Monterey Bay Aquarium Research Institute
Arctic Shelf Edge and Slope:
ROV Observations

MBARI’s Arctic ROV operations on shelf and slope of the Beaufort Sea

MBARI has participated in three research cruises in the Canadian Beaufort Sea on the Canadian Coast Guard Icebreaker Sir Wilfrid Laurier (SWL). On each of these cruises an inspection class remotely operated vehicle (ROV) has been utilized to visualize the seafloor and to collect samples. This work has been conducted in collaboration with scientists at the Geological Survey of Canada and Fisheries and Oceans Canada. This is also part of a collaborative research network involving participation by the Korean Polar Research Institute.

 

An overview of the ROV operations that MBARI has conducted from the SWL in 2010, 2012, and 2013 are outlined on this site.

 

In total, 37 dives have been conducted; 8 with a Phantom ROV in 2010 and 29 dives with MBARI’s MiniROV in 2012 and 2013. The locations of these dives are indicated in Figure ## and listed in Table ##. Videos clips showing the characteristics features are posted here.


Beaufort Shelf Location
                    Map 
 

Site map:

Expanding capabilities for ROV operations in the Arctic- Filling the open niche

Evidence of methane venting on the Beaufort shelf and shelf edge

Beaufort Sea shelf edge morphologies

            (a) Areas of rough topography

            (b) Gravel deposits along the shelf edge.

Appearance of continental slope sediments

(A) Sediment covered areas

(B) Outcrops exposed on the slope

(C) Water Seepage on the Slope

Mud Volcanoes

Whale Marks

Video Annotation

Published Literature

 

 

Expanding capabilities for ROV operations in the Arctic- Filling the open niche:

 

ROV’s are among the most effective tools for conducting detailed surveys of the seafloor characteristics. However, there has been little use of ROV’s in the Arctic Ocean in water depths below ~150 m water depths. As a result the appearance of the seafloor along the margins of the Arctic Ocean is largely unknown.

 

The lack of ROV exploration in the Arctic is largely attributable to logistical difficulties. The existence of sea ice over the outer shelf and slope has historically made access and especially ROV operations difficult and it is still not possible to operate in some areas in a given year. In addition most deep diving ROV’s require large launch and recovery systems that take up a considerable amount of deck space and need to be installed in port. They also require a large team of dedicated people to operate. In practice this means that a ship going into the Arctic would have to be largely if not solely committed to ROV operations for an entire summer field season, which is economically hard to justify.

 

During the 2010 SWL cruise the ROV sampling targets were gas vents near the edge of the continental shelf in <150 m water depth. For this work a Phantom ROV was used, which is a small commercially produced vehicle. Phantoms have been heavily used since 1982, sometimes for work on the Arctic shelf and MBARI had one. They are small enough to be stowed in the ships hold and only mounted on the deck during a particular segment of an expedition. Thus, it makes it viable to utilize as an ancillary operation in conjunction with other programs.


Phantom ROV Phantom ROV deployment

 

After the 2010 field season, the scientific goals shifted from operations near the shelf edge to research targets in up to 1 km of water depth, which is beyond to capability of the Phantom. The lack of a capable, easily deployed, and inexpensive to operate vehicle was identified as a hole in the capabilities of the existing research facilities, which was hindering the advancement of high latitude science. Some commercially available were considered, we did not find them optimal for our needs. A decision was made to build a fly-away inspection class ROV system at MBARI. The goal was to obtain a capable vehicle which could access ≥1 km water which could be used as ancillary programs on expeditions. Initially it was to be used to continue the Arctic project, as well as to provide the opportunity to conduct operations elsewhere in the world from ships of opportunity.

 

Dale Graves and Alana Sherman at MBARI designed a vehicle to fill this open niche.  They then lead a team in build an initially 1000 m capable. It is now called the MiniROV. The field programs in 2012 and 2013 were the first uses of this vehicle.



 

The MINI ROV is a portable, low cost, inspection class ROV system, capable of operating with a small crew (2 people). The MINI ROV is capable of light duty work functions such as limited sampling, video transects, instrument deployment and recovery (with a 70 pound instrument payload) and is the core vehicle is outfitted with the following suite instruments: HD camera, scanning sonar, lasers, LED lights (10,000 lumens) and CTD. A five-function manipulator arm (ECA Robotics Arm 5E) was added in 2013 field program enable sampling (rock samples, push cores, etc.) and potentially experimental deployments to be conducted. In addition, the vehicle will has bolt on tool sleds for mission specific payload and sampling requirements.

