The far side of the sound (where Michael’s post described the trip out to) is very different underwater. Sandy, non-volcanic rocks and lots of different types of life.
There are still sponges but many different kinds of animals that we don’t really see near McMurdo station. Especially scallops which cover the seafloor.
While we get Crinoids on both sides of the sound, there were two at the site that we were working at. I only saw one, but it was a pretty one. These are closely related to star fish, sea urchins, and sea cucumbers and swim by waiving all their arms in a rhythmic pattern. We didn’t see any swimming though.
And in addition to the life on the seafloor, the algae growing on the underside of the ice, truly made the place special.
In order to SCUBA dive under the sea ice of Antarctica, one must first create an entrance into, and (more importantly) an exit from, the frozen Southern Ocean.
On October 20th, 2023, we drilled an ice hole at the Cinder Cones dive site, located ~45 minutes away from McMurdo towards the Erebus Volcano.
At 9 am the dive team met the drill operator, the carpenters, and the sea ice field safety team at the ice pier. The drill operator towed the Terex drill, dive hut, and drill bit out to the site using a bulldozer. The carpenters (who de-winterize the huts) drove a pisten bully and towed the fuel for the gas heater. The field safety team drove a Haglund and were responsible for navigating a safe route for us across the ice cracks. Finally, the divers joined the caravan in two pisten bullys.
As we made our way (slowly) toward the desired dive site, we had to stop often when we saw signs of cracks in the ice. Every crack must be profiled: drilled on either side using a Kovacs drill and the thickness of the ice and the width of the gap measured with a weighted measuring tape. We then do a quick calculation to determine which, if any, of our vehicles can cross safely. Over the decades, a few vehicles have fallen through the sea ice near McMurdo, including the tractor “Big John”!
Here is a video outlining all the activities from the day, including our caravan across the sea ice, profiling cracks, navigating a safe path to Cinder Cones, attaching the drill bit to the Terex drill, drilling our hole, and dragging our dive hut into place so that we have a nice warm area to kit up for diving.
Last week, we took leave of McMurdo Station by helicopter, to New Harbor, an additional research site about 50 miles away. We stayed for three nights at an established field camp there.
Approaching our field camp.
Our flight was entirely over sea ice, which extends beyond the horizon. The sea ice has been endlessly fascinating to me and it was such a joy to be able to see it from the air. I found this area strikingly beautiful:
An area of drift icefrom last summer that refroze this past winter. Drift ice is composed of many ice floes, individual plates of sea ice.
Arrival at New Harbor. We were lucky to have had such a clear day for our flight.
After unloading gear into our hut, we got right to work creating a dive hole in the ice. The first step was to use a battery-powered 10″ diameter auger to remove the first 3 feet of ice. Then a hole was drilled all the way through to the water, 9 feet below the surface. A metal coil through which a hot fluid was circulated (known as a hot finger) was inserted into that hole to melt the ice until the hole was wide enough to dive. We all took turns refueling the hot finger every three hours for about 22 hours.
Andrew working on drilling out the diving hole
As the hot finger ran, we had time for some cards…
and exploration.
An iceberg can be seen on the horizon which appears as a sharp white line. One sometimes feels as if they are on an alien planet here. On land, there are absolutely no detectable signs of life- no lichens or moss growing on the rocks, let alone some sort of little shrub, no birds in the sky, no burrows of little animals, nothing. The only living things are the microbes that live in the perpetually parched and frozen soil.
A pressure ridge created by the sea ice being shove against the shore.
The next afternoon, the dive hole was ready and the divers got to work.
Steve keeps a watchful eye on Jacob and Rowan as they prepare for their first dive here. Diving without the warmth of a dive hut at about 0F (-18 C) presents special challenges. Moisture from the divers’ breath can easily ice over their masks and clog the lines that supply the air from their tanks and are used to inflate their dry suits.
After sleeping in the warmth of the hut on the first night, several of us moved our cots and sleeping bags into the shelter we had set up near the dive hole for a night of sleep on the ice. As we all settled down and got quiet to fall asleep, we were alarmed to hear continuous cracking and popping sounds coming from the ice below us. Reassuring ourselves that the ice was 9 feet thick, we managed to drift off.
Beautiful blue light was transmitted into our shelter through the ice. (At this time of year, the sun does not set, of course.)
