Just to the east of the Ross Sea lies Cape Colbeck, our next destination. Here, ecologist Dr. Gitte McDonald is hoping to find some Emperor Penguins. In the past, Gitte has had some of her Emperors come to this area to molt. But, no one knows where they go or what they do after molting, until they are seen heading back across the Ross Sea for breeding. Gitte and her team are hoping to catch and tag Emperor Penguins to shed some light on this mystery.
Whereas we were mostly in open water during our Ross Bank surveys, now the N.B. Palmer is heading into the ice. At this time of year (e.g., late summer in the Southern Hemisphere), we didn’t know what the ice conditions would look like at Cape Colbeck. Luckily, the ice cover was more than we expected – and the ice was covered with penguins!
Ice flows off Cape Colbeck. On the look out for penguins!
Spotting penguins on the bridge. Colin, one of the Marine Technicians, makes a plan for how to safely reach the penguins.
Gitte and her team off to an ice flow to tag Emperor Penguins.
One tagged Emperor and others waiting to be tagged! Photo courtesy of Sarah Peterson, ACA permit #: 2023-003.
It’s important to note that not just anyone can jump into a zodiac and get onto the ice with penguins. Well before the cruise, Gitte had to secure the necessary permits and training to handle Emperor Penguins. And, there are a lot of rules to follow to ensure both the scientists and the penguins stay safe! So, that means that we couldn’t join Gitte’s team out on the ice, but we did have some important jobs onboard!
While the penguin ecologists were out, we geologists were wrapping up sample processing and moving our samples into the cargo hold for shipping. However, we did get some chances to be penguinologists! While “penguinologist” isn’t an actual term, it’s one we’ve adopted on the Palmer. As penguinologists, we watched from the bridge to look out for groups of Emperors and to keep eyes on the zodiac in the ice. I’m definitely adding this to my CV!
After some successful penguin tagging at Cape Colbeck, we moved more east into Marie Byrd Land, towards the Saunders Coast. While at Cape Colbeck, the N.B. Palmer could either drift in open water or use dynamic positioning to stay in the same spot if there were some large icebergs nearby. Here, the ice cover was too patchy to drift so the Captain decided to “park” in the ice to save fuel.
Parked in the ice overnight.
While Gitte and her team were out with the penguins and we were not on official penguinologist duties, we had the opportunity to take out the zodiacs for a spin. Part of the adventure is actually getting INTO the zodiac (you climb into via a rope ladder hanging over the side of the ship). These trips were probably the closest we got to being “tourists” in Antarctica, but they were also training runs for some of the crew who were interested in driving the zodiac on future expeditions. While we maintained distance from the penguins, especially the ones Gitte and her group want to tag, we did get up close and personal with some cool icebergs.
Obligatory “Hey, Mom! I’m on a zodiac in Antarctica!” picture.
Our home away from home, the Palmer, with a group of Emperor Penguins.
Gitte and her team brought 33 penguin tags with them, and used all 33 of them! Once they completed tagging, they deployed net tows (much larger than our plankton nets) to figure out what the penguins were eating. In fact, they used up all their tags ahead of schedule, so we were able to squeeze in a mini multibeam survey around the Eastern Ross Sea, which is one of the most poorly mapped regions of the Ross Sea. Unfortunately, we had to cut our bonus survey short and head north to avoid storms that were forming in our transit path across the Southern Ocean back to Lyttleton, New Zealand.
After 10 days completing multibeam surveys and Super Sites along our North-South transect of Ross Bank, we switched directions to conduct our East-West transect and finish our science days.
While mapping the shallowest portion of Ross Bank, called the bank crest, we noticed a large iceberg. Normally along our transects, we notice icebergs here and there but we kept coming across the same iceberg at the same spot. As a refresher, when you see an iceberg, you are only seeing the top 10% of the actual berg that is floating above sea level. The other 90% is below the surface. When icebergs encounter a shallow region like Ross Bank, they can get stuck – or grounded. We think this berg is grounded! Since we’ve only been seeing water for a bit, it was nice to have a landmark to keep track of during our survey.
Iceberg grounded on Ross Bank. Photo courtesy of Rachel Meyne.
