Hammertime: THOR’s Cores

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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.

Composite map showing previous seafloor bathymetry along with the Knudsen sub-surface imagery are similar to the kind of data that is used to identify core sites.

Joey Patterson tests the strength of the sea ice prior to deploying the Kasten corer.

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.

Night coring using the Kasten corer. The wire holds the top of the corer at an angle to allow the THOR team to put spacers into the top of the core. Just below where the wire is connected to the top of the corer are the weights that help force the barrel down into the seafloor.

Rob Larter, Ali Graham and Becky Minzoni compare the Knudsen sub-profile images with new bathymetry gathered after arriving at Thwaites glacier.

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 Palmer is amazingly agile for all its ice-busting power. It has thrusters on all sides that allow it to remain “on station” for a particular site so that it can deploy science assets from the starboard and aft sides of the main deck. This is particularly useful for coring, as different cores types can be deployed efficiently at the same site.

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.

Outlined on the board is a cross-section that represents a transect from the deep basin to the high point in front of Thwaites requires a variety of coring types, including the Kasten core, the Megacore, and the jumbo gravity core.

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.

 

Pictured Left to Right: James Kirkham; MT Jack Greenberg and the THOR team; Kelly Hogan and James Kirkham and the THOR team.

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.

Left- The THOR team (pictured left to right: Rob Larter, Ali Graham, Victoria Fitzgerald, Kelly Hogan, Rachel Clarke, Tasha Snow, Becky Minzoni) place the core barrel on the table. Right- Becky Minzoni removes the lid off the bottom most part of the Kasten core barrel.

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.

 

 

Crinoidea and Scotoplane

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.

Despite nearly 50 years of collecting and refining the coring process, the one constant is mud. Everywhere. Especially for the samples from the Megacorer, which need to be handled with utmost care in order to preserve the seawater/seafloor mud and the interface between them. It takes teamwork and good timing to extract the core tubes from the framework. Pictured Left to Right: Becky Minzoni, Ali Graham; Rob Larter and Ali Graham; Becky Minzoni, Victoria Fitzgerald

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.

MT’s and observers on the main deck look at the contents of the box corer. Beck Minzoni, Rob Larter and Ali Graham pull out one of the core samples taken from the box core.

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.

The core barrel is attached to a top weight, similar to the Kasten corer. Once removed from the weight the barrel liner holding the core can be pushed out and cut into sections. Pictured left to right: MT Jack Greenberg, Rob Larter, Becky Minzoni, Ali Graham; Ali Graham cleans and caps off the JPC core sections.

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.

THWAITES Glacier: There and gone

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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 unexpectedly calm waters enabled the Palmer to map at a quarter of a nautical mile of the calving front of the ice shelf.  Peering down the face of the ice into the water, one can barely see the 90 percent of the ice that rests below the surface.

 

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.

 

The many faces of Thwaites ice shelf.

 

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.

There was great hope, based on this mid-February satellite imagery, that the area in front of Thwaites would still be open when we arrived.  Weather plays a significant role in the movement of sea ice.  You can see the difference in the amount of cover on the western side of both images.  MODIS images provided by Christopher Shuman and NASA Worldview 

 

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.

 

The partial traverse of the Palmer at the edge of the ice shelf the morning of 26 February. Image courtesy of Johan Ronaldsson.

 

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.

 

The ice shelf currently extends 15 km beyond the grounding line, which marks the transition from the land-based ice stream.  The red track on 8 March 2019 ice data shows how quickly sea ice conditions can change over 5 days.  Today, we would not be able to survey the seafloor in that sector.  While the Palmer might be able to navigate it, the interferences caused by the ice would produce very little usable multibeam data.

 

This is what the western ice shelf looks like at its terminus. This section has been breaking up and retreating by about 10 kilometers since 2016.

 

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.

 

In addition to multibeam bathymetry, the THOR team collects complimentary sub- seafloor images that can reveal several meters of what lies directly below the surface.  The image shows “reflectors”- created by sound waves of a particular frequency that can penetrate below the seafloor, are reflected back to the ship and then processed to create this image of the seafloor contours, the scale of which is greatly exaggerated, and sedimentary layers.

 

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.

