Ice Ridges Research Articles

Onboard multivariate hazard assessment for UIKKU chemical tanker by Gaidai reliability method

The current study outlines a novel multimodal structural reliability methodology, suitable for naval dynamic systems, that are either numerically simulated, or directly physically measured. Cross-correlations between the system's principal/key dimensions/components, along with the high dimensionality of complex naval dynamic systems, are not easily addressed by existing reliability methods, that are mostly univariate or bivariate. The objective of this study had been to apply a novel reliability/hazard assessment methodology to UIKKU chemical tanker onboard dynamic measurements to demonstrate the efficiency of the proposed multimodal structural reliability methodology. Current investigation utilized onboard measured ice loadings, exerted on the UIKKU tanker hull and propulsion devices during its Arctic voyage. Onboard dynamic data recordings then were interpreted to gain knowledge about dynamic load levels. The hull of UIKKU had been instrumented so that ice-induced loads/stresses on vessel shell plating had been monitored at various key locations, both in longitudinal as well as in vertical directions, along the vessel’s hull. Longitudinal bending stresses at several locations on the vessel hull and vessel vertical accelerations had been measured to analyze global vessel behaviour when colliding e.g., moderately heavy ice ridges. In addition to UIKKU onboard measurements onboard, Russian partners had instrumented icebreaker vessel Capitan Dranitsyn to real-time measure strains/stresses within ice belt grillage, located at the vessel’s bow. Icebreaker vessel Capitan Dranitsyn acted as escort icebreaker during the whole Arctic voyage. Obtained results may be utilized to harmonize IACS Polar ship rules. In the current study, the onboard measuring system along with measured results, during the whole voyage have been briefly represented.

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.

Effects of the gap ratio on the flow field structures and the aerodynamic performance of an airfoil with ridge ice

Under SLD icing conditions, the ridge ice may appear on the surface of aircraft, which led to the significant aerodynamic deterioration and affected aircraft flight safety. The present study experimentally investigated the effects of the gap ratio on the flow field structures and aerodynamic performance of an airfoil with ridge ice. Detailed measurements were performed in a low-speed reflux wind tunnel by utilizing the Particle Image Velocimetry (PIV) technique and a high-sensitivity six-component balance. The results showed that the maximum lift coefficient, stall angle, and maximum pitch moment coefficient of the airfoil increased as the gap ratio enlarged. At AOA = 10 deg, the separation bubble length decreased by 77 % when the gap ratio changed from 0 to 0.1. Meanwhile, the separation bubble length decreased by 68 % when the gap ratio changed from 0.1 to 0.3. Besides, as the increase of the gap ratio, the average vorticity, turbulent kinetic energy, and Reynolds shear stress in the selected region above the airfoil decreased, while the average velocity increased. In addition, the gap ratio did not have an apparent effect on the transition onset positions and the maximum spanwise vorticity in the flow field.

A large-scale high-resolution numerical model for sea-ice fragmentation dynamics

Abstract. Forecasts of sea-ice motion and fragmentation are of vital importance for all human interactions with sea ice, ranging from those involving indigenous hunters to shipping in polar regions. Sea-ice models are also important for simulating long-term changes in a warming climate. Here, we apply the Helsinki Discrete Element Model (HiDEM), originally developed for glacier calving, to sea-ice breakup and dynamics. The code is highly optimized to utilize high-end supercomputers to achieve an extreme time and space resolution. Simulated fracture patterns and ice motion are compared with satellite images of the Kvarken region of the Baltic Sea from March 2018. A second application of HiDEM involves ice ridge formation in the Gulf of Riga. With a few tens of graphics processing units (GPUs), the code is capable of reproducing observed ice patterns that in nature may take a few days to form; this is done over an area of ∼100km×100km, with an 8 m resolution, in computations lasting ∼10 h. The simulations largely reproduce observed fracture patterns, ice motion, fast-ice regions, floe size distributions, and ridge patterns. The similarities and differences between observed and computed ice dynamics and their relation to initial conditions, boundary conditions, and applied driving forces are discussed in detail. The results reported here indicate that the HiDEM has the potential to be developed into a detailed high-resolution model for sea-ice dynamics at short timescales, which, when combined with large-scale and long-term continuum models, may form an efficient framework for forecasts of sea-ice dynamics.

