Current Trend of Carbon Emissions from Wildfires in Siberia

Accelerated rise in wildfire carbon emissions from Arctic continuous permafrost

Wildfires over permafrost put perennially frozen carbon at risk. However, wildfire emissions from biomass burning over the diverse range of permafrost regions and their share in global wildfire emissions have not been revealed. The results showed a dramatic increase in wildfire carbon emissions from permafrost regions over the period 1997-2021. The share of permafrost in global wildfire CO2 emissions increased from 2.42% in 1997 to 20.86% in 2021. Accelerating wildfire emissions from continuous permafrost region is the single largest contributor to increased emissions in northern permafrost regions. Fire-induced emissions from 2019 to 2021 alone accounted for approximately 40% of the 25-year total CO2 emissions from continuous permafrost regions. The rise in wildfire emissions from continuous permafrost regions is explained by desiccation within a 5-10 cm soil depth, where wildfires combust belowground fuel. These findings highlight the acceleration of fire-induced carbon emissions from continuous permafrost regions, which disturb the organic carbon stock and accelerate the positive feedback between permafrost degradation and climate warming, thus stimulating permafrost towards a climatic tipping point.

Rapid summer Russian Arctic sea-ice loss enhances the risk of recent Eastern Siberian wildfires

In recent decades boreal wildfires have occurred frequently over eastern Siberia, leading to increased emissions of carbon dioxide and pollutants. However, it is unclear what factors have contributed to recent increases in these wildfires. Here, using the data we show that background eastern Siberian Arctic warming (BAW) related to summer Russian Arctic sea-ice decline accounts for ~79% of the increase in summer vapor pressure deficit (VPD) that controls wildfires over eastern Siberia over 2004-2021 with the remaining ~21% related to internal atmospheric variability associated with changes in Siberian blocking events. We further demonstrate that Siberian blocking events are occurring at higher latitudes, are more persistent and have larger zonal scales and slower decay due to smaller meridional potential vorticity gradients caused by stronger BAW under lower sea-ice. These changes lead to more persistent, widespread and intense high-latitude warming and VPD, thus contributing to recent increases in eastern Siberian high-latitude wildfires.

Synoptic weather patterns during fire spread events in Siberia

Several recent studies have indicated a strong relationship between extensive wildfires in Siberia and synoptic-scale weather processes. In this study, we used the concept of fire spread events to investigate the relationships between synoptic and surface-level weather conditions and extensive wildfires in Siberia during 2001-2022 using the MODIS and ERA5 reanalysis products. We analyzed the spatio-temporal features and seasonality of fire spread events in the region and found that most of them occurred in the central part of Eastern Siberia (ES) during the summer months, following the wildfire season in the region. A significant positive trend in the annual count of fire spread events was found in ES, coinciding with non-significant negative trends in cloud cover and precipitation and non-significant positive trends in air temperature and the fire weather index. Results show that in the ES region, which accounts for 46 % of the total number of considered events, the main driver of fire spread events is the formation of a positive geopotential height anomaly, which, based on the pattern of the meridional wind component, indicates the presence of an anticyclone above the area of fire spread events. The presence of a high-pressure zone causes a decrease in cloud cover over regions with fires, leading to increases in the amount of incoming solar radiation and surface air temperature and a decrease in precipitation. These conditions contribute to the drying of fuel and an increase in the overall fire hazard level, which in turn leads to an intensification of the combustion process, as evidenced by an increase in the radiative power of fires.

Possible enhancement in ocean productivity associated with wildfire-derived nutrient and black carbon deposition in the Arctic Ocean in 2019-2021

The Arctic is severely affected by climate change and various forms of environmental pollution. Enriched with nutrients and light-absorbing compounds, the wildfire plume has the potential to affect biological carbon fixation and sequestration within the Arctic Ocean. In this study, we utilized satellite-derived oceanic data (phytoplankton and sea ice) and atmospheric reanalysis products (black carbon, BC, indicative of wildfire impact) to evaluate the effect of the pronounced increase in wildfires from 2019 to 2021 on the East Siberian Sea. During these years, chlorophyll-a levels rose by ∼213 % compared to the previous decadal average, which had notably lower wildfire activities. This increase in chlorophyll-a is attributable to the deposition of nitrogen from the wildfire plume. Concurrently, the period required for sea ice concentration to decrease by 25 % was on average ∼ 10 days shorter than usual. This suggests that BC-induced acceleration of sea ice melting might extend the growing season for phytoplankton.

