Measuring the “death” of light at the end of World

Light is a ubiquitous physical phenomenon that we experience everyday on this planet. Undoubtedly, vast majority of the light we receive is from the Sun. For centuries, natural scientists and physicists were fascinated by the “birth” of light as well as its path to Earth; but it was not until recent decades, when the scientific community began to systematically study the “death” of light and recognize its significance. Light does not simply “die,” its energy is usually redirected or conserved in another form. The redirection of light in the atmosphere gives the sky its blue color, while the absorption of red light by the ocean allows blue light to penetrate relatively deeper in the water column.

Light in a marine environment is usually diminished in two ways: absorption and scattering. This concept can be easily demonstrated with an old-fashioned projector that uses transparencies to project images. Now imagine that I placed two clear glass dishes containing mystery liquids on the projector. As an audience, you would see the projected image were two shadows of the dishes’ shape; these shadows indicate that the two mystery liquids completely and equally diminish light from the projector. However, if I were to invite you to look directly at the two dishes, you would see one is filled with milk, and the other is filled with fountain-pen ink. Even though these two kinds of liquids give light the same fate, the kind of particles in each liquid is evidently very different. Milk scatters more light than it absorbs which is why it appears white; while ink absorbs more light than it scatters, so it appears to have a dark color. While this simple demonstration presents the unique optical properties of two kinds of homogeneous solutions, optical phenomena in the ocean are far more complex.

Absorption and scattering in the ocean depend heavily on water and the small particles residing in it. These two processes are collectively termed as “inherent optical properties” (IOPs) – which indicates that the ability for water and small particles to interact with light is “inherent” and is not dictated by ambient light. This is why many IOP instruments have their own light source and can be deployed in the dark. Light is typically absorbed by the following five components in the ocean: water, phytoplankton, non-algal particles (NAP), and colored dissolved organic matter (CDOM). Phytoplankton are unicellular plant organisms living in the ocean. They function in a marine ecosystem like their terrestrial counterparts on land. Their unique pigments for conducting photosynthesis have a significant absorption of light; the effect is more noticeable during a period of intense phytoplankton growth (aka. “bloom”). Non-algal particles are materials that are not alive and are not dissolved. NAPs often include cell walls of phytoplankton, detritus waste from organisms, as well as suspended minerals and sediments. Isolated NAPs often appear translucent or even transparent; however they can aggregate and become large particles after the end of a bloom when a massive amount of waste materials is readily available; therefore they can be significant sources for light absorption. Colored dissolved organic matter (CDOM) is the most mysterious among the four components that absorb light in the ocean. CDOM is in a dissolved phase, and so it is very hard to be captured with conventional filtration methods and without contamination. No one has a comprehensive understanding of CDOM even in the present day and, for decades, optical oceanographers simply referred to it as “gelbstoff” or “yellow matter.” This is because measuring this material is extremely difficult, and in addition the main components of CDOM differ significantly by region. The effect of CDOM is mostly pronounced in cases of “dead” lakes or ponds after a toxic algal bloom; in these scenarios, the aquatic environment is largely lifeless and the water has a hint of dark hue, which indicates light absorption. Light in the ocean is not only diminished by absorption; it can also be redirected by scattering. Size, concentration, and the intrinsic “texture” of particles can significantly contribute and influence scattering. These IOPs are elemental components that dictate the amount and intensity of light leaving the ocean-air interface. The outgoing light signal is usually computed as a ratio among the IOPs, and these ratios are commonly referred to as “apparent optical properties” (AOPs). AOPs are relatively easier to measure in comparison to IOPs; it gives rise to optical signals that can be detected by remote radiometers (a fancy light meter in the sky).

At this point, if it was a conversation, most people would begin to ask: ‘why is this important?’ And ‘why should we measure optics in Antarctica?” The answers to these questions would require an explanation of two orders – the first order concerns with biology and ecology, while the second order is operational and procedural. First, though only accounting for < 1% of the plant/algal biomass on Earth, phytoplankton produce approximately 50%—70% of the oxygen content. In order to grow and produce oxygen, phytoplankton needs light and carbon dioxide for photosynthesis. A careful examination of this bio-optical process can reveal how photosynthesis functions in the marine environment. Because phytoplankton uptake carbon when they conduct photosynthesis, they can also act as a biological pump and sink atmospheric carbon to great depths. The Southern Ocean, surrounding the continent of Antarctica, is the largest carbon sink in the world’s ocean both during the last ice age and in present-day. The western Antarctica Peninsula (wAP), where FjordEco field campaign took place, is one the most productive region among the Southern Ocean. The dark winters in the polar region makes light availability one of the limiting factors controlling phytoplankton growth. In addition, phytoplankton is a primary producer and it is the first link in the marine food web that plays a key role in oceanic ecology and ecosystem.

