Due to the gradual decrease in flow of the Atlantic Meridional Overturning Circulation (AMOC) and given the geographical position, a change in climate in the Netherlands is expected (Van den Dool, 2025) & (Carrington, Damian, 2025). The AMOC transports warm ocean water to Northern Europe leading to a temperate maritime climate in the Netherlands. A gradually decreasing or complete collapse of the AMOC certainly results in a colder Northern Europe. Resulting lower air and surface temperatures, will impact ice formation on rivers, such as the Maas. Other claims of consequences in case of an AMOC collapse are: less precipitation in Europe, and faster sea level rise in the Atlantic Ocean (Van den Dool, 2025).

Arctic sea ice is retreating at a high rate, also due to the positive ice-albedo feedback loop: as ice melts and disappears, it reflects less sunlight, further accelerating ocean warming. One proposed way to slow the retreat is by thickening sea ice in winter, increasing its chances of surviving summer melt. This could be achieved by artificially flooding existing sea ice with seawater pumped from below, allowing it to freeze at the surface through exposure to cold air and thicken the ice layer. However, the effectiveness of this approach remains uncertain, as numerical models show contrasting results and few field experiments have been conducted. This study examines the growth and melt of ice through spring and summer after artificial flooding covering (Formula presented.), resulting in thickened (+26 cm) snow-covered first-year sea ice. Observations were carried out in Vallunden Lagoon (Van Mijenfjord), Svalbard, from 20 March to 24 June 2024, with flooding and intensive in situ measurements from 11–15 April. Artificial flooding significantly heated the upper two-thirds of the original 90 cm thick ice, increasing salinity. Surface albedo evolution was influenced by specific events such as slush formation, snow drift, and a major meltwater drainage event in spring. Artificial flooding resulted in thicker ice and delayed rotten ice formation by 6 days, but did not delay the disappearance of ice in summer compared to a non-flooded reference site. Experiments at other scales and locations could help reveal how local conditions and flooded area size influence results and the potential of this method.

The design of flexible vertical offshore structures exposed to ice, like offshore wind turbines, can become governed by ice loads and structural responses at low relative ice speeds. This study attempts to quantify the low-speed ice loads based on a hypothesized interaction mechanism linking the velocity dependence of global loads to specific states of the ice supported by model- and full-scale observations. The quantified velocity effect is applied to estimate potential global pressures at low speeds from high-speed crushing events from the full-scale measurement campaign at the Norströmsgrund lighthouse. It is estimated that the velocity effect may produce global pressures equivalent to applying an ice strength coefficient of 0.9 MPa to 1.6 MPa. These results substantiate an alternative physics-informed approach to account for the velocity effect for ice loads and provide an interpretation of the interaction scenario captured by the 1.8 MPa value in the ISO19906 design standard.

Offshore wind turbines in cold sea areas can be fitted with ice cones to reduce static and dynamic loads from drifting sea ice. The effectiveness of ice cones in reducing static loads has been tested in model-scale ice basin experiments. However, only a few experiments used compliant test setups to study ice-induced vibrations on conical structures. This study explores the dynamic interaction between level ice and a downward-bending cone with a 60° slope angle through ice basin tests with a hardware-in-the-loop system based on a hybrid technique, combining a physical indenter with a numerical structure model of an offshore wind turbine. Two types of periodic ice-induced vibrations were observed for the first time in an ice basin: bending failure-induced vibrations and unexpected vibrations caused by local failure at the ice-structure interface. The local failure had characteristics of both shear failure and crushing failure and occurred at low ice-structure interaction speeds during tests. Local failure-induced vibrations were significant in the dynamic test with an ice-drift speed of 5 mm s^-1, however they also contributed to the dynamic response of the structure at higher ice-drift speeds. Bending failure-induced vibrations occurred at critical ice-drift speeds (30 mm s^-1 to 40 mm s^-1 and 70 mm s^-1 to 100 mm s^-1) where the bending failure frequency matched the 1st or 2nd natural frequency of the structure model. The results show that ice-induced vibrations on conical structures occur at various ice-drift velocities for both previously known and unexpected ice failure modes. Furthermore, the results provide new insight into conducting ice basin tests on ice-structure interaction with compliant conical structures.

