Mediterranean Outflow Water characteristics in the Northeast Atlantic in 2019 and 2021.

The characteristics of Mediterranean Outflow Water (MOW) in the Northeast Atlantic were obtained during the 43^rd cruise of the R/V Akademik Nikolaj Strakhov (October 2019) and the 59^th cruise of the R/V Akademik Ioffe (September 2021) using CTD measurements. MOW is transformed Mediterranean Sea Water flowing down the slopes of the Strait of Gibraltar into the Gulf of Cadiz, where it mixes with underlying North Atlantic Central Water. MOW spreads at water depths between 500–1500 m in the eastern North Atlantic and is characterized by higher temperatures and salinities than other ambient water masses. In 2019 and 2021 MOW was located at depths of about 700–1500 m. The temperature in the core of MOW was in the range of 9.5–11.5 °C, while in 2019 both temperature and salinity were higher than in 2021. The salinity in the core was 36.15 psu in 2019 and 36.08 psu in 2021. The comparison of MOW characteristics obtained in 2019 and 2021 with data obtained in cruises in 1993, 2001 and 2005 from the CLIVAR and Carbon Hydrographic Data Office (https://cchdo.ucsd.edu/) showed that the maximum salinity values were observed in September 1993 and reached 36.17 psu. The minimum value of this parameter in the core of MOW was recorded in April 2001 and was 36.03 psu. According to the data of the 1993–2019 expeditions, the maximum salinity was noted at a depth of 1000–1100 m. In 2021, the core of MOW was slightly deeper — about 1150 m. The temperature in the MOW core in all studied years was in the range of 11.1–11.3 °C, with the exception of 2001, when the maximum temperature in the core was about 10.9 °C.

Acknowledgements

The financing of the expedition and the primary processing of the data obtained on the 59^th cruise of the R/V Akademik Ioffe were carried out at the expense of the state assignment of IO RAS № 0128–2021–0012. The analysis and interpretation of the data were supported by the Russian Science Foundation (project no. 21–77–20004).