Investigating permafrost on the bottom of the Beaufort Sea
What do an icebreaker, an autonomous underwater vehicle (AUV), permafrost and seabed mapping have in common? They are all part of a scientific research program underway in the Beaufort Sea. Geological Survey of Canada scientists Michelle Côté, Ned King and Mat Duchesne are investigating permafrost and gas hydrates in shallow Arctic shelf areas in the Beaufort Sea. They are trying to determine if this underwater layer of permafrost below the sea floor is being affected by climate change and are blogging about their research from the Korean icebreaker Araon between August 29 and September 13, 2017. Join Natural Resources Canada, the Korea Polar Research Institute and the Monterey Bay Aquarium Research Institute as they explore the sea floor of the Beaufort.
- Meet the Team!
- Arrival and Science Preparations
- A Century of Science on Herschel Island
- Multi-Channel Seismic Research Program on the RV Araon
- Using High Tech Tools to Explore New Areas Along the Western Side of the Mackenzie Trough
- Report from the Terrestrial Field Party
- Pingo-like Features (PLFs) and Mud Volcanoes on the Eastern Mackenzie Shelf
- What is a glacier? Understanding the glacial history of the western Arctic
- Arctic Wildlife Above and Below the Beaufort Sea
Meet the Team!
Michelle began her career at the Geological Survey of Canada (GSC) studying onshore permafrost and gas hydrates in the Mackenzie Delta. In the past few years, she has developed sea legs and has worked on research programs in the Beaufort Sea as well as offshore of the West Coast of Canada. Michelle has been involved in all three Araon expeditions to the Canadian Beaufort, and a big part of her role is in the permitting and logistics of these multi-disciplinary research programs.
Ned is a Quaternary geoscientist with experience in the shelf and slope marine environment on the southeast coast of Canada, Norway and more recently, the Beaufort Sea. He is a surficial (and shallow sub-seabed) geology mapper and has interests in past and present seabed processes including sediment transport, mass wasting and glacial framework reconstruction. His tools are primarily geophysical, mainly sonars and seismic, but he welcomes getting into the mud too, collecting long-sediment cores. Applications of his work include characterizing seabed conditions toward infrastructure placements such as rigs, pipelines, wind turbines and cables and foundation stability.
Mat’s area of expertise is reflection seismology. More specifically, his research interests are land and marine 2-D and 3-D seismic reflection processing and hydrocarbon detection using seismic methods. Recently his work has focused on the analysis of seismic reflection data to evaluate the potential of energy resources in Canada’s North, shear wave reflection seismology, environmental risks associated with the exploitation of non-conventional energy resources and seismic imaging in the Beaufort Sea.
Arrival and Science Preparations
The science team from Korean Polar Research Institute (KOPRI), Monterey Bay Aquarium Research Institute (MBARI) and the Geological Survey of Canada (GSC) assembled in Barrow, Alaska, on August 26, and we did a quick transfer by helicopter to the RV Araon, which was anchored just offshore. Within two hours everyone was on board, and we enjoyed our first meal on ship while the last of the gear was loaded onto the vessel. Then we began to unpack and settle in. Right on schedule at noon on August 27, we lifted anchor and began our transit to Canadian waters.
Photo 1: Two helicopters work in tandem to transfer all of the personnel and gear on to the RV Araon
Photo 2: GSC field party awaits their helicopter transfer to the vessel.
During our transit, lots of preparations have taken place. Each day starts with a science meeting where we discuss and refine the science objectives and tasks for the day. Science equipment and computers have been unpacked and set-up.
Photo 3: The Chief Scientist, YK Jin from KOPRI, leads the daily science meeting.
Repositioning equipment on the deck:
MBARI’s mini remote-operated vehicle (ROV) and automated underwater vehicle (AUV) equipment was loaded in Korea in early July after being used for surveys in Taiwan. There was great relief that all of the equipment transited in good condition. The miniROV and AUV were assembled and repositioned on deck for good launch and recovery.
Photo 4: Repositioning ROV winch on Araon deck.