What happens to biomass burning-emitted particles in the ocean? A laboratory experimental approach based on their tracers

Wildfires, controlled burns, and biofuel combustion (biomass burning or BB) are major contributors to particulate matter in the atmosphere and thus have an impact on climate, human health, and ecosystems. Once emitted, the particulate matter derived from BB can be taken up by the oceans. However, the fate and impact of BB in the marine biological carbon pump, and carbon cycle are largely unknown. This work presents the first attempt to investigate the bioavailability of two BB tracers, levoglucosan and galactosan, in seawater inoculated with marine prokaryotes. Levoglucosan and galactosan were incubated with a marine bacterial inoculum and monitored for six weeks under controlled laboratory conditions. Along with the anhydrosugar concentrations, multiple chemical and biological parameters were monitored over time. The results indicate that levoglucosan and galactosan can be assimilated by marine prokaryotes as their concentrations decreased by 97 ± 4 % and 36 ± 21 % (n = 3) of their initial values. However, this decrease occurred only after a 9 and 15 days from the beginning of the experiment, respectively. The decrease in the levoglucosan and galactosan concentrations was accompanied by an increase in both heterotrophic prokaryotic production, and abundance. These results demonstrate that these anhydrosugars have the potential to be assimilated by heterotrophic prokaryotes and thus contribute to the microbial food web functioning. Under our experimental conditions, levoglucosan exhibited a bacterial growth efficiency of 17 ± 5 % (n = 3), suggesting that most of the levoglucosan is mineralized into CO2. Prokaryotic diversity analyses revealed the predominance of a few bacterial genera from the Roseobacter clade that were selected after the addition of the anhydrosugars. The presence of this widespread marine bacterial clade reflects its ability to process semilabile compounds (here levoglucosan and galactosan) originating from BB and contribute to the dissolved organic matter pool in surface seawaters.

Holocene wildfire and vegetation dynamics in Central Yakutia, Siberia, reconstructed from lake-sediment proxies

Wildfires play an essential role in the ecology of boreal forests. In eastern Siberia, fire activity has been increasing in recent years, challenging the livelihoods of local communities. Intensifying fire regimes also increase disturbance pressure on the boreal forests, which currently protect the permafrost beneath from accelerated degradation. However, long-term relationships between changes in fire regime and forest structure remain largely unknown. We assess past fire-vegetation feedbacks using sedimentary proxy records from Lake Satagay, Central Yakutia, Siberia, covering the past c. 10,800 years. Results from macroscopic and microscopic charcoal analyses indicate high amounts of burnt biomass during the Early Holocene, and that the present-day, low-severity surface fire regime has been in place since c. 4,500 years before present. A pollen-based quantitative reconstruction of vegetation cover and a terrestrial plant record based on sedimentary ancient DNA metabarcoding suggest a pronounced shift in forest structure toward the Late Holocene. Whereas the Early Holocene was characterized by postglacial open larch-birch woodlands, forest structure changed toward the modern, mixed larch-dominated closed-canopy forest during the Mid-Holocene. We propose a potential relationship between open woodlands and high amounts of burnt biomass, as well as a mediating effect of dense larch forest on the climate-driven intensification of fire regimes. Considering the anticipated increase in forest disturbances (droughts, insect invasions, and wildfires), higher tree mortality may force the modern state of the forest to shift toward an open woodland state comparable to the Early Holocene. Such a shift in forest structure may result in a positive feedback on currently intensifying wildfires. These new long-term data improve our understanding of millennial-scale fire regime changes and their relationships to changes of vegetation in Central Yakutia, where the local population is already being confronted with intensifying wildfire seasons.

Climate change, fire return intervals and the growing risk of permanent forest loss in boreal Eurasia

Climate change has driven an increase in the frequency and severity of fires in Eurasian boreal forests. A growing number of field studies have linked the change in fire regime to post-fire recruitment failure and permanent forest loss. In this study we used four burned area and two forest loss datasets to calculate the landscape-scale fire return interval (FRI) and associated risk of permanent forest loss. We then used machine learning to predict how the FRI will change under a high emissions scenario (SSP3-7.0) by the end of the century. We found that there are currently 133,000 km² forest at high, or extreme, risk of fire-induced forest loss, with a further 3 M km² at risk by the end of the century. This has the potential to degrade or destroy some of the largest remaining intact forests in the world, negatively impact the health and economic wellbeing of people living in the region, as well as accelerate global climate change.

