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RRS Discovery DY031

Cruise summary report

Cruise Info. 
Ship name (ship code)RRS Discovery (74EQ)
Cruise identifierDY031
Cruise period2015-05-29 — 2015-06-17
StatusCompleted
Port of departureSouthampton, United Kingdom
Port of returnLiverpool, United Kingdom
PurposeResearch
ObjectivesObjectives

- Complete the annual Extended Ellett Line CTD section
- Collect water samples for measuring biogeochemical properties including dissolved oxygen, nutrients, carbon and trace metals.
- Collect underway measurements of surface currents, surface temperature and salinity, bathymetry, surface meteorology.
- Complete epibenthic sled tows at a deep location in the central Rockall Trough.
- Launch a seaglider for a related research programme (near Rockall) which will stay in UK or international waters.
- Launch a second seaglider for a related research programme (near Iceland) which will operate in Iceland and Greenland waters.
- Deploy 2 Met Office Argo floats along the CTD section

The Extended Ellett Line is a hydrographic section between Iceland and Scotland that is occupied annually by scientists from the National Oceanography Centre (NOC) and the Scottish Association for Marine Science (SAMS), UK. The measurement programme began as a seasonally-occupied hydrographic section in the Rockall Trough in 1975, building on early surface observations made underway from ocean weather ships. In 1996 the section was extended to Iceland, sampling three basins: the Rockall Trough, the Hatton-Rockall Basin and the Iceland Basin. These three basins form the main routes though which warm saline Atlantic water flows northwards into the Nordic Seas and Arctic Ocean. The section crosses the eastern North Atlantic subpolar gyre; as well as the net northward flow there is a large recirculation of the upper layers as part of the wind-driven gyre. During its passage through the region, the warm saline water is subjected to significant modification by exchange of heat and freshwater with the atmosphere. The two deep basins (Rockall Trough and Iceland Basin) contain southward flowing dense northern overflow waters, and Labrador Sea Water in the intermediate layers.
Chief scientistN Penny Holliday (National Oceanography Centre, Southampton)
ProjectExtended Ellet line
Coordinating bodyNatural Environment Research Council (NERC)
Cruise reportRRS Discovery DY031 cruise report dy031.pdf (2.58 MB) 
Ocean/sea areas 
GeneralNorth East Atlantic Ocean (limit 40W)
SpecificRockall Trough, Hatton-Rockall Basin, Iceland Basin.
Track chartsRRS Discovery DY031 cruise track — dy031trk.pdf (0.12 MB) 
Measurements 
Physical oceanography 
Surface measurements underway (T,S)Quantity: activity duration in days = 20
Description: Underway thermosalinograph measurements of sea surface temperature, conductivity, transmittance and fluorescence.
Surface measurements underway (T,S)Quantity: number of stations = 81
Description: Discrete salinity samples taken from underway system intake. Measured on board.
Water bottle stationsQuantity: number of stations = 82
Description: Discrete salinity samples from CTD bottles. Measured on board.
CTD stationsQuantity: number of stations = 85
Description: Standard SBE9/11+ CTD package measuring conductivity, temperature, transmittance, turbidity, fluorescence and oxygen.
Transparency (eg transmissometer)Quantity: number of stations = 85
Description: Standard SBE9/11+ CTD package measuring conductivity, temperature, transmittance, turbidity, fluorescence and oxygen.
Transparency (eg transmissometer)Quantity: activity duration in days = 20
Description: Underway thermosalinograph measurements of sea surface temperature, conductivity, transmittance and fluorescence.
Current profiler (eg ADCP)Quantity: activity duration in days = 15
Description: Underway ADCP measurements, 150 kHz system.
Current profiler (eg ADCP)Quantity: number of stations = 84
Description: Downward looking lowered ADCP measurements, 300kHz system.
Current profiler (eg ADCP)Quantity: activity duration in days = 15
