Oxygen Minimum Zone (OMZ) Dynamics Off Peru: Preliminary Insights From a Mooring and an Integrated Modelling Platform - The AMOP Project

In the current context of the ocean deoxygenation, OMZs are known to play a key-role on the evolution of climate (greenhouse gases) and on the ecosystems and fisheries (nitrogen loss, respiratory barrier, sulfidic events) at both local and global scales. One of the objectives of the AMOP (Activities of research dedicated to the Minimum of Oxygen in the eastern Pacific) project is to document the mechanisms associated with the OMZ variability from hourly to decadal timescales. The hypothesis is that the variability scale ranges are different at the oxycline compared to the OMZ core, and directly impact the OMZ recycling behavior acting as either a preservation or remineralization layer. Results from a mooring deployment off Callao put in evidence three main time scales of OMZ variability- intra daily, intra monthly and intra seasonally. A coupled model ROM-BioEBUS configuration of the Peruvian OMZ shows there is a marked longitudinal variability in the characteristics of the oxygen spectrum, indicative of a strong influence of mesoscale activity in shaping the OMZ structure offshore. Mooring data highlight oxygenation events occurring near the oxycline rather than within the core, and inducing a shift of the OMZ regime from organic matter preservation towards remineralisation.