Tracing Southwest Pacific Bottom Water using potential vorticity and helium-3

• Published in: Journal of Physical Oceanography
• Main Authors: Downes, SM, Key, RM, Orsi, AH, Speer, KG, Swift, JH
• Format: Article in Journal/Newspaper
• Language: English
• Published: Amer Meteorological Soc 2012
• Subjects: Earth Sciences; Oceanography; Physical Oceanography; Antarctic; Drake Passage; Pacific; The Antarctic; Antarc*
• Online Access: https://doi.org/10.1175/JPO-D-12-019.1; http://ecite.utas.edu.au/103127

This study uses potential vorticity and other tracers to identify the pathways of the densest form of Circumpolar Deep Water in the South Pacific, termed Southwest Pacific Bottom Water (SPBW), along the 28.2 kg m −3 surface. This study focuses on the potential vorticity signals associated with three major dynamical processes occurring in the vicinity of the PacificAntarctic Ridge: 1) the strong flow of the Antarctic Circumpolar Current (ACC), 2) lateral eddy stirring, and 3) heat and stratification changes in bottom waters induced by hydrothermal vents. These processes result in southward and downstream advection of low potential vorticity along rising isopycnal surfaces. Using δ 3 He released from the hydrothermal vents, the influence of volcanic activity on the SPBW may be traced across the South Pacific along the path of the ACC to Drake Passage. SPBW also flows within the southern limb of the Ross Gyre, reaching the Antarctic Slope in places and contributes via entrainment to the formation of Antarctic Bottom Water. Finally, it is shown that the magnitude and location of the potential vorticity signals associated with SPBW have endured over at least the last two decades, and that they are unique to the South Pacific sector.