63º 05.455’S, 55º 23.75’ N
Because we were eager to complete sampling before ice conditions became too difficult to navigate, we initiated the JPC deployment before we’d completed collecting sediment from the Kasten core in the lab. The core had been almost entirely assembled days before. However, because temperatures were reaching as low as 0 F, there were a couple integral pieces that needed to be kept warm until the very last moment. The steel core barrel was ready to go, but the PVC liner that would house the sediment itself was being kept indoors, isolated from the wind and snow. As we neared the time of deployment, the students saw a flurry of activity as we helped the Marine Technicians assemble the remaining bits of Jumbo Piston Core.
Although the morning brought calm, relatively ice-free seas, when the day shift reported at noon, it quickly became apparent that conditions were deteriorating. The mates would not be able to hold the boat stationary with sea ice pushing against the vessel, and more importantly, against the wire suspending the JPC apparatus above the seafloor. We would have to put the complex core apparatus into the water, and simultaneously lower the wire and drift with the ice to the predetermined core station.
Unlike the Kasten core, which is weighted to penetrate the sediment, the JPC is set up in two parts. The longest barrel (in this case, 80 feet) is the piston core. The Trigger core, by comparison, is only about a meter and a half long. The trigger core touches the bottom first, and “triggers” the mechanism associated with the piston core, which then falls the remaining distance to the seafloor. Determining the ideal length of the free fall is one of the most difficult parts of Jumbo Piston coring. If the distance is too great, the barrel may settle awkwardly, and if it’s too short, there may not be enough momentum to penetrate the sediment. The PI’s use notes from past cruises and images from the sub-bottom profiler to calculate the ideal distance. In this case, the free fall was about 2 meters.
We were set. Both the piston and trigger cores were in the water, the free fall distance was calculated, and we were drifting with the ice to our core location. The coring went without a hitch, only taking about an hour to deploy and retrieve.
The deployment is really only half the fun, however, and the day shift’s next task was to dismantle the JPC and extrude 80 feet of PVC piping from the steel barrel. Being outside is always a pleasure, but as night drew closer, the weather took a turn for the frosty. Because the PVC had frozen within the steel barrel, we needed to walk up and down the length of the barrel, hosing it down with warm water. Walking kept us warm, but the fine spray from the hoses froze immediately onto our jackets, overalls, and hardhats. I didn’t realize the extent to which I was encased in a fine sheet of ice until I retreated inside and meltwater began to drip steadily from my clothing.
After an hour or so, we were able to extrude the first couple feet of PVC. With this success, the process went much more quickly. We cut the PVC into sections, labeled each one, and stayed unerringly positive in the driving snow. The entire night was so much fun, and we were all filled with a great sense of accomplishment at having filled an entire 80-foot coring barrel with a marine sedimentary record. And, because the JPC was taken close to the ikaite and shell-filled Kasten Core, we should see some of the same exciting features in the longer core.
All in all, the final station at Perseverance Drift was a great success. Impinging ice prevented us from staying longer, but we collected what we needed before we started the five-day transit north, across the Drake and back to Punta Arenas.
63º 05.33’S, 55º 24.65’ N
After the successful recovery of the whale bone mooring, we were excitedly looking forward to the final science station at Perseverance Drift, where we would complete the last sampling of the trip. We were hoping to collect a Kasten and Jumbo Piston Core (JPC), and complete some multi-beam sonar surveying of the seafloor.
The site, Perserverance Drift, is located between Joinville and D’Urville Islands at the northeasternmost part of the Antarctic Peninsula, and is characterized by extremely irregular seafloor bathymetry. The narrow Larsen Channel between the islands acts as an accelerating pipe for water moving from west to east. The sudden deceleration of sediment as the channel broadens results in a large-scale drift deposit system. Careful geophysical surveying was necessary to select a site appropriate for collecting an 80 foot JPC. We would need a thick sediment sequence and a swath of relatively even seafloor. We decided to collect both cores from the open area to the east of the Larsen Channel.
We recovered a beautiful 5-meter Jumbo Kasten core that proved to be a fount of interesting samples. We discovered many very well-preserved bivalves throughout the core’s length; several of the shells hadn’t even been disturbed from their life positions during sediment accumulation. Kara Vadman (Colgate University) unearthed a scaphopod, or tusk shell, at the very base of the core. The discovery of any shell material is vital because dating of carbonate material will place the core in context of the Antarctic Peninsula’s marine geological record.
Both shifts also discovered beautiful centimeter-long ikaite specimens in the lower half of the core. I was particularly excited that we’d discovered them after learning about the unusual circumstances of their formation. They were beautiful, yellow and prismatic. We hurriedly put them into vials and then into the -80 C freezer so they would not disintegrate at room temperature. It was my first time seeing fresh ikaite crystals, and it felt, appropriately, as though we had uncovered buried treasure.
The JPC was next on the docket, and we were all hoping that favorable ice conditions would hold out for a hiccup-free deployment.
Today was a particularly eventful day on the ship as we were making our final attempt at the whalebone lander that we missed on the way down. The whale bones attached to this lander have been on the ocean floor for two years collecting various life forms that benefit from the nutrients given off by the decomposing bones. The morning was tense as we had to find the lander once we released it from the sea floor. This job was made much harder when the large flag used to locate it by sight got caught under some ice and was not visible from the surface. Luckily one of the marine techs spotted the little yellow buoy that was attached to the flag and we were able to recover the lander. Once it was on deck several groups began working very quickly to do some initial sampling of the bones before the animals on them began to freeze. The Microbiology group swabbed various areas of the bones for DNA before anyone contaminated them by handling them so we had to move very fast in order to let the benthic ecologists get the bones into the warmth.