Optical Characterization of Fresh and Photochemically Aged Aerosols Emitted from Laboratory Siberian Peat Burning

Carbonaceous aerosols emitted from biomass burning influence radiative forcing and climate change. Of particular interest are emissions from high-latitude peat burning because amplified climate change makes the large carbon mass stored in these peatlands more susceptible to wildfires and their emission can affect cryosphere albedo and air quality after undergoing transport. We combusted Siberian peat in a laboratory biomass-burning facility and characterized the optical properties of freshly emitted combustion aerosols and those photochemically aged in an oxidation flow reactor (OFR) with a three-wavelength photoacoustic instrument. Total particle count increased with aging by a factor of 6 to 11 while the total particle volume either changed little (<8%) for 19 and 44 days of equivalent aging and increased by 88% for 61 days of equivalent aging. The aerosol single-scattering albedo (SSA) of both fresh and aged aerosol increased with the increasing wavelength. The largest changes in SSA due to OFR aging were observed at the shortest of the three wavelengths (i.e., at 405 nm) where SSA increased by less than ~2.4% for 19 and 44 days of aging. These changes were due to a decrease in the absorption coefficients by ~45%, with the effect on SSA somewhat reduced by a concurrent decrease in the scattering coefficients by 20 to 25%. For 61 days of aging, we observed very little change in SSA, namely an increase of 0.31% that was caused a ~56% increase in the absorption coefficients that was more than balanced by a somewhat larger (~71%) increase in the scattering coefficients. These large increases in the absorption and scattering coefficients for aging at 7 V are at least qualitatively consistent with the large increase in the particle volume (~88%). Overall, aging shifted the absorption toward longer wavelengths and decreased the absorption Ångström exponents, which ranged from ~5 to 9. Complex refractive index retrieval yielded real and imaginary parts that increased and decreased, respectively, with the increasing wavelength. The 405 nm real parts first increased and then decreased and imaginary parts decreased during aging, with little change at other wavelengths.

Atmospheric Deposition on the Southwest Coast of the Southern Basin of Lake Baikal

A precipitation monitoring station in Listvyanka was set up to determine the potential impact of the coastal area on the state of the adjacent air environment above Lake Baikal on its southwest coast. This article presents the results of studying the chemical composition of atmospheric deposition (aerosols and precipitation) at this station in 2020, and of their comparison with the data from previous years (from 2000 to 2019). In 2020, the ionic composition of atmospheric aerosols and precipitation had changed compared to previous years. In the modern period, the total amount of ions in aerosols, accounting for 0.46 ± 0.40 μg∙m−3, was lower by an order of magnitude than between 2000 and 2004. The average annual total amount of ions in precipitation in Listvyanka was almost unchanged from the average values in 2000–2010 and was 10% lower than that from 2011 to 2019 (7.3 mg/L). The ratio of major ions of sulphates and ammonium changed in the aerosol composition: compared to the period from 2000 to 2004, in 2020, the contribution of ammonium ions had decreased significantly, from 32% to 24%; the contribution of sulphates had increased to 43%, and the contribution of calcium had increased from 8 to 13%. Since 2010, the contribution of K+ ions has increased to 8–10%, indicating the effect of smoke aerosols from wildfires. In precipitation, despite the dominance of sulphates (26%) and calcium (18%) throughout the year, the contribution of nitrates increases to 19% during the cold season (from October to March), while the contribution of ammonium ions and hydrogen ions increases to 13% and 17%, respectively, in the warm season (from April to September). In 2020, as in previous research years, the acidity of precipitation at the Listvyanka station was elevated (pH 5.1 ± 0.5); 50% of precipitation in 2020 had pH ˂ 5. We quantified ions in atmospheric aerosols and precipitation on the underlying surface of the coastal southwestern part of Lake Baikal. Ion fluxes with precipitation were the highest in the warm season, which corresponds to the annual maximum precipitation. Unlike previous years (from 2000 to 2010 and from 2011 to 2019), wet deposition of most ions—especially calcium, ammonium and nitrates—had decreased in 2020. There was a 35-fold decrease in nitrogen fluxes and a 5-fold decrease in sulphur fluxes in aerosols, as well as 1.6-fold and 1.3-fold decreases, respectively, in precipitation.

Long Term Monitoring and Connection between Topography and Cloud Cover Distribution in Serbia

The use of weather satellite recordings has been growing rapidly over the last three decades. Determining the patterns between meteorological and topographical features is an important scientific job. Cloud cover analysis and properties can be of the utmost significance for potential cloud seeding. Here, the analysis of the cloud properties was conducted by means of Moderate Resolution Imaging Spectroradiometer (MODIS) satellite recordings. The resolution of used data was 1 km2 within the period of 30 years (1989–2019). This research showed moderate changing of cloudiness in the territory of Serbia with a high cloudiness in February, followed by cloudiness in January and November. For the past three decades, May has been the month with the highest cloudiness. The regions in the east and south-west, and particularly in the west, have a high absolute cloudiness, which is connected with the high elevation of the country. By means of long term monitoring, the whole territory of Serbia was analyzed for the first time, in terms of cloudiness. Apart from the statistical and numerical results obtained, this research showed a connection between relief and clouds, especially in the winter season. Linear regression MK (Mann-Kendall test) has proven this theory right, connecting high elevation sides with high absolute cloudiness through the year.