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Monday, December 3, 2007: Details of an Ice Dive
We have given several glimpses into diving beneath the ice but looking back through the earlier posts I see we haven’t given a good description of all the effort it takes to actually do a dive here. We have been doing sampling dives about every other day so I’d like to give a start to finish description of the effort involved with making those dives.


Yesterday’s dive at Cape Armitage started off snowy with limited visibility so even a short mile from McMurdo we couldn’t see the location where we were supposed to set up the new dive site. Skeptical, I loaded the Tucker with a shovel and a large dip net and headed to meet Tom and his drill rig. The rig is a tracked Caterpillar bulldozer, called a Challenger, pulling a tracked drilling rig and followed by a tracked trailer with drill bits. I followed Tom out of town because I figured even with my inexperience, I could follow a big yellow bulldozer in falling snow without getting too lost.

The visibility gradually improved so we were able to GPS and flag the location of the dive holes we needed to drill. After mounting the 4’ diameter drill bit on the drive shaft we started to drill but soon realized the snow was about four feet deep on top of the ice. That’s a problem because it leaves the water level too far down in the hole for divers to climb out of the hole. We stopped drilling, unhooked the drill rig from the Cat and Tom started removing the snow down to the ice surface. I was surprised how hard and compact the snow was here and how much effort it takes for a big bulldozer to cut through the snow. It is not soft and fluffy like one would think and took close to an hour to remove. With the snow cleaned from the surface of the ice we were able to again position the drill bit in the hole and continuing drilling through the ice.

As the drill bit cuts, the snow and ice chips pile up in a cone around the hole. Fast shovel work is required to keep up with the drill with the main goal to keep a path in the cone clear for water to flow out when the bit breaks through the ice. Well the bit broke through the ice OK and the water flowed, but then it kept flowing and flowing, starting a lake.

Realizing that the ice must have been pressed down slightly below sea level by the weight of all the snow, we quickly built a snow dam in the cone to stop the flow. Tom then had to move a foot of snow back in around our hole just so the dive hut wouldn’t be sitting in a lake of freezing water. Freezing your dive hut into the ice is not a good idea. Once the hole was finished and the snow was smoothed for moving in the dive hut, the dip net became the weapon of choice. There are a lot of ice chunks and slush that must be dipped out, one net at a time until the surface is ice free. Each full net is heavy so it’s a workout to clear the hole.

When we finished clearing the hole, we towed the dive hut and positioned it over the hole in the ice. With careful aiming we got it right the first time.

We then drilled a second hole a few hundred yards away going through the entire process all over again. It took half a day but that's what it takes to get the dive holes ready for divers.

Next step is readying dive gear in the dive locker and partially suiting up. The base layers that keep you warm under the actual dry suit are a layer of thermal polypro underwear and then a thick fluffy insulated jumpsuit. On each foot I wear a liner sock, a neoprene sock, a wool sock and an insulated bootie that goes over the top of the other three. Getting into the dry suit wearing all that insulation should constitute a Yoga routine. Hands are then wiggled through the wrist seals while making sure that the small plastic tubes called “tubies” lie properly on your wrist and protrude through the wrist seals. These little tubes are critical because they allow air to move into your glove, keeping your hand from getting tightly squeezed during descent. They also allow you to move warmer air from around your body into your gloves by shaking your hands vigorously above your head when your hands get cold. Next is getting your head through the neck seal, particularly difficult for divers like Nick with little necks and big heads. There are two main zippers on the suit that seal you in for what you hope is a dry dive.

Our other dive gear consists of the air tank with two tank valves, each with its own separate regulator. This redundancy is a safety measure in case your primary regulator freezes and free flows air while you are doing your dive. The second regulator is on your chest within easy reach so you can switch regulators when needed. Switching regulators is a skill you must demonstrate on your check out dive here before you are allowed to continue diving in Antarctica. It sounds like a simple feat but the restricting tightness of the hoods and frozen lips makes it difficult to get a regulator in or out of your mouth. The dive guru here, Rob Robbins, demands that skill even though he says that the regulator freeze ups happen on less than 1% of the dives. I’m really glad however he made us practice that skill because I have had two free flows out of ten dives. I guess I'm really messing up his low freeze up percentages. The risk of freeze ups mandates diving with a buddy essential because the bulky insulation and dry suit make it extremely difficult to reach around and turn off your own valve to the free flowing regulator. On your own you have to quickly take your tank off to reach the valve so having your dive buddy there to turn off the valve to the free flowing regulator keeps the air in your tank and your stress level down- Thanks Stacy! Twice!

