10/25 to 10/26/12: Last Day of Science

After sleeping for about 3 hours, I awoke to find that we were transiting to Spring Point, where we were going to attempt to install the new GPS station that we were unable to do on the way down due to fast ice. We arrived in Hugh’s Bay around 15:00 to discover that it was blowing 40 knots and there was no way to launch the small boats to bring people ashore. Gene decided that we needed a new plan, so we designed a depth transect of pocket basins from 300-750 meters deep. At each of these sites, we would collect surface sediments using a Smith Mack Grab sampler. Then we would do a CTD to determine the temperatures of the water above the site. This information may be helpful for further developing a paleotemperature proxy for cold waters. We also left the option open to collect one or two kasten cores.

With this new plan, my next 22-hour day began. The grab deployments are relatively easy and the sampling is even easier: a few scoops of sediment from 0-2 cm, and we are finished. Seems a shame, given it can take up to an hour of wire time. I caught a cat-nap and was awoken to deal with the second to last grab.

When I woke up, I was treated to the most beautiful views in the entire world. Of course, the pictures I took cannot do this sunrise justice. The ocean was a lake and the sun was glistening off the glaciers. WOW!

However, there was more work to be done. There was the potential to go back to Spring Point to try the install, but we had a noon end time to get on the road and head back to Punta Arenas. Gene, the Captain, MPC, and I met on the bridge in the morning sunshine and determined that Spring Point was too ambitious. So, we went back to our plan and hit the last site. Gene took over the helm and I went to sleep. When I awoke 3 hours later, they were bringing the last kasten core on deck. Right now we are working to process it… taking samples and archives. After that, science will be over. The cruise that started out as a potential scientific disaster due to sea ice has turned out to be pretty successful. We have done almost everything that we planned, minus my water sampling and the GPS installations, which will have to wait until another cruise. I leave you for today with our intrepid Chief Scientist…

10/25/2012: STUCK, again…

It all began innocently enough. After not finding the Gerlache Strait frontal boundary with our CTD casts, we held station and waited for the MT’s to finish re-rigging the JPC. Brad and I filtered more water, and waited. At 22:00, we were ready to put the JPC in the water and I had been awake since about 09:00. Surely this would only take a few hours, and then I would be off for a nap. Oh how wrong I was. Needless to say, we did not take pictures of the following ordeal, so I’m going to be a bit reckless and use pictures from previous days, so you can get the idea.

Deployment was smooth and we (me, Gene, the MTs, and our MPC) all gathered in aft control with the winch operator. Here I am entertaining in aft control; this is typical.

When the trigger core hit the bottom and the piston fired, we had a HUGE shiv (jump of the winch line through the block on the A-frame) and a double jump on the wire tension to 11500 lbs. Not large for a JPC on the other ship, the N.B. Palmer, but a big one for a 12 m piston core on the L.M. Gould.

We were pretty sure we had gotten into the glacial sequence, and began celebrating by eating Dove chocolates that I had been warming up in my pocket since we deployed. At about 8000 lbs of tension, the winch stopped. Just stopped. Oh NO! We were anchored to the bottom. To make matters worse, there were TONS of icebergs around. TONS! And some of them were Titanic big. The Mate on the Bridge was stressed and so were we. We woke up the Chief Engineer and the Captain, both who arrived shortly after and scratched their heads for a while.

The MTs and MPC tried to figure out what to do next. Should we cut the wire? How could we do that with so much tension on the line? Would we spool out the line and risk losing more wire? Would be have to launch a zodiac and cut at the water line? All of these options seemed too dangerous. As the mom in the room, I put my foot down and told them they weren’t going to do anything stupid. We tried pulling the A-Frame up to see if we could help the winch along that way, by adding extra tension. Nope, that didn’t work. At this point, it was 04:00 and the sun was beginning to rise. The Captain, our MPC, and Gene were about ready to make the call to cut the wire and leave the gear on the bottom, when the Chief Engineer called to say that he was going to override the winch from the engine room and start trying to tug as we moved the ship forward. It worked!!!!! The winch slowly creeped to life, and we were going to retrieve the gear. The only problem, we would have to stay AWAKE to do this!

At about 05:30, the JPC came on deck. We were all so tired that we must have looked as if we had just come through a war. The MTs and MPC helped me extrude and label the core liners as they came out. Gene and Brad brought them into the lab and started securing, labeling, and measuring the sections. At one point, in our tiredness, we stopped to observe the most beautiful sunrise any of us had ever seen… a white peak clearly illuminated by the glow of the morning sun. Then it was back to work.