Practice launch and recovery of AUV:
A challenging aspect of the AUV surveys is the launch and recovery of the vehicle, and this is the first time these tasks have been undertaken from the Araon. This morning, we anchored just off Herschel Island in preparation for the arrival of the Marine Mammal Observers. The wind conditions were light at 15 knots and the sea was relatively calm, which provided an excellent opportunity for practicing both the launch and recovery of the AUV.
The AUV was lifted by the crane and carefully placed over the side of the vessel. Tether lines were expertly used to control the AUV as it was lowered into the water.
We witnessed an excellent first deployment by the KOPRI crew with this new piece of equipment. They smoothly launched their Fast Response Craft (FRC) and the AUV recovery team proceeded to practice approaching the AUV and hooking the recovery line to the top of the AUV. This is not an easy task, particularly with 25 people watching you from the deck! This practice time has allowed the crew and the science team to tweak their methods and allows for smooth operations at sea when conditions will likely be more challenging.
Photo 5: AUV over the side of the Araon during the practice deployment.
Photo 6: KOPRI/MBARI recovery team practicing retrieval of the AUV.
A Century of Science on Herschel Island
Written by Scott Dallimore and Stephen Wolfe
As described in previous blog entries, the Araon science program began immediately upon crossing the Canadian border with bathymetric mapping using a hull-mounted multibeam sonar system and imaging of the subsurface geology with a sub-bottom sonar. After about 36 hours of transiting and science, the ship put in at Herschel Island to pick up three marine mammal observers to play a vital role while the ship conducts a multichannel seismic program. Scott Dallimore and Stephen Wolfe from the GSC are coordinating the logistics for the Herschel Island rendezvous with access to the site provided by Gwich’in Helicopters through the Polar Continental Shelf Project.
The flight from Inuvik to Herschel takes about 1.5 hours, crossing the Mackenzie Delta (the second largest delta in the Arctic) and then transiting along the north slope of Yukon. The scenery is indeed spectacular, as is the history of the area. Recognizing the unique character of Herschel Island, the Yukon Government established it as a Herschel Island-Qikiqtaruk Territorial Park in 1987 in accordance with the terms of the Inuvialuit Final Agreement.
The Yukon Government’s excellent web site http://www.env.gov.yk.ca/camping-parks/HerschelIslandQikiqtaruk.php explains that Herschel Island has been home to the Inuvialuit people for thousands of years as a base for hunting, fishing and whaling. The Inuvialuktun word for Herschel Island is “Qikiqtaruk,” which simply means “island.” Qikiqtaruk changed substantially after the first visit to the island by Sir John Franklin in 1826. By the late 1800s, the sheltered water of Thetis Bay and Pauline Cove attracted the burgeoning whaling fleet which, having depleted baleen whales in the north Pacific, was moving into the Beaufort Sea. The fleet established a whaling station with dozens of vessels over-wintering at Pauline Cover with a population, at times, numbering more than 1,000. This tumultuous time had substantial environmental and social impacts far beyond the depletion of the bowhead whales. Several historic structures are still standing.
Herschel Island has also been a focus for scientific research for more than a century. The first scientific expedition sponsored by the Canadian Government — the GSC no less! — worked from Herschel Island and nearby King Point from 1913 to 1916. In a small way, Scott and Stephen also have a long history of scientific research in the area. In 1986 and 1987, they spent almost 10 weeks working from small zodiacs as they studied the coastal and permafrost geology of the Yukon coast. The highlight of their trip was a stop at Herschel Island — which just happens to have a sauna mixed in with the historic whaling structures! Scott was just a new GSC scientist at the time, and Steve was a summer student, who shortly thereafter became a permanent employee at the GSC in Ottawa as a permafrost scientist.
Figure 1: Scott Dallimore (GSC) enjoying a tasty camp meal during 1986 summer field program.
Figure 2: Steve Wolfe (GSC) working with field samples collected during 1986 summer field program.
Figure 3: Steve examining the sediment exposures along Yukon Coast, summer 1986.
