High resolution profiler study of deep mixing in the Romanche fracture zone

Abstract

Between November 20 and December 10, 1994, studies of the deep mixing processes in the Romanche Fracture Zone (RFZ) of the Mid-Atlantic Ridge were conducted from the French research vessel N/O le Noroit. Oceanographers from France and the U.S. worked together to acquire the unique data obtained on this expedition. The cruise departed from and returned to Dakar, Senegal. Prior to the work in the RFZ, a sediment trap was recovered and returned to port. Two HRP engineering test dives were completed on the way to the fracture zone. The next week and a half was spent profiling with the HRP and CTD along the channel of the RFZ to identify regions of especially intense mixing. After that, two trans-equatorial sections were done with the HRP to examine the structure and intensity of the equatorial jets. The presence of bottom intensified flow to the east along the RFZ and enhanced mixing of Antarctic Bottom Water were both observed. Based on the measurements obtained during this experiment, transport through the RFZ is estimated to be 1 Sv. The work at sea, instrumentation, data return and some preliminary results are presented in this report.