Space-time dynamics of carbon stocks and environmental parameters related to carbon dioxide emissions in the Buor-Khaya Bay of the Laptev Sea

This study aims to improve understanding of carbon cycling in the Buor-Khaya Bay (BKB) by studying the inter-annual, seasonal, and meso-scale variability of carbon stocks and related hydrological and biogeochemical parameters in the water, as well as factors controlling carbon dioxide (CO2) emission. Here we present data sets obtained on summer cruises and winter expeditions during 12 yr of investigation. Based on data analysis, we suggest that in the heterotrophic BKB area, coastal erosion and river discharge serve as predominant drivers of the organic carbon (OC) cycle, determining OC input and transformation, dynamics of nutrients, carbon stocks in the water column, and atmospheric emissions of CO2

Biogeochemical structure of the Laptev Sea in 2015-2020 associated with the River Lena plume

The discharge of rivers and the subsequent dispersion of their plumes play a pivotal role in the biogeochemical cycling of the Arctic Ocean. Based on the data collected during annual transects conducted in the autumn period (September-October) from 2015-2020, this study explores the effect of River Lena plume dispersion on the seasonal and interannual changes in the hydrophysical and biogeochemical structure of the southeastern Laptev Sea. The temperature-salinity relationship (T-S), Redfield ratio and multiparameter cluster analysis were used to investigate variations in the water mass structure along the transect. The results revealed that the plume’s interannual and seasonal spreading patterns play a crucial role in regulating the local physical, biogeochemical, and biological processes in the southern Laptev Sea. During September-October, the hydrochemical water mass structure along the transects shifted from highly stratified to unstratified as the plume’s mixing intensity increased. Anomalous hydrochemical distributions were observed due to coastal upwelling, which was primarily characterized by high total alkalinity and nitrate levels, and low organic phosphorus, nitrite, and ammonia levels in the seawater. Wind and cold weather conditions drive deep vertical mixing of seawater, causing the resuspension of bottom sediment and the subsequent enrichment of bottom water by nutrients. Multi-parameter cluster analysis is used to describe the details of water mass structures in the highly dynamic southern Laptev Sea, with water mass structures typically undergoing significant changes within two weeks between September and October. The migration and transformation of water masses throughout the seasons are influenced by the volume of river discharge, fall-winter cooling, and atmospheric circulation patterns. Furthermore, the general atmospheric circulation is confirmed to be the primary cause of the interannual variation in the spread of the Lena River plume over the southeast Laptev Sea.publishedVersio

Signatures of Molecular Unification and Progressive Oxidation Unfold in Dissolved Organic Matter of the Ob-Irtysh River System along Its Path to the Arctic Ocean

The Ob-Irtysh River system is the seventh-longest one in the world. Unlike the other Great Siberian rivers, it is only slightly impacted by the continuous permafrost in its low flow. Instead, it drains the Great Vasyugan mire, which is the world largest swamp, and receives huge load of the Irtysh waters which drain the populated lowlands of the East Siberian Plain. The central challenge of this paper is to understand the processes responsible for molecular transformations of natural organic matter (NOM) in the Ob-Irtysh river system along the South-North transect. For solving this task, the NOM was isolated from the water samples collected along the 3,000?km transect using solid-phase extraction. The NOM samples were further analyzed using high resolution mass spectrometry and optical spectroscopy. The obtained results have shown a distinct trend both in molecular composition and diversity of the NOM along the South-North transect: the largest diversity was observed in the Southern “swamp-wetland” stations. The samples were dominated with humic and lignin-like components, and enriched with aminosugars. After the Irtysh confluence, the molecular nature of NOM has changed drastically: it became much more oxidized and enriched with heterocyclic N-containing compounds. These molecular features are very different from the aliphatics-rich permafrost NOM. They witnesses much more conservative nature of the NOM discharged into the Arctic by the Ob-Irtysh river system. In general, drastic reduction in molecular diversity was observed in the northern stations located in the lower Ob flow

Biogeochemical structure of the Laptev Sea in 2015-2020 associated with the River Lena plume