Thirty years later and there are still research topics to pursue! The interest during this field season is to undertake a reappraisal of all things glacial. A key objective is to consider and document the correlation of the offshore geology, which will be studied from the Araon, with the terrestrial geology present on land. Interest in this topic was stimulated by Scott and Charlie Paull, a scientist from the Monterey Bay Aquarium Research Institute (MBARI), when they visited a terrestrial exposure on the Yukon coast in 2013 and observed a sedimentary diamicton deposit with very large boulder-drop stones. This unit looked very much like the glacial deposits that we are finding offshore in our remotely operated vehicle (ROV) dives and geophysical studies. Scott, Charlie and Michelle Côté, GSC scientist, spent three days camping at Herschel Island in 2014 to sample cobbles.
Figure 4: 2014 field party of Charlie Paull (MBARI), Malcolm Nicol (GSC), Michelle Côté (GSC) and Scott at Herschel Island. Pauline Cove and some of the historical structures are in the background.
Figure 5: Michelle and Charlie preparing cobble samples at the docks at Herschel Island in August 2014.
This summer, Scott and Steve will be taking a close look at the sediments that make up Herschel Island as they appear to have formed by glacial ice thrusting of ancient marine sediments. There are very distinct ice-thrusted ridges on the island and outcrops of buried glacial ice from the Pleistocene glaciation. In addition, they will be sampling glacial sediments all along the Yukon coast to the Alaska border to document the origin of these sediments.
Multi-Channel Seismic Research Program on the RV Araon
A key objective of this research program is to improve our understanding of subsurface geology and permafrost and gas hydrate distribution. We hope to quantify the occurrence and release of fluid and methane gas at depth with an aim of understanding sediment instability, both landslide-type and fluid-related.
The primary geophysical method used to asses this scientific question is marine reflection seismic, which involves transmitting controlled acoustic (sound) energy through the ocean into the seafloor and recording the energy that is reflected back from the different layers beneath the sedimented surface of the seafloor.
Figure 1: Schematic diagram of the RV Araon with the multichannel seismic equipment deployed
Seismic data acquisition depends on the generation of pressure (i.e. seismic or sounds) waves. Devices called airguns produce a seismic wave when compressed air is released into the surrounding water. The sound waves produced by the airguns travel downwards to the seafloor and into the sediment below. Some of the seismic energy is reflected back from the top of any of the underlying layers and returns to the surface where it is recorded with listening devices called hydrophones. The hydrophones are housed within a streamer that is towed behind the ship. The streamer on the Araon is 1.5 km long and is towed at 6 m below the ocean surface. The vessel travels at approximately 8 km/h (5 knots) while we are surveying.
Figure 2: Streamer for the multi-channel seismic system being deployed from the rear deck of the Araon.
During our expedition a two airgun array will be used, with a compressed air volume of 420 cubic inches. This array is particularly well-suited for producing an image of the different layers from the seafloor and below, to a depth of about 1000 m. This seismic configuration contrasts with oil and gas industry hydrocarbon exploration programs which use much larger volumes of compressed air (energy) and can image many kilometers below the seafloor.
Five days of our research program are dedicated to conducting a seismic survey along very specific lines of interest. Many of the lines will target features and zones we know exist but need better data to interpret their origins, while some lines fill in gaps across virtually unexplored territory. We hope to collect about 1000 km of seismic data along 12 -14 survey lines. The resulting seismic images will be used to assess the regional geologic framework of the Beaufort Shelf and slope, to identify the history of sedimentation in the Beaufort Basin, to identify any potential gas hydrate and permafrost present, to understand the glacial history of the Beaufort Sea, as well as to determine geohazard issues related to submarine instability and landslides.
Figure 3: KOPRI and NRCan scientists monitor multichannel system data acquisition from the lab.
Our research program implements many mitigation measures, developed in consultation with Fisheries and Oceans Canada, to minimize the impact of our research on the environment and, specifically, during the acoustic surveys, marine mammals. One such measure is to have Marine Mammal Observers onboard to watch for the presence of marine mammals within a 1000 m safety zone around the vessel, both before and during seismic operations. The seismic data acquisition can only begin when this safety zone is clear of marine mammals for one hour. If a mammal enters this safety zone during the seismic operations, the airguns are immediately turned off. The Marine Mammal Observers then determine when it is safe to resume operations.
