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RRS Discovery D312

Cruise summary report

Cruise Info. 
Ship name (ship code)RRS Discovery (74E3)
Cruise identifierD312
Cruise period2006-10-11 — 2006-10-31
StatusCompleted
Port of departureReykjavík, Iceland
Port of returnGovan, United Kingdom
PurposeResearch
ObjectivesUK oceanographers have been making repeated measurements on a short section across the Rockall Trough, since 1975. The section consists of a series of stations from the Scottish continental shelf to Rockall. The time series was established by David Ellett and was thus called the "Ellett Line". The Ellett line is one of a relatively small number of high quality physical time series in the North Atlantic Ocean and is important for monitoring oceanic climate variability.
Since 1996 NOCS and SAMS have been occupying an extended version of the Ellett Line that runs all the way to Iceland. The Extended Ellett Line is important oceanographically because it completes the measurements of the warm saline water flowing into the Nordic Seas from the eastern North Atlantic. It also monitors around half of the returning deep and cold current, the overflow water (the rest returns to the Atlantic via the Denmark Strait to the west of Iceland).
There is little added cost, either in time or financially, in making a number of biogeochemical measurements using water samples from the hydrographers' CTD stations. Thus, recently, the scientific interests in the Extended Ellett line have become more multidisciplinary; the 2006 occupation was no exception. Samples were filtered for POC, HPLC studies and trace aluminium concentration determination, in addition some extra time was found for a number of zooplankton net hauls.
Chief scientistJohn T Allen (National Oceanography Centre, Southampton)
ProjectThe extended Ellet line
Coordinating bodyNatural Environment Research Council (NERC)
Cruise reportRRS Discovery D312 cruise report d312.pdf (2.28 MB) 
Ocean/sea areas 
GeneralNorth East Atlantic Ocean (limit 40W)
SpecificRockall Trough and Iceland Basin
Track chartsRRS Discovery D312 cruise track — d312trk.pdf (0.03 MB) 
Measurements 
Physical oceanography 
Water bottle stationsQuantity: number of samples = 634
Description: H09: SBE9/11+CTD system with 24 10l OTE Bottles, SBE9+ Underwater Unit09P37898-0782, SBE11+ Deck Unit 11P-19817-0495, SBE32 24way Rosette 32-0344, SBE Pressure: 94756. Calibrated on: 15 Apr 2004 Guildline Autosal salinometer (model 8400B, serial no. 60839) and OSIL's Autosal software, Softsal used to get salinity samples.
CTD stationsQuantity: number of profiles = 65
Description: H10: Primary T & C Sensors (On Vane). SBE3 Temperature: 03P-2728 Calibrated on 15/03/06, SBE4 Conductivity:04C-2851, calibrated on 09/06/06, SBE5 Pump: 053962 (3K) Secondary T & C Sensors: SBE3 Temperature:03P-4490, calibrated on 11/06/06 SBE4 Conductivity: 04C-2450, calibrated on 15/06/06, SBE5 Pump: 054164 (3K) H21: SBE 43 Oxygen: 0612, calibrated on 24/11/05 H90: Chelsea Aqua 3 Fluorometer: 088108, calibrated on 17/11/04 H16: Transmissometer: 04-4223-001, calibrated on 08/12/04
Transparency (eg transmissometer)Quantity: number of profiles = 65
Description: H10: Primary T & C Sensors (On Vane). SBE3 Temperature: 03P-2728 Calibrated on 15/03/06, SBE4 Conductivity:04C-2851, calibrated on 09/06/06, SBE5 Pump: 053962 (3K) Secondary T & C Sensors: SBE3 Temperature:03P-4490, calibrated on 11/06/06 SBE4 Conductivity: 04C-2450, calibrated on 15/06/06, SBE5 Pump: 054164 (3K) H21: SBE 43 Oxygen: 0612, calibrated on 24/11/05 H90: Chelsea Aqua 3 Fluorometer: 088108, calibrated on 17/11/04 H16: Transmissometer: 04-4223-001, calibrated on 08/12/04
Current profiler (eg ADCP)Quantity: number of profiles = 1
Description: The 150 kHz vessel mounted acoustic Doppler profiler (VM-ADCP) was operated and logged throughout the cruise. Data were logged using IBM Data Acquisition Software (DAS) version 2.48 with profiler software 17.10. The instrument was configured to sample over 120 second intervals with 96 bins of 2 2 m depth, using pulse length 4 m and blank beyond transmit of 4 m. Two configuration files were set up, one for water tracking only, the other for bottom tracking in shallow water.
Current profiler (eg ADCP)Quantity: number of profiles = 1
Description: RD Instruments 75kHz Ocean Surveyor ADCP (Transducer SN 2011) was operated and logged throughout the cruise. RDI proprietary software VMDAS (V1.42) was used to configure the ADCP and perform velocity mapping to the reference frame of the vessel. A suite of MATLAB routines were used to perform data screening and transformation to absolute velocities in Earth coordinates.
Current profiler (eg ADCP)Quantity: number of profiles = 65
Description: Two 300 kHz, RDI 'Workhorse', Lowered Acoustic Doppler Current Profilers (LADCP) were deployed on the CTD frame throughout the cruise. The LADCP data were processed in Matlab using the 'Visbeck' v7 data processing suite and ship's navigation and the CTD pressure sensor were both used to improve the accuracy of the derived profiles. The majority of the profiles had been satisfactorily processed by the end of the cruise.
