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The National Oceanography Centre’s Louis Clement and Alexander Cerra have returned from a unique five-week expedition across the Labrador Sea, one of the few opportunities to study this critical region at the end of winter.
Read their story (as written by marine physicist Louis Clement):
In late March 2026, MARS engineer, Alexander Cerra and I joined the German research vessel Maria S. Merian in Nuuk, Greenland, for a five-week cruise across the Labrador Sea.
This provided a rare opportunity to sail the region at the end of winter as part of Germany’s contribution to the OSNAP project.
Conducting research in the Labrador Sea during late winter is essential for advancing our understanding of deep convection - the process by which surface waters mix with deeper layers through direct contact with the atmosphere. This period also allows scientists to observe and sample the phytoplankton bloom that helps sequester carbon dioxide in the deep ocean.
A major objective of the expedition was to deploy autonomous instruments in this harsh environment to better understand the turbulent processes driving the development of convection.
With air temperatures dropping to -10°C, icy conditions both in the water and on deck, persistent waves, and strong winds (often exceeding Beaufort force 8), operations were particularly challenging and delayed some of the planned fieldwork. Despite these difficulties, we successfully deployed two Argo-type floats equipped with turbulence sensors, along with two gliders.
Tracking the hidden turbulence shaping ocean climate
The profiling floats will measure turbulent mixing using a range of sensors that capture temperature and velocity variations at ultra-high sampling rates. One of the floats will remain in the Labrador Sea into spring, providing invaluable data on the end of convection and the lifespan of turbulence sensors in subpolar conditions.
These floats are the first to be deployed in the subpolar North Atlantic as part of a float array funded by the ARIA project POLEMIX.
POLEMIX is a five-year project that aims to characterise the global behaviour of turbulent mixing in the subpolar North Atlantic and to better understand its implications for a potential climate tipping point in the North Atlantic Subpolar Gyre.
Within POLEMIX, this data will be used in climate models to assess the likelihood of approaching such a tipping point and to help refine model accuracy.
Following the journey of carbon through ocean layers
An additional glider was deployed as part of the NERC-funded ReBELS project, which investigates how carbon is transferred from the surface to the deep ocean.
While the biological carbon pump refers specifically to the sinking of organic material, ReBELS also examines how ocean physics redistributes this carbon.
Deploying this glider in early April allows us to capture the onset of the phytoplankton spring bloom, providing high-resolution observations that help us understand how carbon export develops over the season.
Together, these deployments mark an important step forward in observing some of the ocean’s most complex and least understood processes.
The data collected over the coming months will offer valuable new insights into how the Labrador Sea drives ocean circulation and carbon storage, helping to improve climate models and our understanding of future change in this critical region.
Dive Deeper
Where is the Labrador Sea?
The Labrador Sea is in the North Atlantic Ocean, between the Labrador Peninsula of Canada and Greenland. It is known for being the coldest part of the subpolar North Atlantic and is covered in ice for roughly two-thirds of the winter.
Why is it important to study?
It is a critical, cold-water region that is often described as acting as a ‘lung’ of the ocean because it oxygenates deep-sea waters and drives global ocean circulation.
It also has a vital role to play in climate regulation, as a key ‘storage sink’ of carbon.
Researchers monitor this area as they seek to understand the impacts of climate change – from ocean warming to the ‘freshening’ of waters by melting ice.