 

Efforts to enhance the capability of the MiniROV are on-going. For example, since the 2013 field program, a new longer umbilical, allowing the vehicle to dive to 1500 m was acquired. A generator was selected and purchased, enabling the vehicle system to be operated on ships of opportunity without having to interface to the ship’s power. A mid-water sampler was added to the vehicle tool sled.

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Evidence of methane venting on the Beaufort shelf and shelf edge

The seafloor under the Arctic Shelf is arguably the part of the Earth that is undergoing the most dramatic change due to global warming (e.g., Paull et al., 2007). In the southern Beaufort Sea, off the north coast of Canada, the shelf area was terrestrially exposed during much of the Quaternary period when sea level was ~120m lower than present. As a consequence, many areas are underlain by >600m of ice-bonded permafrost that conditions the geothermal regime such that the base of the methane hydrate stability can be >1000m deep. Marine transgression has imposed a change in mean annual surface temperature from -15°C or lower during periods of terrestrial exposure, to mean annual sea bottom temperatures near 0°C. The thermal disturbance caused by transgression is still influencing the upper one kilometer of subsurface sediments. Decomposition of gas hydrate is inferred to be occurring at the base and the top of the gas hydrate stability zone. As gas hydrate and permafrost intervals degrade, gaseous gas will form and may generate excess pore water pressure. The fate of this gas and in particular whether it is escaping from the seafloor is at issue.

 

In the fall of 2010 the goal of the ROV operations was to investigate sites where methane venting possibly associated with decomposing gas hydrate and/or permafrost was inferred to occur. Water column acoustic anomalies identified as potential vents sites has been discovered the previous summer along the shelf edge during multibeam surveys conducted by the ArcticNet project (Blasco et al., 2013; Saint-Ange et al., 2015). During this expedition a Phantom ROV was used to document the nature of these seafloor gas vents. Two different styles of methane venting was observed on this expedition (Paull et al., 2011).

 They are illustrated in video clips A and B below.


  Location of 2010 Dive 8 Video 

Vigorous Methane Vent (Dive 8: 2010) (Download movie file .wmv .mov)

Video shows methane venting at a site in the middle of the Arctic shelf. In this image, bubble releases are migrating along the seafloor, apparently following the tip of a propagating crack in the seafloor. A cloud of sediment is created by the vigorous gas venting. Such vigorous venting is commonly observed at discrete geomorphic features known as Pingo-Like-Features (Paull et al., 2007).


  Location of 2010 Dive 3 video 

Methane Vent (Dive 3: 2010)
Video shows methane bubbles intermittently emanating from several small holes that are rimmed with white bacterial mats. This style of venting of methane is occurring over a large area along the edge of the continental shelf.

 

The methane gas emanating from both areas have stable isotopic compositions that indicate they are microbial in origin, are radiocarbon dead and thus sourced from geologic deposits. The methane vents at the Pingo-Like-Features are believed to be sourced from the top of the gas hydrate stability field, while the gas emanating along the shelf edge can be from either permafrost or gas hydrate decomposition. Gas venting from both these shelf edge environments is consistent with heating associated with the last transgression.

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Beaufort Sea shelf edge morphologies:

ROV dives along the shelf edge of the Beaufort Sea were conducted in during the SWL cruises in 2010, 2012, and 2013. These provide insight into the processes that are occurring in this region. Two re-occurring morphologies were observed during the ROV dive; areas of slightly elevated topography and exposed gravel deposits.

 

(a) Areas of rough topography

ROV-observations of the seafloor near the shelf edge in the areas where gas venting was observed in 2010 (Phantom Dives 1 to 7) is associated with patches of distinctive rough morphology. These patches form isolated small mounds and ridges which are commonly associated with a white surface coating that are interpreted to be bacterial mats. The positive relief on these features may be related to differential erosion, leaving these more resistant patches standing higher. The concept that the fine-scale topography is related to permafrost is being evaluated.

