The purpose of the paper is to analyze the large-scale peculiarities of ice age composition and thickness in winter period (October–May) along the entire stripe of the Russian Arctic seas from the Novaya Zemlya Archipelago to Alaska, as well as to assess the multi-year changes taking place in early 21st century. The source of the information used for the present paper is the electronic ice charts at the end of every month, developed in the AARI from 1997 to 2018.

On the average, during the period 1997–2018, from month to month, the consecutive and ordered changes of ice area of given age take place in accordance with the general ice thickness increase. In October–December the grey-white and first year thin ice (15–70 cm) prevails in the Arctic seas, in January–February — the first-year medium ice (70–120 cm), in March–May — the first-year thick ice (more than 120 cm).

The period from 1997 to 2018 consists of two parts (1997–2003 and 2004–2018) principally differing from one another by the peculiarities of ice age composition. The basic content of the changes in the 21st century is the decrease of relatively thicker ice area and increase of that of relatively thinner ice.

On the average, in the winter periods of 2004–2018, (1) the area of ice thinner than 70 cm (nilas, grey, grey-white and first year thin) became 12 % less than in 1997–2003, and (2) the area of ice thicker than 70 cm (first year medium, first year thick, second year and multi-year) became 18 % larger than in 1997–2003. The most significant changes regard to the second year and multi-year ice, their area in winter period decreased about 10 times. Decrease of the rate of first year ice growth is accompanied with delay of the dates when the first year ice reaches the values of 70 and 120 cm.

Correspondingly, the weighted mean ice thickness also changes. On the average, in 2004–2018 ice thickness has got about 40 cm less than in 1997–2003; by the end of cold period (May), ice thickness decrease from 153 to 117 cm.

The typical feature of the observed changes is an abrupt transformation from one climatic state of ice cover to another during only one hydrological year.

The Duration of Arctic Invasions (DAI) is known to be connected with various climatological indexes. This paper presents the results of a study of DAI changes in various sectors of the Northern Hemisphere from 1899 to 2017. To this end, we used the classification of circulating mechanisms of the Northern Hemisphere by B.L. Dzerdzeevsky.

The basic attention was paid to the study of the trend component of the temporal variability of the duration of Arctic invasions; to the assessment of long-period cyclic fluctuations of the DAI; and to the forecasting the duration of Arctic invasions over the next decade in the Northern Hemisphere sectors.

To analyze the components of the change in the duration of Arctic invasions and its forecast, we used: a description of the initial data using a linear trend, approximation of time series by the Savitsky-Golay method, spectral analysis and spectral-time analysis, as well as the component-harmonic method.

We found a significant increase in the duration of Arctic invasions in the Pacific and Atlantic sectors and its significant decline in the European and American sectors. In deviations from the trend, a powerful quasi-fifty-year component for five sectors is clearly manifested; whereas in the European sector the deviation is rather weak and quasi-thirty-year fluctuations dominate here. What is more, quasi-20-year fluctuations in the variability of DAI were revealed, we predict DAI estimates for the next 10 years by combining the trend and two quasi-cyclic fluctuations. According to our forecast an increase in the duration of Arctic invasions will occur from 2022 in the European sector. In the Atlantic sector, DAI growth will begin in 2019 and continue until 2023, and then DAI will fall. In other sectors, there will be a decrease in the duration of Arctic invasions starting from 2016. The decrease in American sector starts only from 2022.

The article presents the results of studies that complement each other. New methods of instrumental studies of the physical and mechanical characteristics of ice and ice cover are considered.

There is briefly described the complex system to developed in the AARI (Arctic and Antarctic research Institute) to determine the strength characteristics of ice formations in natural conditions. The results of determining the ice strength in wells (local strength) at the research station of AARI “Ice Base Cape of Baranov” are presented. The coefficient of comparison of local strength and strength of samples under uniaxial compression is obtained. This allows to determine the ice strength without sampling and testing of samples. On a large experimental material, linear and quadratic approximations for local ice strength were obtained. The influence of the indenter penetration rate on the local ice strength is studied.

There is considered the application of the contact remote method for monitoring the dynamic state of the ice cover in order to obtain new data for creating a method of predicting the phenomena of compression and destruction of sea ice in real time.

To study the large-scale mechanics of ice during dynamic processes in the air — ice — water system, a modular-block system for ice cover monitoring was developed. The layout of the system was tested in Arctic expeditions.

The developed complex system for determining the strength characteristics of ice formations in natural conditions and the modular-block system for monitoring the state of the ice cover complement each other, suggest their further development and improvement, provide wide opportunities for ice research.

