Siberian Arctic Research Articles

Extending the knowledge of taxonomy, biodiversity, and biogeography of Arctic ichthyofauna: A case study of the most diverse genus Lycodes (Zoarcidae)

Eelpout genus Lycodes (Zoarcidae) is the most species-rich genus of fishes in the Arctic seas. The species composition and the actual ranges of some Arctic eelpouts are still questionable due to insufficient research efforts and often incorrect species identifications. A new material on 12 species of eelpout genus Lycodes was collected during 2019 research cruise in four seas of Siberian Arctic (western Chukchi, East Siberian, Laptev, and Kara seas). The morphological characters, variability and distribution of these species are described and discussed. Four species are discovered in new areas, i.e. L. reticulatus were for the first time reported for the East Siberian Sea, L. pallidus for the Chukchi Sea, L. raridens for the Laptev Sea, and L. rossi in the Chukchi and East Siberian seas. These records significantly extend our knowledge on the modern ranges of these species, and may testify to the expansion of Pacific species into the Arctic. Results obtained show that L. pallidus and L. polaris might be the most abundant and widespread species occurred in three Siberian Arctic seas, while former species is characterized by the the widest range of morphological variability. A data presented contribute to monitoring of the biodiversity of Arctic ecosystems that are transforming rapidly in the face of climate change and increasing anthropogenic pressure.

Sources and Fates of Sedimentary Polycyclic Aromatic Hydrocarbons in the East Siberian Arctic Shelf: Implications for Input Pathways and Black Carbon Constraint

AbstractThe Arctic region is experiencing more rapid climate changes than the other parts of the world and serves as a sink for semi‐volatile persistent organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs), which can be utilized as molecular markers for pyrogenic carbon, such as black carbon (BC). As the sea ice retreats and increased terrestrial inputs with widespread wildfires, the PAH concentrations in the Arctic Ocean are rising. In this study, the sources and fates of PAHs together with BC in surface sediments from the East Siberian Arctic Shelf (ESAS) were analyzed. Positive matrix factorization (PMF) elucidated a mixed petrogenic and pyrogenic sources and distinct PAH fates associated with diverse input pathways including coastal permafrost erosion contribution (∼30%), petrogenic‐related emission (∼34%), fossil fuel combustion (∼26%), and biomass burning (∼10%). Correlation analysis indicated that BC plays a key role in affecting the behavior and fates of PAHs. In the Chukchi Sea, PAHs are closely associated with soot‐BC, whereas in the Laptev Sea (LS) and west East Siberian Sea (W‐ESS), they exhibit a coupling process with char‐BC. The presence of these carbonaceous materials in the sediments of CS is likely influenced by atmospheric deposition and biological activity, whereas the LS and W‐ESS regions are mainly affected by long‐distance river transport and direct deposition from coastal permafrost. As global warming continues, permafrost thawing induces the remobilization and retranslocation of PAHs, thereby becoming a significant PAH contributor and input pathway in the rapidly changing Arctic coastal margin.

Relationship between Respiration Rate and Body Weight in Arctic Copepods at Subzero Temperature

Dependence of the respiration rate (R) on the animal’s weight (W) is described by the equation R = a Wb, where the exponential coefficient b is usually taken equal to ¾. However, several authors indicate that the value of the coefficient b may vary with temperature changes as well as during ontogeny. In the Arctic seas, copepods spend most of their lives at temperature below or close to zero. Meanwhile, there are very few measurements of respiration rate at temperatures ≤ 0°C, which does not allow us to estimate the overall R(W) dependence at these temperatures. The work was carried out in three cruises of the R/V “Akademik Mstislav Keldysh” in the Siberian Arctic seas in 2018–2020. Copepods caught from the sea were adapted to experimental temperature and placed in tightly capped vials filled with filtered sea water for 24 h. The oxygen concentration was measured with a fiber-optic oxygen probe. The results of 120 measurements of respiration rate and 111 measurements of body carbon in five species of copepods at a temperature of -1.5°C are presented. The obtained relationship between body carbon content (W) and the prosome length (L) was described by the equation W = 6.982 L3.221, and the dependence of respiration on body weight was described by the equation R = 0.077 W0.753. No effect of a subzero temperature on the coefficient b was found. The regression parameters of R(W) did not change with the ontogenetic development of Calanus glacialis.

