Cruise inventory

RRS James Cook JC082 (JC083)

Cruise summary report

Cruise Info. 
Ship name (ship code)RRS James Cook (740H)
Cruise identifierJC082 (JC083)
Cruise period2013-02-06 — 2013-03-08
StatusCompleted
Port of departureMontego Bay, Jamaica
Port of returnSt. John's, Antigua and Barbuda
PurposeResearch
ObjectivesThe goal of JC082 was to conduct a multidisciplinary study of two hydrothermal vent fields on the Mid-Cayman Spreading Centre (MCSC), as part of NERC Standard Grant NE/F017774/1, "Hydrothermal activity and deep-ocean biology of the Mid-Cayman Rise".

The primary tool for this investigation was the UK Isis ROV facility, undertaking the following tasks:
- high-resolution multibeam bathymetry of the hydrothermal deposits associated with each vent field
- sampling of high-temperature vent fluids from each vent field
- sampling of basement rocks and hydrothermal deposits at each vent field
- sampling of the dominant fauna inhabiting each vent field
- where possible, sampling seafloor sediments in the vicinity of each vent field
- collecting water samples from the buoyant hydrothermal plumes above each vent field

ROV dives were undertaken at two sites: the Von Damm Vent Field (VDVF; 18° 22.605' N 81° 47.875' W depth ~2300 m), and the Beebe Vent Field (BVF; 18° 32.785' N 81° 43.080' W depth ~5000 m). 6 ROV dives were undertaken at VDVF and 5 ROV dives at BVF.

In addition, a CTD was used to:
- obtain Sound Velocity Profiles (2 deployments) to calibrate the Ultrashort Baseline (USBL) acoustic navigation of the Isis ROV;
- obtain water column hydrographic profiles (5 deployments along the spreading centre axis) to investigate the oceanography of the deep water overlying the Mid-Cayman Spreading Centre;
- characterise the dispersing hydrothermal plumes from each vent field, through tow-yo profile deployments (6 deployments) collecting Niskin bottle water samples for geochemical analysis, plus one Stand-Alone Pump System (SAPS) deployment above BVF.

A rock dredge was also deployed to collect a sample of rocks from the toe of an Oceanic Core Complex feature associated with the seafloor spreading centre.

Some shipboard multibeam bathymetry data were also acquired to add to the records obtained during RRS James Cook JC044 as part of the same project.

Handed over to research cruise JC83 mid-ocean on 25/02/2013.

JC083 was a short cruise offshore Montserrat in the Lesser Antilles was funded by a (technology led) NERC standard grant.

The first aim was to test a new ROV-mounted vibracorer on the UK ROV ISIS. This would be the first vibracorer available for science worldwide of its type. The vibracorer was able to obtain 80cm long cores, but further work is now needed to increase the strength of the vibrator motor.