 

Bastien Queste manages the deployment and monitoring of gliders for California Institute of Technology and the University of East Anglia.  The gliders, who are named for whales (both common and famous names), are guided remotely from their institutions through satellite transmitted commands.  The gliders’ small size and lack of sophisticated moving parts allow collection of physical and chemical oceanographic information in hard to reach places for long periods at a time. They move up, down, and forward through the ocean by motorized internal mechanisms- oil bladders and weights which can be manipulated remotely.  Their multi-day missions at Thwaites will gather ocean current direction and velocity, sea water temperature, salinity, water pressure (a depth equivalent), the amount of chlorophyll in the water, suspended sediment, and the amount of dissolved oxygen in the water for specific ocean depths.

 

FOC/UK- permit No. 29/2018 Lars Boehme and his team tag two Weddell seals near Thwaites Glacier.  Several groups of Emperor penguins that were feeding in the water nearby observe the proceedings.

 

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.

Comparison of the seafloor in front of Thwaites as seen by the EM122 multibeam echo-sounder and the Hugin’s multibeam.

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.

Six coring sites and the 14 cores that were collected to try and sample a variety of depths and places that may record the past behavior of the ice shelf.

 

THOR team members Rob Larter, Becky Totten Minzoni, and Ali Graham look over the jumbo gravity core collected on the 28th of February.

 

 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.

 

Life on the Research Icebreaker Nathaniel B. Palmer

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By Peter Sheehan and Linda Welzenbach

 

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.

 

The Nathaniel B. Palmer at the face of the Thwaites Glacier Ice Shelf.  The ship’s close distance to the ice allows detailed mapping of the front and multibeam bathymetry.  The angle of the echo sounder beam extends beneath the ice edge to see the seafloor a few meters under the shelf.

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.

 

The E-lab is the nerve center and office space for all the science teams.  Everyone in the E-lab looking excitedly at the Hugin AUV high resolution side-looking sonar of the seafloor surface in front of the Thwaites ice shelf.

 

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.

News is posted on “The white Boards”.  Each day will list scheduled science activities, but may include training, lectures, and even social activities.

 

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.

THOR coring PI Becky Totten Minzoni consults the map of the 01 deck to locate the berth we would be sharing.

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 mess hall is located near the bow of the ship.  Its outer walls are right next to the ice breaking going on, making conversations difficult to hear at times.  The silver diner-like atmosphere is quite comfortable, with each table providing at least 20 different sauces, condiments, and spices to accommodate most palates.

 

One of the highlights of the Palmer is the fantastic array of baked goods, from handmade dinner rolls to a cinnamon “King cake” to start off the Mardi Gras season.

 

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 aft cargo hold not only holds two sets of propeller blades, but also a strapped down Ping-Pong table, a good way to manage stress through friendly competition and physical activity.  Peter and Chef Julian battle it out during the Transit Tournament.

 

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.

View from the bridge starboard catwalk of the deck 4 roof and starboard side with lifeboats down to deck 1. The entire ship can be viewed as you walk around the bridge catwalk.

 

 

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.

 

 

 

THWAITEing….At Rothera Station

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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.

 

“Grease” ice forms at the sea surface. This type of ice forms by direct freezing of seawater and is one of the first stages for formation of drift ice.

 

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.

 

Emperor penguin, Weddell seals, and Humpback whales

Adélie penguins

Peter I Island, an uninhabited Norwegian dependency

 

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.

 

 

THOR team works with marine technicians to assemble the MEGACORE and to practice extracting the tubes.

NBP1902 Chief Scientist and THOR PI Rob Larter caps off the archive sediment core extracted from a MEGACORE tube

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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.

 

Image courtesy of Aleksandra Mazur and the TARSEN Hugin Team.

 

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.

 

Halley research station will be closing as a result of the breakup of the Brunt Ice Shelf

A note left in a cairn in 1957 by J.M. Rothera, namesake of Rothera 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.

Island Days (Part II) – TARSAN Partners with the Natives: Seals!

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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.

This Weddell seal is not masquerading as a unicorn. The unique payload cap she is wearing is called a “tag”, a device created more than a decade ago by Dr. Lars Boehme, physical oceanographer at St. Andrews University in Scotland. The tag is a small computer that collects oceanographic information around Antarctica over the period of a about year. The “horn” transmits information by satellite about salinity, temperature, depth, and location to a web application so that scientists can monitor their partners in near real time. For more info: http://biology.st-andrews.ac.uk/seaos/introduction.htm (PERMIT NUMBER FOR WILDLIFE INTERACTIONS: FCO/UK PERMIT NO. 29/2018)

 

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.

