EPOC researchers have recovered four of five moorings from the Iceland-Faroe Ridge. The recovery closes out a year-long deployment watching one of the least-observed branches of the Atlantic Meridional Overturning Circulation (AMOC). As well as recovering the moorings, the expedition was lucky enough to observe a subduction event. This is the process that turns surface water into the dense overflow feeding the AMOC’s deep return flow. The team traced it along the ridge, all the way to the mooring array.
The full record is now documented as EPOC Milestone 10, authored by James Wyatt, Karin Larsen, Hjálmar Hátún and Svein Østerhus.
In total, five moorings were deployed; two (IFRW and IFRI) in June 2025 and three (IFRZ, IFRY and IFRX) in October 2025. The recovery voyage replaced the moorings in the Faroe Bank Channel and the Faroe Current, extending two long-running series: the Faroe Bank Channel overflow record and the Faroe Current record respectively. Larsen et al. (2024) describes the first; Hansen et al. (2023) describes the second. Both now carry another year of data.
A MicroCAT CTD on mooring IFRX recorded an oceanographic process in action. When the sensor’s depth increased, temperature and salinity dropped at the same time. That combination, deeper, colder, and less salty, is the standard signature of overflow water passing beneath it.
This is what a subduction event looks like from below: colder, less salty surface water sinking beneath warmer Atlantic water at the Iceland-Faroe Front, then travelling on as overflow. It is one of the two main ways dense overflow water forms at the ridge, and it usually happens out of sight, tracked afterwards through models rather than caught directly by a sensor in the water. A mooring picking it up this clearly is exactly the kind of process-level evidence that helps refine the ocean models used in AMOC assessments.
Preliminary analysis suggests the moorings sat in a spot that regularly sees this kind of water. Pinning down exactly where it originates will take further analysis once the full dataset is calibrated.
Unfortunately, not every mooring made it back; IFRZ could not be located. While this does represent a fifth of the array’s data, it is also a familiar risk. Moorings in this region involve deploying in a busy shipping and fishing corridor through harsh winter weather. However, losing one mooring does not undermine the value of the other four, or of the subduction event sampled along the way.
The Greenland-Scotland Ridge carries the AMOC’s dense overflow water south from the Nordic Seas. The Iceland-Faroe Ridge is one of its three main crossing points, alongside the Denmark Strait and the Faroe Bank Channel. It is also the least observed of the three which is why the Iceland-Faroe Ridge moorings are key to understanding AMOC-associated processes in this region.
Cruise and mooring data will be released publicly once calibration is complete.