Deep-Sea Floats Set To Expand Ocean Monitoring To More Than 98% By 2028
Ifremer’s Deep-6000 prototypes have completed dives to 6,000 metres, extending autonomous ocean monitoring into the abyssal zone and addressing gaps in deep-ocean climate data.
More than 70% of Earth’s surface is covered by ocean, yet only a small fraction has been explored in detail. As climate change alters ocean temperatures and circulation, researchers are expanding autonomous monitoring systems into deeper parts of the water column.
The international Argo programme currently operates about 4,000 data-collection floats around the world. Most descend to between 2,000 and 4,000 metres, leaving a significant gap in observations from deeper waters.
France’s national ocean agency, Ifremer, is now extending that reach with its Deep-6000 floats, which are designed to operate at depths of up to 6,000 metres.
Deep-6000 Reaches The Abyssal Zone
Ifremer reported that two Deep-6000 prototypes completed five dives to 6,000 metres between 11 January and 2 February this year. The missions collected data from the abyssal zone, where extreme pressure presents major engineering challenges.
At approximately 6,000 metres below the surface, pressure reaches about 600 times the level experienced at sea level. Water pressure increases by roughly one atmosphere for every 10 metres of depth.
The successful tests make France the third country, after China and the United States, to develop Argo floats capable of reaching 6,000 metres, according to Ifremer.
"The main challenge was to design a system that could withstand the pressures of the deep sea, be self-sufficient in terms of energy to remain operational for seven years, and keep costs under control," Xavier André, head of profiler technology development at Ifremer, said in a press release.
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The Deep-6000 prototypes use composite materials rather than pure titanium for their hulls. At about 88 pounds (40kg), they weigh roughly twice as much as a typical Argo float, according to the supplied material.
Ifremer said 30 additional deep-sea floats are expected to join the international Argo fleet by 2028. The organisation says this expansion would allow researchers to monitor more than 98% of the ocean's volume.
The United States currently operates more than 100 deep-sea floats, while China operates more than 30.
How The Autonomous Floats Gather Data
Argo floats operate through repeated cycles rather than remaining permanently at a single depth. A float is deployed from a vessel and descends to a designated drift depth, where it remains for about nine days.
It then descends further to its profile depth for approximately three hours before returning to the surface. Once at the surface, the float transmits its collected measurements by satellite.
A typical cycle lasts about 10 days, and conventional floats generally complete around 150 cycles before their batteries are exhausted, giving them an operational life of roughly three to five years.
The floats measure variables including temperature, salinity, oxygen and pressure. These observations are used by scientists and weather and climate centres to study changes in the ocean and improve understanding of processes including ocean warming, sea-level rise, circulation and monsoons.
The existing global fleet generates more than 100,000 temperature and salinity profiles each year. Argo data is also freely available online for researchers and other users.
Extending Climate Observations Into Deeper Waters
More than 90% of the ocean is classified as deep ocean, meaning waters at least 200 metres below the surface. Only about 5% of the entire ocean has been explored, according to the supplied material.
Deep-ocean observations are particularly important because warming is not confined to the upper layers. The material notes that about 10% of ocean warming occurs below the depths reached by most conventional Argo floats, creating a gap in available observations.
Virginie Thierry, a physical oceanographer at Ifremer, said the Deep-6000 floats would enable the organisation to monitor warming through the abyssal depths.
"We will also be able to obtain information on deep ocean circulation," she said, "which contributes to the storage of climate signals such as heat and carbon in the deep ocean, and refine ocean prediction models. Argo is an example of truly remarkable international cooperation, with more than 60 countries contributing to it."
The expanded measurements are intended to improve understanding of how heat and carbon move through the deep ocean and provide additional data for ocean and climate prediction models.