Figure 4: Marine Mammal Observers, John Ruben, Dale Ruben and Rhonda Reidy, on the Bridge of the Araon.
The seas have calmed and then sun is out today. After lunch we were treated to a spectacular view of snow capped mountains surrounding Mackenzie Bay to the south in Northwest Territories of Canada.
Figure 5: Snow capped mountains surrounding Mackenzie Bay.
Using High Tech Tools to Explore New Areas Along the Western Side of the Mackenzie Trough
With the great potential for oil and gas deposits, the geology of the area underlying the Canadian Beaufort Sea on the eastern side of the Mackenzie Trough has been extensively explored over the past five decades. Thus, a wealth of data exists in this area, including: multichannel seismic data looking deep into the subsurface; large swaths of multibeam data used to make detailed maps of the seafloor, much like topographic land maps; nearly 100 oil and gas industry exploration wells drilled hundreds of metres into the seafloor; and hundreds of five metres or less cores that have been taken for scientific purposes.
In contrast, on the western side of the Mackenzie Trough, east of the U.S.–Canada border, very little data exist, just some low-resolution maps of the bathymetry, a handful of detailed multibeam and low quality seismic lines, and one oil and gas industry well.
As we begin to investigate the western side of the Mackenzie Trough, we aim to understand the seafloor processes occurring there and will compare these findings to those for the eastern side. Much like early explorers who mapped, charted, and described unknown regions of the earth, we, too, are exploring relatively unknown areas, but with high-tech tools instead of compasses and sextants.
With only 15 days of ship-time, we need to target our studies to develop a solid understanding of what looks like postage stamp–sized areas within the maps of the vast area of the Yukon Shelf/Slope.
These high-tech tools increasingly become more precise as we home in on areas of interest. First, we used existing maps of the Arctic Ocean seafloor to identify areas of potential interest. These maps are at a poor resolution — imagine looking at something that is out of focus. We use educated guesses to select targets and use our first tools discussed in the previous post: the ship-based multibeam sonar system to produce a more detailed map of the seafloor and the sub-bottom profiler to produce images of the sediment layers below the seafloor.
These data are collected continuously as the ship moves back and forth along lines, much like mowing a lawn. The results are intriguing. The first impression is that seabed features are similar to those of the eastern trough and include deep scars that cut into the continental shelf and broad flat swaths of seafloor punctuated by mounds, gullies and ridges potentially associated with gas or water release.
After days of ship-based data collection and multibeam data cleaning — inaccurate soundings in the data must be cleaned to make the map useful to geologists — a base map is produced that can be used to find areas of interest so that we can deploy even more precise sampling tools: the high-resolution mapping autonomous underwater vehicle (AUV) and the remotely operated vehicle (ROV).
Photo 1: Examples of multibeam bathymetry collected by the Araon (left) vs. data collected by the mapping AUV (right).
Once areas of interest are selected from the low-resolution, ship-based maps, a mission is designed and sent to the AUV, which then autonomously surveys the seafloor for 16–20 hour missions. The maps are of such high resolution that we can image seafloor features one metre in size.
While the AUV was collecting data during its long mission through the afternoon and into the night, we began using the sub-bottom profiling data we collected to select locations to target for gravity coring.
To get a core, the coring assembly — consisting of hollow steel pipe fitted with a plastic liner — is lowered to the seafloor while suspended from a steel wire. Above the pipe is a heavy lead weight that drives the pipe into the seafloor. The coring system we are using can have steel pipes that are up to 6 m long and has a 250-kg weight at its top. At locations where the sediment is soft, the pipe and liner fills to the full 6-m length with sediment; when the seafloor is hard, we may only get 1–3 metres of sediment or less. The coring system is then pulled out of the sediment and winched up to the surface.
