The 14C reservoir age (MRA) for the sea surface is a tracer of air-sea gas exchange and mixing of young carbon derived from the atmosphere with older carbon from subsurface waters. These processes are related to climate, ocean and carbon cycle parameters that varied over the past 50,000 years. The MARCARA project focuses on documenting and modelling the MRA at key locations of the three main oceans. We will generate 14C ages on ultra-small samples by means of the AixMICADAS spectrometer equipped with a versatile solid & gas ion source. This approach will allow us to better quantify MRA and avoid, or correct for, various biases. For numerical modelling, we will use a high-resolution unstructured mesh approach to zoom into the regions of interest and with data assimilation of both marine and atmospheric 14C data. Our data-model integration will be focused on the last deglaciation and abrupt climate changes such as Heinrich stadials and Dansgaard-Oeschger interstadials.