Discovery Sails to the Porcupine Abyssal Plain

November, 2020

The RRS Discovery sets sail on 10/11/2020 on its second science cruise since the coronavirus pandemic put the research ship programme on hold. This time a limited number of scientists and technicians are travelling to the Porcupine Abyssal Plain Sustained Observatory (PAP-SO) in the North East Atlantic at 49°N, 16°W where the water is 4850 m deep.

The PAP-SO is a long-running open-ocean time-series study site with a focus on biogeochemistry through the full water column and the connections between processes at the surface and seabed. The Met Office provide the largest most complex mooring at the PAP-SO where NOC instruments record Essential Ocean Variables from atmosphere to 1000m. Funded by NERC through CLASS NOC scientists visit PAP-SO every year to take samples, make new observations and service the infrastructure.

This year the regular spring/summer visit to PAP-SO was delayed because of the pandemic but it is important to ensure data and samples are recovered for analysis and interpretation, minimising the impact on the time series. It will be a challenging time of year to do this with high winds and waves expected.

Part of the infrastructure, a large surface buoy, became detached from its mooring during Hurricane Epsilon shortly before DY116 . It was recovered by the FS Maria S. Merian. However, thisis just one component of the observatory and other moorings need to be recovered and if weather conditions allow, replaced with new ones.

One of the moorings is a set of sediment traps at different depths in the water column that collect sinking particles. These particles originate in the surface waters and provide a food source to animals that live in the deep sea. So far the PAP-SO sediment traps have provided a thirty-year dataset to study carbon cycling within the water column in the North East Atlantic (The abyssal seabed at PAP-SO and its inhabitants, that feed on material that has arrived from the surface, are observed with a time lapse camera called BATHYSNAP that takes photographs every eight hours.  BATHYSNAP will be recovered as part of the DY116 programme.

If weather conditions and sea state allow, a new buoy will be deployed at PAP-SO to replace the one that detached before the cruise.

The buoy can be seen in here being loaded onto Discovery.

As well as working with the moorings the PAP-SO scientists will use the CTD to calibrate the instruments recovered from the moorings and collect water samples. It is unusual to be sampling at PAP-SO in November so DY116 provides an interesting opportunity to add a seasonal dimension to the work by sampling a water column, well-mixed to several hundred meters and study carbon and nutrients at deeper depths.

The transit to PAP-SO from Southampton passes by Whittard Canyon, another CLASS study site. To support the ongoing work at Whittard Canyon DY116 plans to recover another sediment trap from the site so the data can be worked on to inform future research there. We will be busy measuring the surface ocean between the two sites, testing new instrumentation for carbon dioxide measurements As these are autonomous they will continue to give us information on the uptake of this greenhouse gas, whatever the weather may hold for us.