Seasonal and latitudinal variability of the CO2 system in the western English Channel based on Voluntary Observing Ship (VOS) measurements - CNRS - Centre national de la recherche scientifique Accéder directement au contenu
Article Dans Une Revue Marine Chemistry Année : 2013

Seasonal and latitudinal variability of the CO2 system in the western English Channel based on Voluntary Observing Ship (VOS) measurements

Pierre Marrec
T. Cariou
  • Fonction : Auteur
E. Collin
M. Latimier
  • Fonction : Auteur
E. Mace
  • Fonction : Auteur
Pascal Morin
  • Fonction : Auteur
Stefan Raimund
  • Fonction : Auteur
  • PersonId : 974380
M. Vernet
Yann Bozec
  • Fonction : Auteur
  • PersonId : 912803
  • IdHAL : yann-bozec

Résumé

We investigated the dynamics of the CO2 system across the Western English Channel (WEC) between Roscoff (France) and Plymouth (UK) using a Voluntary Observing Ship (VOS). From December 2010 to December 2011, 20 return crossings were carried out to collect a comprehensive dataset of CO2 system parameters and ancillary data. The hydrographical structure of the water column across the latitudinal transect was investigated at 3 fixed stations: ASTAN (southern WEC, offshore Roscoff), El and L4 (northern WEC, offshore Plymouth). Based on these profiles, we defined two provinces, the stratified northern WEC (>49.5 degrees N) and the well-mixed southern WEC (<49.5 degrees N), which were periodically separated by a thermal front. These contrasted hydrographical properties strongly influenced the ecosystem dynamics. Biological production/respiration processes were the main driver of pCO(2) variability during the year except for winter cooling in the northern WEC. The seasonally stratified northern WEC showed enhanced biological activities characterized by an extensive autotrophic phase, which maintained the pCO(2) below the atmospheric equilibrium until early fall and acted as a sink for atmospheric CO2 at a rate of 1.1 mol C m(-2) y(-1). The permanently well mixed southern WEC was characterized by a shorter autotrophic phase due to a delayed spring phytoplankton growth and an early start of the fall heterotrophic phase, resulting in an annual air-sea CO2 flux close to equilibrium at a rate of -0.4 mol C m(-2) y(-1). On annual scale, calculation of Net Ecosystem Production (NEP) revealed that surface waters at El and ASTAN were both autotrophic at rates of 1.5 mol C m(-2) y(-1) and 1.0 mol C m(-2) y(-1), respectively. Our latitudinal approach resolved the discrepancy between the directions of the fluxes in the WEC observed in previous studies by differentiating between the hydrological regions. The combined approach of using data from VOS tracks and fixed coastal observatories stations provided new insights into the control of air-sea CO2 fluxes in the different provinces of the WEC. This combined approach could be applied in other continental shelf systems where data on the CO2 system are sparse. (C) 2013 Elsevier B.V. All rights reserved.
Fichier non déposé

Dates et versions

hal-01251677 , version 1 (06-01-2016)

Identifiants

Citer

Pierre Marrec, T. Cariou, E. Collin, A. Durand, M. Latimier, et al.. Seasonal and latitudinal variability of the CO2 system in the western English Channel based on Voluntary Observing Ship (VOS) measurements. Marine Chemistry, 2013, 155, pp.29-41. ⟨10.1016/j.marchem.2013.05.014⟩. ⟨hal-01251677⟩
152 Consultations
0 Téléchargements

Altmetric

Partager

Gmail Facebook X LinkedIn More