RRS James Cook JC029

Cruise summary report

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Cruise Info.

Ship name (ship code)

RRS James Cook (740H)

Cruise identifier

JC029

Cruise period

2008-11-01 — 2008-12-22

Status

Completed

Port of departure

Cape Town, South Africa

Port of return

Cape Town, South Africa

Purpose

Research

Objectives

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. 1a), 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 upper-ocean 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.

Chief scientist

Alberto C Naveira Garabato (University of Southampton School of Ocean and Earth Science)

Project

SOFINE

Cruise report

(11.28 MB)

Ocean/sea areas

General

Indian Ocean
Southern Ocean

Specific

Southern Indian Ocean - North of Kerguelen Plateau

Track charts

(0.58 MB)

Measurements

Physical oceanography

Surface measurements underway (T,S)

Quantity: activity duration in days = 55
Description: Continuous Vessel-Mounted ADCP, multibeam bathymetry and standard underway measurements

CTD stations

Quantity: number of stations = 65
Description: CTD, including 2 To-Yo stations consisting of 4 down and up casts (58 stations were done with lowered ADCP)

Current profiler (eg ADCP)

Quantity: activity duration in days = 55
Description: Continuous Vessel-Mounted ADCP, multibeam bathymetry and standard underway measurements

Other physical oceanographic measurements

Quantity: number of stations = 47
Description: Vertical Microstructure Profiler (VMP-5500)

Other physical oceanographic measurements

Quantity: number of stations = 11
Description: ISW Microstructure Profiler (ISW)

Moorings, landers, buoys

Physical oceanography

Current meters

46° 33' 46" S 71° 51' 27" E — AUS (long-term) mooring 1 (2000 m) deployed [15 Nov - 03:28 GMT - 2000m]

Current meters

46° 34' 30" S 71° 56' 56" E — AUS (long-term) mooring 2 (2500 m) deployed [15 Nov - 09:57 GMT - 2500m]

Current meters

46° 32' 24" S 71° 55' 3" E — UK (short-term) central mooring deployed [14 Nov - 01:34 GMT - 1869m]

Current meters

46° 31' 49" S 71° 53' 27" E — UK (short-term) eastern mooring deployed [14 Nov - 08:30 GMT - 1992m]

Current meters

46° 31' 39" S 71° 53' 37" E — UK (short-term) northern mooring deployed [13 Nov - 02:54 GMT - 1840m]

Current profiler (eg ADCP)

46° 32' 24" S 71° 55' 3" E — UK (short-term) central mooring deployed [14 Nov - 01:34 GMT - 1869m]

Current profiler (eg ADCP)

46° 31' 49" S 71° 53' 27" E — UK (short-term) eastern mooring deployed [14 Nov - 08:30 GMT - 1992m]

Current profiler (eg ADCP)

46° 31' 39" S 71° 53' 37" E — UK (short-term) northern mooring deployed [13 Nov - 02:54 GMT - 1840m]