Furthermore, optical measurements are often very dynamic, and they would usually yield more information than what the researchers are seeking. This would allow a great opportunity to develop new proxies for studying specific oceanographic regions. For an example, using absorption data at 676nm of a scanned spectrum, we could derive chlorophyll concentration and refer pigment-based biomass; another example would be the relatively robust relationship between particle backscattering and particulate organic concentration in the water column. While the interpretation of many optical measurements is difficult and still has room for improvement, it undoubtedly provides valuable information for a holistic investigation of natural phenomena and ecosystems.

Moreover, the National Aeronautics and Space Administration (NASA) has been launching a suite of Earth observing satellites in the last two decades. Many of these missions are aimed to understanding oceanic processes. Passive sensors, such as the Moderate-Resolution Imaging Spectroradiometer (MODIS) onboard of the Aqua satellite, are capable of detecting ocean color signals (which are computed from water-leaving AOPs); since these AOPs rely heavily on IOPs and ambient light condition, they can be utilized to measure surface chlorophyll concentrations. This realization is perhaps one of the greatest technological advancements in the history of ocean science. For centuries, prior to remote measurements of ocean color, marine scientists only covered less than 10 percent of the entire world’s surface ocean. Since the launch of the first ocean color sensor, the Coastal Zone Color Scanner (CZCS), surface chlorophyll concentration data coverage around the globe has been extended to twice per day. This kind of data acquisition covering a large spatiotemporal scale was unprecedented, and it was only achieved through the understanding of fundamental optical components. However, it has been known that these satellite sensors are not well calibrated in the high latitudes; this is due to both the challenges of fieldwork and light availability/angles in these extreme environments. A great effort in ocean color algorithm validation and correction is urgently needed in the polar regions. NASA proposed to launch a next generation of ocean color sensor by 2020. The sensor is called “Pre-Aerosol, Clouds, and Ecosystem” (PACE) and it is “hyperspectral” – this means the detected signals will only have 5 to 10 nm intervals, and allow the data to have a finer spectral structure and shape. These information are crucial to understanding ocean biology and ecosystems.

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A Day Ashore in Antarctica

Our team of FjordEco scientists got the chance to leave the ship today and actually set foot on solid ground again. We needed to service a weather station and time-lapse glacier camera atop Useful Island, a small island at the mouth of the fjord. This location provides an excellent vantage point from which to observe the movement of icebergs around the fjord. This glacier camera was set to a 15-minute interval and so provided a detailed look at the icebergs in the fjord. Once the data were downloaded (over 10,000 images!), FjordEco scientists turned the images into a movie which showed interesting patterns of iceberg groundings, movements, and melting.

While one team was at the top of Useful Island servicing the weather station and camera, another team of ecologists was motoring around the island in a zodiac hunting for subtidal macroalgae samples for stable isotope analyses. Equipped in dry suits with attached rubber boots, the ecologists waded through the water sampling a variety of green and red fleshy algae. In addition, they took some samples of green ice which contained ice algae. When this ice melts into the seawater, algae are then deposited in the ocean and could be a source of food to the fauna living on the seafloor. Stable isotope analyses will allow scientists to understand how energy flows through the fjord ecosystem from the primary producers in the surface water to the top predators inhabiting the benthos, or seafloor.

The weather was thankfully calm and allowed for easy sample collection as well as a chance to observe some of the beautiful Antarctic fauna living on the island. Our team got the chance to see penguins, fur seals, a variety of impressive seabirds, and even a leopard seal during this day trip. It was a humbling experience being at sea level and for the first time getting an appreciation for the sheer size of the icebergs and the intricacies of their shapes. As the sun began to set, the sea ice began to sneak in silently but surprisingly fast. Our teams returned to the zodiacs and motored back to the ship. Even though the sun was setting, shipboard science never ceases. As soon as the teams boarded the ship and the zodiacs were recovered, we began to steam to our next sampling site for a full night of coring.

