| Chlorofluorocarbon (CFC-11 and CFC-12) observations in the North Pacific measured during the 1980's are used to evaluate a global coarse resolution, seasonal version of the GFDL OGCM. The model successfully simulates the CFC water column burden and CFC ratio ages than the absolute tracer concentrations. In quiescent areas (135{dollar}spcirc{dollar}W), the model simulation of the observed tracer fields is better than in areas where higher interannual variability is observed, such as near the subarctic front (40{dollar}spcirc{dollar}N) in the 165{dollar}spcirc{dollar}E and 170{dollar}spcirc{dollar}W sections. If the observed fields are objectively mapped at the model resolution, the observations more closely resemble the model fields. The CFC ratio ages (CFC-11/CFC-12 and CFC-11/CCl{dollar}sb4{dollar}) are "ventilation ages", the average age of the water in that water parcel ventilated by a transient tracer. This is different from the average age of all of the water in an imaginary water parcel ("equilibrium age").; The Samoa Passage, a {dollar}sim{dollar}50 km feature, controls the bottom water mass characteristics in the real North Pacific Ocean. Without this feature, the model deep North Pacific T-S characteristics show in intermediate water mass not found in the real ocean. The Aleutian Arc controls the positioning of the center of the subtropical gyre. The coarse model topography does not simulate this feature, causing the model to overventilate atmospheric tracers in the subarctic North Pacific.; In the North Pacific, the fresher subarctic water flows between two saltier layers: the lighter subtropical water and the denser NPDW, creating a salinity minimum. The North Pacific salinity minimum (NPSM) in the model is a ventilated feature, an imprint of the subarctic ventilation, occurring on the densest water to outcrop in the North Pacific. The CFCs on the model salinity minimum are derived from atmospheric contact at the annual isopycnal outcrop. The NPSM in the model is not a feature of ventilation. The CFC-11/CFC-12 ratio ages and ideal age tracers monotonically increase with depth. The vertical derivative of ideal age with respect to density has a maximum in the salinity minimum, demonstrating that the minimum is a boundary between the surface recently ventilated water and the older, deeper water. |
