A Day in the Life of the Ocean Currents

By Mara Freilich, Postdoctoral Fellow at the Scripps Institution of Oceanography. // ABOARD THE SALLY RIDE //

A whiteboard lists the day's schedule.
Schedule for the day. Credit: Mara Freilich

While doing oceanographic fieldwork, we live and work on the ship. This is the second week that we have been at sea. While there is a rhythm to life at sea, every day is different. Since we are studying ocean dynamics that change quickly, we sample adaptively, meaning that we adjust when and where we sample to follow quickly moving ocean features. I am a postdoctoral fellow at University of California, San Diego’s Scripps Institution of Oceanography. I am working on sampling biological communities to understand how ocean currents, particularly a type of current called submesoscale that spans up to 6.2 miles, or 10 kilometers, across, affect plankton, which form the base of the food web in the ocean. We work as a team on the ship, and I work most closely with the biological sampling team: Kelly Luis (NASA’s Jet Propulsion Laboratory), Sarah Lang and Pat Kelly (University of Rhode Island), Dante Capone (UC San Diego), and Élise Beaudin (Brown University).

There is no typical day, but here’s a look at one “day in the life” of the S-MODE field campaign.

Early morning: I woke up at 2:45 am this morning to plan biological sampling. We aimed to do a Conductivity, Temperature, and Depth (CTD) cast at 5 am. A CTD cast involves lowering a scientific instrument through the water that measures a range of physical and biological variables and that can close bottles to bring water from depth onto the ship. When I woke up, I learned that overnight, Sarah had spotted a submesoscale eddy  in the observations. I looked at the new data and agreed that this was exactly the type of ocean current we had been looking for and charted a course to cross through it again. Once I had the plan, I sent waypoints to the captain and mates who drive the ship. Elise, Kelly, Dante and I started sampling surface water to study the biological communities there. When we got the location that we had planned for a CTD cast, we sampled water from the cast and started a 24-hour experiment to measure growth and grazing rates. This allows us to investigate the role of ocean physics and community composition on ocean food webs. We finished processing the samples just in time for a breakfast of croissant and eggs.

Woman in teal shirt conducts Conductivity, Temperature, and Depth, or CTD, cast to preserve marine samples.
Mara Freilich preserving samples from the CTD cast. Credit: Kelly Luis

Late morning: After a quick nap, I did some data analysis. We are constantly collecting and analyzing data to figure out next steps. Right after lunch (vegetable soup and cheese bread), there was a fire drill. There is a drill every week to keep the scientists and crew in practice in case of a real emergency.

Two researchers sit in front of 12 computer screens, reading a display of data. The computer monitors are aboard a research vessel, with a port hole window in the background.
Pat Kelly and Mara Freilich operating the CTD and choosing where to collect water. Credit: Kelly Luis

Afternoon: This afternoon we deployed nine autonomous vehicles from the ship. Autonomous vehicles are ocean robots that sample alongside us to give more information. While outside doing this, we saw a whale and took a moment to watch as it swam near the ship!

A group of researchers, equipped with hard hats and life vests, pull at ropes to assist the S-MODE waveglider lower into the ocean.
Members of the S-MODE mission deploying a waveglider, a type of autonomous ocean vehicle. Credit: Kelly Luis

We also had a Zoom meeting with the whole project team, including the pilots for the autonomous vehicles who work from land, scientists working with instruments on planes that fly over the experiment area every day, and scientists involved in the project in other ways, including numerical modeling. We all discussed our interpretations of what we were seeing and the plan for the next 24 hours.

Evening: After dinner, I helped Sarah calibrate one of the instruments that measures the way that light passes through water, called an AC-S (Spectral Absorption and Attenuation Sensor). This instrument tells us about the biological communities in the water, which absorb and scatter light. (Think about a pond with lots of algae that turns green). While the instruments collect data continuously, we have to maintain them to get good quality data. I took a shower and went to sleep after a productive day. Our cabins are on the deck above the spaces where we work and eat. I share my cabin with Kelly. We have bunk beds. Before going to sleep, I made a plan for tomorrow, but of course it might change depending on how the ocean currents change overnight!