While the MTs worked to break down the JPC and stow the gear, I worked with the two core catchers and the cutter nose to extract the sediment, while preserving the stratigraphy. Not only had we tagged into the calving bay facies (science alert: alternating diatom rich layers and clay layers that were deposited during deglaciation) but we had encountered a sandy interval with some pretty stinky hydrocarbons. I wonder if we got stuck when the sands flowed in around the cutter nose? That combined with the winch issue made for an exciting night. Here is a photo of the reconstructed bottom half meter of the core. The diatom layers are green and brownish, the sand and clay layers are gray.

At this point, it was 07:30 and time for breakfast; nothing like 5 meals in one shift. All of us went to bed pretty wiped out. Science can get pretty exciting and stressful sometimes. I’m just glad we recovered the gear, the core, and that no one got hurt.

10/24/2012: Going ashore and other science activities

While I was sleeping, Gene and the students went ashore at Duthier’s Point to change out a modem on the GPS station.

These GPS stations were installed to determine how much the crust beneath the Antarctic Peninsula has rebounded since the loss of the Larsen Ice Shelf and other ice shelves/glacial systems over the last 50 years. The swap-out went well and the Hamilton College undergraduates travelling with us came back super excited about trip ashore. Apparently, there were tons of penguins (and penguin poop) and seas as blue as the Agean. Too bad I missed it.

After the install, we transited back out to the middle of the Southern Gerlache. Our plan: to locate the frontal boundary between cold Weddell Sea waters and warmer Upper Circumpolar Deep Water, derived from the Antarctic Circumpolar Current. The interplay between these two water masses is what we think formed the Schollaert Drift, a massive pile of Holocene age sediments located seaward of the grounding line we had been interested in previously. Here is a 3.5 kHz image of the drift. If you look at it, you can see a bump coming up from the sea floor that has a lot of lines through it (image stolen from Willmont et al., 2007). These are different sediment layers of Holocene age (aside: the core we took a few days ago was located right under the black target symbol, because we were trying to target the unit under the drift sediments).

To look at the water column structure, we deployed the newly fixed CTD. Unfortunately, the frontal boundary was nowhere to be found. We moved farther south, thinking it might be a seasonal feature. Nope, wasn’t there either. At that point, we decided to stop looking, but to collect water samples to get a better idea of the sediments and biology present in the water column. We had intended to do this type of study in Palmer Deep, where I have done a lot of sedimentary geochemical work, but due to ice, this was the next best location. We sampled the bottom water, the mid-depth temperature maximum that is likely modified UCDW, and then the surface waters. Results TBD once we get back to USF and the microbiologists (who are way smarter than I am) take over.

We also finally (after several failed attempts) collected a kasten core at the site of our Southern Gerlache JPC. It was 1.5 meters of late Holocene sediments and will make up part of Katie’s Hamilton College undergraduate thesis.

At this point, days blend into nights, and back into days, as my 24-hour science shifts start getting more intense.

10/23/2012: Changing luck and doing science… for now

Well, a couple of things happened since my last post. We circum-navigated Anvers Island dodging growlers (small icebergs) in driving snow and 20-foot seas. This slowed our progress back to the Gerlache Strait. And, after all these days at sea, the students once again found themselves seasick, leaving the Assistant Professors in the science party to occupy the watch station. That afternoon, science pressure was relieved a bit when we learned that the National Science Foundation (NSF) had granted our request to extend the cruise by two science days to make up for our days lost to sea ice. After quick emails to significant others, we accepted the extra days and revisited our science plan.

We decided to rig a 12 meter jumbo piston core (JPC) designed to tag into the glacial/deglacial contact that I mentioned in my first Gerlache Strait post (the reason for our first seismic survey). We conducted another brief 3.5 kHz survey and found an excellent coring location. We arrived on station in the early evening and couldn’t have asked for a more picturesque coring station. The views of the sun setting over Brabant Island were amazing. We saw minke whales and watched seals feasting on squid that were coming to check out the lights on our boat.

Jack, our Marine Technician who usually drills lake sediments in Africa, prepared the JPC for deployment, a task that is more involved than deploying a gravity core. Deploying a JPC involves lowering the core barrel into the water, cocking the trigger arm, deploying the trigger core, while hoping that whole system doesn’t pre-trigger in the water column.

We ended up with an excellent 10.5 m core and obtained our target contact (and no comments on my hard hat, especially from the NBs out there. I couldn’t see, so I had to turn it around, even though the ratchet was in front).

The night went downhill from there. We tried to do a CTD (an instrument that collects information about the temperature, clarity, oxygen concentration of the water column), but there was an electrical problem that was shorting out the sensors and needed to be fixed. Then we tried a kasten core, but that came up with about 4 inches of sediment in the bottom. At that point, I hadn’t slept in 22 hours and was very cranky, so they sent me to bed.

