The influence of the mid-Atlantic ridge upon the circulation and the properties of the Mediterranean water southwest of the Azores
Joyce, Terrence M.
MetadataShow full item record
LocationCentral North Atlantic Ocean
KeywordMediterranean water southwest of the Azores; CTD section across the mid-Atlantic Ridge; Frontogenesis by horizontal shears; Knorr (Ship : 1970-) Cruise KN66
The warm, salty water influenced by the Mediterranean outfow can be observed at mid-depth throughout the Central North Atlantic Ocean. Katz (1970) first noted that rather than a gradual salinity decrease away from the source, large changes were observable over major topographic features such as the mid-Atlantic Ridge, despite the fact that the topography presented no direct physical barrier to the core layer. Two mechanisms are considered which can account for this sub-surface frontal transition: variable eddy diffusivity and horiontal shear induced by submarine topography. The structure of the actual geostrophic currents and water masses southwest of the Azores is explored with CTD, XBT, and float data collected in June 1977 aboard the R.V. Knorr. A CTD section normal to and crossing the ridge axis near 35N, 35W shows the thermocline to be domed up 200 m over the ridge axis compared with stations 200 km to either side. At 1000 meters depth a change in salinity of nearly 0.15% in the Mediterranean Water is observed to occur over a horizontal distance of 100-150 km, and is located west of the ridge near 38N and over the ridge axis near 34N. Near this transition two neutrally buoyant floats were tracked for a period of a day. CTD stations around and over a float at 810 meters depth showed the temperature and salinity intrusions to persist with time and horiontal space scales in excess of 15 hours and 4 km. If the currents observed SW of the Azores are representative of the general circulation of the region, they not only explain the water mass structure in the thermocline and Mediterranean Water but also point out that the historical data base of zonal hydrographic sections does not adequately resolve the baroclinic structure.
Originally published in Journal of Marine Research 39 (1981): 31-52
Showing items related by title, author, creator and subject.
Slope water, Gulf Stream, and seasonal influences on southern Mid-Atlantic Bight circulation during the fall-winter transition Rasmussen, Linda L.; Gawarkiewicz, Glen G.; Owens, W. Brechner; Lozier, M. Susan (American Geophysical Union, 2005-02-16)Observations from autumn, 2000, near the shelfbreak front in the Middle Atlantic Bight are used to describe the transition from stratified summer conditions to well-mixed winter conditions over the shelf. During the ...
Silva, Monica A.; Prieto, Rui; Cascao, Irma; Seabra, Maria I.; Machete, Miguel; Baumgartner, Mark F.; Santos, Ricardo S. (2013-02)Cetaceans living in offshore waters are under increasing pressure from anthropogenic activities. Yet, due to the lack of survey effort, relatively little is known about the demography or ecology of these populations. ...
Zhang, Weifeng G.; Gawarkiewicz, Glen G. (John Wiley & Sons, 2015-09-30)Onshore intrusions of offshore waters onto the Mid-Atlantic Bight shelf can greatly affect shelf circulation, biogeochemistry, and fisheries. Previous studies have concentrated on onshore intrusions of slope water. Here ...