Climate change and the associated sea warming will profoundly reshape marine ecosystems globally. Numerous species will experience range shifts as populations track ideal conditions and are replaced by other species adapted to warmer waters. Alternatively, some species may have enough evolutionary potential to adapt to changing environmental conditions. As a case in point, the Atlantic herring (Clupea harengus), a key species of pelagic ecosystems, is characterised by large populations numbering billions of individuals and by high overall genetic diversity. It is also known for its dynamic population history and episodic local population invasions. Moreover, herring have a wide distribution and occupy the contrasting niches of the Atlantic Ocean and Baltic Sea. Yet, it is not clear to what degree plasticity and genetic variation contribute to the adaptations to various environments. Here, we propose to test this question by using a temporal genomics approach relying on comparisons of historical and modern genomes forward simulations. Access to a comprehensive genomic dataset of modern herrings and to historical samples dating back to the 1400s offer an unprecedented opportunity to examine past population dynamics in response to past environmental changes and predict its future response to warming seas. Ultimately, this temporal transect analysis will provide essential information for future planning of sustainable herring fisheries in the North Atlantic and Baltic seas.