At 08:45 GMT 30th March (the morning after the despatch of newsletter 2) we reached what we then thought would be our southernmost point 72"27.70'S 16"31.14'W. We parked just off the Antarctic ice shelf to do the first CTD station proper of the A23 section. The view was amazing. Large cliffs of ice rose from the sea and the shelf rose steeply behind that. A number of flat topped icebergs had broken loose from the shelf. The water around the ship was relatively clear, although occasional bands of freshly formed ice drifted by. The area seemed to be devoid of wildlife apart from the Antarctic and Snow Petrels that had followed the ship. The air temperature was about -10C, having dropped by 5C in the hour the ship approached the shelf. As the ship turned northward the air temperature rose in an equally dramatic fashion. This has since been dubbed the "Great temperature anomaly" by "Trevor the Weather".
That day and into the night we occupied a number of CTD stations across the Antarctic slope. After reaching a depth of 4000m, we broke off the section and headed southwest in search of more recently formed bottom water. After ten hours steaming through (mainly) ice we reached a new southernmost point on the cruise at 72"49.64'S 22"54.64'W. Apparently a record southerly position for the ship. Whilst we were taking CTD measurements a number of Weddell seals swam around the ship providing great photo opportunities. The search for more recent bottom water appears to have been unsuccessful. The journey back to the cruise track was particularly exciting for the penguin spotters amongst us (virtually all the scientists). Some of us even thought we saw a whale.
Since rejoining the cruise track we have steamed northwards, stopping for CTD dips every 50km or so. Every day we are enthralled by new sights. On the April fools day there was a spectacular display of the Aurora Australis (Southern Lights). On the 2nd we steamed through newly formed pancake ice for the whole day. During the day of the 3rd we steamed into clear water. On the 5th most of us woke to the ship thuderring (think that's a Dave Special word but it is a good description ! ed.) through older thick sea ice embedded with bits of bergs. It was also the sunniest morning since we left Stanley. The biology (penguins and seals) were out in force. The Emperor penguins always stand tall and regal as the ship passes, whereas the Adelie penguins run around like headless chickens, flapping their wings before diving into the nearest lead (crack in the ice).
We have now moved out of the ice and are close to completing the Weddell Sea part of the section. The air temperature has been below 0 C continually since 02:00 GMT on the 27th March. We hope for a return to positive temperatures tomorrow.
Now Karen is going to add a bit of science to give you a flavour of what we are doing. CTD stations are in full swing every few hours and all going well, even the notorious rosette has been behaving perfectly and giving us 100% firing every time. The data are being plotted and contoured - small geostrophic shears in the Weddell Gyre. Now we are reaching the Scotia Arc and the bottom water is very cold - also high in freons - as we begin to close the station spacing up the slope. It's going to be hard work for everyone getting all the different samples for chemical analysis before the ship arrives on the next station - it's all hands to the deck to help out. With the CTD being sampled in the water bottle annex, it's been quite cosy even for the southernmost stations. Only at the station nearest Antarctica did we have trouble with the water freezing in the Niskins.
The ADCP has been disappointing during passage legs but fine on station. We are planning XBTs between CTD stations across the Weddell-Scotia Confluence and the fronts of the Antarctic Circumpolar Current - all to come in the next week or so. We shall probably be passing within sight of South Georgia when we write the next newsletter.
Best wishes to all readers !