Ice Ridges Research Articles

Mechanism of generation and development of thermal ice ridges

Mechanism of generation and development of thermal ice ridges

Calculation of the destruction of ice structures by the grid-characteristic method on structured grids

Sea ice is a difficult object to study due to its heterogeneous structure and location near the melting point. This paper proposes a model of ice ridges as a heterogeneous structure with multiple water and air inclusions, free boundaries and free sliding contact boundaries. The dynamic growth of cracks in a given heterogeneous structure under intense dynamic influences is considered, which makes the considered boundary value problem nonlinear. The influence of explosion parameters (location of sources, frequency, number of periods) on the nature of the destruction of the ice ridges was investigated. The work also investigates the collision of an ice island with ice floes. For calculations, the grid-characteristic method is used on structured rectangular computational grids.

О ПОРИСТОСТИ НЕКОНСОЛИДИРОВАННОЙ ЧАСТИ КИЛЯ ТОРОСОВ

The paper discusses the distribution of porosity of the unconsolidated part of the keel of ten first-year ice ridges investigated in the central Arctic basin and the Shokalsky Strait (Severnaya Zemlya) in 2012–2019. These studies were performed using thermal drilling with the computer (logger) recording of penetration rate. Boreholes were drilled along the cross-section of the ridge crest, mainly at 0.25-m intervals. The porosity values for the unconsolidated part of the keel are presented on the diagram as a point cloud. The horizontal position of the points is determined by the relative distance between the borehole and the point where the keel has the maximum draft. As moving away from this point, the average porosity of the unconsolidated part of the keel tends to increase. This feature is a consequence of the Archimedes force effect and agrees with the model of porosity changes from the theory of granular media.

Estimation of Ice Thickness and the Features of Subglacial Media Detected by Ground Penetrating Radar at the Baishui River Glacier No. 1 in Mt. Yulong, China

Using ground-penetrating radar (GPR), we measured and estimated the ice thickness of the Baishui River Glacier No. 1 of Yulong Snow Mountain. According to the position of the reflected media from the GPR image, combined with the radar waveform amplitude and polarity change information, the ice thickness and the changing medium position at the bottom of this temperate glacier were identified. Water paths were found in the measured ice, including ice caves and crevasses. A debris-rich ice layer was found at the bottom of the glacier, which produces strong abrasion and ploughing action at the bedrock surface. This results in the formation of different detrital layers stagnated at the ice-bedrock interface and numerous crevasses on the bedrock surface. Based on the obtained ice thickness and differential GPS data, combined with Landsat images, the kriging interpolation method was used to obtain grid data. The average ice thickness was 52.48 m and between 4740 and 4890 m above sea level, with a maximum depth of 92.83 m. The bedrock topography map of this area was drawn using digital elevation model from the Shuttle Radar Topography Mission. The central part of the glacier was characterized by small ice basins with distributed ice steps and ice ridges at the upper and lower parts.

Estimation of sea ice parameters using an assimilated sea ice model with a variable drag formulation

In this work, sea ice concentrations in the regions of Baffin Bay, Hudson Bay, the Labrador Sea and the Gulf of St. Lawrence were estimated using a standalone regional configuration of Los Alamos Sea ice Model, CICE. A sensitivity analysis of the mixed layer depth criteria that affects the predicted sea ice formation/ablation has been carried out to tune the model. Sea ice concentration from AMSR2 OSISAF, sea ice edge from SSMIS/ASCAT OSISAF, and sea surface temperature from OISST AVHRR-only products were then assimilated into the tuned model using a combined optimal interpolation method. Extending previous studies, which used a constant drag formulation in their assimilation schemes, we use a variable drag formulation to represent the friction associated with effective sea ice surface roughness at the ice–atmosphere and ice–ocean interfaces. The variable drag coefficient is estimated from properties of the sea ice cover such as the ice concentration, the vertical extent and area of the ridges, the freeboard, the floe draft, the size of floes and melt ponds. The new features of the assimilated model include tracers to estimate ridged ice, level ice, melt ponds, freeboard, sail height and keel depth. The estimates of ice concentration from the assimilated models are then compared with the ice concentration product from the Canadian Ice Service. The results show that the updates provided to the tracers through the assimilation of sea ice products are reasonable and the model estimates of ice concentration from the assimilated models are better than the non-assimilated model estimates. Finally, the estimates of updated sea ice parameters such as ridged ice area, volume and ice thickness are compared with the estimates from non-assimilated models and the literature to verify the results.

