The Optical Signature of a Bottom Boundary Layer Ventilation Event in the Northern Gulf of Mexico's Hypoxic Zone

Abstract

Oceanographic observations in the northern Gulf of Mexico captured an unusual combination of atmospheric forcing and shelf frontal dynamics that brought about the surface ventilation of sediment-laden bottom waters. Colorimetric analysis of in situ optical data indicates a specific turquoise-white color signature for turbid and low-oxygen bottom waters that match a coincident shelf-wide feature detected in Moderate Resolution Imaging Spectroradiometer satellite true color images. The physical processes leading to this ventilation event are simulated using the Coupled Ocean Atmosphere Mesoscale Prediction System, which includes an integrated surface wave model. The combined model-data analysis suggests that low-oxygen, bottom water ventilation may occur episodically during boreal spring and summer in the northern Gulf of Mexico following the passage of high-energy atmospheric systems, and these events may be identified in the historical satellite record based on the unique bottom water optical characteristics.