 


  Location of 2010 Dive 5 video 

Mounds (Dive 5: 2010) (Download movie file .wmv .mov)

Video showing an individual patch of rough topography near the shelf edge. Video clip starts as ROV is over smooth seafloor with numerous brittle stars and shows transition as it moves onto a patch of rough topography. Rough topography is composed of areas frosted with white and in places exposing black colored seafloor. These colored areas occur on subtle ridges that are slightly elevated with respect to the tan sediments within the patch and distinctly higher than the surrounding brittle star covered smooth seafloor. Field of view is estimated to be ~2 m. The images suggest that more erosion resistant materials occupied the cracks.


  Location of 2010 Dive 3 video 

Polygonal Structure (Dive 3: 2010) (Download movie file .wmv .mov)

Video shows a patch of slightly elevated rough topography near the shelf edge.  Within this patch there are ~20 cm wide <5 cm high white and black ridges that appear to outline approximately polygonal patterns. Gas bubbles occasionally emanate from the white and black areas. Field of view is estimated to be ~2 m.

 

   Location of 2010 Dive 3 video 

Older Inactive Ridge (Dive 3: 2010) (Download movie file .wmv .mov)

Ridge of slightly elevated and rough topography seen near the shelf edge. The ridge is estimated to be ~1m across and have 10 to 20 cm of relief with respect to the surrounding smooth seafloor. The size and shape of this ridge is similar to the rough topography seen nearby but lacking the white and black coloration and thus inferred to be inactive. Field of view is estimated to be ~2 m.


 (b) Gravel deposits along the shelf edge

 

ROV dives discovered that gravel deposits occur near the shelf edge at a number of sites (2013 MiniROV Dives, 14, 17, 18, 19, 20, 25, 26, & 28 and 2012 MiniROV Dives 7, 9). These deposits are considered to be tills as they are composed of unsorted material containing boulders, cobbles, and pebbles of mixed lithologies, as well as fine sediment. The origin of these tills is the topic of on-going investigations.


  Location of 2013 Dive 18 video 

Shelf Edge Gravel (Dive 18: 2013) (Download movie file .wmv .mov)

Video showing extensive gravel exposed on the seafloor near the shelf edge. Red dots are 8 cm apart.



  Location of 2013 Dive 25 video 

Shelf Edge Gravel (Dive 25: 2013) (Download movie file .wmv .mov)

Video showing extensive gravel exposed on the seafloor near the shelf edge. Note that sessile organisms are frequently attached to cobbles. Red dots are 8 cm apart.

 

Appearance of continental slope sediments

 

(A) Sediment covered areas

An ROV dive transect (MiniROV Dive 15) was conducted on the slope within a huge landslide scars, the seafloor that was seen is covered with sediment, which has apparently accumulated in place. Not a single rock was observed which is in sharp contrast to areas at the shelf edge and on faces exposed by slide scars where pebbles, cobbles and even boulders are common.


  Location of 2013 Dive 15 video 

Background Seafloor (Dive 15: 2013) (Download movie file .wmv .mov)

Clip shows part of an 867 m long transect between 667 and 592 m water depth up the slope of a sediment-draped landslide scar. Bottom has scattered sea pens (distinguished from tubeworms as they do not form clusters). The bottom was monotonously similar along the entire transect. Red dots are 8 cm apart.

 

(B) Outcrops exposed on the slope

Three ROV dives were conducted within slide scars or on the sides of gullies where older materials have been exposed. These deposits are also considered to be tills as they are composed of unsorted material containing boulders, cobbles, and pebbles of mixed lithologies, as well as fine sediment. These show that tills occur on the slope down to nearly 1 km water depth as well as on shelf edge of the Canadian Beaufort Sea.


  Location 2013 Dive 21 video 

Scattered Cobbles (Dive 21: 2013) (Download movie file .wmv .mov)

Video clip shows scattered cobbles on the face of scarp within a side scar in ~950 m and the ROV’s mechanical arm collecting a cobble. Some of these cobbles were plucked out of the formation. On each dive where cobbles occurred 8-14 samples were collected. Red dots are 8 cm apart.


Location of Dive 29 video

Boulders and Cobbles (Dive 29: 2013) (Download movie file .wmv .mov)

Video clip from ~990 m water depths where the ROV conducted a transect up the steep sidewall of a slope cutting gulley. An outcrop sequence that is ~100 thick was observed which is composed of an extremely poorly sorted sequence containing boulders and numerous cobbles. Red dots are 8 cm apart.


