Fast northward energy transfer in the atlantic due to agulhas rings

• Published in: Journal of physical oceanography Vol. 37; no. 9; pp. 2305 - 2315
• Main Authors: VAN SEBILLE, Erik, VAN LEEUWEN, Peter Jan
• Format: Journal Article
• Language: English
• Published: Boston, MA American Meteorological Society 01.09.2007
• Subjects: Changes; Earth, ocean, space; Energy conversion; Energy transfer; Exact sciences and technology; External geophysics; Marine; Ocean circulation; Oceanography; Physics of the oceans; Thermohaline structure and circulation. Turbulence and diffusion; Travel time; Wave energy; Atlantic Ocean; Agulhas current; Mid-Atlantic Ridge; United States > US; AN, North Atlantic; ISW, West Indian Ocean, Agulhas Current; AS, South Atlantic; A, Mid-Atlantic Ridge; Vortex shedding; Obstacle wave interaction; two-layer models; energy transfer; digital simulation; Topographic wave; Ocean model; Baroclinic mode; Ring current; Energy conversion; thermohaline circulation; Western boundary current; Barotropic mode; ocean circulation
• ISSN: 0022-3670; 1520-0485
• DOI: 10.1175/JPO3108.1

Abstract The adiabatic transit time of wave energy radiated by an Agulhas ring released in the South Atlantic Ocean to the North Atlantic Ocean is investigated in a two-layer ocean model. Of particular interest is the arrival time of baroclinic energy in the northern part of the Atlantic, because it is related to variations in the meridional overturning circulation. The influence of the Mid-Atlantic Ridge is also studied, because it allows for the conversion from barotropic to baroclinic wave energy and the generation of topographic waves. Barotropic energy from the ring is present in the northern part of the model basin within 10 days. From that time, the barotropic energy keeps rising to attain a maximum 500 days after initiation. This is independent of the presence or absence of a ridge in the model basin. Without a ridge in the model, the travel time of the baroclinic signal is 1300 days. This time is similar to the transit time of the ring from the eastern to the western coast of the model basin. In the presence of the ridge, the baroclinic signal arrives in the northern part of the model basin after approximately 10 days, which is the same time scale as that of the barotropic signal. It is apparent that the ridge can facilitate the energy conversion from barotropic to baroclinic waves and the slow baroclinic adjustment can be bypassed. The meridional overturning circulation, parameterized in two ways as either a purely barotropic or a purely baroclinic phenomenon, also responds after 1300 days. The ring temporarily increases the overturning strength. The presence of the ridge does not alter the time scales.