Prevalence of strong vertical CO2 and O2 variability in the top meters of the ocean

Maria Ll Calleja*, Carlos M. Duarte, Marta Álvarez, Raquel Vaquer-Sunyer, Susana Agustí, Gerhard J. Herndl

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


The gradient in the partial pressure of carbon dioxide (pCO2) across the air-sea boundary layer is the main driving force for the air-sea CO2 flux. Global data bases for surface seawater pCO2 are actually based on pCO2 measurements from several meters below the sea surface, assuming a homogeneous distribution between the diffusive boundary layer and the upper top meters of the ocean. Compiling vertical profiles of pCO2, temperature, and dissolved oxygen in the upper 5-8 m of the ocean from different biogeographical areas, we detected a mean difference between the boundary layer and 5 m pCO2 of 13 ± 1 μatm. Temperature gradients accounted for only 11% of this pCO2 gradient in the top meters of the ocean; thus, pointing to a heterogeneous biological activity underneath the air-sea boundary layer as the main factor controlling the top meters pCO2 variability. Observations of pCO2 just beneath the air-sea boundary layer should be further investigated in order to estimate possible biases in calculating global air-sea CO2 fluxes. Key Points High pCO2 vertical variability within the upper meters of the ocean surfaceOnly 11% of pCO2 variability appears to be explained by temperature changesBiological processes exert a control in the observed CO2 vertical heterogeneity

Original languageEnglish (US)
Pages (from-to)941-949
Number of pages9
JournalGlobal Biogeochemical Cycles
Issue number3
StatePublished - Sep 2013
Externally publishedYes


  • oceans
  • oxygen concentration
  • pCO2 variability
  • temperature
  • top meters

ASJC Scopus subject areas

  • Global and Planetary Change
  • Environmental Chemistry
  • General Environmental Science
  • Atmospheric Science


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