(C) Water Seepage on the Slope

The ROV encountered six positive relief features within a slide scar in ~960 m water depths during (Dives 21 and 22) which were covered with a distinctive orange stain or precipitate.  These features occur on a steep slope where older strata might be exposed on the sole of the slide. They are ~1m high, 2-5 m wide, and may occur in a row.  They are believed to be associated with water venting onto the seafloor.


  Location of
                    2013 Dive 21 video 

Shimmering Water (Dive 21&22: 2013) (Download movie file .wmv .mov)

Video shows shimmering water, which indicates water with a different salinity is flowing onto the seafloor at one mound. A brilliant orange color is seen on freshly exposed faces, where the ROV has broken off samples. Red dots are 8 cm apart.


 

Mud Volcanoes

Multibeam bathymetric surveys conducted by the ArcticNet project in 2009 provided the first detailed bathymetry for a 100 km long section of the shelf edge and slope of the Canadian Beaufort Sea (Saint-Ange et al., 2014; Fig. 1). These data revealed the existence of large circular morphologic features in water depths of ~282 m, ~420 m, and a cluster of three closely-spaced structures in ~740 m water depths (Figs. 1 and 2). Water column acoustic anomalies were identified over each of these features, indicating that they are sites of active gas venting and thus initially interpreted as being large mud volcanoes (Blasco et al., 2013; Saint-Ange et al., 2014). Six ROV dives focused on exploring and sampling gas from the tops and flanks of these expulsion features.


  Location of 2012 Dive 8 video 

Gas Collection (Dive 8: 2012) (Download movie file .wmv .mov)

Video clip first showing gas bubbles escaping form the top of the ~430 m mud volcano and being captured into a transparent overturned funnel mounded on the front of the ROV. When a sufficient amount of gas was collected the ROV ascended to 400 m water depth and a heater within the funnel was turned on. The gas hydrate coated bubble mass decomposed over a couple of minutes, forming a gaseous headspace. Later this gas was collected by withdrawing it into a pre-evacuated cylinder. 


Location of 2012 Dive 5 video

Tubeworm Beds (Dive 5: 2012) (Download movie file .wmv .mov)

Video clip showing characteristic seafloor textures topography on the top of a generally flat-topped mud volcano in ~283 m water depths on the slope of the Beaufort Sea.  Clip begins with a close up of a starfish and surrounding tubeworm tubes, than zoom out as the ROV transected over extensive tubeworm beds and landed to zoom on the worms and seafloor again. Red dots are parallel lazar beams, with form an 8 cm scale bar.


  Location of 2012 Dive 5 video 

Mound and Groove (Dive 5: 2012) (Download movie file .wmv .mov)

Video clip showing characteristic seafloor textures topography on the top of a generally flat-topped mud volcano in ~283 m water depths on the slope of the Beaufort Sea. Tubeworms are abundant and form parallel swaths with varying worm density. Clip begins with individual elevated mound with small crack on its top which reveals black sediment and rimmed by frosting of white (mat?). This pattern is interrupted by a distinct grove or crack which is ~5 cm across and has raised levee-like flanks. As the ROV followed this groove, it changed shape into series of mounds. Clip ends showing a similarly oriented parallel lineation exists nearby.) Red dots are parallel lazar beams, which form an 8 cm scale bar.


  Location of 2012 Dive 6
 

Dense Tubeworm Beds (Dive 6: 2012) (Download movie file .wmv .mov)

Video transect across part of large flat-topped mud volcano in ~740 m water depth. This transect starts in area of isolated clusters of tube worms and moves into an area where the bottom is carpeted with tubeworms. Red dots are 8 cm apart.


Location of 2012 Dive 6 video

Top of 740 m Mound (Dive 6: 2012) (Download movie file .wmv .mov)

Video showing area near top of conical mud volcano in ~740 m water depths. This area is notably devoid of sessile organisms. One linear feature is crossed which is believed to be made by whales. Red dots are 8 cm apart.


