multiple authigenic phases on the ancient seafloor. Finally, high-precision triple Fe isotopic analyses of dissolved Fe impacted by extensive oxidation near the Deming Lake oxycline reveal that the slope of the mass fractionation law for natural, O2-mediated Fe2+aq oxidation is identical to those previously defined for both UV photo-oxidation, and for an array of highly fractionated Paleoproterozoic IFs.

Influence of Propeller–Ice Loads on the Wear Development in Stern Tube Bearings of Marine Propulsion Systems and Identification of Critical Operating Conditions

Abstract Increasing ship traffic in ice-covered waters leads to more frequent collisions between ship propellers and sea ice which causes extreme impulse loads on the propeller. These loads are transferred through the propeller shaft to the sliding bearings of the stern tube, especially, the aft stern tube bearings. Extreme bearing loads can lead to mixed friction regimes that cause wear in the bearings and eventually result in a failure of the entire propulsion system. The effect of ice-induced loads on the contact conditions in the sliding bearings is widely unknown. Thus, a study of the influence of these loads on the contact conditions and wear behavior in stern tube bearings resulting from observed sea ice conditions and operating conditions of the ship is necessary. This article aims to investigate the influence of ice collision loads on the contact conditions in the bearings of the stern tube of the research vessel SA Agulhas II. For this purpose, an elastohydrodynamic simulation and a multibody simulation based on field measurements were performed. As a result, this article identifies the operating condition thresholds (i.e., propeller torque and rotational speed) during propeller–ice collisions that cause mixed friction conditions in the bearings. On the basis of these conditions, a risk map is generated to assess the actual wear risk by including the frequency of occurrence of the corresponding mixed friction condition over the duration of a voyage.

Pre-Construction predictions of the Loads from large Ice Ridges Interacting with the Confederation Bridge Piers

During the design phase of the Confederation Bridge in Canada, the Canadian government Public Works and Government Services Canada asked the National Research Council (NRC) of Canada to provide information on ice loads from large ridges using a wide range of predictive technologies. The NRC put together a team that looked at loads from several sources including analytical models, physical model tests, finite element models, discrete particle models, and full-scale data. The ice loading scenario was an extreme first-year ridge loading one of the bridge piers. A large number of analytical models were used and the load components were separated into those from the consolidated layer, the sail, and the keel. An upper bound prediction from this approach gave a value of 16 MN on a pier, but the assumptions that were used to arrive at this value did not match observed behavior in the physical and numerical studies of the program. Physical model tests indicated that the loads could be 10.5 MN with a load of 7.3 MN from the keel and 3.2 MN from the consolidated layer and sail. A finite element analysis indicted a range of predicted values of 10 MN to 12 MN depending upon the assumptions used. A discrete particle analysis predicted load values from 2.2 MN to 9.5 MN depending upon the assumptions used in describing the stiffness of the ridge. A review of full-scale measurements on lighthouses and ships suggested that the loads could range from 7.3 MN to 10.4 MN. These predicted values compare to the highest load measured on the Confederation Bridge over a twenty-year span of just over 8 MN. This paper outlines the approaches used for this prediction study and their resulting predictions. It shows the value of using multiple approaches for load predictions for offshore structures in ice-covered waters.

A kinematic model for collaborative icebreaker convoy operations in ice-covered waters

Icebreaker assistance is a common yet intricate operation in ice-covered waters, frequently leading to collisions between ships and icebreakers. This underscores the need for advanced kinematic models to improve safety and coordination in convoy operations. Consequently, this paper introduces a kinematic model for guiding intelligent ships under icebreaker assistance. The model, grounded in the Traffic Factor State Network (TFSN), evaluates the safety state of a fleet in various ice conditions, using data from actual convoy operations. An enhanced Proportional Integral Derivative (PID) algorithm is integrated to formulate a multi-ship following model, which accounts for the kinematic characteristics of ships in ice. The model also incorporates the transmission process of ship maneuvering commands. Its validity is confirmed through application to two ships under icebreaker assistance. The findings show that the model effectively simulates safe speeds and maintains proper inter-ship distances over time, and it generates safe kinematic instructions for the fleet. This model may contribute to navigational safety in ice-covered waters and demonstrates the potential for inclusion in ice navigation support systems.

