Abstract:
A new hydrographic section was taken across 36°N in the Atlantic Ocean during May-June 2005
aboard RRS Charles Darwin (CD 171). The primary objectives of this work were to measure the
meridional fluxes of heat, nutrients and CO2. This coast-to-coast, zonal data set represents the first
full repeat of this section since 1981 .
A total of 144 CTD/LADCP stations were sampled across the North Atlantic subtropical gyre. In
addition to temperature, salinity and oxygen profiles from the CTDO2 package, water samples
from a 24-bottle rosette were analysed for salinity, dissolved oxygen and inorganic nutrients at
each station. In addition water samples were collected and analysed onboard ship for SF6 , CFCs,
pCO2, TIC and alkalinity and samples were collected for shore-based analyses for He/Tr, organic
nutrients and organic carbon. Full depth velocity measurements were made at every station by up
to two ADCP's mounted on the rosette frame. Throughout the cruise velocity data in the upper
few hundred meters of the water column were provided by an ADCP mounted in the ship's hull,
and continuous measurements of near-surface water temperature, salinity and pCO2 were made.
Meteorological variables were monitored and samples of air and rainfall were periodically
collected. In addition stand alone pumps were deployed 13 times and samples were collected for
shore-side analyses of nitrogen isotopes, pigments and carbon and nitrogen. During the cruise two
fibre optic gyrocompasses were trialled both on the bench and mounted on the rosette.
This report describes the methods used to acquire and process the data on board the ship during
cruise CD171
