Sea Ice Challenges
This hole, intended for divers, has been occupied by Weddell seals (Leptonychotes weddellii). While these seals are generally friendly, we try not to perturb them and will leave them undisturbed in a hole whenever possible.Marine science near McMurdo Station, Antarctica, requires getting through the sea ice to access the ocean. There are few areas along tidal cracks where holes can form naturally, but the locations of these are very limited. Making a hole large enough for a scuba diver or a standard science-capable ROV (1 m across) requires a substantial investment of time and resources. There are three basic techniques.
The "wagon train" involved in drilling a hole in the sea ice. In front is a Pisten-Bully passenger and gear transport vehicle towing a generator sled. Next is a Caterpillar tractor towing the drill rig, a hut for placing over the hole, and the drill bit. In the background you can see Big Razorback Island, which is one edge of a flooded volcanic caldera.
Drilling a hole takes less than an hour, but requires a D8 tractor and someone who can drive it, and a trained operator for the drill rig. It also is limited to areas within tractor driving distance from McMurdo Station (40 km), and fairly smooth ice all the way there.
The drill rig in operation. It�s hard to imagine that you are standing on frozen ocean until the gush of sea water washes over your boots when the drill breaks through. In the background is Mt. Erebus, an active volcano that is part of Ross Island.
Drilling a hole also involves a substantial amount of �driving a D1 tractor� which is a polite way of saying shovelling. While this does not require any special skills (so they will let the scientists do it), it is exhausting.
BlastingA second method is to blast open a hole with dynamite. This requires a trained explosives expert and a special helicopter flight to deliver the explosives. The blasters will detonate two shots, the first to break the ice, and the second to clear the hole of large ice chunks. The resulting hole is irregular and unstable around the edges, so you wait 24 hours for the blasted ice to refreeze in a thin layer, and then go in with a chainsaw to clean up the edges and create a stable platform.
Master Blaster Marty Reed setting out the initial blast configuration. The sticks of Powerfrac are arranged like beads on a string to go through the ice and extend 3 feet below it. Once the cord is arranged, Marty and his assistant Oly Peterson will drill a pilot hole through the ice to place the charge.
Kaboom! There are two holes being blasted simultaneously in this picture, so that even if seals take over one hole we will still have a second hole to dive through. We are sure there are no seals nearby that could be disturbed by the blasting, because before we put them in, there are no holes for them to breathe through.
Chainsawing back through the blast crater. Though chainsaws and seawater are not a very good combination, it usually only requires 14 field rebuilds before the job is completed.
MeltingA third option is to melt a hole in the sea ice. It takes about 24 hours of melting if the ice is 2 m thick, and 3 days if the ice is 7 m thick. The melting apparatus is a modified pressure washer running heated glycol through a coil, so it requires refueling the power washer every 5 hours, and the generator every 3 hours. Aside from not letting you get a full nights sleep, this requires setting up a full field camp so that you have shelter, food, and communication in case the weather turns bad and your transportation cannot return to pick you up when scheduled.
An A-Star helicopter delivers the Hotsy hole melter to a field camp. It required two trips to also bring in the generator, as well as all the fuel, the camp supplies, and the people to support melting a hole.
Positioning the generator requires a bit of grunt work. The generator (fueled by gasoline) runs the pump and the temperature controls in the Hotsy. The Hosty (run on diesel), heats the glycol.
The stinger, or heated coil, is slipped into a pilot hole that we have drilled. The heated glycol is circulated through the closed loop system, warming the water around it and melting the ice.
It is obvious that it takes a substantial effort to make a hole of this size through the sea ice. The costs, in terms of equipment, person power, and time, are all substantial. Contrast this with the effort it will take to make a SCINI hole, 15 cm in diameter rather than 100 cm. One person on a snowmobile can go out with a hand held power head and zip a hole through 7 m of ice in 40 minutes. In fact, the pilot hole that is drilled for both blasting and melting is all that is needed to launch the SCINI ROV!
For locations close to the station, the equipment needed to drill at 15 cm SCINI hole can be carried on a single snowmobile, though we generally travel in pairs for safety.
It takes only one person to drill a 15 cm hole with a Jiffy or Badger powerhead. However, if you are too lazy to add the 1 m long drill sections one at a time, you can come up with creative solutions for drilling with 3 flights at once.
The only ones who won�t be happy with the SCINI solution are the Weddell seals, who enjoy the 100 cm holes for the breathing space they provide.