"MyOcean is the first EU project dedicated to the implementation of the GMES Marine Core Service for ocean monitoring and forecasting. The consortium is preparing a new FP7 proposal to expand the pre-operational service and move to full operations in 2014. Due to the nature of the call, R&D activities are limited to short-term developments closely linked to the operational needs. We propose a project that will provide the necessary link to new developments in data assimilation to ensure that future operational systems make use of state-of-the-art data-assimilation and related analysis tools.A European network of expert teams in advanced data assimilation will extend existing modular data assimilation systems that have high flexibility in type of ocean model and assimilation method. Following specific design rules, new modules can be used in different modular systems. The systems will allow for efficient operational testing of the latest data assimilation methods, and quick comparison of assimilation methods for operational use. Furthermore, we will develop and implement modules that objectively determine the impact of existing and new observation types. Costumers of MyOcean products will be served by concentrating on data-assimilation methods that deliver probabilistic information on the products. To this end, existing ensemble methods will be included and new methods that allow for nonlinear and non-Gaussian systems will be developed.A dedicated web portal will be set up that allows access to validated products, including documented performances on a variety of test cases. Consolidated versions are made available to the science community and Marine Forecasting Centres with indications on best practise implementation.Workshops and summerschools on advanced assimilation methods and modular systems will ensure fast and efficient training to next generation oceanographers, ensuring world-leading operational oceanographic products for costumers and decision makers."