There were also two main science aims. The first aim was to obtain a grid of samples from a pyroclastic surge deposit emplaced offshore SW Montserrat in 1997. This surge was remarkably destructive on land with speeds in excess of 80 m/s. Multicoring was very successful and these are the first detailed samples worldwide from this type of deposit. This will help us to recognise the offshore record (and frequency) of dangerous surge events in other locations worldwide. The second aim was to use the ROV ISIS to better understand the composition, source and emplacement dynamics of very large volcanic flank collapse events. This was also very successful, and determined the composition and origin of the last major collapse event at ~14 ka.
Chief scientistJon Copley (University of Southampton School of Ocean and Earth Science), Peter J Talling (National Oceanography Centre, Southampton)
Coordinating bodyNatural Environment Research Council (NERC)
Cruise reportRRS James Cook JC082 (JC083) cruise report jc083.pdf — access key 'C' (1.31 MB) 
Ocean/sea areas 
GeneralCaribbean Sea
SpecificJC082: Mid-Cayman Spreading Centre (specifically: Von Damm Vent Field (18° 22.605’ N 81° 47.875’, Beebe Vent Field (18° 32.785’ N 81° 43.080’ W) JC083: Around Montserrat and southwest of Antigua. Kahouanne Trough.
Track chartsRRS James Cook JC082 (JC083) cruise track — jc082trk.pdf (00 MB)  RRS James Cook JC082 (JC083) cruise track — jc083trk.pdf (00 MB) 
Measurements 
Physical oceanography 
CTD stationsQuantity: number of profiles = 7
Description: CTD stations (full-depth vertical profiles); 5 for hydrography; 2 SVP (sound velocity profile) for calibration of USBL acoustic navigation of Isis ROV
CTD stationsQuantity: number of profiles = 6
Description: CTD tow-yo profiles to characterise dispersing hydrothermal plumes.
Transparency (eg transmissometer)Quantity: number of profiles = 6
Description: Tow-yo profiles of LSS (light-scattering sensor) and Eh added to CTD to characterise dispersing hydrothermal plumes.
Chemical oceanography 
Other chemical oceanographic measurementsQuantity: number of samples = 194
Description: Measurements of dissolved and particulate inorganics, DOC and POC in discrete water samples collected during tow-yo profiles of hydrothermal plumes
Other chemical oceanographic measurementsQuantity: number of samples = 37
Description: Mini-Niskin bottle samples collected by Isis ROV in buoyant hydrothermal plume. Shorebased analyses: CH4, nutrients, NH3, H2S, total metals, dissolved metals, Fe speciation, TOC, DOC, POC, Nitrate isotopes, dissolved Hg
Other chemical oceanographic measurementsQuantity: number of samples = 1
Description: Stand-Alone Pump System (SAPS) filter of hydrothermal plume; shorebased analyses: particulate composition
Other chemical oceanographic measurementsQuantity: number of samples = 24
Description: High-temperature vent fluid samples, collected by Isis ROV using gas-tight syringe sampler. Shorebased analyses: CH4, CO2, H2S, Anions / Si, Hg (including isotopes), trace metals, pH, salinity, total dissolved solids, DOC.
Biology and fisheries 
Particulate organic matter (inc POC, PON)Quantity: number of samples = 194
Description: Measurements of dissolved and particulate inorganics, DOC and POC in discrete water samples collected during tow-yo profiles of hydrothermal plumes
Dissolved organic matter (inc DOC)Quantity: number of samples = 194
Description: Measurements of dissolved and particulate inorganics, DOC and POC in discrete water samples collected during tow-yo profiles of hydrothermal plumes
ZoobenthosQuantity: number of samples = 35
Description: Samples of dominant hydrothermal vent fauna collected by Isis ROV. Shorebased analyses: morphological taxonomy; molecular phylogenetics; population genetics; gametogenic development; stable isotope composition.
Other biological/fisheries measurementQuantity: number of dives = 5
Description: Isis ROV videography observations of hydrothermal vent fauna. Shorebased analysis: mosaicing and image analysis to quantify microdistribution of dominant species.
Geology and geophysics 
DredgeQuantity: number of hauls = 1
Description: Rock dredge. Shorebased analysis: characterisation of rock type.
Core - soft bottomQuantity: number of cores = 12
Description: 12 gravity core deployments (5 successful) with depths up to 72 cm long
Core - soft bottomQuantity: number of cores = 20
Description: 20 successful multicores - samples of upper ~50 cm of sediment below seafloor
Core - soft bottomQuantity: number of cores = 25
Description: Sediment push-cores collected by Isis ROV; shorebased analyses: O2 profiles, pore water and solid phase composition
Bottom photographyQuantity: number of dives = 13
Description: 13 (1 aborted) dives of ROB ISIS for periods of up to ~10 hours
Bottom photographyQuantity: number of dives = 5
Description: Isis ROV videography of seafloor geology.
Multi-beam echosoundingQuantity: number of surveys = 5
Description: 5 ship-mounted swath multibeam surveys of individual areas up to ~4 x 4 km3
Multi-beam echosoundingQuantity: number of surveys = 1
Description: Shipboard multibeam of NE corner of Mid-Cayman Spreading Centre
Multi-beam echosoundingQuantity: number of surveys = 2
Description: Isis ROV multibeam bathymetry of vent fields.
Other geological/geophysical measurementsQuantity: number of samples = 93
Description: Rock samples collected by Isis ROV. Shorebased analysis: characterisation of rock type.