RSS James Cook Cruise JC032, 07 Mar – 21 Apr 2009. Hydrographic sections across the Brazil Current and at 24°S in the Atlantic.

Abstract

Hydrographic sections were occupied in the South Atlantic Ocean and during March - April 2009 aboard the RRS James Cook (JC032). Three of these sections intersected the Brazil current at three separate latitudes during the steam northwards from Montevideo. The main trans-Atlantic section was occupied at 24°S. 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. The main section completed an overall aim, devised under the Oceans 2025 project, to create a box around the South Atlantic and Southern Ocean region to expose the regional circulation scheme and basin-scale budgets of physical and biogeochemical properties by performing a box-inverse analysis of the new observations.

A total of 118 CTD/LADCP stations were sampled across the South Atlantic. In addition to temperature, salinity and oxygen profiles from the sensors on the CTD package, water samples from a 24-bottle 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, CFC’s, pCO2, TIC, alkalinity, and nutrient biogeochemistry. In addition, samples were collected from the ship’s underway system to calibrate and compliment the data continually collected by the TSG (thermosalinograph). Full depth velocity measurements were made at every station by an 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 and EM120 swath system, which is attached to the hull.

This report describes the methods used to acquire and process the data aboard the ship during cruise JC032.

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