After finishing our initial multibeam and subottom survey, we chose coring sites. Because the Jumbo Piston Core (JPC) was still configured from our last transect, we cored all the sites where we wanted JPCs first, before conducting the remaining super site coring (e.g., multi and kasten coring). However, before we core, we conduct water sampling to ensure we aren’t sampling mud from our coring operations. The shipboard chemists had quite a sampling marathon.
Chemical Oceanographer: Samantha Schwippert
Sam is a first year Masters Student in Dr. Kanchan Maiti’s lab at Louisiana State University. Dr. Maiti is also sailing with us! As chemical oceanographers, they are interested in understanding carbon flux in the Ross Sea, especially in the coastal regions and at the ice-shelf edge. In the Ross Sea, the formation of cold bottom waters and phytoplankton blooms act together to move inorganic and organic carbon from the atmosphere and surface ocean into the deep ocean, where it is removed from exchange with the atmosphere. Together, these processes make the Southern Ocean, and especially the coastal regions of Antarctica, an important global carbon sink (30-40% of the global CO2 uptake occurs in the Southern Ocean). Why is this important? Well, studies indicate that, within the Southern Ocean, the Ross Sea region is an important sink for anthropogenic (human derived) CO2. This means that, presently and in the past, the Southern Ocean plays an important role in regulating atmospheric CO2 concentrations and Earth’s climate system.
On the Palmer, Sam samples water from Niskin bottles on the CTD rosette, McLane Pumps, and underway sampling – plus sediment from the multicores. During CTD casts, Sam tells each bottle on the rosette to close at a different depth in the water column, resulting in a suite of samples from the water column. When the rosette is recovered, she samples the water from the bottles for nutrient content, oxygen isotopes, and natural uranium series isotopes that can track sinking particles; she also filters samples for particulate organic carbon. Sam’s favorite part about life on the Palmer is meeting everyone, the penguins, being able to experience Antarctica, midrats (a term for the midnight meal on our 24 hour ship) -really everything!
Sam sampling from the CTD rosette.
Back to Ross Bank. Once water sampling was finished at a site, we deployed the JPC! Since the JPC core barrel is typically longer than the Kasten core barrels, we can collect longer sedimentary records that extend. However, we have to wait to open these cores until they’re back at the repository. We do get a look at the sediments as we cut the core into sections onboard, but we’ll have to be patient to see the rest of it!
Cutting the Jumbo Piston Core liner as it’s pushed out of the core barrel. That’s me using the pipe cutter to cut the core linter into 1.5m sections – thankfully, I didn’t drop anything in the drink!
While JPCs are usually lined with white high density PVC pipe, we got the chance to try out clear PVC tubes similar to those used in the International Ocean Discovery Program (IODP)! Here we are (above) showing Phil, the Principal Investigator on our cruise, one of the JPCs we recovered. It is not a full barrel, as you can see from the muddy water visible at the top of the tube.
After finishing all of our JPC stations, the marine technicians reconfigured the winch for our other coring objectives. While the JPCs were a nice break from sampling, we were ready to get muddy again and jumped right into multi- and Kasten coring.
Opening the last Kasten core of our cruise! We had a lot of work ahead of us. Because the previous core was still on the table, we had to finish that sampling before we could start sampling the new core.
And with that, we finished up our science days onboard the RVIB Nathaniel B. Palmer. Over our 30 science days spread across NBP23-01 and NBP23-02, we:
acquired 7,740 square kilometers of new multibeam bathymetry data
collected >30 meters of sediment core – over 1,000 lbs of sediment,
sampled >3.5 TONS of seawater,
cleaned out the Palmer’s ice cream freezer.
But, it’s not goodbye to Ross Bank for Phil and his team – they’ll be back next year to expand our initial multibeam survey and obtain more sediment cores. For now, we will head west across the Ross Sea towards Cape Colbeck, where the penguin ecologists hope to find some Emperor Penguins to tag.
We are halfway through our allotted science days on NBP23-02, the second leg of our cruise. During our McMurdo port call, we were joined by a new group of scientists: marine ecologists who study Emperor penguins! While we are collecting our geophysical and geologic data, they are surveying the wildlife we encounter as we map Ross Bank. Their science days are at the end of the cruise, before we transit back to Lyttleton, New Zealand. We still have a lot of science to do between now and then!
