Cruise inventory

RRS James Clark Ross JR20031230 (JR103, JR96)

Cruise summary report

Cruise Info. 
Ship name (ship code)RRS James Clark Ross (74JC)
Cruise identifierJR20031230 (JR103, JR96)
Cruise period2003-12-30 — 2004-01-20
StatusCompleted
Port of departureStanley, Falkland Islands (Malvinas)
Port of returnStanley, Falkland Islands (Malvinas)
PurposeResearch
ObjectivesThe main aims of the JR96 cruise:
1) To use multi-frequency acoustics to estimate the biomass of Antarctic krill in
the Western Core Box (WCB) at South Georgia
2) To sample with RMT8 net hauls to characterize the dominant zooplankton and
obtain representative length frequency of krill
3)To carry out an oceanographic survey of WCB using Undulating
Oceanographic Recorder (UOR) and CTD.
4) As part of AFI-3-16 to recover and deploy moorings within WCB.

Series of acoustic traverses using the EK60 echo sounder and undulating oceanographic recorder (UOR) by day followed by CTDs and nets along same profiles by night. Unfortunately there were many icebergs and the poor weather wiped out lots of the EK60 record. Two moorings, shallow and deep, were recovered and relaid in the Western Core Box. The shallow mooring refused to resurface and so had to fish for it. The mooring was successfully recovered, the data downloaded and redeployed at 53° 47.69'N and 37° 56.31'W. The deep mooring was recovered, the data downloaded and redeployed without problems at 53° 30.66'S and 37° 51.87'W. A further traverse of the mudwave region was almost completely mapped. The magnetometer was tested for any heading effect apparent.


JR103:
The JR103 swath-bathymetry cruise also took place concurrantly with JR96. JR103 was a cruise using science time originally allocated on RRS Ernest Shackleton but transferred to the RRS James Clark Ross for operational reasons. The cruise was combined with Bioscience cruise JR96 in the South Georgia region and to minimise losing time in transit it was decided to carry out swath bathymetry and magnetic surveys along the southern and western margins of the South Georgia microcontinent. This zone is active from a tectonic point of view with several large earthquakes having taken place in recent years. It was hoped that evidence of recent volcanic activity, such as fresh fault scarps would be visible on the swath data which could give insight into the nature of the deformation taking place. The survey also covers an area formed in the earliest period of spreading on the currently active East Scotia Ridge system and there was a possibility that E-W magnetic profiles across the zone could provide information on this process.
A third objective was to try and image an unusual zone of large mudwaves at the eastern end of the South Falkland Trough. These had been identified and even cored on earlier cruises but the existing data were inadequate to properly define the nature of the wave field.

Swath and Topas started recording shortly after leaving port and the SeaSpy magnetometer was deployed. JR103 was carried out first. Proceeded to the south east corner of the main survey area south of South Georgia. Two tests of the undulator to be used on the bioscience traverses. 12 E-W swath box traverses with expendable bathythermograph on the edge of the South Georgia continental margin.
Chief scientistJonathan L Watkins (British Antarctic Survey), Peter Morris (British Antarctic Survey)
ProjectWestern Core Box - Acoustics Survey, AFI moorings servicing
Cruise reportRRS James Clark Ross JR20031230 (JR103, JR96) cruise report jr103.pdf — access key 'C' (0.96 MB)  RRS James Clark Ross JR20031230 (JR103, JR96) cruise report jr96.pdf (3.46 MB) 
Ocean/sea areas 
GeneralSouth Atlantic Ocean
SpecificNW of South Georgia South Georgia shelf margins
Track chartsRRS James Clark Ross JR20031230 (JR103, JR96) cruise track — jr103track.pdf (00 MB) 
Measurements 
Physical oceanography 
Surface measurements underway (T,S)Quantity: number of deployments = 2
Description: UOR tests
Surface measurements underway (T,S)Quantity: number of deployments = 6
Description: UOR tows for oceanographic survey
BathythermographQuantity: number of stations = 12
Description: E-W swath box
CTD stationsQuantity: number of profiles = 7
Description: oceanographic survey
Subsurface temperature and salinity measurementsQuantity: number of deployments = 6
Description: UOR tows for oceanographic survey
Subsurface temperature and salinity measurementsQuantity: number of deployments = 2
Description: UOR tests
Biology and fisheries 
ZooplanktonQuantity: number of stations = 10
Description: RMT8 to locate krill
Acoustic reflection on marine organisms.Description: a number of acoustic traverses
Geology and geophysics 
Magnetic measurementsQuantity: number of measurements = 1
Description: continuous recording
Magnetic measurementsQuantity: number of measurements = 1
Description: test
Moorings, landers, buoys 
Physical oceanography 
Current meters53° 30' 59" S  37° 51' 59" W — deep water mooring redeployed
Current meters53° 47' 59" S  37° 52' 59" W — shallow water mooring redeployed
Current meters53° 47' 59" S  37° 55' 59" W — shallow water mooring recovered
Current meters53° 30' 59" S  37° 51' 59" W — deep water mooring recovered