Frozen Ocean
Most people know that water freezes at 0˚C or 32˚F. That's freshwater, like from your kitchen sink or water in a pond by your house. Most people don't know that salt water, like water from the ocean, can freeze too. The salt actually makes it harder to freeze the salt water, so it must be colder for that to happen. The ocean water needs to be about -1.8˚C or 28˚F to freeze. To most people, that's a fact that they memorize, but never experience. Here in Antarctica, it's happening all around us!
Surrounding McMurdo Station in August is a frozen ocean. Where I live the ocean almost never freezes, so it's hard to explain to someone what the situation is down here. It doesn't just freeze. It freezes quite thick, like 6 feet thick. That's easily thick enough to support the weight of all those vehicles we talked about yesterday, including the LC-130 or C-17 planes.
I only bring this up, because the worms Dr. Marsh and his team are interested in studying are found in the sediment (mud and sand) at the bottom of the ocean. Hmmm... I see a problem.
The worms don't come to you...
So here's the problem. How are we going to get the worms if they are at the bottom of the ocean and that ocean is frozen solid so thick that you can land an airplane on it? Anyone?
The solution is that we must go to the worms. So, to begin, we must first get to the water. Well, how do you get to the water through six feet of sea ice? I am so glad you asked. It's my new favorite piece of heavy machinery. We use a giant drill!
Location, Location, Location
First, we need to find the spot to drill. This is not as easy as it might sound. The top of the ice looks pretty much the same everywhere, white and frozen. Underneath the ice can be very different. Some places can have 15 feet of water; others can have about 1,500 feet. So, how do you know where to drill? Fortunately, previous SCUBA divers have left maps, notes, and knowledge for us to use. Drs. Marsh and Kim (Adam and Stacy) have been diving here for many years. Together, they have a really good knowledge of diving under the ice. They use GPS to mark locations and can then use the GPS to return to those dive sites.
Dr. Marsh uses GPS to locate the dive site.
Drilling
First, we clear the ice of the two feet of snow. This step actually isn't necessary, and sometimes results in some undesirable consequences. We probably won't be clearing the snow at any of the other holes that we drill this season after the experience on the first one. I'll let you see what happened in the video below.
We first use a bulldozer to clear the snow.
We cleared about two feet of snow off this particular spot.
After the snow has been cleared, we use the bulldozer to put the drill into position. Steve Zellerhoff is our fabulous drill rig operator. Attach to the drill is an auger bit that is 4 feet in diameter. That's going to cut a hole 4 feet across through the ice.
Steve Zellerhoff uses the drill to drill us a diving hole.
It's amazing to watch that machine punch a four foot hole through the ice.
The drilling operation is noisy and fun. The drill basically grinds the ice into shavings that can be shoveled away. The amount of time it takes depends on the thickness of the ice. In this case, it took about 3-4 minutes of drilling to get through 6 feet of ice.
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When we were done drilling we would have liked to place a dive hut over the hole to keep it from freezing, but unfortunately so much water came up and flooded the surrounding area that we couldn't put the dive hut in position. What do you think would have happened to the dive hut if we had put it over the hole with all the water there?
So, instead we waited twelve hours for all that water to freeze. This was a good time for pictures.
It's a little hard to believe it, but there is over 100 feet of sea water underneath Steph and the Pisten Bully.
Stephanie and Annamarie doing their Antarctic cold jog across the ice.
Besides all the water that poured up through our hole, what else do you think froze? Our dive hole! So, we had to break up the new ice over the hole (about two inches in 12 hours). I would like to thank the seal that used our dive hole to breathe from because that helped keep it partially open and made for easier chipping.
Here's what the hole looked like after a few hours. See the two holes within the hole. We think a seal kept them open. (Photo courtesy of Dr. Stacy Kim)
Mike and Dr. Marsh clear out the hole before the hut is dragged in place. (Photo courtesy of Dr. Stacy Kim)
Then we positioned the dive hut! At the end of a few hours work, we had this wonderful hole. Doesn't it look inviting? Who's ready to jump in? Remember, that water is 28˚F!
Here's the finished dive hole.