At last, the weather arrives and I can collect data
56° 08.91 S
34° 52.61 W
On Thursday, the weather arrived. The relief was immense – I finally had data to collect! As we put out the buoy to measure all the lovely bubbles that were being generated, the air temperature was -6C, the water temperature was about -2C, we had a 30mph wind and there was horizontal snow. But who cares about all that when there are bubbles to look at?
We took turns at standing out on deck to keep an eye on the tether. Huddled in our massive down jackets and trying to shelter under the gantry, we were put to shame by the astonishing small seabirds swooping around the enormous waves. They stayed about half a metre above the water surface, never touching it and zooming around happily in brutal conditions. I don't think I've ever had so much respect for something so small.
But the wind didn't make everyone happy. When a ship is rolling and pitching, just getting on with everyday life takes a lot more effort. You used to walk down corridors but now the only possible gait is an inelegant waddle. Even then, you still bounce off the walls (and occasionally the ceiling). Soup has a mind of its own, and only the very optimistic fill their tea mugs past halfway. Sometimes a whole deskful of stuff will suddenly arrive in your lap. And sleep can be hard – several times this week I've woken up feeling as though I'd spent the past eight hours in a tumble dryer.
It just goes to show how much we take the stability of gravity for granted. Funniest of all is the circuit training. Three times a week, a group of us toddle or waddle down to the hold, where there are mats and weights and enthusiastic cries of encouragement from Rich the purser. Sit-ups seem delightfully easy for six seconds or so, while the ship is falling and gravity has effectively decreased. Then you pay for it during the following six seconds as the ship rises back up and the increased effective gravity pins you to the floor.
The main task this week has been to investigate the large-scale structure of the ocean below us. We reached our southernmost point at the start of the week and we've been working our way back north along a line, stopping every few hours to take samples. The astonishing thing about this particular sort of sampling is that very simple measurements of just two things – temperature and salinity – are enough to reveal gigantic rivers, waterfalls and lakes hidden within the ocean.
If there was anything sentient in the deep ocean, its main evidence for human existence would be the occasional appearance of strange rings of cylinders dangling down on long lines. It may be unusual for humans to reach the depths of the ocean, but these funny cylinders have been going there regularly for decades. They are called Niskin bottles, and they are always accompanied by a thermometer and a device for measuring salinity. This apparatus is the most fundamental tool in the oceanographer's kit. Welcome to the world of the CTD.
Every oceanographic ship has a CTD rosette. As it's lowered down, it sends back information about conductivity (a measure of salinity), temperature and depth. Once it's close to the ocean floor, usually four or five kilometers down, the scientists on board have a detailed profile of the water below them. On the way back up, they choose when to close the Niskin bottles (previously open at both ends) and so they can bring back samples of water from different depths.
Amazingly, temperature and salinity are enough to track individual water masses flowing around the world's oceans. Moving water masses form an oceanic circulation system and, like the human circulation system, it moves oxygen and nutrients around. Here in Antarctica, the ice and cold mean the surface water becomes cooler, saltier and more dense. It sinks at the edge of the continent and cascades out over the shelf and down towards the deep ocean floor. Then it slowly slithers along the bottom and out into the rest of the world's oceans, taking oxygen and carbon with it. This week, the CTD group has been able to identify this colder water layer sitting on the ocean floor. Their job has been to track where it's got to this year. It's been a bit like a yearly medical, checking this part of the pulse of the planet.
Now the medical is done and we're heading back towards South Georgia. It's warmed up, and it's calm again for the time being. We're going to an exposed area of ocean, so I'm optimistic about finding more bubbles. And we're apparently also quite likely to see whales. What a fabulous combination to look forward to!