This open access book brings selected, peer-reviewed contributions presented at the Fifth Stochastic Transport in Upper Ocean Dynamics (STUOD) 2024 Workshop, held at INRIA in Rennes, France, September 23–26, 2024. Aimed to deliver new capabilities for assessing variability and uncertainty in upper ocean dynamics, this book provides decision-makers a means of quantifying the effects of local patterns of sea level rise, heat uptake, carbon storage, and change of oxygen content and pH in the ocean. Its multimodal monitoring will enhance the scientific understanding of marine debris transport, tracking of oil spills, and accumulation of plastic in the sea. All topics of these proceedings are essential to the scientific foundations of oceanography which has a vital role in climate science. Studies convened in this book focus on a range of fundamental areas, including:         •    Observations at a high resolution of upper ocean properties such as temperature, salinity, topography, wind, waves, and velocity.          •    Large-scale numerical simulations.          •    Data-based stochastic equations for upper ocean dynamics that quantify simulation error.          •    Stochastic data assimilation to reduce uncertainty. These fundamental subjects in modern science and technology are urgently required to meet the challenges of climate change faced today by human society. This proceedings book represents a lasting legacy of crucial scientific expertise to help meet this ongoing challenge, for the benefit of academics and professionals in pure and applied mathematics, computational science, data analysis, data assimilation, and oceanography. The STUOD project is supported by an ERC Synergy Grant and led by Imperial College London, the National Institute for Research in Computer Science and Automatic Control (INRIA), and the French Research Institute for Exploitation of the Sea (IFREMER).