Before we continue our geophysical survey, we picked up two oceanographic gliders that spent the last few months measuring different ocean water properties around McMurdo. Gliders are a type of Autonomous Underwater Vehicle (AUV) that can be outfitted with different sensors to measure water column properties. When a glider is deployed, it is given a series of waypoints. The glider will change its buoyancy to move up and down through water column, collecting data that, upon surfacing, is transmitted to researchers via satellite. Once we got word that the gliders had surfaced, it was all hands-on deck trying to spot the yellow cylinder in the vast ocean. After recovering the gliders via zodiac (a small inflatable boat), we were on our way towards Ross Bank.
Two Marine Technicians and Meredith Meyer, a scientist from the Virginia Institute of Marine Science, recovered the glider from the zodiac.
Our main objective on this expedition is to complete a sea floor bathymetric survey with multibeam sonar on and around Ross Bank. In essence, we are creating a topographic map of the seafloor. We are also collecting sub-bottom data using CHIRP sonar. This technique allows us to see the uppermost layers of sediment below the seafloor. While we are on our 12-hour shifts, one of our jobs is “watchstanding”, which involves monitoring the multibeam, CHIRP, and any other underway data we are collecting. While this job is essentially watching monitors while everyone else is off taking cores or analyzing samples, the watchstander is actually seeing newly mapped areas for the first time. As a geophysicist, Dr. Phil Bart, the chief scientist on our cruise, and his students are very interested in studying the geomorphic features on Ross Bank, and to understand past glacial activity.
As I type this post, I am watching new data coming in from the multibeam echo sounder. The rainbow lines are the previously collected data and the black space has yet to be mapped! We really are in “uncharted’ territory.
In addition to multibeam surveys, we completed a series of 5 Super Stations (SS) on a North-South transect across Ross Bank. At each SS, similar to those I described earlier during NBP23-01, we deployed the CTD, McLane water pumps, a plankton net, the MultiCorer, and a Kasten Corer. Check out my previous post to read about what these instruments and devices do! Each site takes about 6-10 hours to complete – if everything works out as planned!
Another exciting part of our cruise is the Yo-Yo Camera. Much like the name suggests, the camera moves up and down just above the seafloor. A weight hanging from the camera triggers a photo when it hits the seafloor. These photos are useful for understanding the benthic community and helps us to avoid large rocks while we are coring!
One of the many Yoyo camera photos featuring the seafloor of Ross Bank. The red dots (also circled in red) are 10 cm apart, so we can determine the size of different features/organisms.
Once we completed all 5 Super Stations on our North-South transect, the marine technicians began to configure the Jumbo Piston Corer (JPC). The JPC is similar to the Kasten Core, but it can penetrate much deeper into the sediments beneath the seafloor. Unlike the Kasten Core, on this cruise, we don’t sample the JPCs onboard. We will have to wait a few months to see what we found! At the end of our transect, we started to get into quite a bit of weather, making deck work difficult. Since configuring the JPC takes some time, we got permission to take shelter right in front of Ross Ice Shelf!
Me-half a mile from the Ross Ice Shelf!
While the troughs around Ross Bank are filled with mud that is easy to core, the Bank itself is mostly capped with sands and diamicts (mixtures of sediment with grain sizes that range from clays to cobbles), which are notoriously difficult to core and recover. Large rocks, deposited as the ice retreated, are nearly impossible to core and we had to replace more than a few cutter noses (see image and caption below).
This is what happens when you core in rocky areas. This part of the gravity/piston coring device, called the cutter nose, is located at the tip of the core pipe and “cuts” though the sediment as the pipe moves through the sediment layers. The cutter nose on the bottom left is what this component is “supposed” to look like; the other 3 rammed into rocks.