Terrestrial input and biological processes drive varying mineral/organic matrix-related mercury sequestration and deposition in the East Siberian Arctic Shelf

Thawing Arctic permafrost is releasing massive amounts of terrestrial mercury (Hg) into the Arctic shelf, which is expected to form a Hg sink in sediments. Here we analyzed the coupling roles of terrestrial input and biological processes in varying mineral/organic matrix-related Hg sequestration and deposition on the East Siberian Arctic shelf (ESAS), using Pearson and partial correlation analysis. Results show that the occurrence of Hg in the Laptev Sea under the Lena River-dominated input exhibits strong correlations with the organic carbon (OC) content and sediment specific surface area. This indicates that the prolonged riverine loading processes facilitate Hg sequestration by organic/mineral matrices and these land-derived mineral-OC-Hg complexes remain stable during cross-shelf transportation. By contrast, the comparative samples with coastal erosion-dominated Hg input in the western East Siberian Sea shows limited Hg complexation, primarily due to the absence of regulation by riverine processes and/or the high sedimentation rates. The correlations between Hg and OC source proxies (δ13C and lignin) indicate that these matrix-free Hg could be more readily sequestrated by the marine OC, which facilitates its deposition via the biological pump. While unexpectedly low Hg abundance in the Chukchi Sea may indicate that the effective biological scavenging of Hg sequestration could be constrained by insufficient terrestrial Hg input. Our findings of the matrix-related Hg sequestration by mineral and/or OC association in this study may shed light on the biogeochemical cycle of Hg in the Arctic aquatic regime, which could reduce the methylmercury formation in water column, and the methylation within sediments needs further exploration.

Carbon and oxygen isotopes in mummified wood reveal warmer and wetter winters in the Siberian Arctic 3000 years ago

Paleoclimate reconstructions from the Holocene are important for defining baseline conditions in order to interpret and contextualize the effects of modern climate change. Such records are particularly lacking for Siberia, a region that represents ~ 50% of the Arctic. In addition, the majority of proxy-based paleoclimate reconstructions for the Holocene represent mean annual conditions, and few quantify winter temperature, which is particularly important for predicting the effects of global warming in Arctic environments. Here we provide the first quantitative proxy reconstruction of precipitation and temperature for both summer and winter for 3000 years ago via novel high-resolution intra-annual carbon and oxygen isotope measurements across annual growth rings of fossil wood mummified within the permafrost of far northeastern Siberia. We found that the site experienced greater precipitation year-round (~ 10% increase in summer and ~ 30% increase in winter), cooler summer temperatures, and warmer winter temperatures, compared with today. Our findings indicate that warmer winter temperatures (+ 3.0 °C above early twentieth century values) in the Arctic 3000 years ago drove higher mean annual temperature by up to 1 °C, despite the existence of cooler summers, a similar phenomenon to what is observed within today’s Arctic environments, and past intervals of extreme global warmth.

