Studies of physical data assimilation in the California Current and the development of a coupled physical and biogeochemical data assimilation system

Physical data assimilation is quite mature in oceanography. It is routinely practiced in operational and quasi-operational, global and regional systems throughout the world, and reanalyses providing estimates of previous ocean states are increasingly available. However, these activities leave a large portion of the desired ocean state, namely biogeochemical information, unknown. At UCSC we have developed a new method for assimilating biogeochemical information, that uses a log-transformation. This talk will review data assimilation efforts in oceanography, particularly 4-dimensional variational assimilation that is used at UCSC. I will highlight relationships between the physical state of the California Current and low-frequency variability in the Pacific that is accessible from a thirty year reanalysis. And I will finish with a discussion of the technical implementation and performance of our approach for biogeochemical data assimilation.