Unlike the cores we took during NBP23-01 (pre-McMurdo Station), which were generally muddy soft sediments, the cores we have collected on Ross Bank are sandier – BUT filled with foraminifers (forams, for short)! If you’re new to Expedition Antarctica, or need a reminder, I’ve been on the hunt for forams to include in my dissertation since the beginning of the expedition. These microfossils are extremely useful for micropaleontological and geochemical analyses that can help us reconstruct past ocean temperatures. With the naked eye, they look like a grain of sand. But, under the microscope, forams come in all shapes and sizes. The forams I am familiar with make their shells (called “tests”) out of calcium carbonate, but I’ve encountered a new type of foram that I haven’t seen before – the agglutinated type. The word “agglutinated” contains the Latin word agglitinare which means “to glue together”. Agglutinated forams build their tests (shells) out of sand grains or even parts of other forams! In the dry lab, where we sample the cores, I have a little microscope station set up right next to a porthole – best view in the house! Since forams are zooplankton, I can use a standard binocular microscope to see them (think: the dissecting microscopes you may have used in science class. Some scientists onboard need much more powerful microscopes to see the critters they’re after.
The two types of foraminifera I’m finding: calcareous and agglutinated. Look at all of these different shapes!
Meet the Scientists
In an earlier post, I introduced you to several scientists currently sailing on the NB Palmer. However, there are many more scientists who need introductions. Let’s meet some new people:
Geologist: Matthew Danielson
Matthew is a 3rd year PhD student in Dr. Bart (the chief scientist)’s lab at Louisiana State University. His research uses geophysical and geological methods to reconstruct ice retreat in the Ross Sea. Specifically, he’s exploring the geomorphology of Ross Bank via the multibeam and CHIRP data we are currently acquiring. Most of the features that Matthew looks for were either eroded or deposited by past glacial activity and are now covered by post-glacial sediments. For example, we can resolve a feature – such as a grounding zone wedge – with multibeam, but to see the structure of the sedimentary units in and around that feature, we use CHIRP. Exploring the spatial distribution of these features is necessary context for the other data we collect, including sediment cores. Matthew’s favorite part of this expedition is seeing all the wildlife and the Ross Ice Shelf.
Matthew cleaning multibeam data. He has to go through each line and delete any errant pings, outliers, a process that ensures that we are looking at real seafloor features.
Rachel is a first year Masters student studying paleoceanography in Dr. Molly Patterson’s lab at Binghamton University. Before this expedition, I met Rachel via email, when she was an undergraduate researcher in Dr. Amy Leventer’s lab at Colgate University. It was in Dr. Leventer’s lab that Rachel learned all about diatoms – tiny photosynthetic algae that live in the surface ocean around Antarctica, and even near the sediments in shallow waters. She is keeping VERY busy onboard, taking water samples every 6 hours to characterize the living phytoplankton assemblage in our study area. She’s also sampling water from the CTD to look at phytoplankton community depth profile. These phytoplankton also are very useful environmental indicators that are preserved in the sediment records we collect. In addition to sampling water, Rachel samples each sediment core for fossilized diatoms. One type of sample she takes is called a toothpick sample, where she collects the smallest amount of mud with a toothpick. She smears the sediment on a microscope slide and can look at and identify all the diatoms in a sample! Since these critters are TINY, Rachel has to use a microscope with 100x magnification. The Palmer has an entire Microscope Room! While the science is awesome, Rachel admits that her favorite part about life onboard the Palmer is the really nice espresso machine in the Marine Project Coordinator’s office.
Rachel looking into the microscope in the Palmer’s microscope room. Around here are examples of what she sees in the microscope: living plankton from the CTD and fossilized plankton from the cores – even microplastics (probably from our fleece jackets or sweaters- oops)!
We will finish our survey of Ross Bank by completing an East-West transect with 5 more Super Stations (water + sediment sampling). Fun fact from the penguin folks: apparently a lot of their tagged penguins like to hang out around Ross Bank!
As we arrived at our first study site, there was excitement in the air. We were surveying a site in the Pennell Trough, Ross Sea that may provide clues to how the Ross Ice Shelf retreated in the past (Fun fact: My lab mate, Imogen Browne, is studying the paleoenvironment of the Pennell Trough in the Miocene, ~14-16 million years ago). While we chose this site based on geophysical data, this was also a great water chemistry sampling site. As such, we called this first site “Super Station 1” and deployed three types of instruments/samplers:
CTDs are one of the most common instruments used in oceanography. The name stands for conductivity (salinity), temperature/transmissivity, and depth. While the CTD is a series of sensors that measures basic physical parameters, we also deploy a rosette of Niskin bottles to sample water at different depths through the water column to analyze water for biological (e.g., phytoplankton assemblages) and chemical (e.g., nutrients) parameters. We may not be GEOTRACES trace element rosette experts on this Palmer expedition, but we can hold our own.
