We analyze ground temperatures measured daily at depths of 0-10 m in the Nadym region, north-west Siberia (65 18 0 N, 72 6 0 E). Nadym is located within the discontinuous permafrost zone and the forest-tundra transition subzone, thus representing an area threatened by permafrost thawing. Soil comprises a 0.4-1.0-m-thick topmost layer of peat with high porosity (~0.9), underlain by layers of mineral soil (sand, clay, loam) with lower porosities of 0.3-0.4. With a numerical heat transfer model, we provide predictions of general permafrost development for the next 300 years. Furthermore, we apply the model with the same time frame, to predict permafrost evolution in two monitoring boreholes (BH) in the Nadym area, BH 1-09 and 3-09 with present (2012-2016) temperatures at the top of the permafrost (TTOP) of −2.0 and 0.0 C, respectively. Applying a mild warming trend (0.02 C/yr in mean annual air temperature [MAAT], corresponding to the IPCC representative concentration pathway trend RCP 2.6) does not lead to thawing of permafrost during the applied 300 years of simulation time in BH 1-09, whereas in BH 3-09 thawing has already begun. Applying a strong warming trend of 0.05 C/yr in MAAT (corresponding to RCP 8.5) leads to gradual thawing of permafrost in both boreholes. K E Y W O R D S climate change, freezing and thawing indices, Nadym, permafrost, temperature, thermal modeling, West Siberia

In 2016, an outbreak of anthrax killing thousands of reindeer and affecting dozens of humans occurred on the Yamal peninsula, Northwest Siberia, after 70 years of epidemiological situation without outbreaks. The trigger of the outbreak has been ascribed to the activation of spores due to permafrost thaw that was accelerated during the summer heat wave. The focus of our study is on the dynamics of local environmental factors in connection with the observed anthrax revival. We show that permafrost was thawing rapidly for already 6 years before the outbreak. During 2011–2016, relatively warm years were followed by cold years with a thick snow cover, preventing freezing of the soil. Furthermore, the spread of anthrax was likely intensified by an extremely dry summer of 2016. Concurrent with the long-term decreasing trend in the regional annual precipitation, the rainfall in July 2016 was less than 10% of its 30-year mean value. We conclude that epidemiological situation of anthrax in the previously contaminated Arctic regions requires monitoring of climatic factors such as warming and precipitation extremes.

Abstract. The Pan-Eurasian Experiment (PEEX) Science Plan, released in 2015, addressed a need for a holistic system understanding and outlined the most urgent research needs for the rapidly changing Arctic-boreal region. Air quality in China, together with the long-range transport of atmospheric pollutants, was also indicated as one of the most crucial topics of the research agenda. These two geographical regions, the northern Eurasian Arctic-boreal region and China, especially the megacities in China, were identified as a “PEEX region”. It is also important to recognize that the PEEX geographical region is an area where science-based policy actions would have significant impacts on the global climate. This paper summarizes results obtained during the last 5 years in the northern Eurasian region, together with recent observations of the air quality in the urban environments in China, in the context of the PEEX programme. The main regions of interest are the Russian Arctic, northern Eurasian boreal forests (Siberia) and peatlands, and the megacities in China. We frame our analysis against research themes introduced in the PEEX Science Plan in 2015. We summarize recent progress towards an enhanced holistic understanding of the land–atmosphere–ocean systems feedbacks. We conclude that although the scientific knowledge in these regions has increased, the new results are in many cases insufficient, and there are still gaps in our understanding of large-scale climate–Earth surface interactions and feedbacks. This arises from limitations in research infrastructures, especially the lack of coordinated, continuous and comprehensive in situ observations of the study region as well as integrative data analyses, hindering a comprehensive system analysis. The fast-changing environment and ecosystem changes driven by climate change, socio-economic activities like the China Silk Road Initiative, and the global trends like urbanization further complicate such analyses. We recognize new topics with an increasing importance in the near future, especially “the enhancing biological sequestration capacity of greenhouse gases into forests and soils to mitigate climate change” and the “socio-economic development to tackle air quality issues”.

<p>Anthrax is a bacterial disease affecting mainly livestock but also posing a risk for humans. During the outbreak of anthrax on Yamal peninsula in 2016, 36 humans were infected and more than 2.5 thousand reindeer died or were killed to prevent further contamination [1]. Anthrax is a natural focal disease, which means that its agents depend on climatic conditions. The revival of bacteria in previously epidemiologically stable region was attributed to thawing permafrost, intensified during the heat wave of 2016. We studied recent dynamics of air temperature as well as summer and winter precipitation in the region. In addition, we analysed the effect of winter precipitation and air temperature on the dynamics of active layer thickness using data from Circumpolar Active Layer Monitoring sites [2]. Our analysis suggests that permafrost was thawing intensively during several years before the outbreak, when snowy cold winters followed warmer winters. Thick snow prevented soil from freezing and enhanced permafrost thawing. In addition, we showed that summer precipitation drastically decreased in the region of outbreak during recent years, likely contributing to the spread of disease.  </p><p>[1] Popova, A.Yu. et al. Outbreak of Anthrax in the Yamalo-Nenets Autonomous District in 2016, Epidemiological Peculiarities. Problemy Osobo Opasnykh Infektsii [Problems of Particularly Dangerous Infections]. <strong>4</strong>, 42–46 (2016).</p><p>[2] Circumpolar Active Layer Monitoring site: https://www2.gwu.edu/~calm/ [2/08/2019].</p>

<p>The rate of climate warming in North-West Siberia is among the highest in the world and this trend is especially pronounced in summer [1]. Analysis of permafrost thermal conditions in this area provides plausible scenarios of permafrost degradation also elsewhere. An increase in the summer mean temperature together with the prolongation of the warm season results in the increase of the thawing degree-days enhancing thawing of permafrost. Here we present the results of decadal temperature observations from three boreholes near Nadym, North-West Siberia. We further use the results and the observed cryolithological structure of soils in two boreholes to model the long-term evolution of the deep permafrost under two climate scenarios, RCP2.6 (climate action, fast reduction of CO<sub>2 </sub>emissions) and RCP8.5 (‘business as usual’). Both borehole sites have a topmost high-porosity, high-ice content layer of peat which helps prolonging the degradation. The main difference between the boreholes is snow cover resulting from the difference of borehole positions (one is located on the top of the hill). Our results suggest that under RCP8.5 scenario permafrost will degrade in both boreholes. On the contrary, under RCP2.6 scenario permafrost will degrade in one borehole with the deeper snow cover, where it already shows the signs of degradation. For the other borehole, the model predicts that permafrost will not degrade within the next 300 years, although the permafrost temperatures are eventually above -1°C.</p><p>[1] Frey K.E. & Smith L.C. Recent temperature and precipitation increases in West Siberia and their association with the Arctic Oscillation. Polar Research <strong>22(2)</strong>, 287–300 (2003).</p>