  Location of
                    2013 Dive 24 video 

Top of 430 m Mound (Dive 24: 2013) (Download movie file .wmv .mov) Dive_24_S004_T001 another contact.mov

Video clip showing part of a dive transect across the top of mud volcano in 430 m water depths. Clip starts showing area where the seafloor is characterized by its light gray color, rough texture and notable absence of sessile organisms, which is believed to be a recent mud flow. As the ROV moves toward the edge of the flow, the number of mobile organisms increases. The contact between the recent flow and the older surface is marked by a change to a tan color, a slight drop in the surface elevation, a change to a smoother surface texture, and the occurrence of sessile organism (notable tiny tube worms and white mats rimming burrows). A linear ridge seen on the older surface outside the flow appears to end where it was buried by the flow. Red dots are 8 cm apart.


Location of 2013
                  Dive 24 video

Top of 430 m Mound (Dive 24: 2013) (Download movie file .wmv .mov) Dive_24_S004_T001 young white flow contact.mov

Video clip showing part of a dive transect across the top of mud volcano in 430 m water depths. This clip shows the edge of what is interpreted to be a recent mud flow, starting before the flow is seen. Initially the surface is light tan and has some sessile organism (small tubeworms and white rimmed burrows). The edge of the flow is associated with a change to a lighter gray color, slight rise in surface elevation, and rougher surface texture. The surface of the flow is notably lacking in sessile organisms. Red dots are 8 cm apart.



 

Whale Marks

Large tear-shaped grooves were seen on most of the ROV dives on the Beaufort Shelf and slope that are typically 2-10 m long and have slightly curving paths. In cross section these grooves are characterized by smooth rounded central troughs, which are consistently associated with upturned sediments on their flanks. These features commonly somewhat tear shaped in that they are tapered at one end and get deeper toward the other side before ending with a blunt end. It is common to have clumps of obviously out of place sediments dropped onto the seafloor at the end of these grooves. These structures are tentatively attributed to whales.

Location of 2012 Dive 5 video

Whale Mark (Dive 5: 2012) (Download movie file .wmv .mov)

Video showing an example of a showing large tear-shaped grooves. This groove has  clumps of sediment at the end that are have lighter colored sides suggesting this feature is comparatively fresh. Red dots are 8 cm apart.

 

Video Annotation

The video recorded from the ROV dives in 2010, 2012, and 2013 are archived at MBARI. The video has been reviewed to document the major components of the visually identifiable benthic fauna using VARS (video annotation and reference system; http://www.mbari.org/vars/vars_overview.html). Lists of the identified organism is tabulated in xxx.table.xls

This research has been advanced in collaboration with scientists from the Geological Survey of Canada, Fisheries and Oceans Canada and MBARI. Future research cruises will include an expanded research network with participation by the Korean Polar Research Institute.

Published Literature

Blasco, S., Bennett, R., Brent, T., Burton, M., Campbell, P., Carr, E., Covill, R., Dallimore, S., Davies, E., Hughes-Clarke, J., Issler, D., MacKillop, K., Mazzotti, S., Patton, E., Shearer, J., and White, M., 2013, State of knowledge: Beaufort Sea seabed geohazards associated with offshore hydrocarbon development Geological Survey of Canada Open File 6989, 307 p.

Paull, C.K., Ussler, W. III, Dallimore, S., Blasco, S., Lorenson, T., Melling, H., McLaughlin, F., and Nixon, F.M., 2007, Origin of pingo-like features on the Beaufort Sea shelf and their possible relationship to decomposing methane gas hydrates, Geophysical Research Letters, 34, L01603, doi:10.1029/2006GL027977.

Paull, C.K., Dallimore, S., Hughes-Clarke, J., Blasco, S. Lundsten, E., Ussler, W. III, Graves, D., Sherman, A., Conway, K., Melling, H., Vagle, S., and Collett, T., 2011, Tracking the decomposition of permafrost and gas hydrate under the shelf and slope of the Beaufort Sea, 7th International Conference on Gas Hydrate, 12 p.

Saint-Ange, F., Kuus, P., Blasco, S., Piper, D.J.W., Hughes-Clarke, J., and MacKillop, K., 2014, Multiple failure styles related to shallow gas and fluid venting, upper slope Canadian Beaufort Sea, northern Canada, Marine Geology, v. 355, p. 136-149.

 

Last updated: Mar. 05, 2015