text by Linda Welzenbach and Becky Minzoni; images by Linda Welzenbach
“Where’s the mud, people?” asks marine technician Joee Patterson from the doorway of the E-lab the morning of 6 March. If all goes to plan, THOR’s Hammer would deliver 8 cores of mud from the deep sea in front of Thwaites over the next 24 hours. As with most planned science aboard a research ice breaker in Antarctica, there will be successes, there will be set-backs, and there will be adjustments. By the end of the day, however, the THOR team get their mud.
The THOR team will tell the story of Thwaites Glacier from what they find on the seafloor. Until now the focus has been on multibeam mapping of the underwater topography, and the details of Thwaites’ story will be fleshed out through detailed study of the muddy sediments that rest on the seabed. Mud is defined in Webster’s dictionary as a “slimy, sticky mixture of solidmaterial with a liquid (e.g. water).” The mud that THOR seeks is slimy and sticky and at times even soupy, with consistency ranging from Nutella to chunky peanut butter, and other not so complimentary comparisons that are an endless source of amusement for the scientists.
For THOR, the sometimes pungent, green, brown to gray colored mud holds the key to their questions of how Thwaites Glacier behaved recently and back to the distant past. Seafloor mud contains bits and pieces of old Antarctic continent that hasbeen ground into sand, silt and clay by glaciers scraping the land. The ice carries its sediment cargo off the continent and into the sea. The seafloor mud hosts life at its surface, and remains of dead organisms as evidence of past ocean conditions. The sediment similarly traps water as it is deposited on the ocean floor, and records environmental regimes that operated below and in front of the glacier from thousands of years ago to the present day. These are the key clues that will help us tell Thwaites story.
The depth of the seafloor, even as we sail close to the ice shelf, is astounding. At Thwaites, depths range from less than 100 meters (300 feet) to over 1,200 meters (3,600 feet). To access the seafloor in Antarctica you need a ship that can remain “on station” without an anchor, that can battle ice, and that must be reinforced with steel framing and a winch system to deploy coring devices to great depths, where the gear becomes increasingly heavy. The captain and crew work diligently to monitor and avoid icebergs and sea ice during coring operations.
The coring device consists of a large weight on top of a metal barrel that is suspended from a wire and lowered through the ocean to the sea bottom. The barrel penetrates the seafloor mud like a straw, collecting up to maximum of 6 meters of sediment. Imagine trying to drop a skinny straw suspended from a thread through a glass of swirling milk with chocolate syrup on the bottom, and keeping it straight. In depths of a thousand or so meters, dropping the straw onto the ocean floor can take more 30 minutes, and it takes much longer to properly assemble and deploy the core device into the water. All the while the ship has to remain stationary, especially in heavy or icy seas, for the final drop so that the corer doesn’t end up leaning to its side or falling over. Most of the time, the corer successfully collects sediment.
How do we decide where to collect seafloor mud? Despite the astounding depths of the coring operations, site selection is not blind. Selection involves information gathered by the ships’ multibeam mapping and sound imaging of the mud and bedrock just beneath seafloor. Doing it well requires experience and interdisciplinary collaboration. The THOR team on NBP1902 includes three geophysicists who specialize in geomorphology (Rob Larter, Ali Graham, and Kelly Hogan) and a geologist who specializes in sedimentology and paleontology (Becky Totten Minzoni). Each project investigator brings their experience and expert knowledge to the table to target the best places that can create a complete picture of an area. They also have to consider the tools they will use to gather the best samples, within the constraints of time and manpower.
At each shift change the team meets to pore over both the recently collected multibeam bathymetric data and the Knudsen sub-profile imagery as it is captured in real time. For this cruise, the areas selected will tell a discrete story for the now ice-free ocean in front of Thwaites, yet also provide a framework for planning the activities during the THOR cruise next season. When selecting a site, the main characteristics the geoscientists look for are sedimentary layers (reflections in the sub-bottom profiler) from target depths that typically preserve shells, which are used to date the advance and retreat history of the ice sheet and ice shelf.
The team plans to gather eight cores. A suite of cores from three different sites will be taken along a transect from a deep basin to a high point near the modern ice shelf. All of these cores will tell the geoscientists about the recent retreat of the Thwaites ice shelf over the last century.
They pick the Kasten corer to use first. The Kasten is the primary go-to system employed to explore the seafloor because it can sample a variety of sediment types. The Kasten core results are then used to decide the next core type to use. The Kasten has a square barrel that is screwed together with plates to capture up to 3 m of sediment. Attaching weights around the square barrel up to 15 tons, the corer is sent to the seafloor by its wire tether at a particular rate (ranging from 10 to 30 meters per second). The weights and the speed of impact are optimized for extraction of different seafloor sediment densities and strengths. THOR team watches a monitor that displays the tether wire tension, both before and after the corer impacts the seafloor. An increase in the wire tension after it is pulled from the seabed is a first indication that tells the team how well the corer performed and how much material they may have collected.
After a long wait for one of the Kasten cores to resurface, the marine technicians Joee Patterson and Jack Greenberg settle the bottom end of the core into a heavy-duty metal “basket” mounted on the deck, allowing it to pivot gently, while draining some of the seawater from the top. Once the overhead winch is secure, the THOR team springs into action. The first thing is to preserve the integrity of the softer sediments in the top of the core with a perfectly cut foam block they have prepared. Once the core is separated from its top weights, everyone helps to heave the hundred plus pound full core barrel onto a cart. It is then carefully rolled across the deck to the Baltic room, where it will be carried into the lab for a long night of processing, sampling, and describing.
Muddy float coats, hard hats and unwieldy steel toed boots forgotten, we all hasten to unveil the sticky treasure within thebarrel that holds other worlds from the deep ocean beneath our feet. Once we remove the lids of the Kasten core barrel, it becomes apparent that the very top of the seafloor was washed out, a not uncommon result of Kasten coring, especially when the seafloor muds are soupy and soft. Immediately following this assessment, Becky Minzoni and Ali Graham quickly decide that the soupy seafloor surface absolutely must be captured from this site. That’s where the Megacorer comes in.