Written by Astrid Leitner.

 

A Day in the Life of a FjordEco Scientist

It’s been a crazy busy last two days; I’ve slept about 2-3 hrs each night. We’re getting into our stride for operations and everyone is working their tails off. The folks from the benthic group are dredging up mud from the sea floor through a variety of devices like the Mega-core, Box corer and Kasten corer. The phytoplankton folks are conducting measurements on phytoplankton concentrations, seawater chemistry, sunlight availability, particle concentrations and phytoplankton growth experiments with radionuclide labeled carbon isotopes. Our group has been conducting CTDs, recovering moorings, measuring turbulence in the water column and for the first time today, we attempted visits to the timelapse cameras to download the last 4 months of photos, (1 every hour to look at the glacier as it discharges icebergs.)

On one of the trips to service a timelapse camera deep within Andvord Bay, the ice conditions and weather made it too dangerous to make a beach landing so the trip was aborted. After we made it back to the ship, an amazing front was slowly making its way into the fjord but the winds were still calm so the photographer on board (Maria Stenzel) decided it would be a dramatic overflight around the ship with her drone. The footage is absolutely breathtaking; icebergs, brash ice, a mixture of blue skies, and approaching black clouds all with the backdrop of 1,000′ cliffs, icefalls and tidewater glaciers (http:www.instagram.com/FjordPhyto/). The rugged nature of this place is unbelievable, it kind of blows you away no matter what direction you look… Since the front has moved in, it’s been snowing like crazy, I would guess that at least 6 inches have fallen in the last 6 hours.

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Physical Oceanographer Peter Winsor and a team from the University of Alaska at Fairbanks try to reach an ice choked shoreline of Andvord Bay, but are forced to return to the ship for fear of being trapped in the ice. The team has left a long term time lapse camera overlooking a glacier which feeds into Andvord Bay at Inner Basin B (check). The camera was installed in December, 2015. Photo by Maria Stenzel

Late in the day today, we thought that we would recover one of our inner fjord moorings. The ice was too thick at the mooring location for a safe recovery so we resorted to Plan B: a trip to service a different time-lapse camera. We were given a last minute green light from the bridge to do this operation and scrambled to put our gear together and splash zodiacs over the side. We left the Nathaniel B. Palmer at 6:02 pm with good late afternoon light. We used the zodiac to push a lot of brash ice out of the way on the trip to the beach and like a SEAL team we hit the ground running. We had to scamper up a rocky talus slope that was covered in fresh snow. At the top of the scree, there was a cliff with a path below it that led about 100 yards to the camera tripod setup. It was an invigorating traverse that led to a beautiful perch with clear views to one of the tidewater glaciers that we estimate is discharging ice into the fjord at a rate of 5 m/day. Once at the camera Doug pulled out its SD card and a tablet to back up nearly 4,000 photos. We wiped all the snow off of the camera, inserted a new SD card and scrambled back down to our zodiac waiting for us at the beach landing. Our big red ship was staged just a mile off and now as darkness was descending and the snow was falling, we followed the ship’s yellow spotlights back. Unbelievably, we were back on the boat in 40 minutes, right at dark. Hooray for another amazing day of science on the Western Antarctic Peninsula!

Tonight the benthic folks will drag nets on the seafloor and repeat their coring. We are set to get up early and tow the ACROBAT from the outer to inner fjord, it will be our first ACROBAT tow so far on this trip.

Written by Hank Statsewich.

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Physical Oceanographer Peter Winsor and a team from the University of Alaska at Fairbanks try to reach an ice choked shoreline of Andvord Bay, but are forced to return to the ship for fear of being trapped in the ice. The team has left a long term time lapse camera overlooking a glacier which feeds into Andvord Bay at Inner Basin B (check). The camera was installed in December, 2015. Photo by Maria Stenzel

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Physical Oceanographer Peter Winsor and a team from the University of Alaska at Fairbanks try to reach an ice choked shoreline of Andvord Bay, but are forced to return to the ship for fear of being trapped in the ice. The team has left a long term time lapse camera overlooking a glacier which feeds into Andvord Bay at Inner Basin B (check). The camera was installed in December, 2015. Photo by Maria Stenzel

