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.