Die Topographie und die hydrographischen Verhältnisse unterhalb von 2000m Tiefe im Gebiet der Romanche-Bruchzone

• Main Authors: Tomczak, Gerhard, Annutsch, Ralph
• Format: Article in Journal/Newspaper
• Language: German
• Published: Bornträger 1970
• Subjects: Antarctic; Mid-Atlantic Ridge; Antarc*
• Online Access: https://oceanrep.geomar.de/id/eprint/56353/; https://oceanrep.geomar.de/id/eprint/56353/1/Tomczak_M_1970_A_2.pdf; https://oceanrep.geomar.de/id/eprint/56353/2/Karte%20no%207%201%20-%20Kopie.pdf; https://oceanrep.geomar.de/id/eprint/56353/3/Karte%20No%207%202%20-%20Kopie.pdf

During the "Atlantic Expedition" in 1965 (IQSY) a comprehensive bathymetric survey and a few hydrographic stations were made by R.V. "Meteor" in the equatorial region of the Mid-Atlantic Ridge. The survey results are shown in a bathymetric chart covering the western parts of the Romanche- and Chain Fracture Zones. West fo the original Romanche Trench another deep trench with a medium depth of 6000 m was discovered. The maximum sounding obtained was 7028 m. Both trenches apparently belong to the same fracture zone, but are distinctly separated from each other. The western boundary of the trench against the Brasil Basin is formed by a sill rising to a depth of about 4400 m. The serial hydrographic observations give some indications of the flow of the cold Westatlantic deep watet in the fracture zone area and its influence on the hydrographic conditions in the East-Atlantic Basin. The upper limit of the nearly homogenious Westatlantic bottom water with an Antarctic component lies in about 4400 m. The water mass entering the system of trenches of the Romanehe Fracture Zone over the western sill originates from the lower part of the discontinuity layer lying above the bottom watet. Potential temperatures of 0.6 °C were the lowest observed by "Meteor" in the western trench. There seems to be a remarkable tongue of relatively high salinity and a minimum of oxygen in the deep watet of this trench. At present we can only speculate upon the origin of this highly saline deep water tongue underneath the eastward moving relatively thin layer of less saline Westatlantic deep watet. In the range of the sill separating both trenches a lee-wave is indicated by the distribution of salinity and oxygen, which implies a vertical transport of water masses. Caused by this transport it is assumed that relatively cold watet may be lifted temporarily to a depth, where it can pass the northbounding ridge, thus getting directly into the Sierra Leone Basin. In the original Romanche Trench the cold Westatlantic deep water seems to fill the ...