RRS Charles Darwin Cruise 141, 01 Jun-11 Jul 2002. Satellite Calibration and Interior Physics of the Indian Ocean: SCIPIO

Abstract

RRS Charles Darwin Cruise 141, SCIPIO (Satellite Calibration and Interior Physics of the Indian Ocean) provided a multidisciplinary survey of the Mascarene Ridge system in the western Indian Ocean. The principal objectives were to (a) study the flow of water masses through the Ridge system, together with their decadal-timescale variability, (b) assess the energy fluxes and mixing arising from internal waves, (c) collect in situ data for the calibration of sea-surface temperature and ocean colour sensors on the ENVISAT satellite, (d) investigate the biogeochemical properties of the water masses, and (e) measure the heat fluxes and winds, and the airflow disturbance around the ship.

The survey comprised three sections parallel with the Ridge near 64°, 60° and 57° E, joined by two other sections at 8° and 20°S. The sections comprised CTD, LADCP, and biogeochemistry (nutrients, phytoplankton, zooplankton, biogenic gases, CFC tracers and light levels) stations to full ocean depth, at typical spacings of about 60-80 nm.

At several of these the CTD and LADCP were cycled continuously for a semidiurnal tidal cycle to study the internal waves, and the smaller 12-bottle CTD frame was used throughout (usually with 6 bottles) in order to reduce mixing effects from the trailing wake. Underway measurements were made with the shipboard ADCP, TSG, radiosondes, XBTs, and of surface meteorology, skin surface temperature, and zooplankton.

The ship's EM12 swath bathymetry system was operated continuously, and used to study certain key areas in detail. In addition, MMP (a cycling CTD) and bottom-mounted ADCP moorings were successfully laid and recovered near 8°S, 60°E, and a first deployment of the ARGODOT turbulence probe was made near 20°S, 57.5°E.

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