Medium-scale experiment in consolidation of an artificial sea ice ridge in Van Mijenfjorden, Svalbard

This study characterizes a consolidation of undeformed level ice and ice ridges. Field investigations were performed in the Van Mijenfjorden, Svalbard for 66 days between February and May of 2017. The thickness and properties of the level ice that was used to make the ridge were measured, and thermistor-strings were installed in the ridge and the neighboring level ice. The ridge was visited four times for drilling and sampling. During our field experiment, the level ice (LI) grew from 50 to 99 cm, the consolidated layer (CL) grew up to 120 cm, and the ridge initial macroporosity was about 0.36. The experimental results provided enough information for accurate growth prediction and validation of ridge consolidation models.Two analytical resistive models and two-dimensional discretized numerical models are presented. All models need general met-ocean conditions and general ice physical properties. The ridge model includes the effect of the inhomogeneous top and bottom surfaces of the consolidated layer. The models were validated against the field measurements, and the further details of the analytical models were validated against the numerical model.The analytical resistive ridge model with convective atmospheric flux captures the relevant phenomena well and could be used for prediction of the consolidated layer thickness in probabilistic analysis of ice actions on structures. The model including the radiative terms predicted heat fluxes in level ice and ridge better than the convective model but required more input data. Vertical temperature profiles through the consolidated layer and further into respectively a void and an ice block may result in significantly different estimations of the consolidated layer thickness. The difference between fresh and saline ice growth is becoming significant only during the warming phase due to significant change of sea ice microporosity.

Mechanics of oscillations and waves in the ice of the Аrctic ocean during compression and ridging

One of the main scientific and practical problems in the Arctic is the study of the dynamic state of the sea ice cover. The main parameters in the general model of drifting ice are the drift velocity vector, friction stress at the air-ice and ice-water interfaces, and the forces of dynamic interaction of ice fields. Establishing the connection between the large-scale processes in the atmosphere-ice-ocean system is necessary for developing methods of forecasting ice compression and ridging and the formation of local and extended fractures and leads, which help improve the existing climate models. The main aim is to obtain results of full-scale instrumental measurements of parameters of ice large-scale mechanics and dynamics, which provide a physical basis for explaining the nature of observed large-scale ice processes and allow one to perform physical parametrization. To accomplish this aim and evaluate the physicomechanical condition of the drifting ice cover of the Arctic Ocean, the “Transarktika-2019” expedition performed a real-time ice monitoring in April 2019. The investigation was conducted using seismometers and tiltmeters installed on the ice such that they formed a triangle with the sides measuring up to two kilometers. Data has been obtained on the wave and oscillation processes of crack formation, compression and ridging of ice. The possibilities of deciphering the initial data on the physics of wave and oscillatory processes in the icewater system considerably increase when using the known methods of processing seismic signals. With use of spectral Fourier analysis wavelet-transformation of oscillations significanlty extending possibilities of the seismic method at revelation of prognostic signs of crack formation and compression was applied. It is shown that the dynamics of ice processes can be connected with oceanic swell and tidal events. A possibility is created for obtaining new results in the investigation of large-scale mechanics of sea ice.

Turbulent heat exchange characterisics in sea ice ridges areas

The studies of the features of turbulent heat exchange were carried out for the first time in domestic practice near ice ridge areas of sea ice using an unmanned aerial vehicle (UAV) as part of the expedition "Transarktika-2019" onboard the R/V “Akademik Tryoshnikov”. An original measuring complex designed in AARI, was used to assess the characteristics of the ice surface (ice ridges, flat areas of ice). This made it possible to obtain comparative estimates of the albedo and surface temperature of different morphometric structures of the sections of the ice field, where the expedition's ice camp was organized. Measurements of air temperature and wind velocity were carried in the atmospheric surface layer on flat snow-covered areas of sea ice out from the windward and leeward sides of the ridge in parallel with the UAV flights. As a result of the experiments, it was found that the ice ridges areas have a lower albedo and surface temperature compared to neighboring areas of flat sea ice on average. Turbulent heat fluxes from the windward side of the hummock ridge exceed similar values recorded from the leeward side under conditions of unstable stratification in the atmospheric surface layer and exceed the fluxes calculated for conditions of flat ice on the sections with absence of hummocks, on average. In total, the nature and intensity of turbulent heat conduction in the ice ridges area differs from the analogous values observed on the flat sea ice cover. It is possible that the assessment of heat conduction with the atmosphere requires a certain revision, against the background (within the conditions) of thin first-year ice increasing which is more prone to hummocking than multi-year ice.

