Into the Weddell Sea

Today, by noon, when the tide shifted once again, we could make good use of this space to ram into the blocking floe at the bow.  With a few well-aimed bouts we finally succeed to push it away, opening our path to thinner sea ice.  This success is owed to Polarstern’s immense power.  No less than 20,000 hp allow accelerating to a speed of 3kn within a ship’s length to again and again push the bow onto the floe, which slowly but surely budges under the ship’s weight. 

12. January 2017, 3 weeks and 6 days at sea

This morning, just after midnight, we finally launched the first Argo float, dropping it rather unpretentiously from the stern into the ship’s wake.  From now on, it shall obtain CTD profiles between 2000 m depth and the sea surface and then transmit the data by satellite.  In between it drifts at 800m depth, sojourning slowly across the Weddell Sea.  Of particular scientific value is the fact, that the float will diligently execute its mission, even once Polarstern has long since returned to Bremerhaven.  Argo floats have a lifetime of up to 4 years!  This will help us to observe the formation of sea ice and cold bottom waters, which primarily occurs in fall and winter and which is highly relevant to the climate system.  Data from an international fleet of 3500 Argo floats, equally distributed across the global ocean, are sent – where possible - in real-time to the Argo data bases, where everyone can download them at anytime.  A still much too rare cooperation between coastal states to foster our understanding and protection of the oceans and the climate system!

13. January 2017, 4 weeks at sea

While the work on deck continues to be dominated by mooring recoveries and deployment, the ALGENOM team continues their lab-work with diatom cultures which had been isolated during the last weeks. Diatoms (Fig. 5) are an important group within the phytoplankton organisms of the Southern Ocean. Our team would like to gain insights into their evolvability, that is, how quickly they can adjust to changing environmental condition, under field conditions using experimental and population genomic methods. We catch our organisms using hand nets, the ice basked (both Fig. 6) and the Niskin bottles attached to the CTD rosette, and pick individual cells or colonies into nutrient enriched seawater fresh under the inverted microscope. Under temperature and artificial light conditions close to what they are used to, these cells start to divide. With time, the single original cell grows into a thick brown soup of diatoms. But until then they need careful attention. We look at the cultures regularly and pick them again if necessary to free them completely of any other organisms growing alongside. Our catches are good: at almost every station, a couple dozens of new cultures join the team. If all goes well, these cultures will be returned to Bremerhaven alive and we can start lab experiments and molecular biological work on them back home.

14. January 2017, 4 weeks and 1 day at sea

The ship’s motions and its vibrations suddenly change in the middle of night.  But we cannot have reached the next station yet.  That one is scheduled for 9 AM, and it is only 4 now.  A call to the bridge elucidates the situation.  We got into a field of icebergs and thick fog reduces the sight to sometimes one, maybe two, ship lengths.  In spite of radar, this calls for reduced speed, we feel our way forward at only 1, maybe 1 ½ knots.  The officer on duty is certain: In the 23 years of his service on Polarstern, he has never experienced such a situation.  He requests all 4 of our machines to be up and running, such that he can command “Full Astern” at any time.  Should an iceberg pop up unexpectedly in front of the bow, the ship could now be brought to a halt within a ships length.  With good visibility, the iceberg parade would be a feast for the eyes, but right now we can only dimly make out the giant colossuses passing by.  With today’s deck work, which was dedicated to the tuning of RAFOS sources, being finished, we join on the working deck for a barbecue instead of the mess room.  Thanks to our galley team, it once again turns into a culinary highlight, as on many expeditions before.

15. January 2017, 4 weeks and 2 days at sea

Exchanging moorings once again.  But they do not let us settle into a routine.  This time the mooring’s transponder does not like to answer to the queries from the ship’s underwater positioning system.  However, a second release, which is integrated into our moorings for redundancy, promptly responds to the acoustic release command and shortly after the floatation elements are sighted at the surface.  A short moment of tension yields to relief.

In good spirits everybody aboard greets home,

Olaf Boebel