Investigating Rapid Ocean Dynamics in the North Atlantic

In the fall of 2022 a group of scientists and engineers from the Multiscale Ocean Dynamics (MOD) lab at UC San Diego’s Scripps Institution of Oceanography found themselves hiding from a massive storm next to an active volcano in the middle of the North Atlantic, all this while singing karaoke in Italian. More than once did they ask: “How did we end up here?”

To answer that question, first we have to back it up a little. The Northern Ocean Rapid Surface Evolution (NORSE) project, funded by the Office of Naval Research, aims to investigate the physics involved in rapid changes of the surface layer of the ocean, which is subject to the influences of wind and waves. Currents, temperature, and even the speed of sound are some of the properties that get altered by those influences, and a better understanding of these processes will ultimately help us improve modeling and predicting what the ocean will do in a changing climate.

The location for the NORSE experiment is the North Atlantic Ocean, where there are two primary regions of interest: the Lofoten Basin and the waters around the island of Jan Mayen. The Lofoten Basin is a dynamic region in the North Atlantic where warm water from the south flows north and splits in two branches. One is flowing north along the Norwegian coast, and one is going west towards Jan Mayen before turning north towards the island of Svalbard.

The warm Atlantic water spreads across the basin between these currents, and there are also a large number of eddies, or vortices (swirls), of various sizes. The Lofoten Basin Eddy is a vortex of particular interest. It is strong, deep, long-lived, and well-studied. As such it’s the perfect natural laboratory to investigate some of the processes of interest in NORSE.

Our team deployed more than 40 drifters in the eddy. These surface drifters are in essence small floating GPS and temperature sensors made and operated by the Lagrangian Drifter Lab at Scripps. They will remain in the water for several months and send data that can be used to compute currents and flows on spatial and temporal scales impossible to measure by satellites, for example. All this is to help us better understand the dynamic processes in the upper ocean.

The second experiment region involves the various seafloor features, such as channels and ridges, in the area around Jan Mayen, a small Norwegian island. Jan Mayen has the world’s northernmost volcano protruding above sea level. Mount Beerenberg (“Bear Mountain”) reaches 2,277 meters (7,470 feet) into the sky. The island has variously been in the hands of Dutch whalers in the 17th century and Allied troops during WWII. Today there is no permanent population, only a research station home to about 18-35 primarily Norwegian scientists and military personnel who serve six months to a year at a time. With its quite impressive height, the volcano serves as a useful shield from wind and waves churned up in the big storms that bring the forces on the ocean that NORSE aims to study.

During the cruise, we deployed and recovered various floating sensors that sampled everything from temperature to chlorophyll. We also deployed several moorings, which are sensors on long wires with surface buoys attached to a heavy weight at the seafloor, that will remain in the water for at least a year, collecting data on the changes in sound speed through the various bottom channels that exist around Jan Mayen.

The 2022 cruise was the second in the NORSE series. The first was in the same region in September of 2021. In 2022 the MOD team was joined aboard the Italian research vessel Nave Alliance by researchers representing Applied Research Laboratories at the University of Texas, Virginia Institute of Marine Science (VIMS), Woods Hole Oceanographic Institution (WHOI), Applied Physics Lab (APL) at University of Washington, Center for Marine Research and Exploration (CMRE), Italy, and University of Bergen, Norway.

Between the groups, there were enough oceanographic instruments around to sample pretty much anything one could imagine sampling in the ocean. From autonomous gliders that can be piloted to go back and forth over interesting features like ocean fronts, to ship-based profilers that can measure temperature and salinity with high resolution at depths of thousands of meters, to various acoustical instruments, both of the profiling and moored kind.

For the MOD team, the fall 2022 cruise was a chance to test out a new instrument that has been in development in the lab for a while — a towed acoustic profiler. Consisting of an array of staggered acoustic sensors placed on a torpedo-like profiler that is lowered off the side of the ship on a custom-built winch, the “towed PADS” or “T-PADS” can be angled in different directions. They thereby offer a chance to collect very high-resolution data in a swath of the ocean as the ship slowly moves around.

The acoustic sensors used for this type of oceanographic research rely on the principle of scattering. Acoustic signals sent from our instruments bounce off small particles in the ocean, such as plankton, and scatter back to us. Measuring the Doppler effect — the time delay in the sound pulse when it returns — provides details of the currents in the water around the instrument in high temporal and spatial resolution. The T-PADS were successfully deployed and collected data. These data will be incorporated in a PhD thesis and hopefully contribute to further development of this quite revolutionary instrument.

Though there were many successful deployments of various instruments during the cruise, the North Atlantic can be a harsh place and it’s not always rainbows and unicorns (or Northern Lights and narwhals, which might be more appropriate here). During the cruise, we struggled with everything from weather delays to the loss of instruments, having to hide behind Jan Mayen to wait out a storm and having various things break.

Being at sea can be hard, from being seasick to missing family, long days, a lack of sleep and food that you’re not used to eating. In those times, the people around you make all the difference. The NORSE 2022 science party was a golden example of that.

Together on the ship we celebrated Halloween by decorating the lab and dressing up as Vikings (the obvious choice of Halloween costume for a project called “NORSE”). When Día de los Muertos rolled around, we made a little altar to our instruments lost at sea, we threw dance parties on the back deck at 2 a.m. surrounded by swirling snow while doing overnight profiling, and we worked our way through an impressive number of crosswords.

And when things look bleak and you’re losing hope that you’ll ever get that data you need for your paper or thesis? Remember that you can always fall back on that time-old tested and trusted idea that, despite language barriers, there’s always the uniting power of music and belting out a good tune or dancing together with the people around you. There is always some fun to be had, even if the karaoke is in Italian….

Read more blog posts from both NORSE cruises on the MOD website here:

http://www.mod.ucsd.edu/norse
MOD is also on Instagram and Twitter: @MOD_at_Scripps

Kerstin Bergentz is a third-year graduate student in the MOD lab working with dynamics in the upper ocean, air-sea interactions, and various types of waves.