Annual cycle and destruction of Eighteen Degree Water

TitleAnnual cycle and destruction of Eighteen Degree Water
Publication TypeJournal Article
Year of Publication2016
AuthorsBillheimer S., Talley LD
JournalJournal of Geophysical Research-Oceans
Date Published2016/09
Type of ArticleArticle
ISBN Number2169-9275
Accession NumberWOS:000386913200003
Keywordsannual variability; atmosphere; circulation; diapycnal diffusivity; Eighteen degree water; evolution; gulf; gulf-stream; Mixing; ocean; Potential vorticity; restratification; stream; subtropical mode water; variability; western north-atlantic

Eighteen Degree Water (EDW), the subtropical mode water of the western North Atlantic, is a voluminous, weakly stratified upper ocean water mass that acts as a subsurface reservoir of heat, nutrients, and CO2. This thick layer persists throughout the year, but nearly half of its volume is dispersed or mixed away, diffusing its properties into the thermocline, from the time it outcrops in winter until it is renewed the following year. CTD observations from Argo profiling floats and acoustically tracked, isothermally bound profiling floats are used to quantify EDW destruction rates and investigate the relevant processes responsible for the large annual cycle of EDW. EDW destruction occurs primarily at the top of the EDW layer, with the highest EDW destruction rates occurring during early summer. Slower, steadier EDW destruction is observed in early winter. EDW destruction is dominated by 1-D vertical diffusion, while mesoscale, along-isopycnal stirring is also significant, explaining approximately 1/3 of the total annual EDW destruction. Destruction via along-isopycnal processes is more prevalent near the Gulf Stream than in the southern Sargasso Sea, due to higher potential vorticity gradients and enhanced mesoscale activity.

Short TitleJ Geophys Res-Oceans
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