(Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1994-06)
Kettle, A. James
A field experiment demonstrated the presence of a diurnal cycle in the concentration
of carbon monoxide ([CO]) in the upper ocean at the BATS site. A series
of laboratory experiments and numerical simulations were carried out to assess the
diurnal variation in [CO] both at the sea surface and in the upper layers of the water
column down to 200 m. Published studies of this cycle have suggested that the dominant
controlling processes are light-induced production, microbial CO consumption,
surface degassing, and dilution due to entrainment of deeper CO-depleted water into
the mixed layer. Laboratory experiments focussed on finding the production rate coefficient
and the destruction rate. The numerical studies were conducted to simulate
the diurnal cycle in [CO] at the sea surface and at depth, and the results confirmed
the values of the production rate coefficient and destruction rate obtained by the
laboratory experiments. The field measurements indicate that [CO] does not vanish
below the euphotic zone as expected. This may be due to a possible blank correction
to the measurements, low destruction rate at depth, or a small dark production rate.
The CO consumption e-folding was optimized by numeric experiment and calculated
to be about 52±9 h on the basis of a minimized sea surface [CO] deviation and 73±10
h on the basis of minimized CO inventory deviation. Laboratory determinations of
apparent quantum yield and numeric experiment lead to an optimized sea surface
production of CO 0.40 ± 0.05nMh-1. Finally, deviations between the [CO] measurements
and numeric experiments suggest that factors controlling the CO budget may
be subject to spatial and temporal patchiness.
