Hydrological and hydrochemical haracteristics of the modified AABW in the Discovery Gap (Northeast Atlantic) in 2021.

Hydrological and hydrochemical characteristics of the Discovery Gap bottom water (deeper than 4000 m) were obtained during the 59^th cruise of the R/V Akademik Ioffe (October 2021). Discovery Gap is the narrow gap of 150 km long, 10–50 km wide, oriented from southwest to northeast in Azores–Gibraltar Fracture Zone (Northeast Atlantic). Water with a potential temperature of less than 2 °C (modified Antarctic Bottom Water (AABW)) and high silicon concentrations was detected in the Discovery Gap. The terminal point of propagation of modified AABW in the exit sill of the Gap (depth more than 4700 m). There was cyclonic circulation in the Discovery Gap Narrows (the narrowest point of the Discovery Gap, 10 km wide, located in the northeastern part of it): in the northeast direction of more than 14 cm/s speed and with the high phosphate concentrations (1.46-1.54 μmol/l), in the southwest direction of 6-8 cm/s speed and with a low phosphate content (1.39-1.40 μmol/l). The localization of the extrema of phosphorus concentrations correlates with the maximum flow velocities, which may be associated with advective processes.

Acknowledgments:

The expedition and the hydrochemical processing of the data received during the 59^th cruise of the R/V Akademik Ioffe was carried out with a support of the state assignment of the IO RAS (No. 0128-2021-0012), the hydrophysical measurements were supported by the Russian Science Foundation (project no. 21-77-20004).

We thank the crew of the R/V Akademik Ioffe for assistance, B.V. Chubarenko for valuable comments and E.I. Gmyrya for preparing the map.