Deep and bottom currents in the Challenger Deep, mariana trench, measured with super-deep current meters

The bottom currents in the Challenger Deep, the deepest in the world, were measured with super-deep current meters moored at 11degrees22' N and 142degrees35' E, where the depth is 10915 m. Three current meters were set at 9687 m, 10489 m and 10890 m at the station in the center of the Challenger Deep for 442 days from 1 August 1995 to 16 October 1996. Although rotor revolutions in 60 minutes of recording interval were zero for 37.5% of the time, the maximum current at the deepest layer of 10890 m was 8.1 cm s(-1), being composed of tidal currents, inertia motion and long period variations. Two current meters were set at 6608 m and 7009 m at a station 24.9 km north of the center for 443 days from 31 July 1995 to 16 October 1996, and two current meters at 6214 m and 6615 m at a station 40.9 km south of the center for 441 days from 2 August 1995 to 16 October 1996. The mean flow at 7009 m depth at the northern station was 0.7 cm s(-1) to 240degreesT, and that at 6615 m depth at the southern station was 0.5 cm s(-1) to 267degreesT. A westward mean flow prevailed at the stations, and no cyclonic circulation with mean flows of the opposite directions was observed in the Mariana Trench at a longitude of 142degrees35' E. Power spectra of daily mean currents showed three spectral peaks at periods of 100 days, 28-32 days and 14-15 days. The peak at 100 day period was common to the power spectra.