Unlike the single-strike gravity driven corers, the Megacorer is a set of 12 short precision hole punches. The tubes are mounted to a metal frame, that can be deployed with a wooden foot that can act as a “snow shoe” to keep it from pushing too far down through the soft, soupy sediment. When the tethered frame hits the bottom, a piston pushes the 12 tubes into the seafloor. A guillotine-like door closes off the bottom of the tubes and a lid seals the top of each tube. If the conditions are optimal, all 12 core tubes will be filled with 50 cm of perfectly preserved upper seafloor mud and sea water, and may also include the occasional squiggly Antarctic creature.
Yet, more often than not, some number tubes will be empty. Rocks, thick sticky mud, or tilt of the frame may impact the function of the trigger systems. The redundancy of 12 tubes provides more than enough material, and will capture at least some sediment even in less than optimal conditions.
An alternative to Megacores is the mighty box core. The box corer uses a frame similar to the Megacorer, but instead of 12 individual tubes, it forcefully inserts a metal box into the seafloor and then triggers a scoop that slides underneath to seal and hold the bottom.
The box core preserves the upper seafloor like the Megacore, but the box core does so as a larger and sturdier unit that provides more material in context. The box core is usually used for biological studies, and the sampling methods are flexible, allowing a variety of archiving tubes to be extracted from the sediment section. While the box corer was not used in the Thwaites coring transect, it was tested in an area of the eastern Amundsen Sea and will be employed in the 2020 THOR cruise.
Last but not least is the Jumbo gravity corer. The Jumbo is a metal barrel lined with PVC pipe, and has a heavy weight on its top that can capture up to 6 meters of sediment on this cruise. The PVC liner is extruded from the barrel and archived immediately following extraction. Extrusion happens on the deck right after it is secured at the surface. The core liner is pushed from the coring tube, cut into measured lengths, briefly described, capped and immediately refrigerated. It will later split into halves, with one half held as an archive and the other for sampling. These archives will be useful for years to come.
Within 36 hours, THOR deployed all but the box corer to collect 6 cores out of 8 attempts, but with end result achieving a full sample of the targeted transect, including both seafloor surfaces and long sediment records. As of the 12th of March, the THOR team completed 28 coring events resulting in 26 cores. Each one will provide samples to all the science team members and provide the foundation for a more extended coring strategy for next year’s cruise.
On the afternoon of the 21st, The Palmer began its 13-knot transit from Rothera to Thwaites Glacier. All our fingers were crossed that the ice would not prevent the Palmer from getting close to the ice shelf. The captain maintained that weather and ice conditions would determine just how close we would get to the face of the calving front, which would in turn determine just how much data we could gather beneath the shelf front with our now very well tested array of instruments.
The 26th of February dawns gloomy but calm, a perfect backdrop for the towering 30-40 meter wall of the eastern ice tongue, the crystalline face fractured and glowing deep teal to cobalt in the fissures and cavities. The Palmer glides slowly, 400 meters from the face of the ice shelf in front of Thwaites Glacier.
Arriving around 5 a.m., the Palmer begins to map the uncharted perimeter, the multibeam simultaneously mapping the seafloor in front and as far under the shelf as the angle of the sound pulse could extend. The weather for the next two days was expected to worsen, so this day was the perfect day to get as close to the shelf terminus as possible.
Thwaites Glacier ice shelf extends about 15 kilometers beyond the grounding line. The grounding line is where the glacier transitions from resting on the bedrock to a floating ice shelf in the Amundsen Sea. Along the 150-kilometer ice front, the satellite images show two different types of ice shelves. The eastern ice shelf looks like a large solid piece of ice. Moving west along the front (down in the image) the ice changes into what looks like alligator skin. That texture is created by crevassing of the ice as it moves past the grounding line. Once they move into the sea, the ice eventually breaks along the fracture lines.
This is the first time since 2000 that the Palmer has been to Thwaites, with only one other more recent survey conducted by the Polar Stern in 2006. Neither mission made it south of 74o 50’ latitude. The Palmer mapped a new ice-free boundary that is 18 km further south than in 2006.
As of the 3rd of March, the THOR team have surveyed more than 1,500 square kilometers of new seafloor. Upon reaching the eastern edge of the shelf, we gathered multibeam bathymetry and sub-bottom profiles. Sub-bottom profiles are pictures, almost like an x-ray view, of the first 10s of meters into the seafloor. Similar to the multibeam echo sounder, sub-bottom profiles are also created from sound, but using different frequencies and computer processing to generate an image that shows seafloor structure and sedimentary layers. These profiles are collected simultaneously with the bathymetry data to help the THOR team find places to collect core samples.
The other teams are also busy deploying the ocean water CTD’s (35 in total for all of Thwaites as of the seventh) and deploying gliders that collect ocean current and CTD information over a longer time period right next to the glacier. Lars Boehme and his team were gifted with a perfect day to look for seals on ice floes north of the eastern ice shelf, successfully tagging two of the four they found.
The Hugin also deployed on a 13-hour mission to conduct a survey of the seafloor. Its mission was to look for features of recent glacial retreat and measure Circumpolar Deep Water properties near the glacier front. Following its recovery on the afternoon of March 1st, the Hugin’s multibeam data revealed meter scale seafloor features, finer-scale features that complement the regional scale imagery that the multibeam bathymetry collects.
As of the 6th of March, THOR collected 14 cores from six sites, with the first three gathered in the early hours of the 27th from a site that was identified from the initial multibeam survey line at the face of the ice shelf. This first site is near what is possibly a former pinning point at the tip of the remnant Thwaites Glacier Tongue.
We wake early on the 7th to find ourselves gone from Thwaites. The Palmer is sitting quietly in the ice-free waters of western Pine Island Bay. We are there to conduct additional physical oceanography measurements and to collect moorings. Moorings are stationary instruments that collect ocean data over several years. The instruments are tethered to a weight that sinks to the bottom of the ocean. They are recovered by triggering a release mechanism that will allow the instrumentation to float up to surface for retrieval. They are sometimes hard to find because their original location may be caught and moved by giant icebergs.
