Saturday 29th December

I worked through a CTD shift with Esmee. What an insight into the nature of research it offered; a water sample is much more than a bucket over the side.

The CTD equipment stands as high as your shoulders and holds a 'rosette' of vertical cylinders within a metal frame. Each cylinder can be opened individually at a nominated depth. Data from several electronic devices bolted to the frame indicating salinity and fluorescence, and temperature and depth is assessed during the CTD's descent and the optimum sampling depths identified.

A crew winches the equipment out the side hatch of the CTD room, while nearby in the instrument room the descent is guided down and back 'firing' the cylinders electronically to open and fill as the frame returns.

Details are noted meticulously, recording the time and location of each sample. Then when it's hauled up again people emerge from various labs, gloved up, in waterproofs and gumboots for their share of the freezing cold water.

It's an orderly queue and conversations roll around the rosette in a community of collaboration. A count of the various receptacles shows the range of data being recorded. Mark is measuring CFC's. He needs to minimize risk of air contamination so he's first. He siphons into a giant syringe then whisks his crate of samples back to his container on the helideck for immediate attention. Dr Steve Rintoul who manages this project is next. He steps in next with a flask, records each temperature, and adds chemicals to his sea water recording dissolved oxygen. Melissa is collecting for CO2, Esmee's salts are bottled in brown glass. Finally four small 'nutrients' tubes are filled, each vial coded and marked and sent off to the fridge and freezer up at Beverley in 'Skylab' on the mezzanine deck.

Every CTD cast contributes this information to a data bank gathered over 15 years, revealing the movement and makeup of the Southern Ocean. Measuring the behaviour of its major currents, temperature changes in the water and varying salinity can offer clues to understanding climate, the rising sea level, and the how the ocean functions as a carbon sink.

So how many people do you need to take a water sample?

At least a dozen.

Pics: CTD goes out CTD sampling

Margot Foster is a journalist currently on board the Australian Aurora Australis, an Australian research vessel currently participating in the Census of Antarctic Marine Life (CAML, IPY project 53). She works with the Australian Broadcasting Corporation (ABC).