Offshore substation platforms connect the array cable system of an offshore wind farm to the export cables and are often designed based on the jacket support structure concept with almost vertical legs. The size of these platforms, and the number of cables arriving at the platform through j-tubes, make that these have many structural elements crossing the waterline. For design of such multi-leg structures to ice loading, it is important to account for sheltering and interference effects as well as potential jamming of ice between closely spaced members. Guidance on these topics can be found in design standards; however, it mostly concerns four-legged structures with equal leg diameters for which experience has been obtained in full-scale and model-scale. In this paper we present results from a pre-study for a recent offshore substation design. A preliminary method for defining the sheltering and interference factors for multi-member structures with more than four vertical members and members of different diameters crossing the waterline is presented. The method is based on the original work on this topic by Saeki. The sensitivity of the global ice load on the platform support structure to the placement of cable j-tubes is investigated with the proposed method. The results are discussed in relation to design of substation support structures with a focus on dynamic interaction between ice and the platform, the potential benefit of lay-out optimization and extending the approach to include jamming and ice ridges interaction. This study highlights the need for further model-scale or full-scale testing to validate key assumptions required to develop these kinds of approaches for dealing with sheltering and interference on multi-member structures.

Sea ice poses significant challenges to human activities in cold regions. These activities include, for example, winter navigation and offshore wind energy developments. Designing vessels and structures to withstand loads caused by sea ice requires a deep understanding of the mechanical behavior of sea ice. Ice engineering and ice mechanics provide the understanding that enables the development of safer and more efficient structures for operations in icy environments. This chapter introduces key topics in ice engineering, focusing on the engineering properties of sea ice and the mechanics of ice failure processes during ice interactions with structures. Various types of ice failure processes, each often associated with specific types of offshore structures, are described in detail. The chapter also describes how experimental research is conducted at both full and laboratory scales. In addition, the chapter highlights typical modeling techniques used in ice engineering simulations and summarizes essential features of ice engineering simulation tools. The chapter concludes with a discussion on future directions for ice engineering research, emphasizing its links to geophysical-scale sea ice dynamics. From the aspect of future sea ice cover and its behavior, one of the strengths of ice engineering is that it relies on ice properties, which can be measured. This allows for accounting for the effects of climate change on ice cover reliably.

A modeling approach to simulate ice-induced vibrations of vertically sided offshore structures in ice tank experiments is presented. The technique combines replica modeling with the preservation of kinematics during ice-structure interaction. The technique was chosen based on the theoretical understanding that ice-induced vibrations are caused by an energy exchange between the structure and the ice. The mechanism is controlled by primarily four aspects: the kinematics during ice-structure interaction, the degree to which the ice can resist higher loading at low velocities prior to failure (velocity effect), the existence of a transition speed from ductile-to-brittle failure, and the mean ice load level. A model ice type which resulted in a velocity effect and provided a transition speed comparable to that of sea ice was developed and used during ice tank experiments. A scaling factor, derived from the comparison between the mean brittle crushing ice load of the full-scale event and the in-situ measured mean brittle crushing model ice load, was applied to scale structure properties of a numerical model. This model was implemented during real-time hybrid simulations in model ice to preserve kinematics during the ice-structure interaction. To verify the proposed scaling approach, rigid indenter experiments covering velocities from 0.1 mm s⁻¹ to 500 mm s⁻¹ and dynamic ice-induced vibration experiments of structures with varying aspect ratios (8 and 12) and shapes (cylindrical and rectangular) were conducted. Neither the aspect ratio nor shape appeared to influence the development of ice-induced vibrations significantly. The approach was qualitatively validated by reproducing full-scale ice-induced vibrations as experienced by the Molikpaq platform and Norströmsgrund lighthouse.

The design of flexible vertical offshore structures exposed to crushing ice, such as offshore wind turbines, can become governed by ice loads and the structural response associated with low relative speeds between ice and structure. Low ice speeds can cause significant loads due to pressure synchronization and/or increase in contact, potentially larger than those observed at high ice speeds, which is often referred to as the velocity effect. In this study, the dataset from the full-scale measurement campaign at the Norströmsgrund lighthouse is reanalyzed. Several instances of ice load amplification are identified and presented, to confirm that synchronization and the velocity effect developed. The increase in ice load is quantified and discussed in the context of a theoretical framework, and model- and full-scale observations of the velocity effect on other structures. Then several events of high-speed crushing are investigated and the potential global pressures at low speeds for those events are estimated based on the theoretical framework. These estimates are compared to typical high-speed global crushing pressures used to define the ice strength coefficient CR for the Baltic Sea. It is found that the velocity effect may produce global pressures equivalent to a CR factor above 0.9 MPa. The results provide a theoretical substantiation for inclusion of the velocity effect and a possible physical interpretation of the recommended value of 1.8 MPa in the ISO 19906 design standard.

