How does Subantarctic Mode Water ventilate the Southern Hemisphere subtropics?

TitleHow does Subantarctic Mode Water ventilate the Southern Hemisphere subtropics?
Publication TypeJournal Article
Year of Publication2016
AuthorsJones D.C, Meijers A.JS, Shuckburgh E., Sallee J.B, Haynes P., McAufield E.K, Mazloff MR
JournalJournal of Geophysical Research-Oceans
Volume121
Pagination6558-6582
Date Published2016/09
Type of ArticleArticle
ISBN Number2169-9275
Accession NumberWOS:000386913200001
Keywordsanthropogenic carbon-dioxide; circulation; circumpolar current; climate model; coupled; global overturning circulation; intermediate water; modeling; north-atlantic; ocean; parameterization; Southern Ocean; Subantarctic Mode Water; subduction; thermocline; transport; ventilation
Abstract

In several regions north of the Antarctic Circumpolar Current (ACC), deep wintertime convection refreshes pools of weakly stratified subsurface water collectively referred to as Subantarctic Mode Water (SAMW). SAMW ventilates the subtropical thermocline on decadal timescales, providing nutrients for low-latitude productivity and potentially trapping anthropogenic carbon in the deep ocean interior for centuries. In this work, we investigate the spatial structure and timescales of mode water export and associated thermocline ventilation. We use passive tracers in an eddy-permitting, observationally-informed Southern Ocean model to identify the pathways followed by mode waters between their formation regions and the areas where they first enter the subtropics. We find that the pathways followed by the mode water tracers are largely set by the mean geostrophic circulation. Export from the Indian and Central Pacific mode water pools is primarily driven by large-scale gyre circulation, whereas export from the Australian and Atlantic pools is heavily influenced by the ACC. Export from the Eastern Pacific mode water pool is driven by a combination of deep boundary currents and subtropical gyre circulation. More than 50% of each mode water tracer reaches the subtropical thermocline within 50 years, with significant variability between pools. The Eastern Pacific pathway is especially efficient, with roughly 80% entering the subtropical thermocline within 50 years. The time required for 50% of the mode water tracers to leave the Southern Ocean domain varies significantly between mode water pools, from 9 years for the Indian mode water pool to roughly 40 years for the Central Pacific mode water pool.

DOI10.1002/2016jc011680
Short TitleJ Geophys Res-Oceans
Student Publication: 
No