Silica fluxes in the northeast Atlantic frontal zone of Mode Water formation (38 degrees-45 degrees N, 16 degrees-22 degrees W) in 2001-2002 - Archive ouverte HAL Access content directly
Journal Articles Journal of Geophysical Research. Oceans Year : 2005

Silica fluxes in the northeast Atlantic frontal zone of Mode Water formation (38 degrees-45 degrees N, 16 degrees-22 degrees W) in 2001-2002

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J Mosseri
  • Function : Author
B. Quéguiner
P Rimmelin
  • Function : Author
C Guieu

Abstract

[ 1] The biogenic (BSi) and lithogenic (LSi) silica export fluxes were investigated in the northeast Atlantic (38 degrees - 45 degrees N, 16 degrees - 22 degrees W) as part of the Programme Ocean Multidisciplinaire Meso Echelle (POMME) program in 2001 - 2002. They were measured at four stations located on both sides of a frontal zone (40 degrees - 42 degrees N) by means of permanent moorings of sediment traps deployed at 400 and 1000 m depth. Averaged over the area, the annual BSi fluxes ( corrected from Th-230 trapping efficiencies) ranged between 0.240 mmol m(-2) d(-1) at 400 m to 0.316 mmol m(-2) d(-1) at 1000 m. The bulk annual BSi fluxes are comparable to bulk BSi export fluxes recorded for oligotrophic areas. The annual export flux of LSi ( range 0.029 mmol m(-2) d(-1) at 400 m to 0.054 mmol m(-2) d(-1) at 1000 m) was lower than BSi and accounted for 10% of the total silica export flux. Results show a strong coupling between the two siliceous particulate fractions, which is interpreted as reflecting LSi scavenging by BSi and limitation of BSi production in surface water by lithogenic ( trace metals) inputs. BSi export was maximum at the beginning of the productive season during the spring bloom. However, annual BSi export fluxes in 2001 were quite higher at 400 m in the southern area ( e. g., 0.249 - 0.288 at the southeast station versus 0.211 mmol BSi m(-2) d(-1) at the northeast station) contradictory to the classical south-north surface production increase. We suggest an advective lateral transport within the upper 400 m of siliceous particles from the northern, more productive area to the southern region.
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hal-03494209 , version 1 (19-12-2021)

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J Mosseri, B. Quéguiner, P Rimmelin, N Leblond, C Guieu. Silica fluxes in the northeast Atlantic frontal zone of Mode Water formation (38 degrees-45 degrees N, 16 degrees-22 degrees W) in 2001-2002. Journal of Geophysical Research. Oceans, 2005, 110 (C7), ⟨10.1029/2004JC002615⟩. ⟨hal-03494209⟩
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