Investigation of ice wedge bearing capacity based on an anisotropic beam analogy

Ships and offshore structures operating in ice-covered waters need to be able to break ice. The hulls of ships and offshore structures are often designed to be inclined so that an out-of-plane force can be incurred to initiate flexural failure. During this process, an in-plane force co-exists as the result of the hull inclination, which can affect the bending process and alter the magnitude of interaction force. Additionally, the loading process can be rapid and incur dynamic effect within the ice sheet, resulting in higher peak loads compared to the scenario of quasi-static loading. The effect of in-plane force and loading speed, however, are often neglected in the modelling of the icebreaking process in order to enable simplified solutions of analytical form, which leads to deviations in the estimation of ice loads. This paper aims to investigate the effects of in-plane force and loading speed on the ice bearing capacity during the icebreaking process. This is conducted via the Finite Element Analysis (FEA) with the Cohesive Element Method (CEM). An anisotropic beam analogy concept is proposed to model a 3D ice wedge with a 2D beam which has varying properties along the axial direction. The analogy enables fast and stable simulation of ice crack propagation through its thickness direction, while maintaining properties of the ice wedge in 3D. The analogy is verified with Nevel's closed-form solution for a narrow wedge resting on an elastic foundation. After that, the beam is loaded with a rigid wall with different inclination angles and loading speeds. The results reveal that the in-plane force and loading speed have significant influence on the icebreaking process, resulting in different bearing capacity and overall energy consumption. Based on the numerical results, a regression study is conducted to derive a correction coefficient accounting for the joint effect of in-plane force and loading speed on the bearing capacity, which can be incorporated into ice-structure interaction simulation models.

On the data-driven investigation of factors affecting the need for icebreaker assistance in ice-covered waters

Merchant vessels often require icebreaker (IB) assistance to create safe pathways and improve efficiency when navigating in the Baltic Sea. Since IB resources are limited, an accurate estimation on the need for IB assistance is important. Whether IB assistance is needed depends on multiple factors. While practical experience from captains is naturally a source of valuable information for the decision on the need for IB assistance, systematic analysis of the reasoning is limited. The primary aim of this paper is to holistically investigate the influencing factors and their effect on estimating the need for IB assistance through data-driven techniques. Based on a comprehensive list of potential factors, different of data such as traffic history, environmental conditions, and ship specifications are gathered to present complex navigational scenarios. Each scenario is labeled by different navigation modes (independent navigation or IB assistance), laying the foundation for influencing factor identification and effect quantification. Logistic regression is applied to evaluate the effect of the factors on the need for IB assistance. The results show that the impact of the factors is diverse, and ridged ice concentration has the most significant impact. The effectiveness of identified factors is measured by comparing it to that of the factors that have been implemented by the existing studies (e.g., the combination of ice concentration, thickness, and ship ice class, or only ship speed). By considering the factors in this study, the classification performance can be improved by at least 5.6%. The findings in this paper can provide insights for predicting IB workloads and optimizing IB resources and have the potential to support the development of an intelligent decision-support system for winter navigation.

Fatigue Performance Analysis of an Underwater Vehicle Rudder Mechanism Considering Arctic Low Temperatures

For underwater vehicles navigating in Arctic Sea ice-covered waters, fatigue damage is a crucial issue. Many scholars have conducted low-temperature fatigue analysis on low-temperature materials and substrate platforms for ships, and the results show that low temperature is beneficial for improving the mechanical properties of materials. However, they have mainly focused on low-temperature performance experiments and simulation analysis of standard components of materials, and there are very few fatigue life experimental studies on underwater vehicle mechanical structures. This paper conducts experimental investigations on a scaled model of an underwater vehicle rudder mechanism in a polar environment laboratory. Using a comparative analysis method involving simulations and experiments, the low-temperature fatigue test data of the scaled underwater vehicle rudder mechanism are analyzed, and the quantified analysis between fatigue and different low-temperature loading cycles, as well as the influence of icing on the fatigue life, is explored. It is indicated that the Arctic environment can decrease the fatigue life of the underwater vehicle rudder mechanism by deteriorating its material properties. The paper builds the foundation for the fatigue life of an underwater vehicle rudder mechanism in Arctic low-temperature environments.

Impact of changes in sea ice cover on the wave climate of semi-enclosed, seasonally ice-covered water bodies at temperate latitudes: a case study in the Gulf of Riga

Impact of changes in sea ice cover on the wave climate of semi-enclosed, seasonally ice-covered water bodies at temperate latitudes: a case study in the Gulf of Riga

Diversity of microbial communities in long-term ice-covered water bodies of the Cold Pole region, Yakutia

Water bodies located in the north-east of Yakutia during the period of ice cover were studied. High-throughput sequencing of 16S rRNA gene libraries revealed a high taxonomic diversity of microbial communities in the studied ecotopes. The majority of the under-ice communities was represented by Proteobacteria, Actinobacteriota, Cyanobacteria, Verrucomicrobiota, Bacteroidota, and Planctomycetota. The difference in community diversity between deep-water lakes Labynkyr, Vodorazdelnoye, and Ulu, the source of the Labynkyr River, and shallow-water lakes Myamichi and Mertvoye, the mouth of the Labynkyr River, is shown.