All this dive gear and the sampling gear are loaded into the Tucker and for the drive to the dive site. Once at the dive hut everything is unloaded from the Tucker into the dive hut. Preparation for the dive begins with again clearing the ice from the dive hole and then setting up our safety line. This weighted line drops through the ice hole and extends to the bottom. Spaced along the line are flags and three flashing strobes and a small emergency air tank with a regulator. The flags and strobes help us keep track of the dive hole in the twilight to dark conditions under the ice. Also attached to the bottom of the line is our box of sampling cores, an underwater digital camera and an underwater video camera.

Final dive preparation begins sitting on the edge of the hole and wiggling in to a shoulder harness weight belt weighing forty pounds. Two pound weights are then strapped on each ankle and fins are strapped on. All important dive computers are fitted to wrists or hoses and the air tank backpack is loaded on and air is turned on to both tank valves. Note that in under ice conditions, no buoyancy compensators (BC) are used because rapid assents to the surface are a bad idea, creating more danger than safety. Slushy frazil ice under the sea ice can obscure a diver pressed up against the ice, plus it's very difficult to see your dive hole when at the bottom of the ice. Proper boyancy is therefore acheived by adding or releasing air directly from the dry suit. It takes some practice but good control of your boyancy using the dry suit becomes second nature. On the head go a neoprene "gorilla mask", a thick neoprene hood and finally a latex hood. These three hoods keep my head surprisingly warm and dry but at the price of being a bit constricting and claustrophobic. It’s sure better than a wet head, but I prefer to put these on at the last minute possible before the dive.

The face mask gets its requisite spit and is filled with icy seawater so it won’t fog up. By this time I am usually getting overheated and sweating inside my suit and anxiously looking forward to getting in to the cold water. Each hand gets a wool glove and then the dry glove is stretched over a sealing ring in the dry suit for what you hope are dry hands (sometimes these leak- ask Nick!). Putting on dry gloves requires help from another person so we always have at least one dive tender assisting divers throughout the preparations. My mask goes on last and the dive tender works the mask seals under all the hoods so the mask will seal against your skin. A final check of the gear, grab a dive light and then you are ready to drop in the hole ....

...unless the hole is plugged by a thousand pound seal breathing in your hole. In that case you just wait until the seal is willing to let you use his breathing hole. Breathing holes are critical real estate here and the Weddel seals aggressively defend their breathing holes against other seals. Fortunately they seem very unconcerned about us divers using "their" holes.

Dives typically take around thirty to forty minutes to complete the sampling, explore the area and safely ascend back to the surface in the dive hole. Each diver has to ascend through the ice hole singly while the others wait just below the ice. Occassionally we even have to wait for a seal to vacate the hole before we can make our final ascent to the surface.

Tanks and weights are removed and lifted off the diver and fins removed so that the diver can climb a metal ladder that was lowered in the hole during their absence. Once out of the water, mask and gloves come back off and you stand next to the hut’s heater trying to get your lips, fingers and toes functional again. For me it’s only these extremities that get cold and the longer the dive the colder they get. It’s manageable though and each dive the cold seems less of an obstacle.

The conclusion of the dive means bringing up the down line loaded with samples and cameras, reloading the Tucker, driving back to the dive locker and spending an hour cleaning and prepping gear for the next dive. Samples are processed, cameras are downloaded and cleaned and finally much food is eaten to replace all the calories burned during the day.

Subsequent review of the digital images or video sometimes leads to the dissappoinment of finding the data unuseable for one reason or another. That forces a return to the site to repeat the sampling. Unfortunately the hut has often already been moved so the the dive is repeated without a warm hut. It's good incentive to get it right the first time.

Yesterday’s dive at Cape Armitage took us a total of about 9 hours to complete. It's a lot of work to do a dive in Antarctica but just seeing these unique and beautiful under ice communities is reward enough.


Brrr!!!! (but i'm a weather wimp heading to the tropics)

vera just sent me the link to this entry--very very cool

Happy belated birthday!

I found my way here via "Heraclea" and I gotta say I find this fascinating! Stay dry and I look forward to viewing more photos from the bottom of the bottom of the world.


Interesting experience. Stay dry, find something to get into, but everyone likes doing somethings

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This material is based on work supported by the National Science Foundation under Grant No. ANT-0619622 ( Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.