Characterization of "dead-zone" eddies in the eastern tropical North Atlantic

Abstract

Localized open-ocean low-oxygen "dead zones" in the eastern tropical North Atlantic are recently discovered ocean features that can develop in dynamically isolated water masses within cyclonic eddies (CE) and anticyclonic mode-water eddies (ACME). Analysis of a comprehensive oxygen dataset obtained from gliders, moorings, research vessels and Argo floats reveals that "dead-zone" eddies are found in surprisingly high numbers and in a large area from about 4 to 22°ĝ€N, from the shelf at the eastern boundary to 38°ĝ€W. In total, 173 profiles with oxygen concentrations below the minimum background concentration of 40ĝ€μmolĝ€kgĝ'1 could be associated with 27 independent eddies (10 CEs; 17 ACMEs) over a period of 10 years. Lowest oxygen concentrations in CEs are less than 10ĝ€μmolĝ€kgĝ'1 while in ACMEs even suboxic (