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.
Paleoceanographer (Diatom Specialist): Rachel Meyne
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!