Frozen in Place: The Mystery of the Mummified Seals

Weddell seal near Cape Bernacchi
Seals? Yes. Polar bears? No: A young Weddell seal raises its head to check us out before continuing its nap on the sea ice near Cape Bernacchi. It probably got onto the ice via a hole several yards away that was cut earlier in the season by Sam Bowser’s dive team.

Let’s clear up one thing that I get asked a lot: there are no polar bears in Antarctica. That’s the Arctic. The only mammals are marine mammals, found along the coasts: seals — which I saw on a number of occasions — and whales —which I did not see at all. The only birds I saw were skuas, which are feisty brown birds related to gulls, and Adélie penguins. Uphill from the sea ice pressure ridges in New Harbor beneath the Double Curtain Glacier was a highly unusual sight — several square yards of gray and tan moss — the only plant life I saw growing in soil the entire seven weeks I was in Antarctica. Further inland, walking the gravel hills and ice-covered lakes of the Dry Valleys, you and your companions are the only living things in sight — nothing green, feathered, scaly or furry. The exception was a lone skua occasionally spotted in the vicinity of the Lake Hoare field camp, nicknamed Taylor by the field camp residents. The major life forms of the Dry Valleys are microscopic organisms in the lakes, streams and soil that scientists sample and study as part of the long-term ecological research study, but of course, they’re not visible without a microscope.

Moss in the Dry Valleys
A rare sign of life: This patch of moss on a hill between the Double Curtain Glacier and a pressure ridge was the only plant I saw growing in the Dry Valleys.

Against that backdrop, it was startling to periodically come across the bodies of mummified seals in the Dry Valleys, several miles from the ocean. Seals are built for swimming. Underwater footage shows even 10-foot-long, 1,200-pound Weddell seals gracefully gliding along. They spend most of their time in the water, occasionally poking their heads out to take a few breaths. Periodically, they laboriously haul themselves onto the ice to rest, like the young Weddell seal in the photo at the top of this post. The ellipsoidal body shape, wing-like flippers and tail that serve them underwater are definitely not made for walking. Once you’ve seen a seal galumphing with great difficulty across the ice like a giant slug, it’s even more remarkable to imagine how they could travel for miles on their bellies, dragging their rotund bodies over ragged lake ice and gravel hills. An oft-quoted statistic is that mummified seals have been documented as far inland as 41 miles. If that’s the case, this one at Lake Bonney must be one of them, since that’s about how far the lake is from McMurdo Sound:

Mummified seal, Lake Bonney
This mummified seal atop Lake Bonney traveled about as far as any have managed — around 41 miles from the sea.
Mummified seal, Lake Bonney
A closer look at the Lake Bonney seal, lying on its back atop ablated lake ice.

The dry, freezing climate and lack of bacteria and invertebrates that break down carcasses in warmer regions leave the seals in varying states of preservation that make it impossible to tell how long they’ve been lying there by their appearance just by sight. Some are mostly skeletal, some still have a substantial amount of leathery skin attached, but you can’t tell if they’re a few years old or several hundred without doing a laboratory analysis of carbon and nitrogen isotopes.

A research team led by Paul Koch and Brenda Hall in the 2012-13 and 2013-14 seasons has done just that. They saw these seals not as a weird curiosity, but as a way to investigate the history of seal populations over the past 1,500 years, and how they adapted to changing amounts of ice in McMurdo Sound in terms of their diet, which is also revealed by the chemical analysis. Up until about 500 years ago, McMurdo Sound had far less ice than it did afterwards, when ice shelves formed. Knowing how the seals responded and how their diet changed would help predict how warming oceans might affect them in the future. To that end, the scientists a undertook a comprehensive inventory of Dry Valleys mummified seals and took over 400 samples to be analyzed (read more about the study in the Antarctic Sun and this press release). “Studies of fossils let us see how species do or don’t adapt to environmental shifts. Here, we are using that approach to explore the adaptability and vulnerability of different Antarctic seal species to less icy conditions in the near future,” said Koch.

If you’ve read every single one of my Antarctica blog posts, you’ve encountered a few of the following scenes before, but I thought it would be interesting to bring them all together in one place, along with some information about what is known about them.

Ferrar Glacier, seal skeleton and pressure ridge
This seal near the Double Curtain Glacier didn’t get very far uphill before succumbing. The Ferrar Glacier is in the distance.
Mummified seal skeleton
Close-up of the seal skeleton. The flipper anatomy is very clear on the right.

