The Bathysonde, a historical tool for oceanographic measurements
estimated reading time: 4 minutes
by oceans connectes, le 09 september 2021
31st March 2021.
In the middle of the South Atlantic Ocean, the night is dark, the weather and the sea calm.
The ship stops at a fixed point.
We are about to make our 20th CTD station.
The 20th of a long series that will punctuate our daily journey from Chile to the Canary Islands.
During oceanographic campaigns, vertical profiles are measured at regular intervals with this tool historically used in oceanography: the bathysonde!
The bathysonde is a strange white carousel equipped with a multitude of measuring instruments. It is connected to the ship and operated by an electric cable, which is activated by a dedicated electric winch that deploys like a giant fixed-station arm to lower the bathysonde into the water.
The bathysonde is used to acquire physical and chemical data at a fixed point called a station, and along the water column – typically from the surface to 6000 metres below the surface.
It is usually equipped with two main elements: a CTD probe and a rosette.
The CTD probe (Conductivity-Temperature-Depth) allows very accurate measurements of conductivity (from which salinity is deduced), temperature and pressure (from which depth is deduced).
Other sensors that can be fitted to a CTD include dissolved oxygen sensors in the ocean or fluorescence sensors that measure chlorophyll, etc.
The rosette is the ring of bottles that surrounds the probe. The bottles allow the sampling of seawater at different depths to measure its physical and biogeochemical characteristics: temperature, salinity, pH, oxygen content, nutrient salts, etc.
During the ascent of the bathysonde from the bottom to the surface, the oceanographers trigger the closing of the bottles at different depths to collect samples all along the water column. Analyses will be carried out by the teams of chemists either on board or back in the laboratory after the samples have been preserved.
Relive a bathysonde ascent during the SAGA10W campaign!
Today, the CTD Rosette is the result of a constantly evolving technology. It has evolved with the progress of electronics, which increasingly allows continuous measurements. It is therefore a privileged tool for marine scientists who work a little more each day to unravel the mysteries of the sea.
A collective human adventure, an exceptional amount of data collected and the beginnings of a science of the sea concerned with its environmental impact: this is how we can sum up the success of this 2022 edition of the 32nd PIRATA oceanographic campaign.
A unique sailing boat, an international low-carbon campaign, that is a world first: it was under these favourable winds that the French sailing boat Blue Observer returned to the port of Brest in March after 96 days at sea in the North and South Atlantic.
More than 28 days since the departure, and the tiredness can be read on all faces. The scientists of the PIRATA-FR32 campaign have not had a single minute to keep a logbook or to send us some "live" news...it doesn't matter: the focus is on watches and measurements!
For several days now, the 14 scientists have been sailing for the 32nd edition of the oceanographic programme PIRATA ("Prediction and Research Moored Array in the Tropical Atlantic"). From the ship "Thalassa" of the French Oceanographic Fleet on which they have embarked, they gave us some news about their journey.
For the 25th consecutive year of the programme, the PIRATA oceanographic campaign left the port of Las Palmas in the Canary Islands on 28 February 2022.
In the spring of 2021 and despite a still complicated health context, scientists spent 42 days criss-crossing the South Atlantic Ocean with the aim of quantifying the most important marine current in the ocean circulation and climate system of our planet.
One of the scientific objectives of the SWINGS campaign was to understand the evolution and development of phytoplankton in the Southern Ocean.
48 sailors on board and 2 months at sea to collect, sample and filter water, with this main objective: to understand how the ocean helps regulate the climate by absorbing atmospheric CO2.
In his programme "La Terre au Carré" on France Inter, Mathieu Vidard looks back at the SWINGS expedition.
Leaving Reunion Island in January 2021, they have been together at the helm of the SWINGS mission for 8 weeks in the heart of the Southern Ocean.
For 8 weeks, 48 scientists and crew members crossed part of the Indian Ocean, passing through the Marion, Crozet, Heard and Kerguelen islands, before returning to Reunion Island 57 days later.
This year, 12 scientists and 25 crew members embarked on the 31st mission of the PIRATA oceanographic programme from the port of Brest (France) instead of the usual port since 2015 of Mindelo (Cape Verde), due to the pandemic.
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