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We have deployed two moorings today and have one more to do. Many things are harder to do in the Antarctic, and one of them is deploying moorings. We usually stream out the lengths of wire, with instruments and flotation at various depths, behind the ship. The bottom of the mooring, with the big anchor, is deployed last and drags the rest of the mooring down so it sits vertically in the water. In the sea ice, this can be difficult: if a big floe crossed the mooring line, it would break. This particular region of Antarctica poses another challenge: we are almost on top of the south magnetic pole here. The conventional compasses in our oceanographic instruments don’t work (the dip angle of the magnetic field is more than 89 degrees). So to measure current directions with the moorings, we are using a fibre optic gyro, which does not depend on the magnetic field. But we only have one of them (they’re expensive), so we need to deploy and recover it again, to use on the next mooring. The moorings are designed so once we know the orientation of the instrument package on the sea floor, we can determine the ocean currents for the whole duration of the experiment. Finding the relatively small gyro package once it is released and floats up to the surface can be tricky, especially when there is ice around or blowing snow. We’ll try to do this for the second time in a few hours.
REGARDS: Steve, Fred and Penny
Map
A map showing Australia and Antarctica. The map shows the journey of one voyage that has occured in the season, with each route highlighted in a distinct colour.