10/22/2012: Evolution of a Scientific Plan

PIs and funding agencies can all breathe a collective sigh of relief. Cruise LMG12-11 has now recovered marine sediments from the Antarctic continental margin. And, they look pretty exciting, if I do say so myself.

I arrived for my midnight to noon shift at the same time as we arrived on station for our first jumbo gravity core. This core site was designed to target the contact between glacial tills and the calving bay facies that we see in Palmer Deep and in other locations on the Antarctic continental margin. If we can date this contact, we can better understand the mechanisms forcing the retreat of Antarctic ice sheets/glaciers/ice shelves after during the last deglaciation. We began the evening with a safety meeting on the bridge with the Captain and mates, technicians, and scientists. For all of you snickering seagoing marine geologists out there, this was a legitimate safety meeting, complete with forms to sign concerning the potential hazards and risks of working out in the back deck of a ship in a remote and unforgiving environment. Gone are the old days of showing up at a station and throwing stuff over the side.

I started the evening up in the aft control room with the winch operator (and a heater), while the Marine Technicians worked out on the back deck to rig and deploy the 6 meter jumbo gravity core. We lowered the coring apparatus through the water column at 50 meters/min. About 50 meters from the bottom, we stopped the decent and let the core hang and adjust, before firing it into the sediment at 50 m/min. If you watch the tension on the winch readout, you can actually see the core penetrate the sediments. After initial penetration, we spool out additional wire, and the core moves downward through the sediments on the sea floor. After about a minute (or 20 seconds, because Gene was impatient), we began reeling in the wire. As the core is pulled out of the mud, the tension increases dramatically, and is generally higher on accent, due to the now full barrel of sediment. At the surface, our trusty (or trysty as I originally wrote; queue more snickers from the marine geologists in the crowd) Marine Technicians, Amy, Jeremy, Jack, and Eric (our Marine Projects Coordinator) worked quickly to secure the core barrel so that we could safely extrude, label, cap, and move the core barrels quickly into the lab. We recovered 4.5 meters of sediment in JGC-1.

Once in the lab, Garret and I worked to clean and re-label the cores. We measured the magnetic susceptibility of the sediments by running them through a sensing loop. In Antarctic margin sediments, magnetic susceptibility tells us something about how much magnetic material is present in the sediments. This material is typically derived from terrigenous (meaning from the land) material that enters the system via glaciers and/or glacial melt water. Our magnetic susceptibility measurements indicated that we recovered the deglacial sequence we had been targeting.

At sunrise, we moved towards Hugo Island, where we would attempt the GPS install. However, there was too much sea ice around Hugo Island, making it impossible to launch a shore party. Gene and I quickly revised our science plan accordingly. We would travel to the northern end of Hugo Trough where we would collect another jumbo gravity core and a kasten core.

At noon, we arrived at Station 2, at the northern end of Hugo Trough. The wind was blowing 40 knots and it was snowing sideways, so we decided to forgo the kasten core, in favor of another jumbo gravity core. This time I was left in charge of the coring operation. Although I buried the core up to the bomb, the magnetics suggest that we recovered the glacial-calving bay facies and most of the middle Holocene. Lucky for me, the core can be easily compared to other cores in the region with existing radiocarbon chronologies.

With the winds raging and the swells picking up, we decided to transit back to the Gerlache Strait. This transit will take us 15 hours. We have a suit of measurements to conduct when we get to the Gerlache, including water column work, more sediment coring, and possibly a GPS install at Duthiers Point. Of course, this plan is subject to change.

10/21/12: Stand back, we are going to try SCIENCE!

Well, we are finally on our way out of Palmer Station and heading to Hugo Island Trough to start our real scientific work. After what seemed like endless days of waiting on the sea ice conditions to improve, it started to blow from the NE at about 20 knots last night. The wind loosened the pack ice just enough that we were able to set sail.

We pulled away from Palmer Station at about 13:00. Most of the station residents were standing on the pier to wave us off, and to wave off the last of the winter overs, who are going home with us. I think most of the station residents are glad to have us gone. Ship going folk and land lubbers don’t often have a lot in common (translation: we are loud and like to stay out late).

Now we are sliding through the pack ice on our way to out to the continental shelf. The weather is still beautiful and the seas are calm and ice covered. This makes for ideal coring conditions.

When we arrive at our study area, early Monday morning, we will be collecting several kasten cores and a gravity core. This site is similar to Palmer Deep, where I have done research since my Masters Degree, but there is a lower sedimentation rate. This means that the sequence does not have as high a temporal resolution as Palmer Deep for much of the sequence, but we are able to get older material than what was recovered at Palmer Deep; this older sequence is of similar or higher temporal resolution to that of Palmer Deep. We think that this older material was deposited at ~13,000 years ago, when regional glaciers were receding from the continental margin.