On the results of studying ice ridges in the Shokal'skogo Strait, part III: New data

The paper presents information on the studies of the first-year ice ridges conducted by the AARI experts in April–May 2018 in the fast ice of the Shokal'skogo Strait (Severnaya Zemlya Archipelago) using hot water drilling with computer recording of the penetration rate. Boreholes were drilled along the cross-section of the ridge crest at 0.25 m intervals mainly. One of the ice ridges had an unusual configuration: the sail crest was on the edge of the perpendicular extended keel crest. Cross-sectional profiles of ice ridges are illustrated. The records of thermodrilling rate revealed the presence of residual ice fragments in the keel of the ice ridges. The sail height varied from 2.9 up to 3.2 m, the keel depth varied from 8.5 up to 9.6 m. The average keel depth to sail height ratio varied from 2.8 to 3.3, and the thickness of the consolidated layer was 2.5–3.5 m. The porosity of the unconsolidated part of the keel was about 23–27%. The distributions of porosity versus depth for all ice ridges are presented and discussed.

Development of environmental contours for first-year ice ridge statistics

Ice ridges represent a major threat to ships and offshore structures in areas with sea ice but no icebergs, since they frequently determine and govern the structural design loads. This work focuses on the development of environmental contours for first-year sea ice ridge statistics, which are able to represent the key parameters that will influence the extreme loads that would be acting on ice-capable vessels sailing in Arctic regions. Based on the inverse first order reliability method (IFORM), the development of environmental contours to be applied for the reliability-based design of ice-capable vessels in Arctic regions is elaborated. The number of relevant parameters and hence the dimension of the space containing the environmental contour will depend on the particular ice-vessel interaction model that is to be applied. Furthermore, the influence from the degree of correlation between the environmental parameters as well as from the number of ship-ice ridge interaction during the voyage on the environmental contour shapes are studied.

Experimental investigation of rate dependency of freeze bond strength

The effects of deformation rate on the shear strength of freeze bonds have been investigated through a series of Asymmetric Four-Point Bending (AFPB) experiments. Two submersion times of 30 min and 24 h have been considered, while the deformation rate has been varied from 0.01 to 100 mm/s. Ice specimens with an initial temperature of −18 °C have been subjected to a constant confinement of 25 kPa during formation and shearing of the freeze bonds. Failure of the bonds proved to be highly dependent on deformation rate, where more strain was observed prior to failure of the bond for slower deformation rates. The shear strength of the bond for both submersion times showed a general decreasing trend with increased deformation rate, which is of significant importance in characterizing the properties of ice ridge/rubble strength. Previous ice rubble strength experiments, as well as ice ridge keel gouging tests, have reported the same failure rate-dependency, highlighting the role of freeze bond failure on rate effects. Compressive strength measurements of solid ice presented in the literature have been observed to follow similar trends within the range of strain rates used in present study, where the failure mode appears to transition from ductile to brittle with increasing deformation rate. While more work is needed to understand the mechanisms associated with the rate dependency of freeze bond, this general observation suggests the rate dependency of ice ridges/rubble may indeed be related to the behavior of ice as a material, rather than being associated primarily with factors such as inertial and pore pressure effects, which have been previously proposed as the principal controlling mechanism.

