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A two‐dimensional nitrogen and carbon flux model in a coastal upwelling region
Author(s) -
Ianson Debby,
Allen Susan E.
Publication year - 2002
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 - 10.1029/2001gb001451
Subject(s) - upwelling , photic zone , oceanography , environmental science , sink (geography) , flux (metallurgy) , isopycnal , total organic carbon , carbon sink , dissolved organic carbon , atmospheric sciences , geology , phytoplankton , climate change , chemistry , nutrient , geography , environmental chemistry , cartography , organic chemistry
Coastal upwelling regions are associated with high primary production and disproportionately large fluxes of organic matter relative to the global ocean. However, coastal regions are usually homogenized in global ocean carbon models. We have developed a carbon and nitrogen flux model including all major processes both within and below the euphotic zone over seasonal to decadal timescales for coastal upwelling regions. These fluxes control surface p CO 2 . The model is applied to the west coast of Vancouver Island, Canada (∼49°N, 126°W). Net annual air‐sea CO 2 exchange and export flux of inorganic and organic carbon and nitrogen from the system to the rest of the ocean are estimated for different model scenarios. Model sensitivities are discussed. Results show strong biological drawdown of p CO 2 during summer and atmospheric CO 2 invasion. However, this invasion is nearly balanced by gas evasion during winter. Therefore the region is a much smaller sink of atmospheric CO 2 (6 g C m −2 yr −1 , or equivalently 200 kg C yr −1 per m coastline) than the summer season predicts. More significantly, there is a large flux of inorganic carbon (3 × 10 4 kg C yr −1 per m coastline) from intermediate depth ocean water to the surface ocean via the coastal system compared to a small export of organic carbon (all dissolved) (2 × 10 3 kg C yr −1 per m coastline) back into the lower layer of the open ocean. Thus we suggest that the dominant effect of coastal upwelling on the global ocean is providing a conduit for inorganic carbon to the surface ocean.