Concentration of dissolved iron in the oxygen minimum zone off San Esteban sill, Gulf of California

Abstract

Dissolved iron (Fed) concentrations are reported for the Gulf of California oxygen minimum zone (OMZ), which was located in front of San Esteban sill, between Subtropical Subsurface Water (SSW) and Pacific Intermediate Water. Mean Fed concentration in the OMZ was 3.84 ± 2.48 nM, with minimum and maximum values of 1.48 and 10.02 nM. These concentrations are higher and are enriched in relation to the Tropical Northeast Pacific Ocean OMZ (0.25–1.2 nM), whose waters enter the gulf through SSW. Sediment resuspension and Fed-enriched waters cause the observed Fe increase at the stations located near San Esteban sill. On the other hand, the relatively lower Fed concentrations found at the stations farthest from the sill are the result of denitrification in the suboxic zone.