Morphometry and Internal Structure of Ice Ridges in the Kara and Laptev Seas

Morphometry and Internal Structure of Ice Ridges in the Kara and Laptev Seas

Laboratory tests to investigate the initial phase of ice ridge consolidation

During lake/sea ice ridging and river ice jamming, broken ice blocks experience transient heat conduction. In present work, this process is represented by submerging a cold fresh-ice block into fresh water at freezing point. The thermal behavior of ice was investigated both experimentally in the cold laboratory of Norwegian University of Science and Technology and numerically with Finite Differential Method (FDM). Most thermal properties of fresh water and fresh ice are well known except the heat transfer between ice and water (convective flux). Ice pieces with varying initial thicknesses and temperatures were applied while ice growth and temperature histories were measured. The physical experiments were performed to obtain a heat transfer coefficient (h), which was essential to calculate the convective flux. The two dimensionless numbers, Fourier and Stefan numbers, were used to study the development of ice temperatures and the ice growth. During the process the convective flux has limited influence on ice temperature while it reduced the maximum ice growth. This is because new ice that forms on the water-ice interface insulates the original ice from the water. In other words, the dimensionless temperature development is governed by the Fourier number alone. The ice growth, on the other hand, is influenced by the convective flux, so that a higher initial thickness and/or a lower initial temperature decreases the ice growth fraction. A balance of latent heat, inertia and convective flux shows that an increase of convective flux directly reduces latent flux and consequently the ice growth. The overall results from simulation and experiments demonstrate that an areal scalar (convective flux) and a volumetric scalar (latent energy flux) cannot be scaled simultaneously. Therefore, the dimensionless ice growth is a function of Stefan number and modified by convective flux, which is parameterized by initial temperature and thickness.

Forms of piled ice at the southern coast of the Baltic Sea

The paper presents the topography, morphology, and structure of various forms of piled ice observed at the southern coast of the Baltic Sea. The authors distinguished pressured ice, grease ice ridge, ridge ice, and hummock ice, based on the results of observations, measurements and photographic documentation that were collected by the authors in the years 1979–2019. Cross-sections of the forms were prepared based on the results of manual drilling. The recognised forms were then classified according to their structure, topography, and morphology as well as the genetic conditions of the region. The distinguished forms of piled ice differ not only in terms of the type and structure of the ice that they consist of, but also in terms of topography and the piling factor: wind, wave movements, and currents.

Evaluating Landfast Sea Ice Ridging near UtqiaġVik Alaska Using TanDEM-X Interferometry

Seasonal landfast sea ice stretches along most Arctic coastlines and serves as a platform for community travel and subsistence, industry operations, and as a habitat for marine mammals. Landfast ice can feature smooth ice and areas of m-scale roughness in the form of pressure ridges. Such ridges can significantly hamper trafficability, but if grounded can also serve to stabilize the shoreward ice. We investigate the use of synthetic aperture radar interferometry (InSAR) to assess the formation and movement of ridges in the landfast sea ice near Utqiaġvik, Alaska. The evaluation is based on the InSAR-derived surface elevation change between two TanDEM-X bistatic image pairs acquired during January 2012. We compare the results with backscatter intensity, coastal radar data, and SAR-derived ice drift and evaluate the utility of this approach and its relevance for evaluation of ridge properties, as well as landfast sea ice evolution, dynamics, and stability.

Satellite Observations for Detecting and Forecasting Sea-Ice Conditions: A Summary of Advances Made in the SPICES Project by the EU’s Horizon 2020 Programme

The detection, monitoring, and forecasting of sea-ice conditions, including their extremes, is very important for ship navigation and offshore activities, and for monitoring of sea-ice processes and trends. We summarize here recent advances in the monitoring of sea-ice conditions and their extremes from satellite data as well as the development of sea-ice seasonal forecasting capabilities. Our results are the outcome of the three-year (2015–2018) SPICES (Space-borne Observations for Detecting and Forecasting Sea-Ice Cover Extremes) project funded by the EU’s Horizon 2020 programme. New SPICES sea-ice products include pancake ice thickness and degree of ice ridging based on synthetic aperture radar imagery, Arctic sea-ice volume and export derived from multisensor satellite data, and melt pond fraction and sea-ice concentration using Soil Moisture and Ocean Salinity (SMOS) radiometer data. Forecasts of July sea-ice conditions from initial conditions in May showed substantial improvement in some Arctic regions after adding sea-ice thickness (SIT) data to the model initialization. The SIT initialization also improved seasonal forecasts for years with extremely low summer sea-ice extent. New SPICES sea-ice products have a demonstrable level of maturity, and with a reasonable amount of further work they can be integrated into various operational sea-ice services.

