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- Title
- VERTEX: carbon cycling in the northeast Pacific,
- Description
- Particulate organic carbon fluxes were measured with free-floating particle traps at nine locations during VERTEX and related studies. Examination of these data indicated that there was relatively little spatial variability in open ocean fluxes. To obtain mean rates representative of the oligotrophic environment, flux data from six stations were combined and fitted to a normalized power function, F = F 100 (z/100) b; e.g. the open ocean composite C flux in mol m -2 y -1 = 1.53 (z/100 -0.858 with depth z in meters. It is shown that the vertical derivative of particulate fluxes may indicate solute regeneration rates, and accordingly regeneration rates for C, H and N were estimated. Oxygen utilization rates were also estimated under the assumption that 1.5, 1.0 and 0.25 moles of O 2 were used for each mole of N, C and H regenerated. Regeneration ratios of these elements were depth-dependent: i.e. N:C:H:-O 2 = 1.0 N: 6.2 (z/100) 0.130 C: 10.0(z/100) 0.146 H: [1.5 + 6.2 (z/100) 0.130 + 2.5 (z/100) 0.146]-O 2. Comparisons of our rates with those in the literature indicate that trap-derived new productivities in the open Pacific (≈1.5 mol C m -2 y -1) are substantially less than those estimated from oxygen utilization rates in the Sargasso Sea (≈4 mol C m -2 y -1). A hypothesis is presented which attempts to explain this discrepancy on the basis of the lateral transport and decomposition of slow or non-sinking POC in the Sargasso Sea. Data gathered during the VERTEX studies are also used for various global estimates. Open ocean primary productivities are estimated at 130 g C m -2 y -1 which results in a global open ocean productivity of 42 Gt y -1. Organic C removal from the surface of the ocean via particulate sinking (new production) is on the order of 6 Gt y -1. Fifty percent of this C is regenerated in the upper 300 m of the water column. The ratio of new production (measured with traps) to total primary production (measured via 14C) is 0.14. It is concluded that the 14C technique yields reasonable estimates of primary productivity provided that care is taken to prevent heavy metal contamination. © 1987., Cited By (since 1996):671, Oceanography, ,
- Author
- Martin, Knauer, Karl, Broenkow
- Date
- 1987-01-01T00:00:00Z
- Title
- VERTEX lateral transport: The lateral transport of manganese in the northeast Pacific,
- Description
- Vertical distributions (0 to 2000 m) of dissolved Mn were measured at 5 stations on a 3200-km east-west (California to Hawaii) transect during the VERTEX (Vertical Transport and Exchange) IV and V cruises. All profiles shared common features: surface maxima, subsurface minima, maxima associated with the oxygen minimum, and relatively low levels at depth. Particulate Mn fluxes, measured at four of the five stations using free-floating particle traps (∼ 100 to 2000 m), indicated that in situ particulate scavenging was not responsible for the formation of the subsurface dissolved Mn minimum nor was in situ particulate Mn regeneration responsible for the dissolved Mn maximum associated with the oxygen minimum. Thus, these dissolved Mn extrema result primarily from lateral advective transport processes. The Mn minimum is associated with the shallow salinity minimum, a water mass that sinks away from the surface in the North Pacific (∼ 47°N), and spreads to the south and east in our study area. Additional evidence of the onshore flow of open-ocean, near-surface water is provided by the high Pb concentrations (∼ 50 pmol kg -1 associated with this feature. Waters in the oxygen minimum/ Mn maximum appear to have northerly and offshore flow in our study area. Box model estimates indicate that offshore lateral advective velocities must approach 0.4 cm s -1 to balance vertical diffusive losses from the oxygen minimum/dissolved Mn maximum. Maintenance of the subsurface Mn minimum requires onshore lateral transport of water with low Mn content at velocities on the order of 0.9 cm s -1 offshore, increasing to 4.4 cm s -1 inshore. These velocities represent maximum estimates since north-south Mn distribution data were not available. © 1985., Cited By (since 1996):23, Oceanography, ,
- Author
- Martin, Knauer, Broenkow
- Date
- 1985-01-01T00:00:00Z