Inter-calibration at the North Pole
By Ursula Schauer |
On September 7, 2015 Polarstern reached the geographic North Pole. Already from some distance we recognized the outline of another ship: the US Coast Guard Cutter Healy.
The officer on duty, Igor Hering, was steering the ship through the dense ice cover while it slowly approached 90° north. The compass needle indicator rotated wildly, as it is supposed to do, and many other displays had a chance to demonstrate whether or not their software were able to handle 90°N. On the bridge there was considerable turmoil, there was chatting and laughter, happy faces, and seemingly thousands of photos being taken.
There were also some unimpressed faces, since some of the crew members have already been at the Pole four times. Polarstern reached the North Pole for the first time in 1991 together with the Swedish ice breaker Oden, then in 2001 accompanied by the Healy, and in 2011 all on its own. With the last visit in 2014 and now our own one, research with Polarstern at the pole is getting to be routine.
The Healy has been working at the pole already for some days. Similar to Polarstern, she has about 60 scientists onboard who conduct a similarly comprehensive oceanographic program. Our own program is tightly linked to that of the Healy; while the Healy is conducting two long transects in the Pacific sector of the Arctic, our own stations capture the Eurasian Arctic. With their investigation of trace elements and isotopes both ships cover the Arctic portion of the international GEOTRACES program (see also: Expedition Summary and Weekly Report 2, and www.geotraces.org). By coordinated planning of the two expeditions taking place in the same year, complimented by Canadian expeditions, a synoptic cover of nearly the entire Arctic Ocean is achieved.
It has only recently become possible to measure the concentration of many substances found in the ocean as new methods for analysis have been developed. Therefore, crossover stations of different labs at the same position in the ocean are invaluable for the determination whether our Arctic-wide observations properly resolve spatial differences or if they just manifest methodological differences between different labs. Organizing such a crossover calibration by sending two ships to a particular location in the central Arctic Ocean is not a simple task. It is even less simple to arrange this crossover in the very same season. To have the crossover station happen at the same day is a planning (and conducting) challenge beyond any reasonable efforts. Therefore, when such a crossover station is conducted at the same day at the North Pole, it is a magical moment for all participants in both expeditions. This will not only last for the rest of the cruise but also holds for the knowledge increase gained through these combined measurements.
Yet even if we are not at the Pole just for symbolic reasons, but because our research programs took us here, we celebrated the occasion. The preparations were running for days: a pole was constructed to hold the printouts of names of and distances to all home towns, flags were ironed and Glühwein was heated. Finally, we went alongside at the same floe which the Healy was at, and everyone, except those standing watch, went on the ice and strolled through the snow. And then of course the visiting between the ships started.
After inquiring cautiously (after all, a coastguard ship is a military platform) it quickly became clear that mutual visits on both ships were highly appreciated. There was nothing holding them back now. The stream of crew and scientific participants walking in both directions were cordially welcomed on the respective other side and with enthusiasm guided through the ship: labs and cabins were visited, bridges and engine rooms were proudly presented, and some scientists met long known or new colleagues and could discuss face to face questions regarding the work.
After a couple of hours everyone returned back home. For the American colleagues it was afternoon; for us on Polarstern it was already early morning so everybody was sinking onto his/her pillow immediately and taken away by dreams of the beautiful day. All, of course except those standing watching and except those who started to conduct the inter-calibration station – happy with the knowledge that they were obtaining an invaluable data set.
