National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 1999

Thermocline ventilation and oxygen utilization rates in the subtropical North Pacific based on CFC distributions during WOCE

Sonnerup, R.E., P.D. Quay, and J.L. Bullister

Deep-Sea Res. I, 46(5), 777–805, doi: 10.1016/S0967-0637(98)00092-2 (1999)

Thermocline ventilation rates for the subtropical North Pacific are determined using a 1-dimensional (meridional) along-isopycnal advective-diffusive model tuned to chlorofluorocarbon (CFC) concentrations measured along 152°W in 1991 during WOCE P16. Mean southward advection rates in the subtropics range from 1.03 to 0.56 cm s−1 between σθ = 25.5 and 26.6. Model-derived ventilation times for the subtropical gyre increase from about 10 to 27 years for that isopycnal range. Oxygen utilization rates (OURs) determined using the advective-diffusive model decrease with depth from 6.6 to 3.2 µmol kg−1 yr−1 between σθ = 25.5 and 26.6. Extrapolation of the OUR versus depth trend to the base of the euphotic zone with the 1/Z power function of Martin et al. (1987) and integration from 500 to 100 m depth implies a carbon export rate from the overlying euphotic zone of 2.2 ± 0.5 moles C m−2 yr−2 at 30°N, 152°W. Analysis of the WOCE radiocarbon and salinity distributions indicates that zonal and crossisopycnal transport terms would have to be considered in modeling these tracers in the subtropical North Pacific.

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