Elation Through Filtration: An Oceanographer’s Sensations at Sea

By Dante Capone, Ph.D. student at the Scripps Institution of Oceanography // ABOARD THE SALLY RIDE //

Being a biological oceanographer on a physical oceanographic voyage has highlighted a key distinction between the two disciplines.

Physical oceanographers rely on sensing – deploying instrumentation that measures properties of the water: temperature, velocity, oxygen, etc. Those data are sent back to laptops allowing for near instantaneous analysis. The day-to-day work of biological oceanography, on the other hand, may be a science best described by filtering – a task that is intertwined with most measurements in our field. We collect water and remove the particles or organisms we want to study. The finest filter might have holes that let only the tiniest particles through, while the largest filter could be something like a large net, where even fish can slip through its mesh.

On the surface, this seems to have drawbacks: the science requires elaborate (but often aesthetic) filtration racks and intensive labor both on the ship and back on shore. It may be months before samples are fully analyzed and in a nicely formatted data table on your computer. However, for me these additional steps have resulted in a greater appreciation for the science and a deeper natural intuition for the water we study.

Different interpretations of the filtration rack aboard the R/V Sally Ride
Different interpretations of the filtration rack aboard the R/V Sally Ride. Credit: Dante Capone

Filtering concentrates the colors and shapes of the particles and plankton in the water, painting them on the canvas of a small, white 25mm lens into the water below us. When passing through a phytoplankton bloom the filter may stain vibrant shades of green, yellow, or red, and with material thick enough to form plankton layer cake. Occasionally, a stray zooplankton – a jellyfish or small crustacean – may unintentionally wind up on your filter, causing the true marine biology nerds to gather around in excitement in an attempt to identify it. We note everything, pack the filters into neatly labeled vials and archive the evolution of our oceanographic journey for analysis back on land.

Tools for filtration and biological oceanographic activities.
Essential tools for filtration and biological oceanographic activities. Upper left) 200uL and 1000uL pipettes and 0.1um filter pack. Upper right) 25mm diameter Supor and glass-fiber filters. Lower left) Filter with phytoplankton and larger gelatinous salp zooplankton. Lower middle) Filters loaded onto rack. Lower right) View of filter with filter funnel from above. Credit: Dante Capone

Part of the reason I enjoy biological oceanography is the variation provided by alternating between typical work on the computer and in the lab punctuated by intense bouts of fieldwork at sea. Compared to the data analysis or paper reading we do back on land, the “sea brain” switches gears, acclimating to more hands-on work. After a handful of experiments, we’ve dialed in our tasks, placing filters, measuring and pipetting water becoming ingrained into our muscle-memory. This frees up the mind and facilitates conversations and a special kind of bonding that can only happen due to the lengthy nature of our sampling.

On the S-MODE campaign, I have been doing a lot of filtering. In my case, I’m interested in measuring grazing in the ocean. Analogous to cattle grazing grass on land, zooplankton graze phytoplankton in the ocean and convert this into energy for larger organisms, or export it to the seafloor as fecal pellets. To make my measurements, I join the party of scientists to gather around the CTD (a suite of sampling instruments) where I collect and filter water into countless labeled bottles to remove any microorganisms. Whether there are waves crashing onto the deck or sun shining on a calm sea, the excitement of science spikes our energy, allowing us to share laughter and meaningful conversation. Back in the ship’s lab we’ll carefully pour our water onto dozens of filters, often powered by lively music.

Scenes from CTD water collection party
Scenes from CTD water collection party. Courtesy of Jessica Caggiano and Jacob Wenegrat.

There may come a day soon when biological oceanography advances to the point of instantaneous measurements. Already, high-tech cameras, acoustics, optics, and even early in-situ DNA measurements pave the way to phase out filtration. However, for now we will continue to enjoy the opportunity to slow down and enjoy letting each parcel of water we collect pass through our hands.