Cruise inventory

RRS James Clark Ross JR15007

Cruise summary report

Cruise Info. 
Ship name (ship code)RRS James Clark Ross (74JC)
Cruise identifierJR15007
Cruise period2016-05-25 — 2016-07-10
StatusCompleted
Port of departurePort of Spain, Trinidad and Tobago
Port of returnImmingham, United Kingdom
PurposeResearch
ObjectivesIncreased amounts of mixing arising from the internal tide over ridges and seamounts has been recognised for some time, but the biogeochemical consequences of that mixing have not yet been quantified. The Ridgemix project takes as its key hypothesis that the mixing generated by the internal tide over steep ocean seabed topography, such as mid ocean ridges, plays an important role in the biogeochemistry of the ocean. In the subtropical North Atlantic work using noble gas tracers has identified the amounts of nutrient that must be supplied to the region, which is in agreement with the requirements of primary production, but the mechanisms responsible for supplying this nutrient are not understood. Our view in the Ridgemix project is that internal tide mixing over the mid-Atlantic ridge brings deep nutrients upward onto isopycnals that, downstream of the ridge, are accessed by deep winter mixing in the western subtropical Atlantic Ocean. Based on preliminary evidence from earlier research cruises on other projects we also think that the upward mixing of nutrients could have local effects on primary production and plankton community structure immediately above the ridge.

Our cruise track and sampling stations had the following aims:
(i) Quantify the internal mixing and vertical nutrient fluxes at spring and neap tides at sites above the ridge and in the deep water away from the ridge.
(ii) Quantify the general distribution of vertical turbulent mixing along the ridge, in the adjacent deep basin to the west, and across the slopes of the ridge.
(iii) Measure the distribution of nutrients on key isopycnals in water masses before, during and downstream of the mixing over the ridge.
(iv) At sites along the ridge and in the deep basin to the west, quantify the phytoplankton and zooplankton community structures with a particular focus on the deep chlorophyll maximum.
Chief scientistJonathan Sharples (National Oceanography Centre, Liverpool)
Cruise reportRRS James Clark Ross JR15007 cruise report jr15007.pdf — access key 'C' (5.16 MB) 
Ocean/sea areas 
GeneralNorth West Atlantic Ocean (limit 40W)
SpecificMid Atlantic ridge
Track chartsRRS James Clark Ross JR15007 cruise track — jr15007trk.pdf (00 MB) 
Measurements 
Physical oceanography 
CTD stationsQuantity: number of profiles = 67
Description: CTD: salinity, temperature, density, dissolved oxygen, chlorophyll fluorescence, beam transmittance.
Current profiler (eg ADCP)Quantity: track kilometres = 4500
Description: Vessel ADCP
Current profiler (eg ADCP)Quantity: number of profiles = 67
Description: Lowered ADCP on CTD frame
Other physical oceanographic measurementsQuantity: number of profiles = 30
Description: VMP6000 turbulent microstructure profiles, full depth
Other physical oceanographic measurementsQuantity: number of profiles = 79
Description: VMP2000 turbulent microstructure profiles to between 800 and 1600 metres
Chemical oceanography 
OxygenQuantity: number of profiles = 67
Description: Bottle samples from CTD profiles.
PhosphateQuantity: number of profiles = 67
Description: Bottle samples from CTD profiles.
NitrateQuantity: number of profiles = 67
Description: Bottle samples from CTD profiles.
SilicateQuantity: number of profiles = 67
Description: Bottle samples from CTD profiles.
Biology and fisheries 
Phytoplankton pigs (eg chlorophyll, fluorescence)Quantity: number of profiles = 20
Description: Bottle samples from CTD profiles
Particulate organic matter (inc POC, PON)Quantity: number of profiles = 20
Description: Bottle samples from CTD profiles
Dissolved organic matter (inc DOC)Quantity: number of profiles = 20
Description: Bottle samples from CTD profiles
Biochemical measurements (eg lipids, amino acids)Quantity: 40
Description: Standalone pumps, 4 deployed at 10 sites.
PhytoplanktonQuantity: number of samples = 200
Description: Phytoplankton samples, taken from approx 10 bottles on 20 CTD profiles.
ZooplanktonQuantity: 120
Description: Approx 6 nets (3 replicates of 2 mesh sizes) at 10 sites.
Moorings, landers, buoys 
Physical oceanography 
CTD stations36° 14' 35" N  32° 46' 54" W — Drifting wirewalker mooring with profiling CTD and turbulent microstructure. Deployed for approx.. 3 weeks during cruise.
CTD stations36° 13' 5" N  32° 44' 44" W — 1 x APEX float with CTD and SUNA nitrate sensor, profiling in the upper 1000 metres. Deployed October 2015. THIS MOORING FAILED (not recovered)
Subsurface temperature measurements36° 14' 39" N  32° 46' 52" W — 4 x 75kHz ADCPs, 30 temperature or temperature-depth loggers, all covering the whole water column (2,300 metres). Deployed in October 2015, recovered on 30/6/16.
Current profiler (eg ADCP)36° 14' 39" N  32° 46' 52" W — 4 x 75kHz ADCPs, 30 temperature or temperature-depth loggers, all covering the whole water column (2,300 metres). Deployed in October 2015, recovered on 30/6/16.
Surface drifters/drifting buoys36° 14' 35" N  32° 46' 54" W — Drifting wirewalker mooring with profiling CTD and turbulent microstructure. Deployed for approx.. 3 weeks during cruise.
Other physical oceanographic measurements36° 14' 35" N  32° 46' 54" W — Drifting wirewalker mooring with profiling CTD and turbulent microstructure. Deployed for approx.. 3 weeks during cruise.
Other physical oceanographic measurements36° 14' 49" N  37° 0' 16" W — Glider with ADCP and turbulent microstructure sensors, profiling in upper 200 metres for approx. 3 weeks. Note: 2 other gliders also deployed, but both failed.
Chemical oceanography 
Nitrate36° 13' 5" N  32° 44' 44" W — 1 x APEX float with CTD and SUNA nitrate sensor, profiling in the upper 1000 metres. Deployed October 2015. THIS MOORING FAILED (not recovered)