Perhaps not so surprising when we arrive is that the Pine Island calving face has also retreated several kilometers since the last survey in 2017, providing the opportunity to survey the newly exposed seafloor. The ice-free conditions ensure that we can complete the oceanographic tasks and head back to Thwaites for a few more days of surveying (and hopefully coring!) on the far east side of the Thwaites ice shelf in an area that has recently become ice free. There and gone….but going back again.
The Nathaniel B Palmer is, without a doubt, one of most amazing places I can say I call home. It is taking us places that even those of us who are “Old Antarctic Explorers” have never seen. The Palmer can manage Southern Ocean tempests, dodge amazing icebergs, glide through sea ice, and is now charting new waters in front of Thwaites glacier.
Twenty-six people from more than seven nations and scientific disciplines (from marine mammal biology, physical oceanography, glaciology to geology) are focused on Thwaites Glacier. Yet regardless of our collective focus, each of us experiences life on board in different ways.
With nearly a month on board, we have all settled into some measure of routine, most of which (and most everyone will agree) revolves around chow-time and the shiftwork that defines our scientific activities. There is always something new to discover, but we are often reminded of what it was like at the beginning, trying to find our way (and our sea legs) around the Research Vessel/Ice Breaker (RV/IB) Nathaniel B. Palmer.
The following account was written at the beginning of the cruise, with the hope there would be time to talk a little bit about life on the RV/IB Nathaniel B. Palmer. The early Hugin testing, the very rough seas, and complex start to our cruise shifted that focus. As we are currently at Thwaites but experiencing yet another tempest (blizzard conditions- sustained 35-40 knot winds gusting to 50), we thought this would be a good opportunity to provide a look at what living on board a research vessel is like.
In the Beginning…. By Peter Sheehan
So, this is a big boat. Spread over six occupied decks, and with a vast underbelly of engine rooms and storage hangars built into the hull, the Palmer measures almost 100 m (300 ft) from one end to the other and has room enough for some 50 people. But what has surprised me most, even though, unusually, this cruise carries almost a full complement of scientists and crew, is how roomy things feel. Writing this blog in one of the many labs and work rooms that comprise the main deck, I have only one other person for company. People bustle up and down in the corridor – someone just waltzed past but by no means are we all sat on top of one another like inhabitants of a human beehive.
I have been aboard the Nathaniel B Palmer, the ice-breaking research ship operated by the United States Antarctic Program, for almost two days now, yet there is scarcely a foray out of my cabin that does not involve a protracted mix-up over decks, corridors – or even which end of the ship is which. I just went for a coffee and ended up in a laundry room. To exacerbate my problems getting around, all of the corridors have the same green doors and the same green laminate flooring. It is this disorientating similarity that makes a laundry room look a lot like a mess hall – dining room, to you and me – to the unsuspecting junior scientist.
The other thing that’s spiced up my first couple of days on the Palmer is the fact that everything has a silly name on a ship. The mess hall I’ve mentioned; the kitchen is actually the galley; bathrooms are called heads – go figure; and even words as ostensibly straightforward as front and back are, in fact, fore and aft respectively. The crew bandy (British to English translation is “ship speak”) these terms about with a breezy confidence, but to the uninitiated they add considerably to the brain fog – so don’t even think about asking for directions. I am assured that I shall know the Palmer like the back of my hand within another couple of days, but I am not convinced that people appreciate how heroically serious I am when I say I have no sense of direction.
The room that I was most excited to find on my misadventures was the sauna. My friends are always delighted when I talk about going on a science “cruise” given that there is not a piña colada in sight – and, granted, this is a far cry from hopping about Greek Islands with David Hasselhoff or the last surviving Bee Gee. But we have had two weeks in one ofthe coldest parts of the world: and although I’m still waiting for a swimming pool and a suite of sun loungers, I defy you to tell me that a sauna is anything other than a game changer.
The sauna serves a dual purpose. While arguably a place to unwind from long days of the hard work that comes with maximizing the science, it also provides warmth to a cold crew and scientists coming back from icy excursions or science-based deck work that can’t be accomplished in the labs.
The heart of science on the Palmer is located on the main deck, which hosts 3 dry laboratories. Two are computational (the primary one is called the E-lab) and one is for processing THOR Cores. There is one laboratory dedicated for biology and chemistry activities and includes a walk-in refrigerator that holds all THOR’s core archives and samples.
Scientists on NBP1902 spend most of their time in the E-lab. The E-lab is the nerve center, meeting room, seafloor mapping, Hugin mission control, CTD data monitoring and workstations for all the participants. The E-lab is our office on the sea. When not working, most of us can be found on the bridge, perched some 60 feet above the water line offering a 360-degree view of the world around the ship. The bridge holds a certain serenity, even during the worst of conditions, where one feels at once safe yet in touch with the wildest world outside.
Science is conducted 24 hours a day, 7 days a week. Everyone works 12 (and more) hours per shift to accomplish as much science as possible in the short window of a cruise. Weather delays, equipment adjustments and fixes, environmental constraints (mostly weather related, but theycan include ice issues) can create “hurry up and wait” situations. While we are always prepared to act on a moment’s notice, the in-between times may be filled with literature reading, data processing or ‘easy to pick up and put down’ creative activities. The E-lab has a stash of guitars within easy access, and there is no lack of musician scientists who make use of them.
At the end of the day, it is the 20 ship’s hands- captain and mates, engineers, seaman, oilers, cooks and 10 science support team members, keep us safe, well fed and ensure the success our science activities. It is an understatement to say that we all appreciate the hard work they do on our behalf. Life on board ship is not just about the Nathanial B. Palmer, it’s about the people who make it the most amazing and one-of-a-kind experience of a lifetime.
