RRS Charles Darwin CD169

Cruise summary report

Cruise Info. 
Ship name (ship code)RRS Charles Darwin (74AB)
Cruise identifierCD169
Cruise period2005-02-17 — 2005-03-18
Port of departureMindelo, Cape Verde
Port of returnAscension Island, United Kingdom
ObjectivesThe purpose of the cruise was to seek for, locate and investigate the first high-temperature hydrothermal vents to be discovered anywhere on the southern Mid-Atlantic Ridge. To achieve this, a nested strategy was employed. First a continuous swath map along the length of the Mid-Atlantic Ridge from ca. 2° S to the Ascension Fracture Zone near 6° S was completed. Next, a continuous TOBI survey was conducted along the just-mapped sections of mid-ocean ridge to obtain detailed deep-tow sidescan sonar imaging of the seafloor along the ridge-axis. At the same time, a suite of miniature autonomous plume recorders (MAPRs) were deployed above and below the TOBI vehicle to obtain co-registered information about the presence or absence of high-temperature hydrothermal vents' plumes. After a brief mid-cruise port-call to exchange personnel in Ascension, the cruise continued with combined CTD operations and deployment of the WHOI autonomous underwater vehicle, ABE, in the vicinity of the most promising plume signals obtained from TOBI, close to a fresh volcanic segment centre near 5degS. Here ABE was used in three modes: i) to map non-buoyant hydrothermal plumes; ii) to map buoyant plumes and the underlying seafloor; iii) to photograph new hydrothermal vents and their associated ecosystems. In complementary work, fresh lava samples were collected by rock-coring and dredging whilst water column samples were collected using a CTD-rosette, guided by AUV-based discoveries, from both the buoyant and non-buoyant portions of hydrothermal plumes overlying two adjacent vent-sites.
Chief scientistChristopher R German (Southampton Oceanography Centre)
ProjectChEss (Census of Marine Life field program: Chemosynthetic Ecosystems)
Coordinating bodySPC (P.A. Tyler & C.R. German, co-PIs)
Cruise reportRRS Charles Darwin CD169 cruise report cd169.pdf (6.99 MB) 
Ocean/sea areas 
GeneralSouth West Atlantic Ocean (limit 20W)
SpecificMid-Atlantic Ridge
Track chartsRRS Charles Darwin CD169 cruise track — cd169trk.pdf (0.14 MB) 
Physical oceanography 
Water bottle stationsQuantity: number of profiles = 18
Description: 12 point profiles collected with 10L Niskin bottles mounted on CTD-rosette
CTD stationsQuantity: number of profiles = 18
Description: SeaBird 9/11+ CTD equipped with in situ chemical (Fe/Mn, Eh) sensors
Transparency (eg transmissometer)Quantity: number of profiles = 18
Description: Profiles from SeaPoint optical back-scatter sensor mounted on CTD
Transparency (eg transmissometer)Quantity: track kilometres = 200
Description: 2-D data slices from 5 in situ SeaPoint OBS sensors towed above/below TOBI
Chemical oceanography 
Other dissolved gasesQuantity: number of profiles = 18
Description: 12 point profiles collected for dissolved methane analyses
Trace elementsQuantity: number of profiles = 18
Description: 12 point profiles collected for TDMn, TDFe and other metal analyses
Other chemical oceanographic measurementsQuantity: number of dives = 1
Description: Non-buoyant plume mapping with ABE (5km x 1km grid, 2 depths)
Geology and geophysics 
DredgeQuantity: number of deployments = 4
Description: Dredges for rock samples in 5degS, Mid-Atlantic-Ridge segment
Core - rockQuantity: number of cores = 22
Description: Rock cores in fresh glass, all but 4 in 5degS, MAR segment
Bottom photographyQuantity: number of dives = 3
Description: ABE camera surveys of seafloor at new vent-sites (200m x 200m grids)
Geophysical measurements made at depthQuantity: track kilometres = 200
Description: Deep-tow sidescan sonar (TOBI) imaging (6km swath width)
Multi-beam echosoundingQuantity: number of dives = 2
Description: Multibeam mapping with SM2000 on ABE (1800m x 600m grid)
Multi-beam echosoundingQuantity: track kilometres = 250
Description: Multibeam swath bathymetry using EM12 system