Diurnal carbon cycling in the surface ocean and lower atmosphere of Santa Monica Bay, California

• Published in: Geophysical research letters 2009-04, Vol.36 (8), p.n/a
• Main Authors: Leinweber, A., Gruber, N., Frenzel, H., Friederich, G. E., Chavez, F. P.
• Format: Article
• Language: English
• Subjects: Atmosphere; Biogeochemistry; Carbon; Carbon cycle; carbon cycling; Carbon dioxide; diurnal changes; Diurnal variations; Earth sciences; Earth, ocean, space; Exact sciences and technology; Geobiology; Marine; Oceanography; Primary production
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2008GL037018

We investigate the diurnal carbon cycle in the near surface ocean and atmosphere of Santa Monica Bay, California on the basis of hourly measurements of the oceanic and atmospheric partial pressures of CO2 (pCO2oc and pCO2atm) and related parameters from a moored platform. The power spectrum of the data from three deployments during late spring, summer, and fall reveal a strong peak at 1 cycle/day for both oceanic and atmospheric pCO2. While the average diurnal peak‐to‐peak amplitude is about 15 to 20 μatm for pCO2oc and about 10 μatm for pCO2atm, the 10% largest amplitudes exceed 55 μatm and 42 μatm, respectively. The diurnal cycle of oceanic pCO2 is primarily controlled by temperature, but biological processes substantially modify it. The contribution of lateral processes, such as tides, is likely small. For the fall deployment, our data suggest an average net primary production of about 30 mmol C m−2 day−1. The diurnal cycle of atmospheric pCO2 is primarily controlled by the air‐sea breeze. Neglect of the diurnal variations in the flux calculations may result in biases of more than 0.2 mol C m−2 a−1.