Peter is a postdoctoral researcher with TARSAN hailing from the University of East Anglia in the United Kingdom. Usually his field research takes place in the distant and warm Indian Ocean making observations of ocean currents and the fresh water that exchanges from the ocean into the air during the seasonal monsoons. Peter finds himself out of his element, you might say, in the icy reaches of Antarctica, but has taken to it well, helping to deploy the various TARSAN ocean instruments (including the CTD), creating visualizations of the ocean data as it arrives from the instruments, and providing hilarity through unending witty sarcasm to lighten the most mundane of activities.
text and images by Linda Welzenbach
On the 15th of February, the Palmer had to make an emergency transit to the closest base for a medical evacuation. Although EMT trained ASC staff can work remotely with doctors to solve many issues, some ailments require higher order facilities and care. So off to the British Antarctic Surveys’ (BAS) Rothera Station we go, located some 1,000 nautical miles north on the Antarctic peninsula.
Rothera station is a four-day journey at 13 knots (the fastest the Palmer can go), back through sea ice festooned with seals, penguins; breaching whales who taunted the photographers with their brief and distant appearances; and more icebergs whose myriad shapes and sizes continue to fascinate. But it is essentially an end to Thwaites glacier science for about 8 days if all goes as planned. During these days, the scientists slowly wind down from the intense energy associated with round the clock science, as if they are going into hibernation until we can return.
The morning of our arrival (the 19th) my roommate, THOR team lead scientist/coring expert Dr. Becky Minzoni, bursts in exclaiming that she would never forgive herself if she didn’t wake me (I am on the noon-midnight shift, so tend to go to bed late and not wake until mid-morning). Anticipating that what I might see is best viewed outside, I throw on everything I can think of, grab my 10-pound bag of camera gear and run up the 60 stair steps to the bridge. Out of breath already, the view literally finishes off what little is left. No matter, the view keeps me standing.
Mountains rising straight out of the water of Marguerite Bay, snow like smoke whispering away from the highest peaks and edges. Streams of ice, sinuous with hints of blue bending through the valleys between, the terminating glaciers cracked and crevassed where they make their way over the final bedrock hurdle into the sea.
Everyone is on the bridge.
The morning sun, low on the horizon and directly ahead, creates intense shadows on the mountains which fill the port side view as we round the eastern side of Adelaide Island. They seem close enough to touch.
It takes about 2 hours to go from Marguerite Bay to the small cove called Ryder Bay where Rothera station sits, nestled on the point of a low exposure of glacially carved volcanic rock in the shadow of Sheldon glacier. Within what seems like minutes ofour arrival, a small craft departs the wharf (which is under construction, preventing the Palmer’s berth, and why there is a ferry rescue operation).
By mid-morning the mood becomes restless with the need to get back to Thwaites. Since there is the better part of two days before the arrival of our new marine technician, a practice collection of a multi-core (known as a MEGACORE) as well as a possible Hugin deployment is suggested. The Hugin is not ready, so the MEGACORE activities proceed. Opportunities torefine and practice a complicated technique, time permitting, can only increase the probability of success later on. It also allows us to anticipate and plan contingencies when things don’t work out exactly how they are planned.
The next morning brings two pieces of news. The first, and most important, is that the mission succeeded; the patient has safely arrived in Punta Arenas, Chile, and will even be able to make it back home for treatment. The second is that we are stuck for another day. The weather in Punta Arenas prevented the return flight until tomorrow (the 21st). A possible visit to the station is also negated by 30+ knot winds, which frustratingly die down just after mid-morning. By this time the Hugin is ready for a test. The sea is amazingly flat and the air a balmy 2-3 degrees above freezing. Serendipity.
Unplanned events, planned contingencies and serendipity are expected when conducting Antarctic science. The next serendipity comes as a follow-up invitation from Rothera. We would be able to walk on land, tour the facility and send mail to our loved ones, but more importantly, our media experts will provide outreach for the British Antarctic Survey (BAS) by interviewing and reporting the work of other International Thwaites Glacier Collaboration scientists who just happen to be on station.
Rothera Point has been home to the BAS research station since 1975 and is the largest British research facility in Antarctica. It houses approximately 140 people, from staff scientists to the construction workers that are currently expanding the wharf. They maintain four Twin Otter research science planes and one Dash 7, the latter of which is solely for transport of people and supplies from Antarctica. The Dash flies to and from the station to South America and the Balkans 1-2 times per week. Rothera Station is one of seven bases the BAS maintains in Antarctica, plus smaller field stations used to depot fuel and supplies for field activities around the continent.
Onshore, we are met by BAS’ Mairi Simms, Rothera Physical Sciences Co-Ordinator and meteorologist, who will guide us through two laboratories: the Bonner laboratory from which all the Antarctic marine research is conducted, and the Bransfield House where much of the glaciologic and geologic research is conducted.
The Bonner laboratory is one story and, like most of the buildings of the station, is metal skinned and painted green. It is located close to the bay where samples collected by the science divers are easily transferred to special aquariums. We are met by Ali Massey, who is the lab manager. She shows us the pressure chamber used to decompress divers (when needed) and then leads us on to the experimental aquarium laboratory to talk to Dr. Melody Clark, who studies marine animals’ genetic evolution in response to climate change.
The lab is smaller than one might expect, but has not only her research charges (clams, snails and brachiopods), but a number of other Antarctic residents, from the many legged starfish of the genus Labidiaster, or the Antarctic sun star (and yes I thought it was an octopus too!), to the Sea Lemon (snail with a very interesting protective layer that looks like a lemon) sharing space with a sea spider and seaweeds (all of which are red!)
We go on to talk to Dr. Amber Annett, NERC Independent Research Fellow, and Sam Coffin, postgraduate and BAS Cambridge Research Scientist, who study the chemistry and sedimentary materials within glacial melt water that comes from the Sheldon glacier, and how it impacts the ecosystems of Ryder bay.
