1 November 2018

IMAU PhD student David Wichmann

My cruise to the North Atlantic subpolar gyre

In mid-May I got an E-Mail forwarded by my supervisor with the subject “student voor vaartocht” – and even though my Dutch skills are rather limited I immediately knew that this was my big chance to go on a research cruise within my PhD. Coming from theoretical physics, I had only a slight idea about observational oceanography if any, so it was clear that I could benefit a lot from such an experience. Some E-Mails and one and a half months later I stood in Reykjavik at the pier, ready to board the American research vessel Neil Armstrong to discover the subpolar North Atlantic within the OSNAP (Overturning in the Subpolar North Atlantic Program) project.

On board were three research groups from the U.K. (SAMS), US (RSMAS) and the Netherlands (NIOZ) and the crew, together more than 40 people. Thanks to the collaboration of IMAU with NIOZ I could join this one-month long journey as part of the NIOZ team. The main goal of the cruise was the recovery and re-deployment of 19 moorings, as well as taking around 100 CTD (Conductivity, Temperature, Depth) profiles across the Iceland Basin and Irminger Sea. Equipped with all kinds of sensors, the moorings were deployed there two years ago and continuously measured temperature, salinity, current speed and pressure along the water column.

Being prepared for the hardship of ship life – admittedly possibly influenced by Jack London’s “The Sea Wolf” which I was reading on the plane – I was surprised that life on the ship was quite comfortable and, above all, filled with all kinds of meals during the day, most prominently the “cheese-thirty” event at half two pm and the infinite stock of ice cream aboard. If I think back, perhaps only the ship-coffee matched my expectations.

 

During the shifts I was mostly involved in operating the CTD, which measures salinity, pressure and temperature profiles. In the ocean community this job is perhaps considered the most boring, but I was truly excited when I saw my first profile with all the well-known features in it: the mixed layer, the thermocline, and different water masses with their characteristic temperature and salinity signatures. And each time it was a thrilling moment when the water samples came aboard, often from more than 3000m deep.

Recovering and re-deploying moorings along our way, we slowly headed westwards along our planned section just to be soon interrupted by the remnants of tropical storm “Chris”, which were on their way directly towards us. Evading the storm – and with it the last chance to get seasick – we finished the section from the east and even managed to arrive back in Reykjavik one day before schedule. Being part of this cruise was a great opportunity on my route to becoming an oceanographer, and it showed me as a modeler how hard it is to gather real data from the ocean. Although I certainly was more than happy to be back on land after 4 weeks on the ship, I am glad that I got this opportunity within my PhD education.

David Wichmann