HR: 17:00h
AN: OS34A-05 [Abstracts]
TI: Pacific dominance of oceanic N2 fixation diagnosed from nutrient distributions
AU: * Deutsch, C
EM: cdeutsch@ocean.washington.edu
AF: Program on Climate Change, University of Washington, 1492 Boat St., Seattle, WA 98195
AU: Gruber, N
EM: ngruber@igpp.ucla.edu
AF: Department of Atmospheric Sciences and IGPP, UCLA, 5853 Slichter Hall, Los Angeles, CA 90095
AU: Sarmiento, J L
EM: jls@splash.princeton.edu
AF: Department of Geosciences, Princeton University, Guyot Hall, Princeton, NJ 08540
AU: Sigman, D M
EM: sigman@princeton.edu
AF: Department of Geosciences, Princeton University, Guyot Hall, Princeton, NJ 08540
AB:
Nitrogen fixation, the dominant input of biologically available nitrogen (N) to the ocean, is traditionally viewed as being
spatially segregated from denitrification, the dominant N loss. However, because of spatial and temporal variability, the
global distribution of marine N2 fixation is difficult to determine from direct shipboard measurements. By assimilating
climatological distributions of the major nutrients NO3 and PO4 within an ocean circulation model, we estimate a
necessary signature of N2 fixation: the net biological uptake of PO4 that occurs in the absence of a stoichiometric
uptake of NO3. The global rate of N2 fixation is estimated at ~150 TgN/yr, and is found primarily in subtropical
latitudes, where this process accounts for 50-90% of the N exported from surface waters. The highest N2 fixation rates
are diagnosed in the Pacific Ocean, where water column denitrification rates are high but the rate of atmospheric Fe
deposition, thought to limit oceanic N2 fixation, is relatively low. These results suggest that oceanic N2 fixation is
most strongly coupled to the generation of N-deficient waters in denitrification zones, supporting the view that N2
fixation effectively stabilizes the ocean fixed N reservoir over time.
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0469 Nitrogen cycling
DE: 0470 Nutrients and nutrient cycling (4845, 4850)
DE: 0545 Modeling (4255)
DE: 4273 Physical and biogeochemical interactions
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005