We are now out of normal communications satellite range, and are reliant on our Iridium phones for any essential messages (and this blog!). The Antarctic Circle is defined as 66 degrees 33′ S, and we crossed this latitude late evening (around 10pm) on the 31st January – so we are now officially in Antarctic waters!
One of the important tasks before we arrive in our study region is to check that all our equipment is performing as expected. After a two day postponement due to weather (we had quite a bit of swell, with a maximum recorded roll of about 30 degrees to port!), we ran a CTD cast, tested one of our VMPs (Vertical Microstructure Profilers) and released a radiosonde. Throughout the cruise we’ll have special blog posts describing what each of these pieces of equipment do, but today we’ll briefly describe a CTD.
A CTD being deployed from the JCR in the Weddell Sea, January 2012.
CTD stands for Conductivity-Temperature-Depth, and these are the three main measurements that this sensor takes, providing salinity, temperature and depth. The sensors are also able to collect dissolved oxygen and chlorophyll measurements, and these are attached to a ‘rosette’, which consists of 24 10-litre bottles that can be shut at any specified depth to collect water samples. These water samples are then measured for salinity, dissolved oxygen and Helium-Tritium concentrations, and these can be used to verify the readings that the sensors provide. All of these measurements give us vital information about where the water has come from and how these water masses interact.
It is definitely becoming evident we’re travelling further south; we started spotting our first icebergs yesterday, and they’re becoming a much more frequent sight. However, straight after our CTD cast, the visibility reduced dramatically and we’re currently sailing through fog with snowfall! There’s already a shallow covering on the colder surfaces on the ship.
We expect to arrive on the shelf edge of the Amundsen Sea in the early hours of Sunday morning (2nd Feb), and then our science will begin!! CTD measurements will be taken all the way down to the front of the ice shelf, and we’re hoping to spot some seals along the way too. If all goes to plan, we should be arriving in front of Pine Island Glacier next Friday or Saturday!
We’ll try to update this blog as frequently as we can, but it is unlikely we’ll be able to send photos out from the field until our return to normal communications. Until then, we’ll try our best to describe the views! You can also see previous photos from the Antarctic field season and follow our location from our meteorological data here.
Via: Ocean2ice blog