Long-Period Transport Changes in the Eastern North Atlantic and Their Simulation by Propagating Waves

• Published in: Journal of Geophysical Research: Oceans
• Main Authors: Siedler, Gerold, Finke, Michael
• Format: Article in Journal/Newspaper
• Language: English
• Published: AGU (American Geophysical Union) 1993
• Subjects: North Atlantic
• Online Access: https://oceanrep.geomar.de/id/eprint/15382/; https://oceanrep.geomar.de/id/eprint/15382/1/92JC02122.pdf; https://doi.org/10.1029/92JC02122

An analysis is presented of geostrophic volume transport across a zonal line along 28-degrees-N in the eastern Atlantic. The data are from an array of five moorings with 200-km spacing carrying temperature sensors and one current meter each for 1 or 2 years. Transport changes in the main thermocline relative to a fixed depth level are obtained by the use of temperature-salinity relationships. The transport variability is simulated by two propagating waves with first-order baroclinic mode structure. Solutions exist with annual and semi-annual periods and zonal wavelengths of 100-200 km and 300 km, respectively. Assuming quasi-geostrophic dynamics and using results on the Reynolds stress, the dominating waves of annual and semi-annual period are found to propagate to the southwest, with 45-degrees-60-degrees and 25-degrees to the south off the westward direction, respectively. Wave solutions with a 90-day period and a zonal wavelength of about 300 km are interpreted as an effect of barotropic waves arising due to horizontal temperature inhomogeneity. The propagation is about +/-25-degrees off the westward direction. In general, good approximations are obtained with the propagating wave simulations in the western and central part of the array, while large differences occur between observation and simulation close to the Canary archipelago. Possible causes for these differences are discussed.