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

Ebullition-Driven Fluxes of Methane from Shallow Hot Spots in the East Siberian Arctic Shelf

The maximum concentration of atmospheric methane (CH4) occurs over the Arctic: the value of CH4 over Greenland exceeds that over Antarctica by 8-10%; an absolute maximum is measured during wintertime (Steel et. al., 1987; Fung et. al., 1991). Geologic evidence provides insight into possible climate change effects from a warmer Arctic, suggesting that enhanced Arctic CH4 emissions during warm periods played a key role in past rapid climate change.This work was supported by the International Arctic Research Center of the University Alaska Fairbanks (by the Cooperative Institute for Arctic Research through NOAA Cooperative Agreement NA17RJ1224 and the National Science Foundation Agreement No OPP-0327664), the Russian Foundation for Basic Research (No.04-05-64819) and the Far-Eastern Branch of Russian Academy of Sciences, RAS (Project: Environmental changes in the East-Siberian region)

Organic matter composition and greenhouse gas production of thawing subsea permafrost in the Laptev Sea

Subsea permafrost represents a large carbon pool that might be or become a significant greenhouse gas source. Scarcity of observational data causes large uncertainties. We here use five 21-56 m long subsea permafrost cores from the Laptev Sea to constrain organic carbon (OC) storage and sources, degradation state and potential greenhouse gas production upon thaw. Grain sizes, optically-stimulated luminescence and biomarkers suggest deposition of aeolian silt and fluvial sand over 160 000 years, with dominant fluvial/alluvial deposition of forest- and tundra-derived organic matter. We estimate an annual thaw rate of 1.3 ± 0.6 kg OC m−2 in subsea permafrost in the area, nine-fold exceeding organic carbon thaw rates for terrestrial permafrost. During 20-month incubations, CH4 and CO2 production averaged 1.7 nmol and 2.4 µmol g−1 OC d−1, providing a baseline to assess the contribution of subsea permafrost to the high CH4 fluxes and strong ocean acidification observed in the region

シベリア側北極海の沿岸-陸棚-海盆域に及ぶ生物地球化学過程の変化

北極海の中でもシベリア側北極海は、地球温暖化に伴う海底永久凍土の融解や海岸浸食、そして海氷激減が引き金となり生物地球化学的な変化が最もダイナミックに起きている海域である。海底永久凍土の融解は温暖化ガスであるメタンを大気中に放出させ (Shakhova et al., 2010a, b)、さらなる温暖化を招く恐れがある。海岸浸食は炭素・栄養塩・微量金属・粒子態及び溶存態有機物等を北極海に供給し (e.g., Semiletov et al., 2011, 2012, 2013)、CO2の大気への放出や基礎生産、微生物生産の増減を左右する可能性がある。また、海氷減少は水塊構造や海洋循環の変化を伴い栄養塩分布を変化させ (Nishino et al., 2011, 2013)、その結果、基礎生産や生物ポンプにも影響すると考えられる。しかし、この海域はロシアEEZ内、或いはそれに近接しているため、利用できるデータが非常に限られており、生物地球化学的な変化の定量的な評価はもちろん、基本的な物質循環像さえ、ほとんど分かっていない。 　本研究では、ロシアEEZ海域を含むシベリア側北極海の船舶観測を中心として、氷上キャンプやセジメントトラップ・係留系による観測、さらに衛星データや数値モデルを駆使して、シベリア側北極海で起きているダイナミックな生物地球化学的変化を把握するとともに、それが環北極海域、そして全球の生態系・気候システムに与える影響について評価する。発表資料, 北極環境研究コンソーシアム (JCAR) 長期計画ワークショッ

CASCADE-The Circum-Arctic Sediment CArbon DatabasE

Biogeochemical cycling in the semi-enclosed Arctic Ocean is strongly influenced by land–ocean transport of carbon and other elements and is vulnerable to environmental and climate changes. Sediments of the Arctic Ocean are an important part of biogeochemical cycling in the Arctic and provide the opportunity to study present and historical input and the fate of organic matter (e.g., through permafrost thawing). Comprehensive sedimentary records are required to compare differences between the Arctic regions and to study Arctic biogeochemical budgets. To this end, the Circum-Arctic Sediment CArbon DatabasE (CASCADE) was established to curate data primarily on concentrations of organic carbon (OC) and OC isotopes (δ13C, Δ14C) yet also on total N (TN) as well as terrigenous biomarkers and other sediment geochemical and physical properties. This new database builds on the published literature and earlier unpublished records through an extensive international community collaboration. This paper describes the establishment, structure and current status of CASCADE. The first public version includes OC concentrations in surface sediments at 4244 oceanographic stations including 2317 with TN concentrations, 1555 with δ13C-OC values and 268 with Δ14C-OC values and 653 records with quantified terrigenous biomarkers (high-molecular-weight n-alkanes, n-alkanoic acids and lignin phenols). CASCADE also includes data from 326 sediment cores, retrieved by shallow box or multi-coring, deep gravity/piston coring, or sea-bottom drilling. The comprehensive dataset reveals large-scale features of both OC content and OC sources between the shelf sea recipients. This offers insight into release of pre-aged terrigenous OC to the East Siberian Arctic shelf and younger terrigenous OC to the Kara Sea. Circum-Arctic sediments thereby reveal patterns of terrestrial OC remobilization and provide clues about thawing of permafrost. CASCADE enables synoptic analysis of OC in Arctic Ocean sediments and facilitates a wide array of future empirical and modeling studies of the Arctic carbon cycle. The database is openly and freely available online (https://doi.org/10.17043/cascade; Martens et al., 2021), is provided in various machine-readable data formats (data tables, GIS shapefile, GIS raster), and also provides ways for contributing data for future CASCADE versions. We will continuously update CASCADE with newly published and contributed data over the foreseeable future as part of the database management of the Bolin Centre for Climate Research at Stockholm University