A field campaign in the Vallunden lagoon in the Van Mijenfjorden on Spitsbergen was conducted to gather data on sea ice restoration by artificial flooding. Sea ice thickening was initiated by pumping sea water from below the first-year sea ice onto the surface without removing the covering snow layer. Part of the data was collected by four thermistor strings, two radiation sensors, and one anemometer. All measurement systems were left in the field until recovery of the floating systems in summer. Data provided by the measurement devices were received remotely to gather data before, during, and after the flooding phase (including the melting for as long as the sensors were sending data). Furthermore, coring systems were used to extract 88 ice cores for analysis of temperature, density and bulk salinity profiles along the full length of the ice cores before, during and within four days after flooding. The data set can be used to investigate physical processes involved in the ice growth before, during and after flooding. The data can be used to understand the development, growth and melting of snow ice. The radiation data can be used to analyze the (reflected) radiation of the initial, flooded and melting ice. Data gathered during the melting can be used to investigate the melting of thickened sea ice with different initial conditions prior to the onset of melting. Data on bulk salinity can be used to investigate short-term salt migration. Combing the different insights, growth- and melting models of sea ice including snow and snow ice can be validated. The understanding of melt-water drainage events could be improved and flow models for simulation of artificial flooding of snow-covered first-year sea ice could be further developed using the data.

The frozen-in scenario-a condition where the offshore wind farm is fully enveloped by a large ice cover-is not typically considered during design. The current study explores this scenario by including a sufficiently large surrounding ice sheet, modelled as a representative linear elastic spring at mean sea level, in a dynamic model of an offshore wind turbine. The effects of the presence of ice on natural frequencies and flexibility of the offshore wind turbine is investigated, as well as its effect on load effects in typical wind-dominated design load cases. Emphasis is placed on cases governing the design of structures above waterline, such as extreme coherent gusts and directional changes. By varying the spring stiffness representing the ice, the load, deformation, and strain rate the modelled ice was subject to, were determined. The study found that the extreme overturning moment and damage equivalent moment reduce when the offshore wind foundations are surrounded by ice, whereas the shear increases from MSL and below. The combined load effects from the frozen-in load case show a higher utilization for a few select elevations below MSL. Depending on the assumed relationship between ice thickness and stiffness, the study evaluates the conditions under which the ice sheet could potentially grow and remain intact during both power production and extreme events. These findings indicate that based on the current methodology, the frozen-in load case cannot be disregarded and should be included in design in regions where there is an increased risk of encountering these conditions. However, it is expected that with improved ice modelling, accounting for viscoelastic behavior and ice failure, utilization levels would not exceed those observed in ice-free conditions.

In this paper, we focus on investigating ship activities in the United States’ Arctic waters and developing new viscoelastic materials that can mimic specific ice behavior. This is a significant challenge, and we discuss potential positive outcomes and how the acquired knowledge can contribute to understanding ice behavior in Arctic and Sub-Arctic regions. We first define ice and ship statistics, providing a foundational understanding of potential ice–ship interactions. We then describe the development of thought experiments for wave–ice interactions and the creation of a numerical environment for modeling purposes. This step is crucial for simulating various scenarios related to ice and wave dynamics, ultimately contributing to the design of ships capable of navigating safely in diverse Arctic conditions. Finally, stakeholder and community engagement is addressed, recognizing the importance of involving local perspectives and insights to ensure practical, socially responsible, and effective solutions.

Baltic Sea offshore wind development has seen a rapid growth in the past decade with major projects developed and constructed in the Southern Baltic Sea and attention now slowly turning to the more challenging Northern Baltic Sea areas. With respect to sea ice engineering, the focus the past years has been on determination of global loads on the support structures, in particular development of ice-induced vibrations has received much attention. In this paper specific sea ice engineering questions encountered in discussions with designers of offshore wind support structures between 2018 and 2023 are presented. The focus is on questions which do not seem to have a straightforward answer yet. These relate to the completeness of the load case table, interpretation of the ice strength coefficient CR, jamming and sheltering effects for multi-legged structures, design of appurtenances for ice loading, ridge loads, and sea ice dynamics in the presence of wind farms.

