The Porcupine Abyssal Plain Sustained Observatory (PAP-SO) is a fixed-point, open-ocean, scientific observatory located at 4,850m depth in the Northeast Atlantic.

PAP-SO is coordinated by the National Oceanography Centre.

Operating since 1985, this is one of a small number of oceanic sites that have achieved time series datasets to full ocean depth over several decades, providing key information for the assessment of long-term change in the ocean and its ecosystems.