Apr - Diving
Diving for Science
Rothera Station Diary - April 2003
There was a crisp feeling to the air as it blew over my face. I could feel the start of an ice cream headache beginning and was thankful that the neoprene hood covered my ears and neck. The sledge glided easily through the fresh snow as we rounded the new Bonner Lab and over the end of the runway to what would be our entry point.
The surface team go straight to work. Ian Heffernan makes his way to the water’s edge with his shovel to clear safe passage for Kirsty Brown and myself. Andy Miller unties our scuba cylinders and readies them for us to don. Once into our jackets they both assist with doing buckles and straps, as our hands are restricted when inside the neoprene mitts.
We make our way to the water’s edge where we are able to sit on the ice and don our masks and fins. The surface team run through our pre-dive checks: main air on, bail out air on, suit inflation connected and working, jacket inflation connected and working, weight belt free and clear, timing device on, compass and knife all present. I confirm my dive profile: 27 metres maximum depth, 20 minutes maximum bottom time, safety stop 3 minutes at 6 metres. Ian gives me a tap on the shoulder, 'Ok John, you’re on the SMB [surface marker buoy] and good to go.'
I slide down off the ice into the water and start to wade out to shoulder depth, all the time holding my main breathing demand valve clear of the water. This reduces the chances of having an air free flow, with the current wind chill factor is minus 20°C any water that would get in would instantly freeze. I empty all the air out of my jacket and suit and look over to Kirsty who is doing the same, we acknowledge each other with a small nod, turn and give the surface team an OK signal and both submerge.
Once on the bottom I steady for a moment to make sure that everything feels ok, I check my timer and see that it is on and note the temperature, -2°C. The burning sensation to my cheeks and lips is like a red-hot poker, but it quickly abates to a comfortable numbness. The water seeps into my mitts and my own body heat then warms it to a comfortable level. I turn my torch on and scan around to Kirsty, who gives me the ok signal. We descend down the steep slope.
The natural light starts to fade as we reach twenty metres and we rely more on the torches. We keep swimming, 21, 22, 23, 24, bingo the torch light flashes across our objective: transect one – 25 metre site. Twenty five concrete blocks topped with blue painted plasticine in a five-by-five metre grid. Kirsty brings out her clipboard and goes to work noting what, if any, damage has been inflicted on the blocks by passing icebergs. This only takes a few minutes as the site is relatively untouched, she gives the sign that she has finished. We head north staying at 25 metres for a 40-metre swim to transect two.
As we swim our torchlight crosses a big scour in the seabed. I check my depth 25.5 metres and think to myself, ‘that must have been one big ice berg to be hitting the bottom here.’ This, of course, is the main part of Kirsty’s experiments down here, which I refer to as ‘The Ice Berg Impact Study.’ The grids that we are surveying give Kirsty and other scientists data of the frequency and intensity of berg impacts with the sea floor, which they then equate to their studies. One study looks at how the bottom dwelling marine life copes with the constant bombardment and how quickly they start to re-colonize.
After a few minutes we arrive at transect two, which I quickly see has almost been obliterated. I look over to Kirsty who already has her clipboard out and starts to record the information. I’m amazed to see plasticine that was in one-inch thick blocks as flat and thin as a sheet of A4 paper, even some of the concrete blocks have been turned into mounds of dust. I check my timer; we have been in the water for 17 minutes and gesture to Kirsty that we only have another 3 minutes before we have to start our ascent.
Kirsty finishes off her recordings and signals to me that she is ready to leave the bottom; I make a mental note that my timer reads 19 minutes. We turn and start to swim back up the slope both of our torches working hard scanning the bottom on the way. The abundance of marine life on the bottom is fantastic with hundreds of brittle stars and varying other types of starfish, bright yellow sea lemons, sea cucumbers, sea squirts and little fish hiding between rocks.
We arrive at six metres where we will make our safety stop. We both turn our torches off - there is now plenty of light penetrating from the surface. We are both staring up at the surface where there are small bergs floating, when suddenly out of the corner of my eye I see something swish past. I swing around to get a better a look and see the outline of a seal swimming away. I quickly turn to Kirsty to see if she has noticed, which she has. I then see the seal turning round and coming back. It’s heading right for us at what seems like a hundred miles an hour. It seems to get bigger and bigger. It has almost taken up my complete line of sight. Swoosh; right at the last moment to goes over the top us. I can feel the water swirling around me in its wake. It’s a fur seal and a big one at that; it must be at least 6 feet in length. I turn to see it coming in again, this time I have my wits about me and gauge my breathing so I’m not expelling bubbles when it’s close. To a seal this could be seen as act of aggression. The seal continues to play around us for a few minutes, leaving me in awe of its speed and manoeuvrability.
Reluctantly I check my timer; we have completed our safety stop. I signal to Kirsty and we both swim up to the surface and the seal disappears out of sight. On breaking surface I immediately feel the wind hitting my face. I signal to the surface team that we are ok and we both exit the water. We all move quickly securing the gear to the sledge and start to head back up to the dive store. Once back inside the warmth hits us like a blanket and we struggle out of our suits, laughing as my hood has frozen and feels more like cardboard than neoprene.
We break down the equipment and give it all a rinse in fresh water, before completing our logs. Then we head upstairs for a much deserved hot drink and to plan our objectives for the next dive.
John Withers - Diving Officer and Deputy Winter Base Commander
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