The study investigated the use of a Hardware-in-the-Loop (HiL) technique applied in model ice experiments to enable the analysis of offshore structures with low natural frequencies under dynamic ice loading. Traditional approaches were limited by facility capacities and ineffective downscaling of the geometry of the offshore structures. The goal of the present study was to overcome these challenges and to enhance the understanding and explore the applicability of a hybrid testing technique in model ice experiments. To achieve the objective, 204 Hardware-in-the-Loop simulations in model Ice (HiLI) were analyzed. Results showed robust behavior and good performance of the HiLI due to minimal variation in measured delay, normalized root mean square error, and peak tracking error and low magnitudes of such parameters despite alterations in factors such as the choice of the numerical structural model, physical prototype, measurement system, and ice type. Notably, the performance of the HiLI was affected when testing with warm model ice or scaling for harsh ice conditions, attributed to a reduced signal-to-noise ratio and instability of the system, respectively. Experimental identification of the critical delay, along with the application of an analytical stability criterion, revealed that the instability observed, was likely induced by reducing the structural stiffness of the numerical structural model to fulfil the scaling requirements when testing for harsh ice conditions. Additionally, the study showed improved HiLI performance when the physical prototype was in contact with the model ice. This observation was further analyzed and is assumed to be caused by the coupling between the ice and physical prototype, causing a coupled and thus increased eigenfrequency of the physical prototype-ice system.

Cyclic crushing experiments with a haversine velocity waveform were performed on passively confined, freshwater columnar ice specimens for a variety of velocities and frequencies. The aim of the experiments was to study the ice deformation and failure behavior in crushing when loaded at a predefined displacement pattern closely resembling the frequency lock-in regime of ice-induced vibrations. The focus of the experiments was on the development of load and ice deformation behavior at the grain and ice specimen scales during each cycle. To this end, the deformation and failure of the ice were observed with crossed-polarized light to highlight the microstructure in-situ during cyclic crushing. It was shown that there are dichotomous mechanical behaviors of the damaged and confined ice during a single crushing cycle: brittle at high velocity and non-brittle at low velocity. At low velocity, ice fracture was interrupted and stress relaxation occurred until the predefined velocity began increasing in the cycle. The stress relaxation in the load was accompanied by stress-optic effects in the ice. It was found that a load peak-velocity hysteresis developed in each crushing cycle: peak loads following the non-brittle behavior were temporarily higher than the peak loads of the brittle behavior. The temporary load peak enhancement tended to increase with increasing duration of stress relaxation, i.e. the peak enhancement tended to increase with decreasing velocity and frequency. Negligible peak enhancement and stress relaxation duration were observed for the highest frequency and mean velocity tested of 2 Hz and 10 mm s⁻¹, respectively. For tests with a minimum velocity of 1 mm s⁻¹, no stress relaxation was observed in the load measurement. Preliminary results from deviating from the haversine velocity waveform by increasing the minimum velocity showed that the stress relaxation duration decreases, but the non-brittle peak load does not decrease. It is speculated that ice anelastic ice behavior could account for the rapid stress relaxation at low velocity. It is unclear what causes the hysteresis, although it is speculated that dynamic strain aging might play a role. The change in ice behavior during the experiments demonstrates a mechanism which develops rapidly and might therefore incite the development of the frequency lock-in regime of ice-induced vibrations of vertically-sided structures.

Increased activity in planning offshore wind farms in the northern Baltic Sea has renewed interest in studying the effect of ice cones on ice failure mechanisms. In preparation for future experiments with steep ice cones, preliminary ice basin experiments were performed at the Aalto Ice and Wave Tank to investigate how model ice fails against a 3D-printed cylindrical and a conical structure representative of wind turbine foundations. The main motivation behind the two structures is to test ice loads on a monopile foundation and a monopile foundation fitted with an upward-bending ice cone. Each structure was tested at eight different velocities in three ice sheets with varying mechanical properties, including a newly developed, crushing-optimized model ice. The force exerted by the ice on these rigid structures was measured using a six-axis load cell. The results show that ice undergoes mixed-mode failure on the cone in the form of bending, crushing, and spalling, when tested in crushing-optimized ice. Based on the observations and results, it is recommended that model-scale experiments, focused on mixed-mode ice failure, use model ice with a representative compressive to flexural strength ratio, scaled flexural and compressive strength, and the ability to fail in brittle crushing. If these criteria cannot be met, it may be possible to combine test results from different ice sheets, each focused on one ice failure mechanism. Additionally, this study successfully used 3D-printed structures, which present a new and more accessible method of preparing scale models.

