RRS James Cook Cruise 29, 01 Nov-22 Dec 2008. SOFine cruise report: Southern Ocean Finestructure

Abstract

The SOFINE research project aims to investigate two important, inter-related aspects of the
physics of the Antarctic Circumpolar Current (ACC) and the Southern Ocean overturning
circulation: (a) the ‘frictional’ processes that slow down the ACC as it meanders around major
bathymetric obstacles and flows over small-scale topographic roughness; and (b) the meso- and
small-scale phenomena that move water masses across the ACC and modify their properties in
the process. These issues will be studied using a collection of data gathered during cruise JC
29, which is described in this report.
The JC 29 cruise consisted primarily of a series of transects across the standing meander that
the ACC forms around the northern edge of the Kerguelen Plateau. The transects delineate a
double box (Fig. 2), with the outer transects sampling the ACC as it enters and exits the
meander, and the inner transect surveying the current in an area within the meander and
downstream of some complex small-scale topography. During the transects, hydrographic,
velocity and microstructure profiles were obtained with a CTD, lowered ADCP and VMP-5500
(a free-fall vertical microstructure profiler) suite, and quasi-continuous measurements of upperocean
currents and high-resolution bathymetry were made with vessel-mounted ADCPs and a
multibeam system. A variety of profiling floats (including EM-APEX, Iridium and standard
Argo units) were also deployed at the upstream end of the meander, with the goal of obtaining
measurements of the downstream evolution of water mass properties and both thermohaline
and shear finestructure. Opportunistic measurements of upper-ocean turbulence were obtained
with an ISW tethered turbulence profiler. Finally, a cluster of three short-term (2.5 weeks)
moorings and two long-term (> 1 year) moorings were deployed at the southern end of the
inner transect to measure the generation of internal waves by flow-topography interaction at a
small ridge and the mesoscale eddy statistics of the area, respectively. The short-term
moorings were successfully recovered toward the end of the cruise.

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Identifiers

ORCID for A. Naveira Garabato: orcid.org/0000-0001-6071-605X

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