The article presents the results of studies of the environmental properties of organochlorines which differ in properties and origin, in the lake ecosystems of the Bolshezemelskaya tundra (Nenets Autonomous Okrug, Russia). The purpose of this study was to evaluate and assess the levels, distribution characteristics and composition of organochlorines in the bottom sediments of small lakes located in the Adzva river basin in Pymvashor natural boundary (the northernmost location of the exit of thermal-mineral springs of the continental Europe) and in the adjacent area, outside this unique subarctic hydrothermal zone.

In order to meet this goal, multi-method (hydrochemical, geochemical, etc.) research was carried out using standard generally approved laboratory practices with their adaptation to the study goals. The quantitative content and composition of the target individual organochlorines were determined by gas chromatographic method with electron-capture detection.

The presence of chlorophenol compounds and polychlorinated benzenes (including persistent organic pollutants) was shown in the lakes sediments. The influence of specific microclimatic conditions of subarctic hydrothermal system on the composition and distribution of chlorophenol compounds in lake sediments was considered. In the small lake sediment core in Pymvashor natural boundary a reducing trend in the levels of organochlorines with depth has been recorded (conditioned among other things by the lithological features of bottom sediments). The chlorophenol compounds were found at highest concentrations (619.3–765.5 ng/g) in the sediment upper layers, rich in organic matter; chlorophenol composition was represented mainly by chlorinated phenols, most likely of biotic origin. A lower concentration (185.0 ng/g) of chlorophenol compounds of predominantly abiogenic origin was determined in the lake sediments outside hydrothermal system. The presence and levels of persistent organochlorine pollutants (pentachlorophenol 0.1–2.4 ng/g; hexa- and pentachlorobenzenes 0.4–3.6 ng/g) in the lake sediments were associated with long-range atmospheric transport from various origin sources in nearby regions and low-latitude territories.

In continental waterbodies of Antarctic oases specific algal communities are forming. The structure and dominating complex of species of this communities due to different distance from the seashore and latitude, the composition of the constituent rocks, altitude and the presence in the past of periods of contact with sea water is unique for different oases. It may vary in different waterbodies within one oasis besides.

Aim of the research is to describe different types of algal communities from the continental waterbodies of Schirmacher Oasis and it’s confinement to the different types of waterbodies.

Samples were collected from 173 waterbodies: 151 with stagnant water and 22 streams.

During the study 64 species of Cyanoprokaryotes were found, and this group usually dominated in communities. Also 14 most frequent species of Chlorophyta, 12 most frequent species of Bacillariophyta, 6 species of desmid algae, 2 species of Xanthophyceae, 1 species of Eustigmatophyceae were noted in benthos. Usually resting stages and in one case — life cells of Golden algae (Chrysophyceae, Synurophyceae) were found in mats on the bottom of big lakes. Plankton algae in most of the waterbodies had very low abundance and diversity and were strongly influensed by trophic level. Benthic algal communities were much more diverse and abundant. Eight sustainable types of benthic algal communities were revealed in continental waterbodyes of Schirmacher Oasis. Form, colour, and species composition of bentic films and mats strongly depended on temperature, conductivity and pH of the waterbody and its depth.

The purpose of the article is to identify the features and problems of spatial development of the regions of the North of the Russian Far East. The research was carried out under the project “Modeling the spatial development scenarios of Siberia and the Far East of Russia until 2030: features of the resettlement system” (RFBR grant No. 19-010-00836 A), which won the RFBR competition “Fundamental Scientific Research Projects”. The study is being conducted by the team of the Department of Geourbanistics & Spatial Development of ISPR FCTAS RAS since 2019 and is intended to last for three years. The main goal is to assess the current state of the resettlement system, develop strategic prospects and model alternative scenarios for the spatial development of the regions of the Siberian and Far Eastern Federal Districts. A key feature is the use of interdisciplinary methods based on a combination of economic, mathematical, sociological, statistical and scenario approaches to research. From a practical point of view, the project results will help to plan more rationally the spatial development the spatial development of the country’s regions. The analysis shows that the sociological methods of spatial research have large reserves but are not yet used to the full capacity. This article discusses the current problems of spatial development of the north of the Russian Far East. On the basis of the authors’ development of the empirical research model by a group of scientists of ISPR FCTAS RAS, in August 2019, the survey of respondents of the Kamchatka Krai, the Magadan Oblast` and the Chukotka Autonomous Okrug was conducted. The results of the opinion poll made it possible to identify differences in migration preferences, a number of features of the economic potential capacity and the quality of infrastructure, and the social sphere of the Far Eastern regions of the country.