Cruise inventory

RRS John Murray JM4B/76 (IMER/FLEX/3/76)

Cruise summary report

Cruise Info. 
Ship name (ship code)RRS John Murray (74MJ)
Cruise identifierJM4B/76 (IMER/FLEX/3/76)
Cruise period1976-04-15 — 1976-04-25
Port of departureAberdeen, United Kingdom
Port of returnAberdeen, United Kingdom
ObjectivesOn the 15th April Researcher set course for the centre of the FLEX square. Continuous logging of surface temperature, sailting, chlorophyll and nitrate using non-toxic pumped sea-water supply from 3m depth. This logging continued throughout the cruise whenever the ship was underway. Half hourly navigational and hourly meteorological observations were taken continually while the ship was at sea.

Reversing water bottle casts were used as a calibration check for UOR T and S sensors. Reversing water bottle casts were made to 8 or 9 depths at every station. The UOR was towed 7 times and CPR was towed 6 times at stations 0, 2A, 2C, 3B and UOR surveys. UOR surveys IA and IB: Leg 1 and Leg 2 of FLEX grid. UOR tows 3 & 5 and CPR tows 3 & 5. Suvey II: UOR tow 6 & 7 and CPR tow 6. 2 HSLE oblique plankton hauls and 1 LHPR oblique plankton haul made at station 9A and 1 LHPR haul at station 9B. HSLE surveys with 1/2 hourly HSLE hauls were made along Legs 1(2B), 2(3A), 3 (4A), 4 and 5 of FLEX grid. Light attenuation profiles made at stations 8A, 6A and 4B. Large volume water samples taken at stations 8A(1), 6A(5), 9B(2), 1B and 4B. Water samples for C14 experiment at station 8A. 4 sediment trap moorings were recovered and re-laid: closer to station 9; station 1A re-laid; station 5A re-laid 1/2 mile from JONSDAP mooring 91; and station 1B re-laid.

Stations: 0, 1A, 1B, 2A, 2B, 2C, 3A,3B, 4A, 5A, 5B, 6A, 7A, 8A, 9, 9A and 9B.

Bad weather and engine trouble reduced effective time in FLEX area from the planned 14 days to 6. FLEX grid was reduced from the 4 surveys planned to 2 partial surveys with UOR/CPR. Only 16 of planned 36 stations worked. Nevertheless, sampling was sufficient to obtain a reasonable impression of conditions during start of phytoplankton bloom. A thermocline was observered before the first stormy period. Chlorophyll concentrations were recorded.
Chief scientistRobert H Bruce (Institute of Marine Environmental Research, Plymouth)
ProjectJONSDAP 76 (FLEX)
Cruise reportRRS John Murray JM4B/76 (IMER/FLEX/3/76) cruise report john_murray4b_76.pdf — access key 'C' (0.58 MB) 
Ocean/sea areas 
GeneralNorth Sea
Track chartsRRS John Murray JM4B/76 (IMER/FLEX/3/76) cruise track — trk1646.html
Physical oceanography 
Surface measurements underway (T,S)Quantity: track kilometres = 2410
BathythermographQuantity: number of profiles = 30
Water bottle stationsQuantity: number of stations = 17
Subsurface temperature and salinity measurementsQuantity: track kilometres = 1111
Transparency (eg transmissometer)Quantity: number of stations = 4
Chemical oceanography 
PhosphateQuantity: number of stations = 17
NitrateQuantity: track kilometres = 1852
Description: continuous surface nitrate recording
NitrateQuantity: number of stations = 17
NitriteQuantity: number of stations = 17
SilicateQuantity: number of stations = 17
Biology and fisheries 
Primary productivityQuantity: number of stations = 4
Phytoplankton pigs (eg chlorophyll, fluorescence)Quantity: track kilometres = 1852
Description: 1000nm cont. surface chlorophyll recording
PhytoplanktonQuantity: number of stations = 17
ZooplanktonQuantity: number of hauls = 100
Description: hauls;survey:population,biomass determination etc.
Incident radiation
Routine standard measurements