Bioaccumulation of Chemical Elements and Organic Carbon in the Macrozoobenthic Organisms of the Laptev Sea

Within the framework of the program “Marine Ecosystems of the Siberian Arctic”, based on the materials collected during the 69th and 72nd cruises of the R/V “Akademik Mstislav Keldysh”, a study of the distribution of a group of chemical elements (As, Ba, Bi, Co, Cr, Cr, Cd, Co, Cu, Cr, Mn, Ni, Pb, Sc, Ti, Tl, Th, V, U and Zn) and organic carbon in the mass taxa of the Laptev Sea macrozoobenthos in the fields of methane seepage and outside them was carried out. For the first time, the bioaccumulation potential (BP) was quantified, taking into account, along with the concentration of elements in organisms, their biomass. At the C-15 methane field, the population of brittle stars accumulates each of the microelements many times (up to 40 times) more than at the background station. Brittle stars and bivalves show increased BP for Ni, As, Ba, Cu, Ti, V, Mn, and Zn compared to other elements, with brittle stars having significantly higher BP. It is assumed that the increased bioaccumulation of some heavy metals and metalloids in methane seep areas is associated with a greater bioavailability of organic matter in bottom sediments. For organic carbon, the highest BP was established, which is especially expressed in the C-15 methane field. At the background station, taxa accumulate a significantly smaller (by a factor of 10) amount of carbon in their biomass. As a result of the functioning of the ground eaters, bottom sediments are enriched with organic carbon, which may indicate an important contribution of benthic organisms to the carbon cycle in the seas of the Arctic.

A unique warm–water oasis in the Siberian Arctic’s Chaun Bay sustained by hydrothermal groundwater discharge

Chaun Bay, located on the fringe of the East Siberian Sea, has been described since the mid-20th century to support a unique marine ecosystem that is atypical for the local Siberian Arctic. Here we use ship-board physical, biogeochemical and geological measurements taken in October 2020, along with hydrographic observations taken from land-fast ice in April 2023, to demonstrate that these warm-water biological communities are supported by hydrothermal submarine groundwater discharge that delivers heat, salinity, nutrients, and trace elements to the bay. We identify a cyclonic eddy that mixes the warm nutrient-rich groundwater with oxygen-rich surface water, resulting in a water mass within Chaun Bay that has similar physical and chemical properties to the highly productive waters of the North Pacific and Southern Chukchi Sea. The bay showed elevated concentrations of chlorophyll-a and zooplankton, and the abundance and species diversity of epibenthos significantly exceeded values observed elsewhere in the East Siberian Sea. The benthic communities contained a number of boreal species that are not typically found in the Arctic Ocean. We also observed Thysanoessa krill populations, a pelagic species generally considered an expatriate in Arctic waters.

Different trends in the dynamics of Arctic lakes in North Siberia under climate change in 1985–2021

The methods and results of a comparative analysis of the effects of climate changes on the dynamics of the areas of thermokarst lakes over the past 36 years in the Arctic regions on the Yamal, Gydan, and Taimyr peninsulas are considered, the areas of which are 114, 175 and 426 thousand km2, respectively. All three regions are located within the permafrost zone of the Siberian Arctic. Using images of the Landsat 4, 5, 7, and 8 satellites, time series of data on average values of lake areas for the indicated regions were obtained on the basis on averaging areas of lakes over 23 test (key) areas. The total area of the test sites is about 800 km2. Using the ERA5 reanalysis system, time series of data on the mean annual air temperature in these territories have been generated, which show a rise of the temperature over the studied period 1985–2021. A comparison of trends in changes in regional mean areas of lakes and mean annual air temperature shows that with approximately the same rate of the temperature rise on these peninsulas, different trends in the dynamics of the lake areas are observed, which are manifested, on the one hand, in a noticeable reduction in the areas of lakes in the territories of Yamal and Gydan and, on the other hand, in their growth in Taimyr. Air temperature averaged over the period 1985–2021 and coefficients of the linear trend of changes in the lake areas in each of the above regions were compared. The results show that on the territories of Yamal and Gydan, where the lake areas decrease, the mean air temperature for the same period is equal to –8.1±0.9 and –8.9±0.9 °С, respectively. On the Taimyr territory, where the lake areas increase, the mean air temperature is significantly lower: –12.8±0.94 °С. Thus, this makes possible to make a conclusion that these considered regions differ significantly from each other by values of mean air temperature, and respectively, they are characterized by different trends in changes in areas of the thermokarst lakes.

