RRS Discovery Cruise DY078/079, 06-28 May 2017, Southampton to Reykjavik. Extended Ellett Line 2017 occupation and OSNAP Rockall Trough mooring refurbishment cruise

Holliday, N.P. ORCID: https://orcid.org/0000-0002-9733-8002; et al, .. 2017 RRS Discovery Cruise DY078/079, 06-28 May 2017, Southampton to Reykjavik. Extended Ellett Line 2017 occupation and OSNAP Rockall Trough mooring refurbishment cruise. Southampton, National Oceanography Centre, 118pp. (National Oceanography Centre Cruise Report, 48)

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Abstract/Summary

Cruise DY078/079 (hereafter called DY078) was the 2017 occupation of the Extended Ellett Line (EEL) and the 2017 refurbishment cruise for the OSNAP Rockall Trough moorings (Overturning in the Subpolar North Atlantic Program). The core scientific objectives of DY078 were: To service (recover and re-deploy) the 3 UK OSNAP moorings and 1 ADCP lander in the Rockall Trough (RTWB1, RTWB2, RTEB2 and RTADCP1). To complete the Extended Ellett Line CTD/LADCP section across the eastern subpolar North Atlantic between Scotland and Iceland via the Rockall-Hatton Plateau. To collect and freeze nutrient samples from CTD stations for later analysis at SAMS To deploy four Argos floats for the UK Met Office. To recover one WHOI OSNAP glider and one SAMS EEL glider. To deploy one WHOI OSNAP glider and one SAMS OSNAP glider. To collect water samples for isotopic analysis at Edinburgh and Cardiff Universities To survey the seabed for sediments with the subbottom profiler. To collect underway water samples for microplastics analysis To survey for seabirds and marine mammals To communicate the cruise work through social media To collect underwater film footage for an artist The opportunistic objectives, to be completed if weather conditions allowed were: To collect megacores for palaeoceanographic and microplastics analysis To collect water column water samples for microplastics analysis To collect wind data for air-flow distortion analysis Almost all objectives were achieved, including the opportunistic ones, along with 7 extra CTD stations. The OSNAP ADCP lander was not recovered or re-deployed. All OSNAP moorings were previously deployed in 2014, refurbished in 2015 and 2016, and will be recovered in 2018. The moorings and the CTD profiles will be used to measure the mean and variability of the surface-to-seafloor currents, and to compute the volume, heat and freshwater transport within the currents. They are part of a large international programme, OSNAP (Overturning in the Subpolar North Atlantic Programme) which has other moorings in the Labrador Sea, Irminger Sea and Iceland Basin.