Open AccessHydrography, nutrients, and carbon pools in the Pacific sector of the Southern Ocean: Implications for carbon flux
Author(s) -
Daly Kendra L.,
Smith Walker O.,
Johnson Gregory C.,
DiTullio Giacomo R.,
Jones David R.,
Mordy Calvin W.,
Feely Richard A.,
Hansell Dennis A.,
Zhang JiaZhong
Publication year - 2001
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/1999jc000090
Subject(s) - oceanography , environmental science , hydrography , phytoplankton , polar front , new production , nutrient , carbon cycle , dissolved organic carbon , deep chlorophyll maximum , geology , photic zone , chemistry , ecosystem , ecology , organic chemistry , biology
We investigated the hydrography, nutrients, and dissolved and particulate carbon pools in the western Pacific sector of the Antarctic Circumpolar Current (ACC) during austral summer 1996 to assess the region's role in the carbon cycle. Low f CO 2 values along two transects indicated that much of the study area was a sink for atmospheric CO 2 . The f CO 2 values were lowest near the Polar Front (PF) and the Subtropical Front (STF), concomitant with maxima of chlorophyll a and particulate and dissolved organic carbon. The largest biomass accumulations did not occur at fronts, which had high surface geostrophic velocities (20–51 cm s −1 ), but in relatively low velocity regions near fronts or in an eddy. Thus vertical motion and horizontal advection associated with fronts may have replenished nutrients in surface waters but also dispersed phytoplankton. Although surface waters north of the PF have been characterized as a “high nutrient‐low chlorophyll” region, low silicic acid (Si) concentrations (2–4 μ M ) may limit production of large diatoms and therefore the potential carbon flux. Low concentrations (4–10 μ M Si) at depths of winter mixing constrain the level of Si replenishment to surface waters. It has been suggested that an increase in aeolian iron north of the PF may increase primary productivity and carbon export. Our results, however, indicate that while diatom growth and carbon export may be enhanced, the extent ultimately would be limited by the vertical supply of Si. South of the PF, the primary mechanism by which carbon is exported to deep water appears to be through diatom flux. We suggest that north of the PF, particulate and dissolved carbon may be exported primarily to intermediate depths through subduction and diapycnal mixing associated with Subantarctic Mode Water and Antarctic Intermediate Water formation. These physical‐biological interactions and Si dynamics should be included in future biogeochemical models to provide a more accurate prediction of carbon flux.