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Physical Oceanographer Peter Winsor and a team from the University of Alaska at Fairbanks try to reach an ice choked shoreline of Andvord Bay, but are forced to return to the ship for fear of being trapped in the ice. The team has left a long term time lapse camera overlooking a glacier which feeds into Andvord Bay at Inner Basin B (check). The camera was installed in December, 2015. Photo by Maria Stenzel

 

 

Mud and Moorings

It has been a very busy start to our second FjordEco cruise with lots of coring and mooring operations at Station B (our outer shelf station) and in Andvord Bay. The sediment trap mooring at Station B was recovered smoothly and presented 20 bottles of preserved material that has been sinking to the seafloor over the last 5 months. From this mooring we will be able to determine the flux of carbon (i.e. the amount of food) sinking to the animals on the seafloor. This is important as these animals get little additional food during the winter when sea ice is thick and phytoplankton do not have sunlight to grow. It will be interesting to see how this flux compares to that in the fjord from the second sediment trap.

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Photo by A. Ziegler.

On our way to Andvord Bay we retrieved two physical oceanography moorings that were deployed in the Gerlache Strait back in November. The deeper mooring extended from 200m below the surface to the bottom at roughly 330m while the shallow mooring captured the upper water column from 20m to approximately 150m. This mooring was designed to detach from its flotation if hit by large icebergs. When the mooring surfaced we found the float was missing and the pressure sensor data revealed that the mooring had been hit several times by ice and dragged before breaking loose. Luckily the design allowed for the return of the instruments which continued to collect data at deeper depths without floatation. The physical oceanography team has downloaded all of the instrument data and is now processing and interpreting it all. These two moorings will give a long-term picture of the water properties (temperature, salinity, oxygen) and water movement over the outermost sill of the fjord. This is an important location for determining water exchange in and out of the fjord.

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Photo by D. Brinkerhoff.

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Photo by D. Brinkerhoff.

The FjordEco team then moved into the inner basin of Andvord Bay to investigate ice conditions for our other operations. The ice was clear enough for the benthic team to begin coring. We conducted successful boxcore, megacore and Kasten core deployments. During these operations, the air temperature rose 6°C which brought continuous heavy rain and winds of over 70 knots. Even the experienced crew have rarely seen such conditions in this area. After core sampling, we moved to the middle basin of the fjord to retrieve the time-lapse camera mooring.

The time-lapse camera captured a still image of the seafloor every 6 hours from deployment on December 5, 2015 to recovery on April 6, 2016. The benthic team now has 488 images to compare and analyze. Stay tuned for more about the exciting footage captured by the camera as well as the first trawl of the cruise and deployment of the sea glider!

Written by Amanda Ziegler.

Here we go….again!

Only two short months ago we were all here in Punta Arenas, Chile, offloading from the Laurence M. Gould. Samples were shipped, equipment was stowed away, and scientists and crew went their separate ways. Now, our teams are assembling once again for the second cruise of the project. (Visit the rest of our webpage for a detailed look at our previous cruise and more information about the FjordEco project).

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Photo credit: K. Christiansen.

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Photo credit: K. Christiansen.

This second cruise will be aboard the Research Vessel and Ice Breaker (RVIB) Nathaniel B. Palmer. The 308 ft vessel holds 27 crew members and 43 scientists who will all call this vessel “home” for the next 32 days. This vessel not only supports vessel-based research but also supports zodiac operations for land-based projects, as well as helicopter operations for transport to field sites and aerial sampling techniques. Prepping and mobilizing our gear for the cruise fell on Easter this year, and there was certainly no shortage of holiday spirit or candy with the galley staff providing whole chocolate bars (a hot commodity on a month long cruise) and others donned playful bunny ears. Our cruise begins with a 4-day transit across the Drake Passage to the shelter of the western Antarctic Peninsula. We ensured a safe crossing by rubbing the toe of the famous Magellan statue in Punta Arenas. We will begin our work at Station B, a site on the outer continental shelf located near Palmer Station on Anvers Island. We will then move into the fjord to continue sampling for the remaining days (>20).

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Sampling locations during the second Fjord Eco cruise.

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Photo credit: K. Christiansen.