Transformation of internal solitary waves at the edge of ice cover

Abstract. Internal wave-driven mixing is an important factor in the balance of heat and salt fluxes in the polar regions of the ocean. Transformation of internal waves at the edge of the ice cover can enhance the mixing and melting of ice in the Arctic Ocean and Antarctica. In the polar oceans, internal solitary waves (ISWs) are generated by various sources, including tidal currents over bottom topography, the interaction of ice keels with tides, time-varying winds, vortices, and lee waves. In this study, a numerical investigation of the transformation of ISWs propagating from open water in the stratified sea under the edge of the ice cover is carried out to compare the depression ISW transformation and loss of energy on smooth ice surfaces, including those on the ice shelf and glacier outlets, with the processes beneath the ridged underside of the ice. They were carried out using a non-hydrostatic model that is based on the Reynolds-averaged Navier–Stokes equations in the Boussinesq approximation for a continuously stratified fluid. The Smagorinsky turbulence model extended for stratified fluid was used to describe the small-scale turbulent mixing explicitly. Two series of numerical experiments were carried out in an idealized 2D setup. The first series aimed to study the processes of the ISWs of depression transformation under an ice cover of constant submerged ice thickness. Energy loss was estimated based on a budget of depth-integrated pseudoenergy before and after the wave transformation. The transformation of ISWs of depressions is controlled by the blocking parameter β, which is the ratio of the minimum thickness of the upper layer under the ice cover to the incident wave amplitude. The energy loss was relatively small for large positive and large negative values of β. The maximal value of energy loss was about 38 %, and it was reached at β≈0 for ISWs. In the second series of experiments, a number of keels were located on the underside of the constant-thickness ice layer. The ISW transformation under ridged ice also depends on the blocking parameter β. For large keels (β<0), more than 40 % of energy is lost on the first keel, while for relatively small keels (β>0.3), the losses on the first keel are less than 6 %. Energy losses due to all keels depend on the distance between them, which is characterized by the parameter μ, i.e. the ratio of keel depth to the distance between keels. In turn, for a finite length of the ice layer, the distance between keels depends on the keel quantity.

A Framework for Structural Analysis of Icebreakers during Ramming of First-Year Ice Ridges

This paper presents a framework for structural analysis of icebreakers during ramming of first-year ice ridges. The framework links the ice-ridge load and the structural analysis based on the physical characteristics of ship–ice-ridge interactions. A ship–ice-ridge interaction study was conducted to demonstrate the feasibility of the proposed framework. A PC-2 icebreaker was chosen for the ship–ice interaction study, and the geometrical and physical properties of the ice ridge were determined based on empirical data. The ice ridge was modeled by solid elements equipped with the continuous surface cap model (CSCM). To validate the approach, the simulated ice resistance was computed using the Lindqvist solution and in situ tests of R/V Xuelong 2. First, the local ice-induced pressure on the hull shell was determined based on numerical simulations. Subsequently, the local ice pressure was applied to local deformable sub-structural models of the PC-2 icebreaker hull by means of triangular impulse loads. Finally, the structural response of sub-structural models with refined meshes was computed. This case study demonstrates that the proposed framework is suitable for structural analysis of ice-induced stresses in local hull components. The results show that the ice load and the structural response obtained based on the four first-year ice-ridge models show obvious differences. Furthermore, the ice load and corresponding structural response increases with the width of the ridge and with increasing ship speed.

Iapetus Equatorial Ridge: The Understanding from The Quran and The Hadith

This research studies the statement about the splitting of the Moon into two as narrated by Quran & Hadith in accordance to scientific studies related to the subject. The author suggests that current scientific findings of the formation of the equatorial ridge on Iapetus differs from the Islamic classical scholars’ opinions are not in tandem regarding the splitting and fusing of the moon. This research also applies the methodology of hadith from the writings given from various narrations and hadith literature. The application of document analysis methodology is applied to current concepts by the geologists and astrophysicists on the formation of the equatorial ridge of Iapetus and the ice ridge in Antarctica. The findings establishes that the Iapetus equatorial ridge is a genuine existence that occurred, which split into two and fused back. This image was captured by the satellite sent to Saturn.

