The paper presents the results of a study of the morphometry of a first-year ice ridge formed in November during the drift of the "North Pole-41" station from December to August using thermal drilling and thermistor strings. The dynamics of the consolidated layer thickness include an increase in the thickness in winter-spring, continued consolidation in the first half of summer, and subsequent melting. Keel consolidation increased from 31% in early January to complete freezing in early August; the contribution of summer processes to the increase of the consolidated layer thickness during the period of its maximum development was 8%.

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.

Morphological characteristics of three first-year ice ridges were investigated in the Shokalsky Strait in April and May 2019 by hot-water thermal drilling with the recording of penetration rate. Boreholes were drilled along the ice ridge cross-section with an interval of 0.25 m. The ice ridge cross-sectional profiles are presented. The sail height for the investigated ridges varied within 1.8-2.7 m, and the keel draft varied from 7.0 to 9.1 m. The ratio of the keel draft to the sail height was equal to 2.7-5.2, the thickness of the consolidated layer was 2.4-2.7 m. The mean porosity of the unconsolidated part of the keel in the ice ridges made up 28-36%. The porosity distributions for the unconsolidated part of the keel along the drilling profile are given for the analyzed ice ridges. The main feature of one of the ridges was an almost rectilinear slope of the keel, which laterally extended for 16 m.

First-year ice ridge has been examined with respect to geometry and morphology at the Barneo ice camp in April 2013. Its characteristics are discussed in the paper. The sail height was 4.7 m, the keel depth was 8.6 m. The keel depth to sail height ratio was equal to 1.8. Structure of the keel of the examined ice ridge was too heterogeneous in its composition. Significant fragment in the keel of ice ridge is fully consolidated, its draft reaches to 5.8 m but the fragment's upper boundary is located at the sea level. This indicates the presence of hydrostatic unbalance. Away from the point of maximum keel draft on the cross-section, the average porosity of the unconsolidated part of the keel tends to increase, but again decreases at the periphery of the keel. The distribution of ice fraction in sea ice versus depth for the ice ridge is presented. Increased ice fraction corresponds to the consolidated layer. The depth of the lower boundary of consolidated layer is confirmed by distributions of ice temperature versus depth.

The paper presents new data on the texture and density of a unique natural object – perennial fresh landfast ice in the Gulf of Transcription (East Antarctica), obtained in January 2020. The main purpose of the work was a planned (scheduled) inspection of the landing site selected for the 63rd season of the Russian Antarctic Expedition (RAE), investigation of the ice core sampling and analysis of its texture, including measuring the ice density. The thickness of the ice cover at the core sampling site was 3.02 m. In the long-standing (perennial) fast ice, the new ice is formed mainly from below as a natural growing of the congelation ice. From above a new ice is formed in smaller volumes, and it is either the infiltration ice in spring or freezing of melt water on the surface in autumn. Infiltration ice does not contribute much to the old fast ice, remaining a seasonal phenomenon. The reasons for that are insufficient snow accumulation in winter and the lack of salt water in the subglacial layer. In the upper layer of ice, its density is minimal and amounts to 680–720 kg/m3, increasing with depth and approaching its maximum at the lower edge – 917 kg/m3. The average density of ice is 875 kg/m3. The effect of primary air inclusions (bubbles) on the density of ice which contains large crystals of tens of centimeters in size is approximately the same for the whole ice thickness. Significant changes in the density of ice are caused by secondary inclusions which are formed during the freezing of melt water in the runoff and riverbed flows. It is shown how a crack in the ice, probably thermal, is further transformed under the influence of temperature and melt water runoff into a sinusoidal channel. This is rather common phenomenon associated with the thermal physics of the ice cover, the melting–freezing processes, and surface tension. The period of the sinusoid increases linearly with depth (the coefficient of determination R2 = 0.99). Thus, the new data obtained allows expanding the present-day scientific notions on the role of physical processes in formation and evolution of long-standing (perennial) ice.

The Russkaya station (Marie Byrd Land, West Antarctica) was one of the wintering stations of the Russian Antarctic Expedition (RAE) before its conservation in 1990. Starting from the field season of the 65th RAE (2019/20), work is under way at Russkaya station to put it into operation as a functioning wintering station. Due to its significant distance from other RAE infrastructure sites and also due to severe climate, organization of logistical operations in this area requires a special approach. For the most effective transport communication with the station, it is planned to organize an airstrip to receive planes on ski landing gear on the surface of the outlet glacier. Glaciers of this type are often characterized by crevasses, which are not traceable on the surface, which makes it necessary to study the structural sub-surface features of the glacier. For this purpose, geophysical survey in the field season of the 65th RAE were carried out with usage of the GPR-method. GPR profiling at a frequency of 900 MHz allowed us to identify the crevasses and assess their morphometric characteristics, in particular the width and depth. The widest crevasses were examined in detail to improve the interpretation of GPR data. Based on the results of geophysical works, the boundaries of zones were determined, within which the crevasses are either absent, or their width does not exceed 0.6 m. In addition, by means of core drilling, values of ice density to a depth of 5 m from the surface were obtained, which correspond to the normative data on preparation of airfields for operation of airplanes on ski landing gear. Based on the results of geophysical and glaciological investigations, a site on the glacier suitable for runway preparation was identified. An area safe for organization of transport communication between the airfield and Russkaya station was also identified. It is adjacent to the hills of the oasis, as the glacier in this part is the most stationary.

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.