During this cruise, one goal for the science party is to recover moorings deployed in November-December 2015. The moorings must be recovered in order to retrieve data and prepare them for the next year as these will not be visited again for approximately one year. All moorings will ideally be turned around within the first week or so of the cruise if weather is cooperative, mainly ice conditions. Ice in this region makes mooring work a risky business. Sea ice can move in quickly endangering instruments while they are at the surface while massive icebergs can damage even deep moorings. We will be anxious to see if the shallow moorings survived the passages of large icebergs during these past few summer months. During the previous cruise, we were surprised to have found a mooring >5km from its original deployment location which had been dragged by an iceberg even with >600lbs ballast attached proving that ice can make it quite challenging to work in this environment. Once the moorings are recovered, the physical oceanography team led by Dr. Peter Winsor will work to download data from all of the instruments, charge batteries, ensure that everything is working properly, and redeploy them again. These physical oceanography moorings will provide data about the water circulation in the fjord and help to relate this to patterns observed in productivity and animal distribution. The benthic ecology team led by Dr. Craig Smith (chief scientist) will also be recovering two sediment trap moorings and a time-lapse camera mooring during this cruise. These moorings will help collect data relating benthic food supply (particles sinking to the seafloor) and animal responses over time in the fjord.

In addition to servicing moorings, the team will also be using zodiacs to access weather stations and time-lapse glacier cameras on shore. It is imperative that we service this equipment before the coming winter as power failures or other problems could limit the amount of data retrieved over the next very long deployment. The science party will also be conducting a wide range of chemical, physical, biological and geological sampling (see Project Summary for a more comprehensive look at the sampling). Stay tuned for MUCH more about all of the fun and interesting work we’ll be doing!

Written by Amanda Ziegler.

Antarctic fieldwork perspectives from an undergrad!

The Fjord Eco team recently made our way back to Punta Arenas, Chile through the Drake Passage, which we can again nickname the “Drake Lake” due to the great weather we experienced during the crossing. We enjoyed a fun-filled white elephant gift-exchange and delicious holiday meal for Christmas after departing from Palmer Station.

My name is McKenna Lewis and I am a second year undergraduate student at the University of Hawai’i. I am majoring in global environmental science and will be completing my senior thesis project within the parameters of the Fjord Eco project. My experience as a participant on this cruise has exceeded any hopes I could have as an undergrad from Hawai’i. This cruise was the first research cruise I’ve been on and I have experienced many other firsts on the cruise as well, including seeing snow for the very first time!

Living on a ship for six weeks didn’t leave me a horrible seasick mess as I had feared. Comfy staterooms, friendly ASC and ECO staff, good food, and an always stocked ice cream freezer made life aboard the Laurence M. Gould more than enjoyable. Not to mention the awe-inspiring views in Andvord Bay paired with calm, fjord-protected waters for which only one word comes to my mind to describe it: paradise. Daily sightings of humpback whales, Gentoo penguins, or leopard seals on ice floes never got boring. My favorite aspect about life at sea was getting to meet scientists, students, and marine technicians from all over the world, exchanging stories, good-hearted advice, and many, many laughs at the dinner table. I always had a blast with whomever I was working. There were even a few impromptu snow ball fights on deck!

The greatest challenge for me on this cruise was simply being inexperienced in oceanography. Although I prepared myself for the cruise as best as I could in my studies, there was still so much for me to learn. Fortunately, all who taught me and helped me in my learning process on the cruise were always patient and kind. I learned simple tasks, such as putting a plastic hardhat on a glass float, to more complicated tasks, like deploying a sediment trap mooring. After all our moorings were deployed, I learned the ins and outs of megacoring and Blake trawling and eventually got the hang of it! Processing the Blake trawls were my favorite operation because although they were time consuming and unbelievably muddy, being able hold and closely observe organisms from the benthos, which I’d only ever seen in BBC documentaries or preserved in bottles, was so exciting! A trawl we did in the inner basin of Andvord came up chock-full of ophiuroid sea stars and pycogonids, sea spiders, and another in the Gerlache Strait had a few dozen sea pigs. It was fascinating to see changes in species abundance and diversity from trawl to trawl within the fjord and out onto the open shelf. I feel that I learned the most during the processing of the trawls, with the others from our group gladly sharing what they knew about the various structures and functions of the different species found.

