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RRS Discovery DY078 (DY079)

Cruise summary report

Cruise Info. 
Ship name (ship code)RRS Discovery (74EQ)
Cruise identifierDY078 (DY079)
Cruise period2017-05-06 — 2017-05-28
StatusCompleted
Port of departureSouthampton, United Kingdom
Port of returnReykjavík, Iceland
PurposeResearch
ObjectivesCruise 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

Most objectives were achieved, including the opportunistic ones, along with 7 extra CTD stations. The only objective not achieved is that the ADCP lander was not recovered, and its replacement was postponed for a later cruise.

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.
Chief scientistN Penny Holliday (National Oceanography Centre, Southampton)
ProjectUK OSNAP; Extended Ellet Line
Coordinating bodyNatural Environment Research Council (NERC)
Cruise reportRRS Discovery DY078 (DY079) cruise report dy078.pdf (30.43 MB) 
Ocean/sea areas 
GeneralNorth East Atlantic Ocean (limit 40W)
SpecificIceland Basin, Rockall Trough
Measurements 
Physical oceanography 
Surface measurements underway (T,S)Quantity: number of stations = 91
Description: Discrete salinity samples taken from underway system intake. Measured on board.
Surface measurements underway (T,S)Quantity: activity duration in days = 22
Description: Underway thermosalinograph measurements of sea surface temperature, conductivity, transmittance and fluorescence.
Water bottle stationsQuantity: number of stations = 64
Description: Discrete salinity samples from CTD bottles. Measured on board.
CTD stationsQuantity: number of stations = 81
Description: Standard SBE9/11+ CTD package measuring conductivity, temperature, transmittance and oxygen.
Transparency (eg transmissometer)Quantity: activity duration in days = 22
Description: Underway thermosalinograph measurements of sea surface temperature, conductivity, transmittance and fluorescence.
Transparency (eg transmissometer)Quantity: number of stations = 81
Description: Standard SBE9/11+ CTD package measuring conductivity, temperature, transmittance and oxygen.
Current profiler (eg ADCP)Quantity: activity duration in days = 22
Description: Underway ADCP measurements, 150 kHz system.
Current profiler (eg ADCP)Quantity: number of stations = 81
Description: Downward looking lowered ADCP measurements, Up + down-looking 300kHz system.
Current profiler (eg ADCP)Quantity: activity duration in days = 22
Description: Underway ADCP measurements, 75 kHz system.
Chemical oceanography 
OxygenQuantity: number of stations = 81
Description: Standard SBE9/11+ CTD package measuring conductivity, temperature, transmittance and oxygen.
PhosphateQuantity: number of stations = 72
Description: Discrete nutrient samples taken from CTD bottles. Frozen, to be measured at SAMS.
NitrateQuantity: number of stations = 72
Description: Discrete nutrient samples taken from CTD bottles. Frozen, to be measured at SAMS.
NitriteQuantity: number of stations = 72
Description: Discrete nutrient samples taken from CTD bottles. Frozen, to be measured at SAMS.
SilicateQuantity: number of stations = 72
Description: Discrete nutrient samples taken from CTD bottles. Frozen, to be measured at SAMS.
Biology and fisheries 
Phytoplankton pigs (eg chlorophyll, fluorescence)Quantity: activity duration in days = 22
Description: Underway thermosalinograph measurements of sea surface temperature, conductivity, transmittance and fluorescence.
Phytoplankton pigs (eg chlorophyll, fluorescence)Quantity: number of stations = 81
Description: Standard SBE9/11+ CTD package measuring conductivity, temperature, transmittance and oxygen.
Meteorology 
Routine standard measurementsQuantity: activity duration in days = 22
Description: Underway meteorology measurements of radiation, air temperature, wind speed and direction, relative humidity and air pressure.
Moorings, landers, buoys 
Physical oceanography 
Current meters57° 5' 53" N  9° 21' 18" W — UK OSNAP mooring RTADCP1 recovered. Water depth 947m. Current meter, microcat.
Current meters57° 28' 18" N  12° 18' 40" W — Mooring RTWB2 deployed on 11/05/2017
Current meters57° 28' 11" N  12° 42' 38" W — UK OSNAP mooring RTWB1 recovered. Water depth 1585m. Current meter, microcat.
Current meters57° 6' 1" N  9° 33' 49" W — Mooring RTEB1 deployed on 13/05/2017
Current meters57° 28' 9" N  12° 42' 20" W — Mooring RTWB1 deployed on 11/05/2017
Current meters57° 28' 4" N  12° 18' 43" W — UK OSNAP mooring RTWB2 recovered. Water depth 1799m. Current meter, microcat.
Current meters57° 6' 5" N  9° 33' 44" W — UK OSNAP mooring RTEB1 recovered. Water depth 1813m. Current meter, microcat.
Neutrally buoyant floats57° 21' 40" N  10° 21' 40" W — Met Office Argo float 8071 deployed on 17/05/2017
Neutrally buoyant floats60° 14' 47" N  19° 59' 4" W — Met Office Argo float 8072 deployed on 24/05/2017
Neutrally buoyant floats59° 24' 1" N  18° 24' 55" W — Met Office Argo float 8073 deployed on 23/05/2017
Neutrally buoyant floats57° 13' 58" N  10° 3' 1" W — Met Office Argo float 8070 deployed on 16/05/2017
Data held at BODC Get data
Discrete samples 
81  CTD frame plus rosette sampler
91  Sample taken from ship's non-toxic supply