Mapping Deep Ocean Currents: Uncovering the Hidden Pathways of Overflow Waters

What is the main goal of this cruise, and what kinds of data are you collecting?

The aim of the FAROX cruise was to understand how dense overflow waters cross the Iceland–Faroe Ridge and the Faroe–Shetland Channel. To do this, we collected temperature, salinity, current, and turbulence data to see how these waters move and mix as they pass through these passages. In total, we carried out 154 CTD stations—an unusually high number for a cruise of this length—to map the deep currents in the region and measure their properties, currents we still know very little about.

To collect this data, what instruments are you using?
We used CTDs to measure temperature and salinity throughout the water column, LADCPs to record current velocities with depth, and the ship’s ADCP for continuous current monitoring along our cruise track. We also used a vertical microstructure profiler (VMP) in the Faroe–Shetland Channel to measure turbulence. 

What’s a typical day like onboard for the research team?
There is no true “normal” day at sea, but the rhythm is intense. The team worked in shifts around the clock — some operating the CTD and VMP, others processing data as soon as it was collected, while continuously planning the next stations. The weather and sea conditions determined if we could proceed to the next station or section.
 

Did you encounter any surprising findings or challenges during the cruise?
Yes! We expected strong currents, but surprised us most was the intensity of the tides over the ridge near Iceland. They were much stronger than anticipated and may also have some influence on the overflow waters crossing the Iceland–Faroe Ridge.

Why is this research important, and how might it impact scientists and/or the planet?
The overflow waters we studied are a critical component of the Atlantic Meridional Overturning Circulation (AMOC), which helps regulates Europe’s climate and influences sea level and weather patterns worldwide. To understand how the AMOC may change in the future, we need to know how these dense waters are formed, and through which currents they are transported. Mapping the deep currents across both the Iceland–Faroe Ridge and the Faroe–Shetland Channel in such detail as we did is an essential step toward that goal. 

What’s one thing you wish more people understood about marine research?
That the deep ocean is still one of the least observed parts of our planet. Conducting research at sea to collect direct measurements is challenging, costly, and often unpredictable, but it provides unique data that satellites and models alone cannot do. When combined, these different approaches allow scientists to construct a much fuller picture of the ocean processes. 

What’s the most challenging part of doing science at sea?
The unpredictability of weather, tides, currents, or equipment failures can change your plans in an instant. You must be flexible and patient, all while working long shifts in a confined space. Also, we cannot forget about seasickness.

What has receiving the SWERVE funding and ship time meant for you?
The funding and dedicated ship time made this work possible. Without it, we would not have been able to collect such rare observations in this region. From a first look at the data, it seems we have gathered a unique dataset that will help us better understand how overflow processes and deep currents function—and their role in shaping the climate system. I am personally very grateful to SWERVE for making this opportunity possible.