Transport of Deep and Bottom Waters through the Mid-Atlantic Ridge in the Vema Fracture Zone

Abstract

This paper addresses changes of Antarctic Bottom Water (AABW) transport through the Vema Fracture Zone based on direct measurements and Glorys12v1 reanalysis. Instrumental measurements of currents and other principal hydrological characteristics were carried out during the 45th cruise of the R/V Akademik Nikolaj Strakhov in November 2019. According to the current velocity measurements in 2019, the transport in the Vema Fracture Zone is 0.9 Sv. Moreover, based on the distribution of dissolved oxygen concentration, it is more correct to consider the isotherm 1.7°С rather than 2°С as the upper boundary of the AABW. The reanalysis showed very good agreement with direct measurements. The average transport of bottom water during the reanalysis period is 0.66 Sv. In general, there is a tendency towards an increase in both transport and temperature over the 25-year period covered by reanalysis. The measurements of the bottom water temperature during twenty successive samplings showed changes from 1.36 to 1.41°С within a day. This interval almost completely covers the entire range of values observed in previous years.