The path of the Antarctic circumpolar current brings it in contact with many other bodies of water, including the Southern Ocean, the Atlantic, the Indian, and the Australian oceans. The ACC incorporates bits and pieces of those water bodies which then become part of the CDW. Amazingly enough, each of their contributions to the CDW can be identified by information such as temperature, salinity, biota, and more. These data aren’t just thumbprints of their source, they also tell us about the interaction and extent of these characteristics. It tells us that ocean water is dynamic and interconnected.

 

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.

The larger CTD device, also not terribly glamorous, can gather a lot of data in real time, if only in one spot. Its sensors send the information to a computer on the ship during its trip to the deep. The large gray cannisters are like giant test tubes that can be signaled to open during its passage, sampling the ocean water. Samples can then be used to measure things like chlorophyll (the amounts of which can serve to tell scientists how well the phytoplankton are doing) and oxygen in the water. They can also be preserved for future science that will be conducted at land-based laboratories following the cruise. The profiles provided by CTD’s have wide application for ocean modeling, and for THOR. The temperature and salinity profiles are used as part of calculating the sound velocity that provides the multibeam seafloor bathymetry data.

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.

Caption- Each tag is actually a tiny computer, battery and satellite transmitter (the antennae). The location, salinity, pressure, and temperature data for the depths the seal dives are transmitted each time the seal surfaces. The computers themselves are handmade by Dr. Lars Boehme and the Sea Mammal Research Unit Instrumentation Group at the University of St. Andrews in Scotland. While the hardware is modular, the programming can be modified to gather a variety of data types, from studies in seal behavior to information about a variety of ocean environments and locations.

 

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.

Lars Boehme approaches a nearly one-ton male elephant seal to see if he is a good candidate for a tag. The seal sees this as a challenge and expresses himself with bared teeth and a deep throated growling (that can really only be described as a very long, very scary belch). The trick to managing these encounters, according the Lars, is to appear taller than the seal. We were glad that he was the expert. Within a few seconds of looking the seal over, he walked away. The seal was still molting. (PERMIT NUMBER FOR WILDLIFE INTERACTIONS: FCO/UK PERMIT NO. 29/2018)

 

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.

This female Weddell seal is awake and entering the water about 20 minutes after the team finishes attaching the tag. She remained in the cove swimming around and back numerous times to check out our activities. (PERMIT NUMBER FOR WILDLIFE INTERACTIONS: FCO/UK PERMIT NO. 29/2018)

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.

Lars and his team are very experienced and very quickly settled the seal down in preparation for tagging. In addition to attaching the tag, they also record the seals size, approximate weight, and overall health. (PERMIT NUMBER FOR WILDLIFE INTERACTIONS: FCO/UK PERMIT NO. 29/2018)

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.

Lars Boehme and his postdoctoral research associate Gui Bortolotto carefully attach the tag to a female Weddell seal. (PERMIT NUMBER FOR WILDLIFE INTERACTIONS: FCO/UK PERMIT NO. 29/2018)

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.

(PERMIT NUMBER FOR WILDLIFE INTERACTIONS: FCO/UK PERMIT NO. 29/2018)

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.

Island Days (Part 1)- Geologic and Historical Constraints (GHC) on Glacial Advance and Retreat

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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.

 

Photos by Linda Welzenbach

 

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!

 

 

The “Iceberg” Correction

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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.

Each “ping” is displayed as a line of points. This image shows multiple pings. Each “ping” line is composed of 432 depth soundings – you may even be able to see the individual points.

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.

Icebergs are made of freshwater ice and compacted snow. They typically originate from the breakup of glaciers and ice shelves that terminate in the ocean.

 

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.

Turn captured on the multibeam swath image.

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.

These icebergs originated from Antarctica. They may be at least a year old, but their location in warmer waters will melt them very quickly, as much of their rounded surfaces are already showing.

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.

OTHER Icebergs…

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.

This is classified as a blocky multi- year freshwater iceberg because of its steep sides and flat top.

 

 

 

 

 

 

 

 

 

 

 

 

Drift sea ice is young flat ice floes formed from sea water at the sea surface that can move with current or winds.

 

 

 

 

 

 

 

 

 

 

 

 

 

Landfast ice or “Fast” ice is multi-year flat, solid ice made of both seawater and fresh water (from snow) that is attached to the far continental margin and can include grounded icebergs such as the one in the background.

