Hydrographic observations, carried out in March-May, 2019 during “Transarktika-2019” expedition onboard R/V “Akademik Tryoshnikov” allowed studying mechanisms of Atlantic Water (AW) transformation in the Barents Sea. Although this research topic is rather traditional for oceanographic studies, there are still a number of questions, which require clarification. Among these is a deeper understanding of the AW transformation in specific regions in cold season, when the coverage by observations is scarce. In this study we performed temperature and salinity (TS) analysis of conductivity — temperature — depth (CTD) data, collected in the north-eastern “corner” of the Barents Sea — this is the area with difficult access in winter due to high concentration of pack ice. The results allowed identification of areas along the pathways of AW branches, where various types of open sea convection and cascading acted as dominant processes of AW properties change. We distinguish several driving mechanisms controlling modification of the waters of Atlantic origin. An advantage of winter measurements is that the active stage of AW transformation mechanisms is explicitly observed at the consecutive CTD sections.

Arctic summer and winter sea-ice extent is continuously declining as a result of climate change, affecting the hydrography and biogeochemical cycles on the seasonally ice-free Eurasian Shelves. The prolongation of the open-water season causes higher sediment resuspension and coastal erosion due to larger wind fetch and wave heights. This impacts the optical properties of the water column and hence biological productivity in this region. During “Transarktika-2019” leg 1 in late winter 2019, a comprehensive dataset of filtered water samples and optical data was collected throughout the central and northern Barents Sea. Combining suspended particulate matter concentrations obtained from water samples and optical data revealed a pronounced bottom nepheloid layer on the Barents Sea shelf even under ice-covered conditions. Moreover, the data indicate that the Franz Viktoria Trough could be a major pathway for sediment transport into the Eurasian Basin. Therefore, to link changes in sediment distribution and its impact on the ecosystem under a warming climate, further studies of sediment dynamics are required, particularly during winter.

We discuss the experience of conducting special oceanographic observations in the ice camp of the experimental drifting station. In a changing climate the Barents Sea is exposed to an important change in a heat and salt balance and a system of ocean currents. These changes are related to the distribution of the Atlantic waters, surface waters and sea ice, so a drifting station appears to be the best-adapted platform for complex simultaneous measurements of sea water properties and phenomena. The drifting station was organized as a “vessel — ice” camp during the first leg of the “Transarktika-2019” expedition, and the following characteristics were measured: temperature, salinity, ocean currents and turbulence. A detailed description of the experimental station is presented: three sites on ice with CTD-strings, one equipped additionally with ADCP and one site on ice with a turbulent cluster equipped with a 3D velocimeter, ADCP and CTD. The RV “Akademik Tryoshnikov” was another platform for oceanographic measurements. We present some results of a qualitative analysis of the obtained data. The conditions of the experiment are considered as inadequate for studying the characteristics of internal waves, but we state the efficiency and the potential of the developed approach of in situ observations in a turbulent cluster for calculation of fluxes and discuss the obtained from CTD thermal structures. Finally, we evaluate the possibility of application of the obtained experience for future drifting ice camps in the North Pole.

On the “Transarktika-2019” expedition, works were carried out for determining the physical and mechanical characteristics of frost field of the first-year sea ice and the field of second-year ice.
The thickness of the ice cover was determined by contact and non-contact methods, the temperature, salinity and density of ice, the strength of the samples at central bending and uniaxial compression, as well as the local (borehole) strength of ice were measured.
Studies have shown that most of the field is an ice formation formed in the process of dynamic metamorphism. At the beginning of the expedition, an ice floe passed through a section of warm surface waters. This led to the disappearance of the openwork layer on the lower boundary of the ice and stopping the growth of ice from below. During the observation period, the average temperature and salinity of the deformed ice increased, while the average density decreased. The values of mechanical characteristics decreased with increasing temperature and brine volume. The average borehole strength were close to the values obtained by the quadratic approximation for ice in the area of the Ice Station “Cape of Baranov”. The physical and mechanical properties of the level ice are generally similar to the properties of ice, composed mainly of fibrous structures. The ratios between the borehole strength and the strength under uniaxial compression of ice samples drilled parallel to the ice surface were 4.5 and 4.7, which corresponds to the literature data.
The thickness of the second-year sea ice at the place of work was 166 — 169 cm, the snow height was 27 cm, the raft of the ice surface above the water surface was 15 cm. The average ice temperature was –4.0 °C. Second-year ice can be divided into three parts that differ in their physical properties. The upper part (0 — 10 cm) was formed in the autumn. The second part (10 — 85 cm) is ice that has undergone seasonal thermometamorphic changes. The lower part was formed during the natural growth of ice from below at the current season.

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.