The discharge of rivers and the subsequent dispersion of their plumes play a pivotal role in the biogeochemical cycling of the Arctic Ocean. Based on the data collected during annual transects conducted in the autumn period (September-October) from 2015-2020, this study explores the effect of River Lena plume dispersion on the seasonal and interannual changes in the hydrophysical and biogeochemical structure of the southeastern Laptev Sea. The temperature-salinity relationship (T-S), Redfield ratio and multiparameter cluster analysis were used to investigate variations in the water mass structure along the transect. The results revealed that the plume’s interannual and seasonal spreading patterns play a crucial role in regulating the local physical, biogeochemical, and biological processes in the southern Laptev Sea. During September-October, the hydrochemical water mass structure along the transects shifted from highly stratified to unstratified as the plume’s mixing intensity increased. Anomalous hydrochemical distributions were observed due to coastal upwelling, which was primarily characterized by high total alkalinity and nitrate levels, and low organic phosphorus, nitrite, and ammonia levels in the seawater. Wind and cold weather conditions drive deep vertical mixing of seawater, causing the resuspension of bottom sediment and the subsequent enrichment of bottom water by nutrients. Multi-parameter cluster analysis is used to describe the details of water mass structures in the highly dynamic southern Laptev Sea, with water mass structures typically undergoing significant changes within two weeks between September and October. The migration and transformation of water masses throughout the seasons are influenced by the volume of river discharge, fall-winter cooling, and atmospheric circulation patterns. Furthermore, the general atmospheric circulation is confirmed to be the primary cause of the interannual variation in the spread of the Lena River plume over the southeast Laptev Sea

Water Circulation, Temperature, Salinity, and pCO2 Distribution in the Surface Layer of the East Kamchatka Current

The ship-borne observations of the temperature, salinity, pCO2 (1995–2020) and satellite geostrophic velocity fields, SST, and chlorophyll concentration are used to identify the factors that determine the spatio-temporal variability of seawater parameters on the western boundary of the subarctic North Pacific. In winter, the surface layer of the East Kamchatka Current (EKC) was characterized by two types of water: the waters with a negative temperature (−1.0–−0.5 °C) and salinity of 32.4–32.9 and waters with a positive temperature (0.4–1.7 °C) and salinity of 33.0–33.1. The source of water with negative (positive) temperature and decreased (increased) salinity for the EKC zone is the Bering Sea shelf (Aleutian Basin). The surface waters in the eastern Kamchatka area in winter were close to gas equilibrium with the atmosphere or supersaturated with carbon dioxide (pCO2 = 380–460 µatm). In summer, extremely low pCO2 values (140–220 µatm) in the surface layer of the eastern Kamchatka and the northern Kuril Islands regions have been associated with the decreased salinity (32.1–32.6) of the waters. The distributions of the temperature, salinity, and pCO2 in the surface layer of the central Kuril Islands are determined by the location and intensity of the Kuril eddies and the EKC stream jets. The water mixing in the central Kuril Straits and the Kruzenshterna Bank area leads to increased salinity (33.2–33.4) and high values of pCO2 (480–670 µatm) in the surface layer of the EKC. The comparison of the pCO2 data collected in winter demonstrates an increase in pCO2 between 1998/2001 and 2018/2020 at about 50 µatm in the surface waters with a salinity of 33.0–33.1, which is in agreement with an increase in pCO2 in the atmosphere at 46 µatm (from 368 to 414 µatm) during this period

Water Circulation, Temperature, Salinity, and pCO₂ Distribution in the Surface Layer of the East Kamchatka Current

