Water mass characteristics in the equatorial North Atlantic: A section nominally along 6.5°N, July 2000

Abstract

[1] In July 2000, a transatlantic conductivity-temperature-depth/hydrographic section was occupied on board the Russian R/V Akademik Ioffe in the northern equatorial region from 9°26

Anthropogenic CO2 changes in the Equatorial Atlantic Ocean

“…The average [C ant À uC T 0 ] in the lNADW ranges from 5.4 ± 0.2 lmol kg À1 in the WB in 1993 to 8.2 ± 0.3 lmol kg À1 in the EB in 2010, and the mean [C ant À TTD] values are between 2.9 ± 0.1 lmol kg À1 in the EB in 1993 and 10.7 ± 0.3 lmol kg À1 in the WB in 2010. Once again, the pulse of LSW in the early 1990s (Lazier et al, 2002), together with the eastward branching of the DWBC (Mémery et al, 2000) and the northward cyclonic flow of the NADW into the south-eastern part of the Gambia Basin reported by Sarafanov et al (2007), could be the processes responsible for the C ant redistribution in the ER region observed during 2010. Nevertheless, no pattern could be easily described there because our estimates of [C ant ] were within the methodology uncertainty.…”

“…The lNADW layer is delimited by r 2 = 37.0 kg m À3 and r 4 = 45.9 kg m À3 (Johnson, 2008) and is characterized by waters that are progressively colder ($2-3°C) than uNADW. The AABW layer encloses waters below r 4 = 45.9 kg m À3 (Rhein et al, 1998;Sarafanov et al, 2007).…”

“…Eastward of the MAR, we differentiated the Eastern Ridge (ER) region, from 32.5°W to 21°W (Sierra Leone ridge), and the Eastern Boundary (EB) region, from 21°W to the African coast ($15°W), in order to distinguish between the Gambia abyssal plain and the Sierra Leone basin (Arhan et al, 1998). The density layers were selected according to the main water masses present in the Equatorial Atlantic Ocean (Tsuchiya et al, 1994;Arhan et al, 1998;Stramma and England, 1999;Stramma and Schott, 1999;Mémery et al, 2000;Brea et al, 2004;Sarafanov et al, 2007;Murata et al, 2008;Herraiz-Borreguero and Rintoul, 2011).…”

Atlantic Meridional Overturning Circulation at 14.5° N in 1989 and 2013 and 24.5° N in 1992 and 2015: volume, heat, and freshwater transports

“…3e and 4e). Previous studies have also shown that at 7.5 • N in the Atlantic, warming occurred in the intermediate layer (500-2000 m) through comparison of hydrographic data measured in 1957(Arhan et al, 1998Sarafanov et al, 2007Sarafanov et al, , 2008, and a significant decrease in the northward AAIW transport at this latitude (Hernández-Guerra et al, 2014). Schmidtko and Johnson (2012) further showed warming and salinification trends in the AAIW core in the tropical North Atlantic since the mid-1970s.…”

Atlantic meridional overturning circulation at 14.5° N and 24.5° N during 1989/1992 and 2013/2015: volume, heat and freshwater fluxes

“…3e and 4 e). Previous studies have also shown that at 7.5° N in the Atlantic, warming occurred in the intermediate layer (500-2000 m) through comparison of hydrographic data measured in 1957(Arhan et al, 1998Sarafanov et al, 2007Sarafanov et al, , 2008, and a significant decrease of the northward AAIW transport at this latitude (Hernández-Guerra 5 et al, 2014). Schmidtko and Johnson (2012) further showed warming and salinification trends of the AAIW core in the tropical North Atlantic since the mid-1970s.…”