NOCEANIC · Key factors driving particulate organic matter fluxes and related nitrogen losses in the main anoxic oxygen minimum zones of the world oceans

Nitrogen loss fuelled by sinking particulate organic carbon (POC) is a key mechanism that drives biogeochemical cycles in anoxic oxygen minimum zones (OMZs). However, little is known about what controls this mechanism because of the challenges involved in observing it. Noceanic aims to improve current knowledge by exploiting – for the first time – time-series of optical proxies of POC and physicochemical data collected by autonomous profiling floats (i.e. “BGC-Argo”). This data acquired at unprecedented temporal and vertical resolution will generate new insights into the biogeochemical linkages between POC fluxes and N losses. Ultimately, Noceanic will contribute to reducing uncertainties in the mechanistic prediction of N losses and deepen understanding of the biogeochemical response of oceans to ongoing OMZs expansion. Noceanic will combine models, field and remote-sensing data. From field data, optical POC relationships will be tuned and then used to convert optical proxies of POC into POC fluxes. Remote-sensing data will be exploited to model surface POC formed by photosynthesis and assess its source of variability. From these elements, POC fluxes in anoxic OMZs (> 100 m) can then be translated into N losses. Finally, temporal changes in N losses will be explained in terms of the main factors driving the formation of POC and its export to anoxic OMZs. These innovative interdisciplinary activities will establish a two-way exchange of knowledge between the Researcher and the host institution, and enhance their European and international network of collaborators. An expected outcome of Noceanic is its impact on the European strategy for global ocean observations by promoting the inclusion of OMZs – a critical shift because OMZs expansion is affecting the oceans’ role in mitigating the Earth’s climate and the size of fish stocks, ultimately inflicting consequences on European society.