HR: 0800h
AN: OS51C-1322    [Abstracts]
TI: Comparative study on deficiency of N-nutrient deduced from Beaufort and Laptev Sea expedition data (JWACS and NABOS cruises)
AU: * Tanaka, N
EM: norit@iarc.uaf.edu
AF: IORGC, JAMSTEC, 2-15 Natsushima Cho, Yokosuka, 237-0061 Japan
AU: * Tanaka, N
EM: norit@iarc.uaf.edu
AF: IARC, UAF, 930 Koyukuk Dr, Fairbanks, AK 99775-7335 United States
AU: Murata, A
EM: akihiko.murata@jamstec.go.jp
AF: IORGC, JAMSTEC, 2-15 Natsushima Cho, Yokosuka, 237-0061 Japan
AU: Nitishinsky, M
EM: miroslav@otto.nw.ru
AF: AARI, 38 Bering St, St. Petersburg, 199397 Russian Federation
AU: Timokhov, L
EM: ltim@aari.nw.ru
AF: AARI, 38 Bering St, St. Petersburg, 199397 Russian Federation
AB: Arctic shelf and its vicinity are posted to be the most active area for denitrification in the world ocean. The recent stable nitrogen isotope study suggests that there is no appreciable evidence for denitrification in water column although there is substantial deficiency in nitrogen in water column. Nitrogen isotope study revealed that the water column deficiency is due to unidirectional nitrogen uptake by sediments, which is driven by sedimentary denitrification (T. Tanaka et al., Cont. Shelf Res., 2004). Nitrogen loss by dinitrification in the area was posted as large as 20 Tg-N/year, which corresponds 15-25 % of nitrogen loss in the world ocean, if entire shelf area in arctic and its vicinity is active in denirification. JWACS (Joint Western Arctic Climate Study) and NABOS (Nansen & Amundsen Basin Observational System) has been carried out hydrographic observation cruises by Japanese R/V Mirai, Canadian icebreakers and Russian icebreaker in the last 3 years to understand Arctic Ocean Response to the Climate Change and its feed back to the global climate system. Those cruises gave us unique opportunity to examine nutrient dynamics in surface stratified water layers, which the upmost response and affect climatic system in the Arctic, which include physical climate and biological response forcing physical climate system. In this study, N*=(NO3-+NO2--16PO4+2.9)x0.87 is estimated in Laptev Sea and Beaufort Sea. N* in Laptev Sea shows all positive values averaged at 3.8, indicating typical Atlantic surface layer signature. Whereas N* values in Canada Basin showed startling negative values as low as -13. The lowest value was found in the nutrient maximum subsurface layer with almost freezing water temperature (Cold Halocline Water). N* -phosphate diagram and N*-nitrate diagram revealed remarkably weak denitrification signature in Laptev Sea.
DE: 4815 Ecosystems, structure and dynamics
DE: 4845 Nutrients and nutrient cycling
DE: 1050 Marine geochemistry (4835, 4850)
DE: 1615 Biogeochemical processes (4805)
DE: 0330 Geochemical cycles
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting