While the ARAON was positioned in the Larsen B and C embayments, we were able to collect a set of sediment cores to further expand our understanding of the Larsen ice shelf system. The core from the Larsen C provides an example of the current, active sedimentological processes along an ice shelf margin. Cores collected from the Larsen B captures any sediment deposited since the ice shelf collapse event. Beyond this comparison, these cores will improve the chronology of deglaciation at the end of the last ice age around 10,000 years ago. Reconstructing the size of the Antarctic Peninsula ice sheet and its demise is a major goal of the LARISSA project; sediment cores are one of many proxies used to unravel this geologic question.
Sediment core collection can be a tricky process. First, there needs to be sufficient thickness of sediment to collect. It is possible to estimate thickness using the sub-bottom profiler or “chirp” device on the ship. Although sediment is present, it is also necessary to place the core’s location in spatial context. What sort of geomorphologic features, or landforms created by geologic processes, is the core collected from? This information can be understood from the multi-beam instrument that reveals the bathymetry of the seafloor. Then the sediment core itself needs to be collected such that the coring process does not disturb the stratigraphic relationships. Marine scientists are particularly interested in the sediment-water interface, the boundary between sediment and the ocean in cores. If the sediment-water interface is maintained during the collection process then the modern environment of the seafloor is preserved. Marine scientists from every discipline are interested in this interval as it provides information about modern sedimentation rates, ecosystem and microecosystem assemblages, active geochemical and biochemical processes, and high-resolution, short-term chronology techniques. Everyone wants a sample of the sediment-water interface to analyze.
In order to provide all science teams with samples, the allocation of sediment from the cores is carefully planned. It’s a great display of teamwork and sharing between colleagues to ensure that everyone is able to analyze the sediment core and then share their results. While two disciplines may seem disparate at first glance, phytoplankton and Lead-210 abundance for example, individual proxies often correlate when results are compiled providing insightful interpretations. Tapping into the expertise of scientists from different backgrounds strengthens end results and optimizes the utility of the data collected.
While much time the past couple days was spent sampling sediment cores, the ARAON also sat in the Larsen B embayment for helicopter operations to glaciers and rock outcrops on the east side of the peninsula. The weather limited flying time, but the glaciology group was able to complete some work. Check out the link to the blog from the National Snow and Ice Data Center (NSIDC) on this page to learn more about that group’s activities.
While students on the Hill and fellow Hamiltonians in the northern hemisphere are enjoying sunnier days and warmer temperatures, winter is creeping up on us in the Antarctic Peninsula. The days are short, the sun hangs low in the sky to the north, and the sea ice thickens as temperatures and sunlight decrease. Yesterday air temperatures hovered just above zero degrees Fahrenheit. With foresight and prudence, the ship’s captain decided that our time was up in the Larsen to prevent the ARAON from becoming encased in the forming winter sea ice. In the afternoon yesterday, the ARAON began its transit north to move away from the eastern side of the Antarctic Peninsula.
The day before last, I woke up to find that the ARAON had returned to the Larsen B. Poor weather conditions canceled all helicopter operations, and the focus of the day was marine science. Since an ice shelf covered the Larsen B embayment for the past 10,000 years, the marine realm in this region is largely unexplored. Heavy fast ice and sea ice has furthered limited access, so it is quite remarkable to be here. The multibeam and chirp (compressed high-intensity radar pulse technology which simplifies the reading of sonar signals) data we collect here reveals new information every minute.
We spent the day with our eyes glued to the chirp looking for possible sediment core locations under the former Larsen B ice shelf. An ice shelf is floating glacial ice from land that extends and floats in the ocean, and unlike sea ice, is hundreds of meters thick. Ice shelves are sensitive barometers of climate conditions. They begin to disintegrate when average annual atmospheric temperatures rise above a -9 to -5 degrees Celsius. These features are also sensitive to oceanic conditions such as water temperature and salinity. If a warm, saline water mass begins to interact with an ice shelf (warm, saline = lower freezing point), the ice shelf can undermelt, placing further strain on its persistence.
When an ice shelf breaks up, it indicates local conditions are in flux. The Larsen B subsisted for the entire Holocene, or period of time since the last ice age. Using sediment cores it is possible to reconstruct past environments and use radiocarbon dating to constrain the chronology of climatic events.
Ice shelves limit calving of icebergs and sediment transport from the glaciers, starving these basins of sediment, and therefore, the sedimentation rates are quite low. This is sort of a catch-22: if we find sediment, it can provide an extensive time record of sedimentation, but it is hard to find sufficient sediment to core in the first place. Furthermore, during the last ice age the sea floor of the Weddell Sea was englaciated leaving behind hard, compacted till that is difficult to recover with sediment cores. We found a couple sites to core, but just as suspected, the amount of sediment recovered was quite thin and scarce.
In addition to sediment cores, dredging is another common technique used to learn about the seafloor. Along Cape Framnes, remotely operated vehicles (ROVs) discovered corals living on the rocky bottom, and dredging was used to attempt to collect some of these corals.
Corals in the Antarctic are akin to extensive tree-ring records from redwoods or sequoias. Corals depend on the influx of moving water containing nutrients in the water column. Since nutrients are remarkably scarce in the Weddell Sea, corals have existed possibly since the ocean reoccupied the area following deglaciation and grow very slowly. Since corals are made of calcium carbonate, they can be radiocarbon dated (telling us how old they are). They grow radially like trees. The layers on coral record changes in oceanographic conditions that are related to climate variability. Dredging, however, tends to destroy delicate features, so the coral we were able to recover was scarce. Nonetheless, what was recovered will provide exciting data.
The course of the ARAON took us as far south as sea ice permitted. We passed Cape Framnes to the Larsen C, the remaining and largest Larsen ice shelf. The vessel traveled below 66 degrees south, putting us almost within reach of crossing the Antarctic Circle. The survey, oceanographic and sedimentological data collected here is particularly valuable as it represents an active, intact ice shelf system. If the recent historical trend of north to south ice shelf collapse along the Antarctic Peninsula continues, this data will provide a baseline dataset to compare against a post-ice shelf collapse environment.
On the morning of April 20, two helicopter missions took off from the ARAON which is located just southeast of Snow Hill Island in the Weddell Sea. The flights had two purposes: 1) sea ice reconnaissance 2) repairing a GPS station on Robertson Island. The ice pilot, a special crewman who advises the ship’s captain on navigating sea ice, flew in one helicopter, and within a few minutes of being airborne identified at least two possible courses to penetrate through the sea ice to open water along the former Larsen A ice shelf area. This helicopter also scouted possible exit paths to ensure the ARAON does not spend the winter in the Weddell Sea.
The other helicopter flew to Robertson Island, the boundary island between the former Larsen A and Larsen B ice shelves. The first visitor to Robertson Island was Sir Earnest Shackleton on the infamous voyage of the Endurance nearly a century ago. Since then, very few people have journeyed there, and now Professor Eugene Domack has been there three times, and, by his account, more than anyone else!
After the helicopters returned to the ship, the ARAON navigated through a mesh of sea ice and icebergs to break through to open waters along the former Larsen A area. Without the flight information, it would have been nearly impossible to spot a path for the ship. After crushing through the ice and cruising by massive tabular icebergs, the ARAON made it to the open water in Larsen A.
Within the Larsen A, the ship’s path crossed close to a mooring placed nearly a year ago by LARISSA scientists on the RVIB Nathaniel B. Palmer. A mooring is essentially an anchored cable with oceanographic and sedimentological instruments attached to it at selected depths in the water column to continuously collect data through time at a given location. The ship positioned itself near the recorded coordinates of the mooring and electronically released it from the anchor allowing it to rise to the surface. As the sun set over the peninsula and James Ross Island, all scientists and crew went on deck to look for the mooring’s buoys. Just as daylight nearly ran out, the captain was able to spot the buoys and brought the ship to the mooring.
After the crew successfully obtained the mooring and carefully brought it on deck, we were able to recover all of the oceanographic instruments and sediment traps flawlessly. Everyone in the marine geology group was ecstatic to obtain this data set from the Weddell Sea, a frontier in the world’s oceans.
The ARAON continued its course south towards the former Larsen B ice shelf area, the site of an ice shelf collapse in 2002. The Larsen B was a stable feature for the entire Holocene, or the last 10,000 years, but due to rising regional surface temperatures and changing atmospheric patterns, broke up over the course of a single month. The ice shelf was nearly 720 feet thick and the area of Rhode Island - a catastrophic example of rapidly changing environmental conditions due to climate change.
Since the breakup event however, access has been highly limited as fast ice, or sea ice that fasts to land and glaciers, has choked much of the Larsen B area. The ARAON cruised as far west into the Larsen B area as possible and stopped along the current fast ice margin. The weather was on our side that morning with clear blue skies, and the glaciology group was able to conduct field activities on several glaciers that drain along the eastern side of the Bruce Plateau.
Just as the helicopters returned, however, the weather changed quite rapidly, visibility and temperatures dove, and the winds picked up. One of the meteorological stations on a monitored glacier nearby recorded a 20 degree Celsius drop in 30 minutes. We are in Antarctica heading into the winter - insane weather is to be expected! The storm worsened, and after the ship encountered 60 knot sustained winds (nearly 70 miles per hour), the ship redirected its course north with haste to avoid the storm and possibly becoming trapped in sea ice.
The following morning after the storm had passed, the sky was clear and the air was frigid and dry. Oceanographic and multibeam surveys were conducted for much of the day to further bolster our understanding of the Larsen A area. With improved weather conditions, the ARAON again headed south towards the Larsen B.
On the night of the 18th, the ARAON made record time in rounding the peninsula to arrive on the east side. As the ship traveled across the Terror and Erebus Gulf and circled around Snow Hill Island, we began to encounter sea ice. While most of my sleep was calm and quiet, I woke up around 7:30 a.m. to a grinding, crushing sound accompanied by jerking vibrations. We were breaking ice.
Antarctica is basically a circular shaped continent at the bottom of the planet with a long, skinny, mountainous arm sticking out north of the peninsula. Most of the southern ocean is open and uninterrupted by landmasses and the Antarctic Circumpolar Current (ACC) whips from west to east around the continent. Above the sea, the strong southern westerly wind field also circulates around Antarctica. When these forces encounter the peninsula, the ACC must circumvent the continental shelf of the Antarctic Peninsula and is redirected north through the Drake Passage. The ACC carries relatively warm, saline ocean water that serves as a moisture source for storms. The southern westerlies pick up this moisture and slam into the mountain belt that is the Antarctic Peninsula.
Although the peninsula lies partially north of the Antarctic Circle, meaning it is sub-polar and therefore does not experience complete winter darkness, it is still heavily glaciated due to the strong precipitation gradient, cold conditions and high solar seasonality. The western side of the peninsula and the Bruce Plateau receive high amounts of snow, and although it is slightly warmer, glaciers persist at low elevations. As the southern westerlies pass over the crest of the peninsula and are purged of moisture, the air dries and cools over the east Antarctic Peninsula. On the eastern side, these colder, drier conditions allow for the persistence of ice shelves, but due to lower snow accumulation rates, glaciers do not exist at this low elevation. Additionally, the Weddell Sea is much colder than the Bellingshausen Sea on the west side, further differentiating the peninsula’s climate. The colder ocean and atmosphere along with northeasterly winds supports and pushes sea ice towards the east side of the peninsula in the Weddell Sea, making access that much more difficult.