Once the ecologists had processed the bones that we wanted to sample further from, by removing any bone worms that were living on them, we took them for our own DNA samples. We will be looking at the different bacterial communities within the decomposing bones in relation to several geochemical aspects such as lipid content. In order to get these samples we needed to take cores of the bones with a specially made bone saw attached to a drill. We drilled from several bones and took at least two cores from each in order to have replicate data on them. One bone was particularly interesting since it expanded when we took it out of the saw, possibly indicating methanogens (bacteria that produce methane when breaking down the bone). We took extra samples from that bone in order to get a methane analysis as well as some samples for viewing the microbial community inside the bone. It was a very exciting day because we had been hoping to get this lander since we missed it in the first few days of the cruise and we found some very interesting specimens to sample.
For the last couple days, doing science and taking samples has been halted because of the thickening ice that has been impeding the ship from moving quickly. We had initially planned on going to a particular site where we thought there may be a cold seep, which would be very interesting to look at from a microbiological standpoint. However, the ice conditions were making traveling to the site difficult and slow. Since it is getting into the winter season in Antarctica, the ice is re-forming and is thicker than it would be in the warmer months. With this thickening, it makes it much harder to break in order to progress. This results in the ship having to often move backward in order to pick up enough speed to break thicker ice chunks. While we encounter larger, open water, channels that make traveling much easier, we are coming across thick ice much more often.
In order to try to avoid the worsening ice conditions, we changed our route to return to the Ikaite site that we visited at the beginning of the trip to take more samples and cores. Unfortunately, we were also unable to make it to this location, even after trying several different routes, and therefore had to change our plans again. With only a few days left before we have to make our journey back through the Drake Passage and back to Punta Arenas, our current plan is to go back to the locations of the whale bone landers and try, for a second time, to retrieve them. The hope is that the changing winds and moving storms, will push us and the ice farther out into the sea so that we are better able to get out of the ice and move north.
063° 56.87 S
056° 38.11 W
Easter Sunday on the Palmer was a day of transit for the most part, so there was time for a few holiday activities, such as egg dying and an Easter egg hunt. Eggs were dyed using the usual color tablets as well as with onion skins, a traditional method shown to us by Pavica Srsen, a Croation member of The University of Hawaii team.
The night shift was greeted by a sunny Easter morning just west of Rhoss Bay, although we were unable to approach the bay for science due to ice conditions. Most of the morning was spent on the bridge, enjoying the view and discussing new strategies for science operations. Maria Vernet, Chief Scientist, and Bruce Huber, Co-Chief Scientist, ultimately make the final call after assessing ice conditions with the Captain and Chief-Mate. It was decided to continue on to the Vega Drift with the intention to visit potential cold seep sites. Unfortunately, ice once again hindered this operation, and we are currently underway to a new site in the Vega Drift that was cored nearly ten years ago and is known to contain ikaites. As we have mentioned quite often in our accounts here, ice continues to be an obstacle, but the principal investigators make it a point to have multiple alternative plans so as not to lose any valuable time for science.
As we travelled further north this morning, the morning of April 9th, the Antarctic wildlife literally flocked to the waters surrounding the Palmer. As we cut through the ice just north of Vega Island, we created a trail of open water behind us for seals and minke whales to come up and breathe. The minke whales especially took advantage of the large area of water behind the ship so as not to strain their backs by cutting the ice and making their own breathing areas. Adelie penguins were also sighted frequently.
After our potential coring in the Vega Drift, we intend to continue north and again try to retrieve the whalebone lander that was meant to be our first science operation of the cruise. If all goes well, we will be overwhelmed with samples in these final days of science, from sampling the bones, megacores, kasten cores, and hopefully, a few jumbo piston cores.
64 31.9496 W
58 34.0405 S
With only a week until we start the 4-day transit back to Punta Arenas, the scientists aboard the Palmer have started to review the accomplishments of the cruise and plan for analytical work to be completed at our home institutions. In the two years prior to our departure, the primary investigating scientists used conclusions from past cruises to create the research plan for NBP12-03. One of the places we were most eager to return to was a site called the Vega Drift, in the Erebus and Terror Gulf of the Antarctic peninsula where the unusual mineral ikaite (pronounced ‘icky-ite’) has been found. Glassy and prismatic, several centimeter-long crystals of ikaite had been unearthed in sediment cores during past Antarctic cruises; we were able to recover them in the first kasten core from the Vega Drift. Geologists and biologists aboard hope to learn more about ikaite formation and its implications for studying paleoceanography
Ikaite found in Antarctica’s Vega Drift, is associate with rapidly accumulating high glacial marine sediment deposition near Vega Island in the Erebus and Terror Gulf of the northeast Antarctic Peninsula. The presence of ikaite in one of our sediment cores suggests that the sediment was deposited at a point where very cold water and high organic productivity prevailed- both of which are components of ikaite formation.
We often associate ‘mineral’ with coldly glittering diamonds or the brown tones of polished tiger’s eye. Lifeless minerals seem as far removed from animals as you can get. However, ikaite is different from diamond and tiger’s eye because part of its elemental composition is derived from organic, rather than inorganic carbon.
Microbes assist in the mineral’s formation by breaking down organic carbon from shells and other animal debris on the seafloor. The byproducts of decomposition, such as sulfate and phosphate, are dissolved into the sediment pore water. These compounds, in conjunction with increased stratigraphic pressure over time (as more sediment is dumped onto the seafloor) create an ideal environment for ikaite formation.
Our hunt for ikaite is yet another example of the efficacy of LARISSA’s collaborative theme. Professors Domack and McCormick are very interested in the importance of ikaite as a paleoenvironmental indicator, as well as the fascinating aspects of its formation. The three crystals which our group helped recover last month will add nuance to the multi-disciplinary body of ikaite knowledge.