Impact of gas arising from gas hydrate decomposition on the effective permeability of bottom sediments of the Arctic shelf: a laboratory simulation

Relevance. The necessity to investigate the mechanism of gas (methane) flow occurring during decomposition of gas hydrate formations within the layers of bottom sediments. This process is evident through substantial releases of methane bubbles in extensive shallow regions of the Russian Arctic shelf and has the potential to alter the equilibrium of atmospheric methane, a critical greenhouse gas. Aim. To quantitatively investigate, within the context of gas transport in bottom sediments, the impact of free and bound gas within the pores on the nonlinearity of filtration flows. Methods. The model samples with filtration properties similar to those of the bottom rocks of the East Siberian Arctic shelf. During the experiments, a specific amount of gas was injected into the saturated model sample, followed by the measurement of its effective permeability during a slow decrease in pore pressure gradient. The obtained curve was interpreted within the framework of the threshold gradient model. Results. The experiments yielded curves showing the dependency of the threshold gradient magnitude on gas saturation for several samples. It was found that the threshold gradient linearly increases with the growth in gas fraction within the pore space. Already at a gas fraction of approximately 0.02, this value in the experiments reached 0.01 MPa/m, corresponding to the hydrostatic pressure gradient in water. This suggests that even areas with relatively low gas saturation may be impermeable to convective fluid flow. This possibility should be considered when creating models for bubble gas transporting through the rock layers of bottom sediments. Furthermore, the existence of gas-saturated zones with threshold gradients can significantly impact the vertical profile of pore pressure and lead to a reassessment of the depth of gas hydrate stability zones.

Laptev Rift System Composite Tectono-Sedimentary Element, East Siberian Arctic

Abstract The Laptev Sea in the East Siberian Arctic is characterized by a system of extensional structures known as the Laptev Rift System (LRS), developed at the continental prolongation of an active divergent plate boundary - the Gakkel spreading ridge. The LRS hosts as much as 13–14 km of siliciclastic sedimentary strata of supposedly Late Cretaceous to Recent age. The strata accumulated atop of stretched and thinned continental crust that before the rifting onset was a complex tectonic juncture of Late Paleozoic/Early Mesozoic Taimyr and Late Mesozoic Verkhoyansk fold-and-thrust belts formed along the edges of the Siberian Palaeocontinent. In the context of this volume, the LRS is described as a composite tectono-sedimentary element that includes sedimentary rocks accumulated during pre-rift and syn-rift phases. The latter includes at least two syn-rift sedimentary cycles separated by a sedimentary succession formed during a stalled rift phase. In the absence of deep exploration wells, many aspects of the LRS geology and its petroleum prospects remain poorly constrained.

Ancient DNA reveals the origin and history of early dogs in northeastern China

Research has suggested that domestic dogs may have undergone simultaneous domestication in both the eastern and western parts of the Eurasian continent. Alternatively, domestication may have originated in the eastern part of Eurasia and subsequently spread westwards. The northeastern region of China, which serves as a link between the expansive Eurasian steppe and the northern regions of China, is of paramount importance for investigating the origin and domestication of dogs. To establish a precise spatiotemporal framework for the genetic history of ancient dogs in China, this study conducted mitochondrial genome analysis on 110 samples obtained from five archaeological sites in the northeastern region of China, spanning from the Neolithic period to the Bronze Age. This study reveals the developmental history of domestic dogs in the Northeast region, emphasizing the close connections between domestic dogs in Northeast China approximately 10,000 to 7000 years ago and ancient domestic dogs from the Siberian Arctic and the Americas. Furthermore, around 6000 years ago, domestic dogs from the Yangtze and Yellow River basins in China gradually spread to Northeast China, leading to the replacement of the original domestic dog haplotypes. These findings provide new insights into the early spread and diffusion of domestic dogs, as well as the origin and domestication of ancient dogs in China, contributing to a more comprehensive understanding of this phenomenon.

