Observing Processes impacting The sea Ice Mass balance from In Situ Measurements (OPTIMISM): from physics to its impacts on biology.

The OPTIMISM (2009-2013) project brought together a consortium of researchers and engineers from 5 French laboratories to document and study the evolution of sea ice thickness together with processes governing exchanges at the ocean-ice-atmosphere interface from in situ observations, a prerequisite to improve models’ parameterizations. The project was based on the development of an autonomous instrument (Ice-T buoy and Bear meteo mast) aimed at measuring the different parameters impacting the thermodynamical sea ice mass balance (sea ice thickness evolution, heat content and fluxes at its interfaces) . The Ice-T buoy was deployed for 4 consecutive years at the North Pole, in the frame of the international NPEO observatory, allowing to collect a valuable data set not only for process studies, but also to validate models and satellite observations. This project also aimed at investigating factors impacting the activity of polynya, which, as dense water formation regions ventilating the deep ocean, play a key role in the climate machinery. We have in particular collected an uninterrupted 2-year time series of measurements in the heart of the Storfjorden polynya, Svalbard. This effort fostered the development of a new multidisciplinary, international, observation program, involving paleo-oceanographers and biogeochemists in addition to physicists, based on a series of oceanographic cruises ( STeP program, Storfjorden Polynia multidisciplinary study) . This renewed OPTIMISM project, opening to a broader scientific community (including polar regions biogeochemists), envisions new technological developments on the one hand, enabling in particular to measure biological activity within and at the base of sea ice, in addition to physical parameters provided by the instrument (“green” Ice-T) or snow measurements based on miniaturized millimetric radar. Such technological developments require to be tested in arctic conditions before reaching an operational stage. The project aims, on the other hand, at pursuing the collection of data at the North Pole within the NPEO international consortium, which is highly motivated in the frame of an Arctic in rapid transition, as well as measuring greenhouse gases within the sea ice in Storfjorden, in relationship with the STeP campaigns.