Diving here is such an important part of what we do that we’ll be writing about it throughout the season. So this is just the second of a series of journal entries about all the things that go into our scientific diving operations, or "dive ops" for short.
In my most recent journal entry, I talked about what is involved in making the call on if and where to dive. This time I’ll talk about what comes next, which is getting the dive gear ready to go.
We normally meet as a group at 8:00 AM every morning to coordinate the day’s activities. The first thing usually covered is what dive ops are for the day. I list who I want to dive, who I want to tend, where I think we should go, and what time I think we should leave. Then everyone else chimes in as applicable and we make sure that my ideas work for everyone and their own lab work constraints for the day.
If it works with everyone’s schedule, we usually plan to leave the boat dock for the dive at either 9:15 or 9:30. I’ll head back here to my office to double check the weather and take care of any e-mail etc. that I didn’t get to before the meeting. If I’m one of the divers for the day, then next I’ll head down to the dive locker.
The first thing I’ll usually do in the dive locker is get the gear wash bucket filling with fresh water. We use this to dunk our gear in when we get back from the dives and typically siphon it empty thereafter. Then I’ll grab a mesh gear bag and put in my mask, snorkel, fins, dive hoods, bag with wrist tubes and sea drops (explanation of those in another entry), one or two mesh collecting bags, and, if needed, a blunt-tipped collecting knife and/or dive light. Whether I’m diving or not, if I go out in the boats I take a waterproof "dry bag" with lots of extra hats, gloves, socks, etc. I put a bag with my drysuit gloves and insulating under gloves for the dive in there.
Next up is usually setting up my tank. I use the now full wash bucket to soak the strap on my buoyancy compensator vest that holds it to the tank (it stretches out when wet so needs to be soaking wet when I put it on for correct sizing). Then I put it and my two air regulators on the tank. Yes, two separate regulators on one single tank.
The most unusual piece of dive equipment we use here is a "slingshot valve" on our tanks. This allows us to mount two completely independent regulators on it. Pretty much all divers these days use two stage air regulators (I’m dating myself by noting that I learned to dive using both one and two stage regulators in the dive course). One of the last places one stage regulators were commonly used was in polar waters. That is because they froze up less often than two stage regulators.
Regulator freezing is a big concern, particularly later in the season when the seawater will be below 0 C (32 F) and, therefore, below the freezing point of any fresh water that might get trapped in the regulator. Normally, when regulators freeze, they freeze open. That may sound like a good thing, but the free-flowing air that comes out is very difficult or impossible to breath from. Even if you could, particularly at the relatively deep depths that we often dive to (100 - 130 ft), the air in our tanks is so compressed in volume that it wouldn’t take long for most of it to bleed out and be gone. Not a good thing!
The regulators we use are the standard at McMurdo Station, the larger US antarctic base at 78 degrees south latitude. The water is pretty much always -1.8 C there, so always below freshwater freezing. Bill, Jim, and I have all done diving research there in the past. The regulators we use have proven to be outstanding at resisting freezing in that even more extreme thermal environment. Still, it is nice to have a backup plan if they do. By using the slingshot valves, the buddy of a diver with a frozen regulator can turn the air off to it completely. The diver can then use his or her second regulator to make a safe return to the surface, hopefully with enough air left for a complete safety stop on the way.
After I get my tank set up, I put that, my weight belt, my dry bag, and my dive gear bag out on the deck of the dive locker for the day’s dive tenders to put into the boat. Then I head up to my room to change into my polypropylene long underwear. I usually wear two polypro undershirts, one light weight and one medium weight. On my legs a set of medium weight bottoms and on my feet a pair of thin polypro liner socks under wool socks. A pair of fleece pants and teva sandals go last to walk to the dive locker in but not to dive in.
Back in the dive locker, it is time to put the last and major dive underwear on. This is a heavy jump suit made of thinsulate. A lot of heavy winter gloves use this as insulation and the jump suit is thick and warm. A pair of thinsulate booties that aren’t quite as thick as the jump suit go over the wool socks on my feet. Then it is time to get into the drysuit.
After I get my legs into the dry suit I pause to put on my ankle weights. I use 2.5 pound weights on each leg in addition to the 38 pounds I wear in my weight belt. As I’ll discuss in a later journal entry, we have to vent air from our suits as we ascend and the only vent is on our upper arm. So keeping one’s feet down is a good thing. Also, wearing 43 total pounds of lead can be cumbersome so spreading it out a little is nice.
With my ankle weights now on, it is time to put the dry suit on the rest of the way. The suit has built-in boots but your hands and head stick out. So you have to get both hands and your head through water-tight seals on the wrists and neck. These are moderately thin, smooth rubber that is tapered towards the opening. We use talc to lubricate them first. But it still isn’t all that easy or fun, particularly getting your head through the neck seal. But it beats getting wet, at least in the frigid waters here!
Drysuit completely on, I grab my hat and waterproof mittens and head to the zodiac to take me to the dive site. Stay tuned...!