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Impacts of increasing anthropogenic soluble iron and nitrogen deposition on ocean biogeochemistry
Author(s) -
Krishnamurthy Aparna,
Moore J. Keith,
Mahowald Natalie,
Luo Chao,
Doney Scott C.,
Lindsay Keith,
Zender Charles S.
Publication year - 2009
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2008gb003440
Subject(s) - biogeochemistry , biogeochemical cycle , deposition (geology) , environmental chemistry , reactive nitrogen , environmental science , photic zone , new production , phytoplankton , oceanography , nitrogen , nitrate , biogenic silica , nutrient , diatom , chemistry , ecology , geology , sediment , biology , paleontology , organic chemistry
We present results from transient sensitivity studies with the Biogeochemical Elemental Cycling (BEC) ocean model to increasing anthropogenic atmospheric inorganic nitrogen (N) and soluble iron (Fe) deposition over the industrial era. Elevated N deposition results from fossil fuel combustion and agriculture, and elevated soluble Fe deposition results from increased atmospheric processing in the presence of anthropogenic pollutants and soluble Fe from combustion sources. Simulations with increasing Fe and increasing Fe and N inputs raised simulated marine nitrogen fixation, with the majority of the increase in the subtropical North and South Pacific, and raised primary production and export in the high‐nutrient low‐chlorophyll (HNLC) regions. Increasing N inputs alone elevated small phytoplankton and diatom production, resulting in increased phosphorus (P) and Fe limitation for diazotrophs, hence reducing nitrogen fixation (∼6%). Globally, the simulated primary production, sinking particulate organic carbon (POC) export. and atmospheric CO 2 uptake were highest under combined increase in Fe and N inputs compared to preindustrial control. Our results suggest that increasing combustion iron sources and aerosol Fe solubility along with atmospheric anthropogenic nitrogen deposition are perturbing marine biogeochemical cycling and could partially explain the observed trend toward increased P limitation at station ALOHA in the subtropical North Pacific. Excess inorganic nitrogen ([NO 3 − ] + [NH 4 + ] − 16[PO 4 3− ]) distributions may offer useful insights for understanding changing ocean circulation and biogeochemistry.