Early the next morning, we were awakened by the sound of repeated, deep exhalations. A Weddell seal had discovered the dive hole and was using it to breathe. It returned repeatedly over the course of several hours, taking about 1-1/2 minutes to complete its breathing exercises each time.
Weddell seal, breathing. They breathe through their nostrils which open and close like valves, allowing them to keep water out while they are diving.
After making our way across the ice to the hut for breakfast, we later returned to find our friend laying comfortably nearby. He spent the next 8 hours there.
In contrast, to the land, the sea below the ice is teaming with life, some of which makes an occasional trip to the surface.
The next day, the divers continued their work below, collecting samples and completing other tasks for their research.
Steve and Andrew preparing for a dive.
After diving was complete, everyone warmed up, had some snacks, and then set off on a hike to Commonwealth Glacier.
Explorers of a remote and alien world
Commonwealth Glacier is at the edge of the McMurdo Dry Valleys, a vast part of Antarctica that receives 1-4 inches of precipitation (water equivalent) per year, classifying it as a desert. This is the front edge of the glacier.
We returned back to our hut at 10 p.m. One thing you do not have to worry about here at this time of the year is the sun setting while you are on your way back from somewhere.
After dinner, I decided to spend another night on the ice rather than drag my stuff back to the hut. I was awoken once again, early the next morning, by deep exhalations. As I stood near the dive/breathing hole, I could hear the other-worldly liquidy-sounding clicking and whistling calls of the seal as it swam below the ice before emerging to breathe.
After just two days, the dive hole had already begun to freeze over. Weddell seals scrape the ice with their teeth to keep their breathing holes open.
The next day, we packed up and made our return trip to McMurdo Station. It was a great privilege and joy to visit such a remote and beautiful place that few others have ever seen.
Jacob and Rowan enjoying our beautiful return flight
Because it is dangerous for divers to fly immediately after diving because the change in altitude can cause decompression sickness (the bends), we flew back below 500′ altitude, giving us a beautiful, low angle view of the landscape.
We have been doing more and more dives trying to get in as much research as possible into the season. One of the really important parts of doing research anywhere is also looking around and seeing the environment. I have been fortunate enough to dive at the Jetty site since I started working here and so I also get to see how things have changed. While this site is the most dove on in the region, it is still full of amazing life and animals.
Here is a large hexactinellid sponge – or also known as a glass sponge. These are very large and are more frequent, or at least larger the deeper you go. This one is a really nice and healthy looking one that has a sea spider walking around on it.
However not all of them are looking great. This is the same species but is instead being actively grazed upon by some sponge-eating sea stars (Acodontaster).
As we go shallower we see very large sea squirts (tunicates -Cnimidocarpa in this instance) as well as soft corals.
Its by going back and back to the same sites that we get to see change. It is one of the amazing things about this place – the ability to watch a very slow to respond ecosystem change over time. What windows will this provide into our understanding of this amazing region in the future?
While conducting our research, we dive at a number of different spots in the Ross Sea. The site that we most commonly dive is known as Cinder Cones Seep. Cinder Cones Seep is particularly special because it was observed to begin seeping methane in 2011. This was a first for Antarctica! There were previous studies suggesting that the Antarctic region may have a large amount of methane reserves, but no eyes had ever been laid on an active seep. Being able to study this site will tell us a huge amount about the methane cycle in both Antarctica and the earth as a whole.
The white mats in the above picture are microbial mats, or biofilms filled with bacteria and archaea that are associated with the seeping methane. Photo credit: Andrew Thurber
Above the ice, the Cinder Cones Seep area has a lot of wind funneled onto it, causing most of the snow to blow away. The lack of snow on top of the ice makes the dive site extremely light, and when diving, we don’t even have to use lights! This is in sharp contrast to the other sites that I’ve visited here.
Andrew conducts a transect along the seep, filming the animals near the measuring tape to later be counted and analyzed.
The site has sea stars, nemertean worms, and anemones as far as the eye can see. There are so many of them everywhere that they’re often on top of each other.
A fish sits on top of a sea star, which sits on top of a nemertean worm, which sits on top of a bed of anemones!
Every time I dive at Cinder Cones, I get excited thinking about the implications of our research and the importance of learning more about this system. The samples collected from this site have been and will be a huge part of my research in the coming years, and I couldn’t be happier to see it with my own eyes and take samples of it with my own hands.