Ongoing borealization of Siberian Arctic marine ichthyofauna: Further evidence

The occurrence, abundance, biomass and size composition of six boreal fish species (walleye pollock Gadus chalcogrammus, Pacific cod G. macrocephalus, northern wolffish Anarhichas denticulatus, beaked redfish Sebastes mentella, Greenland halibut Reinhardtius hippoglossoides, glacier lanternfish Benthosema glaciale) in the Siberian and Pacific Arctic are presented based on the analysis of open databases (OBIS, GBIF and FishBase) and the results of scientific surveys of TINRO 1977–2020. In open databases, information on the records of these species is available mainly for the eastern Chukchi Sea and the Beaufort Sea and is practically absent for the seas of the Siberian Arctic, which is due to technical reasons. Data from long–term surveys of TINRO indicate the extension of the ranges of North Atlantic species eastward and North Pacific species westward indicating the ongoing borealization of the Siberian Arctic due to a changing climate. At the species level, it can lead to the overlap of the ranges of the “western” and “eastern” populations of Greenland halibut, as well as the ranges of Pacific and Greenland cods, which will make it possible to exchange genetic material between these populations/species and will contribute to the disappearance of genetic differences between them.

From the Berelekh ‘mammoth graveyard’ to Berelekh geo-archaeological complex: Paleoenvironment, site formation processes, and human-mammoth relationships

The Berelekh ‘mammoth graveyard’ is located on the Berelekh River in the NE Yana-Indighirka Lowland at 70° 30′ N and 144° 02′ E in the East Siberian Arctic. First studied in 1970, it was originally viewed as an example of a natural accumulation of mammoth remains in a periglacial landscape, although the discovery of associated archaeological remains indicated a human presence. New field research has yielded more data on stratigraphy, site formation processes, paleoenvironments, and age, allowing reassessment of the relationship between the mass accumulation of mammoth remains and archaeological site, which together constitute the Berelekh geo-archaeological complex (BGAC). The accumulation of mammoth bone spans 13,700–11,800 14C yr B.P., with respective peaks at 12,400, 12,200, and 11,800 14C yr B.P. The peaks fall within the Bølling-Allerød warming, represented in the Berelekh pollen record. Based on the taphonomy and dating of the BGAC, humans contributed to the formation of the bone-bed and procurement of mammoth was related to production of mammoth ivory technology. The dating of the mammoth bone accumulation coincides with the age of the archaeological site, indicating recurring but not permanent human occupation of the area. Based on IntCal20 calibration, the archaeological component of the Berelekh geo-archaeological complex dates to ∼14,000–13,500 calBP.

Increased summertime wildfire as a major driver of the clear-sky dimming in the Siberian Arctic from 2000 to 2020

A warming Arctic is expected to exacerbate wildfires in Siberia, potentially creating a critical feedback to the Arctic climate change. However, our understanding of these fire-climate interactions remains limited. This study investigated changes in East Siberian wildfires and their influence on fire emissions, aerosol optical depth (AOD), and the surface clear-sky insolation across the Siberian Arctic from 2000 to 2020 using satellite observations. Our analysis reveals a substantial increase in wildfires, with fire counts doubling (a 114% increase) and fire radiative power surging by 8.4 × 106 MW compared to the early 21st century. Over 93% of this increase occurred during the boreal summer months. These intensified wildfires led to a significant rise in aerosol emission (organic carbon, PM2.5, and black carbon) exceeding 75% in East Siberia. Consequently, fire-season AOD in the Siberian Arctic increased by 33% (6.0 × 10−2), with 85% (5.1 × 10−2) attributable to wildfire changes. The wildfire-associated increase in AOD resulted in enhanced clear-sky dimming of 4.1 ± 3.2 W m−2 across the Siberian Arctic from 2000 to 2020. These findings suggest a critical feedback mechanism: a warming Arctic drives increased wildfires in Siberia, which in turn significantly impact the Arctic surface radiative budget through enhanced clear-sky dimming. Future simulations and projections for the Arctic should prioritize incorporating the feedback effects of intensifying wildfires.