The ship-borne observations of the temperature, salinity, pCO2 (1995–2020) and satellite geostrophic velocity fields, SST, and chlorophyll concentration are used to identify the factors that determine the spatio-temporal variability of seawater parameters on the western boundary of the subarctic North Pacific. In winter, the surface layer of the East Kamchatka Current (EKC) was characterized by two types of water: the waters with a negative temperature (−1.0–−0.5 °C) and salinity of 32.4–32.9 and waters with a positive temperature (0.4–1.7 °C) and salinity of 33.0–33.1. The source of water with negative (positive) temperature and decreased (increased) salinity for the EKC zone is the Bering Sea shelf (Aleutian Basin). The surface waters in the eastern Kamchatka area in winter were close to gas equilibrium with the atmosphere or supersaturated with carbon dioxide (pCO2 = 380–460 µatm). In summer, extremely low pCO2 values (140–220 µatm) in the surface layer of the eastern Kamchatka and the northern Kuril Islands regions have been associated with the decreased salinity (32.1–32.6) of the waters. The distributions of the temperature, salinity, and pCO2 in the surface layer of the central Kuril Islands are determined by the location and intensity of the Kuril eddies and the EKC stream jets. The water mixing in the central Kuril Straits and the Kruzenshterna Bank area leads to increased salinity (33.2–33.4) and high values of pCO2 (480–670 µatm) in the surface layer of the EKC. The comparison of the pCO2 data collected in winter demonstrates an increase in pCO2 between 1998/2001 and 2018/2020 at about 50 µatm in the surface waters with a salinity of 33.0–33.1, which is in agreement with an increase in pCO2 in the atmosphere at 46 µatm (from 368 to 414 µatm) during this period

Space-time dynamics of carbon and environmental parameters related to carbon dioxide emissions in the Buor-Khaya Bay and adjacent part of the Laptev Sea

This study aims to improve understanding of carbon cycling in the Buor-Khaya Bay (BKB) and adjacent part of the Laptev Sea by studying the inter-annual, seasonal, and meso-scale variability of carbon and related hydrological and biogeochemical parameters in the water, as well as factors controlling carbon dioxide (CO₂) emission. Here we present data sets obtained on summer cruises and winter expeditions during 12 yr of investigation. Based on data analysis, we suggest that in the heterotrophic BKB area, input of terrestrially borne organic carbon (OC) varies seasonally and inter-annually and is largely determined by rates of coastal erosion and river discharge. Two different BKB sedimentation regimes were revealed: Type 1 (erosion accumulation) and Type 2 (accumulation). A Type 1 sedimentation regime occurs more often and is believed to be the quantitatively most important mechanism for suspended particular matter (SPM) and particulate organic carbon (POC) delivery to the BKB. The mean SPM concentration observed in the BKB under a Type 1 regime was one order of magnitude greater than the mean concentration of SPM (~ 20 mg L⁻¹) observed along the Lena River stream in summer 2003. Loadings of the BKB water column with particulate material vary by more than a factor of two between the two regimes. Higher partial pressure of CO₂ (<i>p</i>CO₂), higher concentrations of nutrients, and lower levels of oxygen saturation were observed in the bottom water near the eroded coasts, implying that coastal erosion and subsequent oxidation of eroded organic matter (OM) rather than the Lena River serves as the predominant source of nutrients to the BKB. Atmospheric CO₂ fluxes from the sea surface in the BKB vary from 1 to 95 mmol m⁻² day⁻¹ and are determined by specific features of hydrology and wind conditions, which change spatially, seasonally, and inter-annually. Mean values of CO₂ emission from the shallow Laptev Sea were similar in September 1999 and 2005 (7.2 and 7.8 mmol m⁻² day⁻¹, respectively), while the CO₂ efflux can be one order lower after a strong storm such as in September 2011. Atmospheric CO₂ emissions from a thawed coastal ice complex in the BKB area varied from 9 to 439 mmol m⁻² day⁻¹, with the mean value ranged from 75.7 to 101 mmol m⁻² day⁻¹ in two years (September 2006 and 2009), suggesting that at the time of observations the eroded coastal area served as a more significant source of CO₂ to the atmosphere than the tundra (mean value: 22.7 mmol m⁻² day⁻¹) on the neighboring Primorsky coastal plain (September 2006). The observed increase in the Lena River discharge since the 1990s suggests that increased levels of "satellite-derived" annual primary production could be explained by an increasing load of humic acids delivered to shelf water; in this water the color resulting from the presence of CDOM (colored dissolved organic matter) mimics the color resulting from the presence of Chl <i>a</i> when seen from space. Because the BKB area can be employed as an integrator of ongoing changes in the surrounding environment, we suggest that under ongoing changes, more nutrients, products of eroded OC transformation and river transport, will be delivered to the Arctic Ocean with its shrinking ice cover, potentially increasing primary production outside of the shallow East Siberian Arctic Shelf (ESAS). At the same time, because the ESAS is characterized by very low transparency which limits euphotic layer thickness, excessive <i>p</i>CO₂ will not be utilized by photosynthesis but will rather be emitted to the atmosphere at increasing rates, affecting regional CO₂ balance