Once back onboard the Araon, the sediment-filled liners provide samples of how the sediments change with dept. Most of the samples will be sealed on the ship and returned to the laboratory at KOPRI, where they will be analyzed in detail using a variety of techniques to determine various properties, including the age of the sediments, their type and source, and the chemistry of water trapped between layers and grains of sediments. Among the topics of special interest is the question of what conditions were like 10,000–12,000 years ago.
Photo 2: a 6-m long gravity core assembly on the back deck of the Araon.
The final and most surgically precise tool in our modern-day tool box is the remotely operated vehicle, or ROV. Outfitted with a high-resolution video camera, a robotic arm, push cores and a sampling box, we survey the seafloor by “flying” the ROV over terrain that we determined to be the most promising from the multibeam bathymetric maps. These ROV ground-truthing surveys allow us to examine, discuss and sample material just like geologists do on land.
Fortunately we do this all while staying warm and dry within the ROV control van. In the last two days of surveying with the ROV, we have conducted four dives, collected approximately 30 rocks and eight push cores. Two push cores were collected in a patch of bacterial mat growing on the seafloor and released a trickle of bubbles upon collection, indications of the presence of methane gas.
Photo 3: ROV pilots in the control van collecting push cores from the seafloor.
Surfacing from its 18-hour deployment, the autonomous underwater vehicle (AUV) was recovered using the small boat and returned safely back on the deck of the Araon.
After three hours of data processing, the initial results revealed a stunning seafloor topography, with linear scarps, elongated depressions and ridges that are usually parallel with the shelf edge. There are also circular mounds up to 10 m high, often with collapsed summits. To our knowledge, the only place where comparable topography has been mapped is on the eastern flank of the Mackenzie Trough. Clearly this finding suggests that — whatever the processes are that form this unusual morphology — they are occurring on both sides of the Mackenzie Trough. The multi-channel seismic data collected at the beginning of the program will help establish the reasons for these similarities.
Photo 4: Scientists retrieving collected specimens from ROV and Araon crew securing the miniROV to the deck.
A great deal of analysis that needs to be done on all these data once they’re back at our respective laboratories onshore. Using all of these tools helps scientists to develop a more complete understanding of geological processes that have occurred and are occurring around the Mackenzie Trough region.
As a result of poor weather, with winds up to 40 knots, we are unable to deploy the AUV or ROV on this day. Thankfully, the Araon is a very robust vessel designed for rough seas, and we weathered the storm quite comfortably!
Report from the Terrestrial Field Party
Written by Scott Dallimore and Stephen Wolfe
As described in our August 30 blog entry, the 2017 Arctic field program also includes a terrestrial component, with Scott Dallimore and Stephen Wolfe from the GSC examining the coastal geology of the northern Yukon. For Scott and Steve, the field program is a bit of a trip down memory lane as they worked together on this coast 30 years ago.
In addition to providing logistics support for the Araon field program, they focused this year on observations of terrestrial landscape evolution in response to the ~2°C climate warming in that has been experienced in this area in the past three decades.
They also were looking for correlations between the marine and terrestrial geology, specifically examining evidence for glaciation that could have an origin from offshore ice shelves rather than terrestrial sources, and to record the character of marine sediments from the offshore that have been ice-thrusted and now reside in the cliff sections of parts of the Yukon Coast and on Herschel Island.
Araon returns to Hershel Island
At 6 p.m. local time on September 4, the Araon arrived at Herschel Island to offload marine mammal observers (MMOs) Rhonda Reidy and John and Dale Ruben. It was a rather majestic evening, with the Araon beautifully framed in front of the Barnes Mountain range. The ship held position about 1.5 miles offshore, and their able small boat crew brought the MMOs to the protected waters of Pauline Cove. Scott in particular was very pleased to see the Araon and boat crew as not being on the ship had been nagging at him a fair bit. All hands were very keen to briefly catch the flavour of historic Herschel Island and hear stories of the muskoxen that had been wandering along the shoreline just a few hours before they arrived.