The presence of mummified seals has posed a scientific mystery since the first explorers of the region in the early 1900s ran across them. They’re generally small, and I have run across only one account of researchers encountering a live seal in the Dry Valleys. The current assumption is that these are young seals that get lost during whiteout conditions in the harsh Antarctic winter, when the seals usually stay near cracks in the sea ice. Without visual cues, they get turned around and crawl along in a futile search for the sea until they expire. As of October 2015, Koch’s team published that it had reported identified mummies of over 300 crabeater seals, 100 Weddell seals and around 20 leopard seals, a proportional breakdown roughly corresponding to their current numbers in the sound. That sounds like a significant number of wayward seals, but the mummies can be as much as 1,500 years old. Koch told the Antarctic Sun that it may be that only one or two lose their way each year.

The leopard seal shown below, on the Lake Fryxell side of the Canada Glacier, is a rare sight on a few counts. Leopard seals make up less than 5% of the mummified seals. This one is pretty much intact, including fur, which is unusual. And unlike the vast majority of the mummies, we know for sure that this one is a recent arrival, because this area is frequently traversed by Dry Valleys researchers and they took note of its appearance a couple of years ago.

Leopard seal near Lake Fryxell
A mummified leopard seal is a rare sight. This one made it past Lake Fryxell, which is in the background.
Mummified leopard seal
A closer look at the leopard seal.
Mummified seal near the Canada Glacier
This seal skeleton was in the general vicinity of the leopard seal, on the Fryxell side of the Canada Glacier. Odds are it’s a crabeater seal, which are far more commonly found than leopard seals. (The remaining teeth look right for it to be a crabeater, too.) The top of the seal has been sandblasted off over the years by winds ripping through the valley, but you can see that the part facing the ground is probably in one piece.
Mummified seal near Canada Glacier
The same seal as above, with the Canada Glacier behind it to the right.

Mummified seals are not only found in the Dry Valleys. There’s one on the black sand beach at Cape Royds. It’s notably well preserved, but it’s right by the sea ice so there is no mystery as to how it ended up there:

Mummified seal, Cape Royds
On the black sand beach at Cape Royds, the tan object in the center of the photo is the mummified seal shown below. (Photo is slightly blurry because it is a detail of a broader vista.)
Mummified seal, Cape Royds
Mummified seal on the black sand beach at Cape Royds.

I photographed all the mummified seals I encountered, with the exception of one that had remarkably made it the length of Lake Hoare and part way up a hill near the Suess Glacier. It was dismembered into two halves, lying in the dirt side by side, which for some reason struck me as more grotesque and disturbing than a dead seal in one piece. I just didn’t want to look at that again! But probably the strangest one I saw was also near the Suess Glacier: rather than lying on its back or its side, it’s perched on its belly, tail curving upwards and head lifted as if flash-frozen in mid motion.

Mummified seal, Lake Hoare
This mummified seal at the west end of Lake Hoare is unusual for coming to rest in a pose that gives it a strangely animated look. Rae, the Lake Hoare camp manager, suggested that it was underwater for a long time, and revealed by a retreating shoreline. This view faces the direction the seal came from. It would have to have crawled around the Commonwealth Glacier, down the length of Lake Fryxwell, around the Canada Glacier and down the length of Lake Hoare to reach this point!
Seal near Suess Glacier
Close up of the seal near the Suess Glacier, looking west toward the glacier, which is in the upper left corner.

The scientists who have studied these seals are interested in them as a fossil record and a way of understanding the history of ocean ecology. What drives the seals to travel for miles over land and how they survive the journeys is ultimately beside the point in terms of their research. The lack of information about that aspect is a reminder, though, of how little we still know about what Antarctic animals do during the long, dark winters — that includes seals and penguins. At one of the science lectures, I asked Jennifer Burns, who has been studying Weddell seals for over 20 years, if she had seen any changes in behavior related to climate change. She responded that she hesitates to make comparisons because monitoring and tracking hardware is so much better quality now than 20 years ago. Devices are smaller and less intrusive to attach to the animal — in the past they were bulky and generally didn’t stay on long. In years to come, perhaps more seals will be tracked and shed some light on the mystery of the lost seals.


The Road to Double Curtain Glacier

Antarctica sea ice
Sea ice pressure ridges looking toward the Ferrar Glacier.
Pair of skuas in Antarctica
What does the skua say?: Haw! Haw! Haw! Haw! Haw!

