RRS James Clark Ross Cruise 194, 12-23 Dec 2008. Drake Passage repeat hydrography: WOCE Southern Repeat Section 1b – Burdwood Bank to Elephant Island.

Abstract

A repeat hydrographic section (WOCE section SR1b) across Drake Passage was occupied
during December 2008 aboard the RRS James Clark Ross (JR194). This is a section across the
Antarctic Circumpolar Current at its narrowest point, with the primary objective of this cruise
being to determine the currents, characteristics and transports of the various water masses.
A total of 32 CTD/LADCP stations were sampled across Drake Passage and down to Rothera,
of which 30 comprised the SR1b repeat hydrographic section between Burdwood Bank and
Elephant Island, and the first two were test stations. In addition to temperature, salinity and
oxygen profiles from the sensors on the CTD package, water samples from the 24-bottle rosette
were analysed for salinity at each station, in order to calibrate the CTD salinity profiles. Also,
samples were collected from the shipís underway system to calibrate and complement the data
continually collected by the OceanLogger. 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 shipsí VMADCP (vessel mounted acoustic Doppler current
profiler) mounted on the hull. Meteorological variables were monitored using the onboard
surface water and meteorological sampling system. Bathymetry data were also collected using
a Simrad EA600 echo-sounder, and 7 Argo floats were deployed. A new addition to the
scientific complement was the study of microbial abundance and dynamics within the Drake
Passage section. Flow cytometry was used to compare the abundance of dominant microbial
plankton groups, and a scintillation counter to assess the productivity rates of the
bacterioplankton.
The work is a component of the "Sustained Observations" supported by NERC's Oceans 2025
programme. This report describes the methods used to acquire and process the data on board
the ship during cruise JR194.

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