Back outside, we have to walk along the airplane runway (because of the construction) to cross into the heart of the station and over to Bransfield House, where we will meet up with Dr. Andy Smith, glaciologist who recently arrived from the field, to talk about preparations for next seasons Thwaites Glacier GHOST project. We also chat with Carl Robinson, head of BAS Airborne Sensor Technology, who is just back from flying a month of geophysical surveys along Thwaites Glacier.
Heading up the hill from the airstrip, we face an unlikely sight- a sleeping Elephant seal parked in the middle of a bridge. We are told that they adopted this spot many years ago, and Antarctic treaty regulations prevent interfering with the natives, so they get to stay; the BAS get to use a second bridge built a bit further away from the coast for thru traffic.
At Bransfield House, a large weathered wooden door with a metal bar as the latch looks out of place in the modern green metal skin. Also out of place on the new metal is a mounted wooden sign with pealing read paint and the letters of the station name carved into it. We enter into a vestibule common to all Antarctic buildings, meant to buffer the cold. Through two more doors, we meet Dr. Andy Smith, his own measure of weathering apparent being fresh out of the field. In an upstairs conference room, we settle down to talk about Thwaites Glacier science.
Dr. Andy Smith, one of the PI’s for International Thwaites Glacier Collaboration (ITGC) GHOST project, is just back from the 2018-19 BEAMISH field site where they conducted seismic profiling and hot-water ice drilling of the Rutford Ice Stream to characterize the bed below. The Rutford effort, like ITGC’s GHOST project, is part of a broader effort seeking to illuminate the past behavior of the entire West Antarctic Ice Sheet (WAIS) system.
His wiry frame is a testament to the 20+ years he’s been working in Antarctica. “Drilling is grueling work. You have to assemble and operate large heavy equipment for 24 hours over many days. Once we start, we have to keep going regardless of the weather,” Smith says of the field work they just completed. The ice cores show the structure of the ice to help identify the processes operating from the base to the surface, but also captures the rock at the bottom, the type of which has been a mystery. They set explosive charges that create localized shock- waves (like mini-ice quakes) that penetrate the rock below. When asked if these explosions might destabilize the ice, the response is that the charge is part of a well-tested technique that only produces a “small kick” to the ice. Seismic instruments measure the waves that bounce off the rock layers below, showing both the structure and makeup of the rock. Rutford is smaller than Thwaites, but is similar in thickness at two kilometers. Information from Rutford will provide similar information to what they expect to extract from Thwaites in during the 2020 field season using the same techniques.
The GHOST project will focus on the physics of how ice works- how it flows, what allows it to speed up, what holds it back. “THOR is looking at ice behavior in the past, we on the GHOST project are looking at how the ice works presently, particularly at the bed; what happens at the bed is a big factor of control over how it flows. We want to know the detailed bed topography, the places where its rough or smooth.” Prior work at Pine Island Glacier (PIG), which has been a main focus of the BAS, suggests that PIG and Thwaites (and their proximal boundaries) work together. As one changes, it will affect the other. They will also look for evidence that can be used to model future glacier behavior. For example, in a situation where the material below the ice sheet is soft and smooth, and wet and deformable, the glacier could move easily and speed up. Conversely if the topography is rugged, models may say that the glacier is better grounded.
“A rise in the topography under the glaciers is a good thing because they tend to stick there. But the bad side is that once they retreat from those points they tend to retreat quite quickly.” They want to try and understand at what stage the glacier might remain pinned there and then quantify the time scales for how long it will stay there. “At around 70 kilometers, which is not that far inland, it is a critical bit of information to know,” emphasized Smith.
With Thwaites Glacier, there is a time factor involved. “We think [Thwaites] has the greatest potential to surprise us in a not so good way. Part of the problem is that Thwaites has been hard to access, and thus far has been ignored because of that. Little information exists earlier than 25 years ago, so this collaboration should provide a large amount of the missing information,” says Smith.
When asked how the world at large can learn from the research and the challenges of gathering this information, Andy’s parting advice is to make the best plans you can. But also make sure you have contingencies to that plan.
“The secret to the work we do, in many ways, is to keep asking yourself ‘what if, what if, what if….’You can have a wonderful plan on paper, and it will change completely when you actually try to achieve it. Get used to change, work with it rather than fight against it. And hope you have enough contingencies to be able to know what the next best thing is to do…”
Lapsing into a thoughtful distant gaze, Andy mentions Scott and Shackleton. “Shackleton especially – his methods and leadership are used and put forward as good ways to deal with difficult situations. The principles and approaches of his leadership are also applicable elsewhere.” This, of course, makes me think of frontiers beyond Antarctica, such as space.
As a compliment to Smith’s research at BEAMISH, Carl Robinson, head of BAS Airborne Survey Technology, is just back from a month of flying geophysical surveys over Thwaites Glacier. His team uses a remarkable suite of remote sensing instruments, radars that cover a range of shallow snow to deep depth-sounding radar (which can see just below the rock-ice contact) as well as gravity and magnetic sensors that also look at the geology below the ice.
Robinson and his crew use Twin Otter aircraft, which need refueling before reaching the Thwaites Glacier field camp. After stops at BAS’s Sky-Blu and then BEAMISH sites, they actually begin their systematic surveys en route, similar to how NBP1902 takes continuous bathymetry during transit. Surveying requires good weather to allow for up to 4-hour flights at 1,000 feet, sometimes retracing a path to re-cross certain features like grounding lines (places where the ice shelf is fixed to the seafloor). “When we get close to the coast, the glacier features look more dramatic. You see heavy crevassing and bergs forming, reflecting the different processes that are happening internally, where the ice is moving over mountain ranges buried under the ice,” says Robinson with a smile.
This year’s data should provide a top to bottom look at the entirety of Thwaites Glacier, the effort of which is scheduled to be repeated over the next 5 years. Robinson emphasizes the importance of the multi-year effort. “This is a rare opportunity to see how the glacier changes over the next 5 years. Because of the way most funded grants work, surveys typically are only conducted during a single season.” The information will also be used by Andy Smith and the other GHOST scientists to decide where to take ice cores that will provide the best information about the glacier’s structure to help model Thwaites’s future behavior.
