The 2019 Fridtjof Nansen Medal is awarded to Anne-Marie Tréguier for leading contributions to the numerical modelling of the eddying ocean from the global to the regional scale, and for crucially advancing the understanding of the influence of mesoscale eddies.
Over the past three decades, Anne-Marie Tréguier has made diverse and important advances to ocean dynamics. These advances have greatly contributed to the present understanding of the role of ocean mesoscale eddies in the large-scale ocean circulation and have made possible the use of realistic ocean models to understand how fine-scale dynamical processes influence the large scale. Her early work on the influence of the bottom topography on eddy processes brought first evidence of the role of standing eddies in the momentum balance of the Antarctic Circumpolar Current.
She successfully promoted numerical modelling as a framework relevant to studying the greatly under-sampled eddy-scale processes and their influence of the large-scale circulation, since, as she argued, numerical modelling had the capability to be the bridge between in-situ observations (coarse and heterogeneous) and satellite observations (limited to the ocean surface). By developing innovative analytical methods of numerical model outputs to make it possible to understand fine-scale dynamics, she achieved remarkable results in demonstrating the importance of mesoscale eddies and their parameterisation. Her publications on the role of ocean eddies on the meridional overturning and the meridional transports of heat and freshwater are a major contribution to the present perception of the importance of eddies in climate.
Tréguier’s enthusiasm and deep interest in science are truly palpable. She is gifted with the ability to take a complex problem and clearly outline the steps that one needs to take to solve it. This is necessary when interpreting complex ocean numerical models. Her work over the last three decades covers ocean modelling end-to-end with contributions to theory, numerical algorithms, and operationalisation of ocean models. The work goes across the scales from sub-mesoscale to climate and different regions spanning all ocean basins.
Tréguier is recognised as a leading scientist in the worldwide ocean modelling community and is regularly asked to contribute to the leadership of international programs. She has shown her strong leadership capabilities in the coordination between European modelling groups. These projects promote the development and use of realistic eddying ocean models that perform eddy-permitting/resolving global ocean/sea-ice numerical simulations over decades. This international coordination made it possible to address mechanisms that drive the variability of water masses and the oceanic circulation, highlighting the importance of features such as topographic effects, mesoscale eddies and small-scale mixing processes on the large-scale circulation and its variability. Tréguier’s coordination work was significant in making the NEMO modelling framework a community model in Europe, now used by many climate centres and the Copernicus marine services.
Tréguier is known for her generosity and dedication toward colleagues and students; she has supervised many doctoral and masters students, leading many of them to distinguished careers. When we say today that our science has advanced to the point when ocean modelling can be considered as the main tool for understanding the ocean general circulation, we can also say very confidently that Anne-Marie Tréguier is one who critically and fundamentally contributed to this advance.