Note from Alexander and Martin.

A lot has happened in the last couple of days. One of the more interesting challenges with working in these environments is adapting your regular routines to handle the unique properties of the water column. With the AUV, two of the instruments that are giving us the most trouble are the ADCP and the CTD. The first of these is because of the clarity of the water that doesn’t allow for the instrument to adequately measure water velocities. Many different attempts were made to adequately sample but the best we could do was approximately 2 m away from the vehicle when we should usually get 8-10 m. The other issue that was encountered with the CTD was that ‘supercooled’ water and platelet formation on the instrument would cause problems with the salinity measurements. The former was prevented by pouring a bucket of warm water on the CTD immediately before launch and then the  latter was avoided by cutting up a kitchen sieve and using that as a guard for the intake to the instrument. The other issue that is being encountered is that the controlling fins of the AUV are having problems in the cold – most likely a combination of increased viscosity of the oil that they’re in and mechanical resistance. Not much can be done to avoid this except heating the tail cone of the vehicle with a portable heater until immediately before she’s to go in the water.

However, it isn’t all work around the hole, between times in the water we’ve been putting in the ROV and warding off overly friendly visitors!

With everything relatively debugged, we’re actually gathering data on mixing and eddy movement from underneath the ice tongue. Although it’s relatively difficult to sample in a current that’s moving up to 0.5 m/s vertically and even greater than that horizontal, we’re able to discern repeatable structure in both the salinity and temperature profiles. In addition, we have been working on a way to estimate platelet ice thickness from the sidescan sonar and vehicle altitude data. Still in the process of debugging this, but we think it might be a new way to estimate platelet thickness which is an important factor in basal sea ice growth in regions with supercooled water.

Although Halloween isn’t very big down at the Kiwi base, a few of us did get to celebrate by dressing up like polar explorers and joining the familiarization trip to Shackleton’s Hut up at Cape Royds. This was a beautiful windless day that showed Antarctica, and this little piece of Antarctic exploration history , most wonderfully.

Regards,

Alexander and Martin