Numerical investigation of the influences of ridge ice parameters on lift and drag coefficients of airfoils through design of experiments

The complexity of ice accretion shapes on aircraft brings challenges in establishing the physical correlations between the geometric parameters of ice and the aerodynamic performances of an airfoil. The present study applied a quarter-circle simplified ridge ice model and designed four parameters, including the lower ice horn, the height of the upper ice horn, the angle of the upper ice horn, and the location of the upper ice horn. Design of Experiments (DOE) was adopted to design the simulation process and analyze the obtained data. Numerical investigations were carried out to study the effects of these four design parameters on the lift coefficients ( CL) and drag coefficients ( CD) of three airfoils at various angles of attack. The results revealed that the four design parameters had influences on CL and CD in all simulation cases. The influence of the height of the upper ice horn was always dominant, followed by the angle and location of the upper ice horn. The influence degrees of the lower ice horn varied with the angles of attack and airfoils. The change trends of CL and CD were opposite while changing the value of any parameter in most simulation cases. In addition, the leading-edge radii of these three airfoils, as well as the shapes of the upper and lower surfaces, could alter the influences of design parameters on CL and CD.

A peek beneath the surface of Arctic sea ice

Sea ice ridges account for a large proportion of the overall Arctic sea ice volume, yet more attention in research has historically been focused on the thinner level ice. We spoke to Dr Mats Granskog and Dr Oliver Müller about their work in analysing samples from sea ice ridges collected during the MOSAiC polar expedition, with the aim of gaining deeper insights into their role.

Ice ridge evolution: Investigation in-situ and computer simulations

The article presents a two-dimensional three-layer non-stationary thermodynamic model allowing to calculate the annual variation (thermodynamic evolution) of the ice ridge using external meteorological and hydrological parameters as well as the information on the initial ice ridge porosity. For the test model simulation, the results of the study of morphometric characteristics of the ice ridge carried out in May-June 2011 and in April 2012 at « North Pole −38» and «North Pole −39» drifting stations were used. These studies were conducted using electric thermal drilling with computer recording of the penetration rate. Boreholes were drilled along the cross-section of the ridge crest at 0.5 m intervals. Cross-sectional profiles of ice ridge are illustrated. Applying the proposed model, it was possible to adequately reproduce the observed evolutionary changes in the main morphometric parameters (sail height, keel depth, thickness of the consolidated layer) of the investigated ice ridge.

Analysis of Ship Motion in An Ice Ridge Field Based on Empirical Approach

Analysis of Ship Motion in An Ice Ridge Field Based on Empirical Approach

Observations of preferential summer melt of Arctic sea-ice ridge keels from repeated multibeam sonar surveys

Abstract. Sea-ice ridges constitute a large fraction of the total Arctic sea-ice area (up to 40 %–50 %); nevertheless, they are the least studied part of the ice pack. Here we investigate sea-ice melt rates using rare, repeated underwater multibeam sonar surveys that cover a period of 1 month during the advanced stage of sea-ice melt. Bottom melt increases with ice draft for first- and second-year level ice and a first-year ice ridge, with an average of 0.46, 0.55, and 0.95 m of total snow and ice melt in the observation period, respectively. On average, the studied ridge had a 4.6 m keel bottom draft, was 42 m wide, and had 4 % macroporosity. While bottom melt rates of ridge keel were 3.8 times higher than first-year level ice, surface melt rates were almost identical but responsible for 40 % of ridge draft decrease. Average cross-sectional keel melt ranged from 0.2 to 2.6 m, with a maximum point ice loss of 6 m, showcasing its large spatial variability. We attribute 57 % of the ridge total (surface and bottom) melt variability to keel draft (36 %), slope (32 %), and width (27 %), with higher melt for ridges with a larger draft, a steeper slope, and a smaller width. The melt rate of the ridge keel flanks was proportional to the draft, with increased keel melt within 10 m of its bottom corners and the melt rates between these corners comparable to the melt rates of level ice.