We will also do some water column work while Gene and one of the electronics technicians install a backup battery at the Hugo Island GPS station. During the summer, the station’s batteries are recharged using solar panels. Because there is little to no solar insolation in the winter months in Antarctica, the backup battery will enable the station to keep collecting and transmitting data through the winter.

Wish us luck! We are going to need it. I am on the night shift, so I should go take a nap.

10/19/2012-10/20/2012: You can check out any time you like…

I am really beginning to believe that we will never be able to leave. For the past three days it has been beautiful: sunny, cold, and dead calm. A high-pressure system has parked over us and nothing has changed.

So, why is there so much ice along the western Antarctic Peninsula this season if the region is warming at 5X the global average? Well, one hypothesis is that because the glaciers are producing more melt water, the surface ocean is freezing at higher temperatures and is forming fast ice along the coast. The ice that we are stuck in now is likely fast ice from Graham Land that let loose during the gale that blew from the south, creating the rough conditions that we experienced in the Bransfield Strait last week.

To protect ourselves from the pressure of the ice, we are tied up at the pier at Palmer Station. Here is a photo of the ship from yesterday. As you can see beyond the ship, there is a lot of sea ice. If you want to check out Palmer Station and the ship, and be the first to know if we are leaving, you can check out the Palmer Station webcam. It updates quite often and gives a good view of the station.

http://www.usap.gov/videoclipsandmaps/palwebcam.cfm

Here are two images of our region. The first image is a radar image from two days ago. Radar images are hard to get these days, due the loss of Envistat, the European Space Agency’s environmental observing satellite, earlier this year. I have marked the location of Anvers Island, Palmer Station, and the Gerlache Strait on this image. As you can see, there is sea ice all around the southern end of Anvers Island but the Gerlache Strait is open. If only we could get there. Remember, we burned 1 day of fuel going 1.5 miles from Palmer Station and the Gould is ice strengthened, but not an ice breaker.

The image below is a MODIS visible light satellite image from yesterday that we got from the National Snow and Ice Data Center. Because it has been so clear for the past few days, we can actually see the sea ice, rather than just clouds.

So, we continue to watch and wait. We just completed the Palmer Station cargo operations and the Palmer scientists are putting the finishing touches on their experiments. If we leave today, we may be able to get some science done. We have all of the coring equipment set up and secured on the back deck. We have the water sampling equipment staged in the labs. We have cleaned the labs. So now, we wait.

Waiting is frustrating because we want to be doing science, but it isn’t all that bad in the grand scheme of things. I mean, who wouldn’t want to be stuck in one of the most beautiful and remote places on earth with people who cook for you, glacier hiking, and more movies than you could possibly watch in a year (note: we have not watched Endurance yet). Yesterday, the science party went up to the Palmer Station kitchen where we helped to prepare 33 pizzas for the “Crosstown” Pizza dinner. The Science party, technicians, and the ship’s captain and mates ate pizza, salad, and ice cream with the Palmer Station crew.

After dinner, Brad, Gene, Dianna, and I suited up in cold weather gear and put on our snowshoes for an evening trek up the glacier. Gene took the opportunity to point out some things about the glacier that have changed since he has been coming to Palmer Station. For example, the calving front of the glacier used to be perpendicular to the water. Now that the calving front is firmly in the ablation zone (Science alert: the region of the glacier where ice begins to melt), we can see crevasses forming, and meltwater tunnels at the calving face; the calving face now looks as if it is tilting backward, rather than perpendicular to the water because of the ice loss in the ablation zone.

Here are some photos from last night. The first one is looking out to East to the Antarctic Peninsula from the top of the glacier above Palmer Station. As you can see, there is no open water there.

If you turn 90 degrees to the right, this is the view that you see… and here is yet another photo of Palmer Station and the Gould from the top of the glacier. As you can see, there is no open water (do I sound like a broken record?).

We just got the following status update from our intrepid chief scientist:

Hi All  just to let you all know where we stand in our discussions about exiting Palmer Station. This AM we met to discuss the status of the ice, given a new set of images and the weather we have been having. It is the unanimous opinion that to attempt to leave the pier at Palmer would not only be futile in terms of getting to open water, but would potentially present a dangerous situation for the vessel if we become locked in and drift with the pack. Just in the last 24 hours the pack ice has doubled back on itself, mushroomed so to speak, under a persistent push from the south. Winds are non existent out of any direction in our immediate vicinity, and the temps continue to be well below freezing (ie. -7.0 degrees right now). The Gould is not capable of making way in such ice–which has only gotten worse since we hightailed it back in here a few days ago. So please sit tight and continue to be supportive of each other.  thank you  Gene