The J-Team

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text and images by Linda Welzenbach

 

All field-based science conducted on board and beyond the Nathaniel B. Palmer would not be possible without the support of the Marine technicians.  They are in charge of on-board deck operations, ship to shore operations, and the safe deployment and recovery of scientists, scientific tools and equipment.

Within a day after leaving Punta Arenas, marine technicians Jennie Mowatt and Joee Patterson were tasked with the recovery of a state-of-the-art Autonomous Underwater Vehicle (AUV) that was being field tested in the Straits of Magellan prior to its deployment in the Amundsen Sea.

Jennie Mowatt will celebrate 4 years in her position in May; Joee Patterson, 3 years in May. They love their jobs and the great opportunity to problem solve. The work is always different, sometimes hugely frustrating but also hugely satisfying. They appreciate seeing Antarctica in ways most people never do. “We have seen the entire profile of the ocean around Antarctica- from the top to deepest depths. I have put my hands on creatures from 1,500 meters deep below the surface,” says Joee Patterson.

The pressure is on for the successful launch and retrieval of this “torpedo of science” that can accommodate up to 20 different sensors, including an obstacle detection sonar instrument in the nose cone.  The design is based on devices used by the petroleum industry and for national defense purposes; it takes advantage of the AUV’s ability to dive deep(up to 1,000 meters) but with payloads that will measure a variety of characteristics of the ocean, map the seafloor under Thwaites Glacier, and collect information on what is happening at the interface of both—something that was not possible until now.  Much was riding on this early test.

 

The morning of the test was perfect.  Cloudless skies were mirrored by the nearly still water of a small cove in the Straits of Magellan. The Hugin, built by the Kongsberg company (who also happen to provide the technology for multibeam bathymetry), is named for one of Odin’s ravens that travel the world to gather information.

Prior to launch, the science team meets with the entire Marine technician support group to go over safety and thesequence of activities. (pic of the big group) Jonas Andersson, one of the TARSAN scientists that manages the Hugin, rolls out the AUV from a specially made garage.

 

Once the bridle was attached and rigging set to lift Hugin off the ship, Joee and Jennie hopped in the zodiac to prepare for the AUV’s deployment.

With the Hugin in the water, the ship moves away and Jennie and Joee move in to watch over the AUV as it takes on water (shedding buoyancy) in preparation for diving.  Once it disappears, they return to ship.  Four hours later, the weather has turned ominous.  The skies are heavy, dark and spitting rain.  The winds have picked up and the sea surface is rough and rolling.  Hugin’s bright orange skin is spotted and Joee and Jennie are off in the zodiac to begin the process of bringing Hugin home.

Unbeknownst to those of us observing on deck, the marine technicians (known as the MT’s) had met and devised a plan, to include several contingencies for the AUV’s retrieval based on changes in the environment or equipment condition.  The first unplanned situation was the unexpected presence of a South American fur seal who found the AUV interesting.

“The seal was doing acrobatics while we were out there, and I thought it might jump in the zodiac. He came at us quickly and so I scooted the boat away, and then he just disappeared”, said Joee.

South American fur seal torpedoing through the air

Their first step was to attach the bridle system using the hooks on top that would be used to hoist the AUV onto the ship.  The plan was that one person would be in charge of maneuvering the lighter weight and buoyant zodiac while the other wrangled the two-ton AUV.

Assuming that the AUV would move more slowly and that the wind and the swells would impact the zodiac, their plan would take advantage of the zodiac’s maneuverability. The goal would be to tie the AUV to the side of the zodiac, which is a typical way of using a smaller thing to tow a larger thing. “Once we got out there, we figured out that our plan where one person did the maneuvering and one person to do the wrangling was not the optimum situation. The contingency was then to tow it astern of the zodiac. This presented other challenges.  The Hugin acts an anchor so we have to put a lot of power on the zodiac to get the Hugin to move at all.  Then once you get the Hugin moving you don’t want to get it moving so fast that it moves past you.  Add to that the swell and wind working against us as we try to keep a heading and keep it trapped behind us.”

Jennie summarized the complexity of the situation, “It was our first time working with the bridle system and we didn’t know how well the zodiac would travel with the AUV.  I definitely would not have predicted its hydrodynamic behavior as we tried to tow it behind the zodiac.  That was the thing that we couldn’t have predicted until we were actually doing it.”

