UBC Theses and Dissertations
Circulation of the Northeast Pacific Ocean inferred from temperature and salinity data Matear, Richard James
The temperature, salinity, and pressure (STP) data were collected during two cruises, one in early October and the other in early December of 1987, as part of the Ocean Storms experiment. These hydrographic data were analyzed to determine circulation of the northeast Pacific Ocean and to calculate the factors influencing the heat and salt content of the upper ocean. From the depth profiles of the temperature and salinity data, the water mass in the Ocean Storms area was classified as being the Eastern Sub-Arctic Pacific Water Mass. Maps of dynamic height for this area revealed that the current pattern was generally smooth but that mesoscale eddies did exist in the flow. Isentropic analysis of the temperature and salinity fields produced a flow pattern that was generally consistent with the. dynamic height maps. However, this analysis revealed additional details in the flow that were not evident in the dynamic height maps. To extract additional information from the temperature and salinity data an inverse model was developed. This model assumed that the flow was geostrophic and that the vertical velocity satisfied a linear β-plane vorticity equation. This inverse model calculated the vertical and horizontal velocities at a reference level of 1000 dbars, and the horizontal and vertical mixing terms by conserving mass, salt, and heat. These conservation constraints were applied to large- boxes defined by four hydrographic stations and two pressure surfaces. The circulation determined using the model showed well-defined flow features. Comparison of the absolute geostrophic flow with the seven-day averaged current meter observations showed much similarity, despite complications from an incident storm. Correlation between the geostrophic flow at the surface and the total flow field inferred from drifter data was also high. An estimate of the ageostrophic flow suggested that acceleration and nonlinear terms played an important role in affecting the flow field during the first cruise. The observed change in salt content of the upper 150 m of the ocean was .004 ppt for the sixty days between the two cruises. The net transport of salt into the study area by the calculated flow field was -.016 ppt. Therefore, to balance the salt budget would require E - P = 9 cm. The upper ocean lost 92 W/m² of heat during the sixty days between the two cruises. As the vertical and horizontal transport of heat acounted for 40 W/m² loss of heat, the remainder of heat lost, 52 W/m² was attributed to air-sea boundary processes.
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