Modification of North Atlantic Deep Water by Pacific/Upper Circumpolar Deep Water in the Argentine Basin

• Published in: Geophysical Research Letters
• Main Authors: S. V. S. Brand, C. J. Prend, L. D. Talley
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2023
• Subjects: Geophysics. Cosmic physics; QC801-809; NADW; North Atlantic Deep Water; North Atlantic; Southern Ocean
• Online Access: https://doi.org/10.1029/2022GL099419; https://doaj.org/article/7c3dc581724244268c8d04dc98cc21f2

Abstract Much of the salty, high oxygen North Atlantic Deep Water (NADW) leaving the Atlantic flows through the Argentine Basin, where it is diluted by fresher, low oxygen Circumpolar Deep Water (CDW). This mixing of deep water masses is often overlooked in the zonally averaged description of the overturning circulation. Here, we show that intense mixing occurs along the western boundary: (a) extreme, isolated oxygen/temperature anomalies recorded by three autonomous biogeochemical floats suggest that subsurface eddies can inject relatively unmodified CDW far into the northwestern Argentine Basin, and (b) moderate, numerous temperature/salinity anomalies indicate a mixing zone from Rio Grande Rise to the Malvinas Current. This western eddy pathway shortcuts the gyre‐scale cyclonic route for CDW inferred from most previous studies. Significantly, CDW dilution of NADW affects the properties of deep waters that upwell in the Southern Ocean, and hence the connection between Northern and Southern Hemisphere polar climates.