RRS Discovery Cruise 346, 05 Jan - 19 Feb 2010. The 2010 transatlantic hydrography section at 24.5°N

Abstract

A Hydrographic section was occupied at a nominal latitude of 24.5°N in the Atlantic Ocean during January - February 2010 on Cruise 346 of RRS Discovery. The primary objective of this cruise was to measure ocean physical, chemical and biological parameters in order to establish regional budgets of heat, freshwater and carbon, and to infer decadal variability.

A total of 135 CTD/LADCP stations were sampled, with two additional bottle blank stations. In addition to temperature, salinity and oxygen profiles from the sensors on the CTD package, water samples from a 24 x 20 litre rosette were analysed for salinity, dissolved oxygen and inorganic nutrients at each station. Water samples were collected from strategically selected stations and analysed onboard ship for SF6, CFCs, DIC, alkalinity, and filtering. In addition, samples were collected from the ships’underway system to calibrate and compliment the data continually collected by the TSG (thermosalinograph). Full depth velocity measurements were made at every station by LADCP (Lowered Acoustic Doppler Current Profiler) mounted on the frame of the rosette. Throughout the cruise, velocity data in the upper few hundred metres of the water column were collected by the ship’s VMADCP (Vessel Mounted Acoustic Doppler Current Profiler) transducers (75Hz and 150Hz) mounted on the hull. Meteorological variables were monitored using the onboard surface water and meteorological sampling system (SURFMET). Bathymetric data was collected using the EA600 echo sounder, which is attached to the hull. However, whilst steaming it was found that switching over to the fish instrument produced a cleaner dataset.

This report describes the methods used to acquire and process the data on board the ship during cruise D346.

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