Sea Ice Training and the Ice Cave – 10/20/08
The Hagglund that brought us out to the sea ice
The Hagglund awaited us as we prepared to depart for sea ice training. This was a requirement since our expedition is to be based on the ice that forms over the ocean of McMurdo Sound every austral winter. We had to learn how to identify cracks and do thickness profiles of the ice across them, how to determine if a crack was safe to cross depending on what type of vehicle we were traveling in, and how to make ice anchors to secure things like our tents or equipment to the ice.
The tide crack at the transition between the fast ice near McMurdo Station and sea ice
The first introduction was looking at the tide crack just off from McMurdo Station. This forms between the fast ice which is attached to land and doesn’t move and the sea ice which succumbs to the rising and falling of the tides. A tide crack forms everywhere where there is sea ice meeting land. We poked at it with bamboo poles to check for snow thickness and competency to make sure where we were walking was secure.
Driving along the Cape Evans Road
We hopped back into the Hagglund and drove north along the flagged Cape Evans Road in search of cracks between plates of sea ice. We drove past the Erebus Glacial Tongue, through the Dellbridge Islands which are actually the high points of a former volcanic mountain that is buried beneath the ice. Soon we came up on the crack we were looking for.
Flags marking a crack crossing the Cape Evans Road
We pulled up to some flags marking a crack that crossed the roadway. Now we would learn how to travel safely across the sea ice. Most first-year sea ice is about 2-meters thick (or about 6.5 feet), but the minimum thickness of ice to travel on is 30 inches, so in most cases we would be okay. The gap that forms in a crack is of critical importance to determine whether or not you can ride across it, and the minimum width is dependent on the length of how much of the vehicle is in contact with the surface. A crack is considered safe to cross if it is 1/3 or less of the length of the vehicle treads.
Profiling a crack in the sea ice - drilling to determine ice thickness
First thing when approaching a crack is to identify the edges of it by poking a bamboo pole into the snow. The snow should be excavated across the crack down to the ice surface. Then you drill to penetrate through the ice into the underlying water. This is done on either edge of the crack and in the gap. The thickness of the ice is measured through the drilled hole and recorded. The profile of the crack is then complete. The ice around the crack we analyzed was more than 30 inches and the width of the crack was less than 1/3 of the length of the vehicle, so it was determined that it was safe to cross and we carried on.
Making a V-thread ice anchor
One of the more important things we learned was how to make a V-thread ice anchor. Being out on the sea ice there is very little snow cover. V-threads are used to secure things to the ice. The wind can be very strong in Antarctica, and anything not secured will surely blow away. V-thread ice anchors are constructed by drilling into the ice either with ice screws, as pictured, or by using a drill. Two holes are drilled at about 45-degree angles that intersect each other. A piece of strong rope is passed through these, knotted together, and anything that needs to be secured is lashed to the anchor line. The ice is quite strong, and when the wind blows powerfully, the ice anchors will make sure nothing blows away.
Mt. Erebus steaming in the distance
Remains of an iceberg frozen in the sea ice
Tent Island (left) and Inaccessible Island (right) of the Dellbridge Islands
Once we were finished with our training we turned and headed back toward McMurdo Station with a steaming Mt. Erebus looming above us amid a picturesque swirling wispy sky. We could see the remains of an iceberg nearby that became locked within the sea ice when it froze during the earlier winter. We passed through the Dellbridge Islands that we came through on our outbound journey. Yet what was in store was the highlight of the day. We found out that our next destination was an ice cave.
The ice cave entrance in the distance
I knew this was going to be amazing as soon as I jumped out of the Hagglund and saw the ice cave entrance in the distance.
The view surrounding the ice cave entrance
As we approached, the scene quickly became other-worldly, like nothing I had ever laid eyes on before. We were at the very edge of the Erebus Glacier Tongue, and about to walk into the glacier. This is where the Erebus Glacier, spilling off from the Mt. Erebus, goes out to sea. And here, at this location, the sea ice afforded an ideal location to walk right up to it. The icescape became an uplifted, gnarled jumble, very different than the relative flatness of the sea ice we had spent the day out on.
Entering the ice cave
As I slid through the narrow entrance to the ice cave and down the slippery corridor drawing me deeper in, I began to wonder if I was still on Planet Earth.
Easing down the corridor, going deeper into the ice cave
Wow! Am I really seeing this? Am I really here? Is this really real? Stalactite spikes of ice were hanging from the ceiling of the corridor leading to the inner cave chambers. The light became not like the bright sun-splashed scene out where we had just been. It was starting to become a greenish-blue as light was filtered through the overhanging snow and ice. The corridor was steep and slick, but I had to go further inside this natural wonder.
Ethereal blue light in the crystal palace
Inside the cave, away from the influence of unfiltered sunlight, a crystal palace started taking shape, draped in an ethereal blue light that only deepened as I went in further. The ice took on new shapes and character, and I was astonished as I ventured further into the main chamber.
The main chamber
The ceiling, walls, and internal structures of the ice cave were formed from the glacial ice tongue. If melted, you could drink the fresh water. The floor is sea ice, which is salty from the frozen ocean water. The main chamber was the most magnificent of the whole with a large twisting spine leading up to a recessed area capped by skylights to the outside world, a world I felt a million miles away from at the moment.
Looking toward the back chamber
Further along, moving deeper within the ice cave, a rear chamber could be seen. The ice bridge over the entrance seemed to bar the way, but a peek back revealed a narrow chasm lit from above with ice crystals of various shapes and dimension all around.
Gazing out the ice cave entrance to the vast sea ice
I turned and walked back the way I came, feeling energized and exhilarated by this adventure. Gazing out the entrance I was reminded of where I was. I was floating over McMurdo Sound on a vast and dynamic layer of ice; from one other-worldly place to another. What a wonderful treat. What a special place.
Dangling from an ice axe above Mt. Erebus
We decided to have a little fun while waiting for others to fully enjoy their own experience in the ice cave. Yup, that’s me, hanging from an ice axe over Mt. Erebus!
The Hagglund out of gas
Reality soon set in hard, bringing all of us back for our time in the ice cave. As we gathered the group back into the Hagglund to drive back to McMurdo Station, not long into our ride, we ran out of gas. A little bit of patience, and reserve fuel, we were on our way, and back in time for dinner.