The rosette, post deployment in the Baltic Room of the NB Palmer. The Baltic room is enclosed and lets us deploy the CTD in rough weather, and sample the Niskins away from the elements.
On our expedition, we are collecting sediment cores to assess the response of the Ross Ice Shelf to past climate changes. To collect sediments from at and below the seafloor, we deployed a multicorer and a Kasten corer. The multicorer looks similar to the rosette, but with ~8 clear plastic tubes about 1 meter long that, when triggered, collect multiple the upper 1 meter of sediment. The multicore is useful because it enables us to sample the sediment-water interface with little or no disturbance. This is really important for Paleoceanographers trying to reconstruct the last ~1000 years of climate or for regional proxy calibration and 14C reservoir corrections (more on this later). Kasten cores are special gravity cores designed to recover larger volumes of sediment and to be sampled shipboard. The Palmer has Kasten Core barrels between 3 and 9 meters long. The real trick with the kasten core is to determine how much weight to put on so that you collect a long enough sequence, but don’t over penetrate and blow out the sediment-water interface. We use the multicore and the kasten core together to get a complete sediment sequence of the upper 3 to 9 meters of sediment.
A kasten core coming up on the back deck. That red box is what the Marine Technicians (MTs) use to rest the core barrel on while they secure the weight stand.
My onboard research
On this cruise, I am wearing a few title hats: sedimentologist, micropaleontologist, and organic geochemist. My main job is to search the sediments for tiny microfossils called foraminifera – a single cell zooplankton that secretes calcium carbonate shells, called tests; in Antarctica, a lot of the benthic foraminifers (that live on or in the sediments) make their tests out of grains of sand and anything else they can find. We’re really hoping that the sediments we collect contain foraminifers made out of calcium carbonate because their tests record past ocean physical and chemical parameters. For my research, I am sampling the multicores and the kasten cores.
When I sample the multicores, my main focus is to differentiate between living and fossil organisms in the sediments. To do this, I add a protoplasm stain to the samples called Rose Bengal. This bright pink stain enables us to separate the living and recently dead organisms from fossilized organisms (with no remaining protoplasm). This process takes a few days, and I monitor the pH so that I don’t inadvertently dissolve any calcium carbonate. I then wash the fine sediments from the sample, dry the residuals in an oven for 24 hours, and then put the samples into well-labeled vials for future study! Over the years, my advisor has learned that it is best to wash for forams on the ship because Antarctic sediments and their overlying ocean waters can be corrosive to calcium carbonate. You can return home to find sediments with little or no remaining calcium carbonate.
Washing the multicore samples: You can see the stained living to recently dead organisms in this sample! Two organisms from this sample included a bivalve (top) and a benthic foraminifer (Globocassidulina spp.)!
When we sample the kasten cores, my first objective is to collect samples for radiocarbon dating. These samples will be analyzed in Dr. Brad Rosenheim’s USF lab. Radiocarbon dating is extremely important because it enables us to determine when the sediments were deposited. After we sample for radiocarbon, we sample for organic and inorganic geochemistry and micropaleontology, which will help us understand past ocean temperatures and paleoenvironments.
Also on the boat…
One thing that is great about this research expedition is that there are a lot of students from different PI groups at different universities. Let’s hear from some other students about their first day of sampling!
Environmental Scientist: Alyssa Cotten
Alyssa is an undergraduate student in Dr. Wade Jeffrey’s lab at the University of West Florida. Her research focuses on quantifying bacteria and phytoplankton production (a fancy word for growth) using radioisotope tracers. She sampled water from the top few niskin bottles. She also sampled one of the multicores to test her method in the sediments. Her favorite thing about life on the Palmer is her roommates (author’s note: she didn’t feel pressured into saying this because I am one of her roommates) and seeing snow for the first time!
Alyssa in the “Rad Van”, a shipping container on the Helo Deck where all radiotracer work is done. It is really important to avoid tracer contamination onboard because some scientists (like me) are looking at natural levels of the same elements.