Development and calibration of a high dynamic range and autonomous ocean-light instrument to measure sub-surface profiles in ice-covered waters.

The optical chain and logger (OptiCAL) is an autonomous ice-tethered observatory equipped with multiple light sensors for mapping the variation of light with depth. We describe the instrument and present an ensemble calibration for downwelling irradiance E P A R in [µm o l m -2 s -1]. Results from a long-term deployment in the Arctic Ocean demonstrate that the OptiCAL can cover the high dynamic range of under-ice light levels from July to November and produce realistic values in terms of magnitude when compared to modeled surface irradiance. Transient features of raised light levels at specific depths associated with nearby leads in the ice underline the importance of depth-resolved light measurements.

Alternative method for determining available winter water volumes from lakes to support small-scale projects

Abstract In Canada's Northwest Territories (NT), industrial activities conducted during the winter, such as ice road construction and exploratory drilling, require the use of water from ice-covered water bodies. Withdrawal in excess of 10% of available under-ice volume can threaten fish habitat or other users. The Land and Water Boards (LWBs) of the Mackenzie Valley require water licences for water withdrawal beyond regulated thresholds. Applicants must provide information including identification and location of proposed water sources, timing and proposed volume of water and winter water withdrawal must be limited to <10% of available volume to protect fish habitat under the ice. Many applicants are at early project stages and the necessary information on bathymetry and volumes of water is not readily available or requires expertise and effort that may not be feasible at the early stages of smaller projects. This paper describes the alternative method for determining available winter water volumes from lakes to support small-scale projects. A simple formula of ‘allowable volume (m3) = surface area (m2) * 0.1 m’ was developed and tested to provide a conservative estimate of under-ice volumes from easily available data which is protective in spite of uncertainties inherent in limited data.

Route optimization for vessels in ice: Investigating operational implications of the carbon intensity indicator regulation

The International Maritime Organization has adopted the Carbon Intensity Indicator (CII) regulation to promote decarbonization of shipping operations. The CII regulation includes specific treatment for vessels sailing in ice, which allows the time spent in ice, the associated emissions and transport work, to be excluded from the reported annual CII. The current study investigates the implications and possible side effects of this exemption in all ice-covered waters. A proposed model integrates the CII regulation into a route optimization tool for vessels in ice. The research decomposes the regulation from evaluating an annual CII value to monitoring an instantaneous CII value over a unit distance. A ship performance model is used to estimate resistance, powering, and fuel consumption. A graph-based pathfinding method is applied to find optimal routes and speeds for the vessel. A hypothetical bulk carrier with ice class 1A Super operating in the Canadian Arctic is considered as a case study. The Polar Operational Limit Assessment Risk Indexing System is applied to promote safe operations in ice. The demonstrations explore route optimization with and without CII considerations, including the exemption for ships sailing ice. The results show that the CII regulation promotes reduced speeds to curb fuel consumption and carbon emissions. The findings also indicate that the exemption for sailing in ice conditions influences routing decisions with results that are contrary to the intent of the regulation. This research provides a tool to support ship operators with voyage planning and policy-makers in evaluating the impact of the CII regulation.

Numerical Simulation of Turbulent Mixing in a Shallow Lake for Periods of Under-Ice Convection

The article presents the results of application of Implicit Large Eddy Simulation method to numerical simulation of under-ice radiatively driven convection, developing in ice-covered water bodies in the moderate zone at the end of freeze-up period. Studies of the radiatively driven convection are of importance because of the role it plays in the temperature regime of lakes and the functioning of lake ecosystems at the end of freeze-up period. The simulation was carried out with the use of the finite-volume software code SINF/Flag-S, developed in SPbPU. The SIMPLEC algorithm with second-order accuracy was used for ad­vancing in time. The discretization of the convective terms was made with the use of QUICK scheme. The results of calculations were used to study variations in the temperature and pulsation velocity components with periodically varying intensity of external energy pumping during the daily cycle. The dissipation of the kinetic energy, background potential energy, and buoyancy flux were evaluated, and changes in these variables during a daily cycle of radiation impact were calculated. The efficiency mixing of water column was evaluated for the period of development of radiatively driven convection in a model domain simulating a small lake covered by ice.

