Video: Coral AAD trawl
At 88 metres vast coral gardens cover the seafloor.
Part 4 : Climate clues in Antarctic bottom water
We are now in the CASO (Climate of the Antarctic and Southern Ocean) sampling area and must cover 31 stations in six days.
The CTD equipment (conductivity, temperature and depth) 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. The CTD is dropped to depths of around 3,600 metres to sample the cold, dense, Antarctic bottom water that drains from the Mertz Glacier. It takes over an hour for the wire to descend that far at a rate of around a metre a second.
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 and variations in salinity can offer clues to understanding climate, the rising sea level, and the how the ocean functions as a carbon sink.
As we work, we encounter whales and birds and even a curious black iceberg…
Video: Ice
The calm water is building an ice coat. It starts with a thin, greasy looking slick that moves with the swell, gradually thickening as it expels its salt. As the wind disturbs the surface, the cells rub, jostle and blur the edges forming beautiful pancakes. The sea ice can thicken by 20 cm overnight growing both below and above the sea surface. The thin ice grows to be metres thick and eventually becomes the coming winter sea ice, doubling the size of the frozen continent.
Fun in the spa on deck.