Aquatic Sciences Meeting, Albuquerque 2001

SS02 Photochemical Reactions In Surface Waters: A Major Issue in the 21st Century? (Environmental Connections)

Date: Friday, February 16, 2001, Time: 11:15:00 AM

Location: San Miguel

Najjar, R, G, The Pennsylvania State University, University Park, USA, najjar@essc.psu.edu

Zafiriou, O, , Woods Hole Oceanographic Institution, Woods Hole, USA,

Cutter, G, , Old Dominion University, Norfolk, USA,

Kieber, R, , University of North Carolina, Wilmington, USA,

Nelson, N, , University of California, Santa Barbara, USA,

A MODEL OF DIURNAL AND SEASONAL VARIATIONS OF CARBON MONOXIDE, CARBONYL SULFIDE AND HYDROGEN PEROXIDE IN SARGASSO SEA SURFACE WATERS

A model of three photochemically produced species--carbon monoxide (CO), carbonyl sulfide (OCS) and hydrogen peroxide (H2O2)--in Sargasso Sea surface waters is developed with the intent of quantitatively evaluating the extent to which measured rate processes and concentrations are internally consistent. Measurements were made on the RV Endeavor during 10-day station occupations in August 1999 and March 2000. The model includes air-sea gas exchange of CO and OCS, dry and wet deposition of H2O2, photochemical production, biological consumption, dark production and vertical mixing. Air-sea gas exchange is computed from measured wind speed and atmospheric CO and OCS concentrations. Dry and wet deposition of H2O2 are estimated from gas phase and rain water H2O2 concentration measurements. Photochemical production is estimated in two ways: (1) a combination of action spectra and measurements of the underwater UV irradiance distribution and (2) in situ measurements of daily and spectrally integrated production from an optical buoy. CO consumption lifetime was measured from radiocarbon incubations on the optical buoy. Various dark incubations were also conducted to estimate CO, OCS and H2O2 lifetimes. Finally, vertical mixing is estimated using the one-dimensional K-profile parameterization (KPP) model of Large et al. (1994). The KPP model is forced using shipboard measurements of wind velocity, air temperature, humidity, precipitation and downwelling longwave and shortwave irradiance, and evaluated with measurements of temperature, salinity and horizontal current velocity. Results of the chemical model will be presented and evaluated with measurements of the concentrations of CO, OCS and H2O2 from vertical profiles typically several times per day and nearly continuous surface water measurements.

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Aquatic Sciences Meeting, Albuquerque 2001

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