Description: Underway ADCP measurements, 75 kHz system.
Chemical oceanography 
OxygenQuantity: number of stations = 85
Description: Standard SBE9/11+ CTD package measuring conductivity, temperature, transmittance, turbidity, fluorescence and oxygen.
OxygenQuantity: number of stations = 40
Description: Discrete dissolved inorganic carbon (DIC) and Total Alkalinity (TA) samples taken from underway system intake. Measured on board.
OxygenQuantity: number of stations = 82
Description: Discrete dissolved oxygen samples taken from CTD bottles. Measured on board.
PhosphateQuantity: number of stations = 81
Description: Discrete nutrient samples taken from CTD bottles. Measured on board.
Total - PQuantity: number of stations = 81
Description: Discrete nutrient samples taken from CTD bottles. Measured on board.
NitrateQuantity: number of stations = 81
Description: Discrete nutrient samples taken from CTD bottles. Measured on board.
NitriteQuantity: number of stations = 81
Description: Discrete nutrient samples taken from CTD bottles. Measured on board.
Total - NQuantity: number of stations = 81
Description: Discrete nutrient samples taken from CTD bottles. Measured on board.
SilicateQuantity: number of stations = 81
Description: Discrete nutrient samples taken from CTD bottles. Measured on board.
AlkalinityQuantity: number of stations = 80
Description: Discrete Dissolved Inorganic Carbon (DIC) and Total Alkalinity (TA) from CTD bottles. Measured on board.
IsotopesQuantity: number of stations = 10
Description: Discrete oxygen isotope samples from CTD bottles
Other chemical oceanographic measurementsQuantity: number of stations = 80
Description: Discrete Dissolved Inorganic Carbon (DIC) and Total Alkalinity (TA) from CTD bottles. Measured on board.
Contamination 
Trace metalsQuantity: number of stations = 10
Description: Discrete trace metal measurements from CTD bottles. Measured on board.
Biology and fisheries 
Phytoplankton pigs (eg chlorophyll, fluorescence)Quantity: number of stations = 11
Description: Discrete phytoplankton samples from CTD bottles.
Phytoplankton pigs (eg chlorophyll, fluorescence)Quantity: number of stations = 85
Description: Standard SBE9/11+ CTD package measuring conductivity, temperature, transmittance, turbidity, fluorescence and oxygen.
Phytoplankton pigs (eg chlorophyll, fluorescence)Quantity: activity duration in days = 20
Description: Underway thermosalinograph measurements of sea surface temperature, conductivity, transmittance and fluorescence.
Phytoplankton pigs (eg chlorophyll, fluorescence)Quantity: number of stations = 42
Description: Discrete chlorophyll samples taken from CTD bottles. Measured on board.
Other biological/fisheries measurementQuantity: number of stations = 5
Description: Epibenthic sled tows.
Meteorology 
Routine standard measurementsQuantity: activity duration in days = 20
Description: Underway meteorology measurements of radiation, air temperature, wind speed and direction, relative humidity and air pressure.
Moorings, landers, buoys 
Physical oceanography 
Neutrally buoyant floats60° 30' 0" N  20° 0' 0" W — Argo float SN 7208
Neutrally buoyant floats59° 19' 59" N  18° 10' 0" W — Argo float SN 7207
Other physical oceanographic measurements62° 40' 0" N  19° 40' 0" W — Seaglider SG606
Other physical oceanographic measurements57° 57' 0" N  14° 34' 59" W — Seaglider SG603
Data held at BODC Get data
Discrete samples 
85  CTD frame plus rosette samplerTotal dissolved inorganic carbon (TCO2) concentration in the water column
Dissolved oxygen parameters in the water column
Phosphate concentration parameters in the water column
Salinity of the water column
Silicate concentration parameters in the water column
Nitrate concentration parameters in the water column
Metadata parameters
Alkalinity, acidity and pH of the water column
5  Epibenthic Sledge
147  Sample taken from ship's non-toxic supplyTotal dissolved inorganic carbon (TCO2) concentration in the water column
Alkalinity, acidity and pH of the water column