Fast and Intelligent Ice Channel Recognition Based on Row Selection

The recognition of ice channels plays a crucial role in developing intelligent ship navigation systems in ice-covered waters. Navigating through ice channels with the assistance of icebreakers is a common operation for merchant ships. Maneuvering within such narrow channels presents a significant challenge for the captain’s skills and ship performance. Therefore, it becomes essential to explore methods for enabling ships to navigate through these channels automatically. A key step in achieving this is the accurate recognition and extraction of boundary lines on both sides of the ice channel. An ice channel line recognition method based on the lane line detection algorithm UFAST is implemented. The method is trained and tested on the constructed ice channel dataset, with the test results showing that the average recognition accuracy reaches 84.1% and the recognition speed reaches 138.3 frames per second, meeting the real-time requirement. In order to solve the current lack of authentic ice channel images, ice channel navigation scenes are built based on UE4, and synthetic ice channel images are rendered. The method in this paper is also compared with the traditional non-intelligent Otsu threshold segmentation method and the intelligent instance segmentation method YOLACT for performance analysis. The method in this paper has 9.5% higher ice channel recognition accuracy and 103.7 frames per second higher recognition speed compared with YOLACT. Furthermore, ablation studies are conducted to analyze the relationship between the number of gridding cells in the proposed method and ice channel recognition accuracy.

A multi-objective optimisation strategy for ice navigation under ship safety-following scenarios

Shipping activities in the Northern Sea Route (NSR) are increasing. However, due to the complex sea ice conditions, ships still need assistance of icebreakers when sailing through most Arctic waters. Icebreaker escort operations are important to ensure the safe passage of ships through ice-covered waters, but the speed of following ships will be limited, thus creating challenges for NSR sailing economics and emission reduction issues. Optimizing the sailing speed of following ships can reduce NSR ship emissions and improve navigation economy while safeguarding their sailing safety. In this paper, a green, economical and safe optimization approach under ship-following navigation has been developed by drawing on similarities with the car-following phenomenon. Then, three ship-following scenarios are designed for simulating the actual ice navigation conditions. Finally, a cost-eco-efficiency multi-objective optimisation model for ice navigation is established, and the performance of the proposed model is demonstrated by the navigation case of “Tian You”. The results show that the proposed model can effectively reduce navigation costs and control navigation emissions while ensuring navigation safety. This study also demonstrates that there is still room for a 20% improvement in the optimised speed and a 4.8% reduction in the ship-following distance compared to the actual situation.

Mapping vessel traffic patterns in the ice-covered waters of the Pacific Arctic

Recent climate change has caused declines in ice coverage which have lengthened the open water season in the Arctic and increased access to resources and shipping routes. These changes have resulted in more vessel activity in seasonally ice-covered regions. While traffic is increasing in the ice-free season, the amount of vessel activity in the marginal ice zone (ice concentration 15–80%) or in pack ice (>80% concentration) remains unclear. Understanding patterns of vessel activities in ice is important given increased safety challenges and environmental impacts. Here, we couple high-resolution ship tracking information with sea ice thickness and concentration data to quantify vessel activity in ice-covered areas of the Pacific Arctic (northern Bering, Chukchi, and western Beaufort Seas). This region is a geo-strategically critical area that contains globally important commercial fisheries and serves as a corridor for Arctic access for wildlife and vessels. We find that vessel traffic in the marginal ice zone is widely distributed across the study area while vessel traffic in pack ice is concentrated along known shipping routes and in areas of natural resource development. Of the statistically significant relationships between vessel traffic and both sea ice concentration and thickness, over 99% are negative, indicating that increasing sea ice is associated with decreasing vessel traffic on a monthly time scale. Furthermore, there is substantial vessel traffic in areas of high concentration for bowhead whales (Balaena mysticetus), and traffic in these areas increased four-fold during the study period. Fishing vessels dominate vessel traffic at low ice concentrations, but vessels categorized as Other, likely icebreakers, are the most common vessel type in pack ice. These findings indicate that vessel traffic in areas of ice coverage is influenced by distant policy and resource development decisions which should be taken into consideration when trying to predict future vessel-ice interactions in a changing climate.

Hybrid causal logic model for estimating the probability of an icebreaker–ship collision in an ice channel during an escort operation along the Northeast Passage

Under severe Arctic ice conditions, escort operations are the most efficient methods for facilitating shipping. Nevertheless, escort operations are among the most dangerous operations, as they may result in icebreaker–ship collisions and/or ship besetting in ice. To mitigate the risk of collisions, it is essential to understand the event sequences of collisions and the risk control options that can be implemented to reduce the occurrence of undesired events. This paper proposes a hybrid causal logic model to estimate the likelihood of an icebreaker–ship collision while considering human factors during an escort operation along the Northeast Passage. The model relies on inputs from four icebreaker captains. Its applicability is demonstrated for a 2018 summer voyage of a cargo ship assisted by an icebreaker. Risk control options are then proposed based on qualitative and sensitivity analyses of the model. The results of this study can assist shipping companies to better understand the sequence of events prior to icebreaker–ship collisions during escort operations in ice-covered waters. This paper provides information on risk reduction measures. In addition, the proposed model can assist in route planning.