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RRS Charles Darwin CD169
Cruise summary report
Cruise Info. | |
Ship name (ship code) | RRS Charles Darwin (74AB) |
Cruise identifier | CD169 |
Cruise period | 2005-02-17 — 2005-03-18 |
Status | Completed |
Port of departure | Mindelo, Cape Verde |
Port of return | Ascension Island, United Kingdom |
Purpose | Research |
Objectives | The 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 scientist | Christopher R German (Southampton Oceanography Centre) |
Project | ChEss (Census of Marine Life field program: Chemosynthetic Ecosystems) |
Coordinating body | SPC (P.A. Tyler & C.R. German, co-PIs) |
Cruise report | (6.99 MB) |
Ocean/sea areas | |
General | South West Atlantic Ocean (limit 20W) |
Specific | Mid-Atlantic Ridge |
Track charts | (0.14 MB) |
Measurements | |
Physical oceanography | |
Water bottle stations | Quantity: number of profiles = 18 Description: 12 point profiles collected with 10L Niskin bottles mounted on CTD-rosette |
CTD stations | Quantity: number of profiles = 18 Description: SeaBird 9/11+ CTD equipped with in situ chemical (Fe/Mn, Eh) sensors |
Transparency (eg transmissometer) | Quantity: track kilometres = 200 Description: 2-D data slices from 5 in situ SeaPoint OBS sensors towed above/below TOBI |
Transparency (eg transmissometer) | Quantity: number of profiles = 18 Description: Profiles from SeaPoint optical back-scatter sensor mounted on CTD |
Chemical oceanography | |
Other dissolved gases | Quantity: number of profiles = 18 Description: 12 point profiles collected for dissolved methane analyses |
Trace elements | Quantity: number of profiles = 18 Description: 12 point profiles collected for TDMn, TDFe and other metal analyses |
Other chemical oceanographic measurements | Quantity: number of dives = 1 Description: Non-buoyant plume mapping with ABE (5km x 1km grid, 2 depths) |
Geology and geophysics | |
Dredge | Quantity: number of deployments = 4 Description: Dredges for rock samples in 5degS, Mid-Atlantic-Ridge segment |
Core - rock | Quantity: number of cores = 22 Description: Rock cores in fresh glass, all but 4 in 5degS, MAR segment |
Bottom photography | Quantity: number of dives = 3 Description: ABE camera surveys of seafloor at new vent-sites (200m x 200m grids) |
Geophysical measurements made at depth | Quantity: track kilometres = 200 Description: Deep-tow sidescan sonar (TOBI) imaging (6km swath width) |
Multi-beam echosounding | Quantity: number of dives = 2 Description: Multibeam mapping with SM2000 on ABE (1800m x 600m grid) |
Multi-beam echosounding | Quantity: track kilometres = 250 Description: Multibeam swath bathymetry using EM12 system |