Acidification of East Siberian Arctic Shelf waters through addition of freshwater and terrestrial carbon

Ocean acidification affects marine ecosystems and carbon cycling, and is considered a direct effect of anthropogenic carbon dioxide uptake from the atmosphere1–3 . Accumulation of atmospheric CO2 in ocean surface waters is predicted to make the ocean twice as acidic by the end of this century4 . The ArcticOcean is particularly sensitive to ocean acidification becausemoreCO2 candissolveincoldwater5,6 .Herewepresent observations of the chemical and physical characteristics of EastSiberianArctic Shelfwatersfrom1999,2000–2005,2008 and 2011, and find extreme aragonite undersaturation that reflects acidity levels in excess of those projected in this region for 2100. Dissolved inorganic carbon isotopic data and Markov chain Monte Carlo simulations of water sources using salinity andδ18 Odata suggest that the persistent acidification is driven by the degradation of terrestrial organic matter and discharge of Arctic river water with elevated CO2 concentrations, rather than by uptake of atmospheric CO2 . We suggest that East Siberian Arctic Shelf waters may become more acidic if thawing permafrost leads to enhanced terrestrial organic carbon inputs and if freshwater additions continue to increase, which may affect their efficiency as a source of CO2

East Siberian Sea: Interannual heterogeneity of the suspended particulate matter and its biogeochemical signature

The East Siberian Sea (ESS) is the largest, shallowest and most icebound Arctic marginal sea. It receives substantial input of terrigenous material and climate-vulnerable old organic carbon from both coastal erosion and rivers draining the extensive permafrost-covered watersheds. This study focuses on the interannual variability and spatial distribution of suspended particulate matter (SPM) in the surface and bottom waters of the ESS during the ice-free period in 2000, 2003, 2004, 2005 and 2008. We report on the composition and variability of particulate organic carbon (POC), total nitrogen (TN), POC/TN ratios, carbon and nitrogen isotopes (δ13C, δ15N) and provide estimates of the contribution of terrestrial organic carbon (terrOC) based on the δ13C isotopic values. The results show that interannual SPM distribution and elemental-isotopic characteristics of POC differ significantly between the western biogeochemical province (WBP; West of 165oE) and the eastern biogeochemical province (EBP; East of 165oE) of the ESS. The SPM mean concentration in the WBP is almost an order of magnitude higher than in the EBP. From west-to-east of the ESS, SPM tends to become more depleted in δ15N, while the δ13C becomes isotopically heavier. This trend can be explained by a shift in organic matter sources from terrigenous origin (erosion of the coastal ice complex and riverine POC) to becoming dominantly from marine plankton. The maximum contribution of terrOC to POC reached 99% in parts of the WBP, but accounts for as low as 1% in parts of the EBP. At the same time, the type of atmospheric circulation and its associated regime of both water circulation and ice transport control a displacement of the semi-stable biogeochemical border between WBP and EBP to the east or to the west if compared to its long-term average position near 165oE. Our multi-year investigation provides a robust observational basis for better understanding of the transport and fate of terrigenous material upon entering the ESS shelf waters. Our results also provide deeper insights into the interaction in the land-shelf sea system of the largest shelf sea system of the World Ocean, the East Siberian Arctic Shelf system

Sulfonyl Fluorides as Alternative to Sulfonyl Chlorides in Parallel Synthesis of Aliphatic Sulfonamides

Two types of aliphatic sulfonyl halides (Cl versus F) were compared in parallel synthesis of sulfonamides derived from aliphatic amines. Aliphatic sulfonyl fluorides showed good results with amines bearing an additional functionality, while the corresponding chlorides failed. Both sulfonyl halides were effective in the reactions with amines having an easily accessible amino group. Aliphatic sulfonyl chlorides reacted efficiently with amines bearing sterically hindered amino group while the corresponding fluorides showed low activity