Marine (Geomicro)Biologist: Caleb Boyd
Caleb is a first year Ph.D. student studying geomicrobiology with Dr. Brandi Kiel Reese’ at the University of South Alabama and Dauphin Island Sea Lab. What a way to start out a Ph.D.! For his project, he is sampling the CTD, multicore, and Kasten core – the whole suite of tools we deployed. When he samples, Caleb “protects the samples from himself” – making sure that his microbiome does not contaminate the samples. In their lab onboard the Palmer, Dr. Kiel Reese’s team set up a “clean bubble” by hanging plastic sheets around their equipment to prevent contamination. Caleb will determine the metatranscriptomics (broad scale view of the active microbial community), cell counts (in a known sample volume), and will even grow (called culture) some of the microbes to determine what lives in the water/sediment. This type of research is important to understand the outsized role that tiny microbes play in nutrient cycling and larger biogeochemical cycles. Besides meeting new people and learning about different research fields , Caleb’s favorite part of life on the Palmer is rocking and rolling in the Southern Ocean’s huge ocean swells.
Caleb with his multicore sediments.
Over the last few days, we have sampled another superstation and took an add Kasten core! For now, I’m staying busy washing sediments in my search for living benthic organisms and microfossils. Next stop: McMurdo, Station!
Hello Expedition Antarctica! My name is Emily Kaiser and I am a 3rd year PhD student in Dr. Amelia Shevenell’s Antarctic Paleoclimate Lab. In my research, I am focusing on constraining when ice retreated in locations around Antarctica and what mechanisms forced ice retreat following the Last Glacial Maximum (LGM; ~25,000 years ago!). During the LGM, large ice sheets existed across North America (e.g., the Laurentide Ice Sheet) and were (we think, in some places) at their maximum extent around the Antarctic margins. I am interested in this time period because it is the most recent large-scale ice retreat event. Today, Antarctica’s ice sheets are continuing to lose mass at an accelerating pace, contributing to the observed global sea level rise. The two main factors driving ice retreat today are rising atmospheric temperatures and warmer water masses interacting with marine-terminating ice. Since the instrumental records of Antarctic ice mass loss and subsequent sea level rise are limited to the instrumental era, we turn to the geologic records to expand our view of how ice sheets responded to past climate changes. Our paleo data can then be incorporated into climate models to more accurately project the effects of future climate change.
I am a member of the scientific team on board the RV/IB (read: research vessel/ icebreaker) Nathaniel B. Palmer sailing down to the Ross Sea, Antarctica. Our expedition is supported by the U.S. Antarctic Program (USAP) that oversees and supports all US-funded scientific research in Antarctica. Specifically, this cruise is funded by a National Science Foundation grant awarded to geophysicist Dr. Phil Bart from Louisiana State University (LSU), who is the Chief Scientist on the cruise. Our cruise is scheduled to be 73 days long and split into two legs: NBP23-01 and NBP23-02. For the first leg, NBP23-01, we are sharing ship time with a group of microbiologists and environmental scientists. In mid-January, we are docking at McMurdo (the largest US base) where the group we are currently sailing with will disembark and a new set of scientists will join us for NBP23-02. I’m going spotlight NBP23-01 for now and will share info about the second leg when we’re docked at McMurdo. Here’s a hint: 🐧.
Our floating laboratory and home until March, the RVIB Nathaniel B. Palmer docked in Lyttleton, NZ.
Fun fact: In 2018, Dr. Shevenell and PhD student Imogen Browne sailed to the Ross Sea with the International Ocean Discovery Program (IODP) onboard the Joides Resolution. They were interested in recoveringsediments deposited in the Miocene (~23-5 million years ago!) to help us understand larger scale ice sheet evolution. Many paleoclimatologists think about the Miocene because atmospheric CO2 levels were similar to levels we are seeing today. You can read more about their cruise on this blog!
Where we’re heading! We started our journey in Lyttleton, NZ and are currently navigating around a storm in the Southern Ocean. Overnight, we experienced almost 30 ft waves as we approached 54°S.
