As an important component of Arctic carbon cycle, riverine organic carbon export is very sensitive to climate change. In order to analyze the organic carbon output from 2004 to 2017 of Ob, Yenisei and Lena rivers in Siberia of Russia, river discharge and organic carbon data from the ArcticGRO (https://arcticgreatrivers.org/) were used in this study through mathematical statistical analysis and other methods. Results showed that the total annual organic carbon output of these three rivers is about 23 Tg, among which the dissolved organic carbon (DOC) output is approximately 18.55 Tg, more than half of the total in Arctic regions, and nearly 4 times of particulate organic carbon (POC) output. The output of annual DOC from 2009 to 2017 is significantly different from that of 1999-2008, DOC output of Ob River increased by 18% annually, Lena River increased by almost 70%, while Yenisei River dropped by 13%. The organic carbon output in spring and summer reached more than 85% of the whole year, with an output peak in spring, but the outputs of Ob River in spring and summer were almost the same. The organic carbon output characteristics of these river basins are different in seasonality, which was mainly affected by runoff, permafrost and human activities. Among them, the total DOC output has a significant positive correlation with runoff variation in terms of inter-annual and seasonal changes. In general, DOC concentration becomes larger as the discharge increases. Permafrost also has notable influence on river DOC and POC due to various types of distribution. Therefore, the study of the characteristics and influencing factors of the organic carbon output of Arctic rivers under climate change is conducive to in-depth understanding of the comprehensive response of the organic carbon output of Arctic rivers to climate and environmental changes, which lays a foundation for revealing the process of the Arctic carbon cycle under climate change.

The global warming has led to the acceleration of the melting of Arctic sea ice, and the opening of the Polar Silk Road has gradually been put on the agenda. In this paper, according to the navigation performance of eight important Russian ports reaching the Bering Strait through the Northeast Passage from 2030 to 2070, the sea ice data of six CMIP5 climate models under two RCPs and two ship types of PC6 icebreaker and OW (merchant ship) ship are adopted. Based on the study of the four factors of optimal route, navigation time, navigable mileage and navigation cost, the main conclusions are as follows: (1) With the change of time, the optimal navigation routes are gradually concentrated and orderly. The navigation capacity of merchant ship has been significantly improved, and by 2070 it will have the same navigation capacity as the PC6 icebreaker has. (2) The navigation time between the Russian ports and the Bering Strait has decreased by 14 h every 10 a, of which St. Petersburg Port has the most significant decline. By 2070, when the longitude difference between the Russian port and the Bering Strait increases by 1°, the navigation time of the port decreases by 0.4 h. (3) In the next 50 a, the navigable mileage of Northeast Passage will increase by 166 km every 10 a, among which the change pattern and average change pattern of navigable mileage in St. Petersburg Port are the most similar. (4) The navigation cost of the route from the Arctic port is reduced by $10,000 every 10 a, and the decrease of the total navigation cost of merchant ships is the most obvious under high emission concentration. Combined with the change of sea ice, the ports in central and western Russia have great potential for resource transportation. This study quantifies and evaluates the evolution of the navigation performance of the Northeast Passage under the future sea ice melting situation, which provides theoretical and data support for the navigation of the Northeast Passage and the Arctic port trade.

The accelerating global warming enhanced the Arctic sea ice melting, which made it possible to explore energy resources in the Arctic region. This study firstly analyzed the energy trade structure in the pan-Arctic countries, covering Arctic countries and the observer countries. Secondly, it uses correlation analysis to extract the direct geopolitical factors including energy dependence, energy importance, energy security, and indirect geopolitical factors including national power (military power and foreign investment influence), climate and environmental protection and social inclusive development, which might influence the willingness of the pan-Arctic countries to exploit the Arctic energy. Finally, we apply fuzzy-set qualitative analysis (fs/QCA) to examine the driving mechanisms of these geopolitical factors on the willingness to exploit the Arctic energy. The results showed that: (1) Arctic countries mainly serve as energy exporter while observer countries mainly serve as energy importer. The amount of China's energy imported from Arctic counties is small at current stage, but with a huge potential. (2) Energy dependence, energy importance, national power and social inclusive development are significantly correlated with the willingness on Arctic energy exploitation, acting as key geopolitical factors. (3) Key geopolitical factors drive or impede the willingness on Arctic energy exploitation through three major pathways, among which, national power together with energy dependence or energy importance behave as the major driving forces for most of the pan-Arctic countries, large countries in particular, such as Russia, USA, China and India. The second pathway is driven by national power but restricted by social inclusive development, including most European countries and Canada. The third pathway is mainly driven by energy importance while restricted by social inclusive development, mainly including Norway. Finally, this study provided coping strategies and suggestions on China's participating Arctic energy exploitation based on the energy trade structure and the driving mechanisms.

