Thickness Of Consolidated Layer Research Articles

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.

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.

Consolidation of fresh ice ridges for different scales

This study characterizes the refreezing process of deformed ice. Twenty laboratory experiments in ice ridge consolidation were conducted to study the influence of ridge blocks size, initial temperature, and top surface roughness on the consolidation rate. Experiments covered a ridge block thickness range of 2–6 cm, initial block temperatures from −1 °C to −23 °C, ridge sail height up to 3 cm, and consolidated layer thickness up to 14 cm. Experiments were conducted with the average value of the convectional heat transfer coefficient of 20 W/m2K. The presented analytical model for ridge solidification was able to predict the observed ice growth rates and differences between level ice and consolidated layer thicknesses at different stages of the experiments. For the provided experiments, the consolidated layer was as much as 2.2–2.8 times thicker than the surrounding ice level. The consolidation rate was lower than in the analytical solution at the start of the experiment and approached the analytical solution only when the thickness of the surrounding level ice was larger than the ridge void width. The developed numerical model confirmed the observed experimental effects from the block size, initial temperature and surface roughness. Both numerical and analytical models can predict solidification rates for previous studies at the large range of scales for both fresh and saline ice. The advantages of the simplified experimental ridge geometry include high accuracy of the main parameters governing the process, including the ridge macroporosity.

Morphology, internal structure and formation of ice ridges in the sea around Svalbard

The results from 3 years of comprehensive field investigations on first-year ice ridges in the Arctic are presented in this paper. The scopes of these investigations were to fill existing knowledge gaps on ice ridges, gain understanding on ridge characteristics and study internal properties of ice. The ability of developing reliable simulations and load predictions for ridge-structure interactions is the final principal purpose, but beyond the scope of this paper. The presented data comprise ridge geometry, ice block dimensions from ridge sails, ice structure in the ridge and values on the ridge porosity and the degree of consolidation. The total ridge thickness conformed to other ridges studied in the same regions. The consolidated layer thickness was on average 2–3 times the level ice thickness. Minimum 33% and in average 90% of the ridge keel area was consolidated. The distribution of ice block sizes and block shapes within a ridge appears to be predictable. A new approach for deriving a possible ridging scenario and ridge age is presented. Different steps of the ridge building process were identified, which are in good agreement with earlier simulated ridging events. After formation of very thin lead ice between two floes deformation occurs through rafting and ridging until closure of the lead. Subsequently the adjacent level ice floe fractures proceeding ridge formation until ridging forces exceed driving forces. A time span of 10 days could be assessed for a possible ridge formation date, estimating the ridge age of the studied ridge located east of Edgeøya at 78° N to be 7 to 8 weeks.

Effect of vertical inhomogeneity of the ridge keel filling on its freezing rate

Field data on ice ridges in the south-eastern and eastern parts of the Barents Sea collected by specialists of the Arctic and Antarctic Research Institute (AARI) in 2003–2007 has been used in attempt to understand the vertical inhomogeneity of the ridge keels filling. New ridges originated from one-year sea ice (with no consolidated layer or or less than 5–10 cm thick) have been analyzed. Reduction of original observations under certain additional assumptions has allowed formulating the vertical distribution of the ridge keel fill factor. This approximation has been applied in the one-dimensional thermodynamic ride model developed in AARI to simulate the ice ridges behavior in the Central Arctic and Arctic seas. The modeling of ridge freezing rates for different geographical sites has shown the more intensive freezing of ridge keels in initial stage than expected from previous modeling runs. The new results are consistent with field observations on consolidated layer thickness in ridges. Model calculations for a longer period show no big difference in results obtained with or without the approximation proposed.

Engineering Properties of Sea Ice Ridges in the Barents Sea in 2012-2014 Years for Evaluation of Ice Loads on Offshore Structures

Results of studies of ice ridges in field conditions are presented. Ice ridges investigated in the Barents Sea the proximity of the South-East of Svalbard archipelago. Five ice ridges are surveyed during research cruises in 2012-2014 years. Main engineering properties ice ridges as thickness of consolidated layer, height of sail and depth of keel were obtained. Results of research are of primary importance for evaluation of ice loads in studied area in Barents Sea.

Internal structure and porosity of ice ridges investigated at «North Pole‐38» drifting station

Abstract The paper presents the investigation results of morphometric characteristics of three first-year ice ridges conducted in March–June 2011 at «North Pole‐38» drifting station. The height of the ice ridge sail ranged within 3.3–6.1 m; keel draft, from 10.2 to 18.9 m. 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 ridges are illustrated. In each borehole, ice ridge porosity was calculated as the ratio of the length of all voids to total length of the borehole. Distribution of ice ridge porosity along the cross-section seems to be rather regular. Depth-wise distribution of volume content of solid ice phase is shown for the investigated ice ridges. Average thickness of consolidated layer of ice ridges ranged within 0.8 … 2.6 m.