Within two hours of returning to the Palmer, the BAS Dash 7 arrives, delivering our new marine technician. Wasting no time, the Palmer turns her bow south, leaving the beautiful peaks surrounding Ryder Bay behind. Back to Thwaites Glacier we go.
text and images by Linda Welzenbach
Science advances in many ways, with enhancements in methods and instruments that improve the quality of the data we collect and enable the exploration of new frontiers. Yet despite all we know about our ocean, it arguably remains one of Earth’s greatest remaining frontiers. Add in icebergs, sea ice, and bad weather, gathering information from this frontier around Antarctica can be a real challenge! Yet many of the fundamental science requirements of THOR and the other teams that comprise the International Thwaites Glacier Collaboration depend on the collection of a wide range of data from the ocean that surrounds and interacts with the ice shelves around Antarctica. It turns out one of science’s most effective partners in this effort to collect data comes from some of the “locals”: the seals of the Antarctic oceans.
Beyond the obvious complications of dodging icebergs and plowing through sea ice, the ocean itself is incredibly complex; it is not just a body of bitterly cold, incredibly beautiful, deep blue water. The ocean is actually layered like a cake, where each water layer from top to bottom can have its own biota (from microscopic plants to megafauna such as whales), temperature, salinity, and currents (e.g. pathways) around the continent. Pathways are probably some of the most difficult types of information to track, and trying to understand how the water moves around the ice shelves is critical to understanding what is causing thinning of the ice shelf at Thwaites Glacier. That’s where the seals offer their help as rather unique partners in science.
Why seals? Because they can go places we can’t. They are amazing divers that also travel amazing distances. Since 2014, 14 Antarctic seal partners with their unique science payloads have logged more than 6,700 water temperature and salinity profiles within the Amundsen sea. This information tells us about the layer of water that causes melting and thinning of the ice shelf in front of Thwaites (and Pine Island Glacier) called circumpolar deep water.
Circumpolar deep water, or CDW, is derived from a mixture of all the world’s oceans. It originates from the outer ring of water known as Antarctic Circumpolar Current (ACC). The CDW moves from the deeper ACC up onto the shallower continental shelf (but still at depths of more than 300 meters!) carrying saltier water with a temperature of 1-2o C (which is above freezing and therefore melts ice). The CDW is several degrees warmer than the overlying colder surface water because that layer is supplied with fresh water from melting ice. We know this because scientists use devices to measure a temperature and salinity profile from the ocean surface to depths of thousands of meters. This device has the rather unglamorous name CTD, which stands for Conductivity (salinity) and Temperature with Depth.
Joee Patterson (see The J Team) led me into the warm and humid Baltic room, a large space with a noisy heater fan and floors damp from residual sea water. Next to the big black and yellow checkered door which opens directly to the ocean, the six-foot-tall CTD sits tethered to a strong steel cable that will not only carry this nearly 1,000-pound instrument 3,350 meters into the Amundsen Sea, but includes an information umbilical cord that receives data and allows scientists to also send commands. The MT’s are in charge of its setup, modification, and deployment. That day, the CTD had some interesting modifications – passengers, if you will – attached to the bottom ring of the frame. These were micro CTD’s, future riders on our seal science partners. They would be activated to gather the same data as their larger cousin and use the better resolved data set of the host CTD to standardize the temperature, pressure, and salinity data that the micro-versions gathered.
These portable dataloggers, or ‘tags’, were devised and constructed by Dr. Lars Boehme; he is a physical oceanographer at the University of St. Andrews, and works within the Sea Mammals Research Unit, Marine Alliance for Science and Technology Scotland, Scottish Oceans Institute. Over the last decade, he has tagged over 150 seals, to include nearly all the species from around the world. The programming in each tag can be modified to gather a variety of data types, from studies in seal behavior to information about their ocean environments by location. Lars’ knowledge and admiration of seals and their abilities is obvious in the reverence and enthusiasm he conveys when he describes their role in his oceanographic research and exploration.
As for his partners in Antarctica, he has been permitted to tag as many as 16 individuals from among the population of Elephant and Weddell seals who live near the Amundsen sea. The seals that are selected meet a very important qualification: they must have already shed their previous year’s fur. That ensures that the tag Lars and his team glue to the seal’s head is secure. After a year, the seal will molt again, shedding both the previous year’s fur and the tag. Using these partners has also led him to study their biology and ecology. The tag apparently has no impact on their behavior or normal seal activities. And it’s those activities that are critical to providing data about the water in places where humans cannot go.
Elephant seals are the champions of diving, logging marathon dives of up to 1,500 meters (5,000 feet) for up to two hours, although they typically dive 300-600 meters (up to 2,000 feet) for 20 minutes at a time, with 2-3 minute rests between each dive. Weddell seals tend to be shallower divers, only going to 600 meters for up to an hour. The water depths in the Amundsen sea near Thwaites Glacier range from less than 300 meters at the continent to 1,600 meters in the deepest glacial melt water channels, which scientists suspect may funnel CDW right to the base of the ice shelf. This makes the seals perfect natural explorers of the Antarctic shelf.
The day we visited an island among Schaefer group, Lars and his team were just finishing tagging a Weddell seal. After checking over the male Elephant seal, they determined that the big male was still molting and moved on to the other Weddell. After pulling on her fur, Lars deemed her a good candidate.
Seals are large and potentially dangerous animals, so they need to be sedated. This is where Lars’ skill and experience are important for the safety of the humans and the seals. From there, tagging is pretty straightforward. Using epoxy, they put a small amount on the bottom of the tag to make a sticky template on the seal’s head. More is applied to the template and then smoothed around like cake icing. The tag is held in place until the epoxy is set. The final step is to apply a bead around the edges, much like we do when we put caulk around our bath tubs. This keeps water from getting under the tag when they dive, which would lift it off the seal’s head.