The roles of river discharge and sea ice melting in formation of freshened surface layers in the Kara, Laptev, and East Siberian seas

Wide areas of the Siberian Arctic shelf are covered by freshened surface water layers, which are among the largest in the World Ocean. River discharge is the main freshwater source for formation of these layers; therefore, they are commonly referred to as river plumes (the Ob-Yenisei plume in the Kara Sea and the Lena plume in the Laptev and East Siberian seas). The contribution of sea ice meltwater (SIM) to the Ob-Yenisei and Lena plumes is pointed out to be small, albeit its actual volume remains unknown. In this study, we use a novel dataset of satellite-derived sea ice thickness in the Arctic Ocean during the melt period to quantify the annual volume of SIM, which was received by the Ob-Yenisei and Lena plumes during 2012–2020. We reveal that SIM is a significant source for the Lena plume providing, on average, 20% of total annual freshwater content. Moreover, the share of SIM in the Lena plume shows large inter-annual (14%–29%) variability, i.e., during certain years, SIM provides almost one-third of freshwater volume of the Lena plume. This variability is governed by inter-annual variability of ice thickness, as well as seasonal variability of sea ice melting conditions. Conversely, the contribution of SIM to the Ob-Yenisei plume is relatively low (8% on average), and its total annual share varies from 6% to 11% during the study period. This difference is mainly caused by significantly smaller area of the Ob-Yenisei plume as compared with the Lena plume. The forecasted earlier onset of ice melting in the Arctic Ocean in future decades due to climate change could decrease the contribution of SIM to the Ob-Yenisei plume, whereas its influence on the Lena plume remains unclear.

Current and past climate co-shape community-level plant species richness in the Western Siberian Arctic.

The Arctic ecosystems and their species are exposed to amplified climate warming and, in some regions, to rapidly developing economic activities. This study assesses, models, and maps the geographic patterns of community-level plant species richness in the Western Siberian Arctic and estimates the relative impact of environmental and anthropogenic factors driving these patterns. With our study, we aim at contributing toward conservation efforts for Arctic plant diversity in the Western Siberian Arctic. Western Siberian Arctic, Russia. We investigated the relative importance of environmental and anthropogenic predictors of community-level plant species richness in the Western Siberian Arctic using macroecological models trained with an extensive geobotanical dataset. We included vascular plants, mosses and lichens in our analysis, as non-vascular plants substantially contribute to species richness and ecosystem functions in the Arctic. We found that the mean community-level plant species richness in this vast Arctic region does not decrease with increasing latitude. Instead, we identified an increase in species richness from South-West to North-East, which can be well explained by environmental factors. We found that paleoclimatic factors exhibit higher explained deviance compared to contemporary climate predictors, potentially indicating a lasting impact of ancient climate on tundra plant species richness. We also show that the existing protected areas cover only a small fraction of the regions with highest species richness. Our results reveal complex spatial patterns of community-level species richness in the Western Siberian Arctic. We show that climatic factors such as temperature (including paleotemperature) and precipitation are the main drivers of plant species richness in this area, and the role of relief is clearly secondary. We suggest that while community-level plant species richness is mostly driven by environmental factors, an improved spatial sampling will be needed to robustly and more precisely assess the impact of human activities on community-level species richness patterns. Our approach and results can be used to design conservation strategies and to investigate drivers of plant species richness in other arctic regions.