They were also very pleased to report that the multichannel seismic program on the Araon was a terrific success. Aided by calm waters, excellent equipment, skilled operators and an absence of marine mammals (which we did not want to disturb) the program had met its research goals. Shortly after the crew transfer, Scott, Rhonda, John and Dale moved to Inuvik as a team by helicopter, arriving there at 11 p.m. in twilight conditions. The demobilization day also involved demobing all of the fuel drums that Scott and Steve had used over the past five days.
Photo 1: Araon stationed offshore of Herschel Island. Photo 2: Small boat crew on Hershel Island with a very happy Scott jumping on board the zodiac!
Photo highlights of the terrestrial geology program
The north coast of Herschel Island is characterized by a sequence of tilted beds that form ridges on the surface of the island. The ridges are composed of marine sediments that are almost certainly similar to the sediments imaged at depth by the Araon during the multichannel seismic program. The terrestrial exposures give a rare glimpse at the sediment properties and character and the dip directions of the bedding sheds as well as insight into the glacial forces that caused them to be tilted. A fascinating aspect of the geology of Herschel Island and many other locales along the Yukon coast is that glacial ice is still present in the landscape. Large retrogressive thaw flow slides are now exposing this buried glacial ice and rapidly eroding the coastal landscape.
Photo 7: Coastal exposure at border between Yukon and Alaska. The sediments exposed at wave level are glacial in origin, with large cobbles and boulders derived from the Canadian shield. They were sampled and described to see if they are similar to those sampled offshore on the Araon.
Photo 8: Exposure at about 1,400m elevation in the Richardson Mountains northeast of Aklavik, Northwest Territories. Dallimore and Wolfe sampled and described sediments to see if the mountain tops had been glaciated.
Over the past five years, marine geology studies conducted by the research team on the Canadian Coast Guard Sir Wilfrid Laurier and the Korea Polar Research Institute (KOPRI) Araon have gathered evidence of glaciation in the offshore near the shelf/slope transition. These observations seem to indicate a marine record of glaciation that is different from interpretations derived from terrestrial mapping efforts. The 2017 field program included examination of terrestrial exposures all the way from the NWT–Yukon border to the Alaska border. Emphasis was placed on making observations beyond the so-called all-time glacial limit by flying in the helicopter upslope from the coastal plain to the mountain tops. We successfully sampled and characterized more than 20 field sites covering more than 200 km of coastline.
Pingo-like Features (PLFs) and Mud Volcanoes on the Eastern Mackenzie Shelf
Over the last few days, we have conducted three remotely operated vehicle (ROV) dives and two autonomous underwater vehicle (AUV) surveys at areas of geologic interest known as pingo-like features (PLFs) and mud volcanoes on the eastern Mackenzie Shelf.
About 1,350 pingos are found on the adjacent land of the Tuktoyaktuk Peninsula. A pingo, which is an Inuit word, is a mound-shaped, ice-cored hill that forms on land when fresh water enters the near-surface sediments in summer and then freezes in winter. As the ice forms, physical expansion occurs and pushes up the sediment layers above it, creating the pingo.
Pingo-like features found on the seafloor are circular mounds that rise up like haystacks from the seafloor and superficially resemble pingos found on land. The underwater PLFs were first discovered in this area in 1969 and investigated as a potential hazard to navigation. Since then, thousands of PLFs have been identified along the continental shelf/slope, but only a handful have been studied in detail to understand how they form. One of the goals of this trip is to try to understand whether the marine PLFs and the terrestrial pingos are actually similar features and formed under similar processes.
Photo 1: Pingo-like features in bathymetry images.
In multibeam bathymetry images, underwater PLFs look like rows of circular mounds or, when they collapse, donuts. We chose four PLFs, 10 metres high and 70 metres across, to investigate with the MiniROV’s HD video camera. While surveying, we find abrupt transitions between the smooth and flat seafloor, which surrounds the PLFs, to 30–40 degree slopes of the PLF flanks. The flanks contain small boulders, cobble and gravel. As these materials are not seen on the surrounding seafloor, we speculate that they have been pushed up with the freshwater from deeper in the seabed.
