Tracing the North Atlantic Deep Water through the Romanche and Chain fracture zones with chlorofluoromethanes.

• Published in: Deep Sea Research Part I: Oceanographic Research Papers
• Main Authors: Messias, Marie-José, Andrié, Chantal, Mémery, Laurent, Mercier, Herlé
• Other Authors: Laboratoire d'océanographie dynamique et de climatologie (LODYC), Institut de Recherche pour le Développement (IRD)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), CEA- Saclay (CEA), Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Laboratoire de physique des océans (LPO), Institut de Recherche pour le Développement (IRD)-Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER)-Université de Brest (UBO)-Centre National de la Recherche Scientifique (CNRS)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 1999
• Subjects: [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Antarc*; Antarctic; NADW; North Atlantic Deep Water; North Atlantic
• Online Access: https://hal.science/hal-00271275; https://hal.science/hal-00271275/document; https://hal.science/hal-00271275/file/Messias1999.pdf; https://doi.org/10.1016/S0967-0637(99)00005-9

International audience Chlorofluoromethanes (CFMs) F-11 and F-12 were measured during August 1991 and November 1992 in the Romanche and Chain Fracture Zones in the equatorial Atlantic. The CFM distributions showed the two familiar signatures of the more recently ventilated North Atlantic Deep Water (NADW) seen in the Deep Western Boundary Current (DWBC). The upper maximum is centered around 1600 m at the level of the Upper North Atlantic Deep water (UNADW) and the deeper maximum around 3800 m at level of the Lower North Atlantic Deep Water (LNADW). These observations suggest a bifurcation at the western boundary, some of the NADW spreading eastward with the LNADW entering the Romanche and the Chain Fracture Zones. The upper core (σ1.5=34.70 kg m -3 ) was observed eastward as far as 5°W. The deep CFM maximum (σ4=45.87 kg m -3 ), associated with an oxygen maximum, decreased dramatically at the sills of the Romanche Fracture Zone: east of the sills, the shape of the CFM profiles reflects mixing and deepening of isopycnals. Mean apparent water "ages" computed from the F-11/F-12 ratio are estimated. Near the bottom, no enrichment in CFMs is detected at the entrance of the fracture zones in the cold water mass originating from the Antarctic Bottom Water flow.