As I went on deck this morning to see our new surroundings, it felt much colder and drier. The scenery is completely different as well. Rather than towering, jagged peaks and fjords, the landscape is more subdued vertically, but massive icebergs, expansive sea ice, and ice flowing off of the Bruce Plateau make it quite impressive.
As the ARAON attempted to continue south towards Robertson Island, the boundary point between the former Larsen A and Larsen B ice shelves, we encountered thick, stiff sea ice. The crew aims the ship towards the ice, guns the engines, and lets the ship crash through and on top of the sea ice. The weight of the ship crushes the ice, but cannot always penetrate forward. The ship’s captain and ice pilot, an extra crewman who advises the captain on sea ice navigation, decided that the sea ice was too severe today and we have stayed put instead.
To optimize time today, the marine biology groups collected sea ice cores to analyze the phytoplankton assemblages and sea ice chemistry. The ARAON backed up into a zone of thick, sturdy sea ice, the crew laid down the gang plank, and a group of scientists, including me, left the ship to collect ice cores.
Our ice party collected sea ice the old-fashioned way with hand augers. The skies were blue, it was quite warm (especially in our special snow suit / PFD outfits) and a group of curious emperor penguins stopped by to watch us. It has definitely been a highlight of the trip!
We worked for most of the afternoon testing our collective strength against the 2.8 meter thick sea ice, and we were able to recover ice to analyze in the lab later. As we finished augering, the sun had begun to set, illuminating the skies and faces of deep blue icebergs with pinks and oranges.
Since our last blog post, much has happened. On the morning of April 16, the ARAON was stationed in Leroux Bay. Weather conditions remained poor, and the helicopters were unable to take off. As an alternative, the ARAON redirected course and continued south to the adjacent fjord, Bigo Bay. Like Leroux Bay, Bigo Bay was also a previously unstudied site. A multi-beam survey was collected from this fjord as well, and now all four fjords along the Grandidier Channel have been mapped.
Following the survey of Bigo Bay, the ARAON headed back toward Beascochea Bay that night. While in transit, the gravity core collected from Leroux Bay was opened, sampled and described by multiple science groups aboard the ship. The sediment will be subjected to multiple analyses providing insight into the paleoenvironmental history and current oceanographic and ecological conditions in the fjord.
On the morning of the 17, we arrived back in Beascochea Bay. Another CTD was collected from the fjord to further improve our understanding of local oceanic circulation. The weather finally became agreeable, and the helicopters were able to take off for a reconnaissance mission up and over the 6500 foot- elevation Bruce Plateau to the eastern side of the peninsula.
While the helicopters were away, the clear, sunny weather provided stunning views of Beascochea Bay. Valiente Peak ascends 7100 feet out of the ocean and has jagged spires of rock, hanging glaciers and spines of snow. Massive icebergs floated in the bay, but due to the immense size of the fjord, all sense of scale is lost. The sun rose from the northeast and rays of light illuminated the glaciated peaks in the fjord. It was, needless to say, spectacular.
During the flight, both helicopter crews observed a change in the sea ice conditions on the eastern side of the Antarctic Peninsula in the Weddell Sea. For a majority of the austral summer and just prior to the cruise’s departure, sea ice choked the Weddell Sea along the margins of the former Larsen A and B ice shelf areas and the Larsen C ice shelf. From the helicopter it was visible that the sea ice had detached and an area of open water was present.
When the helicopters returned to the ship, the senior science staff met and after carefully weighing the options at hand, decided to reroute the course of the voyage to the eastern side of the Peninsula. Within a few hours of the decision the ARAON was on its way to the east, passing around the western side of Anvers Island through the Bransfield Strait, turning around the tip of the peninsula through the Antarctic Sound and towards James Ross Island. The ARAON cruised quickly along this path average about 13 knots and early this morning, we arrived near James Ross Island, and encountered our first expanses of sea ice.