Chemical oceanography 
OxygenQuantity: number of profiles = 65
Description: H10: Primary T & C Sensors (On Vane). SBE3 Temperature: 03P-2728 Calibrated on 15/03/06, SBE4 Conductivity:04C-2851, calibrated on 09/06/06, SBE5 Pump: 053962 (3K) Secondary T & C Sensors: SBE3 Temperature:03P-4490, calibrated on 11/06/06 SBE4 Conductivity: 04C-2450, calibrated on 15/06/06, SBE5 Pump: 054164 (3K) H21: SBE 43 Oxygen: 0612, calibrated on 24/11/05 H90: Chelsea Aqua 3 Fluorometer: 088108, calibrated on 17/11/04 H16: Transmissometer: 04-4223-001, calibrated on 08/12/04
OxygenQuantity: number of samples = 634
Description: Dissolved oxygen concentrations were determined using the Winkler whole bottle titration method.
PhosphateQuantity: number of samples = 659
Description: Inorganic nutrients were measured on every bottle from every CTD cast using a Skalar San Plus autoanalyser. All data were processed in flow access version 1.04.4. In total 634 niskin bottle and 25 underway samples were analysed.
NitrateQuantity: number of samples = 659
Description: Inorganic nutrients were measured on every bottle from every CTD cast using a Skalar San Plus autoanalyser. All data were processed in flow access version 1.04.4. In total 634 niskin bottle and 25 underway samples were analysed.
NitriteQuantity: number of samples = 659
Description: Inorganic nutrients were measured on every bottle from every CTD cast using a Skalar San Plus autoanalyser. All data were processed in flow access version 1.04.4. In total 634 niskin bottle and 25 underway samples were analysed.
SilicateQuantity: number of samples = 659
Description: Inorganic nutrients were measured on every bottle from every CTD cast using a Skalar San Plus autoanalyser. All data were processed in flow access version 1.04.4. In total 634 niskin bottle and 25 underway samples were analysed.
Other chemical oceanographic measurementsQuantity: number of profiles = 65
Description: H10: Primary T & C Sensors (On Vane). SBE3 Temperature: 03P-2728 Calibrated on 15/03/06, SBE4 Conductivity:04C-2851, calibrated on 09/06/06, SBE5 Pump: 053962 (3K) Secondary T & C Sensors: SBE3 Temperature:03P-4490, calibrated on 11/06/06 SBE4 Conductivity: 04C-2450, calibrated on 15/06/06, SBE5 Pump: 054164 (3K) H21: SBE 43 Oxygen: 0612, calibrated on 24/11/05 H90: Chelsea Aqua 3 Fluorometer: 088108, calibrated on 17/11/04 H16: Transmissometer: 04-4223-001, calibrated on 08/12/04
Contamination 
Trace metalsQuantity: number of samples = 181
Description: Samples were taken from the Rosette sampler at 19 CTD stations and from each bottle one filtered and one unfiltered sample was taken. Both filtered and unfiltered bottles were stored in a chest freezer.
Biology and fisheries 
Phytoplankton pigs (eg chlorophyll, fluorescence)Quantity: number of samples = 105
Description: POC analyses: Water samples from CTD bottles (3 litres) were taken from each depth, and filtered onto MF filters, 25mm, (pre-combusted at 400°C). They were then stored at -80°C, to be analysed at NOCS. For each POC and underway station, chlorophyll samples were obtained by filtering 250 ml of sea water onto Whatman 25 mm GF/F filters to yield total chlorophyll. Filters were then placed in the -80°C freezer for analyses at NOCS.
Particulate organic matter (inc POC, PON)Quantity: number of samples = 105
Description: POC analyses: Water samples from CTD bottles (3 litres) were taken from each depth, and filtered onto MF filters, 25mm, (pre-combusted at 400°C). They were then stored at -80°C, to be analysed at NOCS. For each POC and underway station, chlorophyll samples were obtained by filtering 250 ml of sea water onto Whatman 25 mm GF/F filters to yield total chlorophyll. Filters were then placed in the -80°C freezer for analyses at NOCS.
PhytoplanktonQuantity: number of hauls = 10
Description: The plankton net was attached to the deck winch and lowered to a max depth of 100 m and retrieved at a speed of about 0.5 to 1m per second. The contents were drained into the bucket. The sample was concentrated by pouring it through a sieve and then washed into a sample bottle.
ZooplanktonQuantity: number of hauls = 10
Description: The plankton net was attached to the deck winch and lowered to a max depth of 100 m and retrieved at a speed of about 0.5 to 1m per second. The contents were drained into the bucket. The sample was concentrated by pouring it through a sieve and then washed into a sample bottle.
Moorings, landers, buoys 
Physical oceanography 
Current profiler (eg ADCP)59° 29' 54" N  19° 59' 45" W — Sediment trap mooring and 75 kHz ADCP deployed on 15/10/06 at depths 2765 m (sed trap), 363 m (ADCP)
Biology and fisheries 
Sediment traps59° 29' 54" N  19° 59' 45" W — Sediment trap mooring and 75 kHz ADCP deployed on 15/10/06 at depths 2765 m (sed trap), 363 m (ADCP)
Sediment traps58° 51' 57" N  20° 24' 10" W — Sediment trap mooring deployed on 16/10/06 at depth 2856 m
Sediment traps59° 38' 58" N  18° 46' 50" W — Sediment trap mooring deployed on 15/10/06 at depth 2732 m
Sediment traps60° 0' 37" N  20° 49' 30" W — Sediment trap mooring deployed on 15/10/06 at depth 2781 m
Data held at BODC Get data
Discrete samples 
65  CTD frame plus rosette samplerPhosphate concentration parameters in the water column
Salinity of the water column
Dissolved oxygen parameters in the water column
Silicate concentration parameters in the water column
Nitrate concentration parameters in the water column
5  Instrument mooringSedimentation flux of carbon, nitrogen or organic matter in the water column
Sedimentation flux of non-metallic inorganic species in the water column
Sedimentation flux quantification in the water column