The process of field research was also something I was unfamiliar with. Quickly I learned that not everything goes as planned, as weather or equipment failure can be unpredictable. Problem solving and schedule adjustments must occur regularly. One evening we were surprised when the time-lapse camera mooring we had deployed fifteen minutes prior was spotted on the surface of the water. It turns out that one of the acoustic releases had flooded and released the weight at the bottom of the mooring. Luckily, we were able to recover the mooring, replace the release, and redeploy the mooring. Despite having three different groups on board all working on different aspects of the Fjord Eco project, we were able to remain organized and productive. We’ve had a successful cruise and I am grateful and proud to have been a part of this awesome research project!

Written by McKenna Lewis.

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In our muddy Mustang suits after processing a trawl. Photo credit: M. Lewis.

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A sunny day in the inner basin of Andvord Bay. Photo credit: M. Lewis.

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A jam session on the back deck during the transit to Palmer Station. Photo credit: M. Lewis.

Science Recap: More than halfway through our sampling!

Our sampling and deployments have been moving along rapidly! Suddenly we are over halfway through the science operations for our cruise. Here are some highlights from recent operations!

We’ve seen some amazing weather in Andvord Bay with clear blue sky, warm shining sun, and glassy calm water.

Of course most of the days have had temps hovering around or below freezing, snow or rain, and overcast skies proving to us that the weather of the West Antarctic Peninsula is highly variable. Sea ice and icebergs move quickly and conditions can change quite rapidly. We’ve seen katabatic winds suddenly intensify to over 70 knots (hurricane force)! This means that we must constantly be aware of ice conditions and change our sampling plan if there is too much ice to safely conduct an operation. The West Antarctic Peninsula is known for having variable weather as westerly winds bring warm, moist air from the Pacific Ocean to meet dry, cold air masses moving over the continent. This is also what causes major differences in climate between the West Antarctic Peninsula and other portions of the Antarctic continent, further emphasizing the interest in this region in the face of global climate change.

The ice cooperated with us long enough to deploy all of the physical oceanography moorings, weather stations and glacier cameras. The last camera was installed recently in the inner basin of Andvord Bay. The physical oceanography/glaciology team donned climbing gear and zipped away in the Zodiac to assemble this camera on a rocky outcrop facing the termini of a two massive glaciers at one head of Andvord Bay.

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The physical oceanography/glaciology team makes their way to the site of an automated weather station and glacier camera. Can you spot them?! Photo Credit: Eric Vetter.

This camera will take photographs of the glaciers to assess calving rates, snow cover and melting rates. These parameters will help constrain the ice flux into the fjord and the overall movements of the glaciers. This affects the amount of freshwater and sediment entering the fjord, which in turn influences the productivity (bringing the micronutrient iron) and animals on the seafloor. The ice hasn’t always been on our side, however. We discovered a shallow mooring that we deployed 2 weeks five kilometers down fjord – the entire mooring (including 1200 lbs of railroad wheels) had been dragged >5 km by an iceberg and released in shallower water!

The benthic ecology team assembled a time-lapse camera mooring which will be located in the middle basin of the fjord. This camera is designed to take images of the seafloor four times daily for the next four months; we will then recover the camera, swap batteries and redeploy it for the remainder of the project.

The images will reveal rates of animal activities (e.g. moving, feeding) and responses to seasonal food inputs such as sinking krill carcasses. The camera mooring was deployed smoothly and safely. 15 minutes later voices came over the radio saying there was a mooring mast that just rose to the surface nearby unexpectedly. The radio beacon identified it as the camera mooring which had just been deployed.

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The camera tripod mooring at the surface. Photo credit: Amanda Ziegler.

The team and ship’s crew quickly put a recovery plan together. The ship positioned alongside the mooring which was grappled and carried down to the stern to be lifted onto the ship. Once onboard it was clear that one of the acoustic releases had failed, but how it had failed was less clear. The weight which had been attached to the releases was obviously gone but the release which dropped the weight was still in the locked position. How could this be?! The team removed the release, opened it up and discovered that it had leaked. The pressure experienced by the release during its descent had forced water into the housing and shorted the electronics, causing it to release the weight without receiving the acoustic signal. Not what we expected! It was a great lesson in working with moorings and a reminder of the risk we take with our equipment to get the data we need. The team later mounted a new release and redeployed the mooring; it is now remains on the seafloor happily collecting data!

Written by Amanda Ziegler.