The ship is currently continuing its course south and navigating through the ice. We’ve seen Adelie and Emperor Penguins watch the ARAON moving by and scurry away as the ship breaks ice. Towering icebergs scatter the landscape, and the Bruce Plateau ice cap looms in the distance. Seeing the Larsen Ice Shelf B remnants, or even the Larsen C, is a once-in-this-lifetime opportunity, as the historical trend points to their full collapse as the region continues to warm in the future.
On the afternoon of Thursday, April 11, 2013 the LARISSA (Larsen Ice Shelf System Antarctica) science team and our counterparts from the Korean Polar Research Institute (KOPRI) disembarked from Punta Arenas, Chile, toward the Antarctic Peninsula on the Korean Icebreaker Research Vessel ARAON. The ARAON is the newest icebreaker on the seas today, and everyone from the LARISSA group is excited to join our Korean colleagues for this scientific voyage.
We spent a few days prior to departure in Punta Arenas - performing final preparations for the voyage and seeing parts of the famous port town. Preparations included picking up our extreme cold weather gear, gathering and organizing sampling supplies, packing cargo, and unloading everything onto the ARAON. Prior to setting sail, everyone in the group made sure to stop by the park in the center of Punta Arenas to rub the toe of the statue of Magellan for good luck crossing the notoriously rough Drake Passage.
After preparations were complete, the ARAON departed Punta Arenas for Cabo Negro to fuel up the ARAON for the month long voyage along the west Antarctic Peninsula. While the initial hope was to venture to the east Antarctic Peninsula, specifically to study the former Larsen A ice shelf area, severe sea ice would prevent the ARAON from either accessing or returning from that area, so a decision was made to journey to the western coast of the Antarctic Peninsula.
In the middle of the night, the ARAON departed from Cabo Negro. The first day of travel was along Tierra del Fuego in the Argentinian Bight. After 24 hours along the southern tip of South America, the ARAON entered the Drake Passage. This is my first time at sea, and luckily the Drake Passage was remarkably calm. In fact, veterans of many Drake crossings believe this is the smoothest they’ve ever experienced. During this time, the other students in the marine geology group and I began our 12-hour work shifts. During our first shift, we learned how to stand watch, to update the ship’s logbook and to use nautical charts. At one point, Natalie (a master’s student at Montclair State University) and I went to the bridge to observe ship information.
Due to the potentially rough seas in the Drake Passage, little science can be conducted. In order to fill time, members of our group have been presenting science talks. As an alum of Hamilton College, it was great to be able to sit in on another lecture by Professor Eugene Domack. Topics ranged from marine geology to terrestrial glacial geology to iron geochemistry in sea ice to ice sheet geophysics.
During the early morning on April 15, the ARAON approached its first destination on the west Antarctic Peninsula, Bescochea Bay. The goal at Bescochea Bay was to begin helicopter missions across the Antarctic Peninsula to install glaciological monitoring systems. However, due to poor weather conditions, helicopter operations were called off, and a second plan was enacted to travel to a previously unstudied fjord, Leroux Bay.
Leroux Bay is one of four fjords in Graham Land that is directly exposed to the open ocean. Ice reaches its greatest thickness on the Bruce Plateau in this region, due to the oceanic exposure. Leroux Bay is situated between Bescochea Bay to the north and Barilari Bay to the south and is fed by the Luke Glacier. By studying this fjord’s morphology, sedimentary record, oceanographic properties and biology, it will better resolve our understanding of this region of Graham Land both in the geologic past as well as the present.
Science activities in Leroux Bay included a multibeam swath bathymetric survey of the fjord to reveal the morphology of the fjord, sediment core collection, CTD (Conductivity Temperature Depth) surveys, ocean water sampling from various depths and areas in the fjord, and biological surveys of phytoplankton and zooplankton. These various activities span a broad swath of scientific disciplines. The intersection of differing, yet intimately related scientific fields allows for a comprehensive understanding of the Antarctic Peninsula as a whole.