At the end, Lars sits with the seal, putting himself between it and the water to ensure that the seal recovers fully before allowing her to return to the sea. Suddenly, as we are watching Lars quietly and reverently watch over his sleepy charge, the first seal swims by. Lars then says excitedly “Quick! Take pictures of the seal in the water!” In all his years of work, he has always focused on the animals and had apparently not taken any pictures of a tagged seal swimming.
The second Weddell seal was the fourth seal tagged since the start of the cruise. To date, the four seals have made 1,537 dives and collected 105 CDT profiles. Each time a seal surfaces, the data that they have acquired is transmitted via satellite to Lars and his team. They can even get a rough approximation of the location of the seal if more than one satellite picks up the signal. This is already more than we have collected from the ship, and the seals’ measurements are likely to far outnumber any additional ship-based measurements we can achieve by the end of the cruise.
The hope is that these partners for science, who live in the Amundsen Sea, will dive around and below the sea ice at Thwaites where we can’t go, bearing witness over the next year to the temperature and salinity of the CDW, reporting the data they collect to help us determine the path and extent of this warm water below the glacier.
text and images by Victoria Fitzgerald
As I face the glossy orange wall of the Louisiana born ship, the Nathaniel B. Palmer, I prepare to step off the deck and take my first step down the iced over rope ladder. I am getting off the ship to provide technical assistance and optically stimulated luminescence (OSL) field expertise to PhD student Scott Braddock and Master’s student Meghan Spoth, representatives of the Geologic and Historical Constraints (GHC) team. My mind races from fear to focusing on helping them accomplish their mission: collect organic material (e.g. bones, algae, fur, seashells) for radiocarbon dating of raised beaches on multiple islands in the Amundsen Sea. Their efforts will provide glacial-geology modelers with data to determine if modern Thwaites Glacier retreat rates have occurred in the recent past and if it was able to recover. This information will help us better predict sea level change. I quickly absorb the importance of the project before my mind jumps to the excitement in thinking that I will touch Antarctic land and not just sail near it for 8 weeks. I take a deep breath from beneath five layers of heavy winter clothing and bury my fear of small boats and the ocean. I think: Just step down, away from the comfort of the ship, and get on the Zodiak.
After we arrive, we stumble across a frozen rocky surface carrying shovels, survival bags, and other sampling equipment, looking for a place that won’t interfere with the wildlife, and is above the tides which could wash our gear out to sea. We find a high spot on some rocks and quickly change out of our float coats, the loud orange life vest parkas that (hypothetically) would save our lives if we fall out of the boat into the freezing water. We shimmy into additional dry layers for the long haul of beach combing and hole digging.
To say the wind hurts is an understatement. It’s -10°F outside and the wind chill is around -20°F; I look around and take in what will be the next 12 hours of my day. This isn’t an island for relaxing and drinking margaritas. It’s a stone desert filled with ice, penguin poop, and Adélie penguin parents who are running in all directions away from their tenacious chicks who are begging for another snack. I immediately identify with their struggle, having three kids of my own with insatiable appetites and the energy of a thousand Suns.
Oh, and there are Skuas, the equivalent of angry giant seagulls who dive bomb your head anytime you are near their chicks…which is often. They are everywhere and nowhere. The chicks are the same color as the rocks and it is difficult to see them until you train your eyes for their movement. This is my new priority.
I take a selfie in true millennial fashion and cover up my face. No time to correct my reflection in my sunglasses: my hands have started burning and my phone isn’t recognizing my finger anymore. We make our way to the beaches that Scott has recon’d using what we think of in the U.S. as old satellite imagery, thanks to the internet’s ease of access. Out here we are using two to three-week-old data. Every now and then we receive new ice imagery, but with limited bandwidth on our satellite internet comms and the ice constantly moving, we rely heavily on our experienced Captain and crew to steer us clear of danger and navigate us safely to our projects. We all hold our breath, hoping the beaches are ice free for sampling.
Good news! The imagery was fairly accurate. Even better news: we are further into summer and the beaches have even less ice than we expected. There are four of us, and Scott issues our marching orders plus a quick demonstration on what to look for before we split up into two teams on the hunt for organics. I’m with Scott, while Meghan wanders across the ridge line with Dr. Kelly Hogan, a British Antarctic Survey Geophysicist who has experience in this type of sampling.
As we start, I feel like we are playing a game, a great scavenger hunt, only here it is literal (and littoral!). Surface material can be difficult to find as the islands are littered with penguin remains. The bones of the recently deceased penguins or seals are not good samples, we need hundred to thousand-year-old bones, the ones that are bleached white, growing algae, and spongey looking instead of smooth nonporous surfaces you might find in that piece of chicken from last night’s dinner. After a few minutes of beach combing with little luck, Scott announces he will start digging and I should prepare sample bags.
We make quick work of all the loose cobbles and start using them to hold our gear and samples in place as the wind just won’t stop. Soon we have around 15 samples from at least 2 raised beaches. We are pretty proud of ourselves and decide we should check on the other team and have a hot drink break. Meghan’s side of the island wasn’t as productive and she has about half the number of samples collected, which is ok, because that in itself is new information about the islands in this remote part of the world.
These islands don’t have traditional windward and leeward sides. The land-based glaciers that provide us with a surreal background for our field work are causing harsh winds to push down the sides of the ice and across us. On the opposite side, the island deals with currents and tidal action from the Amundsen Sea. It’s rough, and so is my instant latte. We forgot stir sticks and all my powder is at the bottom of the cup. I gulp it down anyway so that I can put my gloves back on and get back to work. My romanticized notion of touching Antarctica has quickly morphed into reality: Antarctica is cold and desolate and I’m pretty sure it wants to kill us. We all finish, pack up our garbage, and go back to our respective beaches.
At around 9:30pm the Zodiak returns and we make our way back to our home away from home, our little bunk beds awaiting us on the ship. Our bags are successfully filled with penguin bones, seal fur, algae, and seashells. Scott and Meghan have another three days to collect their samples. I help out for two more days with similar results on other islands, but the wind is stronger, the penguin rookeries are more expansive, and Skua attacks increase. On the last day I remain on the ship. I want to help the “science”, but the previous day was bitter, and I discovered that I enjoy having feeling in my fingers! I traded out with another member of our THOR team, PhD student James Kirkham, who was just as excited as I was when stepping on the ladder the first day.