Consolidated layer thickness in probabilistic simulation of first-year ice ridges

This research study focuses on resolving the issue of sparse data and information required for the probabilistic assessment of ice ridge loads in offshore structures in Arctic regions. The study introduces the consolidated layer thickness into the simulation of ice ridge loads. Through the analysis of seasonal development of level ice draft, ridge keel draft, and ridge frequency, conclusions were drawn on the timing of ridge creation. The data used for this analysis was obtained from ice profiling sonars located in the Beaufort Sea. An analytical approach was established to estimate the probability density function of ridge formation timing, which was then used to simulate ridge age, determine an analytical formulation for consolidated layer growth, and investigate its thickness properties. The study found a negative correlation between consolidated layer thickness and ridge keel draft, which contradicts the previously held assumption in the literature that these variables are not related. This research establishes a framework for probabilistic simulation of ice ridge systems characterized by certain parameters, such as ridge keel draft, level ice draft, ridge frequency, and consolidated layer thickness, which facilitates maintaining the correlations between the parameters in the simulation.

Deformation lines in Arctic sea ice: intersection angle distribution and mechanical properties

Abstract. Despite its relevance for the Arctic climate and ecosystem, modeling sea-ice deformation, i.e., the opening, shearing, and ridging of sea ice, along linear kinematic features (LKFs) remains challenging, as the mechanical properties of sea ice are not yet fully understood. The intersection angles between LKFs provide valuable information on the internal mechanical properties, as they are linked to them. Currently, the LKFs emerging from sea-ice rheological models do not reproduce the observed LKF intersection angles, pointing to a gap in the model physics. We aim to obtain an intersection angle distribution (IAD) from observational data to serve as a reference for high-resolution sea-ice models and to infer the mechanical properties of the sea-ice cover. We use the sea-ice vorticity to discriminate between acute and obtuse LKF intersection angles within two sea-ice deformation datasets: the RADARSAT Geophysical Processor System (RGPS) and a new dataset from the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) drift experiment. Acute angles dominate the IAD, with single peaks at 48∘±2 and 45∘±7. The IAD agrees well between both datasets, despite the difference in scale, time period, and geographical location. The divergence and shear rates of the LKFs also have the same distribution. The dilatancy angle (the ratio of shear and divergence) is not correlated with the intersection angle. Using the IAD, we infer two important mechanical properties of the sea ice: we found an internal angle of friction in sea ice of μI=0.66±0.02 and μI=0.75±0.05. The shape of the yield curve or the plastic potential derived from the observed IAD resembles a teardrop or a Mohr–Coulomb shape. With these new insights, sea-ice rheologies used in models can be adapted or redesigned to improve the representation of sea-ice deformation.

THE ROLE OF SUFFOSION IN THE FORMATION OF ENGINEERING GEOLOGICAL CONDITIONS IN THE TERRITORY OF BELARUS

The article presents the results of a comprehensive study of the conditions for the development and spread of natural and technogenic suffusion by the Belarus territory. It is noted that in insignificantly disturbed natural geoenvironment, the most favorable conditions for the development of suffusion have developed within the moraine and water-glacial plains and lowlands of the eastern part of the country, as well as marginal ice ridges and uplands with a cover of loess and loess-like formations with increased silt content, relatively low density of the soil skeleton, easy soakability and thixotropy, which contribute to the intensive development of the suffusion process. Active natural factors, conditions for the development and spread of suffusion, as well as forms of its manifestation in loess and loess-like soil massifs are considered. Suffusion manifestation in technogenically disturbed geoenvironment is analyzed, and its negative impact on functioning of natural-anthropogenic systems of various organization levels is shown by specific examples. In the authors’ opinion, the creation of a monitoring system for the development of suffusion, as well as other exogenous geological and engineering geological processes, will provide up-to-date information on the distribution and manifestation activity of these processes and the factors that determine them.

