Takeaways from the “What does the future hold for the Southern Ocean?” conference

As part of the SOCLIM project, sponsored by the BNP Paribas Foundation under its Climate Initiative program, a team of scientists led by oceanographer Stéphane Blain, will set sail on 6 October on the Marion Dufresne, an oceanographic vessel chartered by IPEV, for a one-month mission to the Southern Ocean.

What is the role of the Southern Ocean?

At a time when CO₂  emissions are rising constantly, the issue of their absorption in our atmosphere remains critical. While the biosphere absorbs a significant part of these emissions, the ocean today plays a major role in climate control. 

To study the increase of CO₂, its storage in the oceans and the oceans’ role in the atmospheric carbon cycle, the SOCLIM mission team is setting out to study these phenomena with the aim of taking readings and samples in a critical geographical area: the Southern Ocean.

Battered by violent winds and crossed by the planet’s most powerful ocean current (the Antarctic Circumpolar Current, also known as the West Wind Drift), the Southern Ocean remains a poorly understood area due to its isolation.

Located between the 60th parallel south and the continent of Antarctica that it encircles, it makes up about 20% of the total area of the world’s oceans and is an essential passage through which the oceans interact with each other. Everything that happens there affects all of the oceans. The biological processes and hydrodynamic conditions that control them are highly variable in terms of both time and space.

The Southern Ocean, a CO₂ sink?

As the true heart of the oceans, the Southern Ocean plays a crucial role in climate change. 

The CO₂ absorbed by the ocean is transported into deep water. The biological pump or marine carbon cycle allows the phytoplankton to absorb it, until it settles and is stored in the sediment layer.

In water, photosynthetic organisms have the ability to transform CO₂ into organic carbon  (particles). This carbon is largely ironed as CO₂ especially by bacteria. But a small part manages to escape to the bottom by gravity. The carbon that reaches the sediment is stored for a very long time (millions of years).

How will the Southern Ocean behave in the future?

To measure the processes at work in the Southern Ocean, the SOCLIM project’s scientists aboard the Marion Dufresne will deploy a new generation of instruments. The data collected will allow them to study:

• heat and CO₂ exchanges between the atmosphere and the ocean;
  
• CO₂ storage/sequestration mechanisms in the ocean;
  
• the bio-optical abnormalities that have been observed on the surface of the Southern Ocean.
  

Which measuring instruments?

Two combined approaches will enable the mission to address the lack of information about the Southern Ocean’s seasonal variability.Accordingly, two types of instruments will be deployed to carry out new measurements during several months.

1. Bio-Argo floats: deployed in the Furious 50s zone, these floats will directly collect data via regular measurements (such as temperature, currents, etc.). This data will then be accessible in real time via a viewing interface accessible to the international community.
   Their mission: to obtain a temporal and spatial vision of the processes at work
   
2. Instrumented moorings: used in oceanography, these will be submerged below the surface and will be deployed throughout the Kerguelen Islands. These instruments will collect particle samples. Unlike the biological Argo floats, the instrumented moorings will be retrieved during a second campaign in 2017.
   

Bio-Argo floats and instrumented moorings (c) Stéphane Blain (LOMIC, UPMC/CNRS)

What are the expected results?

The samples and measurements will make it possible to describe the biological activity of the ocean at the seasonal level and to provide interested members of the public with knowledge about the oceans’ impacts and issues with respect to climate change.