Completing island field work in Antarctica is difficult and requires a level of unwavering dedication to the cause. Scott and Meghan carried on and completed their portion of the International Thwaites Glacier Collaboration without complaint. I have a new appreciation for the GHC team’s dedication to unravel the mystery of glacier retreat in the Amundsen Sea.
We never did find a good spot to take samples using my OSL dating expertise, but we sure did try. A crew member, Joee Patterson, even made us a blacked-out tent from several tarps and some PVC pipe, just for the purpose of taking an OSL sample in complete darkness. If you’d like to know more about our continuing work at Thwaites, check out Thwaiterglacier.org or Thwaitesglacieroffshoreresearch.org.
Victoria Fitzgerald is a National Science Foundation Graduate Research Fellow and geology PhD student at the University of Alabama. She is a mother of three, Army veteran, and a first-generation college graduate. She likes science communication, rocks, and food, but not in that order. If you want to know more about her and OSL, check her out on Twitter @fitzofscience and at fitzofscience.com coming this summer!
text and images by Linda Welzenbach
Since leaving the Chilean coastline, the THOR team has been exploring the sea floor… with sound. Similar to the way that sea mammals communicate with each other over long distances and submarines avoid obstacles, scientists use sound to “see” the bed surface and ultimately map the ocean bottom. Sound waves are generated from beneath the ship from an instrument called a multibeam echo sounder which, in effect, is a giant loudspeaker pointing downwards and away from the vessel on either side.
Here’s how it works: the multibeam sends a “ping” (like you hear in the movies with submarines), a pulse of high-pitched sound that moves down and away from the bottom of the ship. It’s called multibeam because each ping contains 432 individual depth soundings that go out in the shape of a fan. The angle and trajectory of each sounding, the time traveled and distance away from the source of sound, combined with the properties of the ocean, (temperature and salinity) are used to calculate the velocity of sound through water. The result is a swath “image” of sound velocity, where the width of the swath is the maximum angle the outermost depth soundings have achieved as they travel some distance to the seafloor and back.
For deeper water, the swath will be wider; for shallower water, the swath will narrow. Each of the reflected soundings are then processed to show a continuous colorful ribbon, or snail trail, of the seafloor below the ship. (example snail trail image) The colors are equivalent to the distance the sound wave has travelled through the depth of the water, where the longest distances, which are blue, represent the deepest parts and the red colors are shallower features. Collectively they “paint” a picture of the seafloor’s surface in 3-dimensions.
Most oceanographic research vessels employ the multibeam echo sounder whenever they can, the combined results of which can paint a detailed picture of processes that we could never witness ourselves through the depths of the ocean. Marine geologists, oceanographers, and glaciologists studying Thwaites Glacier will use this information to unravel the processes operating between the ocean and the ice shelves. Features such as furrows and plough marks indicate past movement of the ice shelf and icebergs dragging along the sea floor, channels show where water flowed beneath past ice sheets, and high ridges or peaks may have been places where ice was once “grounded” (or resting on) the sea bed, a situation which may act to stabilize an ice shelf or glacier, and allay or even stop its’ backwards retreat.
The science team also use these echo sounders to make decisions about where to gather samples from the sea floor by producing an image of the layers of muds, sands, and rocks just below the surface. The samples help to decipher a longer history of how ice interacted with the ocean, and ultimately how the ice will behave in the future. The accuracy of the data is critical to ensuring that the location where those samples are taken will not be in a place that might damage the instruments (coring devices) used to collect the samples.
An important part of collecting accurate multibeam data is accounting for a variety of physical parameters. On the ship, we are effectively a bobbing cork in the ocean. Combined with the echo sounder, a set of reference points are made with each “ping” to account for this unpredictable motion. Similar to how a gyroscope works, the reference point data accounts for real time conditions such as roll (side to side) pitch (forward and backward motion), heave (the up and down motion) and yaw (the horizontal or side to side motion). The data processing software then applies clever corrections to make sure that the data accurately represent the true position and orientation of each sea floor sounding.
Two days after the ship’s passage through rough seas, THOR team members Kelly Hogan and Ali Graham noticed that the seafloor bathymetry data output suggested that the seafloor had a tilt when they knew it should have been flat. In order to understand if the tilt was real, they needed to do an experiment. They would have to go back over an area that had already been scanned, but in the opposite direction. The difference in the two data sets would show an equal and opposite tilt (if they were right that the tilt was in error) and it would help them calculate the degree of that error. In order to accomplish this, the seafloor would have to be flat and they would need about an hour’s worth of backtrack scanning of the same flat seafloor.
Enter the icebergs. The first significant iceberg that appeared was close enough to provide a terrific photo opportunity for the passengers, and the crew of Nathaniel B. Palmer made a spontaneous viewing loop around the iceberg. (pic of the first berg) The ship had also entered the Bellingshausen Abyssal Plain in the Southeast Pacific Basin, the flattest area of the transit before reaching the Antarctic continental shelf, so the sea floor conditions were optimum.
Another iceberg on the horizon looked to provide the appropriate distance and time it would take to conduct the necessary scan. Using that iceberg as a goal post, they made the first multibeam swath, rounded the second target iceberg (which was as photogenic as the first), and retraced the initial snail trail long enough to determine the degree of error and apply the correction.
Two icebergs later, the problem was solved and the colorful ribbon of seafloor bathymetry was returned to its horizontal self. These kinds of corrections are not uncommon and ensure that the data is good for when the THOR team reaches Thwaites itself, where the accuracy of the sea floor measurements will be important for selecting the best sea floor to sample and interpreting its history.
Here are some of the other icebergs we have seen on our traverse through the Amundsen Sea. They have been categorized by shape, age, and how they formed.