Cruise Goals and Objectives
The goal of our research cruise is to explore the timing and mechanisms forcing retreat of the Ross Ice Shelf (RIS) following the Last Glacial Maximum. To achieve our research goal, we need to incorporate a suite of geologic tools: seafloor mapping, sub-bottom profiling, and sediment coring. I will spotlight each objective further as we begin science operations over the next week – but here is a quick look at what we’re aiming for!
Objective 1: Map the Gap
While we can use satellites to resolve the general seafloor beneath the Ross Sea, we need a finer scale resolution to see features either carved out by past ice flow or deposited during ice retreat. On this cruise, we are utilizing a multibeam echosounder to explore the seafloor geomorphology. This instrument emits sounds that bounce off the seafloor and return to a receiver on the boat. In the Electronics Lab on the Palmer, we will stitch these surveys together to compile a map of our survey site. In the bathymetric map shared here, the rainbow lines represent previous multibeam surveys while the grey shading represents satellite-derived. In addition to filling in gaps in our knowledge of Ross Sea bathymetry, our project will also contribute towards goals set by the Seabed 2030 Project – with a goal of mapping 100% of the sea floor by 2030.
Bathymetric map of the Ross Sea. The grey shading is bathymetry derived from satellite altimetry. The colored lines represent existing multibeam coverage on the shelf. Notice all the gaps in data? Our 1st cruise objective is to “map that gap!”. Figure courtesy of Matthew Danielson, LSU.
Objective 2: What lies below the seafloor?
Seismic surveys have an important scientific purpose: exploring what lies beneath the seabed. Unlike the multibeam echosounder that reflects sound waves off the seafloor, seismic surveys use a sound wave that reflects from subsurface horizons. Since each type of sediment has unique physical properties, we can use data coming back to the acoustic receiver to determine sediment type, layer thickness, and buried features we cannot see from the multibeam echosounder.
Seismic surveys require a special permit and follow mitigations to protect marine life. Thus, we are sailing with a group of trained Protected Species Observers (PSO for short), who are on watch 24 hours/day monitoring the presence/absence of local marine life. While transiting to the Ross Sea, we have had PSO briefings and trainings so we are ready to begin science operations when we arrive at our study site. We are following very strict protocols to require the PSOs conduct continuous visual monitoring of marine life around the ship. Their observations inform us when we can safely conduct surveys survey and when we are required to stop operations.
Fun fact: Two of the PSOs onboard graduated from the University of South Florida! Go Bulls!
Schematic of the seismic survey set up. The ship tows the source and a long line of receivers. Illustration from NOPSEMA.
Objective 3: Sediment coring
Once we complete multibeam and seismic surveys, we use that data to decide where we want to sediment core. The idea behind sediment cores is to collect undisturbed packages of sediment in the order they were deposited. With that logic, the sediment at the top of the core is the youngest and oldest material at the bottom of the core. There are a few different tools that we use to obtain sediment cores such as benthic grab samples, gravity coring, and piston coring. While all three of these techniques recover sediments, each one has a specific purpose. For example, grab samples are a great tool to see what is living just above and just below the seafloor. If you want to get a longer sediment record, you would use a gravity corer or a piston corer.
Once we bring the cores up from the seafloor, we put most of them into cold storage for future sampling. However, some core types and analyses require that we sample some of the cores onboard. The first step to sampling a sediment core is the visual description. We document things such as: sediment color, sediment type, abundance of microfossils, presence of any large rocks, etc. Then, each scientist goes in to take samples from the core for their post-cruise research. For example, I am interested in sampling these cores for radiocarbon dating and paleotemperature reconstructions. Other folks are interested in sampling for microfossils, sediment redox chemistry, methane concentrations, and more!
Types of Cores. The three examples shown here are some of the ways we are planning on coring. Figures from Project Oceanography.
Objective 4: Preserving cores for future generations!
The final cruise objective begins once we reach the shore. At the end of our cruise, we will disembark, and the cores will be shipped to the Antarctic Core Collection at Oregon State University for other scientists – and the future generations of scientists – to use! If you’d like to hear more about the core repository, check out my post from our visit earlier this year!
What’s next for NBP23-01? As we sail further south and into the Southern Ocean, we expect the seas to be rough for a little bit. But there’s another obstacle we need to cross once we’re closer to the Antarctic – sea ice! I’ll write again once we begin ice breaking!