Primary production and microbial heterotrophy in the Siberian arctic seas, Bering Strait, and Gulf of Anadyr, Bering Sea

The data obtained during the recent decades indicate large-scale climatic changes in the Arctic Ocean, especially in the Siberian shelf seas. The impact of shrinking of the Arctic ice cover on marine net primary production (PP) was mostly studied using satellite-derived estimates of chlorophyll-a (Chl a), sea surface temperature, and sea ice concentrations, as well as various modeling approaches. However, no data are available on the quantitative relations between phytoplankton production and heterotrophic bacterioplankton activity in the broadest and shallowest shelf of the World Ocean - the East Siberian Arctic seas (ESAS). In this paper we present a full set of in situ measurements of main PP and microbial heterotrophy characteristics required for better understanding and further validation of the satellite and modeling approaches. In September–October 2011, during the 57th cruise of RV Akademik M.A. Lavrent'ev, PP, bacterioplankton abundance (BA) and bacterioplankton production (BP), as well the rates of dark CO2 assimilation (DCA) were determined in the Chukchi, East Siberian, and Laptev seas and in the Gulf of Anadyr of the Bering Sea (a total of 26 stations) by in situ measurements using radiolabeled bicarbonate. All three important production indicators exhibited significant variance within the studied water areas of the Arctic (РР from 0.98 to 54.7 μg C L−1 day−1), (ВР from 1.1 to 17.1 μg C L−1 day−1), and (DCA from 0.23 to 8.7 μg C L−1 day−1). The state of phyto- and bacterioplankton was determined by analysis of the BP/PP and DCA/PP ratios. Active photosynthesis with efficient incorporation of inorganic carbon into the biomass was observed in the Chukchi Sea coastal eastern waters and in the Gulf of Anadyr. On the contrary, the phytoplankton primary production was extremely low in oligotrophic basins of the East Siberian and Laptev seas, while the activity of heterotrophic bacterioplankton consuming organic matter of phytoplankton origin was relatively high. The data of direct measurements can be used for further adjustment of the indirect assessments of production obtained by satellite observations. Glossary East Siberian Arctic seas (ESAS), net primary production (PP), bacterioplankton abundance (BA), bacterial biomass (BB), bacterial production (BP), Arctic Ocean PP (AO-PP), organic matter (OM), dissolved organic matter (DOM), colored dissolved organic matter (CDOM), light CO2 assimilation (LCA), dark (heterotrophic + chemotrophic) CO2 assimilation (DCA), production indicators of the surface water layer (PPsurf, DCAsurf, BPsurf), estimated production indicators for the entire depth of the sea (PPint, DCAint, BPint; mg C m−2 day−1).

Sediment provenance of the East Siberian Arctic Shelf and evidence of Holocene climate-driven fluvial events in the Indigirka River based on detrital mineral analysis

Analysis of sediment provenance in the East Siberian Arctic Shelf is crucial for the understanding of source to sink pathways and their link to climatic and environmental changes. In this paper, we conducted detrital mineral analysis on surface sediments and one sedimentary core (LV77–41-1) from the eastern Laptev Sea and the western shelves of the East Siberian Sea. Based on the results of light and heavy mineral analysis in surface sediments, two distinct zones were identified in the eastern Laptev Sea: an eastern zone is characterized by sources from the Lena River and a northern zone is characterized by sources that transition from riverine dominance to more sea-ice transported sources in an offshore direction. In the western part of the East Siberian Sea, detrital mineral assemblages in the outer Indigirka River mouth region are influenced by polygenic sources comprising sediments mainly derived from the river itself, and some material supplied by the Siberian Coastal Current, and the erosion of coastal permafrost and nearby islands. In the outer shelf and basin region, detrital mineral assemblages contain signatures of apatite, garnet, and hypersthene, indicating various material sources are represented, including the Lena River, Taimyr Peninsula, and Kamchatka Peninsula. Integrating this understanding of the sources and transport pathways of surface sediments, detrital mineral analysis of core LV77–41-1 indicate that coarse-grained Holocene sediments were mainly transported by the Indigirka River, with subordinate sources from coastal permafrost erosion, materials carried by Siberian Coastal Current, and island erosion. Since 7 ka BP, four distinct fluvial events have occurred, with the most prominent fluvial event occurring between 4.6 and 4.3 ka when the depocenter shifted significantly toward the sea. The fluvial events occurred following the onset warm periods and the high frequency of volcanic glass observed in layers marking these fluvial events serves as evidence of the influx of glacial meltwater into the Indigirka River basin during these warmer episodes.

