Planned maintenance — 18th January 2018 12:00 to 22nd January 2018 09:00 [more]

Cruise inventory

RL Gammarus 9/83

Cruise summary report

Cruise Info. 
Ship nameRL Gammarus
Cruise identifier9/83
Cruise period1983-09-28 — 1983-09-30
Port of departurePlymouth, United Kingdom
Port of returnPlymouth, United Kingdom
ObjectivesJoint cruise with RL Tamaris.

Previous work in the Tamar Estuary showed that at neap tides, in one reach of the estuary, stratification gave way very rapidly to vertically homogeneous conditions. Thought that this might have been caused by breaking internal waves. The measurements were aimed at detecting these internal waves and measuring their characteristics.

Half hourly profiles of current speed and direction, salinity, temperature and suspended solids were taken through the water column. A CTD probe was suspended near the halocline. Measurements carried out over 1 tidal cycle. During the ebb tide the Gammarus carried out echo-sounding surveys from the Tamar Bridge to above Car Green.

Echo-sounding revealed the presence of several small fronts around and after high water. During the ebb tide internal waves appeared in the deep area near Car Green apparently caused by the topographic step at the upstrem end of the deep. The internal wave motions were apparent on the CTD records.
Chief scientistKeith Dyer (Institute of Oceanographic Sciences Taunton)
Coordinating bodyNERC
Cruise reportRL Gammarus 9/83 cruise report tamarisandgammarus_sep83.pdf — access key 'C' (0.06 MB) 
Ocean/sea areas 
GeneralEnglish Channel
SpecificTamar Estuary
Track chartsRL Gammarus 9/83 cruise track — tamarisandgammarus_sep83track.pdf (0.02 MB) 
Physical oceanography 
CTD stationsDescription: a number of CTD records were made during the tidal cycle (no. of samples not noted)
Subsurface temperature and salinity measurementsDescription: Half hourly profiles taken through the water column during 1 tidal cycle
Current metersDescription: Half hourly profiles taken through the water column during 1 tidal cycle
Suspended matterDescription: Half hourly profiles taken through the water column during 1 tidal cycle
Geology and geophysics 
Multi-beam echosoundingDescription: Echosounding took place during the cruise and revealed several small fronts. No. of surveys not noted.