We also encounter communities of suspension-feeding organisms, animals that feed on the small planktonic organisms that drift past them in the currents. We often find these animals — which include soft corals, basket stars and crinoids — on sloped terrain, like the flanks and summits of the PLFs, where current speeds are higher and more food flows past them. Other organisms include a variety of benthic fishes, worms, sponges, brittle stars and anemones.
Photo 2: Gersemia sp. coral, sponges and brittle stars on a pingo-like feature.
Mud volcanoes are also circular seafloor features, both conical and flat-topped, but unlike pingos do not contain ice cores. These larger, pancake-like features, greater than 1 km across and 10–30 m in height, are areas that have subtle changes in seafloor topography. Mud volcanoes form when methane gas, seawater and mud bubble up on the seafloor from approximately 1 km below the seafloor.
The first mud volcano we surveyed was at 420 m below the surface. We can see the form of the mud flows in the multibeam bathymetry, and we can detect what we believe are the various ages in both the sidescan sonar and with the ROV, which shows abrupt color changes from light grey to dark grey between very young and very old flows. We also see differences in the chemistry of the layers below the seafloor and, on the oldest of flows, dense populations of chemosynthetic siboglinid polychaete worms, which thrive in the chemical-rich sediments. Other organisms found at the 420m mud volcano include benthic fishes, shrimp and several species of anemones.
At the 740 m mud volcano we see evidence of mud flows in the bathymetry and, using repeat mapping techniques, we identify annual changes in the surface topography. During the ROV dive, we find a vent area where fluidized mud was actively moving, like the top of boiling water roiling the surface of the seafloor. Small gas bubbles were coming out of the fluidized mud almost continuously, and large bursts of gas carried sediment up into the water column. Surrounding the vent area were trails of what appear to be very fresh mud flows running down the gentle slope on the side of the mud volcano.
These observations provide a glimpse of how mud volcanos build up. Sea life was less abundant here but included a few scattered anemones, fishes, beautiful skates and the ever-present krill, which are incredibly abundant on nearly all of our ROV surveys.
Photo 3: Contact showing juxtaposition of young and old mud flows, with dense siboglinids on old flow in background on 420m mud volcano.
The seas have been calm and winds have been light. But Arctic sea ice was approaching the ship during the ROV survey, which meant that we had to abort the ROV dive very quickly and move to a new survey location. Our second survey site was also not accessible due to sea ice. We took advantage of this opportunity to enter the sea ice edge, if briefly, to see first-hand the incredible beauty of the drifting sea ice. It was truly amazing. Tomorrow we transit back to the west Mackenzie Shelf for our final two days of surveying.
Photo 4: Sea ice off the bow of the Araon.
What is a glacier? Understanding the glacial history of the western Arctic
To interpret what we see today both on land and at the seabed, we need to understand how the landscape was different in the past. When we say “past”, we mean on a geologic timeframe!
A key period we are interested in better understanding is a period about 10,000-20,000 years ago, when the climate was much colder and glaciers covered much of Canada. There have been several other geological periods in the last million years, when glaciers covered the landscape; indeed Antarctic and Greenland and parts of Baffin Island are still covered.
But we are most interested in this “recent” one, and in particular, we are hoping to collect some of the first data on the western side of the Mackenzie Trough to understand the imprint that that glaciation has had on the Yukon Shelf. Scientists have had to speculate on the extent and timing of glaciations because they’ve never been out there with such equipment.
Glaciers are huge ice sheets which can be up to 1-2 km thick. Moving “at a glacial pace” the glaciers flow shaping the landscape beneath them – carving out materials (sediment and rocks) in some areas, grinding and depositing mixes of these materials in others. The patterns of removal and deposition of these materials are the key pieces of evidence that we are looking for to reconstruct what happened thousands of years ago… a scientific time-machine!
Why is it important to understand the glacial history?