Manifestation of Gas Seepage from Bottom Sediments on the Sea Surface: Theoretical Model and Experimental Observations

The key area of the Arctic Ocean for atmospheric venting of CH4 is the East Siberian Arctic Shelf (ESAS). Leakage of methane through shallow ESAS waters needs to be considered in interactions between the biogeosphere and a warming Arctic climate. The development of remote sensing techniques for gas seepage detection and mapping is crucially needed for further applications in the ESAS and other areas of interest. Given the extent of the seepage areas and the magnitude of current and potential future emissions, new approaches are required to effectively, rapidly, and quantitatively survey the large seepage areas. Here, we consider the main features of gas seep detection on the sea surface in the characteristics of wind waves and radar signals. The kinematics of wave packets based on the kinetic equation for the spectral density of the wave action of surface waves is described. The results of a full-scale experiment on the remote radar observation of a model gas seep to the sea surface in the radar equipment signals are considered. The characteristic radar signatures of the gas seep in a wide range of hydrometeorological conditions, the parameters of which were recorded synchronously with the radar mapping, were determined. The results of the first radar observations of natural methane seeps on the ESAS are presented, and their radar contrasts are evaluated. The theoretical conclusions are in good qualitative agreement with the results of the model experiment and field studies and can be used for further research in aquatic areas with potential gas seepage, both of natural or anthropogenic origin, such as bubbling release from broken underwater gas pipelines.

Mass spectrometric analysis of unprecedented high levels of carbonaceous aerosol particles long-range transported from wildfires in the Siberian Arctic

Abstract. Wildfires in Siberia generate large amounts of aerosols, which may be transported over long distances and pose a threat to the sensitive ecosystem of the Arctic. Particulate matter (PM) of aged wildfire plumes originating from Yakutia in August 2021 was collected in Nadym and on Bely Island (both in northwestern Siberia). An advanced analysis of the chemical composition of aerosol particles was conducted through a multi-wavelength thermal–optical carbon analyzer (TOCA) coupled to resonance-enhanced multiphoton ionization time-of-flight mass spectrometry (REMPI-TOFMS) as well as through ultra-high-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS). In Nadym, concentrations of organic carbon (OC) and elemental carbon (EC) peaked at 100 and 40 µg m−3, respectively, associated with Angström absorption exponents for 405 and 808 nm (AAE405/808) between 1.5 and 3.3. The weekly average on Bely Island peaked at 8.9 µg m−3 of OC and 0.3 µg m−3 of EC and AAE405/808 close to unity. In particular, ambient aerosol in Nadym had a distinct biomass burning profile with pyrolysis products from carbohydrates, such as cellulose and hemicellulose, as well as lignin and resinoic acids. However, temporarily higher concentrations of five- and six-ring polycyclic aromatic hydrocarbons (PAHs), different from the PAH signature of biomass burning, suggest a contribution of regional gas flaring. FT-ICR MS with electrospray ionization (ESI) revealed a complex mixture of highly functionalized compounds, containing up to 20 oxygen atoms, as well as nitrogen- and sulfur-containing moieties. Concentrations of biomass burning markers on Bely Island were substantially lower than in Nadym, flanked by the appearance of unique compounds with higher oxygen content, higher molecular weight, and lower aromaticity. Back-trajectory analysis and satellite-derived aerosol optical depth suggested long-range transport of aerosol from the center of a Yakutian wildfire plume to Nadym and from the plume periphery to Bely Island. Owing to lower aerosol concentrations in the plume periphery than in its center, it is demonstrated how dilution affects the chemical plume composition during atmospheric aging.