The research cruise JC238 on RSS James Cook in the North Atlantic forms part of the UK “Overturning in the Subpolar North Atlantic Programme” (UK-OSNAP) and Ellett Array projects and aims to better understand ocean circulation and fluxes through continuous observations of the North Atlantic Subpolar Gyre. The OSNAP array was installed in 2014 to monitor the Atlantic Meridional Overturning Circulation (AMOC). The AMOC is a large system of ocean currents that spans the entire Atlantic. Its upper part transports warm water towards the North. And its lower part, deep below the ocean surface transport cold water towards the South. The AMOC plays an important role in mixing the world’s ocean and distributing heat across the planet impacting the climate. iAtlantic is contributing oxygen sensors to the OSNAP mooring array which were installed in 2020 from RSS Discovery. Together with pH measurements (ATLAS), this will give new insights on AMOC impacts on carbon fluxes.

During the cruise we will deploy 6 BGC-Argo floats, turn around 6 moorings along the Ellet line and OSNAP array in the Rockall Trough and the Iceland Basin and we will install a new drift-free bottom pressure recorder in the Rockall Trough. The bottom pressure recorder will stay in the water for 10 years and its data will be harvested remotely via an acoustic modem without the need to recover the instrument. This is unprecedented for AMOC observations. A similar sensor will be deployed by German colleagues at the western border of the Atlantic basin. The new bottom pressure recorders have the potential to monitor long-term changes in the AMOC with minimal observational effort. Because the sensors are drift free, smallest changes like a continuous trend will be identifiable. This was not possible before because previous bottom pressure recorders were dominated by a strong sensor drift which only allowed to studied changes on time scales shorter than the deployment period. This opens a whole new way of sustainable basin wide transport observations. The company providing the recorders visited SAMS end of May to find out more about this exciting new research. If you want to read more about it, check out their blog post: https://www.sonardyne.com/ocean-bottom-pressure-data-unlocks-amoc/

Read the iAtlantic newsletter article about this cruise (PDF)

Follow the expedition blog: https://www.o-snap.org/category/cruises/