A comprehensive analysis of the morphology of first-year sea ice ridges

Abstract A review of the morphological properties of over 300 full-scale floating first-year sea ice ridges has been made, including measurements from 1971 until the present time. Ridges were examined from the Bering and Chukchi Seas, Beaufort Sea, Svalbard waters, Barents Sea and Russian Arctic Ocean for the Arctic regions; and from the Canadian East Coast, Baltic Sea, Sea of Azov, Caspian Sea and Offshore Sakhalin for the Subarctic (or temperate) regions. Grounded ridges were excluded. A wide catalogue comprising the ridge thicknesses (sail, keel and consolidated layer), widths and angles as well as the macroporosity and the block dimensions is provided. The maximum sail height was found to be 8 m (offshore Sakhalin), and the mean peak sail height was 2.0 m, based on 356 profiles. The mean peak keel depth is 8.0 m, based on 321 profiles. The relationship between the maximum sail height, hs, and the maximum keel depth, hk, for all ridges is best described by the power equation hk = 5.11hs0.69. The correlation differs depending on the region. For Arctic ridges a linear relationship was found to be the best fit (hk = 3.84hs), while for the Subarctic ridges a power relationship (hk = 6.14hs0.53) best fit the data. The ratio of maximum keel to maximum sail is 5.17 on average (based on 308 values), and has also been calculated for each region mentioned above. Arctic ridges generally have a lower keel-to-sail ratio than those in Subarctic regions. The statistical distribution of keel-to-sail ratios is best represented by a gamma distribution. The average sail and keel widths were 12 and 36 m, respectively. The relationships between the sail and keel widths and other geometrical parameters were also determined. Variation of sail and keel thicknesses within individual ridges has been compared with the variability of all ridges. Ridge cross-sectional geometry can vary greatly along the length of a ridge, even over a short distance. A study was made on sail block thicknesses, and it was found that they correlate well with the sail height with a square root model. The typical macroporosity for a first-year ice ridge is 22% (based on 58 values) with an average sail macroporosity of 18% (based on 49 values) and average keel rubble macroporosity of 20% (based on 44 values). The average ridge consolidated layer thickness was 1.36 m based on 118 values. The variation of the consolidated layer was examined, and it was found that the layer tends to grow evenly with time over the width of the ridge cross section. A greater spacing between the measurements seemed to affect the variation, as it decreased with an increasing distance between each borehole. A statistical analysis based on 377 measurements of the consolidated layer of ridges in the Barents Sea showed that the gamma distribution well describes the distribution of the consolidated layer thicknesses in that area.

Hummocks near the North Pole 35 drifting station

Study of hummocks is a very important applied and scientific problem. The main objective of this work is representing new information on structure of hummocks that were studied in the spring time at the North Pole 35 drifting station. In this paper, methodology and results of studying several hummocks with different morphology are considered. The maximum hummock keel draft varied from 3.5 to 14 m, while the maximum sail height was between 2.5 and 3.9 m. The hummock porosity and porosity of the unconsolidated part of its keel varied in the range of 6–18 and 4–26%, respectively. The average thickness of the hummock consolidated layer stayed in the range from 1.8 to 2.4 m. It was found that relatively small sail heights do not affect the consolidated layer thickness, however higher sails influence on the consolidated layer size. The higher the hummock sail, the less its consolidated layer thickness is.

Thermodynamic consolidation and melting of sea ice ridges

Abstract Thermodynamic models describing consolidation of sea ice rubble and slush were formulated then explicit solutions of these models were constructed and analyzed. It was shown that the thermal inertia, the dependence of the specific heat capacity of sea ice on the temperature and the influence of brine salinity in the slush influence the consolidated layer thickness. The finite element method and the computer program FEMLAB were used to calculate consolidation and melting of the two-dimensional model of an ice ridge consisting of solid ice blocks, slush and sea water. Numerical simulations were carried out using five groups of input parameters characterizing the natural variability of environmental conditions and turbulent heat conductivity of sea water. Variations in ice volume and porosity, the thickness and shape of the consolidated layer, temperature distribution inside the ridge and heat fluxes from the ocean and into the atmosphere were analyzed depending on input parameters of the model. It was shown that vertical extension of the consolidated layer of a two-dimensional ridge can locally exceed the consolidated layer thickness calculated with a one-dimensional model. The results of the simulations were interpreted by analyzing of virtual “drilling” data. The average ridge porosity according to the drilling data was shown to be dependent on the number of drilling holes and their location on the ridge.

Internal structure of ice ridges and stamukhas based on thermal drilling data

During the resent years (1996–2005) the Arctic and Antarctic Research Institute performed expeditionary research in marginal seas. One of the tasks consisted in the determination of morphometric characteristics of ice ridges and stamukhas with the help of thermodrilling, with recording of the rate using a computer. The record of the penetration rate of the thermodrill and the water column pressure in the borehole as a function of depth, as well as processing of the recorded data, enabled to get information about the boundaries of consolidated layer. Principles of interpretation of the records of penetration rate of the thermodrill are discussed. Depth-wise distribution of volume content of solid phase of ice is presented for ice ridges and stamukhas in the various regions. Methodological grounds are discussed, of the determination of this distribution, based on the results of averaging of the data obtained through thermodrilling. Internal structure of ice ridges and stamukhas is discussed, for the Pechora Sea, the Sea of Okhotsk, the Caspian Sea, the Sea of Azov and near-polar district of Arctic basin, as well as its consideration with respect to other literary sources. Based on the accomplished analysis of the internal structure of ice ridges and stamukhas of the shelf of the Sakhalin Island and the Pechora Sea, a conclusion was made, that the thickness of consolidated layer determined based on the rate of drilling, according to subjective perception of the operator, frequently proves to be overestimated. The ratio between average thickness of consolidated layer of ice ridges and average thickness of level ice which surrounds the same in the regions in question varies within the range of 0.83…1.63, about 1.2 on the average. For stamukhas this ratio varies within the range of 1.3…2.1, about 1.7 on the average. Average porosity of the investigated ice ridges varies within the range of 12–28%, of the stamukhas — 7–20%.