In May 2015, the old hummock located to the North of the Bennett island (the East Siberian Sea) was investigated using several methods, among which were water thermal drilling, tachometric and sonar surveys, underwater video recording, as well as techniques to determine the strength and physical properties of ice. It was found out that only a combination of different methods provides a way to correctly estimate the main morphometric characteristics of a large ice formation and to determine its volume and mass. Analysis of the internal structure of the hummock, obtained by the water thermal drilling with a record of the drilling rate on the logger, made it possible to reveal a composite character of the ice formation (the hummock consisted of two fragments - the large old one and the smaller first-year piece) and to estimate approximately its age (3-4 years). Comparison of the main morphometric characteristics of the old hummock with the average values of first-year hummocks, investigated in the same area and the time, showed that the old hummock had significantly greater geometric parameters: its volume and mass exceeded similar parameters of the average younger formation by factors 5.6 and 5.8, respectively. This significant difference allows suggestion that the reason is not the age but a composite structure of the old formation. The average thickness of the consolidated layer of the old hummock equal to 4.6 m is almost twice larger than similar parameter of a first-year hummock (2.33 m) while the average value of the thickness in the old part of the old hummock (5.22 m) is larger than that of a young one by the factor 2.2. Note also, that the old hummock is characterized by almost complete smoothness (impossible to separate individual blocks) and minimal porosity (1%) of its ice. The salinity and density of the ice composing the frontal part of the old hummock is much smaller than in first-year hummocks. The average density of ice in the old hummock, determined analytically from the buoyancy condition, was equal to 896 kg/m(3), while the average density of ice in the first-year hummocks, determined from measurements, - 917 kg/m(3).

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.

The article presents an analysis of the expedition results on morphometry and the internal structure of ice ridges. A regression equation connecting the consolidated layer (CL) thickness of ice ridges with the sum of degree-days of frost is proposed. The issue of the CL distribution inside the ice ridge is considered. It is shown that the largest CL thickness is observed in the zone, combining the maximum sail and keel. The averaged porosity distribution by vertical is derived, and the main regularities of its change inside the ice ridge are shown.

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.

A method for studying stamukhas using the modern field equipment is considered. The peculiarities of morphometric characteristics and parameters of the internal structure of stamukhas are analyzed. The interrelation between the consolidated layer thickness and the accumulated freezing degree days is derived for different seas. The comparative analysis of morphometric characteristics and the consolidated layer in the ice-covered seas of Russia is carried out. It is shown that the formation of stamukhas in different regions has specific features depending on the depth, bottom topography, drift characteristics, ice thickness, and dates of fast ice formation. The maximum thickness of the consolidated layer is registered in the Kara and Laptev seas.

The paper describes the morphometric characteristics of three first-year ice ridges investigated in April and May 2016 in the Shokal'skogo Strait (Severnaya Zemlya Archipelago). These studies were conducted using hot water thermal drilling with computer recording of the penetration rate. Boreholes were drilled along the cross-section of the ridge crest mainly at 0.25 m intervals. The main results of the ice ridges studies are given in Part I. Cross-sectional profiles of ice ridges are illustrated. In each borehole, porosity of an ice ridge was calculated as the ratio of the length of all voids to total length of the borehole. Processing of the results showed that when studying ice ridges for obtaining the porosity values close to the true ones, the boreholes should be drilled with a spacing not exceeding two meters. Away from the point where the keel has the maximum draft, the average porosity of the unconsolidated part of the keel tends to increase. This feature is a consequence of the effect of the Archimedes force and agrees with the model of porosity changes from the theory of granular media.

Three first-year ice ridges have been examined with respect to geometry and morphology in landfast ice of Shokal'skogo Strait (Severnaya Zemlya Archipelago) in May 2018. Two of the studied ice ridges were located on the edge of the ridged field and were part of it, because their keels extended for a long distance deep into this field. Ice ridges characteristics are discussed in the paper. These studies were conducted using hot water thermal drilling with computer recording of the penetration rate. Boreholes were drilled along the cross-section of the ridge crest at 0.25 m intervals. Cross-sectional profiles of ice ridges are illustrated. The maximal sail height varied from 2.9 up to 3.2 m, the maximal 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 non-consolidated part of the keel was about 23-27%. The distributions of porosity versus depth for all ice ridges are presented.

The article presents the results of an analysis of the expedition data on morphometry and internal structure of stamukhas, investigated in spring 2017 in the southwestern part of the Laptev Sea. Using a thermal drilling method, researchers obtained average and extreme values of all measured parameters and made an approximation by theoretical distribution functions. Analysis of sonar and tachometric survey data shows the average values of stamukha volume/mass to be more than five times greater than the average values of ice ridge volume/mass. The maximum duration of the recorded stamukhas’ drift was thirty days.

In last two decade, studies of ice ridge morphometry and strength properties have been actively carried out. Thermal drilling of ice and experiments to determine the local strength of ice using a borehole jack are performed. The paper discusses the issues of joint use of thermal drilling equipment and borehole jack for the ice cover research. Two approaches to the comparison of the results obtained by these two methods are considered. Average penetration rate versus local ice strength dependences are presented. With increasing ice strength and decreasing penetration rate the interval of changes in the ice strength increases and correspondence of the strength to the penetration rate decreases. Based on the results of ice ridges research, depth-wise distributions of local strength and thermal drill penetration rate are compared. Difference between the average thicknesses of the consolidated layer obtained from these distributions was 5 %.