RRS James Clark Ross JR19990425 (AMT8, JR41, JR42)

Cruise summary report

Cruise Info. 
Ship name (ship code)RRS James Clark Ross (74JC)
Cruise identifierJR19990425 (AMT8, JR41, JR42)
Cruise period1999-04-25 — 1999-06-07
Port of departureStanley, Falkland Islands (Malvinas)
Port of returnGrimsby, United Kingdom
ObjectivesAMT 8: This cruise took place in two legs, April 25th - April 29th and May 18th -June 7th 1999. The Principal Scientist was Nigel Rees from PML. The AMT 8 cruise report is only available electronically and is an incomplete document ( There are no plans to produce a finished document.

JR42: The structure of the Earth's crust at oceanic volcanic islands is of interest for the information it provides both about the processes involved in the formation of these islands and about the rheology of the underlying oceanic lithosphere, which deforms in response to the island load. Since some of the acoustic energy from large underwater explosions is commonly coupled into the oceanic sound channel as so-called "T-phases", hydrophones around several such islands and broadband seismic stations on the islands are being used for monitoring of the Comprehensive Test Ban Treaty. Cruise JR42 involved a four-day seismic experiment around the island of Ascension, a 4-km-high volcano some 90 km west of the Mid-Atlantic Ridge. During the experiment, a 6186 cu. in. airgun array was fired at one-minute intervals for about two days along a series of lines extending up to 45 km from the coast of the island. These shots were received by hydrophones and sonobuoys offshore and seismometers onshore. The shots were used to locate and calibrate three permanently installed hydrophones, to study the coupling of seismic energy into the island slope, and to study the structure of the crust beneath the island. The experiment was funded by the US Department of Energy (through Lawrence Livermore National Laboratory (LLNL)), the US Office of Naval Research, the UK Natural Environment Research Council, the United Nations (through the Comprehensive Test Ban Treaty Office in Vienna), IFREMER's Centre de Brest, and funds held at the University of Southampton by T. A. Minshull.
Chief scientistNigel Rees (Plymouth Marine Laboratory), Tim A Minshull (University of Southampton School of Ocean and Earth Science)
ProjectAtlantic Meridional Transect (AMT)
Coordinating bodyNatural Environment Research Council (NERC)
Cruise reportRRS James Clark Ross JR19990425 (AMT8, JR41, JR42) cruise report jr41.pdf (0.57 MB)  RRS James Clark Ross JR19990425 (AMT8, JR41, JR42) cruise report jr42.pdf (0.31 MB) 
Ocean/sea areas 
GeneralNorth Atlantic Ocean
South Atlantic Ocean
Track chartsRRS James Clark Ross JR19990425 (AMT8, JR41, JR42) cruise track — jr42trk.pdf (0.06 MB) 
Data held at BODC Get data
Discrete samples 
38  CTD frame plus rosette samplerTransmittance and attenuance of the water column
Carotenoid and flavenoid pigment concentrations in water bodies
Temperature of the water column
Salinity of the water column
Visible waveband radiance and irradiance measurements in the water column
Raw light meter output
Density of the water column
Raw fluorometer output
Chlorophyll pigment concentrations in water bodies
109  Expendable BathythermographTemperature of the water column
324  Sample taken from ship's non-toxic supplyCarotenoid and flavenoid pigment concentrations in water bodies
Chlorophyll pigment concentrations in water bodies