RRS James Cook Cruise 71, 29 Apr - 12 May 2012. Porcupine Abyssal Plain: sustained ocean observation

The objective of the PAP observatory is to provide high temporal resolution (hours) of an increasing number of variables which are relevant from the perspective of the biology, physics and chemistry of the upper water column, the midwater and the underlying seabed. These observations are made over a relatively small spatial scale (30km) in the open ocean over a very flat area of seabed at a depth of 4800m. The site has been under examination for over 20 years and during that time, substantial changes have been observed in the benthic environment. The intention is to sustain and enhance all of these observations in order that a deeper understanding is obtained into the processes which operate; in particular the responses to the changes which are currently taking place in the global environment. The objective of the cruise was primarily to service the infrastructure required for continuous sustained observation, and to put these into context using observations from the ship which as yet cannot be carried out autonomously. The observatory comprises three autonomous platforms; (1) A moored meteorological buoy beneath which, at 30m depth, is a sensor frame carrying a wide range of sensors and samplers, (2) a sediment trap mooring with traps and current meters at 3000 and 4700m depth and (3) a Bathysnap benthic time lapse camera system. All of these were recovered and new or serviced platforms deployed for recovery after 12 months. The large amount of data are placed in the public domain as soon as quality checks have been completed. In addition to this various types of biological and biogeochemical sampling and experimentation was carried out in the water column and on the seafloor in their own right and to add value to the autonomous time series observations.