Transport of the North Atlantic Current

• Main Author: Meinen, Christopher Stuart
• Format: Text
• Language: English
• Published: DigitalCommons@URI 1998
• Subjects: Oceanography; Newfoundland; north atlantic current; North Atlantic
• Online Access: https://digitalcommons.uri.edu/dissertations/AAI9902585

Geostrophic relative velocity profiles from a hydrographic section obtained in August 1993 were referenced using POGO floats and acoustic doppler current profiler measurements, yielding a calculated absolute transport for the North Atlantic Current (NAC) of $\rm112 \times 10\sp6\ m\sp3\ s\sp{-1}$. Based on a thorough study of sources of error, the transport was determined with unprecedented accuracy, $\rm{\pm}23 \times 10\sp6\ m\sp3\ s\sp{-1}$. This transport includes a portion of the northward transport of the Mann Eddy, a large permanent eddy adjacent to the NAC, as is customary at this location since the two northward flows are generally indistinguishable. Historical hydrography was used to demonstrate that the variation of vertical structure in the Newfoundland Basin is dominated by a single lowest mode. Using moored current meter and inverted echo sounder measurements, full-water-column profiles of temperature, and specific volume anomaly, $\delta$, were obtained daily on a section across the NAC along the WOCE ACM6 transect near 42.5$\sp\circ$N. Profiles of $\delta$, integrated vertically, result in profiles of geopotential height anomaly, $\Delta\Phi$; horizontal gradients of $\Delta\Phi$ yield relative velocity profiles, which were absolutely referenced using deep current meters and bottom pressure sensors. These methods provide timeseries of temperature and absolute velocity sections spanning the NAC. The mean absolute transport of the NAC, spanning August 1993 through February 1995, was $\rm146 \pm 14 \times 10\sp6\ m\sp3\ s\sp{-1}$. The barotropic component of the transport (defined as $V\sb{bot}\times H$) exceeded 33% of the total transport. Temperature and absolute velocity sections were used to determine the mean stream-coordinates structure of the NAC, which is narrower and stronger than the Eulerian structure. Peak speeds exceed 80 cm s$\sp{-1}$ and bottom velocities surpass 10 cm s$\sp{-1}$. The mean transport in stream-coordinates is $\rm131 \pm 14 \times 10\sp6\ m\sp3\ s\sp{-1}$. The decrease in transport when calculated in stream-coordinates results from smoothing of the Mann Eddy. The throughput transport of the NAC (removing the contribution of the Mann Eddy) is estimated to be $\rm90 \times 10\sp6\ m\sp3\ s\sp{-1}$. Using these measurements and other published results, a scheme for the overall circulation and transport in the Newfoundland Basin is presented.