Snowmelt contribution to Arctic first-year ice ridge mass balance and rapid consolidation during summer melt

Sea ice ridges are one of the most under-sampled and poorly understood components of the Arctic sea ice system. Yet, ridges play a crucial role in the sea ice mass balance and have been identified as ecological hotspots for ice-associated flora and fauna in the Arctic. To better understand the mass balance of sea ice ridges, we drilled and sampled two different first-year ice (FYI) ridges in June–July 2020 during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC). Ice cores were cut into 5 cm sections, melted, then analyzed for salinity and oxygen (δ18O) isotope composition. Combined with isotope data of snow samples, we used a mixing model to quantify the contribution of snow to the consolidated sea ice ridge mass. Our results demonstrate that snow meltwater is important for summer consolidation and overall ice mass balance of FYI ridges during the melt season, representing 6%–11% of total ridged ice mass or an ice thickness equivalent of 0.37–0.53 m. These findings demonstrate that snowmelt contributes to consolidation of FYI ridges and is a mechanism resulting in a relative increase of sea ice volume in summer. This mechanism can also affect the mechanical strength and survivability of ridges, but also contribute to reduction of the habitable space and light levels within FYI ridges. We proposed a combination of two pathways for the transport of snow meltwater and incorporation into ridge keels: percolation downward through the ridge and/or lateral transport from the under-ice meltwater layer. Whether only one pathway or a combination of both pathways is most likely remains unclear based on our observations, warranting further research on ridge morphology.

Sea Ice Elevation Measurements Using 3-D Laser Scanner

This study aims to introduce a sea ice elevation dataset estimated by using a 3-D laser scanner during the ice camp of the 2022 Arctic summer field survey. The equipment used is FARO’s Laser scanner FOCUS 3D X 130 HDR. The observed sea ice floe is located in the Arctic Ocean (76°13' N, 174°35') and is a multi-year ice with several melt ponds and ice ridges. We scanned eight sections separately, considering the equipment’s maximum horizontal scan range and the ice surface’s topographic features. The raw data were co-registered based on the positions of reference spheres. The result indicated a significant level of accuracy with a target-based vertical mean error of 4.8 mm. The laser scanner data were merged into point clouds ranging from 160×210 m. As a result, sea ice elevation data were generated in 0 to 2.8 m based on the minimum vertical point in the observation range. Sea ice elevation data is an essential variable in estimating the various properties of sea ice, such as ice thickness and roughness. In addition, using climatic variables such as air temperature and energy budget observed simultaneously can help to understand the physical interaction between the sea ice surface and the atmosphere on a local scale.

Experimental investigation on the tensile strength of freshwater freeze-bonds

The strength of the freeze-bonds between ice blocks has been found to significantly affect the strength and failure mechanism of ice rubble and ice ridges. Limited information on the tensile strength of freeze-bonds is presently available. A new testing apparatus and method has been developed to study the tensile strength of freeze-bonds under submerged, confined conditions as expected in natural ice ridges and rubble. A total of 30 experiments have been carried out to study the effect of normal confinement pressure and submersion time on the tensile strength of freshwater freeze-bonds. The confinement pressures ranged from 25 kPa to 100 kPa and freeze-bonds formed in 5 min to 3 h of submersion. The strength of freeze-bonds has been found to increase with the increase of the confinement pressure. The development of the tensile strength of freeze-bonds by submersion time was found to be similar to the development of the freeze-bond shear strength. Empirical equations for estimation of the freeze-bond strength as a function of confinement pressure is presented.

Laboratory experimental dataset for the study of the sheltering effect between ice ridges

Laboratory experimental dataset for the study of the sheltering effect between ice ridges

Analysis of the relationship between level ice draft, ridge frequency and ridge keel draft for use in the probabilistic assessment of ice ridge loads on offshore structures

Level ice draft, ice ridge keel draft and ridge frequency are important variables in the probabilistic assessment of ice ridge loads on offshore structures. We use ice profiling sonar (IPS) measurements of ice draft from the Beaufort Sea to analyse the relationship between these three variables. We propose a probabilistic simulation technique of ridge keel drafts. Two examples of simulations are given. The first example simulates the weekly deepest ridges. The simulated distribution of the weekly deepest ridge keel draft agrees with the measured data. The second example simulates all ridges deeper than 5 m. This simulation results in overestimation of the ridge keel draft in the tail section of the distribution. For both simulations, with the relationships established in this paper, the only needed input is level ice draft. Future studies should investigate whether the relationships found in the Beaufort Sea are valid in other areas or if there is a possibility of scaling the correlations. If the correlations prove predictably scalable for other locations, it could be possible to estimate the ridge keel draft distribution and ridge frequency by knowing only the level ice draft (thickness) statistics. This study is our first endeavour in this direction.