EU urgently needs to increase the development of secure and green energy, and this includes renewables such as Offshore wind energy. An expansion of Offshore wind will include the Baltic where sea ice is one of the major uncertainties. To ensure that the wind turbines are safe for people and the environment, while keeping them economically competitive betterguidelines and regulations should be developedcollaboratively by European industry and academia. There are unsolved challenges with respect to ice action on structures for offshore wind. However, in the current draft for Horizon Europe WorkProgramme 2023-2024 on Climate, Energy and Mobility1, the challenges related to sea ice with regards toOffshore wind energy are not mentioned. In order to meet the crucial green energy goals, it is our statement that it is imperative to include sea ice in the final version.

The effect of misalignment between wind- and ice loading direction on the development of ice-induced vibrations of offshore wind turbines has been investigated experimentally. In the experiments a hybrid test setup was used to study the structural response to combined loading from physical model ice and numerically applied wind. The motivation for this study was the high uncertainty in the design of offshore wind turbine support structures in cold regions, caused by scarcity of full-scale and model-scale data on ice-structure interaction. Test results revealed that misaligned scenarios result in the development of sustained ice-induced vibrations in the ice load direction. The test results also showed that ice-induced vibrations can develop up to higher ice drift speeds for misaligned scenarios than for aligned scenarios. Both observations are considered to be related to low total damping in the ice drift direction for a misaligned scenario. Further comparison between a 90°-misaligned operational and an aligned idling scenario revealed that wind-induced structural displacements perpendicular to the ice drift direction do not cause the ice to fail. On the contrary, it was shown that the ice constrains the wind-induced motion for low relative velocities between ice and structure. For high relative velocities, wind-induced displacements approach those in open water as the ice fails in rapid succession at the sides of the structure during crushing. The analysis of a misaligned scenario with a smaller misalignment angle revealed that vibrations occur perpendicular to the ice drift direction and are characterized by relatively low amplitude and high frequency. The ice, being in contact with the structure, neither prevented those vibrations nor failed.

The manual application of universal (Rigsby) stage techniques is commonly used to determine the fabric of thin sections of ice viewed with crossed-polarized light. This process can require hours of focus in cold conditions to identify the c-axis of each grain in a thin section. Automated ice texture and fabric methods of several forms exist but are rarely implemented beyond the field of glaciology. The present study introduces a method based on the theory of interference coloration for automated ice texture and quarter fabric analysis by using in-plane conventional photography of an ice thin section as input. The method is compatible with universal stages and polariscopes, and is not restricted by the planar-face dimensions of the thin section, allowing for thin section analysis of any size when sufficient digital camera resolution is available. Light source color temperature and chromatic adaptation are considered in the interference coloration theory, and ice fabrics are simulated for reference in identifying ice types. Sample thin section texture and quarter fabric analyses from freshwater lake and laboratory-grown ice are presented to demonstrate the applications of the method. The method is compared with the Rigsby stage technique, which yielded mean (standard deviation of) azimuth and inclination errors of 2.9 (1.0) and 11.5 (8.0) degrees, respectively, thereby demonstrating accuracy sufficient for quantifying quarter fabrics when considering a mean standard deviation in inclination of 5.4 degrees with the Rigsby stage technique.

The authors regret their errors in the production of the legend labels and marker colors in Fig. 15 on page 11. The correct legend labels and marker colors are provided in the figure below:[Formula presented] The authors would like to apologize for any inconvenience caused.

Climate change is affecting global weather patterns, but nowhere is this more apparent than in the Arctic. The Arctic is an extreme environment going through rapid climate change, resulting in the opening of new shipping lanes and leading to less multiyear ice formation. This increases the risk of collision with the sea ice making it difficult to make long term voyage plans based on sea ice predictions. The Automatic Identification System (AIS) provides important services for marine domain awareness. For safe and effective ship traffic management and the development of new artificial intelligence (AI) marine algorithms, precise AIS readings for hull size and type are typically required. In this paper, we provide a summary of ship activities as well as relevant ice information in Alaskan waters that may result in ice-ship interactions and discuss them. AIS ship data was used to determine the ship speed distribution in different areas in the Alaskan waters. Ship movement in ice infested regions was compared with sea ice data from the Copernicus Reanalysis Products and sea ice thickness was estimated using empirical equations to identify potential ship-sea ice interactions. Data from 2015 to 2020 was analyzed to determine if there is an increase in maritime activity that can be linked to a decline in sea ice extent in Alaskan waters. The AIS data was also sorted by ship hull types to see how the different sectors of the Alaskan maritime industry are changing over time in ice-covered areas.