 

 

 

 

Following the successful delivery of the Hugin to the deck, Jennie and Joee discussed adding a third person for next retrieval even if the conditions are calmer.  “It would be good to have more hands to pull the lines, and to use extra slip lines on the vehicle itself.  The weight of the bridal makes it want to sink, so keeping that in the boat will enable better control of the AUV.”

 

I was amazed at their perseverance and their calm under what was obviously difficult environmental conditions.  Yet for the J-Team, it was just another Friday at the office, and problem solving is why they are MT’s for science.

 

 

 

 

NBP’s Current Path Approaches the Second of Two Low Pressure Systems

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text and images by Linda Welzenbach

Waves approaching 15 feet are regularly inundating both the lower and the main deck (where our berth is located).  Viewing the maelstrom from the large windows of the aft winch control room where I’m sitting, I can forget the sea sickness for a bit as I watch the incredible power and beauty of the sea, eyes fixed on the distant horizon as a rocking and rolling NBP slowly but very steadily works its way south.

Large wave on the starboard side of the aft deck.

It is after 12, and I realize I have missed lunch, when a message suddenly comes from the radio telling everyone outside to come in due to heavy seas.  Feeling somewhat normal, and wanting to know how fast or how close the ship is moving into the outer reaches of the severe weather (very cyclonic looking in my opinion), I head to the bridge.  To watch us float about with all the ease of a cork in a bathtub, you wouldn’t know that the NBP is a 6,800-long-tons (15,232,000 pounds) ship with 3,000 (10’ x 40’) steel plates (the bow plates are 1 9/16 inches thick) carrying 425,000 gallons of gas.

 

The image on the left is a computer model of the low-pressure system. The NBP is the red target between 1016 and 1012 pressure contours. Right image shows the ship’s traverse to the Amundsen sea.

 

Meanwhile, below deck, science planning and activities persevere.

 

The monitors show the depth from the multibeam generated sound wave to the seafloor, 4426 meters (13,278 feet) and the reflected signal from two views. The range of color indicate depth-blues are deepest and reds are shallowest. Chris Linden, the NBP multibeam manager and expert, points out the location of the transducers that generate the sound waves and the instruments that will receive the signals that have been reflected off the seafloor.

 

The THOR team and NBP multibeam specialist Chris Linden set up the EM122 multibeam echo sounder to start gathering bathymetry information. As soon as the ship passed beyond the legal border of Chile, they would take advantage of the adjusted ship traverse to gather high resolution seafloor bathymetry from an area that hasn’t been mapped previously. There will be some challenges to acquiring the return signal: the slow ship speed combined with the rough seas that impact the ship’s hull create interference around the receivers (bubbles, for example), affecting the quality of the data.

Other ITGC scientists, whose constitutions are more stalwart than mine, sit at workstations and tabletops that are festooned with pieces of anti-slide fabric (much like rubber carpet pads) utilizing predrilled holes for eye-screws to which bungee cords are tied; these go over top of valued electronics to hold them in place.

 

Author Elizabeth Rush is ready for the rough sea crossing!

 

Tilt-o-meter and barometer on the bridge of the NBP.

 

Back on the bridge of the NBP, I stumble around still developing my sea legs as the motion of the ship is amplified due to its height off the water. The near 360-degree view of the waves is both captivating and hypnotic, helping to subdue some of the seasickness.  In fact, sitting on one of the control chairs is like having an unlimited ticket on the earth’s most incredible amusement park ride.

But as we roll upwards of 20 degrees each way, knowing that the larger sea is coming, the amusement fades for a few moments.  THOR team member and PhD student Victoria Fitzgerald adds, “There is no getting off this ride.” According to Chief Mate Rick Wiemken, there is a buoy in the area that has measured a wave height of 80+ feet. The highest wave ever recorded!

 

 

 

 

NBP pitches forward into a large wave.

One would think TARSAN’s successful deployment of the Hugin AUV would appease Ran (the AUV’s unofficial name), the Nordic goddess of the seas.   The crew of the ship are reassuring: the storm will still pass in front of us.  And while we will see a couple more days of rough seas, the Palmer (with 80 research cruises since coming into service in 1992) will handle it, and we will have gained a deep appreciation and respect for the amazing people who are taking care of us, and the forces of nature around us that we hope to better understand.