The paper presents the results of comparison of contact measurements of ice thicknesses and snow heights performed at the points of the hydrological stations of the “Transarktika-2019” expedition in April 2019 north of Franz-Josef Land archipelago, with altimetry observations of the Cryosat-2 satellite and numerical estimates of the PIOMAS (Pan-Arctic numerical Ice and Ocean Modeling system and data Assimilation). A significantly better correspondence is predictably shown between the variability of the ice thickness directly measured and observed using the CryoSat-2 satellite than that for the numerical PIOMAS system estimates. A trial correction of the algorithm for calculating the ice thickness by replacing the climatic values of the ice density, snow density and height with data from direct measurements also predictably improves the quality of calculating the ice thickness from satellite observations. The mean / route mean square differences obtained for ice thicknesses (+44/+96 cm for uncorrected and +30/+95 cm for corrected CryoSat-2 satellite, –14/+81 cm for PIOMAS system) and snow height (–4/+12 cm for CryoSat-2 satellite, –15/+12 cm for PIOMAS system) show the scale of uncertainty in estimating sea ice thickness and snow height for areas dominated by medium and thick first-year ice.
An anomaly of the ice thicknesses observed during the expedition is given in comparison with the background characteristics based on historical ice charting data for 1970s — 1990s, earlier High-Arctic aircraft “Sever” expeditions during 1950s — 1970s and the stated remote observations and numerical estimates for 2000s — 2019. Comparison shows that the AARI expedition was actually carried out in one of the most favorable years for ice research in the last decade for this region — the average ice thickness in April 2019 was 15 — 28 cm higher than that for the interval 2011 — 2019 with a slightly lower (1 — 2 cm) height of the snow cover. In the earlier period of the 1970 — 1990s this area was characterized by significantly thicker old ice with characteristic thicknesses ~ 60 cm more than in April 2019.

For the first time experience was gained with the operation of Russian equipment for water content and temperature remote sensing of the lower atmosphere in the Arctic. The comparison the results of measurements by radiometric systems with data of radiosoundings in wide range of meteorological conditions had been executed.
It is shown that mean difference between integral atmospheric water content, measured by water vapor radiometer WVR, and calculated from radiosoundings data does not exceed 6 % with standard deviation 0.54 kg/m2 and significant correlation coefficient 0,92. Analysis the data of meteorological temperature profiler MTR-5 allows to conclude that in general its adequately reproduce air temperature profiles in the atmospheric lower 1000 m layer. Some deviations take place only in cases of large temperature gradients.
Preliminary analysis of WVR data showed that monthly mean value of integral atmospheric water content in area under study in April 2019 year practically coincides with calculated from radiosoundings, performed in 1983—1988 years at the polar station Barentsburg, nearest to the drift region, 3.61 and 3.62 kg/m2 respectively. Same time hourly mean values of integral atmospheric water content during drift varied from 2 to 10 kg/m2, with extreme values recorded between April 15 and April 20, probably due to intensive transport of air masses of the Atlantic origin.
Based on MTR-5 data it was concluded that despite differences in sounding technology, the place and time of observations, the statistics of inversions registered during drift correspond well to statistics of inversions, recorded on the Arctic coastal stations and over sea ice cover of the Weddell Sea in winter.

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.

The paper presents the characteristics of the coarse clasts (psephites, larger than 1 cm) sampled in the northern part of the Franz Victoria Trough (Barents Sea) during the “Transarktika-2019” expedition. The studied sedimentary section was formed during the transition from the last deglaciation environments to the marine Holocene settings. The amount of psephites in deglacial sediments is much higher than the one in Holocene sediments. The petrographic composition of the psephites, their roundness (according to Waddell and Khabakov classifications) and shape (according to Zingg classification) were studied in detail. It is shown that the majority of psephites is represented by non-rounded or poorly rounded varieties. Isometric and disc-type shapes are predominating among coarse clasts. Isometric psephites prevail in “deglacial sediments”, while disc-shaped, bladed, and rodlike, as a rule, are current in marine Holocene sediments. The petrographic composition of psephites is mostly represented with carbonate (limestone and dolomite) and sandstones. The amount of carbonates increases from the Holocene to the deglacial part of the sediment section. Other rocks found in smaller quantities are represented by quartzites, cherts, shales, basalts, crystalline schists, gneisses, granites, pyrite. During the last deglaciation at the Late Pleistocene the iceberg rafting was the main mechanism of psephites delivery to the sampling points. The major sources of the icebergs were Franz Josef Land and the Belyi — Victoria Islands region. Rocks of Franz Josef Land are represented mainly by Cretaceous gabbro-basalt complex and Triassic sandstones and siltstones. Upper Paleozoic terrigenous and carbonate rocks, as well as Proterozoic metamorphites, occur in the west of the studied area (the area of the Belyi — Victoria Islands). The results of studying the petrographic composition of psephites allow us to conclude that during the last deglaciation icebergs from both sources were heading north towards the Nansen Basin through the Franz Victoria Trough. Both streams of icebergs failed to reach the opposite sides of the Franz Victoria Trough, mixing with each other approximately in the axial part of the trough and leaving it in northern directions.