Grant: Discovery Grants Program - Individual

During the last 3 decades, the Arctic Ocean has lost 50% of its permanent sea ice cover, exposing more surface waters to direct solar radiation. This phenomenon stimulates light-driven carbon processes: primary production by phytoplankton and photo-oxidation of dissolved organic matter (DOM). While the stimulation of primary producers by increased light availability has been recently documented, the impacts of this radiative forcing on photochemical oxidation of DOM and the net balance between light-driven carbon fluxes has received little attention thus far. Indeed, DOM in the Arctic Ocean surface originates largely from northern terrestrial ecosystems, which store nearly one third of global soil organic carbon. These ecosystems are currently experiencing important biogeochemical transformations under a warming climate, modifying the quantity and chemical character of terrigenous DOM, and the relative abundance of organic and inorganic nutrient inputs into the Arctic Ocean. Here I propose a framework to study the net balance between light-stimulated carbon fluxes in the Arctic Ocean using a diagnostic modelling approach. Therefore, a satellite-based spectral radiative transfer model for the coupled atmosphere-ocean system will be developed to quantify photochemical processes and assess trends in the net balance between primary production and photoooxidation. The parameterization of the photochemical models will be based on in situ observations gathered during research cruises in the Arctic Ocean. In order to predict variation in these photochemical parameters, their variability will be investigated in relation to observable or calculable environmental parameters. The novelty of this proposal resides in the synergetic use of various remotely sensed parameters of the environment merged within a diagnostic modelling approach to answer fundamental questions regarding climate change feedbacks. In particular, the work will aim to exploit the continuous ocean colour observations provided by satellites since 1997. The results should benefit studies focusing on remote sensing problems, global biogeochemical cycles, climate modeling, marine photosynthesis and DOM photochemistry.