Pipeline shore crossing approaches in Arctic conditions

The development of the Arctic region will entail the construction of new infrastructure, in particular, subsea pipelines. Considering the lack of actual field practice, ecosystem vulnerability and lack of common Arctic international standards, their development will be a big challenge, in particular, in the shore crossing zone. The design and construction ofpipelines in the shore crossing area require a special approach that takes into account environmental and technological aspects of development. This work is aimed at analysing and determining environmental and technological factors influencing the design of offshore pipelines in the Arctic coastline. The paper presents theoretical and analytical work and the research isapplied to a specific case study (pipelines from the Leningraskoye field to shore), through engineering calculations. Currently, there are five Arctic projects with shore transition areas for which trenching has been implemented. In order to determine the best shore crossing approach, it is important to consider the following environmental conditions: ice encroachment; ice ridges; shoreline erosion; permafrost thawing. Environmental characteristics should predetermine the choice of approach. Among three existing methods: trenching, tunnelling and horizontal directional drilling (HDD), the micro-tunnelling method is recommended for the Leningradskoye field in combination with a cofferdam corridor to protect the buried pipe from waves and ice in the nearshore area. In order to protect the surrounded permafrost from melting seasonal cooling-device is recommendedto be used. The burial depth is determined to be more than 3.52 m in accordance with Force model calculations of ice ridges scouring depth. On the basis of research, the general choice-making diagram was proposed for Arctic shore crossing areas.

Tides in the southern area of the Kara Sea in the vicinity of the Belyi island

A number of promising hydrocarbon deposits are known in the south-western part of the Kara Sea. A safe development of these deposits requires hydrometeorological support, including sea-level observations. The paper deals with sea-level data of autonomous anchored buoy station. The period of observation is about 2 years, and the observation dataset is divided into 2 periods due to the displacement of the buoy station. The coordinates of the first position of the buoy station are known but they had been changed after the displacement (possibly due to the action of the ice ridge keels).Data from two time series of observations are studied by harmonic analysis, using the method of least squares by AARI version. According to the average monthly and mean annual values of the main tides it is found that the data includes two independent series. It is determined that the second series may be considered uniform. In order to locate of the anchored buoy station we calculated new coordinates using the empirical tidal charts of the M2 wave.As a result, the harmonic constants of the eight main tidal waves for the Belyi Island area are presented for the first time. The new data confirms the amphidromic system in tides O1 and Q1 , between the Zhelaniya Cape and the Belyi Island. According to the new data the maximum seasonal variation in the range of M2 tide was observed in June, and the minimum of the phase angle was observed in July. This unusual seasonal variation of the M2 tide corresponds to previous observations data from the Uedinenia Island.The authors have no competing interests.

On the results of studying ice ridges in the Shokal'skogo Strait, part I: Morphology and physical parameters in-situ

The paper presents information on the studies of the first-year ice ridges conducted by the AARI experts in April–May 2016 in the Shokal'skogo Strait (Severnaya Zemlya Archipelago) using hot water drilling with computer recording of the penetration rate. Boreholes were drilled along the cross-section of the ridge crest at 0.25 m intervals mainly. The results of a detailed study of one of the ice ridges are presented. The sail height varied from 2.5 up to 3.4 m, the keel depth varied from 8.3 up to 10.3 m. The average thickness of the consolidated layer was 2.2–2.4 m. Cross-sectional profiles of the ice ridge are illustrated. Ratio of the mean CL thickness of ice ridge to the mean thickness of level ice was equal 1.7. The distribution of salinity in the upper part of the CL is Z-shaped, and on the scale of the entire ice column, C-shaped. The CL growth rate is approximately twice as high as the growth rate of level ice. It was detected that the ridged ice was slightly stronger than the level ice. The porosity of the ice ridges is investigated in Part II.

О возможности идентификации крупномасштабных областей всторошенного льда в Арктике по данным скаттерометра ASCAT

О возможности идентификации крупномасштабных областей всторошенного льда в Арктике по данным скаттерометра ASCAT