F. Schütte et al.: Hidden vortices: near-equatorial low-oxygen extremes driven by high-baroclinic-mode vortices 129 
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Figure 5. Time series of observed (a) DO, (b) salinity, (c) eastward and (d) northward velocity from moored observations at 11° N/21° W 
ın the upper 300m as a 10d average (color shading). Black lines denote depth of potential density surfaces 26.5, 26.6 and 26.8 kg m”. 
Black-white dashed lines denote depths of DO sensors — in (a), (c) and (d) — and salinity sensors (in b). Gray bars with numbers 01-10 in 
che top of these panels denote time periods of low-DO events (#01 to #10). Note, that no velocity observations are available for low-DO 
events #05 and #06. Panels (e}-(h) show corresponding 2 d averaged time series for the 90 d time period around low-DO events #02 and #03. 
don of the meridional core position of the low-DO extremes, 
ut their extent was found with roughly 1° in latitude in maxi- 
mum. The low-DO cores vertically extended to the isopycnal 
09 = 26.5 kg m”? (150 m depth) and were separated from the 
deep OMZ by an intermediate DO maximum located at about 
09 =26.7kg m”? (between 200 and 300 m), which rules out 
a simple vertical displacement of the vertical gradient. 
https://doi.org/10.5194/os-22-119-2026 
We analyzed the distribution of zonal and meridional ve- 
locity at the depth of the DO minimum using an eddy identifi- 
cation algorithm as described in Sect. 3.3.1. Strikingly, 66 % 
(10 of 15) of the low-DO events could be related to HBVs, 
where radii were identified between 20 and 45km (average 
34km) (Table 1, Fig. 6b and d). The radii are substantially 
smaller than the typical mesoscale (first baroclinic Rossby 
radius of deformation) at these latitudes being at the order 
Ocean Sci... 22. 119-143. 2026