A seal swims towards a crack in the sea ice at Cinder Cones Seep, providing an easy access point for the marine mammals and incredible overhead features for us
It has been a dark year under the ice. Heavy snow has made very little light shine through to the depths. However, the scenery is no less spectacular. Here is a short clip showing what a “normal” dive looks like for us.
A short blog with a little more info about our arrival in Antarctica two weeks ago.
The plane landed safely on the ice! When the crew opened the rear hatch, we were immediately hit with a wave of icy cold air. Exiting the C17 aircraft is always really exciting as everyone is eager to get their first ever (or first of this season) glimpse of the icy continent. Once we disembark, we are quickly ushered along towards the transport vehicles that will be driving us to McMurdo Town.
Here is a compilation of some videos I took during this journey:
One of the main research questions we have focuses on the research site known as Cinder Cones. This is an area where methane leaks from the seafloor and is harvested by microbes for energy. Over the last 10 years the obvious microbial communities have been slowly replaced by dense beds of sand anemones (Edwarsia). This is what it looks like this year – tons and tons of them everywhere.
There are also tons of the star fish that seem to have come into this region. More on that in a future post, but there appears to be an interesting relationship between the stars and what the seep is doing to the ecosystem.
You can still see the small areas of microbial mats being present but they are far more reduced than previous years. However our research is showing that there is still a lot of methane being released. In the image above you can see the small patches of white which are indicative of where methane is seeping from the seafloor.
This area has become a real interesting and yet perplexing place to research, but like all good research sites – it keeps surprising us with its novelty and unexpected patterns. This all lets us better understand how the greenhouse gas methane is kept out of the atmosphere, one microbe at a time.
Ice is as far as the eye can see in Antarctica. It varies in age from million-year-old ice sheets that are miles thick, to annual sea ice that is measured in meters. One incredible form of ice in Antarctica is anchor ice, which resides on the seafloor down to a maximum of 90 feet deep. Anchor ice typically forms plate-like crystals that overlap each other to form jagged structures on the seafloor that are resoundingly beautiful.
Ice and life come to a head in the McMurdo sound. As the anchor ice takes hold, it covers the seafloor and the animals residing on it. This makes for an odd life for the animals subject to the freeze and changes the ecology of the seafloor. Because ice has a lower density than water, Anchor ice can actually pick up the organisms it freezes around and float them to the sea ice ceiling, incorporating them and causing them to eventually die.
An example of a seafloor brimming with both life and anchor ice
With that said, the combination of life mingling with ice is amazing to witness. Most evidence points to anchor ice as damaging to many species, but I have to wonder: In all this time of life and ice intertwined, are there adaptations to life in anchor ice? Are there organisms and ecosystems that require anchor ice?
The sponge Homaxinella Balfourensis encased in anchor ice. Anchor ice can almost entirely eliminate this species from an area, evident to researchers by discolored sponge skeletons.
The sea urchin Sterechinus neumayeri, which sits on top of an anchor ice field. S. neumayeri is numerous in the shallows of McMurdo sound, causing it to inevitably live within and around anchor ice. This sea urchin is largely a grazer, living off of algae, diatoms and animals such as sponges. One interesting fact about S. neumayeri is that it co-opts items from the environment for camouflage! You’ll typically see these urchins with pieces of shells and other objects on their spines.
A fish of the Trematomus genus. These fish often have antifreeze compounds that bind to ice forming in their blood. This is a great example of animal adaptation to living at extreme cold conditions.
During a dive at Cinder Cones last week, Amy and I got to watch an incredible battle between two male Weddell seals underwater.
I was originally just filming Amy framed with a beautiful crack in the sea ice behind her, but then, out of the shadows, two giant seals started making a bee-line for her!
Luckily the camera was still rolling and therefore I caught the scuffle on camera! Check it out:
Weddell seals (Leptonychotes weddellii) live farther south than any other mammal. They grow between 2.5 and 3.5 meters long, and adults can weigh between 400-600 kg. They persist on a diet of fish, crustaceans, krill, squid, prawns, cephalopods, penguins, and even other seals!
Weddell Seals can stay underwater for up to 80 minutes at a time and have been documented to dive over 600 meters deep. These long dives are for both foraging and for finding new breathing holes in the ice above.
