Spring dust frequency in northeast Asia has been investigated using various approaches to understand the mechanisms of dust emission and transport. However, little attention has been paid to the linkage between dust activity and the Siberian High (SH), particularly when the SH pressure system is highly variable. In this study, we characterize the possible physical mechanisms of dust emission and transport associated with the Siberian High Intensity (SHI) and Siberian High Position Index (SHPI) in March using 18 years of ground-based observations and reanalysis data. We found that when the SHI was strong and the SH’s center was farther east (“Strong–East period”), surface and atmospheric temperatures were cooler than when the SHI was weak and the SH’s center was farther west (“Weak-West period”), due to anomalous anticyclonic pressure and strong easterlies. As a result, a reduction in the meridional temperature gradient in the lower atmosphere suppressed dust emission and transport, due to stagnant atmospheric conditions. This anomalous anticyclonic pressure in the Strong-East case seems to reduce the development of extratropical cyclones (ETC) in northeast Asia, leading to a less effective dust transport. A case study with composite analysis also showed a similar physical mechanism: stagnant air accompanying weakened westerlies in the Strong-East period suppressed dust transport to South Korea. Our findings reveal that the intensity and position of the SH can be utilized to identify spring transboundary air pollutants in northeast Asia.

Climate change impacts the characteristics of the vegetation carbon-uptake process in the northern Eurasian terrestrial ecosystem. However, the currently available direct CO₂ flux measurement datasets, particularly for central Siberia, are insufficient for understanding the current condition in the northern Eurasian carbon cycle. Here, we report daily and seasonal interannual variations in CO₂ fluxes and associated abiotic factors measured using eddy covariance in a coniferous forest and a bog near Zotino, Krasnoyarsk Krai, Russia, for April to early June, 2013–2017. Despite the snow not being completely melted, both ecosystems became weak net CO₂ sinks if the air temperature was warm enough for photosynthesis. The forest became a net CO₂ sink 7–16 days earlier than the bog. After the surface soil temperature exceeded ~1 °C, the ecosystems became persistent net CO₂ sinks. Net ecosystem productivity was highest in 2015 for both ecosystems because of the anomalously high air temperature in May compared with other years. Our findings demonstrate that long-term monitoring of flux measurements at the site level, particularly during winter and its transition to spring, is essential for understanding the responses of the northern Eurasian ecosystem to spring warming.

Spring and summer vegetation productivity in Siberia shows opposing responses to warmer spring. Spring warming causes excessive vegetation growth and earlier start of photosynthesis, enhancing productivity in spring. However, this leads to reduced productivity in the following season (i.e., summer) through soil moisture depletion. To understand how an exceptional spring heatwave (HW) affected ecosystem carbon uptake, we investigated the spatiotemporal cascade of gross primary production (GPP) and multiple climate variables over Siberia in 2020, using a satellite‐retrieved GPP product (GOSIF‐GPP) and the ERA5‐Land reanalysis data set for 2001–2020. Results showed a positive impact of anomalous spring warming on annual GPP (GPP_ann). GPP_ann from GOSIF‐GPP in West Siberia (55°–70°N, 50°–90°E) was enhanced by up to 10% above the 2001–2019 average despite continued dry conditions from May to August. In East Siberia (55–70°N, 90–130°E), the GPP increases for May and June were sufficient to compensate for marked reduction of GPP in July due to negative anomaly in radiation. In addition, the higher sensitivity of GPP_ann to spring temperature in West Siberia than in East Siberia suggests that GPP increase coupled with strong warming and respective excessive vegetation growth might be more pronounced in the western region, as observed in 2020. Our results indicate that the warming trend in spring, combined with possible extreme heat events, could elevate annual carbon uptake in Siberia, particularly in West Siberia. Further, this case study for the extreme HW event that occurred in 2020 can provide useful insight for understanding future change in carbon uptake over Siberia.

The transition winter-to-spring is essential for understanding the seasonal dynamics of CO2 flux in high northern latitudes. However, the latest CO2 flux measurements in the two dominant boreal ecosystems, i.e. coniferous forests and bogs are still insufficient. We investigated interannual variability of CO2 fluxes and their major drivers measured in a coniferous forest and a bog from 2013-2017 in Zotino, Russia. To better understand the controlling factors, we utilized the  Multivariate Adaptive Regression Splines (MARS) model. The two ecosystems showed clear differences in the timing of the start of CO2 uptake and CO2 flux rates before and after snowmelt. Both ecosystems started the net CO2 uptake even the snowmelt was incompleted. CO2 flux variations of coniferous forest were more sensitive to changes in air temperature than soil temperature than that of the bog. It is likely that intermittent frost events can reduce the magnitude of CO2 uptake rates of both ecosystems, however, CO2 uptake rates increased with a similar level as pre-frost within a few days. In 2015, both ecosystems reached the highest cumulative net ecosystem exchange of CO2 because of the unusually warm temperature in May compared to the study period. Our findings reveal that continuous and long-term monitoring of the effects of air and soil temperatures on vegetation productivity as well as their legacy effect in subarctic ecosystems required further to be studied.

Anomalous or extreme climate conditions in high northern latitudes are likely to become more frequent and intense for the last several years. Based on the eddy covariance flux data from 2013-2017 collected at a boreal forest and peatland in central Siberia, net CO2 uptake in spring 2015 was the highest compared with the 2013-2017 average because of the anomalous surface warming over the region > 60N. This enhanced spring net CO2 uptake may be associated with more snowfall amount in winter. However, an increased spring net CO2 uptake may be compensated with summertime net CO2 uptake due to the relatively cool summer surface temperature in 2015. Spring 2020 in central Siberia has experienced even more substantial surface warming than in spring 2015, probably associated with excessive spring snowmelt. This suggests that further investigations in the effects of anomalous seasonal climate and snow conditions on net CO2 uptake, photosynthesis and ecosystem respiration are necessary to better understand annual CO2 balance. To characterize carbon fluxes and underlying mechanisms related to climate condition and snow characteristics from 2012-2020, we analyzed upscaling carbon flux dataset based on a random forest model by Jing et al. (2021), satellite-based net ecosystem exchange of CO2 (i.e., Soil Moisture Active Passive (SMAP) L4 data), snow characteristics (e.g. freeze-thaw cycle, snow depth), and reanalysis dataset. We will focus on seasonal CO2 uptake, photosynthesis and ecosystem respiration under the anomalous temperature and snowfall/snowmelt conditions, then discuss factors regulating annual net CO2 uptake capacity in boreal forests and peatlands in central Siberia.