Global warming has caused a shrinkage of the Arctic sea ice cover. It endangered the environment, but made the Arctic channel possible. Therefore, the strategic position of the Arctic has been improved significantly. As a near-Arctic country, China has formulated relevant Arctic policies, which will be directly affected by the changes in the international relations between the eight Arctic countries (region). A comprehensive and real-time analysis on the variation characteristics of the Arctic geographical relationship is required in China, which can provide instructions for formulating political, economic and diplomatic countermeasures in the Arctic. Massive global real-time open databases, such as GDELT (The Global Database of Events, Language, and Tone) global news event database, provide news data from major media in various countries. And this makes it possible to monitor the geographical relationship in real time. Based on the GDELT database and the method of labeled-LDA (Latent Dirichlet Allocation), this paper explored the key elements in social development of eight Arctic countries (region) over the past seven years. This paper also constructed the national interaction network, and identified the evolution pattern of the relations between the Arctic countries. The following conclusions were drawn: (1) Arctic news focused on climate change and ice sheet melting, which had become the main driving factor for the change of international relations in the Arctic; (2) There was a strong correlation between the number of ice sheet melting news pieces and the sea ice area; (3) With the melting of the ice sheet, the social, economic and military activities in the Arctic were booming, and the competition for dominance was becoming increasingly fierce. Generally, a pattern dominated by Russia and Canada was formed.

The Northern Sea Route has been increasingly attracting the attention from countries all over the world due to its important strategic status. By calculating the economic costs of shipping among China-EU ports through the Northern Sea Route and China-EU trade complementarity index, this study builds a trade gravity model in stochastic frontier based on the Northern Sea Route, and explores the influencing factors of China’s import from and export trade to 18 European countries, which shows the following: (1) Taking the traffic volume of 12000 TEU for comparison, the economic costs of shipping along the Northern Sea Route are 1.58-2.80 times those based on the traditional passage among China-EU ports. (2) In 2000-2018, the proportion of the China-EU trade complementarity index based on China’s export (CE_ij) greater than 1 accounted for 52.63%, and countries with higher CE_ij included Iceland, Denmark, Norway, France, Sweden and the United Kingdom, while the proportion of the China-EU trade complementarity index based on China’s import (CI_ij) less than 1 accounted for 94.74%, with a declining trend. So, China’s import and export with 18 European countries were less complementary. (3) In terms of trade scale of China’s export to 18 European countries, the economic scale of trade partner countries has a greater influence than that of China, and the economic costs of shipping are significantly negatively correlated with the trade scale based on the Northern Sea Route; in terms of trade scale of China’s import from 18 European countries, the economic scale of trade partner countries has a greater influence than that of China, and the positive correlation relationship between the economic costs of shipping and the trade scale has lower confidence based on the Northern Sea Route. (4) If the Northern Sea Route was taken for the China-EU trade, the trade efficiencies of China’s export to 18 European countries and import from them declined and rose to varying degrees, respectively, which means that the trade efficiency of China’s import and export had large room for improvement. This study can strengthen the research foundation of relationship between China-EU shipping and trade based on the Northern Sea Route, and provide references for China on participating in the construction of the Northern Sea Route, exploiting and utilizing Arctic resources, and reinforcing the trade between China and Europe.

Due to the rapid development of society and economy, China's demand for energy and mineral resources is increasing day by day. Therefore, China has carried out a lot of energy trade with Russia, a country with adequate resources. Under the background of global warming and the gradual improvement of Arctic navigation, the energy transportation between the ports of the two countries can be completed through the northeast passage, which will be better than the traditional passage in terms of time, cost, and security. In this paper, the weighted average travel time was used to quantify the accessibility from Chinese ports to Russian oil and gas resources from 2030 to 2070 under climate change scenarios, and a shipping cost system was established to calculate the navigation cost. The conclusions are as follows: (1) The accessibility of Chinese ports to Russian oil resources will be better than that to Russian gas resources. (2) The accessibility of Chinese ports to Russian resources will be reduced by 7 hours on average every decade, and the accessibility of Nantong Port to Russian resources will be the best. (3) The navigation cost of Chinese ports will be reduced by $5000 on average every decade, and the cost of the route from Nantong Port will be the lowest. (4) Under the high emission concentration scenario, merchant shipping will cover a wide range in the future. This paper quantified and evaluated the time and cost of energy trade between China and Russia from 2030 to 2070, which provided a theoretical reference for Sino-Russian maritime transportation and energy trade.