The glacial history has direct influence on the strength and properties of the seabed sediments. This has implication for foundation stability (for any seabed engineering), the occurrence of landslide events, the temperature of the seabed which influences permafrost and gas hydrate occurrence, seabed habitat, and a host of other spin-offs from our improved understanding of the natural system in the Beaufort Sea can contribute in some way to many local and even global issues.
Investigating the glacial history from the Araon
Once again, we are using all the tools on board the Araon to build up the picture of the seabed and below it and hopefully develop a better understanding of the geological history of the Beaufort Sea. Using the sonar instruments onboard, we can recognize the removal of the sediments as the glacier advanced by the broad and deep cuts in the soft rocks and sediments across the continental shelf. This process created the Mackenzie Trough, a long scar over 100 m deep and 10s of km wide gouged over 100 km out across the shelf. Then, as the glacier retreats, it leaves behind massive deposits of mud, sand and gravel mixes, sometimes entirely mixed-up in what is called a till deposit, and sometimes in well layered sediment beds, like a layer-cake.
Figure 1 - Some areas have a "layer-cake" cover of muds deposited in front of the glacier as it retreated to the coast. The black arrow points to the seabed. The white arrow shows over 40 metres thickness. Below this are mixed sediments, probably from beneath the glacier when it filled the Mackenzie Trough.
Each successive bed of sediment records the conditions of the environment of the time, and we attempt to tease out a history of environmental changes, where the beds represent the “pages” of a history book. We have observed more than 80 m of this mud (with some stones) in some places but 20 to 40 m is commonplace.
Figure 2 - A sediment core has been captured in the steel barrel below the 1500 kg lead weights and retrieved at the Araon’s stern.
While our sediment cores can only reach a few metres into the muds, not the 10s or 100s of metres that the glaciers carved and deposited, they still provide very important information. The cores allow us to physically examine the sediment and better identify the types of deposits. And with a bit of luck, we will find some “datable” material, such as small fossil shells or tiny “foraminifera”. The material can be sent to a lab for radiocarbon dating which tells us how old the shell is.
Figure 3 - Finding a fossil shell (red arrow) in the glacial muds is a bonus for age dating; otherwise we have to “dig” to collect 100s of tiny microfossils in this mud, a tedious task!
Our first impression is that we have collected some high quality data that will build upon existing knowledge. It will take plenty of work to put together a coherent picture of glaciations largely through interpreting the extent and behaviour of the glaciation from our new seismic records.
Arctic Wildlife Above and Below the Beaufort Sea
We completed science operations on September 12 after conducting a successful ROV dive and collecting several more gravity cores in the Western Mackenzie Trough and Yukon Shelf. Although this is a geosciences expedition, we have made several observations of marine life as well. Topside, we have seen numerous species of birds, including snow geese, ringed seals, and, excitingly, we had an opportunity to observe a polar bear on drifting Arctic sea ice.
Photo 1: A polar bear on drifting Arctic sea ice.
It was amazing to see first-hand the harsh environment in which this bear thrives and a testament to the fact that animals can evolve to fill remarkable ecological niches. Underwater, during our remotely operated vehicle (ROV dives), we observed dense populations of species of soft coral and many basket stars, crinoids, anemones, carnivorous sponges, skates and other fish.
Photo 2: A soft coral and basket star. Water depth is 147 m.
Photo 3: One of many species of anemones, about the size of a lemon. Water depth is 1,035 m.
Photo 4: A deep-sea skate. Water depth is 1,008 m.
On September 15, we passed by the rocky Diomede Islands in the Bering Strait. These two islands — one belonging to Russia and the other to the United States — are separated by only three kilometres of water. The Diomede Islands had to have drawn the attention of early humans as they entered North America across the Bering land bridge from Eurasia during prehistoric times when the sea level was much lower. It’s interesting to ponder early human explorations as we complete ours.
Photo 5: Group photo of science team and Araon crew near Diomede Islands.
We disembark in Nome, Alaska, on September 16, and then the science teams will return to their respective home institutes and begin the work of processing the incredible volume of data that has been collected. We have had a wonderful journey and greatly appreciate the hospitality of the Korea Polar Research Institute and the crew of the RV Araon.
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