I’m back from Sam Bowser’s camp — helicopter picked me up at 5 p.m. yesterday. Sam, his wife Laura and the rest of the team were really welcoming and fun to be with, and took me to a couple of fantastic places. I’ve already posted the trip Laura and I made in the previous blog entry.

The next day Sam, Laura and I went by snowmobile to a fascinating scenic spot that doesn’t really have an official name, but unofficially they call it “the road to Double Curtain Glacier.” Comic relief near the beginning of our trip was provided by a pair of nesting skuas standing on a rock. We stopped the snowmobiles and I got out the telephoto lens. They looked at us, and we looked at them, and then another skua flew a few feet above them, to which they responded by cawing loudly, “Haw! Haw! Haw! Haw!” as if to say, “Don’t even THINK about landing here while we’re on this rock.” Then they calmed down, then they started up again. It sounds like someone laughing sarcastically.

Pair of skuas in Antarctica
We must protect this house!
Pressure ridge near Double Curtain Glacier
The “Road” to Double Curtain Glacier has a lengthy section that looks like this, with very high pressure ridges where the sea ice has been pushed up against the coastline.

What we traveled on was not really a road, of course, it’s a flat area of coastline around New Harbor that this time of year is covered with snow and ice, and it looks like someone plowed a flat area of snow for vehicles and left the piles of snow and ice in a very even line on the sea ice side of the lane. What those piles really are is a pressure ridge, which is a ridge of ice pushed up by the movement of the sea ice. I saw such ridges on the McMurdo Sound sea ice when I was doing my training, but they were only a few inches high. I saw them by the New Harbor camp but they were a few feet high. But as we got closer to the Double Curtain Glacier, the lane got narrower and the wall got higher, forming a crazy Baroque facade that I’m guessing was 20 feet high in places! At some point, the road became so narrowed and slanted we parked the snowmobiles and continued on foot.

Scallop shells
Sam was interested in the large numbers of scallop shells that had been carried to the shoreline by the ice.

The ice has begun to melt and form weird shapes of unending variety. You don’t want to walk too close to one of those towers in case it becomes unstable and collapses. The pressure ridges have carried along numerous scallop shells which are scattered in the ice.

Blue wave of ice
One of the odder sights was this blue curving wave of ice. I wanted to get a closer look, but it was hard to tell if the ice was stable enough to walk on, so I dared go no further.
Fang, the ice formation
I named this formation “Fang,” because it looks like a cartoon wolf in profile.

We eventually came to a place totally blocked off with ice. We climbed a little ways up the hill under the Double Curtain Glacier, and saw a mummified seal skeleton and some moss — the first plant life I’ve seen here. 

Ferrar Glacier, seal skeleton and pressure ridge
Mummified seal skeleton on the hillside above the pressure ridge. The Ferrar Glacier is in the distance.
Mummified seal skeleton
Close-up of the seal skeleton. The flipper anatomy is very clear on the right. There is some dried, mummified skin still attached. No telling how long it’s been here; could have been many years.
Double Curtain Glacier
The Double Curtain Glacier emerges from the fog above the seal skeleton. You can see how it has two different leading edges, hence the name “Double Curtain.”
Moss in Antarctica
There was no plant life in evidence except a patch of moss with white salt crystals on top, not far from the seal skeleton. This is a close-up. We took care not to walk on it because it’s very delicate.
Herbertson Glacier
From this elevated spot you get a good look at the Herbertson Glacier beyond the pressure ridge and across the sea ice from the Double Curtain Glacier.

Many of the photos shown here were from that slightly elevated vantage point on the side of the hill. It was a clear day and we could see the Herbertson Glacier (which was directly across the sea ice) and the Ferrar Glacier (to our right from that spot). As we were leaving, we also drove onto the sea ice about halfway between the Herbertson and the Double Curtain and I got another nice photo of the Ferrar.

Ferrar Glacier
The Ferrar Glacier in the distance, as viewed from the sea ice.

I am incredibly fortunate to have been able to visit this place, which one of Sam’s team told me very few people have gotten to see. Unless you are staying at the New Harbor camp, it is relatively inaccessible. I am working right now on processing some of the 3D captures I made there so I can bring back a little bit of the place for others to see. Once I clean up these files I’ll be able to fabricate them as sculptures with a 3D printer or router. I’ve got one capture processed already. Here are a couple of screenshots of it from the 3D file creation program:

3D file of pressure ridge
3D file of part of the pressure ridge, shown with the “texture layer” (the coloration).
3D file, untextured
3D file shown without the texture layer.